The dual-process perspective and the benefits of retrieval practice in younger and older adults.

The testing effect is often considered a recollection-related phenomenon. However, recent work has observed a benefit of testing to both recollection and familiarity on immediate and delayed final tests. Further, although aging populations show marked declines in recollection, older and younger adults often benefit similarly from testing. This finding suggests that the testing effect in older adults may function via relatively preserved familiarity and lends further support to the hypothesis that the testing effect does not function solely via recollection-related processes. The current study builds on this work to better understand the mechanisms from the dual-process perspective that underlie the testing effect in both younger and older adults. To this end, younger (18-22 year old) and older (65-82 year old) adults studied words, took cued-recall tests on half of the words, and took a final Remember-Know recognition test on all words immediately or after a 1-day delay. At both delays, older and younger adults exhibited a testing effect in both recollection and familiarity, although the magnitude of the testing effect in recollection was reduced for older relative to younger adults. Implications for theories of the testing effect and its application in older adult populations are explored.

Parallel hippocampal-parietal circuits for self- and goal-oriented processing.

The hippocampus is critically important for a diverse range of cognitive processes, such as episodic memory, prospective memory, affective processing, and spatial navigation. Using individual-specific precision functional mapping of resting-state functional MRI data, we found the anterior hippocampus (head and body) to be preferentially functionally connected to the default mode network (DMN), as expected. The hippocampal tail, however, was strongly preferentially functionally connected to the parietal memory network (PMN), which supports goal-oriented cognition and stimulus recognition. This anterior-posterior dichotomy of resting-state functional connectivity was well-matched by differences in task deactivations and anatomical segmentations of the hippocampus. Task deactivations were localized to the hippocampal head and body (DMN), relatively sparing the tail (PMN). The functional dichotomization of the hippocampus into anterior DMN-connected and posterior PMN-connected parcels suggests parallel but distinct circuits between the hippocampus and medial parietal cortex for self- versus goal-oriented processing.

Are efficient learners of verbal stimuli also efficient and precise learners of visuospatial stimuli?

People differ in how quickly they learn information and how long they remember it, and these two variables are correlated such that people who learn more quickly tend to retain more of the newly learned information. Zerr and colleagues [2018. Learning efficiency: Identifying individual differences in learning rate and retention in healthy adults. Psychological Science, 29(9), 1436-1450] termed the relation between learning rate and retention as learning efficiency, with more efficient learners having both a faster acquisition rate and better memory performance after a delay. Zerr et al. also demonstrated in separate experiments that how efficiently someone learns is stable across a range of days and years with the same kind of stimuli. The current experiments (combined N = 231) replicate the finding that quicker learning coincides with better retention and demonstrate that the correlation extends to multiple types of materials. We also address the generalisability of learning efficiency: A person's efficiency with learning Lithuanian-English (verbal-verbal) pairs predicts their efficiency with Chinese-English (visuospatial-verbal) and (to a lesser extent) object-location (visuospatial-visuospatial) paired associates. Finally, we examine whether quicker learners also remember material more precisely by using a continuous measure of recall accuracy with object-location pairs.

The stability of visual perspective and vividness during mental time travel.

When remembering or imagining, people can experience an event from their own eyes, or as an outside observer, with differing levels of vividness. The perspective from, and vividness with, which a person remembers or imagines has been related to numerous individual difference characteristics. These findings require that phenomenology during mental time travel be trait-like-that people consistently experience similar perspectives and levels of vividness. This assumption remains untested. Across two studies (combined N = 295), we examined the stability of visual perspective and vividness across multiple trials and timepoints. Perspective and vividness showed weak within-session stability when reported across just a few trials but showed strong within-session stability when sufficient trials were collected. Importantly, both visual perspective and vividness demonstrated good-to-excellent across-session stability across different delay intervals (two days to six weeks). Overall, our results suggest that people dependably experience similar visual phenomenology across occurrences of mental time travel.

Practicing Retrieval Facilitates Learning.

How do we go about learning new information? This article reviews the importance of practicing retrieval of newly experienced information if one wants to be able to retrieve it again in the future. Specifically, practicing retrieval shortly after learning can slow the forgetting process. This benefit can be seen across various material types, and it seems prevalent in all ages and learner abilities and on all types of test. It can also be used to enhance student learning in a classroom setting. I review theoretical understanding of this phenomenon (sometimes referred to as the testing effect or as retrieval-based learning) and consider directions for future research.

Individual-specific functional connectivity of the amygdala: A substrate for precision psychiatry.

The amygdala is central to the pathophysiology of many psychiatric illnesses. An imprecise understanding of how the amygdala fits into the larger network organization of the human brain, however, limits our ability to create models of dysfunction in individual patients to guide personalized treatment. Therefore, we investigated the position of the amygdala and its functional subdivisions within the network organization of the brain in 10 highly sampled individuals (5 h of fMRI data per person). We characterized three functional subdivisions within the amygdala of each individual. We discovered that one subdivision is preferentially correlated with the default mode network; a second is preferentially correlated with the dorsal attention and fronto-parietal networks; and third subdivision does not have any networks to which it is preferentially correlated relative to the other two subdivisions. All three subdivisions are positively correlated with ventral attention and somatomotor networks and negatively correlated with salience and cingulo-opercular networks. These observations were replicated in an independent group dataset of 120 individuals. We also found substantial across-subject variation in the distribution and magnitude of amygdala functional connectivity with the cerebral cortex that related to individual differences in the stereotactic locations both of amygdala subdivisions and of cortical functional brain networks. Finally, using lag analyses, we found consistent temporal ordering of fMRI signals in the cortex relative to amygdala subdivisions. Altogether, this work provides a detailed framework of amygdala-cortical interactions that can be used as a foundation for models relating aberrations in amygdala connectivity to psychiatric symptoms in individual patients.

Integrative and Network-Specific Connectivity of the Basal Ganglia and Thalamus Defined in Individuals.

The basal ganglia, thalamus, and cerebral cortex form an interconnected network implicated in many neurological and psychiatric illnesses. A better understanding of cortico-subcortical circuits in individuals will aid in development of personalized treatments. Using precision functional mapping-individual-specific analysis of highly sampled human participants-we investigated individual-specific functional connectivity between subcortical structures and cortical functional networks. This approach revealed distinct subcortical zones of network specificity and multi-network integration. Integration zones were systematic, with convergence of cingulo-opercular control and somatomotor networks in the ventral intermediate thalamus (motor integration zones), dorsal attention and visual networks in the pulvinar, and default mode and multiple control networks in the caudate nucleus. The motor integration zones were present in every individual and correspond to consistently successful sites of deep brain stimulation (DBS; essential tremor). Individually variable subcortical zones correspond to DBS sites with less consistent treatment effects, highlighting the importance of PFM for neurosurgery, neurology, and psychiatry.

A role for familiarity in supporting the testing effect over time.

Endel Tulving (1985) drew a distinction between Remembering and Knowing, spurring a great deal of research on the memorial experiences of recollection and familiarity and their contribution to various phenomena in memory. More recently, studies have used this distinction to situate our understanding of the processes that contribute to the testing effect-or, the benefit of retrieval practice to later memory (see also Tulving, 1967). Using retention intervals of approximately 15 min or less between initial and final testing, several studies have found that initial testing magnifies estimates of recollection but not familiarity, regardless of whether a testing effect is revealed in overall recognition performance (Chan and McDermott, 2007). However, the efficacy of prior testing in enhancing memory has been shown to change over time, as have estimates of recollection and familiarity. Thus, the mechanisms that underlie the quintessential testing effect-one that occurs in overall recognition or recall over longer delays-are still uncertain. To investigate this issue, in two experiments, subjects studied word lists, took 3-letter stem cued-recall tests on half of the studied words, and completed a final recognition test in which estimates of recollection and familiarity were obtained via confidence (Experiment 1) or Remember-Know-New (Experiment 2) judgments. Critically, final recognition tests occurred either immediately, 1 day (Experiment 1 only), or 4 days after initial learning. At all retention intervals and in both methods of estimating recollection and familiarity on the final test (i.e. receiver-operating characteristic and remember-know analyses), initial testing magnified estimates of both recollection and familiarity. These findings suggest that the testing effect can result from changes in both processes and pose issues for theories of the testing effect that consider an exclusive role for recollection.

Trait-like variants in human functional brain networks.

Resting-state functional magnetic resonance imaging (fMRI) has provided converging descriptions of group-level functional brain organization. Recent work has revealed that functional networks identified in individuals contain local features that differ from the group-level description. We define these features as network variants. Building on these studies, we ask whether distributions of network variants reflect stable, trait-like differences in brain organization. Across several datasets of highly-sampled individuals we show that 1) variants are highly stable within individuals, 2) variants are found in characteristic locations and associate with characteristic functional networks across large groups, 3) task-evoked signals in variants demonstrate a link to functional variation, and 4) individuals cluster into subgroups on the basis of variant characteristics that are related to differences in behavior. These results suggest that distributions of network variants may reflect stable, trait-like, functionally relevant individual differences in functional brain organization.

High-fidelity mapping of repetition-related changes in the parietal memory network.

fMRI studies of human memory have identified a "parietal memory network" (PMN) that displays distinct responses to novel and familiar stimuli, typically deactivating during initial encoding but robustly activating during retrieval. The small size of PMN regions, combined with their proximity to the neighboring default mode network, makes a targeted assessment of their responses in highly sampled subjects important for understanding information processing within the network. Here, we describe an experiment in which participants made semantic decisions about repeatedly-presented stimuli, assessing PMN BOLD responses as items transitioned from experimentally novel to repeated. Data are from the highly-sampled subjects in the Midnight Scan Club dataset, enabling a characterization of BOLD responses at both the group and single-subject level. Across all analyses, PMN regions deactivated in response to novel stimuli and displayed changes in BOLD activity across presentations, but did not significantly activate to repeated items. Results support only a portion of initially hypothesized effects, in particular suggesting that novelty-related deactivations may be less susceptible to attentional/task manipulations than are repetition-related activations within the network. This in turn suggests that novelty and familiarity may be processed as separable entities within the PMN.

Spatial and Temporal Organization of the Individual Human Cerebellum.

The cerebellum contains the majority of neurons in the human brain and is unique for its uniform cytoarchitecture, absence of aerobic glycolysis, and role in adaptive plasticity. Despite anatomical and physiological differences between the cerebellum and cerebral cortex, group-average functional connectivity studies have identified networks related to specific functions in both structures. Recently, precision functional mapping of individuals revealed that functional networks in the cerebral cortex exhibit measurable individual specificity. Using the highly sampled Midnight Scan Club (MSC) dataset, we found the cerebellum contains reliable, individual-specific network organization that is significantly more variable than the cerebral cortex. The frontoparietal network, thought to support adaptive control, was the only network overrepresented in the cerebellum compared to the cerebral cortex (2.3-fold). Temporally, all cerebellar resting state signals lagged behind the cerebral cortex (125-380 ms), supporting the hypothesis that the cerebellum engages in a domain-general function in the adaptive control of all cortical processes.

Learning Efficiency: Identifying Individual Differences in Learning Rate and Retention in Healthy Adults.

People differ in how quickly they learn information and how long they remember it, yet individual differences in learning abilities within healthy adults have been relatively neglected. In two studies, we examined the relation between learning rate and subsequent retention using a new foreign-language paired-associates task (the learning-efficiency task), which was designed to eliminate ceiling effects that often accompany standardized tests of learning and memory in healthy adults. A key finding was that quicker learners were also more durable learners (i.e., exhibited better retention across a delay), despite studying the material for less time. Additionally, measures of learning and memory from this task were reliable in Study 1 ( N = 281) across 30 hr and Study 2 ( N = 92; follow-up n = 46) across 3 years. We conclude that people vary in how efficiently they learn, and we describe a reliable and valid method for assessing learning efficiency within healthy adults.

Remembering What We Learn.

Memories are the internal mental records that we maintain, which give us instant access to our personal past, complete with all of the facts that we know and the skills that we have cultivated. While the mind's capacity to store and recall information is truly wondrous, there are desirable and undesirable difficulties in learning. Our authors provide examples of retrieval practice and individual differences in long-term retention and explore quick and slow learners.

BOLD Activity During Correct-Answer Feedback in Cued Recall Predicts Subsequent Retrieval Performance: An fMRI Investigation Using a Partial Trial Design.

Receiving correct answer feedback following a retrieval attempt has proven to be a highly effective means of learning new information, yet the mechanisms behind its efficacy remain poorly understood. Here, fMRI was used to examine how BOLD activity measured during a period of feedback could predict subsequent memory (SM) performance on a final test. Twenty-five human subjects studied pairs of associated words, and were then asked to covertly recall target words in response to provided cues. Correct answer feedback was provided immediately after covert retrieval attempts. A partial trial design enabled separate modeling of activity related to retrieval and to feedback processing. During initial study, typical SM effects were observed across the whole brain. During feedback following a failed recall attempt, activity in only a subset of these regions predicted final test performance. These regions fell within the default mode network (DMN) and demonstrated negative SM effects, such that greater deactivation was associated with successful recall. No "task-positive" regions demonstrated SM effects in this contrast. The obtained results are consistent with a growing literature that associates DMN deactivation with successful learning in multiple task contexts, likely reflecting differences in the allocation of attentional resources during encoding.

Task-related and resting-state fMRI identify distinct networks that preferentially support remembering the past and imagining the future.

The relation between episodic memory and episodic future thought (EFT) remains an active target of research. A growing literature suggests that similar cognitive processes and neural substrates tend to support these acts. However, direct comparisons of whole-brain activity reveal clear differences, with numerous regions more active when engaging in EFT than when remembering, and a smaller collection of regions displaying the opposite pattern of activity. Although various network labels have been applied to prior neuroimaging results, to date no formal resting-state functional connectivity analysis has been conducted. In the current experiment, 48 subjects remembered events from their past and engaged in EFT. Resting-state data were collected from all subjects. Task results replicated recent findings, with more activity during EFT in regions across frontal and parietal cortex, and with more activity during remembering in a smaller number of predominantly parahippocampal and retrosplenial regions. Resting-state connectivity analysis, based on seed locations defined using the fMRI task data, indicated that regions preferentially activated during EFT fell primarily within the default mode network, while those more active during remembering fell primarily within the contextual association network. These results suggest that despite their general similarity, the functional network membership of regions showing task differences is dissociable. We discuss our results in light of several hypotheses that attempt to relate remembering and EFT, and suggest that the data speak to differences in the relative contributions of episodic and semantic memory, as well as controlled and automatic processing, during the acts of remembering or engaging in EFT.

Precision Functional Mapping of Individual Human Brains.

Human functional MRI (fMRI) research primarily focuses on analyzing data averaged across groups, which limits the detail, specificity, and clinical utility of fMRI resting-state functional connectivity (RSFC) and task-activation maps. To push our understanding of functional brain organization to the level of individual humans, we assembled a novel MRI dataset containing 5 hr of RSFC data, 6 hr of task fMRI, multiple structural MRIs, and neuropsychological tests from each of ten adults. Using these data, we generated ten high-fidelity, individual-specific functional connectomes. This individual-connectome approach revealed several new types of spatial and organizational variability in brain networks, including unique network features and topologies that corresponded with structural and task-derived brain features. We are releasing this highly sampled, individual-focused dataset as a resource for neuroscientists, and we propose precision individual connectomics as a model for future work examining the organization of healthy and diseased individual human brains.

Are There Multiple Kinds of Episodic Memory? An fMRI Investigation Comparing Autobiographical and Recognition Memory Tasks.

What brain regions underlie retrieval from episodic memory? The bulk of research addressing this question with fMRI has relied upon recognition memory for materials encoded within the laboratory. Another, less dominant tradition has used autobiographical methods, whereby people recall events from their lifetime, often after being cued with words or pictures. The current study addresses how the neural substrates of successful memory retrieval differed as a function of the targeted memory when the experimental parameters were held constant in the two conditions (except for instructions). Human participants studied a set of scenes and then took two types of memory test while undergoing fMRI scanning. In one condition (the picture memory test), participants reported for each scene (32 studied, 64 nonstudied) whether it was recollected from the prior study episode. In a second condition (the life memory test), participants reported for each scene (32 studied, 64 nonstudied) whether it reminded them of a specific event from their preexperimental lifetime. An examination of successful retrieval (yes responses) for recently studied scenes for the two test types revealed pronounced differences; that is, autobiographical retrieval instantiated with the life memory test preferentially activated the default mode network, whereas hits in the picture memory test preferentially engaged the parietal memory network as well as portions of the frontoparietal control network. When experimental cueing parameters are held constant, the neural underpinnings of successful memory retrieval differ when remembering life events and recently learned events.SIGNIFICANCE STATEMENT Episodic memory is often discussed as a solitary construct. However, experimental traditions examining episodic memory use very different approaches, and these are rarely compared to one another. When the neural correlates associated with each approach have been directly contrasted, results have varied considerably and at times contradicted each other. The present experiment was designed to match the two primary approaches to studying episodic memory in an unparalleled manner. Results suggest a clear separation of systems supporting memory as it is typically tested in the laboratory and memory as assessed under autobiographical retrieval conditions. These data provide neurobiological evidence that episodic memory is not a single construct, challenging the degree to which different experimental traditions are studying the same construct.

The parietal memory network activates similarly for true and associative false recognition elicited via the DRM procedure.

Neuroimaging investigations of human memory encoding and retrieval have revealed that multiple regions of parietal cortex contribute to memory. Recently, a sparse network of regions within parietal cortex has been identified using resting state functional connectivity (MRI techniques). The regions within this network exhibit consistent task-related responses during memory formation and retrieval, leading to its being called the parietal memory network (PMN). Among its signature patterns are: deactivation during initial experience with an item (e.g., encoding); activation during subsequent repetitions (e.g., at retrieval); greater activation for successfully retrieved familiar words than novel words (e.g., hits relative to correctly-rejected lures). The question of interest here is whether novel words that are subjectively experienced as having been recently studied would elicit PMN activation similar to that of hits. That is, we compared old items correctly recognized to two types of novel items on a recognition test: those correctly identified as new and those incorrectly labeled as old due to their strong associative relation to the studied words (in the DRM false memory protocol). Subjective oldness plays a strong role in driving activation, as hits and false alarms activated similarly (and greater than correctly-rejected lures).

The Contextual Association Network Activates More for Remembered than for Imagined Events.

The human capacities to remember events from the past and imagine events in the future rely on highly overlapping neural substrates. Neuroimaging studies have revealed brain regions that are more active for imagined events than remembered events, but the reverse pattern has not been shown consistently. Given that remembered events tend to be associated with more contextual information ( Johnson et al. 1988), one might expect a set of regions to demonstrate greater activity for remembered events. Specifically, regions sensitive to the strength of contextual associations might be hypothesized to show greater activity for remembered events. The present experiment tests this hypothesis. fMRI was used to identify brain regions within the contextual association network ( Bar and Aminoff 2003); regions within this network were then examined to see whether they showed differential activity during remembering and imagining. Bilateral regions within the parahippocampal cortex and retrosplenial complex responded more strongly to remembered past events, supporting work that suggests these events have more contextual information associated with them. Follow-up voxel-wise analysis demonstrated the specificity of these results, as did re-analysis of previous experimental datasets. These results suggest that a key differentiating feature of remembering and imagining is the strength of contextual associations.

Visual perspective in remembering and episodic future thought.

According to the constructive episodic simulation hypothesis, remembering and episodic future thinking are supported by a common set of constructive processes. In the present study, we directly addressed this assertion in the context of third-person perspectives that arise during remembering and episodic future thought. Specifically, we examined the frequency with which participants remembered past events or imagined future events from third-person perspectives. We also examined the different viewpoints from which third-person perspective events were remembered or imagined. Although future events were somewhat more likely to be imagined from a third-person perspective, the spatial viewpoint distributions of third-person perspectives characterizing remembered and imagined events were highly similar. These results suggest that a similar constructive mechanism may be at work when people remember events from a perspective that could not have been experienced in the past and when they imagine events from a perspective that could not be experienced in the future. The findings are discussed in terms of their consistency with--and as extensions of--the constructive episodic simulation hypothesis.