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Associative memory deficits in aging are frequently characterized by false recognition of novel stimulus associations, particularly when stimuli are similar. Introducing distinctive stimuli, therefore, can help guide item differentiation in memory and can further our understanding of how age-related brain changes impact behavior. How older adults use different types of distinctive information to distinguish overlapping events in memory and to avoid false associative recognition is still unknown. To test this, we manipulated the distinctiveness of items from two stimulus categories, scenes and objects, across three conditions: (1) distinct scenes paired with similar objects, (2) similar scenes paired with distinct objects, and (3) similar scenes paired with similar objects. Young and older adults studied scene-object pairs and then made both remember/know judgments toward single items as well as associative memory judgments to old and novel scene-object pairs ("Were these paired together?"). Older adults showed intact single item recognition of scenes and objects, regardless of whether those objects and scenes were similar or distinct. In contrast, relative to younger adults, older adults showed elevated false recognition for scene-object pairs, even when the scenes were distinct. These age-related associative memory deficits, however, disappeared if the pair contained an object that was visually distinct. In line with neural evidence that hippocampal functioning and scene processing decline with age, these results suggest that older adults can rely on memory for distinct objects, but not for distinct scenes, to distinguish between memories with overlapping features. [ABSTRACT FROM AUTHOR]

Temporal information, including information about temporal order and duration, is a fundamental component of event sequence memory. While previous research has demonstrated that aging can have a detrimental effect on memory for temporal order, there has been limited insight into the effect of aging on memory for durations, particularly within the context of sequences. In the current study, neurologically healthy young and older participants were administered two temporal match-mismatch tasks: one in which they were instructed on each trial to compare the temporal order or duration information of stimulus sequences presented first in a study phase and then, after a short delay, in a test phase (event sequence task); and a second in which participants were required to compare single durations or sequences of durations across study and test phases of each trial (pinwheel task). Consistent with the literature, the older participants were significantly poorer compared to their younger counterparts at making temporal order match-mismatch judgments in the event sequence task. In addition to this, data from both tasks suggested that the older adults were also less accurate at match-mismatch judgments based on duration information, with tentative evidence from the pinwheel task to suggest that this age-related effect was most prominent when the duration information was presented within a sequence. We suggest that age-related changes to medial temporal and frontal lobe function may contribute to changes in memory for temporal information in older adults, given the importance of these regions to event sequence memory. [ABSTRACT FROM AUTHOR]

Studies in rats and non-human primates suggest that medial temporal lobe (MTL) structures play a role in perceptual processing, with the hippocampus necessary for spatial discrimination, and the perirhinal cortex for object discrimination. Until recently, there was little convergent evidence for analogous functional specialisation in humans, or for a role of the MTL in processes beyond long-term memory. A recent series of novel human neuropsychological studies, however, in which paradigms from the animal literature were adapted and extended, have revealed findings remarkably similar to those seen in rats and monkeys. These experiments have demonstrated differential effects of distinct stimulus categories on performance in tasks for which there was no explicit requirement to remember information across trials. There is also accruing complementary evidence from functional neuroimaging that MTL structures show differential patterns of activation for scenes and objects, even on simple visual discrimination tasks. This article reviews some of these key studies and discusses the implications of these new findings for existing accounts of memory. A non-modular view of memory is proposed in which memory and perception depend upon the same anatomically distributed representations (emergent memory account). The limitations and criticisms of this theory are discussed and a number of outstanding questions proposed, including key predictions that can be tested by future studies. (Contains 10 figures.)

The frontal cortex and temporal lobes together regulate complex learning and memory capabilities. Here, we collected resting-state functional and diffusion-weighted MRI data before and after male rhesus macaque monkeys received extensive training to learn novel visuospatial discriminations (reward-guided learning). We found functional connectivity changes in orbitofrontal, ventromedial prefrontal, inferotemporal, entorhinal, retrosplenial, and anterior cingulate cortices, the subicular complex, and the dorsal, medial thalamus. These corticocortical and thalamocortical changes in functional connectivity were accompanied by related white matter structural alterations in the uncinate fasciculus, fornix, and ventral prefrontal tract: tracts that connect (sub)cortical networks and are implicated in learning and memory processes in monkeys and humans. After the well-trained monkeys received fornix transection, they were impaired in learning new visuospatial discriminations. In addition, the functional connectivity profile that was observed after the training was altered. These changes were accompanied by white matter changes in the ventral prefrontal tract, although the integrity of the uncinate fasciculus remained unchanged. Our experiments highlight the importance of different communication relayed among corticocortical and thalamocortical circuitry for the ability to learn new visuospatial associations (learning-to-learn) and to make reward-guided decisions. [ABSTRACT FROM AUTHOR]

The ventral portion of the rodent hippocampus (HPC; anterior in primates) has been implicated in the detection and resolution of approach–avoidance conflict, which arises when an organism encounters a stimulus that predicts both positive and negative outcomes. Previous work has found differential regulation of approach–avoidance conflict behavior by the CA3 and CA1 subfields, with inhibition of ventral CA3 increasing approach toward conflicting stimuli and inhibition of the ventral CA1 potentiating avoidance. Here, we sought to extend these findings by investigating the role of the dentate gyrus (DG), the input region of the HPC, in learned approach–avoidance conflict processing in rats. Animals were first trained to acquire three different visuotactile cue‐outcome associations in separate arms of a Y‐maze (appetitive, aversive, and neutral). Postacquisition, they were administered a "conflict test," in which they were presented with a choice between exploring an arm in which the appetitive and aversive cues were concurrently presented (conflict stimulus), and another arm containing the neutral stimulus. GABAR‐mediated inactivation of the ventral DG, but not dorsal DG, potentiated approach behavior toward the conflict stimulus, similar to the effects of ventral CA3 inactivation. In contrast, dorsal DG, but not ventral DG, inactivation was found to impair performance on a metric spatial discrimination task, which is commonly used as a test of pattern separation. The findings of this study demonstrate a robust double dissociation between the ventral and dorsal aspects of the DG, in line with previous reports of functional differences along the longitudinal axis of the HPC. [ABSTRACT FROM AUTHOR]

The medial temporal lobe (MTL) has been implicated in approach-avoidance (AA) conflict processing, which arises when a stimulus is imbued with both positive and negative valences. Notably, since the MTL has been traditionally viewed as a mnemonic brain region, a pertinent question is how AA conflict and memory processing interact with each other behaviourally. We conducted two behavioural experiments to examine whether increased AA conflict processing has a significant impact on incidental mnemonic encoding and inferential reasoning. In Experiment 1, participants first completed a reward and punishment AA task and were subsequently administered a surprise recognition memory test for stimuli that were presented during high and no AA conflict trials. In Experiment 2, participants completed a reward and punishment task in which they learned the valences of objects presented in pairs (AB, BC pairs). Next, we assessed their ability to integrate information across these pairs (infer A-C relationships) and examined whether inferential reasoning was more challenging across objects with conflicting compared to non-conflicting incentive values. We observed that increased motivational conflict did not significantly impact encoding or inferential reasoning. Potential explanations for these findings are considered, including the possibility that AA conflict and memory processing are not necessarily intertwined behaviourally. [ABSTRACT FROM AUTHOR]

There has been much interest in how the hippocampus codes time in support of episodic memory. Notably, while rodent hippocampal neurons, including populations in subfield CA1, have been shown to represent the passage of time in the order of seconds between events, there is limited support for a similar mechanism in humans. Specifically, there is no clear evidence that human hippocampal activity during long-term memory processing is sensitive to temporal duration information that spans seconds. To address this gap, we asked participants to first learn short event sequences that varied in image content and interval durations. During fMRI, participants then completed a recognition memory task, as well as a recall phase in which they were required to mentally replay each sequence in as much detail as possible. We found that individual sequences could be classified using activity patterns in the anterior hippocampus during recognition memory. Critically, successful classification was dependent on the conjunction of event content and temporal structure information (with unsuccessful classification of image content or interval duration alone), and further analyses suggested that the most informative voxels resided in the anterior CA1. Additionally, a classifier trained on anterior CA1 recognition data could successfully identify individual sequences from the mental replay data, suggesting that similar activity patterns supported participants' recognition and recall memory. Our findings complement recent rodent hippocampal research, and provide evidence that long-term sequence memory representations in the human hippocampus can reflect duration information in the order of seconds. [ABSTRACT FROM AUTHOR]

Cover legend: This cover image, by Danielle Douglas et al., is based on the Research Article Perception of Impossible Scenes Reveals Differential Hippocampal and Parahippocampal Place Area Contributions to Spatial Coherency, DOI: 10.1002/hipo.22673. [ABSTRACT FROM AUTHOR]

ABSTRACT Surprisingly little is known about how the brain combines spatial elements to form a coherent percept. Regions that may underlie this process include the hippocampus (HC) and parahippocampal place area (PPA), regions central to spatial perception but whose role in spatial coherency has not been explored. Participants were scanned with functional MRI while they judged whether Escher-like scenes were possible or impossible. Univariate analyses revealed differential HC and PPA involvement, with greater HC activity during spatial incoherency detection and more PPA activity during spatial coherency detection. Recognition and eye-tracking data ruled out long- or short-term memory confounds. Multivariate statistics demonstrated spatial coherency-dependent functional connectivity for the HC, but not PPA, with greater HC connectivity to various brain regions including lateral occipital complex during spatial incoherency detection. We suggest the PPA is preferentially involved during the perception of spatially coherent scenes, whereas the HC binds distinct features to create coherent representations. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]