PET studies of encoding and retrieval: The HERA model

Neuroscientist's Behavioral Toolbox for Studying Episodic-Like Memory

Episodic memory, the ability to recall specific events and experiences, is a cornerstone of human cognition with profound clinical implications. While animal studies have provided valuable insights into the neuronal underpinnings of episodic memory, research has largely relied on a limited subset of tasks that model only some aspects of episodic memory. In this narrative review, we provide an overview of rodent episodic-like memory tasks that expand the methodological repertoire and diversify the approaches used in episodic-like memory research. These tasks assess various aspects of human episodic memory, such as integrated what-where-when or what-where memory, source memory, free recall, temporal binding, and threshold retrieval dynamics. We review each task's general principle and consider whether alternative non-episodic mechanisms can account for the observed behavior. While our list of tasks is not exhaustive, we hope it will guide researchers in selecting models that align with their specific research objectives, leading to novel advancements and a more comprehensive understanding of mechanisms underlying specific aspects of episodic memory.

Registered report: Age-preserved semantic memory and the CRUNCH effect manifested as differential semantic control networks: An fMRI study

Semantic memory representations are generally well maintained in aging, whereas semantic control is thought to be more affected. To explain this phenomenon, this study tested the predictions of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH), focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study compares 39 younger (20-35 years old) with 39 older participants (60-75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating task demand levels (low versus high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) were expected in younger versus older participants in the low- versus high-demand conditions, which should be manifested in semantic control Regions of Interest (ROIs). Our older participants had intact behavioral performance, as proposed in the literature for semantic memory tasks (maintained accuracy and slower response times (RTs)). Age-invariant behavioral performance in the older group compared to the younger one is necessary to test the CRUNCH predictions. The older adults were also characterized by high cognitive reserve, as our neuropsychological tests showed. Our behavioral results confirmed that our task successfully manipulated task demands: error rates, RTs and perceived difficulty increased with increasing task demands in both age groups. We did not find an interaction between age group and task demand, or a statistically significant difference in activation between the low- and high-demand conditions for either RTs or accuracy. As for brain activation, we did not find the expected age group by task demand interaction, or a significant main effect of task demand. Overall, our results are compatible with some neural activation in the semantic network and the semantic control network, largely in frontotemporoparietal regions. ROI analyses demonstrated significant effects (but no interactions) of task demand in the left and right inferior frontal gyrus, the left posterior middle temporal gyrus, the posterior inferior temporal gyrus and the prefrontal gyrus. Overall, our test did not confirm the CRUNCH predictions.

Brain representations of space and time in episodic memory: A systematic review and meta-analysis

All experiences preserved within episodic memory contain information on the space and time of events. The hippocampus is the main brain region involved in processing spatial and temporal information for incorporation within episodic memory representations. However, the other brain regions involved in the encoding and retrieval of spatial and temporal information within episodic memory are unclear, because a systematic review of related studies is lacking and the findings are scattered. The present study was designed to integrate the results of functional magnetic resonance imaging and positron emission tomography studies by means of a systematic review and meta-analysis to provide converging evidence. In particular, we focused on identifying the brain regions involved in the retrieval of spatial and temporal information. We identified a spatial retrieval network consisting of the inferior temporal gyrus, parahippocampal gyrus, superior parietal lobule, angular gyrus, and precuneus. Temporal context retrieval was supported by the dorsolateral prefrontal cortex. Thus, the retrieval of spatial and temporal information is supported by different brain regions, highlighting their different natures within episodic memory.

The knowledge domain of cognitive neuroscience of aging: A Scientometric and bibliometric analysis

Cognitive neuroscience of aging (CNA) is a relatively young field compared with other branches of cognitive aging (CA). From the beginning of this century, scholars in CNA have contributed many valuable research to explain the cognitive ability decline in aging brains in terms of functional changes, neuromechanism, and neurodegenerative diseases. However, very few studies have systematically reviewed the research in the domain of CAN, with regard to its primary research topics, theories, findings, and future development. Therefore, this study used CiteSpace to conduct a bibliometric analysis of 1,462 published articles in CNA from Web of Science (WOS) and investigated the highly influential and potential research topics and theories of CNA, as well as important brain areas involved in CAN during 2000-2021. The results revealed that: (1) the research topics of "memory" and "attention" have been the focus of most studies, progressing into a fMRI-oriented stage; (2) the scaffolding theory and hemispheric asymmetry reduction in older adults model hold a key status in CNA, characterizing aging as a dynamic process and presenting compensatory relationships between different brain areas; and (3) age-related changes always occur in temporal (especially the hippocampus), parietal, and frontal lobes and the cognitive declines establish the compensation relationship between the anterior and posterior regions.

Opposite pattern of transcranial direct current stimulation effects in middle-aged and older adults: Behavioral and neurophysiological evidence

Introduction

Episodic memory (EM) exhibits an age-related decline, with overall increased impairment after the age of 65. The application of transcranial direct current stimulation (tDCS) to ameliorate cognitive decline in ageing has been extensively investigated, but its efficacy has been reported with mixed results. In this study, we aimed to assess whether age contributes to interindividual variability in tDCS efficacy.

Methods

Thirty-eight healthy adults between 50 and 81 years old received anodal tDCS over the left prefrontal cortex during images encoding and then performed an EM recognition task while event-related potentials (ERPs) were recorded.

Results

Our results showed an opposite pattern of effect between middle-aged (50-64 years) and older (65-81 years) adults. Specifically, performance in the recognition task after tDCS was enhanced in older adults and was worsened in middle-aged adults. Moreover, ERPs acquired during the recognition task showed that two EM components related to familiarity and post-retrieval monitoring, i.e., Early Frontal and Late Frontal Old-New effects, respectively, were significantly reduced in middle-aged adults after anodal tDCS.

Discussion

These results support an age-dependent effect of prefrontal tDCS on EM processes and its underlying electrophysiological substrate, with opposing modulatory trajectories along the aging lifespan.

Effects of saccadic eye movements on episodic & semantic memory fluency in older and younger participants

Research has demonstrated that performing a sequence of saccadic horizontal eye movements prior to retrieval facilitates performance on tests of episodic memory. This has been observed in both laboratory tasks of retention and autobiographical memory. To date, the work has centred on performance in younger individuals. This paper extends previous investigations by examining the effects of saccadic eye movements in older persons. Autobiographical episodic and semantic memory fluency was assessed in younger (age range 18-35, mean = 22.50), and older (age range 55-87, mean = 70.35) participants following saccadic (vs. fixation control) manipulations. The main effects of eye movements and age were found for episodic autobiographical memory (greater fluency after eye movements and in younger participants). Semantic autobiographical memory showed a main effect of age (greater fluency in younger participants), whereas general semantic memory showed no effect of age or eye movement. These findings indicate that saccadic horizontal eye movements can enhance episodic personal memory in older individuals. This has implications as a technique to improve autobiographical recollection in the elderly and as an adjunct in reminiscence therapy.

Brain structural network to investigate the mechanism of cognitive impairment in patients with acoustic neuroma

Objective

Acoustic neuroma (AN) is a common benign tumor. Little is known of neuropsychological studies in patients with acoustic neuroma, especially cognitive neuropsychology, and the neuropsychological abnormalities of patients affect their life quality. The purpose of this study was to explore the changes in the cognitive function of patients with acoustic neuroma, and the possible mechanism of these changes by structural magnetic resonance imaging.

Materials and methods

We used a neuropsychological assessment battery to assess cognitive function in 69 patients with acoustic neuroma and 70 healthy controls. Then, we used diffusion tensor imaging data to construct the structural brain network and calculate topological properties based on graph theory, and we studied the relation between the structural brain network and cognitive function. Moreover, three different subnetworks (short-range subnetwork, middle-range subnetwork, and long-range subnetwork) were constructed by the length of nerve fibers obtained from deterministic tracking. We studied the global and local efficiency of various subnetworks and analyzed the correlation between network metrics and cognitive function. Furthermore, connectome edge analysis directly assessed whether there were differences in the number of fibers in the different brain regions. We analyzed the relation between the differences and cognitive function.

Results

Compared with the healthy controls, the general cognitive function, memory, executive function, attention, visual space executive ability, visual perception ability, movement speed, and information processing speed decreased significantly in patients with acoustic neuroma. A unilateral hearing loss due to a left acoustic neuroma had a greater impact on cognitive function. The results showed that changes in the global and local metrics, the efficiency of subnetworks, and cognitively-related fiber connections were associated with cognitive impairments in patients with acoustic neuroma.

Conclusion

Patients exhibit cognitive impairments caused by the decline of the structure and function in some brain regions, and they also develop partial compensation after cognitive decline. Cognitive problems are frequent in patients with acoustic neuroma. Including neuropsychological aspects in the routine clinical evaluation and appropriate treatments may enhance the clinical management and improve their life quality.

Research on the Mechanism of Cognitive Decline in Patients With Acoustic Neuroma

Little is known about neuropsychological research on patients with acoustic neuroma (AN), especially cognitive neuropsychology. We aim to compare the cognitive function of patients with AN and healthy controls (HCs) and explore possible underlying mechanisms. Various neuropsychological assessments were performed on all participants. Tract-based spatial statistics (TBSS) was used to compare DTI metrics such as fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD). Correlation analysis was analyzed between DTI metrics and cognitive scales. Compared with the HC group, the AN group performed worse in the neuropsychological evaluations, and TBSS analysis showed widespread alteration of the FA, AD, RD, and MD, which correlated with the cognitive function. These white matter tracts include minor forceps, major forceps, anterior thalamic radiation, superior longitudinal fasciculus, corticospinal tract, and right inferior fronto-occipital fasciculus. Meanwhile, we found for the first time that cognitive decline was related to the decrease of FA in minor forceps, which can be used as a neurobiological marker of cognitive impairment in patients with AN. The occurrence of cognition impairment is common in patients with AN. Including neuropsychological evaluation in the routine clinical assessment and appropriate treatment may strengthen clinical management and improve the quality of life of patients.

Language as the Working Model of Human Mind

The Human Mind, functional aspect of Human Brain, has been envisaged to be working on the tenets of Chaos, a seeming order within a disorder, the premise of Universe. The armamentarium of Human Mind makes use of distributed neuronal networks sub-serving Sensorial Mechanisms, Mirror Neurone System (MNS) and Motor Mechanisms etching a stochastic trajectory on the virtual phase-space of Human Mind, obeying the ethos of Chaos. The informational sensorial mechanisms recruit attentional mechanisms channelising through the window of chaotic neural dynamics onto MNS that providing algorithmic image information flow along virtual phase- space coordinates concluding onto motor mechanisms that generates and mirrors a stimulus- specific and stimulus-adequate response. The singularity of self-iterating fractal architectonics of Event-Related Synchrony (ERS), a Power Spectral Density (PSD) precept of electroencephalographic (EEG) time-series denotes preferential and categorical inhibition gateway and an Event-Related Desynchrony (ERD) represents event related and locked gateway to stimulatory/excitatory neuronal architectonics leading to stimulus-locked and adequate neural response. The contextual inference in relation to stochastic phase-space trajectory of self- iterating fractal of Off-Center α ERS (Central)-On-Surround α ERD-On Surround θ ERS document efficient neural dynamics of working memory., across patterned modulation and flow of the neurally coded information.

Level of processing's effect on episodic retrieval following traumatic brain injury in the elderly: An event-related potential study

Individuals who have sustained a traumatic brain injury (TBI) can suffer from episodic memory impairments. Until now, the neural correlates underlying episodic retrieval in individuals with TBI remained scarce, particularly in older adults. We aimed to fill this gap by recording event-related potentials during an old/new episodic recognition task in 26 older adults, 13 healthy and 13 with TBI. The task manipulated the level of processing in encoding with the use of semantic organizational strategies (deep guided, deep self-guided, and shallow encoding). For all encoding conditions, behavioral data analyses on the discrimination rate indicated that older adults with TBI were globally impaired compared with healthy older adults. The electrophysiological results indicated that the left-parietal effect was larger in the deep guided condition than in the shallow condition. In addition, the results show that the mid-frontal and left-parietal positive old/new effects were absent in both groups. The main findings are the observation, in the control group only, of an early frontal old/new effect (P200; 150-300 ms) and of a late frontal old/new effect on the left hemisphere, only in the Spontaneous condition. Together, results suggest an impairment of the allocation of attentional resources and working memory necessary for retrieving and monitoring items in the elderly with TBI.

Using transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex to promote long-term foreign language vocabulary learning

Transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex (DLPFC) was used to improve foreign-langue learning while using mental imagery. Participants underwent two sessions of 1 mA, 1.5 mA, or sham stimulation prior to learning Swahili-English word pairs two consecutive days. During learning, participants were encouraged to create a mental image of the associated English word. Twenty-four hours after learning and one week later, participants received a cued recall test. A linear dose-response effect of stimulation was found across both tests that occurred long after the immediate effects of stimulation. Follow-up comparisons revealed that only the 1.5 mA condition differed from the sham group. Exploratory moderating effects revealed interactions with sleep quality and handedness. Those with poorer sleep and who were left-handed showed greater recall after 1.5 mA of stimulation than those with better sleep and right-handers. A follow-up behavioral study probing strategy usage indicated that mental imagery strategy use did not strongly impact learning but point to other possible mechanisms including the importance of attending to multimodal perceptual details and memory consolidation. This preliminary evidence supports the role of the DLPFC or connected regions in foreign language vocabulary learning and verbal memory encoding.

The Quest for Hemispheric Asymmetries Supporting and Predicting Executive Functioning

This narrative review addresses the neural bases of two executive functions: criterion setting, that is, the capacity to flexibly set up and select task rules and associations between stimuli, responses, and nonresponses, and monitoring, that is, the process of continuously evaluating whether task rules are being applied optimally. There is a documented tendency for criterion setting and monitoring to differentially recruit left and right lateral prefrontal regions and connected networks, respectively, above and beyond the specific task context. This model, known as the ROtman-Baycrest Battery to Investigate Attention (ROBBIA) model, initially sprung from extensive neuropsychological work led by Don Stuss. In subsequent years, multimodal lines of empirical investigation on both healthy individuals and patients with brain damage, coming from functional neuroimaging, EEG, neurostimulation, individual difference approaches, and, again, neuropsychology, so to "complete the circle," corroborated the functional mapping across the two hemispheres as predicted by the model. More recent electrophysiological evidence has further shown that hemispheric differences in intrinsic prefrontal dynamics are able to predict cognitive performance in tasks tapping these domain-general functions. These empirical contributions will be presented together with contrasting evidence, limits, and possible future directions to better fine-tune this model and extend its scope to new fields.

Age-preserved semantic memory and the CRUNCH effect manifested as differential semantic control networks: An fMRI study

Semantic memory representations are overall well-maintained in aging whereas semantic control is thought to be more affected. To explain this phenomenon, this study aims to test the predictions of the Compensation Related Utilization of Neural Circuits Hypothesis (CRUNCH) focusing on task demands in aging as a possible framework. The CRUNCH effect would manifest itself in semantic tasks through a compensatory increase in neural activation in semantic control network regions but only up to a certain threshold of task demands. This study will compare 40 young (20-35 years old) with 40 older participants (60-75 years old) in a triad-based semantic judgment task performed in an fMRI scanner while manipulating levels of task demands (low vs. high) through semantic distance. In line with the CRUNCH predictions, differences in neurofunctional activation and behavioral performance (accuracy and response times) are expected in young vs. old participants in the low- vs. high-demand conditions manifested in semantic control Regions of Interest.

Age-Related Differences in Functional Asymmetry During Memory Retrieval Revisited: No Evidence for Contralateral Overactivation or Compensation

Brain asymmetry is inherent to cognitive processing and seems to reflect processing efficiency. Lower frontal asymmetry is often observed in older adults during memory retrieval, yet it is unclear whether lower asymmetry implies an age-related increase in contralateral recruitment, whether less asymmetry reflects compensation, is limited to frontal regions, or predicts neurocognitive stability or decline. We assessed age-related differences in asymmetry across the entire cerebral cortex, using functional magnetic resonance imaging data from 89 young and 76 older adults during successful retrieval, and surface-based methods allowing direct homotopic comparison of activity between cortical hemispheres . An extensive left-asymmetric network facilitated retrieval in both young and older adults, whereas diverse frontal and parietal regions exhibited lower asymmetry in older adults. However, lower asymmetry was not associated with age-related increases in contralateral recruitment but primarily reflected either less deactivation in contralateral regions reliably signaling retrieval failure in the young or lower recruitment of the dominant hemisphere-suggesting that functional deficits may drive lower asymmetry in older brains, not compensatory activity. Lower asymmetry predicted neither current memory performance nor the extent of memory change across the preceding ~ 8 years in older adults. Together, these findings are inconsistent with a compensation account for lower asymmetry during retrieval and aging.

Examining the effects of transcranial direct current stimulation on human episodic memory with machine learning

We aimed to replicate a published effect of transcranial direct-current stimulation (tDCS)-induced recognition enhancement over the human ventrolateral prefrontal cortex (VLPFC) and analyse the data with machine learning. We investigated effects over an adjacent region, the dorsolateral prefrontal cortex (DLPFC). In total, we analyzed data from 97 participants after exclusions. We found weak or absent effects over the VLPFC and DLPFC. We conducted machine learning studies to examine the effects of semantic and phonetic features on memorization, which revealed no effect of VLPFC tDCS on the original dataset or the current data. The highest contributing factor to memory performance was individual differences in memory not explained by word features, tDCS group, or sample size, while semantic, phonetic, and orthographic word characteristics did not contribute significantly. To our knowledge, this is the first tDCS study to investigate cognitive effects with machine learning, and future studies may benefit from studying physiological as well as cognitive effects with data-driven approaches and computational models.

Hemispheric Asymmetries in Electroencephalogram Oscillations for Long-Term Memory Retrieval in Healthy Individuals

The hemispherical encoding retrieval asymmetry (HERA) model, established in 1991, suggests that the involvement of the right prefrontal cortex (PFC) in the encoding process is less than that of the left PFC. The HERA model was previously validated for episodic memory in subjects with brain traumas or injuries. In this study, a revised HERA model is used to investigate long-term memory retrieval from newly learned video-based content for healthy individuals using electroencephalography. The model was tested for long-term memory retrieval in two retrieval sessions: (1) recent long-term memory (recorded 30 min after learning) and (2) remote long-term memory (recorded two months after learning). The results show that long-term memory retrieval in healthy individuals for the frontal region (theta and delta band) satisfies the revised HERA asymmetry model.

Biological and environmental predictors of heterogeneity in neurocognitive ageing: Evidence from Betula and other longitudinal studies

Individual differences in cognitive performance increase with advancing age, reflecting marked cognitive changes in some individuals along with little or no change in others. Genetic and lifestyle factors are assumed to influence cognitive performance in ageing by affecting the magnitude and extent of age-related brain changes (i.e., brain maintenance or atrophy), as well as the ability to recruit compensatory processes. The purpose of this review is to present findings from the Betula study and other longitudinal studies, with a focus on clarifying the role of key biological and environmental factors assumed to underlie individual differences in brain and cognitive ageing. We discuss the vital importance of sampling, analytic methods, consideration of non-ignorable dropout, and related issues for valid conclusions on factors that influence healthy neurocognitive ageing.

An historical perspective on Endel Tulving's episodic-semantic distinction

The distinction between episodic and semantic memory, proposed by Endel Tulving in 1972, remains a key concept in contemporary Cognitive Neuroscience. Here we review how this distinction evolved in Tulving's writings over the years. Crucially, from 1972 onward, he argued that the two forms of memory were inter-dependent and that their interaction was an essential feature of normal episodic memory function. Moreover, later elaborations of the theory clearly proposed that these interactions formed the basis of normal declarative memory functioning. A later but crucial aspect of Tulving's contribution was his stress on the importance of subjective experience, which, according to him, "should be the ultimate object of interest, the central aspect of remembering that is to be explained and understood". We relate these and his numerous other ideas to current perspectives about the organization and function of human memory.

Re-evaluating whether bilateral eye movements influence memory retrieval

Several recent studies have reported enhanced memory when retrieval is preceded by repetitive horizontal eye movements, relative to vertical or no eye movements. The reported memory boost has been referred to as the Saccade-Induced Retrieval Enhancement (SIRE) effect. Across two experiments, memory performance was compared following repetitive horizontal or vertical eye movements, as well as following a control condition of no eye movements. In Experiment 1, we conceptually replicated Christman and colleagues’ seminal study, finding a statistically significant SIRE effect, albeit with weak Bayesian evidence. We therefore sought to conduct another close extension. In Experiment 2, horizontal and vertical eye movement conditions were manipulated separately, and sample size was increased. No evidence of a SIRE effect was found: Bayesian statistical analyses demonstrated significant evidence for a null effect. Taken together, these experiments suggest that the SIRE effect is inconsistent. The current experiments call into question the generalizability of the SIRE effect and suggest that its presence is very sensitive to experimental design. Future work should further assess the robustness of the effect before exploring related theories or underlying mechanisms.

Precision, binding, and the hippocampus: Precisely what are we talking about?

Endel Tulving's proposal that episodic memory is distinct from other memory systems like semantic memory remains an extremely influential idea in cognitive neuroscience research. As originally suggested by Tulving, episodic memory involves three key components that differentiate it from all other memory systems: spatiotemporal binding, mental time travel, and autonoetic consciousness. Here, we focus on the idea of spatiotemporal binding in episodic memory and, in particular, how consideration of the precision of spatiotemporal context helps expand our understanding of episodic memory. Precision also helps shed light on another key issue in cognitive neuroscience, the role of the hippocampus outside of episodic memory in perception, attention, and working memory. By considering precision alongside item-context bindings, we attempt to shed new light on both the nature of how we represent context and what roles the hippocampus plays in episodic memory and beyond.

Longitudinal evidence that reduced hemispheric encoding/retrieval asymmetry predicts episodic-memory impairment in aging

The HERA (Hemispheric Encoding/Retrieval Asymmetry) model captures hemispheric lateralization of prefrontal cortex (PFC) brain activity during memory encoding and retrieval. Reduced HERA has been observed in cross-sectional aging studies, but there is no longitudinal evidence, to our knowledge, on age-related changes in HERA and whether maintained or reduced HERA relates to well-preserved memory functioning. In the present study we set out to explore HERA in a longitudinal neuroimaging sample from the Betula study [3 Waves over 10 years; Wave-1: n = 363, W2: n = 227, W3: n = 101]. We used fMRI data from a face-name paired-associates task to derive a HERA index. In support of the HERA model, the mean HERA index was positive across the three imaging waves. The longitudinal age-HERA relationship was highly significant (p < 10^-11), with a HERA decline occurring after age 60. The age-related HERA decline was associated with episodic memory decline (p < 0.05). Taken together, the findings provide large-scale support for the HERA model, and suggest that reduced HERA in the PFC reflects pathological memory aging possibly related to impaired ability to bias mnemonic processing according to the appropriate encoding or retrieval state.

Resituating cognitive mechanisms within heterarchical networks controlling physiology and behavior

Cognitive science has traditionally focused on mechanisms involved in high-level reasoning and problem-solving processes. Such mechanisms are often treated as autonomous from but controlling underlying physiological processes. I offer a different perspective on cognition which starts with the basic production mechanisms through which organisms construct and repair themselves and navigate their environments and then I develop a framework for conceptualizing how cognitive control mechanisms form a heterarchical network that regulates production mechanisms. Many of these control mechanisms perform cognitive tasks such as evaluating circumstances and making decisions. Cognitive control mechanisms are present in individual cells, but in metazoans, intracellular control is supplemented by a nervous system in which a multitude of neural control mechanisms are organized heterarchically. On this perspective, high-level cognitive mechanisms are not autonomous, but are elements in larger heterarchical networks. This has implications for future directions in cognitive science research.

Sex, Age, and Handedness Modulate the Neural Correlates of Active Learning

BACKGROUND

Self-generation of material compared to passive learning results in mproved memory performance; this may be related to recruitment of a fronto-temporal encoding network. Using a verbal paired-associate learning fMRI task, we examined the effects of sex, age, and handedness on the neural correlates of self-generation.

METHODS

Data from 174 healthy English-speaking participants (78M, 56 atypically handed; ages 19-76) were preprocessed using AFNI and FSL. Independent component analysis was conducted using GIFT (Group ICA fMRI Toolbox). Forty-one independent components were temporally sorted by task time series. Retaining correlations (r > 0.25) resulted in three task-positive ("generate") and three task-negative ("read") components. Using participants' back-projected components, we evaluated the effects of sex, handedness, and aging on activation lateralization and localization in task-relevant networks with two-sample t-tests. Further, we examined the linear relationship between sex and neuroimaging data with multiple regression, covarying for scanner, age, and handedness.

RESULTS

Task-positive components identified using ICA revealed a fronto-parietal network involved with self-generation, while task-negative components reflecting passive reading showed temporo-occipital involvement. Compared to older adults, younger adults exhibited greater task-positive involvement of the left inferior frontal gyrus and insula, whereas older adults exhibited reduced prefrontal lateralization. Greater involvement of the left angular gyrus in task-positive encoding networks among right-handed individuals suggests the reliance on left dominant semantic processing areas may be modulated by handedness. Sex effects on task-related encoding networks while controlling for age and handedness suggest increased right hemisphere recruitment among males compared to females, specifically in the paracentral lobe during self-generation and the suparmarginal gyrus during passive reading.

IMPLICATIONS

Identified neuroimaging differences suggest that sex, age, and handedness are factors in the differential recruitment of encoding network regions for both passive and active learning.

Effects of backpack weight on the performance of basic short-term/working memory tasks during flat-surface standing

This study empirically investigated the effects of backpack weight on the performance of three basic short-term/working memory (STM/WM) tasks during flat-surface standing. Four levels of backpack weight were considered: 0, 15, 25 and 40% of the body weight. The three STM/WM tasks were the Corsi block, digit span and 3-back tasks, corresponding to the visuo-spatial sketchpad, phonological loop and central executive of WM, respectively. Thirty participants conducted the STM/WM tasks while standing with loaded backpack. Major study findings were that (1) increased backpack weight adversely affected the scores of all three STM/WM tasks; and, (2) the adverse effect of backpack weight was less pronounced for the phonological loop STM task than the other STM/WM tasks. The study findings may help understand and predict the impacts of body-worn equipment weight on the worker's mental task performance for various work activities requiring simultaneous performance of mental and physical tasks. Practitioner summary: The current study empirically examined the effects of backpack weight on the performance of three basic STM/WM tasks. The study findings entail that reduces the weight of body-worn equipment can positively impact the worker's mental task performance in addition to reducing the worker's bodily stresses. Abbreviations: ACC: anterior cingulate cortex; AP: anterior-posterior; BW: body weight; CoP: centre of pressure; C-S: central executive working memory task and standing; DLPFC: dorsolateral prefrontal cortex; HIP: human information processing; ML: medio-lateral; PMC: premotor cortex; P-S: phonological loop short-term memory task and standing; SMA: supplementary motor area; STM: short-term memory; VLPFC: ventrolateral prefrontal cortex; V-S: visuo-spatial short-term memory task and standing; WM: working memory.

Recognition-induced forgetting does not occur for temporally grouped objects unless they are semantically related

Recent evidence has shown that practice recognizing certain objects hurts memories of objects from the same category, a phenomenon called recognition-induced forgetting. In all previous studies of this effect, the objects have been related by semantic category (e.g., instances of vases). However, the relationship between objects in many real-world visual situations stresses temporal grouping rather than semantic relations (e.g., a weapon and getaway car at a crime scene), and temporal grouping is thought to cluster items in models of long-term memory. The goal of the present study was to determine whether temporally grouped objects suffer recognition-induced forgetting. To this end, we implemented a modified recognition-induced forgetting paradigm in which the objects were temporally clustered at study. Across four experiments, we found that recognition-induced forgetting occurred only when the temporally clustered objects were also semantically related. We conclude by discussing how these findings relate to real-world vision and inform models of memory.

Association of cardiorespiratory fitness on interhemispheric hippocampal and parahippocampal functional connectivity

Interhemispheric functional connectivity is associated with cognitive functioning. Although previous work has evaluated the association of cardiorespiratory fitness on cognitive function, there has been a limited investigation of the association of cardiorespiratory fitness on the functional connectivity of memory-related brain structures. As such, the objective of this study was to examine the association between cardiorespiratory fitness and parahippocampal and hippocampal interhemispheric functional connectivity. Data from the Nathan Kline Institute-Rockland Sample (NKI-RS) were utilized. Our analysis consisted of 284 participants (M_age  = 43 years; 62% female). Cardiorespiratory fitness was objectively measured using a cycle ergometer protocol. Parahippocampal and hippocampal interhemispheric functional connectivity were assessed from fMRI. Higher cardiorespiratory fitness was associated with greater parahippocampal (β = 0.004; CI, 0.00009 to 0.008, p = 0.04), but not hippocampal (β = 0.001; CI, -0.002 to 0.005, p = 0.44) interhemispheric functional connectivity. In conclusion, enhanced cardiorespiratory fitness may facilitate parahippocampal interhemispheric functional connectivity.

Saccades and handedness interact to affect scene memory

Repetitive saccades benefit memory when executed before retrieval, with greatest effects for episodic memory in consistent-handers. Questions remain including how saccades affect scene memory, an important visual component of episodic memory. The present study tested how repetitive saccades affect working and recognition memory for novel scenes. Handedness direction (left–right) and degree (strong/consistent vs. mixed/inconsistent) was measured by raw and absolute laterality quotients respectively from an 8-question handedness inventory completed by 111 adults. Each then performed either 30 s of repetitive horizontal saccades or fixation before or after tasks of scene working memory and scene recognition. Regression with criterion variables of overall percent correct accuracy and d-prime sensitivity showed that when saccades were made before working memory, there was better overall accuracy as a function of increased direction but not degree of handedness. Subjects who made saccades before working memory also performed worse during subsequent recognition memory, while subjects who fixated or made saccades after the working memory task performed better. Saccades made before recognition resulted in recognition accuracy that was better (Cohen’s d = 0.3729), but not significantly different from fixation before recognition. The results demonstrate saccades and handedness interact to affect scene memory with larger effects on encoding than recognition. Saccades before scene encoding in working memory are detrimental to short- and long-term memory, especially for those who are not consistently right-handed, while saccade execution before scene recognition does not appear to benefit recognition accuracy. The findings are discussed with respect to theories of interhemispheric interaction and control of visuospatial attention.

Increased fMRI activity correlations in autobiographical memory versus resting states

Autobiographical memory retrieval is associated with activity of a distributed network that is similar to the default-mode network (DMN) identified via activity correlations measured during rest. We tested whether activity correlations could be used to identify the autobiographical network during extended bouts of retrieval. Global-correlativity analysis identified regions with activity correlation differences between autobiographical-retrieval and resting states. Increased correlations were identified for retrieval versus resting states within a distributed network that included regions prototypical for autobiographical memory. This network segregated into two subnetworks comprised of regions related to memory versus cognitive control, suggesting greater functional segregation during autobiographical retrieval than rest. DMN regions were important drivers of these effects, with increased correlations between DMN and non-DMN regions and segregation of the DMN into distinct subnetworks during retrieval. Thus, the autobiographical network can be robustly identified via activity correlations and retrieval is associated with network functional organization distinct from rest.

Exploring lateralization during memory through hemispheric pre-activation: Differences based on the stimulus type

The original approach of the Hemispheric Encoding/Retrieval Asymmetry model (HERA) was aimed at the operations of encoding and retrieving episodic memories. However, whether HERA presumptions can apply to different types of stimuli (e.g., words and pictures) continues to be a matter of debate. Therefore, in order to analyse the effects of brain pre-activation on subsequent memory, HERA was tested through a hand-clenching paradigm using four types of stimuli: words, fractal images, silhouettes of common objects, and pseudowords. Results revealed that only the memory of words and pseudowords was enhanced by hand-clenching pre-activation, according to HERA predictions. Since the cognitive processes underlying recognition of verbal stimuli are considered to follow a cognitive route involving grapheme-morpheme conversion, it could be hypothesized that hand-clenching pre-activation might be associated with a selective pre-activation of the brain circuits participating in that pathway. Hence, the present work broadens possible interpretations behind the effects of hand-clenching on memory, based on the process engaged and the type of stimulus to be remembered.

Interhemispheric Activation and Memory Function: Considerations and Recommendations in the Context of Cardiovascular Exercise Research

The field of neurobiology of learning and memory has demonstrated that interhemispheric activation plays an important role in subserving episodic memory function. A common behavioral technique to induce interhemispheric activation includes saccadic eye movements, with a common behavioral marker being the degree of handedness. Importantly, however, the field of exercise neurobiology has yet to consider these behavioral techniques and markers in exercise-based studies. This review highlights the effects of these techniques and markers on episodic memory function and discusses the implications of this for exercise studies. We discuss the physiological and neurological mechanisms of interhemispheric activation on memory. We also discuss the role this may play in cardiorespiratory exercise studies. Our understanding of the role of both exercise and interhemispheric activation on memory function is improving. The interplay between these two factors on memory, however, is unknown. We discuss these implications and provide recommendations for future research.

One is all you need: intrahemispheric processing benefits nonverbal visual recognition

Several attempts have been made to understand when and how the two hemispheres of the brain work together to encode and retrieve information during memory tasks, but it remains unclear whether they are equally capable of encoding and retrieval, particularly when the stimuli do not evoke a leftward processing asymmetry. Using a divided visual field paradigm, we presented nonverbal visual stimuli to one visual field/hemisphere at encoding, and at retrieval presented the stimuli either to the same or opposite visual field/hemisphere. Recognition responses were faster and more accurate when the stimuli were initially presented at encoding and retrieval to the same hemisphere (Experiment 1), even when delay intervals between study and test were short (Experiment 2). Taken together, these findings suggest that recognition decisions for stimuli initially presented to a single hemisphere occur more quickly at shorter lags, perhaps due to a stronger memory representation in the original hemisphere of input compared to the indirectly activated hemisphere. Our results are significant because they demonstrate that each hemisphere of the brain can function to encode and retrieve memory representations equally well, as long as the stimuli contain no linguistic information.

Brain Responses at Encoding Predict Limited Verbal Memory Retrieval by Persons with Schizophrenia

Objective

Special attention has been given to verbal memory deficits in schizophrenia because they are apparent in healthy biological relatives of affected individuals, indicating a link to genetic risk for the disorder. Despite a growing consensus that encoding abnormalities contribute to poor verbal memory in the disorder, few studies have directly examined how neural responses during encoding contribute to later memory performance.

Method

We evaluated event-related potentials (ERPs) during encoding of verbal material by patients with schizophrenia, healthy first-degree biological relatives of patients, and healthy controls. The extent to which N1, N400, and anterior and parietal Late Positive Components (LPCs) explained encoding accuracy and later memory of material was investigated.

Results

Encoding accuracy was associated with asymmetry in anterior LPCs toward right frontal brain regions and was most evident in relatives. N1 was abnormal at encoding in schizophrenia and differentially accounted for later memory performance. In controls better recall of verbal material was predicted by a larger early occipital (N1) encoding response; however, in patients with schizophrenia smaller N1 encoding responses were related to better recall. Interestingly, better recognition of verbal material across groups was also predicted by smaller N1 amplitudes during encoding of word stimuli.

Conclusion

Separable patterns of electrophysiological response during encoding appear to differentially support recall and recognition of material from memory. Similar patterns of electrophysiological response across patient and relative groups suggest that those who carry genetic liability for schizophrenia share deviations in the neural activity related to encoding of material into episodic memory.

Neural correlates of episodic memory in the Memento cohort

Introduction

The free and cued selective reminding test is used to identify memory deficits in mild cognitive impairment and demented patients. It allows assessing three processes: encoding, storage, and recollection of verbal episodic memory.

Methods

We investigated the neural correlates of these three memory processes in a large cohort study. The Memento cohort enrolled 2323 outpatients presenting either with subjective cognitive decline or mild cognitive impairment who underwent cognitive, structural MRI and, for a subset, fluorodeoxyglucose–positron emission tomography evaluations.

Results

Encoding was associated with a network including parietal and temporal cortices; storage was mainly associated with entorhinal and parahippocampal regions, bilaterally; retrieval was associated with a widespread network encompassing frontal regions.

Discussion

The neural correlates of episodic memory processes can be assessed in large and standardized cohorts of patients at risk for Alzheimer's disease. Their relation to pathophysiological markers of Alzheimer's disease remains to be studied.

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This is the largest cohort ever to be used in the study of the morpho-metabolic correlates of episodic memory in human, ensuring the validity of the obtained results.

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We found that encoding of information is linked to a posterior network previously evidenced to support working memory.

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The storage process was mainly supported in our study by medial temporal regions.

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Spontaneous retrieval of stimuli implicated broad neural networks including the frontal regions.

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These associations were particularly strong in APOE ε4 carriers suggesting that the free and selective reminding test is useful to detect Alzheimer's disease at an early stage.

Dietary inflammatory index and memory function: population-based national sample of elderly Americans

The objective of this study was to examine the association between dietary inflammatory potential and memory and cognitive functioning among a representative sample of the US older adult population. Cross-sectional data from the 2011-2012 and 2013-2014 National Health and Nutrition Examination Survey were utilised to identify an aggregate sample of adults 60-85 years of age (n 1723). Dietary inflammatory index (DII®) scores were calculated using 24-h dietary recall interviews. Three memory-related assessments were employed, including the Consortium to Establish a Registry for Alzheimer's disease (CERAD) Word Learning subset, the Animal Fluency test and the Digit Symbol Substitution Test (DSST). Inverse associations were observed between DII scores and the different memory parameters. Episodic memory (CERAD) (b adjusted=-0·39; 95 % CI -0·79, 0·00), semantic-based memory (Animal Fluency Test) (b adjusted=-1·18; 95 % CI -2·17, -0·20) and executive function and working-memory (DSST) (b adjusted=-2·80; 95 % CI -5·58, -0·02) performances were lowest among those with the highest mean DII score. Though inverse relationships were observed between DII scores and memory and cognitive functioning, future work is needed to further explore the neurobiological mechanisms underlying the complex relationship between inflammation-related dietary behaviour and memory and cognition.

Effects of Saccade Induced Retrieval Enhancement on conceptual and perceptual tests of explicit & implicit memory

The effects of saccadic horizontal (bilateral) eye movements upon tests of both conceptual and perceptual forms of explicit and implicit memory were investigated. Participants studied a list of words and were then assigned to one of four test conditions: conceptual explicit, conceptual implicit, perceptual explicit, or perceptual implicit. Conceptual tests comprised category labels with either explicit instructions to recall corresponding examples from the study phase (category-cued recall), or implicit instructions to generate any corresponding examples that spontaneously came to mind (category-exemplar generation). Perceptual tests comprised of word-fragments with either explicit instructions to complete these with study items (word-fragment-cued recall), or implicit instructions to complete each fragment with the first word that simply 'popped to mind' (word-fragment completion). Just prior to retrieval, participants were required to engage in 30 s of bilateral vs. no eye movements. Results revealed that saccadic horizontal eye movements enhanced performance in only the conceptual explicit condition, indicating that Saccade-Induced Retrieval Enhancement is a joint function of conceptual and explicit retrieval mechanisms. Findings are discussed from both a cognitive and neuropsychological perspective, in terms of their potential functional and neural underpinnings.

Memory Contextualization: The Role of Prefrontal Cortex in Functional Integration across Item and Context Representational Regions

Memory recall is facilitated when retrieval occurs in the original encoding context. This context dependency effect likely results from the automatic binding of central elements of an experience with contextual features (i.e., memory "contextualization") during encoding. However, despite a vast body of research investigating the neural correlates of explicit associative memory, the neural interactions during encoding that predict implicit context-dependent memory remain unknown. Twenty-six participants underwent fMRI during encoding of salient stimuli (faces), which were overlaid onto unique background images (contexts). To index subsequent context-dependent memory, face recognition was tested either in intact or rearranged contexts, after scanning. Enhanced face recognition in intact relative to rearranged contexts evidenced successful memory contextualization. Overall subsequent memory effects (brain activity predicting whether items were later remembered vs. forgotten) were found in the left inferior frontal gyrus (IFG) and right amygdala. Effective connectivity analyses showed that stronger context-dependent memory was associated with stronger coupling of the left IFG with face- and place-responsive areas, both within and between participants. Our findings indicate an important role for the IFG in integrating information across widespread regions involved in the representation of salient items and contextual features.

Potential avenues for exercise to activate episodic memory-related pathways: a narrative review

Memory function plays an important role in activities of daily living, and consequently, quality and quantity of life. In this narrative review, we discuss the anatomical components of episodic memory, including the structure of the hippocampus and the routes of communication to and from this structure. We also highlight cellular traces of memory, such as the engram cell and pathway. To provide etiological insight, the biological mechanisms of episodic memory are discussed, including factors subserving memory encoding (e.g., cognitive attention, neuroelectrical indices), consolidation (i.e., synaptic and brain systems level), and retrieval (e.g., availability of cues, context-dependent, state-dependent, and cognitive processing). Central to this manuscript, we highlight how exercise may influence each of these aforementioned parameters (e.g., exercise-induced hippocampal growth, synaptic plasticity, and cue retrieval) and then discuss the implications of these findings to enhance and preserve memory function. Collectively, this narrative review briefly summarizes potential mechanisms of episodic memory, and how exercise may activate these mechanistic pathways.

Similar patterns of neural activity predict memory function during encoding and retrieval

Neural networks that span the medial temporal lobe (MTL), prefrontal cortex, and posterior cortical regions are essential to episodic memory function in humans. Encoding and retrieval are supported by the engagement of both distinct neural pathways across the cortex and common structures within the medial temporal lobes. However, the degree to which memory performance can be determined by neural processing that is common to encoding and retrieval remains to be determined. To identify neural signatures of successful memory function, we administered a delayed free-recall task to 187 neurosurgical patients implanted with subdural or intraparenchymal depth electrodes. We developed multivariate classifiers to identify patterns of spectral power across the brain that independently predicted successful episodic encoding and retrieval. During encoding and retrieval, patterns of increased high frequency activity in prefrontal, MTL, and inferior parietal cortices, accompanied by widespread decreases in low frequency power across the brain predicted successful memory function. Using a cross-decoding approach, we demonstrate the ability to predict memory function across distinct phases of the free-recall task. Furthermore, we demonstrate that classifiers that combine information from both encoding and retrieval states can outperform task-independent models. These findings suggest that the engagement of a core memory network during either encoding or retrieval shapes the ability to remember the past, despite distinct neural interactions that facilitate encoding and retrieval.

Brain regions and functional interactions supporting early word recognition in the face of input variability

Perception and cognition in infants have been traditionally investigated using habituation paradigms, assuming that babies' memories in laboratory contexts are best constructed after numerous repetitions of the very same stimulus in the absence of interference. A crucial, yet open, question regards how babies deal with stimuli experienced in a fashion similar to everyday learning situations-namely, in the presence of interfering stimuli. To address this question, we used functional near-infrared spectroscopy to test 40 healthy newborns on their ability to encode words presented in concomitance with other words. The results evidenced a habituation-like hemodynamic response during encoding in the left-frontal region, which was associated with a progressive decrement of the functional connections between this region and the left-temporal, right-temporal, and right-parietal regions. In a recognition test phase, a characteristic neural signature of recognition recruited first the right-frontal region and subsequently the right-parietal ones. Connections originating from the right-temporal regions to these areas emerged when newborns listened to the familiar word in the test phase. These findings suggest a neural specialization at birth characterized by the lateralization of memory functions: the interplay between temporal and left-frontal regions during encoding and between temporo-parietal and right-frontal regions during recognition of speech sounds. Most critically, the results show that newborns are capable of retaining the sound of specific words despite hearing other stimuli during encoding. Thus, habituation designs that include various items may be as effective for studying early memory as repeated presentation of a single word.

Gamma oscillatory activity is impaired in episodic memory encoding with age

The present study proposes to investigate age-related episodic memory impairment in encoding. We collected ERPs in young and old participants performing a word-encoding task. For subsequently remembered words, young adults had greater activity at the left and anterior electrode sites, whereas old adults had greater posterior activity. Performance correlated positively with central sites in young adults but with left parietal hemisphere activity in old adults. Plus, a large left frontoparietal network increased its activity during the successful encoding for the Beta (13-30 Hz) and Gamma (30-100 Hz) bands in young adults. Old adults had increased activity in the right posterior parietal region for forgotten words in the Gamma band. Using a source localization analysis, we found that age leads to a decrease in Gamma band cerebral activity during encoding of words in the left hemisphere and the bilateral parahippocampal regions. These findings indicate that encoding impairment with age may be associated with dysfunctional Gamma oscillatory activity across a widespread network of left cortical regions.

Frontal Structural Neural Correlates of Working Memory Performance in Older Adults

Working memory is an executive memory process that allows transitional information to be held and manipulated temporarily in memory stores before being forgotten or encoded into long-term memory. Working memory is necessary for everyday decision-making and problem solving, making it a fundamental process in the daily lives of older adults. Working memory relies heavily on frontal lobe structures and is known to decline with age. The current study aimed to determine the neural correlates of decreased working memory performance in the frontal lobes by comparing cortical thickness and cortical surface area from two demographically matched groups of healthy older adults, free from cognitive impairment, with high versus low N-Back working memory performance (N = 56; average age = 70.29 ± 10.64). High-resolution structural T1-weighted images (1 mm isotropic voxels) were obtained on a 3T Philips MRI scanner. When compared to high performers, low performers exhibited significantly decreased cortical surface area in three frontal lobe regions lateralized to the right hemisphere: medial orbital frontal gyrus, inferior frontal gyrus, and superior frontal gyrus (FDR p < 0.05). There were no significant differences in cortical thickness between groups, a proxy for neurodegenerative tissue loss. Our results suggest that decreases in cortical surface area (a proxy for brain structural integrity) in right frontal regions may underlie age-related decline of working memory function.

Functional brain imaging of episodic memory decline in ageing

The episodic long-term memory system supports remembering of events. It is considered to be the most age-sensitive system, with an average onset of decline around 60 years of age. However, there is marked interindividual variability, such that some individuals show faster than average change and others show no or very little change. This variability may be related to the risk of developing dementia, with elevated risk for individuals with accelerated episodic memory decline. Brain imaging with functional magnetic resonance imaging (MRI) of blood oxygen level-dependent (BOLD) signalling or positron emission tomography (PET) has been used to reveal the brain bases of declining episodic memory in ageing. Several studies have demonstrated a link between age-related episodic memory decline and the hippocampus during active mnemonic processing, which is further supported by studies of hippocampal functional connectivity in the resting state. The hippocampus interacts with anterior and posterior neocortical regions to support episodic memory, and alterations in hippocampus-neocortex connectivity have been shown to contribute to impaired episodic memory. Multimodal MRI studies and more recently hybrid MRI/PET studies allow consideration of various factors that can influence the association between the hippocampal BOLD signal and memory performance. These include neurovascular factors, grey and white matter structural alterations, dopaminergic neurotransmission, amyloid-Β and glucose metabolism. Knowledge about the brain bases of episodic memory decline can guide interventions to strengthen memory in older adults, particularly in those with an elevated risk of developing dementia, with promising results for combinations of cognitive and physical stimulation.

On the Antecedents of an Electrophysiological Signature of Retrieval Mode

It has been proposed that people employ a common set of sustained operations (retrieval mode) when preparing to remember different kinds of episodic information. In two experiments, however, there was no evidence for the pattern of brain activity commonly assumed to index these operations. In both experiments event-related potentials (ERPs) were recorded time-locked to alternating preparatory cues signalling that participants should prepare for different retrieval tasks. One cue signalled episodic retrieval: remember the location where the object was presented in a prior study phase. The other signalled semantic retrieval: identify the location where the object is most commonly found (Experiment 1) or identify the typical size of the object (Experiment 2). In both experiments, only two trials of the same task were completed in succession. This enabled ERP contrasts between ‘repeat’ trials (the cue on the preceding trial signalled the same retrieval task), and ‘switch’ trials (the cue differed from the preceding trial). There were differences between the ERPs elicited by the preparatory task cues in Experiment 1 only: these were evident only on switch trials and comprised more positive-going activity over right-frontal scalp for the semantic than for the episodic task. These findings diverge from previous outcomes where the activity differentiating cues signalling preparation for episodic or semantic retrieval has been restricted to right-frontal scalp sites, comprising more positive-going activity for the episodic than for the semantic task. While these findings are consistent with the view that there is not a common set of operations engaged when people prepare to remember different kinds of episodic information, an alternative account is offered here, which is that these outcomes are a consequence of structural and temporal components of the experiment designs.

Changes in the modulation of brain activity during context encoding vs. context retrieval across the adult lifespan

Age-related deficits in context memory may arise from neural changes underlying both encoding and retrieval of context information. Although age-related functional changes in the brain regions supporting context memory begin at midlife, little is known about the functional changes with age that support context memory encoding and retrieval across the adult lifespan. We investigated how age-related functional changes support context memory across the adult lifespan by assessing linear changes with age during successful context encoding and retrieval. Using functional magnetic resonance imaging (fMRI), we compared young, middle-aged and older adults during both encoding and retrieval of spatial and temporal details of faces. Multivariate behavioral partial least squares (B-PLS) analysis of fMRI data identified a pattern of whole-brain activity that correlated with a linear age term and a pattern of whole-brain activity that was associated with an age-by-memory phase (encoding vs. retrieval) interaction. Further investigation of this latter effect identified three main findings: 1) reduced phase-related modulation in bilateral fusiform gyrus, left superior/anterior frontal gyrus and right inferior frontal gyrus that started at midlife and continued to older age, 2) reduced phase-related modulation in bilateral inferior parietal lobule that occurred only in older age, and 3) changes in phase-related modulation in older but not younger adults in left middle frontal gyrus and bilateral parahippocampal gyrus that was indicative of age-related over-recruitment. We conclude that age-related reductions in context memory arise in midlife and are related to changes in perceptual recollection and changes in fronto-parietal retrieval monitoring.