Coding of episodic memory in the human hippocampus

Wixted, John T.; Goldinger, Stephen D.; Squire, Larry R.; Kuhn, Joel R.; Papesh, Megan H.; Smith, Kris A.; Treiman, David M.; Steinmetz, Peter

doi:10.1073/pnas.1716443115

Cited by 48 publications

(37 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In that case, although activity in a large fraction of hippocampal neurons is predictive of later performance, relatively few neurons would represent the successfully encoded memory trace and later be reactivated at the second presentation of the word. Moreover, on the basis of earlier work, we expect that the few neurons that are active at retrieval will differ for different repeated words (25,26). Although speculative, we suggest that a small subset of active hippocampal neurons is recruited to encode a specific episodic memory (27,28) and that such recruitment is more likely to succeed when preonset activity in the hippocampus is relatively high compared to when it is relatively low.…”

Section: Discussionmentioning

confidence: 69%

Spiking activity in the human hippocampus prior to encoding predicts subsequent memory

Urgolites

Wixted

Goldinger

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Encoding activity in the medial temporal lobe, presumably evoked by the presentation of stimuli (postonset activity), is known to predict subsequent memory. However, several independent lines of research suggest that preonset activity also affects subsequent memory. We investigated the role of preonset and postonset single-unit and multiunit activity recorded from epilepsy patients as they completed a continuous recognition task. In this task, words were presented in a continuous series and eventually began to repeat. For each word, the patient’s task was to decide whether it was novel or repeated. We found that preonset spiking activity in the hippocampus (when the word was novel) predicted subsequent memory (when the word was later repeated). Postonset activity during encoding also predicted subsequent memory, but was simply a continuation of preonset activity. The predictive effect of preonset spiking activity was much stronger in the hippocampus than in three other brain regions (amygdala, anterior cingulate, and prefrontal cortex). In addition, preonset and postonset activity around the encoding of novel words did not predict memory performance for novel words (i.e., correctly classifying the word as novel), and preonset and postonset activity around the time of retrieval did not predict memory performance for repeated words (i.e., correctly classifying the word as repeated). Thus, the only predictive effect was between preonset activity (along with its postonset continuation) at the time of encoding and subsequent memory. Taken together, these findings indicate that preonset hippocampal activity does not reflect general arousal/attention but instead reflects what we term “attention to encoding.”

show abstract

Section: Discussionmentioning

confidence: 69%

Spiking activity in the human hippocampus prior to encoding predicts subsequent memory

Urgolites

Wixted

Goldinger

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The evidence that the VMPFc and hippocampus play a key role in both subjects with impaired AM (8) and normal subjects (7,(13)(14)(15), as well as in subjects with HSAM, suggests that the current level of prefrontal/hippocampal activity may play a critical role in determining the hypofunctioning (i.e., SDAM) vs. hyperfunctioning (i.e., HSAM) of AM retrieval. Although the increased hippocampal activity in subjects with HSAM might potentially reflect task-related encoding activity (26), the fact that the hippocampal activity increased as a function of longer latencies (indicating increased difficulty) to access the most remote (firsttime) events appears to indicate a selective role of the hippocampus in AM retrieval. This latter finding is in agreement with the hypothesis that AMs might permanently depend on the hippocampal activity (27).…”

Section: Discussionmentioning

confidence: 93%

Enhanced brain activity associated with memory access in highly superior autobiographical memory

Santangelo

Cavallina

Colucci

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Brain systems underlying human memory function have been classically investigated studying patients with selective memory impairments. The discovery of rare individuals who have highly superior autobiographical memory (HSAM) provides, instead, an opportunity to investigate the brain systems underlying enhanced memory. Here, we carried out an fMRI investigation of a group of subjects identified as having HSAM. During fMRI scanning, eight subjects with HSAM and 21 control subjects were asked to retrieve autobiographical memories (AMs) as well as non-AMs (e.g., examples of animals). Subjects were instructed to signal the "access" to an AM by a key press and to continue "reliving" it immediately after. Compared with controls, individuals with HSAM provided a richer AM recollection and were faster in accessing AMs. The access to AMs was associated with enhanced prefrontal/hippocampal functional connectivity. AM access also induced increased activity in the left temporoparietal junction and enhanced functional coupling with sensory cortices in subjects with HSAM compared with controls. In contrast, subjects with HSAM did not differ from controls in functional activity during the reliving phase. These findings, based on fMRI assessment, provide evidence of interaction of brain systems engaged in memory retrieval and suggest that enhanced activity of these systems is selectively involved in enabling more efficient access to past experiences in HSAM.

show abstract

“…The present study was designed to assess the utility of an on-line adaptation of a continuous recognition task (CRT) paradigm [24], for assessing cognitive function in a population of community-dwelling individuals who had not been identified as having dementia. The CRT paradigm is widely used in academic studies of memory mechanisms [25]. The CRT approach was first implemented as an audience demonstration tool that provided data on individuals who were interested in memory problems [26].…”

Section: Introductionmentioning

confidence: 99%

The MemTrax Test Compared to the Montreal Cognitive Assessment Estimation of Mild Cognitive Impairment

Hoek

Nieuwenhuizen

Keijer

et al. 2019

JAD

View full text Add to dashboard Cite

Cognitive impairment is a leading cause of dysfunction in the elderly. When mild cognitive impairment (MCI) occurs in elderly, it is frequently a prodromal condition to dementia. The Montreal Cognitive Assessment (MoCA) is a commonly used tool to screen for MCI. However, this test requires a face-to-face administration and is composed of an assortment of questions whose responses are added together by the rater to provide a score whose precise meaning has been controversial. This study was designed to evaluate the performance of a computerized memory test (MemTrax), which is an adaptation of a continuous recognition task, with respect to the MoCA. Two outcome measures are generated from the MemTrax test: MemTrax speed and MemTrax correct . Subjects were administered the MoCA and the MemTrax test. Based on the results of the MoCA, subjects were divided in two groups of cognitive status: normal cognition ( n = 45) and MCI ( n = 37). Mean MemTrax scores were significantly lower in the MCI than in the normal cognition group. All MemTrax outcome variables were positively associated with the MoCA. Two methods, computing the average MTX score and linear regression were used to estimate the cutoff values of the MemTrax test to detect MCI. These methods showed that for the outcome MemTrax speed a score below the range of 0.87 – 91 s -1 is an indication of MCI, and for the outcome MemTrax correct a score below the range of 85 – 90% is an indication for MCI.

show abstract

Coding of episodic memory in the human hippocampus

Cited by 48 publications

References 43 publications

Spiking activity in the human hippocampus prior to encoding predicts subsequent memory

Spiking activity in the human hippocampus prior to encoding predicts subsequent memory

Enhanced brain activity associated with memory access in highly superior autobiographical memory

The MemTrax Test Compared to the Montreal Cognitive Assessment Estimation of Mild Cognitive Impairment

Contact Info

Product

Resources

About