51
|
Abstract
Episodic memory capacity requires several processes, including mnemonic discrimination of similar experiences, termed pattern separation, and holistic retrieval of multidimensional experiences given a cue, termed pattern completion. Both computations seem to rely on the hippocampus proper, but they also seem to be instantiated by distinct hippocampal subfields. Thus, we investigated whether individual differences in behavioral expressions of pattern separation and pattern completion were correlated after accounting for general mnemonic ability. Young adult participants learned events comprised of a scene-animal-object triad. In the pattern separation task, we estimated mnemonic discrimination using lure classification for events that contained a similar lure element. In the pattern completion task, we estimated holistic recollection using dependency in retrieval success for different associations from the same event. Although overall accuracies for the two tasks correlated as expected, specific measures of individual variation in holistic retrieval and mnemonic discrimination did not correlate, suggesting that these two processes involve distinguishable properties of episodic memory.
Collapse
Affiliation(s)
- Chi T Ngo
- Department of Psychology, Temple University, Philadelphia, PA, USA.
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Lentzeallee 94, 14195, Berlin, Germany.
| | | | - Ingrid R Olson
- Department of Psychology, Temple University, Philadelphia, PA, USA
| | - Nora S Newcombe
- Department of Psychology, Temple University, Philadelphia, PA, USA
| |
Collapse
|
52
|
Zhang X, Jonas P. Integration of spatial and non-spatial information by heterogeneous dentate gyrus granule cells. JOURNAL OF LIFE SCIENCES (WESTLAKE VILLAGE, CALIF.) 2020; 2:19-24. [PMID: 33409506 PMCID: PMC7116553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The hippocampus is the key site for learning and memory and for processing of spatial information in the brain. It is divided into three main subregions: the dentate gyrus (DG), the CA3 area, and the CA1 region, which are linearly interconnected to form a so-called trisynaptic circuit. Thus, the DG sits in a strategic position to gate the flow of information from the neocortex into the hippocampal network. The granule cells (GCs), the main cell type in the DG, receive 'where' and 'what' information from the medial and lateral entorhinal cortex, respectively. How they process this mixed information remains enigmatic. By characterizing the spatial information encoded by the excitatory postsynaptic potentials (EPSPs) in GCs, we demonstrated that the majority of GCs received spatially tuned synaptic input. However, only a minority of GCs successfully converted spatially tuned input to spatially tuned output. Furthermore, we found that mature GCs were highly heterogeneous in terms of their dendritic morphology and intrinsic excitability, which contributes to the sparse and heterogeneous firing of GCs. Finally, we discuss the possible origin of this neural heterogeneity and its potential role in enlarging the computational power of the DG, facilitating pattern separation in this network.
Collapse
Affiliation(s)
- Xiaomin Zhang
- IST Austria (Institute of Science and Technology Austria), Cellular Neuroscience, Am Campus 1 A-3400 Klosterneuburg, Austria
| | - Peter Jonas
- IST Austria (Institute of Science and Technology Austria), Cellular Neuroscience, Am Campus 1 A-3400 Klosterneuburg, Austria
| |
Collapse
|
53
|
Auth JM, Nachstedt T, Tetzlaff C. The Interplay of Synaptic Plasticity and Scaling Enables Self-Organized Formation and Allocation of Multiple Memory Representations. Front Neural Circuits 2020; 14:541728. [PMID: 33117130 PMCID: PMC7575689 DOI: 10.3389/fncir.2020.541728] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 08/19/2020] [Indexed: 12/23/2022] Open
Abstract
It is commonly assumed that memories about experienced stimuli are represented by groups of highly interconnected neurons called cell assemblies. This requires allocating and storing information in the neural circuitry, which happens through synaptic weight adaptations at different types of synapses. In general, memory allocation is associated with synaptic changes at feed-forward synapses while memory storage is linked with adaptation of recurrent connections. It remains, however, largely unknown how memory allocation and storage can be achieved and the adaption of the different synapses involved be coordinated to allow for a faithful representation of multiple memories without disruptive interference between them. In this theoretical study, by using network simulations and phase space analyses, we show that the interplay between long-term synaptic plasticity and homeostatic synaptic scaling organizes simultaneously the adaptations of feed-forward and recurrent synapses such that a new stimulus forms a new memory and where different stimuli are assigned to distinct cell assemblies. The resulting dynamics can reproduce experimental in-vivo data, focusing on how diverse factors, such as neuronal excitability and network connectivity, influence memory formation. Thus, the here presented model suggests that a few fundamental synaptic mechanisms may suffice to implement memory allocation and storage in neural circuitry.
Collapse
Affiliation(s)
- Johannes Maria Auth
- Department of Computational Neuroscience, Third Institute of Physics, Georg-August-Universität, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
| | - Timo Nachstedt
- Department of Computational Neuroscience, Third Institute of Physics, Georg-August-Universität, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
| | - Christian Tetzlaff
- Department of Computational Neuroscience, Third Institute of Physics, Georg-August-Universität, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
| |
Collapse
|
54
|
Jurkowski MP, Bettio L, K. Woo E, Patten A, Yau SY, Gil-Mohapel J. Beyond the Hippocampus and the SVZ: Adult Neurogenesis Throughout the Brain. Front Cell Neurosci 2020; 14:576444. [PMID: 33132848 PMCID: PMC7550688 DOI: 10.3389/fncel.2020.576444] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 08/19/2020] [Indexed: 12/31/2022] Open
Abstract
Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.
Collapse
Affiliation(s)
- Michal P. Jurkowski
- Island Medical Program, University of British Columbia, Vancouver, BC, Canada
| | - Luis Bettio
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
| | - Emma K. Woo
- Island Medical Program, University of British Columbia, Vancouver, BC, Canada
| | - Anna Patten
- Centre for Interprofessional Clinical Simulation Learning (CICSL), Royal Jubilee Hospital, Victoria, BC, Canada
| | - Suk-Yu Yau
- Department of Rehabilitation Sciences, Hong Kong Polytechnic University, Hung Hom, Hong Kong
| | - Joana Gil-Mohapel
- Island Medical Program, University of British Columbia, Vancouver, BC, Canada
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
| |
Collapse
|
55
|
Dohm-Hansen S, Johansson M. Mnemonic discrimination of object and context is differentially associated with mental health. Neurobiol Learn Mem 2020; 173:107268. [DOI: 10.1016/j.nlm.2020.107268] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/27/2020] [Accepted: 06/08/2020] [Indexed: 11/29/2022]
|
56
|
Statistical prediction of the future impairs episodic encoding of the present. Proc Natl Acad Sci U S A 2020; 117:22760-22770. [PMID: 32859755 DOI: 10.1073/pnas.2013291117] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Memory is typically thought of as enabling reminiscence about past experiences. However, memory also informs and guides processing of future experiences. These two functions of memory are often at odds: Remembering specific experiences from the past requires storing idiosyncratic properties that define particular moments in space and time, but by definition such properties will not be shared with similar situations in the future and thus may not be applicable to future situations. We discovered that, when faced with this conflict, the brain prioritizes prediction over encoding. Behavioral tests of recognition and source recall showed that items allowing for prediction of what will appear next based on learned regularities were less likely to be encoded into memory. Brain imaging revealed that the hippocampus was responsible for this interference between statistical learning and episodic memory. The more that the hippocampus predicted the category of an upcoming item, the worse the current item was encoded. This competition may serve an adaptive purpose, focusing encoding on experiences for which we do not yet have a predictive model.
Collapse
|
57
|
Episodic memory contributions to autobiographical memory and open-ended problem-solving specificity in younger and older adults. Mem Cognit 2020; 47:1592-1605. [PMID: 31215008 DOI: 10.3758/s13421-019-00953-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Research indicates that episodic memory processes are required to access specific autobiographical events and the details encompassed by a single event for several functions, including remembering and personal problem solving. Since healthy cognitive aging is associated with episodic memory decline, we hypothesized that older adults would be impaired at producing specific autobiographical events and details in service of these two functions. To test this hypothesis, younger and older adults completed two tasks (generation and elaboration) across two experiments (autobiographical memory and problem solving). The generation task required participants to produce multiple specific event memories or solutions to cues within a 90-s time period. The elaboration task required participants to select a single memory or solution to describe in detail. We quantified the number of specific and non-specific responses provided during the generation task and scored the descriptions from the elaboration task for the number of episodic (internal) and non-episodic (external) details. Across experiment, older adults produced fewer specific responses (generation task) and fewer internal details (elaboration task) than younger adults. In addition, older adults generated more non-specific responses and external details than younger adults for the memory but not the problem-solving experiment. A correlational analysis showed that the number of specific responses (generation) and internal details (elaboration) correlated for the memory but not for the problem-solving experiment. These results show that age-related episodic memory decline impairs access to specific autobiographical events and detail information when remembering and problem solving, but that additional cognitive factors impact how these age declines present when solving problems.
Collapse
|
58
|
Zotow E, Bisby JA, Burgess N. Behavioral evidence for pattern separation in human episodic memory. ACTA ACUST UNITED AC 2020; 27:301-309. [PMID: 32669385 PMCID: PMC7365015 DOI: 10.1101/lm.051821.120] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 06/03/2020] [Indexed: 01/02/2023]
Abstract
An essential feature of episodic memory is the ability to recall the multiple elements relating to one event from the multitude of elements relating to other, potentially similar events. Hippocampal pattern separation is thought to play a fundamental role in this process, by orthogonalizing the representations of overlapping events during encoding, to reduce interference between them during the process of pattern completion by which one or other is recalled. We introduce a new paradigm to test the hypothesis that similar memories, but not unrelated memories, are actively separated at encoding. Participants memorized events which were either unique or shared a common element with another event (paired “overlapping” events). We used a measure of dependency, originally devised to measure pattern completion, to quantify how much the probability of successfully retrieving associations from one event depends on successful retrieval of associations from the same event, an unrelated event or the overlapping event. In two experiments, we saw that within event retrievals were highly dependent, indicating pattern completion; retrievals from unrelated events were independent; and retrievals from overlapping events were antidependent (i.e., less than independent), indicating pattern separation. This suggests that representations of similar (overlapping) memories are actively separated, resulting in lowered dependency of retrieval performance between them, as would be predicted by the pattern separation account.
Collapse
Affiliation(s)
- Ewa Zotow
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, United Kingdom
| | - James A Bisby
- Division of Psychiatry, University College London, London W1T 7BN, United Kingdom
| | - Neil Burgess
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, United Kingdom.,Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| |
Collapse
|
59
|
Nitschke JP, Giorgio LM, Zaborowska O, Sheldon S. Acute psychosocial stress during retrieval impairs pattern separation processes on an episodic memory task. Stress 2020; 23:437-443. [PMID: 32008411 DOI: 10.1080/10253890.2020.1724946] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Numerous studies have shown that the presence of psychosocial stress impairs the ability to retrieve episodic memories, which raise questions about the specific cognitive processes that underlie this impairment. Here, we tested the hypothesis that stress targets retrieval processes needed to reliability discriminate previously learned from new information within episodic memory, pattern separation processing by measuring the effects of retrieval-induced stress on a modified version of the Mnemonic Similarity Task. In a two-part between-subjects design, all participants studied a series of object images in an initial testing session. In a second session, held 24 h later, half of the participants completed a stress induction task (stress group) and half performed a similarly structured but non-stressful task (control group) and all were then given a recognition memory test for the previously studied images which included new images similar to those studied (lures), and images that were completely novel (foils). Both groups performed equally well in terms of overall recognition memory, but the stress group was significantly impaired in discriminating new and similar (lure) items from studied items. This pattern of results suggests that stress specifically targets pattern separation processing when retrieving information from episodic memory. We discuss the implications of this effect, specifically how stress at retrieval reduces the ability to discriminate new from learned information.
Collapse
Affiliation(s)
| | - Lisa-Marie Giorgio
- Department of Psychology, McGill University, Montreal, Canada
- Department of Education and Counselling Psychology, McGill University, Montreal, Canada
| | - Oliwia Zaborowska
- Department of Psychology, McGill University, Montreal, Canada
- SWPS University of Social Sciences and Humanities, Warsaw, Poland
| | - Signy Sheldon
- Department of Psychology, McGill University, Montreal, Canada
| |
Collapse
|
60
|
Nyberg L, Grande X, Andersson M, Berron D, Lundquist A, Stiernstedt M, Fjell A, Walhovd K, Orädd G. Forecasting memory function in aging: pattern-completion ability and hippocampal activity relate to visuospatial functioning over 25 years. Neurobiol Aging 2020; 94:217-226. [PMID: 32650185 DOI: 10.1016/j.neurobiolaging.2020.06.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 06/01/2020] [Accepted: 06/05/2020] [Indexed: 11/18/2022]
Abstract
Heterogeneity in episodic memory functioning in aging was assessed with a pattern-completion functional magnetic resonance imaging task that required reactivation of well-consolidated face-name memory traces from fragmented (partial) or morphed (noisy) face cues. About half of the examined individuals (N = 101) showed impaired (chance) performance on fragmented faces despite intact performance on complete and morphed faces, and they did not show a pattern-completion response in hippocampus or the examined subfields (CA1, CA23, DGCA4). This apparent pattern-completion deficit could not be explained by differential hippocampal atrophy. Instead, the impaired group displayed lower cortical volumes, accelerated reduction in mini-mental state examination scores, and lower general cognitive function as defined by longitudinal measures of visuospatial functioning and speed-of-processing. In the full sample, inter-individual differences in visuospatial functioning predicted performance on fragmented faces and hippocampal CA23 subfield activity over 25 years. These findings suggest that visuospatial functioning in middle age can forecast pattern-completion deficits in aging.
Collapse
Affiliation(s)
- Lars Nyberg
- Department of Radiation Sciences, Umeå University, Umeå, Sweden; Department of Integrative Medical Biology, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden; UiO Center for Lifespan Changes in Brain and Cognition, Department of Psychology, University of Oslo, Oslo, Norway.
| | - Xenia Grande
- German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany; Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Micael Andersson
- Department of Integrative Medical Biology, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| | - David Berron
- German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany; Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke University Magdeburg, Magdeburg, Germany; Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Lund University, Lund, Sweden
| | - Anders Lundquist
- Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden; Department of Statistics, USBE Umeå University, Umeå, Sweden
| | - Mikael Stiernstedt
- Department of Integrative Medical Biology, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| | - Anders Fjell
- UiO Center for Lifespan Changes in Brain and Cognition, Department of Psychology, University of Oslo, Oslo, Norway
| | - Kristine Walhovd
- UiO Center for Lifespan Changes in Brain and Cognition, Department of Psychology, University of Oslo, Oslo, Norway
| | - Greger Orädd
- Department of Radiation Sciences, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| |
Collapse
|
61
|
Parizkova M, Lerch O, Andel R, Kalinova J, Markova H, Vyhnalek M, Hort J, Laczó J. Spatial Pattern Separation in Early Alzheimer's Disease. J Alzheimers Dis 2020; 76:121-138. [PMID: 32444544 DOI: 10.3233/jad-200093] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND The hippocampus, entorhinal cortex, and basal forebrain are among the first brain structures affected by Alzheimer's disease (AD). They play an essential role in spatial pattern separation, a process critical for accurate encoding of similar spatial information. OBJECTIVE Our aim was to examine spatial pattern separation and its association with volumetric changes of the hippocampus, entorhinal cortex, and basal forebrain nuclei projecting to the hippocampus (the medial septal nuclei and vertical limb of the diagonal band of Broca - Ch1-2 nuclei) in the biomarker-defined early clinical stages of AD. METHODS A total of 98 older adults were recruited from the Czech Brain Aging Study cohort. The participants with amnestic mild cognitive impairment (aMCI) due to AD (n = 44), mild AD dementia (n = 31), and cognitively normal older adults (CN; n = 23) underwent spatial pattern separation testing, comprehensive cognitive assessment, and MRI brain volumetry. RESULTS Spatial pattern separation accuracy was lower in the early clinical stages of AD compared to the CN group (p < 0.001) and decreased with disease severity (CN > aMCI due to AD > AD dementia). Controlling for general memory and cognitive performance, demographic characteristics and psychological factors did not change the results. Hippocampal and Ch1-2 volumes were directly associated with spatial pattern separation performance while the entorhinal cortex operated on pattern separation indirectly through the hippocampus. CONCLUSION Smaller volumes of the hippocampus, entorhinal cortex, and basal forebrain Ch1-2 nuclei are linked to spatial pattern separation impairment in biomarker-defined early clinical AD and may contribute to AD-related spatial memory deficits.
Collapse
Affiliation(s)
- Martina Parizkova
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Ondrej Lerch
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Ross Andel
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic.,School of Aging Studies, University of South Florida, Tampa, FL, USA
| | - Jana Kalinova
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic
| | - Hana Markova
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Martin Vyhnalek
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Jakub Hort
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Jan Laczó
- Memory Clinic, Department of Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic
| |
Collapse
|
62
|
Riphagen JM, Schmiedek L, Gronenschild EHBM, Yassa MA, Priovoulos N, Sack AT, Verhey FRJ, Jacobs HIL. Associations between pattern separation and hippocampal subfield structure and function vary along the lifespan: A 7 T imaging study. Sci Rep 2020; 10:7572. [PMID: 32371923 PMCID: PMC7200747 DOI: 10.1038/s41598-020-64595-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 04/20/2020] [Indexed: 12/04/2022] Open
Abstract
Pattern separation (PS) describes the process by which the brain discriminates similar stimuli from previously encoded stimuli. This fundamental process requires the intact processing by specific subfields in the hippocampus and can be examined using mnemonic discrimination tasks. Previous studies reported different patterns for younger and older individuals between mnemonic discrimination performance and hippocampal subfield activation. Here, we investigated the relationship between the lure discrimination index (LDI) and hippocampal subfield volume and activity across the adult lifespan (20-70 years old). Using ultra-high field functional and structural magnetic resonance imaging at 7 T, we found that lower DG volume and higher CA3 activation was associated with worse LDI performance in individuals (>60 years), suggesting that this higher activation may be an indication of aberrant neurodegenerative-related processes. In fact, higher activation in the CA1 and DG was associated with lower volumes in these subfields. For individuals around 40-50 years old, we observed that greater left and right DG volume, and greater activity in the CA3 was associated with lower LDI performance. Taken together, these results suggest that the relationship between memory and hippocampal subfield structure or function varies nonlinearly and possibly reciprocally with age, with midlife being a critically vulnerable period in life.
Collapse
Affiliation(s)
- Joost M Riphagen
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands.
| | - Lisa Schmiedek
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands
| | - Ed H B M Gronenschild
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands
| | - Michael A Yassa
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA, USA
| | - Nikos Priovoulos
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands
| | - Alexander T Sack
- Faculty of Psychology and Neuroscience, Department of Cognitive Neuroscience, Maastricht University, PO BOX 616, 6200, MD, Maastricht, The Netherlands
| | - Frans R J Verhey
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands
| | - Heidi I L Jacobs
- Faculty of Health, Medicine and Life Sciences, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, The Netherlands
- Faculty of Psychology and Neuroscience, Department of Cognitive Neuroscience, Maastricht University, PO BOX 616, 6200, MD, Maastricht, The Netherlands
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| |
Collapse
|
63
|
Abstract
In the present study we investigated the long-standing question whether and why emotionally arousing memories are more distinct as compared to neutral experiences. We assumed that memory benefits from the distinctiveness of emotional information, and that emotions affect encoding by reducing interference among overlapping memory representations. Since pattern separation is the process which minimizes interference between memory representations with similar features, we examined the behavioral manifestation of putative neural mechanisms enabling pattern separation (i.e. mnemonic discrimination) for emotionally arousing materials using the Mnemonic Similarity Task with negative, positive, and neutral images as stimuli. Immediately after incidental encoding, subjects were presented with stimuli they had seen at encoding and also with new items. Crucially, participants were also presented with lure images that were visually similar to ones they had seen before. Response options were old, new, and similar. Our results showed that individuals were better in discriminating between similar, emotionally arousing memories, when compared to the neutral stimuli. Moreover, this so-called lure discrimination performance was better for the negative images, than it was for the positive stimuli. Finally, we showed that the high arousing negative stimuli were better separated than the low arousing negative stimuli, and a similar pattern of results was found for the positive items. Altogether, these findings suggest that lure discrimination is modulated by arousal and not by valence. We argue that noradrenergic activity might facilitate interference resolution among memory representations with similar features, and that superior pattern separation might play a key role in memory enhancement for emotional experiences.
Collapse
|
64
|
Josselyn SA, Tonegawa S. Memory engrams: Recalling the past and imagining the future. Science 2020; 367:367/6473/eaaw4325. [PMID: 31896692 DOI: 10.1126/science.aaw4325] [Citation(s) in RCA: 446] [Impact Index Per Article: 111.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In 1904, Richard Semon introduced the term "engram" to describe the neural substrate for storing memories. An experience, Semon proposed, activates a subset of cells that undergo off-line, persistent chemical and/or physical changes to become an engram. Subsequent reactivation of this engram induces memory retrieval. Although Semon's contributions were largely ignored in his lifetime, new technologies that allow researchers to image and manipulate the brain at the level of individual neurons has reinvigorated engram research. We review recent progress in studying engrams, including an evaluation of evidence for the existence of engrams, the importance of intrinsic excitability and synaptic plasticity in engrams, and the lifetime of an engram. Together, these findings are beginning to define an engram as the basic unit of memory.
Collapse
Affiliation(s)
- Sheena A Josselyn
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada. .,Department of Psychology, University of Toronto, Toronto, Ontario M5S 3G3, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5G 1X8, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Brain, Mind & Consciousness Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1M1, Canada
| | - Susumu Tonegawa
- RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. .,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| |
Collapse
|
65
|
Wynn JS, Ryan JD, Buchsbaum BR. Eye movements support behavioral pattern completion. Proc Natl Acad Sci U S A 2020; 117:6246-6254. [PMID: 32123109 PMCID: PMC7084073 DOI: 10.1073/pnas.1917586117] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The ability to recall a detailed event from a simple reminder is supported by pattern completion, a cognitive operation performed by the hippocampus wherein existing mnemonic representations are retrieved from incomplete input. In behavioral studies, pattern completion is often inferred through the false endorsement of lure (i.e., similar) items as old. However, evidence that such a response is due to the specific retrieval of a similar, previously encoded item is severely lacking. We used eye movement (EM) monitoring during a partial-cue recognition memory task to index reinstatement of lure images behaviorally via the recapitulation of encoding-related EMs or gaze reinstatement. Participants reinstated encoding-related EMs following degraded retrieval cues and this reinstatement was negatively correlated with accuracy for lure images, suggesting that retrieval of existing representations (i.e., pattern completion) underlies lure false alarms. Our findings provide evidence linking gaze reinstatement and pattern completion and advance a functional role for EMs in memory retrieval.
Collapse
Affiliation(s)
- Jordana S Wynn
- Department of Psychology, University of Toronto, Toronto, ON M55 3G3, Canada;
- Rotman Research Institute, Baycrest Hospital, Toronto, ON M6A 2E1, Canada
| | - Jennifer D Ryan
- Department of Psychology, University of Toronto, Toronto, ON M55 3G3, Canada
- Rotman Research Institute, Baycrest Hospital, Toronto, ON M6A 2E1, Canada
| | - Bradley R Buchsbaum
- Department of Psychology, University of Toronto, Toronto, ON M55 3G3, Canada
- Rotman Research Institute, Baycrest Hospital, Toronto, ON M6A 2E1, Canada
| |
Collapse
|
66
|
Abstract
Stimulus selection is a critical part of experimental designs in the cognitive sciences. Quantifying and controlling item similarity using a unified scale provides researchers with the tools to eliminate item-dependent effects and improve reproducibility. Here we present a novel Similar Object and Lure Image Database (SOLID) that includes 201 categories of grayscale objects, with approximately 17 exemplars per set. Unlike existing databases, SOLID offers both a large number of stimuli and a considerable range of similarity levels. A common scale of dissimilarity was obtained by using the spatial-arrangement method (Exps. 1a and 1b) as well as a pairwise rating procedure to standardize the distances (Exp. 2). These dissimilarity distances were then validated in a recognition memory task, showing better performance and decreased response times as dissimilarity increased. These methods were used to produce a large stimulus database (3,498 images) with a wide range of comparable similarities, which will be useful for improving experimental control in fields such as memory, perception, and attention. Enabling this degree of control over similarity is critical for high-level studies of memory and cognition, and combining this strength with the option to use it across many trials will allow research questions to be addressed using neuroimaging techniques.
Collapse
Affiliation(s)
- Darya Frank
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, University of Manchester, Manchester, UK
| | - Oliver Gray
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, University of Manchester, Manchester, UK
| | - Daniela Montaldi
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, University of Manchester, Manchester, UK.
| |
Collapse
|
67
|
Szőllősi Á, Bencze D, Racsmány M. Behavioural pattern separation is strongly associated with familiarity-based decisions. Memory 2020; 28:337-347. [PMID: 31955670 DOI: 10.1080/09658211.2020.1714055] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Pattern separation is the process that minimises interference between memory representations with similar features and is suggested to be associated with hippocampus-related recollection. We tested this hypothesis using the incidental Mnemonic Similarity Task with old (target), similar (lure), and new (foil) items presented on a recognition test, which is widely used for detecting individual differences in behavioural pattern separation performance. In Experiment 1, participants made old/similar/new decisions and rated decision confidence on a scale ranging from "not at all sure" to "very sure". In Experiment 2, participants made recognition confidence judgments on a scale ranging between "sure it was new" and "sure it was old". In Experiment 3, subjects gave old/similar/new decisions and made a secondary Remember/Know/Guess judgment. In Experiment 1, confidence ratings were higher for targets compared to lures when we analysed correct responses (old for targets and similar for lures). Additionally, we found a symmetrical ROC curve and a linear zROC curve for target-lure discrimination in Experiment 2. Finally, we found a bias toward Know responses when we analysed behavioural pattern separation performance (i.e., the rate of similar responses given to the lures). These findings suggest that familiarity, rather than recollection, contributes to behavioural pattern separation performance.
Collapse
Affiliation(s)
- Ágnes Szőllősi
- Department of Cognitive Science, Budapest University of Technology and Economics, Budapest, Hungary.,Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Dorottya Bencze
- Department of Cognitive Science, Budapest University of Technology and Economics, Budapest, Hungary.,Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Mihály Racsmány
- Department of Cognitive Science, Budapest University of Technology and Economics, Budapest, Hungary.,Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| |
Collapse
|
68
|
Todd RM, Miskovic V, Chikazoe J, Anderson AK. Emotional Objectivity: Neural Representations of Emotions and Their Interaction with Cognition. Annu Rev Psychol 2020; 71:25-48. [DOI: 10.1146/annurev-psych-010419-051044] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recent advances in our understanding of information states in the human brain have opened a new window into the brain's representation of emotion. While emotion was once thought to constitute a separate domain from cognition, current evidence suggests that all events are filtered through the lens of whether they are good or bad for us. Focusing on new methods of decoding information states from brain activation, we review growing evidence that emotion is represented at multiple levels of our sensory systems and infuses perception, attention, learning, and memory. We provide evidence that the primary function of emotional representations is to produce unified emotion, perception, and thought (e.g., “That is a good thing”) rather than discrete and isolated psychological events (e.g., “That is a thing. I feel good”). The emergent view suggests ways in which emotion operates as a fundamental feature of cognition, by design ensuring that emotional outcomes are the central object of perception, thought, and action.
Collapse
Affiliation(s)
- Rebecca M. Todd
- Department of Psychology, Centre for Brain Health, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Vladimir Miskovic
- Department of Psychology, State University of New York at Binghamton, Binghamton, New York 13902, USA
| | - Junichi Chikazoe
- Section of Brain Function Information, Supportive Center for Brain Research, National Institute for Physiological Sciences, Aichi 4448585, Japan
| | - Adam K. Anderson
- Department of Human Development, Human Neuroscience Institute, Cornell University, Ithaca, New York 14853, USA
| |
Collapse
|
69
|
Dos Santos Corrêa M, Vaz BDS, Grisanti GDV, de Paiva JPQ, Tiba PA, Fornari RV. Relationship between footshock intensity, post-training corticosterone release and contextual fear memory specificity over time. Psychoneuroendocrinology 2019; 110:104447. [PMID: 31561085 DOI: 10.1016/j.psyneuen.2019.104447] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 08/09/2019] [Accepted: 09/13/2019] [Indexed: 12/23/2022]
Abstract
Overgeneralized fear has long been implicated in generalized anxiety and post-traumatic stress disorder, however, time-dependent mechanisms underlying memory retrieval are still not completely understood. Previous studies have revealed that stronger fear conditioning training protocols are associated with both increased post-training corticosterone (CORT) levels and fear responses at later retrieval tests. Here we used contextual fear conditioning (CFC) to investigate the relationship between post-training CORT levels and memory specificity in different retrieval timepoints. Wistar rats were exposed to CFC training with increasing footshock intensities (0.3, 0.6 or 1.0mA) and had their blood collected 30 min afterwards to measure post-training plasma CORT. After 2, 14 or 28 days, rats were tested for memory specificity either in the training or in the novel context. Regression analysis was used to verify linear and non-linear interactions between CORT levels and freezing. Higher footshock intensities increased post-training CORT levels and freezing times during tests in all timepoints. Moreover, stronger trainings elicited faster memory generalization, which was associated with higher CORT levels during memory consolidation. The 0.3mA training maintained memory specificity up to 28 days. Additionally, linear regressions suggest that the shift from specific to generalized memories is underway at 14 days after training. These results are consistent with the hypotheses that stronger training protocols elicit a faster generalization rate, and that this process is associated with increased post-training CORT release.
Collapse
Affiliation(s)
- Moisés Dos Santos Corrêa
- Centro de Matemática, Computação e Cognição (CMCC), Universidade Federal do ABC (UFABC), São Bernardo do Campo, SP, Brazil
| | - Barbara Dos Santos Vaz
- Centro de Matemática, Computação e Cognição (CMCC), Universidade Federal do ABC (UFABC), São Bernardo do Campo, SP, Brazil
| | - Gabriel David Vieira Grisanti
- Centro de Matemática, Computação e Cognição (CMCC), Universidade Federal do ABC (UFABC), São Bernardo do Campo, SP, Brazil
| | | | - Paula Ayako Tiba
- Centro de Matemática, Computação e Cognição (CMCC), Universidade Federal do ABC (UFABC), São Bernardo do Campo, SP, Brazil
| | - Raquel Vecchio Fornari
- Centro de Matemática, Computação e Cognição (CMCC), Universidade Federal do ABC (UFABC), São Bernardo do Campo, SP, Brazil.
| |
Collapse
|
70
|
Méndez-Couz M, Becker JM, Manahan-Vaughan D. Functional Compartmentalization of the Contribution of Hippocampal Subfields to Context-Dependent Extinction Learning. Front Behav Neurosci 2019; 13:256. [PMID: 31798429 PMCID: PMC6868086 DOI: 10.3389/fnbeh.2019.00256] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 10/28/2019] [Indexed: 12/15/2022] Open
Abstract
During extinction learning (EL), an individual learns that a previously learned behavior no longer fulfills its original purpose, or is no longer relevant. Recent studies have contradicted earlier theories that EL comprises forgetting, or the inhibition of the previously learned behavior, and indicate that EL comprises new associative learning. This suggests that the hippocampus is involved in this process. Empirical evidence is lacking however. Here, we used fluorescence in situ hybridization of somatic immediate early gene (IEG) expression to scrutinize if the hippocampus processes EL. Rodents engaged in context-dependent EL and were also tested for renewal of (the original behavioral response to) a spatial appetitive task in a T-maze. Whereas distal and proximal CA1 subfields processed both EL and renewal, effects in the proximal CA1 were more robust consistent with a role of this subfield in processing context. The lower blade of the dentate gyrus (DG) and the proximal CA3 subfields were particularly involved in renewal. Responses in the distal and proximal CA3 subfields suggest that this hippocampal subregion may also contribute to the evaluation of the reward outcome. Taken together, our findings provide novel and direct evidence for the involvement of distinct hippocampal subfields in context-dependent EL and renewal.
Collapse
Affiliation(s)
- Marta Méndez-Couz
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
| | - Jana M Becker
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
| | | |
Collapse
|
71
|
Griffiths BJ, Fuentemilla L. Event conjunction: How the hippocampus integrates episodic memories across event boundaries. Hippocampus 2019; 30:162-171. [PMID: 31566860 DOI: 10.1002/hipo.23161] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 08/16/2019] [Accepted: 08/19/2019] [Indexed: 11/07/2022]
Abstract
Our lives are a continuous stream of experience. Our episodic memories on the other hand have a definitive beginning, middle, and end. Theories of event segmentation suggest that salient changes in our environment produce event boundaries which partition the past from the present and, as a result, produce discretized memories. However, event boundaries cannot completely discretize two memories; any shared conceptual link will lead to the rapid integration of these memories. Here, we present a new framework inspired by electrophysiological research that resolves this apparent contradiction. At its heart, the framework proposes that hippocampal theta-gamma coupling maintains a highly abstract model of an ongoing event and serves to encode this model as an episodic memory. When a second but related event begins, this theta-gamma model is rapidly reconstructed within the hippocampus where new details of the second event can be appended to the existing event model. The event conjunction framework is the first electrophysiological explanation of how event memories can be formed at, and integrated across, event boundaries.
Collapse
Affiliation(s)
| | - Lluís Fuentemilla
- Institute of Neurosciences, University of Barcelona, Barcelona, Spain
| |
Collapse
|
72
|
Nyberg L, Andersson M, Lundquist A, Salami A, Wåhlin A. Frontal Contribution to Hippocampal Hyperactivity During Memory Encoding in Aging. Front Mol Neurosci 2019; 12:229. [PMID: 31680849 PMCID: PMC6798051 DOI: 10.3389/fnmol.2019.00229] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 09/09/2019] [Indexed: 01/03/2023] Open
Abstract
Hippocampal hypo- as well as hyper-activation have been reported during memory encoding in older individuals. Prefrontal cortex (PFC) provides top-down state signals to the hippocampus that bias its computation during memory encoding and retrieval, and disturbed top-down signals could contribute to hippocampal hyper-activation. Here, we used >500 cross-sectional and longitudinal observations from a face-name encoding-retrieval fMRI task to examine hippocampal hypo- and hyper-activation in aging. Age-related anterior hippocampal hypo-activation was observed during memory encoding. Next, older individuals who longitudinally dropped-out were compared with those who remained in the study. Older dropouts had lower memory performance and higher dementia risk, and hyper-activated right anterior and posterior hippocampus during memory encoding. During encoding, the dropouts also activated right prefrontal regions that instead were active during retrieval in younger and older remainers. Moreover, the dropouts showed altered frontal-hippocampal functional connectivity, notably elevated right PFC to anterior hippocampus (aHC) connectivity during encoding. In the context of a general pattern of age-related anterior hippocampal hypo-activation during encoding, these findings support a top-down contribution to paradoxically high anterior hippocampal activity in older dropouts who were at elevated risk of pathology.
Collapse
Affiliation(s)
- Lars Nyberg
- Department of Radiation Sciences, Umeå University, Umeå, Sweden.,Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.,Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| | - Micael Andersson
- Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.,Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| | - Anders Lundquist
- Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden.,Department of Statistics, School of Business, Economics and Statistics, USBE Umeå University, Umeå, Sweden
| | - Alireza Salami
- Department of Radiation Sciences, Umeå University, Umeå, Sweden.,Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.,Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden.,Aging Research Center, Karolinska Institutet and Stockholm University, Solna, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden
| | - Anders Wåhlin
- Department of Radiation Sciences, Umeå University, Umeå, Sweden.,Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden
| |
Collapse
|
73
|
Ngo CT, Lin Y, Newcombe NS, Olson IR. Building up and wearing down episodic memory: Mnemonic discrimination and relational binding. J Exp Psychol Gen 2019; 148:1463-1479. [PMID: 30896199 PMCID: PMC6715497 DOI: 10.1037/xge0000583] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Our capacity to form and retrieve episodic memories improves over childhood but declines in old age. Understanding these changes requires decomposing episodic memory into its components. Two such components are (a) mnemonic discrimination of similar people, objects, and contexts, and (b) relational binding of these elements. We designed novel memory tasks to assess these component processes using animations that are appropriate across the life span (ages 4-80 in our sample). In Experiment 1, we assessed mnemonic discrimination of objects as well as relational binding, in a common task format. Both components follow an inverted U-shaped curve across age but were positively correlated only in the aging group. In Experiment 2, we examined mnemonic discrimination of context and its effect on relational binding. Relational memory in low-similarity contexts showed robust gains between the ages of 4 and 6, whereas 6-year-olds performed similarly to adults. In contrast, relational memory in high-similarity contexts showed more protracted development, with 4- and 6-year-olds both performing worse than young adults and not differing from each other. Relational memory in both context conditions declined in aging. This multiprocess approach provides important theoretical insights into life span changes in episodic memory. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Collapse
Affiliation(s)
- Chi T. Ngo
- Department of Psychology, Temple University
| | - Ying Lin
- Brain and Cognitive Sciences, University of Rochester
| | | | | |
Collapse
|
74
|
Holistic Recollection via Pattern Completion Involves Hippocampal Subfield CA3. J Neurosci 2019; 39:8100-8111. [PMID: 31405925 PMCID: PMC6786823 DOI: 10.1523/jneurosci.0722-19.2019] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/11/2019] [Accepted: 07/14/2019] [Indexed: 01/10/2023] Open
Abstract
Episodic memories typically comprise multiple elements. A defining characteristic of episodic retrieval is holistic recollection, i.e., comprehensive recall of the elements a memorized event encompasses. A recent study implicated activity in the human hippocampus with holistic recollection of multi-element events based on cues (Horner et al., 2015). Here, we obtained ultra-high resolution functional neuroimaging data at 7 tesla in 30 younger adults (12 female) using the same paradigm. In accordance with anatomically inspired computational models and animal research, we found that metabolic activity in hippocampal subfield CA3 (but less pronounced in dentate gyrus) correlated with this form of mnemonic pattern completion across participants. Our study provides the first evidence in humans for a strong involvement of hippocampal subfield CA3 in holistic recollection via pattern completion. SIGNIFICANCE STATEMENT Memories of daily events usually involve multiple elements, although a single element can be sufficient to prompt recollection of the whole event. Such holistic recollection is thought to require reactivation of brain activity representing the full event from one event element (“pattern completion”). Computational and animal models suggest that mnemonic pattern completion is accomplished in a specific subregion of the hippocampus called CA3, but empirical evidence in humans was lacking. Here, we leverage the ultra-high resolution of 7 tesla neuroimaging to provide first evidence for a strong involvement of the human CA3 in holistic recollection of multi-element events via pattern completion.
Collapse
|
75
|
Gicas KM, Thornton AE, Waclawik K, Wang N, Jones AA, Panenka WJ, Lang DJ, Smith GN, Vila-Rodriguez F, Leonova O, Barr AM, Procyshyn RM, Buchanan T, Su W, Vertinsky AT, Rauscher A, MacEwan GW, Honer WG. Volumes of the Hippocampal Formation Differentiate Component Processes of Memory in a Community Sample of Homeless and Marginally Housed Persons. Arch Clin Neuropsychol 2019; 34:548-562. [PMID: 30407496 DOI: 10.1093/arclin/acy066] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/10/2018] [Accepted: 07/17/2018] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVE Persons who are homeless or marginally housed exhibit significant cognitive dysfunction, with memory being the most impaired domain. Hippocampal subfield volumes have been found to differentially relate to component processes of memory. The neural correlates of memory have not been previously examined in marginalized persons who are understudied and underserved. We examined whether hippocampal subfields and entorhinal cortex volumes are uniquely related to indices of verbal episodic memory using the Hopkins Verbal Learning Test - Revised. METHOD Data was used from a large sample of community dwelling homeless and marginally housed adults (N = 227). Regression analyses were conducted to examine hippocampal subfield volumes (CA1, CA3, CA4, dentate gyrus, subiculum) and entorhinal cortex, and their associations with measures of verbal immediate recall, learning slope, and verbal delayed recall. RESULTS Greater CA3 subfield volume was associated with better performance on an index of encoding (immediate recall), but only in older individuals. Greater CA1 and subiculum volumes were associated with better performance on immediate and delayed recall (measures that tap into retrieval processes), but not with learning slope (a more pure index of encoding). Entorhinal cortex volume was related to all components of memory beyond total hippocampal volume. CONCLUSIONS Our results suggest common neuroanatomical correlates of memory dysfunction in large sample of marginalized persons, and these are uniquely related to different components of memory. These findings have clinical relevance for marginalized populations and theoretical relevance to the growing literature on functional specialization of the hippocampal subfields.
Collapse
Affiliation(s)
- Kristina M Gicas
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - Allen E Thornton
- Department of Psychology, Simon Fraser University, Burnaby, Canada
| | | | - Nena Wang
- Department of Psychology, Simon Fraser University, Burnaby, Canada
| | - Andrea A Jones
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - William J Panenka
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - Donna J Lang
- Department of Radiology, University of British Columbia, Vancouver, Canada
| | - Geoff N Smith
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | | | - Olga Leonova
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - Alasdair M Barr
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ric M Procyshyn
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - Tari Buchanan
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - Wayne Su
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | | | - Alexander Rauscher
- Department of Paediatrics, University of British Columbia, Vancouver, Canada
| | - G William MacEwan
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| | - William G Honer
- Department of Psychiatry, University of British Columbia, Vancouver, Canada
| |
Collapse
|
76
|
Starita F, Kroes MC, Davachi L, Phelps EA, Dunsmoor JE. Threat learning promotes generalization of episodic memory. J Exp Psychol Gen 2019; 148:1426-1434. [PMID: 30667260 PMCID: PMC6642861 DOI: 10.1037/xge0000551] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The ability to generalize from and distinguish between aversive memories and novel experiences is critical to survival. Previous research has revealed mechanisms underlying generalization of threat-conditioned defensive responses, but little is known about generalization of episodic memory for threatening events. Here we tested if aversive learning influences generalization of episodic memory for threatening events in human adults. Subjects underwent Pavlovian threat-conditioning in which objects from one category were paired with a shock and objects from a different category were unpaired. The next day, subjects underwent a recognition memory test that included old, highly similar, and entirely novel items from the shock-paired and shock-unpaired object categories. Results showed that items highly similar to those from the object category previously paired with shock were mistaken for old items more often than items from the shock-unpaired category. This finding indicates that threat learning promotes generalization of episodic memory, and is consistent with the idea that threat generalization is an active process that may be adaptive for avoiding a myriad of potential threats following an emotional experience. Enhanced generalization of aversive episodic memories may be maladaptive, however, when old threat memories are inappropriately reactivated in harmless situations, exemplified in a number of stress- and anxiety-related disorders. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Collapse
Affiliation(s)
- Francesca Starita
- Center for Studies and Research in Cognitive Neuroscience, Department of Psychology, University of Bologna, Bologna, 40127, Italy
| | - Marijn C.W. Kroes
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, 6525 HR, The Netherlands
- New York University, Department of Psychology, New York, NY 10003, USA
| | - Lila Davachi
- Columbia University, Department of Psychology, New York, NY 10027, USA
| | - Elizabeth A. Phelps
- New York University, Department of Psychology, New York, NY 10003, USA
- Nathan Kline Institute, Orangeburg, NY 10962, USA
| | - Joseph E. Dunsmoor
- University of Texas at Austin, Department of Psychiatry, Austin, TX 78712, USA
| |
Collapse
|
77
|
Joensen BH, Gaskell MG, Horner AJ. United we fall: All-or-none forgetting of complex episodic events. J Exp Psychol Gen 2019; 149:230-248. [PMID: 31305093 PMCID: PMC6951107 DOI: 10.1037/xge0000648] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Do complex event representations fragment over time, or are they instead forgotten in an all-or-none manner? For example, if we met a friend in a café and they gave us a present, do we forget the constituent elements of this event (location, person, and object) independently, or would the whole event be forgotten? Research suggests that item-based memories are forgotten in a fragmented manner. However, we do not know how more complex episodic, event-based memories are forgotten. We assessed both retrieval accuracy and dependency—the statistical association between the retrieval successes of different elements from the same event—for complex events. Across 4 experiments, we show that retrieval dependency is found both immediately after learning and following a 12-hr and 1-week delay. Further, the amount of retrieval dependency after a delay is greater than that predicted by a model of independent forgetting. This dependency was only seen for coherent “closed-loops,” where all pairwise associations between locations, people, and objects were encoded. When “open-loops” were learned, where only 2 out of the 3 possible associations were encoded, no dependency was seen immediately after learning or after a delay. Finally, we also provide evidence for higher retention rates for closed-loops than for open-loops. Therefore, closed-loops do not fragment as a function of forgetting and are retained for longer than are open-loops. Our findings suggest that coherent episodic events are not only retrieved, but also forgotten, in an all-or-none manner.
Collapse
|
78
|
Rollins L, Khuu A, Lodi N. Encoding variability accounts for false recognition of noncorresponding lures on the forced-choice Mnemonic Similarity Task. ACTA ACUST UNITED AC 2019; 26:280-283. [PMID: 31308246 PMCID: PMC6636543 DOI: 10.1101/lm.049593.119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Accepted: 05/14/2019] [Indexed: 11/24/2022]
Abstract
On forced-choice tests of recognition memory, performance is best when targets are paired with novel foils (A-X), followed by corresponding lures (A-A'), and then noncorresponding lures (A-B'). The current study tested the prediction that encoding variability accounts for reduced performance on A-B' trials. Young adults (n = 43) completed the forced-choice Mnemonic Similarity Task while eye movements were recorded. Errors on the A-B' test format were attributable to encoding variability; incorrect A-B' trials were associated with more fixations to the B stimulus than the A stimulus at encoding. However, encoding variability did not account for accuracy on the A-A' test format.
Collapse
Affiliation(s)
- Leslie Rollins
- Department of Psychology, Christopher Newport University, Newport News, Virginia 23606, USA
| | - Alexis Khuu
- Department of Psychology, Christopher Newport University, Newport News, Virginia 23606, USA
| | - Nafeesa Lodi
- Department of Psychology, Christopher Newport University, Newport News, Virginia 23606, USA
| |
Collapse
|
79
|
Wynn JS, Shen K, Ryan JD. Eye Movements Actively Reinstate Spatiotemporal Mnemonic Content. Vision (Basel) 2019; 3:E21. [PMID: 31735822 PMCID: PMC6802778 DOI: 10.3390/vision3020021] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 12/23/2022] Open
Abstract
Eye movements support memory encoding by binding distinct elements of the visual world into coherent representations. However, the role of eye movements in memory retrieval is less clear. We propose that eye movements play a functional role in retrieval by reinstating the encoding context. By overtly shifting attention in a manner that broadly recapitulates the spatial locations and temporal order of encoded content, eye movements facilitate access to, and reactivation of, associated details. Such mnemonic gaze reinstatement may be obligatorily recruited when task demands exceed cognitive resources, as is often observed in older adults. We review research linking gaze reinstatement to retrieval, describe the neural integration between the oculomotor and memory systems, and discuss implications for models of oculomotor control, memory, and aging.
Collapse
Affiliation(s)
- Jordana S. Wynn
- Rotman Research Institute, Baycrest, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada
- Department of Psychology, University of Toronto, 100 St George St., Toronto, ON M5S 3G3, Canada
| | - Kelly Shen
- Rotman Research Institute, Baycrest, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada
| | - Jennifer D. Ryan
- Rotman Research Institute, Baycrest, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada
- Department of Psychology, University of Toronto, 100 St George St., Toronto, ON M5S 3G3, Canada
- Department of Psychiatry, University of Toronto, 250 College St., Toronto, ON M5T 1R8, Canada
| |
Collapse
|
80
|
Sakon JJ, Suzuki WA. A neural signature of pattern separation in the monkey hippocampus. Proc Natl Acad Sci U S A 2019; 116:9634-9643. [PMID: 31010929 PMCID: PMC6511004 DOI: 10.1073/pnas.1900804116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The CA3 and dentate gyrus (DG) regions of the hippocampus are considered key for disambiguating sensory inputs from similar experiences in memory, a process termed pattern separation. The neural mechanisms underlying pattern separation, however, have been difficult to compare across species: rodents offer robust recording methods with less human-centric tasks, while humans provide complex behavior with less recording potential. To overcome these limitations, we trained monkeys to perform a visual pattern separation task similar to those used in humans while recording activity from single CA3/DG neurons. We find that, when animals discriminate recently seen novel images from similar (lure) images, behavior indicative of pattern separation, CA3/DG neurons respond to lure images more like novel than repeat images. Using a population of these neurons, we are able to classify novel, lure, and repeat images from each other using this pattern of firing rates. Notably, one subpopulation of these neurons is more responsible for distinguishing lures and repeats-the key discrimination indicative of pattern separation.
Collapse
Affiliation(s)
- John J Sakon
- Center for Neural Science, New York University, New York, NY 10003
| | - Wendy A Suzuki
- Center for Neural Science, New York University, New York, NY 10003
| |
Collapse
|
81
|
Vieweg P, Riemer M, Berron D, Wolbers T. Memory Image Completion: Establishing a task to behaviorally assess pattern completion in humans. Hippocampus 2019; 29:340-351. [PMID: 30246900 PMCID: PMC6519020 DOI: 10.1002/hipo.23030] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 08/15/2018] [Accepted: 09/13/2018] [Indexed: 11/06/2022]
Abstract
For memory retrieval, pattern completion is a crucial process that restores memories from partial or degraded cues. Neurocognitive aging models suggest that the aged memory system is biased toward pattern completion, resulting in a behavioral preference for retrieval over encoding of memories. Here, we built on our previously developed behavioral recognition memory paradigm-the Memory Image Completion (MIC) task-a task to specifically target pattern completion. First, we used the original design with concurrent eye-tracking in order to rule out perceptual confounds that could interact with recognition performance. Second, we developed parallel versions of the task to accommodate test settings in clinical environments or longitudinal studies. The results show that older adults have a deficit in pattern completion ability with a concurrent bias toward pattern completion. Importantly, eye-tracking data during encoding could not account for age-related performance differences. At retrieval, spatial viewing patterns for both age groups were more driven by stimulus identity than by response choice, but compared to young adults, older adults' fixation patterns overlapped more between stimuli that they (wrongly) thought had the same identity. This supports the observation that older adults choose responses perceived as similar to a learned stimulus, indicating a bias toward pattern completion. Additionally, two shorter versions of the task yielded comparable results, and no general learning effects were observed for repeated testing. Together, we present evidence that the MIC is a reliable behavioral task that targets pattern completion, that is easily and repeatedly applicable, and that is made freely available online.
Collapse
Affiliation(s)
- Paula Vieweg
- Institute of Psychology, University of LeipzigLeipzigGermany
- German Center for Neurodegenerative Diseases (DZNE)MagdeburgGermany
| | - Martin Riemer
- German Center for Neurodegenerative Diseases (DZNE)MagdeburgGermany
- Medical Faculty, University Hospital Magdeburg (FME)Otto von Guericke University MagdeburgMagdeburgGermany
- Center for Behavioral Brain SciencesMagdeburgGermany
| | - David Berron
- German Center for Neurodegenerative Diseases (DZNE)MagdeburgGermany
- Institute of Cognitive Neurology and Dementia Research, Otto von Guericke University MagdeburgMagdeburgGermany
- Clinical Memory Research Unit, Department of Clinical Sciences MalmöLund UniversityLundSweden
| | - Thomas Wolbers
- German Center for Neurodegenerative Diseases (DZNE)MagdeburgGermany
- Medical Faculty, University Hospital Magdeburg (FME)Otto von Guericke University MagdeburgMagdeburgGermany
- Center for Behavioral Brain SciencesMagdeburgGermany
| |
Collapse
|
82
|
Kivisaari SL, van Vliet M, Hultén A, Lindh-Knuutila T, Faisal A, Salmelin R. Reconstructing meaning from bits of information. Nat Commun 2019; 10:927. [PMID: 30804334 PMCID: PMC6389990 DOI: 10.1038/s41467-019-08848-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 01/29/2019] [Indexed: 01/09/2023] Open
Abstract
Modern theories of semantics posit that the meaning of words can be decomposed into a unique combination of semantic features (e.g., "dog" would include "barks"). Here, we demonstrate using functional MRI (fMRI) that the brain combines bits of information into meaningful object representations. Participants receive clues of individual objects in form of three isolated semantic features, given as verbal descriptions. We use machine-learning-based neural decoding to learn a mapping between individual semantic features and BOLD activation patterns. The recorded brain patterns are best decoded using a combination of not only the three semantic features that were in fact presented as clues, but a far richer set of semantic features typically linked to the target object. We conclude that our experimental protocol allowed us to demonstrate that fragmented information is combined into a complete semantic representation of an object and to identify brain regions associated with object meaning.
Collapse
Affiliation(s)
- Sasa L Kivisaari
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland. .,Aalto NeuroImaging, Aalto University, P.O. Box 12200, Aalto, FI-00076, Finland.
| | - Marijn van Vliet
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland.,Aalto NeuroImaging, Aalto University, P.O. Box 12200, Aalto, FI-00076, Finland
| | - Annika Hultén
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland.,Aalto NeuroImaging, Aalto University, P.O. Box 12200, Aalto, FI-00076, Finland
| | - Tiina Lindh-Knuutila
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland
| | - Ali Faisal
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland
| | - Riitta Salmelin
- Department of Neuroscience and Biomedical Engineering, Aalto University, P.O. Box 12200, FI-00076, Aalto, Finland.,Aalto NeuroImaging, Aalto University, P.O. Box 12200, Aalto, FI-00076, Finland
| |
Collapse
|
83
|
Hanert A, Pedersen A, Bartsch T. Transient hippocampal CA1 lesions in humans impair pattern separation performance. Hippocampus 2019; 29:736-747. [PMID: 30706576 DOI: 10.1002/hipo.23073] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 11/30/2018] [Accepted: 01/09/2019] [Indexed: 01/30/2023]
Abstract
Day-to-day life involves the perception of events that resemble one another. For the sufficient encoding and retrieval of similar information, the hippocampus provides two essential computational processes. Pattern separation refers to the differentiation of overlapping memory representations, whereas pattern completion reactivates memories based on noisy or degraded input. Evidence from human and rodent studies suggest that pattern separation specifically relies on neuronal ensemble activity in hippocampal subnetworks in the dentate gyrus and CA3. Although a role for CA1 in pattern separation has been shown in animal models, its contribution in the human hippocampus remains elusive. In order to elucidate the contribution of CA1 neurons to pattern separation, we examined 14 patients with an acute transient global amnesia (TGA), a rare self-limiting dysfunction of the hippocampal system showing specific lesions to CA1. Patients' pattern separation performance was tested during the acute amnestic phase and follow-up using an established mnemonic similarity test. Patients in the acute phase showed a profound deficit in pattern separation (p < .05) as well as recognition memory (p < .001) that recovered during follow-up. Specifically, patients tested in a later stage of the amnesia were less impaired in pattern separation than in recognition memory. Considering the time dependency of lesion-associated hippocampal deficits in early and late acute stages of the TGA, we showed that the pattern separation function recovered significantly earlier than recognition memory. Our results provide causal evidence that hippocampal CA1 neurons are critical to pattern separation performance in humans.
Collapse
Affiliation(s)
- Annika Hanert
- Memory Disorders and Plasticity Group, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, University of Kiel, Kiel, Germany
| | - Anya Pedersen
- Department of Psychology, Clinical Psychology and Psychotherapy, University of Kiel, Kiel, Germany
| | - Thorsten Bartsch
- Memory Disorders and Plasticity Group, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, University of Kiel, Kiel, Germany
| |
Collapse
|
84
|
Hanert A, Rave J, Granert O, Ziegler M, Pedersen A, Born J, Finke C, Bartsch T. Hippocampal Dentate Gyrus Atrophy Predicts Pattern Separation Impairment in Patients with LGI1 Encephalitis. Neuroscience 2019; 400:120-131. [PMID: 30625332 DOI: 10.1016/j.neuroscience.2018.12.046] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 12/18/2018] [Accepted: 12/25/2018] [Indexed: 12/27/2022]
Abstract
Day-to-day life involves the perception of events that resemble one another. For the sufficient encoding and correct retrieval of similar information, the hippocampus provides two essential cognitive processes. Pattern separation refers to the differentiation of similar input information, whereas pattern completion reactivates memory representations based on noisy or degraded stimuli. It has been shown that pattern separation specifically relies on the hippocampal dentate gyrus (DG), whereas pattern completion is performed within CA3 networks. Lesions to these hippocampal networks emerging in the course of neurological disorders may thus affect both processes. In anti-leucine-rich, glioma-inactivated 1 (LGI1) encephalitis it has been shown in animal models and human imaging studies that hippocampal DG and CA3 are preferentially involved in the pathophysiology process. Thus, in order to elucidate the structure-function relationship and contribution of hippocampal subfields to pattern separation, we examined patients (n = 15, age range: 36-77 years) with the rare LGI1 encephalitis showing lesions to hippocampal subfields. Patients were tested 3.53 ± 0.65 years after the acute phase of the disease. Structural sequelae were determined by hippocampal subfield volumetry for the DG, CA1, and CA2/3. Patients showed an overall memory deficit including a significant reduction in pattern separation performance (p = 0.016). In volumetry, we found a global hippocampal volume reduction. The deficits in pattern separation performance were best predicted by the DG (p = 0.029), whereas CA1 was highly predictive of recognition memory deficits (p < 0.001). These results corroborate the framework of a regional specialization of hippocampal functions involved in cognitive processing.
Collapse
Affiliation(s)
- Annika Hanert
- Dept. of Neurology, Memory Disorders and Plasticity Group, University Hospital Schleswig-Holstein, University of Kiel, Arnold-Heller-Str. 3, 24105 Kiel, Germany.
| | - Julius Rave
- Dept. of Neurology, Memory Disorders and Plasticity Group, University Hospital Schleswig-Holstein, University of Kiel, Arnold-Heller-Str. 3, 24105 Kiel, Germany.
| | - Oliver Granert
- Dept. of Neurology, Memory Disorders and Plasticity Group, University Hospital Schleswig-Holstein, University of Kiel, Arnold-Heller-Str. 3, 24105 Kiel, Germany.
| | - Martin Ziegler
- Nanoelectronics, Technical Faculty, University of Kiel, Kaiserstr 2, 24143 Kiel, Germany.
| | - Anya Pedersen
- Dept. of Psychology, Clinical Psychology and Psychotherapy, University of Kiel, Olshausenstr 62, 24118 Kiel, Germany.
| | - Jan Born
- Institute for Medical Psychology and Behavioral Neurobiology, University of Tübingen, Otfried-Müller-Str. 25, 72076 Tübingen, Germany.
| | - Carsten Finke
- Dept. of Neurology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
| | - Thorsten Bartsch
- Dept. of Neurology, Memory Disorders and Plasticity Group, University Hospital Schleswig-Holstein, University of Kiel, Arnold-Heller-Str. 3, 24105 Kiel, Germany.
| |
Collapse
|
85
|
Yagi S, Galea LAM. Sex differences in hippocampal cognition and neurogenesis. Neuropsychopharmacology 2019; 44:200-213. [PMID: 30214058 PMCID: PMC6235970 DOI: 10.1038/s41386-018-0208-4] [Citation(s) in RCA: 193] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 08/29/2018] [Accepted: 08/30/2018] [Indexed: 12/27/2022]
Abstract
Sex differences are reported in hippocampal plasticity, cognition, and in a number of disorders that target the integrity of the hippocampus. For example, meta-analyses reveal that males outperform females on hippocampus-dependent tasks in rodents and in humans, furthermore women are more likely to experience greater cognitive decline in Alzheimer's disease and depression, both diseases characterized by hippocampal dysfunction. The hippocampus is a highly plastic structure, important for processing higher order information and is sensitive to the environmental factors such as stress. The structure retains the ability to produce new neurons and this process plays an important role in pattern separation, proactive interference, and cognitive flexibility. Intriguingly, there are prominent sex differences in the level of neurogenesis and the activation of new neurons in response to hippocampus-dependent cognitive tasks in rodents. However, sex differences in spatial performance can be nuanced as animal studies have demonstrated that there are task, and strategy choice dependent sex differences in performance, as well as sex differences in the subregions of the hippocampus influenced by learning. This review discusses sex differences in pattern separation, pattern completion, spatial learning, and links between adult neurogenesis and these cognitive functions of the hippocampus. We emphasize the importance of including both sexes when studying genomic, cellular, and structural mechanisms of the hippocampal function.
Collapse
Affiliation(s)
- Shunya Yagi
- Department of Psychology, Graduate Program in Neuroscience, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Liisa A M Galea
- Department of Psychology, Graduate Program in Neuroscience, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
| |
Collapse
|
86
|
Investigation of the CADM2 polymorphism rs17518584 in memory and executive functions measures in a cohort of young healthy individuals. Neurobiol Learn Mem 2018; 155:330-336. [PMID: 30125698 DOI: 10.1016/j.nlm.2018.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 07/04/2018] [Accepted: 08/02/2018] [Indexed: 11/22/2022]
Abstract
The common polymorphism rs17518584, near the cell adhesion molecule 2 gene (CADM2), was previously identified as playing a role in information processing speed in a genome-wide association study of executive functions and processing speed performed in a cohort of non-demented older adults. In this study, we investigated this polymorphism in a younger population cohort (≤30 years old, median age 19 years), with no known memory or psychiatric disorders, for which we had phenotyped all participants for memory function (n = 514), and a subset of the participants for executive functions (n = 338), using a battery of tests measuring visuo-spatial memory, working memory, verbal memory, and frontal lobe functions (visual scanning, graphomotor speed, and cognitive flexibility). The polymorphism rs17518584 was genotyped by a restriction fragment length polymorphism assay and analysis indicated that the CADM2 polymorphism showed evidence of association with information processing speed as inferred from scores from the Stroop Word, Colour, and Colour-Word Tests (p = 0.005, p = 0.04, and p = 0.028, respectively, in a dominant inheritance model), as well as Trail Making Test Part A (p = 0.005 in an additive model). Significant associations of rs17518584 with scores from other tests of memory subtypes were not detected. The findings of this study provide further support for a role of CADM2 in aspects of cognitive function, in particular reading and information processing speed, and suggest that this role extends to younger individuals.
Collapse
|
87
|
Sevenster D, de Oliveira Alvares L, D’Hooge R. Pre-exposure and retrieval effects on generalization of contextual fear. LEARNING AND MOTIVATION 2018. [DOI: 10.1016/j.lmot.2017.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
88
|
Abstract
Memories for events are thought to be represented in sparse, distributed neuronal ensembles (or engrams). In this article, we review how neurons are chosen to become part of a particular engram, via a process of neuronal allocation. Experiments in rodents indicate that eligible neurons compete for allocation to a given engram, with more excitable neurons winning this competition. Moreover, fluctuations in neuronal excitability determine how engrams interact, promoting either memory integration (via coallocation to overlapping engrams) or separation (via disallocation to nonoverlapping engrams). In parallel with rodent studies, recent findings in humans verify the importance of this memory integration process for linking memories that occur close in time or share related content. A deeper understanding of allocation promises to provide insights into the logic underlying how knowledge is normally organized in the brain and the disorders in which this process has gone awry.
Collapse
Affiliation(s)
- Sheena A Josselyn
- Department of Psychology, University of Toronto, Ontario M5S 3G3, Canada; ,
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
- Department of Physiology, University of Toronto, Ontario M5S 1A8, Canada
- Institute of Medical Sciences, University of Toronto, Ontario M5S 1A8, Canada
- Brain, Mind & Consciousness Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1M1, Canada
| | - Paul W Frankland
- Department of Psychology, University of Toronto, Ontario M5S 3G3, Canada; ,
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
- Department of Physiology, University of Toronto, Ontario M5S 1A8, Canada
- Institute of Medical Sciences, University of Toronto, Ontario M5S 1A8, Canada
- Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1M1, Canada
| |
Collapse
|
89
|
Keresztes A, Ngo CT, Lindenberger U, Werkle-Bergner M, Newcombe NS. Hippocampal Maturation Drives Memory from Generalization to Specificity. Trends Cogn Sci 2018; 22:676-686. [PMID: 29934029 DOI: 10.1016/j.tics.2018.05.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/27/2018] [Accepted: 05/17/2018] [Indexed: 01/15/2023]
Abstract
During early ontogeny, the rapid and cumulative acquisition of world knowledge contrasts with slower improvements in the ability to lay down detailed and long-lasting episodic memories. This emphasis on generalization at the expense of specificity persists well into middle childhood and possibly into adolescence. During this period, recognizing regularities, forming stable representations of recurring episodes, predicting the structure of future events, and building up semantic knowledge may be prioritized over remembering specific episodes. We highlight recent behavioral and neuroimaging evidence suggesting that maturational differences among subfields within the hippocampus contribute to the developmental lead-lag relation between generalization and specificity, and lay out future research directions.
Collapse
Affiliation(s)
- Attila Keresztes
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.
| | - Chi T Ngo
- Department of Psychology, Temple University, Philadelphia, PA, USA
| | - Ulman Lindenberger
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany; Max Planck-University College London (UCL) Centre for Computational Psychiatry and Ageing Research, London, England, and Berlin, Germany
| | - Markus Werkle-Bergner
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany
| | - Nora S Newcombe
- Department of Psychology, Temple University, Philadelphia, PA, USA
| |
Collapse
|
90
|
Is There a Role for Pattern Separation during Sleep? J Neurosci 2018; 38:4062-4064. [PMID: 29695440 DOI: 10.1523/jneurosci.0167-18.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 03/09/2018] [Accepted: 03/19/2018] [Indexed: 11/21/2022] Open
|
91
|
Węsierska M, Dziendzikowska K, Gromadzka-Ostrowska J, Dudek J, Polkowska-Motrenko H, Audinot JN, Gutleb AC, Lankoff A, Kruszewski M. Silver ions are responsible for memory impairment induced by oral administration of silver nanoparticles. Toxicol Lett 2018; 290:133-144. [PMID: 29578054 DOI: 10.1016/j.toxlet.2018.03.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 02/14/2018] [Accepted: 03/18/2018] [Indexed: 12/20/2022]
Abstract
Increasing use of silver nanoparticles (AgNPs) results in increased human exposure. AgNPs are able to cross brain-blood barrier and are a risk factor for the brain. Thus, we hypothesized that AgNPs exposure might affect hippocampal dependent memory, which required cognitive coordination processes. To verify the assumption, in this study we evaluated the effects of orally administered bovine serum albumin (BSA)-coated AgNPs on spatial memory, which engage cognitive coordination processes for on-going stimuli segregation. Rats following 28 days of oral administration with 1 mg/kg (n = 10) or 30 mg/kg (n = 10) BSA-AgNPs or saline, a control groups (n = 10, n = 8), were tested with an active place avoidance task in the Carousel Maze test. The study revealed significant impairment of long- and short-term memory, irrespectively of dose of AgNPs, whereas non-cognitive activity was on a similar level. We found significantly higher content of silver in the hippocampus in comparison to the lateral cortex. No silver was found in the cerebellum and the frontal cortex. The nanoSIMS analysis reveal a weak signal of silver in the hippocampus of AgNPs treated animals that should be attributed to the presence of silver in ionic form rather than AgNPs. Our findings indicate that oral exposure to a low dose AgNPs induces detrimental effect on memory and cognitive coordination processes. The presence of silver ions rather than AgNPs in different brain regions, in particular the hippocampus, suggests crucial role of silver ions in AgNPs-induced impairment of the higher brain functions.
Collapse
Affiliation(s)
- M Węsierska
- Department of Neurophysiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland.
| | - K Dziendzikowska
- Division of Nutrition Physiology, Department of Dietetics, Faculty of Human Nutrition and Consumer Science, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159C, 02-776 Warsaw, Poland.
| | - J Gromadzka-Ostrowska
- Division of Nutrition Physiology, Department of Dietetics, Faculty of Human Nutrition and Consumer Science, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159C, 02-776 Warsaw, Poland
| | - J Dudek
- Laboratory of Nuclear Analytical Methods, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland
| | - H Polkowska-Motrenko
- Laboratory of Nuclear Analytical Methods, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland
| | - J N Audinot
- Materials Research and Technology (MRT) Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Forneaux, L-4362 Esch-sur-Alzette, Luxembourg
| | - A C Gutleb
- Environmental Research and Innovation (ERIN) Department, Luxembourg Institute of Science and Technology (LIST), 5 avenue des Hauts-Forneaux, L-4362 Esch-sur-Alzette, Luxembourg
| | - A Lankoff
- Centre for Radiobiology and Biological Dosimetry, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland; Department of Radiobiology and Immunology, Institute of Biology, Jan Kochanowski University, Świetokrzyska 15, 25-406 Kielce, Poland
| | - M Kruszewski
- Centre for Radiobiology and Biological Dosimetry, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland; Department of Molecular Biology and Translational Research, Institute of Rural Health, Jaczewskiego 2, 20-090 Lublin, Poland; Department of Medical Biology and Translational Research, Faculty of Medicine, University of Information Technology and Management, Sucharskiego 2, 35-225 Rzeszów, Poland
| |
Collapse
|
92
|
Antoniades M, Schoeler T, Radua J, Valli I, Allen P, Kempton MJ, McGuire P. Verbal learning and hippocampal dysfunction in schizophrenia: A meta-analysis. Neurosci Biobehav Rev 2018; 86:166-175. [PMID: 29223768 PMCID: PMC5818020 DOI: 10.1016/j.neubiorev.2017.12.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 10/24/2017] [Accepted: 12/01/2017] [Indexed: 12/19/2022]
Abstract
This meta-analysis summarizes research examining whether deficits in verbal learning are related to bilateral hippocampal volume reductions in patients with or at risk for schizophrenia and in healthy controls. 17 studies with 755 patients with schizophrenia (SCZ), 232 Genetic High Risk (GHR) subjects and 914 healthy controls (HC) were included. Pooled correlation coefficients were calculated between hemisphere (left, right or total) and type of recall (immediate or delayed) for each diagnostic group individually (SCZ, GHR and HC). In SCZ, left and right hippocampal volume positively correlated with immediate (r=0.256, 0.230) and delayed (r=0.132, 0.231) verbal recall. There was also a correlation between total hippocampal volume and delayed recall (r=0.233). None of these correlations were significant in healthy controls. There was however, a positive correlation between left hippocampal volume and immediate recall in the GHR group (r=0.356). The results suggest that hippocampal volume affects immediate and delayed verbal learning capacity in schizophrenia and provides further evidence of hippocampal dysfunction in the pathophysiology of schizophrenia.
Collapse
Affiliation(s)
- Mathilde Antoniades
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK.
| | - Tabea Schoeler
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK
| | - Joaquim Radua
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK; FIDMAG Germanes Hospitalàries - CIBERSAM, Sant Boi de Llobregat, Barcelona, Spain; Centre for Psychiatric Research and Education, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Isabel Valli
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK
| | - Paul Allen
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK; Department of Psychology, University of Roehampton, London, UK
| | - Matthew J Kempton
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK
| | - Philip McGuire
- Department of Psychosis Studies, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK
| |
Collapse
|
93
|
Unfolding the cognitive map: The role of hippocampal and extra-hippocampal substrates based on a systems analysis of spatial processing. Neurobiol Learn Mem 2018; 147:90-119. [DOI: 10.1016/j.nlm.2017.11.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 11/17/2017] [Accepted: 11/21/2017] [Indexed: 01/03/2023]
|
94
|
Putting fear in context: Elucidating the role of the retrosplenial cortex in context discrimination in rats. Neurobiol Learn Mem 2017; 148:50-59. [PMID: 29294384 DOI: 10.1016/j.nlm.2017.12.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/15/2017] [Accepted: 12/29/2017] [Indexed: 01/08/2023]
Abstract
The retrosplenial cortex (RSC), which receives visuo-spatial sensory input and interacts with numerous hippocampal memory system structures, has a well-established role in contextual learning and memory. While it has been demonstrated that RSC function is necessary to learn to recognize a single environment that is directly paired with an aversive event, the role of the RSC in discriminating between two different contexts remains largely unknown. To address this, first order (Experiment 1) and higher order (Experiment 2) fear conditioning paradigms were conducted with sham and RSC-lesioned rats. In Experiment 1 rats were exposed to one context in which shock was delivered and to a second, distinct context without shock. Their ability to discriminate between the contexts was assessed during a re-exposure test. In a second experiment, a new cohort of RSC-lesioned rats was exposed to two contexts made distinct through visual, olfactory and auditory stimuli. In a subsequent conditioning phase, the salience of one of the auditory stimuli was paired to an aversive footshock while the other was not. Similar to Experiment 1, freezing behavior was analyzed upon re-exposure to the contexts in the absence of both the auditory cue and the footshock. The results revealed that RSC is not necessary for rats to use contextual information to successfully discriminate between two contexts under the relatively simple demands involved in this first order conditioning paradigm but that context discrimination is impaired when the processing of complex and/or ambiguous contextual stimuli is required to select appropriate behavioral responses.
Collapse
|
95
|
Ferrara K, Furlong S, Park S, Landau B. Detailed Visual Memory Capacity Is Present Early in Childhood. Open Mind (Camb) 2017; 1:136-147. [PMID: 30931420 PMCID: PMC6436559 DOI: 10.1162/opmi_a_00014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Accepted: 08/24/2017] [Indexed: 12/05/2022] Open
Abstract
Previous studies have shown that adults are able to remember more than 1,000 images with great detail. However, little is known about the development of this visual capacity, nor its presence early in life. This study tests the level of detail of young children's memory for a large number of items, adapting the method of Brady, Konkle, Alvarez, and Oliva (2008). Four- and six-year-old children were shown more than 100 images of everyday objects. They were then tested for recognition of familiar items in a binary decision task. The identity of the foil test item was manipulated in three conditions (Category, Exemplar, and State). Children demonstrated high accuracy across all conditions, remembering not only the basic-level category (Category), but also unique details (Exemplar), and information about position and arrangement of parts (State). These findings demonstrate that children spontaneously encode a high degree of visual detail. Early in life, visual memory exhibits high fidelity and extends over a large set of items.
Collapse
Affiliation(s)
| | - Sarah Furlong
- Department of Cognitive Science, Johns Hopkins University
| | - Soojin Park
- Department of Cognitive Science, Johns Hopkins University
- Department of Psychology, Yonsei University
| | - Barbara Landau
- Department of Cognitive Science, Johns Hopkins University
| |
Collapse
|
96
|
Sleep in Humans Stabilizes Pattern Separation Performance. J Neurosci 2017; 37:12238-12246. [PMID: 29118106 DOI: 10.1523/jneurosci.1189-17.2017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 09/20/2017] [Accepted: 09/27/2017] [Indexed: 12/22/2022] Open
Abstract
Replay of hippocampal neural representations during sleep is thought to promote systems consolidation of declarative memory. How this reprocessing of memory during sleep affects the hippocampal representation itself, is unclear. Here we tested hippocampal stimulus processing (i.e., pattern separation) before and after periods of sleep and wakefulness in humans (female and male participants). Pattern separation deteriorated across the wake period but remained stable across sleep (p = 0.013) with this sleep-wake difference being most pronounced for stimuli with low similarity to targets (p = 0.006). Stimuli with the highest similarity showed a reversed pattern with reduced pattern separation performance after sleep (p = 0.038). Pattern separation performance was positively correlated with sleep spindle density, slow oscillation density, and theta power phase-locked to slow oscillations. Sleep, presumably by neural memory replay, shapes hippocampal representations and enhances computations of pattern separation to subsequent presentation of similar stimuli.SIGNIFICANCE STATEMENT The consolidation of hippocampus-dependent memories is causally related to reactivation during sleep of previously encoded representations. Here, we show that reactivation-based consolidation processes during sleep shape the hippocampal representation itself. We studied the effect of sleep and wakefulness on pattern separation (i.e., orthogonalization of similar representations) and completion performance (i.e., recall of a memory in light of noisy input) that are essential cognitive elements of encoding and retrieval of information by the hippocampus. Our results demonstrate that pattern separation was stabilized after sleep but diminished after wakefulness. We further showed that pattern separation was related to EEG oscillatory parameters of non-REM sleep serving as markers of sleep-dependent memory consolidation and hippocampal reactivation.
Collapse
|
97
|
Abstract
Emerging evidence suggests that age-related declines in memory may reflect a failure in pattern separation, a process that is believed to reduce the encoding overlap between similar stimulus representations during memory encoding. Indeed, behavioural pattern separation may be indexed by a visual continuous recognition task in which items are presented in sequence and observers report for each whether it is novel, previously viewed (old), or whether it shares features with a previously viewed item (similar). In comparison to young adults, older adults show a decreased pattern separation when the number of items between "old" and "similar" items is increased. Yet the mechanisms of forgetting underpinning this type of recognition task are yet to be explored in a cognitively homogenous group, with careful control over the parameters of the task, including elapsing time (a critical variable in models of forgetting). By extending the inter-item intervals, number of intervening items and overall decay interval, we observed in a young adult sample (N = 35, Mage = 19.56 years) that the critical factor governing performance was inter-item interval. We argue that tasks using behavioural continuous recognition to index pattern separation in immediate memory will benefit from generous inter-item spacing, offering protection from inter-item interference.
Collapse
Affiliation(s)
- Amy V Smith
- a School of Psychology , University of Leeds , Leeds , UK
| | - Denis McKeown
- a School of Psychology , University of Leeds , Leeds , UK
| | - David Bunce
- a School of Psychology , University of Leeds , Leeds , UK
| |
Collapse
|
98
|
Lui E, Salim M, Chahal M, Puri N, Marandi E, Quadrilatero J, Satvat E. Chronic corticosterone-induced impaired cognitive flexibility is not due to suppressed adult hippocampal neurogenesis. Behav Brain Res 2017; 332:90-98. [DOI: 10.1016/j.bbr.2017.05.060] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 05/22/2017] [Accepted: 05/25/2017] [Indexed: 12/20/2022]
|
99
|
Abstract
Millions of individuals suffer from age-related cognitive decline, defined by impaired memory precision. Increased understanding of hippocampal circuit mechanisms underlying memory formation suggests a role for computational processes such as pattern separation and pattern completion in memory precision. We describe evidence implicating the dentate gyrus-CA3 circuit in pattern separation and completion, and examine alterations in dentate gyrus-CA3 circuit structure and function with aging. We discuss the role of adult hippocampal neurogenesis in memory precision in adulthood and aging, as well as the circuit mechanisms underlying the integration and encoding functions of adult-born dentate granule cells. We posit that understanding these circuit mechanisms will permit generation of circuit-based endophenotypes that will edify new therapeutic strategies to optimize hippocampal encoding during aging.
Collapse
Affiliation(s)
- Kathleen M McAvoy
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Harvard Stem Cell Institute, Cambridge, MA, 02138, USA
- Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA.
- Harvard Stem Cell Institute, Cambridge, MA, 02138, USA.
- Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
- BROAD Institute of Harvard and MIT, Cambridge, MA, 02142, USA.
| |
Collapse
|
100
|
Clark CA, Fernandez F, Sakhon S, Spanò G, Edgin JO. The medial temporal memory system in Down syndrome: Translating animal models of hippocampal compromise. Hippocampus 2017; 27:683-691. [PMID: 28346765 PMCID: PMC8109260 DOI: 10.1002/hipo.22724] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 09/06/2016] [Accepted: 03/07/2017] [Indexed: 01/19/2023]
Abstract
Recent studies have highlighted the dentate gyrus as a region of increased vulnerability in mouse models of Down syndrome (DS). It is unclear to what extent these findings are reflected in the memory profile of people with the condition. We developed a series of novel tasks to probe distinct medial temporal functions in children and young adults with DS, including object, spatial, and temporal order memory. Relative to mental age-matched controls (n = 45), individuals with DS (n = 28) were unimpaired on subtests involving short-term object or configural recall that was divorced from spatial or temporal contexts. By contrast, the DS group had difficulty recalling spatial locations when contextual information was salient and recalling the order in which objects were serially presented. Results are consistent with dysfunction of spatial and temporal contextual pattern separation abilities in individuals with DS, mediated by the hippocampus, including the dentate gyrus. Amidst increasing calls to bridge human and animal work, the memory profile demonstrated here in humans with DS is strikingly similar to that of the Ts65Dn mouse model of DS. The study highlights the trisynaptic circuit as a potentially fruitful intervention target to mitigate cognitive impairments associated with DS.
Collapse
Affiliation(s)
- Caron A.C. Clark
- Department of Psychology, Memory Development and Disorders Laboratory, University of Arizona, Tucson, Arizona
- Department of Educational Psychology, University of Nebraska, Lincoln, Nebraska
| | - Fabian Fernandez
- Department of Psychology, BIO5 and McKnight Brain Research Institutes, University of Arizona, Tucson, Arizona
- Department of Neurology, BIO5 and McKnight Brain Research Institutes, University of Arizona, Tucson, Arizona
| | - Stella Sakhon
- Department of Psychology, Memory Development and Disorders Laboratory, University of Arizona, Tucson, Arizona
| | - Goffredina Spanò
- Department of Psychology, Memory Development and Disorders Laboratory, University of Arizona, Tucson, Arizona
| | - Jamie O. Edgin
- Department of Psychology, Memory Development and Disorders Laboratory, University of Arizona, Tucson, Arizona
| |
Collapse
|