1
|
Grella SL, Donaldson TN. Contextual memory engrams, and the neuromodulatory influence of the locus coeruleus. Front Mol Neurosci 2024; 17:1342622. [PMID: 38375501 PMCID: PMC10875109 DOI: 10.3389/fnmol.2024.1342622] [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: 11/22/2023] [Accepted: 01/19/2024] [Indexed: 02/21/2024] Open
Abstract
Here, we review the basis of contextual memory at a conceptual and cellular level. We begin with an overview of the philosophical foundations of traversing space, followed by theories covering the material bases of contextual representations in the hippocampus (engrams), exploring functional characteristics of the cells and subfields within. Next, we explore various methodological approaches for investigating contextual memory engrams, emphasizing plasticity mechanisms. This leads us to discuss the role of neuromodulatory inputs in governing these dynamic changes. We then outline a recent hypothesis involving noradrenergic and dopaminergic projections from the locus coeruleus (LC) to different subregions of the hippocampus, in sculpting contextual representations, giving a brief description of the neuroanatomical and physiological properties of the LC. Finally, we examine how activity in the LC influences contextual memory processes through synaptic plasticity mechanisms to alter hippocampal engrams. Overall, we find that phasic activation of the LC plays an important role in promoting new learning and altering mnemonic processes at the behavioral and cellular level through the neuromodulatory influence of NE/DA in the hippocampus. These findings may provide insight into mechanisms of hippocampal remapping and memory updating, memory processes that are potentially dysregulated in certain psychiatric and neurodegenerative disorders.
Collapse
Affiliation(s)
- Stephanie L. Grella
- MNEME Lab, Department of Psychology, Program in Neuroscience, Loyola University Chicago, Chicago, IL, United States
| | - Tia N. Donaldson
- Systems Neuroscience and Behavior Lab, Department of Psychology, The University of New Mexico, Albuquerque, NM, United States
| |
Collapse
|
2
|
Zheng Y, Liu XL, Nishiyama S, Ranganath C, O’Reilly RC. Correcting the hebbian mistake: Toward a fully error-driven hippocampus. PLoS Comput Biol 2022; 18:e1010589. [PMID: 36219613 PMCID: PMC9586412 DOI: 10.1371/journal.pcbi.1010589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 10/21/2022] [Accepted: 09/19/2022] [Indexed: 11/18/2022] Open
Abstract
The hippocampus plays a critical role in the rapid learning of new episodic memories. Many computational models propose that the hippocampus is an autoassociator that relies on Hebbian learning (i.e., "cells that fire together, wire together"). However, Hebbian learning is computationally suboptimal as it does not learn in a way that is driven toward, and limited by, the objective of achieving effective retrieval. Thus, Hebbian learning results in more interference and a lower overall capacity. Our previous computational models have utilized a powerful, biologically plausible form of error-driven learning in hippocampal CA1 and entorhinal cortex (EC) (functioning as a sparse autoencoder) by contrasting local activity states at different phases in the theta cycle. Based on specific neural data and a recent abstract computational model, we propose a new model called Theremin (Total Hippocampal ERror MINimization) that extends error-driven learning to area CA3-the mnemonic heart of the hippocampal system. In the model, CA3 responds to the EC monosynaptic input prior to the EC disynaptic input through dentate gyrus (DG), giving rise to a temporal difference between these two activation states, which drives error-driven learning in the EC→CA3 and CA3↔CA3 projections. In effect, DG serves as a teacher to CA3, correcting its patterns into more pattern-separated ones, thereby reducing interference. Results showed that Theremin, compared with our original Hebbian-based model, has significantly increased capacity and learning speed. The model makes several novel predictions that can be tested in future studies.
Collapse
Affiliation(s)
- Yicong Zheng
- Department of Psychology, University of California, Davis, California, United States of America
- Center for Neuroscience, University of California, Davis, California, United States of America
| | - Xiaonan L. Liu
- Department of Psychology, The Chinese University of Hong Kong, Hong Kong, People’s Republic of China
| | - Satoru Nishiyama
- Graduate School of Education, Kyoto University, Kyoto, Japan
- Japan Society for the Promotion of Science, Tokyo, Japan
| | - Charan Ranganath
- Department of Psychology, University of California, Davis, California, United States of America
- Center for Neuroscience, University of California, Davis, California, United States of America
| | - Randall C. O’Reilly
- Department of Psychology, University of California, Davis, California, United States of America
- Center for Neuroscience, University of California, Davis, California, United States of America
- Department of Computer Science, University of California, Davis, California, United States of America
- * E-mail:
| |
Collapse
|
3
|
Hones VI, Mizumori SJY. Response Flexibility: The Role of the Lateral Habenula. Front Behav Neurosci 2022; 16:852235. [PMID: 35444521 PMCID: PMC9014270 DOI: 10.3389/fnbeh.2022.852235] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/01/2022] [Indexed: 01/13/2023] Open
Abstract
The ability to make appropriate decisions that result in an optimal outcome is critical for survival. This process involves assessing the environment as well as integrating prior knowledge about the environment with information about one’s current internal state. There are many neural structures that play critical roles in mediating these processes, but it is not yet known how such information coalesces to influence behavioral output. The lateral habenula (LHb) has often been cited as a structure critical for adaptive and flexible responding when environmental contexts and internal state changes. A challenge, however, has been understanding how LHb promotes response flexibility. In this review, we hypothesize that the LHb enables flexible responding following the integration of context memory and internal state information by signaling downstream brainstem structures known to drive hippocampal theta. In this way, animals respond more flexibly in a task situation not because the LHb selects a particular action, but rather because LHb enhances a hippocampal neural state that is often associated with greater attention, arousal, and exploration. In freely navigating animals, these are essential conditions that are needed to discover and implement appropriate alternative choices and behaviors. As a corollary to our hypothesis, we describe short- and intermediate-term functions of the LHb. Finally, we discuss the effects on the behavior of LHb dysfunction in short- and intermediate-timescales, and then suggest that new therapies may act on the LHb to alleviate the behavioral impairments following long-term LHb disruption.
Collapse
Affiliation(s)
- Victoria I. Hones
- Department of Psychology, University of Washington, Seattle, WA, United States
| | - Sheri J. Y. Mizumori
- Department of Psychology, University of Washington, Seattle, WA, United States
- Graduate Program in Neuroscience, University of Washington, Seattle, WA, United States
- *Correspondence: Sheri J. Y. Mizumori
| |
Collapse
|
4
|
Kalbe F, Schwabe L. Prediction Errors for Aversive Events Shape Long-Term Memory Formation through a Distinct Neural Mechanism. Cereb Cortex 2021; 32:3081-3097. [PMID: 34849622 DOI: 10.1093/cercor/bhab402] [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: 06/25/2021] [Revised: 09/09/2021] [Accepted: 10/12/2021] [Indexed: 11/13/2022] Open
Abstract
Prediction errors (PEs) have been known for decades to guide associative learning, but their role in episodic memory formation has been discovered only recently. To identify the neural mechanisms underlying the impact of aversive PEs on long-term memory formation, we used functional magnetic resonance imaging, while participants saw a series of unique stimuli and estimated the probability that an aversive shock would follow. Our behavioral data showed that negative PEs (i.e., omission of an expected outcome) were associated with superior recognition of the predictive stimuli, whereas positive PEs (i.e., presentation of an unexpected outcome) impaired subsequent memory. While medial temporal lobe (MTL) activity during stimulus encoding was overall associated with enhanced memory, memory-enhancing effects of negative PEs were linked to even decreased MTL activation. Additional large-scale network analyses showed PE-related increases in crosstalk between the "salience network" and a frontoparietal network commonly implicated in memory formation for expectancy-congruent events. These effects could not be explained by mere changes in physiological arousal or the prediction itself. Our results suggest that the superior memory for events associated with negative aversive PEs is driven by a potentially distinct neural mechanism that might serve to set these memories apart from those with expected outcomes.
Collapse
Affiliation(s)
- Felix Kalbe
- Department of Cognitive Psychology, Institute of Psychology, Universität Hamburg, Hamburg 20146, Germany
| | - Lars Schwabe
- Department of Cognitive Psychology, Institute of Psychology, Universität Hamburg, Hamburg 20146, Germany
| |
Collapse
|
5
|
Nelson AJD. The anterior thalamic nuclei and cognition: A role beyond space? Neurosci Biobehav Rev 2021; 126:1-11. [PMID: 33737105 PMCID: PMC8363507 DOI: 10.1016/j.neubiorev.2021.02.047] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 02/19/2021] [Accepted: 02/24/2021] [Indexed: 12/25/2022]
Abstract
Anterior thalamic nuclei important for specific classes of temporal discriminations. Anterior thalamic nuclei required for hippocampal-dependent contextual processes. Critical role for anterior thalamic nuclei in selective attention. Significance of anterior thalamic – anterior cingulate interactions.
The anterior thalamic nuclei are a vital node within hippocampal-diencephalic-cingulate circuits that support spatial learning and memory. Reflecting this interconnectivity, the overwhelming focus of research into the cognitive functions of the anterior thalamic nuclei has been spatial processing. However, there is increasing evidence that the functions of the anterior thalamic nuclei extend beyond the spatial realm. This work has highlighted how these nuclei are required for certain classes of temporal discrimination as well as their importance for processing other contextual information; revealing parallels with the non-spatial functions of the hippocampal formation. Yet further work has shown how the anterior thalamic nuclei may be important for other forms of non-spatial learning, including a critical role for these nuclei in attentional mechanisms. This evidence signals the need to reconsider the functions of the anterior thalamic within the framework of their wider connections with sites including the anterior cingulate cortex that subserve non-spatial functions.
Collapse
Affiliation(s)
- Andrew J D Nelson
- School of Psychology, Cardiff University, 70 Park Place, Cardiff, CF10 3AT, Wales, UK.
| |
Collapse
|
6
|
Stark SM, Reagh ZM, Yassa MA, Stark CEL. What's in a context? Cautions, limitations, and potential paths forward. Neurosci Lett 2018; 680:77-87. [PMID: 28529173 PMCID: PMC5735015 DOI: 10.1016/j.neulet.2017.05.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 05/09/2017] [Accepted: 05/10/2017] [Indexed: 01/25/2023]
Abstract
The purpose of memory is to guide current and future behavior based on previous experiences. Part of this process involves either discriminating between or generalizing across similar experiences that contain overlapping conditions (such as space, time, or internal state), which we often conceptualize as "contexts". In this review, we highlight major challenges facing the field as we attempt a neuroscience-based approach to the study of context and its impact on learning and memory. Here, we review some of the methodologies and approaches used to investigate context in both animals and humans, including the neurobiological mechanisms involved. Finally, we propose three tenets for operationalizing context in the experimental setting: 1) contexts must be stable over time along an experiential dimension; 2) contexts must be at least moderately complex in nature and their representations must be modifiable or adaptable, and 3) contexts must have some behavioral relevance (be it overt or incidental) so that its role can be measured.
Collapse
Affiliation(s)
- Shauna M Stark
- Department of Neurobiology & Behavior, University of California, Irvine, United States; Center for the Neurobiology of Learning and Memory, University of California, Irvine, United States
| | - Zachariah M Reagh
- Department of Neurobiology & Behavior, University of California, Irvine, United States; Center for the Neurobiology of Learning and Memory, University of California, Irvine, United States
| | - Michael A Yassa
- Department of Neurobiology & Behavior, University of California, Irvine, United States; Center for the Neurobiology of Learning and Memory, University of California, Irvine, United States.
| | - Craig E L Stark
- Department of Neurobiology & Behavior, University of California, Irvine, United States; Center for the Neurobiology of Learning and Memory, University of California, Irvine, United States.
| |
Collapse
|
7
|
Reward-Based Spatial Learning in Teens With Bulimia Nervosa. J Am Acad Child Adolesc Psychiatry 2016; 55:962-971.e3. [PMID: 27806864 PMCID: PMC5098471 DOI: 10.1016/j.jaac.2016.07.778] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 06/07/2016] [Accepted: 08/31/2016] [Indexed: 12/17/2022]
Abstract
OBJECTIVE To assess the functioning of mesolimbic and fronto-striatal areas involved in reward-based spatial learning in teenaged girls with bulimia nervosa (BN) that might be involved in the development and maintenance of maladaptive behaviors characteristic of the disorder. METHOD We compared functional magnetic resonance imaging blood oxygen level-dependent response in 27 adolescent girls with BN to that of 27 healthy, age-matched control participants during a reward-based learning task that required learning to use extra-maze cues to navigate a virtual 8-arm radial maze to find hidden rewards. We compared groups in their patterns of brain activation associated with reward-based spatial learning versus a control condition in which rewards were unexpected because they were allotted pseudo-randomly to experimentally prevent learning. RESULTS Both groups learned to navigate the maze to find hidden rewards, but group differences in brain activity associated with maze navigation and reward processing were detected in the fronto-striatal regions and right anterior hippocampus. Unlike healthy adolescents, those with BN did not engage the right inferior frontal gyrus during maze navigation, activated the right anterior hippocampus during the receipt of unexpected rewards (control condition), and deactivated the left superior frontal gyrus and right anterior hippocampus during expected reward receipt (learning condition). These patterns of hippocampal activation in the control condition were significantly associated with the frequency of binge-eating episodes. CONCLUSION Adolescents with BN displayed abnormal functioning of the anterior hippocampus and fronto-striatal regions during reward-based spatial learning. These findings suggest that an imbalance in control and reward circuits may arise early in the course of BN. Clinical trial registration information-An fMRI Study of Self-Regulation in Adolescents With Bulimia Nervosa; https://clinicaltrials.gov/; NCT00345943.
Collapse
|
8
|
Striatal Activity and Reward Relativity: Neural Signals Encoding Dynamic Outcome Valuation. eNeuro 2016; 3:eN-NWR-0022-16. [PMID: 27822506 PMCID: PMC5089537 DOI: 10.1523/eneuro.0022-16.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 10/06/2016] [Accepted: 10/07/2016] [Indexed: 11/21/2022] Open
Abstract
The striatum is a key brain region involved in reward processing. Striatal activity has been linked to encoding reward magnitude and integrating diverse reward outcome information. Recent work has supported the involvement of striatum in the valuation of outcomes. The present work extends this idea by examining striatal activity during dynamic shifts in value that include different levels and directions of magnitude disparity. A novel task was used to produce diverse relative reward effects on a chain of instrumental action. Rats (Rattus norvegicus) were trained to respond to cues associated with specific outcomes varying by food pellet magnitude. Animals were exposed to single-outcome sessions followed by mixed-outcome sessions, and neural activity was compared among identical outcome trials from the different behavioral contexts. Results recording striatal activity show that neural responses to different task elements reflect incentive contrast as well as other relative effects that involve generalization between outcomes or possible influences of outcome variety. The activity that was most prevalent was linked to food consumption and post-food consumption periods. Relative encoding was sensitive to magnitude disparity. A within-session analysis showed strong contrast effects that were dependent upon the outcome received in the immediately preceding trial. Significantly higher numbers of responses were found in ventral striatum linked to relative outcome effects. Our results support the idea that relative value can incorporate diverse relationships, including comparisons from specific individual outcomes to general behavioral contexts. The striatum contains these diverse relative processes, possibly enabling both a higher information yield concerning value shifts and a greater behavioral flexibility.
Collapse
|
9
|
Xiao X, Dong Q, Chen C, Xue G. Neural pattern similarity underlies the mnemonic advantages for living words. Cortex 2016; 79:99-111. [DOI: 10.1016/j.cortex.2016.03.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 01/08/2016] [Accepted: 03/16/2016] [Indexed: 12/14/2022]
|
10
|
Westermann J, Lange T, Textor J, Born J. System Consolidation During Sleep – A Common Principle Underlying Psychological and Immunological Memory Formation. Trends Neurosci 2015; 38:585-597. [DOI: 10.1016/j.tins.2015.07.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 06/30/2015] [Accepted: 07/28/2015] [Indexed: 12/11/2022]
|
11
|
Mizumori SJY, Tryon VL. Integrative hippocampal and decision-making neurocircuitry during goal-relevant predictions and encoding. PROGRESS IN BRAIN RESEARCH 2015; 219:217-42. [PMID: 26072241 DOI: 10.1016/bs.pbr.2015.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
It has become clear that the hippocampus plays a critical role in the identification of new contexts and for the detection of changes in familiar contexts. The hippocampus accomplishes these goals through a continual process of comparing predicted features of a context or situation to those actually experienced. A mismatch between expected and experienced context expectations is thought to lead to the generation of a context prediction error (Mizumori, 2013) that functionally alerts connected brain areas to alter subsequent decision making and response selection. Little is understood about how hippocampal context analyses impact downstream decision processes. This issue is evaluated here first by comparing the nature of the information represented in hippocampus and decision-related midbrain-striatal structures, while rats perform a hippocampal-dependent spatial memory task in which rewards of different value are found at different locations. In contrast to place-specific and egocentric neural representations, neural representations of goal information are broadly distributed in hippocampal and decision neural circuitry, but they appear in different forms for different brain structures. It is suggested that further researching on how goal information processing occurs in hippocampus and decision neural circuitry may reveal insights into the nature of the interaction between memory and decision systems. The second part of this review describes neural pathways by which hippocampal context information might arrive within the decision circuit. The third section presents a hypothesis that the nature of the interactions between hippocampal and midbrain-striatal circuitry is regulated by the prefrontal cortex.
Collapse
Affiliation(s)
| | - Valerie L Tryon
- Psychology Department, University of Washington, Seattle, WA, USA
| |
Collapse
|
12
|
Werlen E, Jones MW. Modulating the map: dopaminergic tuning of hippocampal spatial coding and interactions. PROGRESS IN BRAIN RESEARCH 2015; 219:187-216. [PMID: 26072240 DOI: 10.1016/bs.pbr.2015.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Salient events activate the midbrain dopaminergic system and have important impacts on various aspects of mnemonic function, including the stability of hippocampus-dependent memories. Dopamine is also central to modulation of neocortical memory processing, particularly during prefrontal cortex-dependent working memory. Here, we review the current state of the circuitry and physiology underlying dopamine's actions, suggesting that--alongside local effects within hippocampus and prefrontal cortex--dopamine released from the midbrain ventral tegmental area is well positioned to dynamically tune interactions between limbic-cortical circuits through modulation of rhythmic network activity.
Collapse
Affiliation(s)
- Emilie Werlen
- School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, UK.
| | - Matthew W Jones
- School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, UK
| |
Collapse
|
13
|
Zucker HR, Ranganath C. Navigating the human hippocampus without a GPS. Hippocampus 2015; 25:697-703. [DOI: 10.1002/hipo.22447] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 03/17/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Halle R. Zucker
- Center for Neuroscience and Department of Psychology; University of California at Davis; California
| | - Charan Ranganath
- Center for Neuroscience and Department of Psychology; University of California at Davis; California
| |
Collapse
|
14
|
Affiliation(s)
- Laura A Ewell
- Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA
| | - Stefan Leutgeb
- 1] Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA [2] Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, California, USA
| |
Collapse
|
15
|
Functional heterogeneity of the limbic thalamus: From hippocampal to cortical functions. Neurosci Biobehav Rev 2014; 54:120-30. [PMID: 25446945 DOI: 10.1016/j.neubiorev.2014.11.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/22/2014] [Accepted: 11/12/2014] [Indexed: 12/31/2022]
Abstract
Today, the idea that the integrity of the limbic thalamus is necessary for normal memory functions is well established. However, if the study of thalamic patients emphasized the anterior and the mediodorsal thalamus as the critical thalamic loci supporting cognitive functions, clinical studies have so far failed to attribute a specific role to each of these regions. In view of these difficulties, we review here the experimental data conducted in rodents harboring specific lesions of each thalamic region. These data clearly indicate a major functional dissociation within the limbic thalamus. The anterior thalamus provides critical support for hippocampal functions due to its cardinal location in the Papez circuit, while the mediodorsal thalamus may signal relevant information in a circuit encompassing the basolateral amygdala and the prefrontal cortex. Interestingly, while clinical studies have suggested that diencephalic pathologies may disconnect the medial temporal lobe from the cortex, experimental studies conducted in rodent show how this may differently affect distinct temporo-thalamo-cortical circuits, sharing the same general organization but supporting dissociable functions.
Collapse
|
16
|
Clewett DV, Mather M. Not all that glittered is gold: neural mechanisms that determine when reward will enhance or impair memory. Front Neurosci 2014; 8:194. [PMID: 25076871 PMCID: PMC4099934 DOI: 10.3389/fnins.2014.00194] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 06/21/2014] [Indexed: 11/13/2022] Open
Affiliation(s)
- David V Clewett
- Neuroscience Graduate Program, University of Southern California Los Angeles, CA, USA
| | - Mara Mather
- Neuroscience Graduate Program, University of Southern California Los Angeles, CA, USA ; Davis School of Gerontology, University of Southern California Los Angeles, CA, USA ; Psychology Department, University of Southern California Los Angeles, CA, USA
| |
Collapse
|
17
|
Redila V, Kinzel C, Jo YS, Puryear CB, Mizumori SJY. A role for the lateral dorsal tegmentum in memory and decision neural circuitry. Neurobiol Learn Mem 2014; 117:93-108. [PMID: 24910282 DOI: 10.1016/j.nlm.2014.05.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 05/24/2014] [Accepted: 05/27/2014] [Indexed: 12/11/2022]
Abstract
A role for the hippocampus in memory is clear, although the mechanism for its contribution remains a matter of debate. Converging evidence suggests that hippocampus evaluates the extent to which context-defining features of events occur as expected. The consequence of mismatches, or prediction error, signals from hippocampus is discussed in terms of its impact on neural circuitry that evaluates the significance of prediction errors: Ventral tegmental area (VTA) dopamine cells burst fire to rewards or cues that predict rewards (Schultz, Dayan, & Montague, 1997). Although the lateral dorsal tegmentum (LDTg) importantly controls dopamine cell burst firing (Lodge & Grace, 2006) the behavioral significance of the LDTg control is not known. Therefore, we evaluated LDTg functional activity as rats performed a spatial memory task that generates task-dependent reward codes in VTA (Jo, Lee, & Mizumori, 2013; Puryear, Kim, & Mizumori, 2010) and another VTA afferent, the pedunculopontine nucleus (PPTg, Norton, Jo, Clark, Taylor, & Mizumori, 2011). Reversible inactivation of the LDTg significantly impaired choice accuracy. LDTg neurons coded primarily egocentric information in the form of movement velocity, turning behaviors, and behaviors leading up to expected reward locations. A subset of the velocity-tuned LDTg cells also showed high frequency bursts shortly before or after reward encounters, after which they showed tonic elevated firing during consumption of small, but not large, rewards. Cells that fired before reward encounters showed stronger correlations with velocity as rats moved toward, rather than away from, rewarded sites. LDTg neural activity was more strongly regulated by egocentric behaviors than that observed for PPTg or VTA cells that were recorded by Puryear et al. and Norton et al. While PPTg activity was uniquely sensitive to ongoing sensory input, all three regions encoded reward magnitude (although in different ways), reward expectation, and reward encounters. Only VTA encoded reward prediction errors. LDTg may inform VTA about learned goal-directed movement that reflects the current motivational state, and this in turn may guide VTA determination of expected subjective goal values. When combined it is clear the LDTg and PPTg provide only a portion of the information that dopamine cells need to assess the value of prediction errors, a process that is essential to future adaptive decisions and switches of cognitive (i.e. memorial) strategies and behavioral responses.
Collapse
Affiliation(s)
- Van Redila
- Department of Psychology, Box 351525, University of Washington, Seattle, WA 98195, USA
| | - Chantelle Kinzel
- Department of Psychology, Box 351525, University of Washington, Seattle, WA 98195, USA
| | - Yong Sang Jo
- Department of Psychology, Box 351525, University of Washington, Seattle, WA 98195, USA
| | - Corey B Puryear
- Department of Psychology, Box 351525, University of Washington, Seattle, WA 98195, USA
| | - Sheri J Y Mizumori
- Department of Psychology, Box 351525, University of Washington, Seattle, WA 98195, USA; Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA.
| |
Collapse
|
18
|
The form and function of hippocampal context representations. Neurosci Biobehav Rev 2014; 40:52-61. [PMID: 24462752 DOI: 10.1016/j.neubiorev.2014.01.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 12/09/2013] [Accepted: 01/14/2014] [Indexed: 01/09/2023]
Abstract
Context is an essential component of learning and memory processes, and the hippocampus is critical for encoding contextual information. However, connecting hippocampal physiology with its role in context and memory has only recently become possible. It is now clear that contexts are represented by coherent ensembles of hippocampal neurons and new optogenetic stimulation studies indicate that activity in these ensembles can trigger the retrieval of context appropriate memories. We interpret these findings in the light of recent evidence that the hippocampus is critically involved in using contextual information to prevent interference, and propose a theoretical framework for understanding contextual influence on memory retrieval. When a new context is encountered, a unique hippocampal ensemble is recruited to represent it. Memories for events that occur in the context become associated with the hippocampal representation. Revisiting the context causes the hippocampal context code to be re-expressed and the relevant memories are primed. As a result, retrieval of appropriate memories is enhanced and interference from memories belonging to other contexts is minimized.
Collapse
|