scholarly journals Failure to reactivate salient episodic information during indirect and direct tests of memory retrieval

2017 ◽  
Author(s):  
Mason H. Price ◽  
Jeffrey D. Johnson
Keyword(s):  
Boundary Condition ◽  
Episodic Memory ◽  
Neural Activity ◽  
Memory Retrieval ◽  
Conscious Awareness ◽  
Episodic Retrieval ◽  
Flicker Frequency ◽  
Test Items ◽  
Episodic Information ◽  
Cortical Regions

ABSTRACTSeveral fMRI and EEG studies have demonstrated that successful episodic retrieval is accompanied by the reactivation of cortical regions that were active during encoding. These findings are consistent with influential models of episodic memory that posit that conscious retrieval (recollection) relies on hippocampally-mediated cortical reinstatement. Evidence of reactivation corresponding to episodic information that is beyond conscious awareness at the time of memory retrieval, however, is limited. A recent exception is from an EEG study by Wimber, Maaβ, Staudigl, Richardson-Klavehn, and Hanslmayr (2012) in which words were encoded in the context of highly salient visual flicker entrainment and then presented at retrieval in the absence of any flicker. In that study, coherent (phase-locked) neural activity was observed at the corresponding entrained frequencies during retrieval, consistent with the notion that encoding representations were reactivated. Given the important implications of unconscious reactivation to past findings and the modeling literature, the current study set out to provide a direct replication of the previous study. Additionally, an attempt was made to extend such findings to intentional retrieval by acquiring EEG while subjects were explicitly asked to make memory judgments about the flicker frequency from encoding. Throughout a comprehensive set of analyses, the current study consistently failed to demonstrate evidence for unconscious reactivation, and instead provided support that test items were indistinguishable according to their prior encoding context. The findings thus establish an important boundary condition for the involvement of cortical reinstatement in episodic memory.

Going Their Separate Ways: Dissociation of Hippocampal and Dorsolateral Prefrontal Activation during Episodic Retrieval and Post-retrieval Processing

2010 ◽  
Vol 22 (3) ◽  
pp. 513-525 ◽  
Author(s):  
Sarah L. Israel ◽  
Tyler M. Seibert ◽  
Michelle L. Black ◽  
James B. Brewer
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Relative Increase ◽  
Network Activity ◽  
Default Network ◽  
Episodic Retrieval ◽  
Retrieval Task ◽  
Paired Associates ◽  
Hippocampal Activity ◽  
Dorsolateral Prefrontal

Hippocampal activity is modulated during episodic memory retrieval. Most consistently, a relative increase in activity during confident retrieval is observed. Dorsolateral prefrontal cortex (DLPFC) is also activated during retrieval, but may be more generally activated during cognitive-control processes. The “default network,” regions activated during rest or internally focused tasks, includes the hippocampus, but not DLPFC. Therefore, DLPFC and the hippocampus should diverge during difficult tasks suppressing the default network. It is unclear, however, whether a difficult episodic memory retrieval task would suppress the default network due to difficulty or activate it due to internally directed attention. We hypothesized that a task requiring episodic retrieval followed by rumination on the retrieved item would increase DLPFC activity, but paradoxically reduce hippocampal activity due to concomitant suppression of the default network. In the present study, blocked and event-related fMRI were used to examine hippocampal activity during episodic memory recollection and postretrieval processing of paired associates. Subjects were asked to make living/nonliving judgments about items visually presented (classify) or items retrieved from memory (recall–classify). Active and passive baselines were used to differentiate task-related activity from default-network activity. During the “recall–classify” task, anterior hippocampal activity was selectively reduced relative to “classify” and baseline tasks, and this activity was inversely correlated with DLPFC. Reaction time was positively correlated with DLPFC activation and default-network/hippocampal suppression. The findings demonstrate that frontal and hippocampal activity are dissociated during difficult episodic retrieval tasks and reveal important considerations for interpreting hippocampal activity associated with successful episodic retrieval.

scholarly journals Electrophysiological signatures of memory reactivation in humans

2020 ◽  
Vol 375 (1799) ◽  
pp. 20190293 ◽  
Author(s):  
Thomas Schreiner ◽  
Tobias Staudigl
Keyword(s):  
Episodic Memory ◽  
Neural Activity ◽  
Crucial Role ◽  
Memory Retrieval ◽  
Functional Significance ◽  
State Of The Art ◽  
Memory Reactivation ◽  
Open Questions ◽  
Neural Processes

The reactivation of neural activity that was present during the encoding of an event is assumed to be essential for human episodic memory retrieval and the consolidation of memories during sleep. Pioneering animal work has already established a crucial role of memory reactivation to prepare and guide behaviour. Research in humans is now delineating the neural processes involved in memory reactivation during both wakefulness and sleep as well as their functional significance. Focusing on the electrophysiological signatures of memory reactivation in humans during both memory retrieval and sleep-related consolidation, this review provides an overview of the state of the art in the field. We outline recent advances, methodological developments and open questions and specifically highlight commonalities and differences in the neuronal signatures of memory reactivation during the states of wakefulness and sleep. This article is part of the Theo Murphy meeting issue ‘Memory reactivation: replaying events past, present and future’.

Lateralization of Prefrontal Activity during Episodic Memory Retrieval: Evidence for the Production-Monitoring Hypothesis

2003 ◽  
Vol 15 (2) ◽  
pp. 249-259 ◽  
Author(s):  
Roberto Cabeza ◽  
Jill K. Locantore ◽  
Nicole D. Anderson
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Item Recognition ◽  
Cued Recall ◽  
Anterior Cingulate ◽  
Episodic Retrieval ◽  
Context Recognition ◽  
Production Monitoring ◽  
The Right

We propose a new hypothesis concerning the lateralization of prefrontal cortex (PFC) activity during verbal episodic memory retrieval. The hypothesis states that the left PFC is differentially more involved in semantically guided information production than is the right PFC, and that the right PFC is differentially more involved in monitoring and verification than is the left PFC. This “production-monitoring hypothesis” differs from the existing “systematic-heuristic hypothesis,” which proposes that the left PFC is primarily involved in systematic retrieval operations, and the right PFC in heuristic retrieval operations. To compare the two hypotheses, we measured PFC activity using positron emission tomography (PET) during the performance of four episodic retrieval tasks: stem cued recall, associative cued recall, context recognition (source memory), and item recognition. Recall tasks emphasized production processes, whereas recognition tasks emphasized monitoring processes. Stem cued recall and context-recognition tasks underscored systematic operations, whereas associative cued recall and item-recognition tasks underscored heuristic operations. Consistent with the production-monitoring hypothesis, the left PFC was more activated for recall than for recognition tasks and the right PFC was more activated for recognition than for recall tasks. Inconsistent with the systematic-heuristic hypothesis, the left PFC was more activated for heuristic than for systematic tasks and the right PFC showed the converse result. Additionally, the study yielded activation differences outside the PFC. In agreement with a previous recall/recognition PET study, anterior cingulate, cerebellar, and striatal regions were more activated for recall than for recognition tasks, and the converse occurred for posterior parietal regions. A right medial temporal lobe region was more activated for stem cued recall and context recognition than for associative cued recall and item recognition, possibly reflecting perceptual integration. In sum, the results provide evidence for the production-monitoring hypothesis and clarify the role of different brain regions typically activated in PET and functional magnetic resonance imaging (fMRI) studies of episodic retrieval.

scholarly journals Reinstatement of Event Details during Episodic Simulation in the Hippocampus

2019 ◽  
Vol 30 (4) ◽  
pp. 2321-2337 ◽  
Author(s):  
Preston P Thakral ◽  
Kevin P Madore ◽  
Donna Rose Addis ◽  
Daniel L Schacter
Keyword(s):  
Episodic Memory ◽  
Subjective Experience ◽  
Functional Neuroimaging ◽  
Specific Information ◽  
Episodic Retrieval ◽  
The People ◽  
Episodic Information ◽  
Episodic Simulation ◽  
Pattern Similarity ◽  
Neuroimaging Study

Abstract According to the constructive episodic simulation hypothesis, episodic simulation (i.e., imagining specific novel future episodes) draws on some of the same neurocognitive processes that support episodic memory (i.e., recalling specific past episodes). Episodic retrieval supports the ability to simulate future experiences by providing access to episodic details (e.g., the people and locations that comprise memories) that can be recombined in new ways. In the current functional neuroimaging study, we test this hypothesis by examining whether the hippocampus, a region implicated in the reinstatement of episodic information during memory, supports reinstatement of episodic information during simulation. Employing a multivoxel pattern similarity analysis, we interrogated the similarity between hippocampal neural patterns during memory and simulation at the level of individual event details. Our findings indicate that the hippocampus supports the reinstatement of detail-specific information from episodic memory during simulation, with the level of reinstatement contributing to the subjective experience of simulated details.

scholarly journals Schematic memories develop quickly, but are not expressed unless necessary

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Alexa Tompary ◽  
WenXi Zhou ◽  
Lila Davachi
Keyword(s):  
Spatial Distribution ◽  
Episodic Memory ◽  
Memory Retrieval ◽  
Fading Memory ◽  
Episodic Retrieval ◽  
Memory Representations ◽  
Over Time

Abstract Episodic memory retrieval is increasingly influenced by schematic information as memories mature, but it is unclear whether this is due to the slow formation of schemas over time, or the slow forgetting of the episodes. To address this, we separately probed memory for newly learned schemas as well as their influence on episodic memory decisions. In this experiment, participants encoded images from two categories, with the location of images in each category drawn from a different spatial distribution. They could thus learn schemas of category locations by encoding specific episodes. We found that images that were more consistent with these distributions were more precisely retrieved, and this schematic influence increased over time. However, memory for the schema distribution, measured using generalization to novel images, also became less precise over time. This incongruity suggests that schemas form rapidly, but their influence on episodic retrieval is dictated by the need to bolster fading memory representations.

scholarly journals Core Network Contributions to Remembering the Past, Imagining the Future, and Thinking Creatively

2018 ◽  
Vol 30 (12) ◽  
pp. 1939-1951 ◽  
Author(s):  
Roger E. Beaty ◽  
Preston P. Thakral ◽  
Kevin P. Madore ◽  
Mathias Benedek ◽  
Daniel L. Schacter
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Divergent Thinking ◽  
Brain Activity ◽  
Inferior Frontal Gyrus ◽  
Parahippocampal Gyrus ◽  
Episodic Retrieval ◽  
Core Network ◽  
Creative Cognition ◽  
The Core

The core network refers to a set of neural regions that have been consistently associated with episodic memory retrieval and episodic future simulation. This network is thought to support the constructive thought processes that allow the retrieval and flexible combination of stored information to reconstruct past and construct novel future experiences. Recent behavioral research points to an overlap between these constructive processes and those also engaged during divergent thinking—the ability to think creatively and generate novel ideas—but the extent to which they involve common neural correlates remains unclear. Using fMRI, we sought to address this question by assessing brain activity as participants recalled past experiences, simulated future experiences, or engaged in divergent thinking. Consistent with past work, we found that episodic retrieval and future simulation activated the core network compared with a semantic control condition. Critically, a triple conjunction of episodic retrieval, future simulation, and divergent thinking revealed common engagement of core network regions, including the bilateral hippocampus and parahippocampal gyrus, as well as other regions involved in memory retrieval (inferior frontal gyrus) and mental imagery (middle occipital gyrus). The results provide further insight into the roles of the hippocampus and the core network in episodic memory retrieval, future simulation, and divergent thinking and extend recent work highlighting the involvement of constructive episodic processes in creative cognition.

scholarly journals Schematic memories develop quickly, but are not expressed unless necessary

2020 ◽  
Author(s):  
Alexa Tompary ◽  
WenXi Zhou ◽  
Lila Davachi
Keyword(s):  
Spatial Distribution ◽  
Episodic Memory ◽  
Memory Retrieval ◽  
Fading Memory ◽  
Episodic Retrieval ◽  
Slow Decay ◽  
Memory Representations ◽  
Over Time

Episodic memory retrieval is increasingly influenced by schematic information as memories mature, but it is unclear whether this is due to the slow formation of schemas over time, or the slow decay of the episodes. To address this, we separately probed memory for newly learned schemas as well as their influence on episodic memory decisions. In this experiment, participants encoded images from two categories, with the location of images in each category drawn from a different spatial distribution. They could thus learn schemas of category locations by encoding specific episodes. We found that images that were more consistent with these distributions were more precisely retrieved, and this schematic influence increased over time. However, memory for the schema distribution, measured using generalization to novel images, also became less precise over time. This incongruity suggests that schemas form rapidly, but their influence on episodic retrieval is dictated by the need to bolster fading memory representations.

scholarly journals The neural basis of episodic memory: evidence from functional neuroimaging

2002 ◽  
Vol 357 (1424) ◽  
pp. 1097-1110 ◽  
Author(s):  
Michael D. Rugg ◽  
Leun J. Otten ◽  
Richard N. A. Henson
Keyword(s):  
Episodic Memory ◽  
Neural Activity ◽  
Functional Neuroimaging ◽  
Neural Basis ◽  
Retrieval Task ◽  
Cortical Level ◽  
Episodic Information ◽  
Episodic Encoding ◽  
Episodic Memories ◽  
Anterior Prefrontal Cortex

We review some of our recent research using functional neuroimaging to investigate neural activity supporting the encoding and retrieval of episodic memories, that is, memories for unique events. Findings from studies of encoding indicate that, at the cortical level, the regions responsible for the effective encoding of a stimulus event as an episodic memory include some of the regions that are also engaged to process the event ‘online’. Thus, it appears that there is no single cortical site or circuit responsible for episodic encoding. The results of retrieval studies indicate that successful recollection of episodic information is associated with activation of lateral parietal cortex, along with more variable patterns of activity in dorsolateral and anterior prefrontal cortex. Whereas parietal regions may play a part in the representation of retrieved information, prefrontal areas appear to support processes that act on the products of retrieval to align behaviour with the demands of the retrieval task.

scholarly journals Where Memory Meets Attention: Neural Substrates of Negative Priming

2005 ◽  
Vol 17 (11) ◽  
pp. 1774-1784 ◽  
Author(s):  
Tobias Egner ◽  
Joy Hirsch
Keyword(s):  
Selective Attention ◽  
Episodic Memory ◽  
Negative Priming ◽  
Memory Retrieval ◽  
Color Naming ◽  
Selective Inhibition ◽  
Episodic Retrieval ◽  
Stimulus Feature ◽  
Retrieval Models ◽  
The Right

The negative priming (NP) effect refers to the observed increase in identification time for a current target stimulus or stimulus feature (the “probe”) that has been employed as a distractor stimulus or stimulus feature on the previous trial (the “prime”), representing strong evidence that ignored information is actively processed to a high level by selective attention systems. However, theoretical accounts of NP differ in whether they attribute the effect to processes of selective inhibition or episodic memory retrieval. Here we derived neurophysiological predictions from the rival “selective inhibition” and “episodic retrieval” models of NP, and employed event-related fMRI in a color-naming Stroop task to assess neural responses to probe trials that were subject to either no priming or negative priming. Compared to no-priming probe trials, NP resulted in increased activation of the right dorsolateral prefrontal cortex, in a region which has been closely linked with episodic memory retrieval functions. NP was also accompanied by activation of the right thalamus, particularly the mediodorsal nucleus, which has been implicated in the pathophysiology of schizophrenia, a condition associated with diminished NP effects. Our results support the proposal that ignored stimulus information is fully encoded in memory, and that episodic retrieval, not selective inhibition, of such information affects selective attention performance on subsequent trials.

Brain Mechanisms of Conscious Awareness: Detect, Pulse, Switch, and Wave

2021 ◽  
pp. 107385842110493
Author(s):  
Hal Blumenfeld
Keyword(s):  
Neural Activity ◽  
Large Scale ◽  
Memory Systems ◽  
Attention And Memory ◽  
Conscious Awareness ◽  
Conscious Perception ◽  
Discrete Events ◽  
Cortical Regions ◽  
Large Scale Networks ◽  
Experimental Findings

Consciousness is a fascinating field of neuroscience research where questions often outnumber the answers. We advocate an open and optimistic approach where converging mechanisms in neuroscience may eventually provide a satisfactory understanding of consciousness. We first review several characteristics of conscious neural activity, including the involvement of dedicated systems for content and levels of consciousness, the distinction and overlap of mechanisms contributing to conscious states and conscious awareness of transient events, nonlinear transitions and involvement of large-scale networks, and finally the temporal nexus where conscious awareness of discrete events occurs when mechanisms of attention and memory meet. These considerations and recent new experimental findings lead us to propose an inclusive hypothesis involving four phases initiated shortly after an external sensory stimulus: (1) Detect—primary and higher cortical and subcortical circuits detect the stimulus and select it for conscious perception. (2) Pulse—a transient and massive neuromodulatory surge in subcortical-cortical arousal and salience networks amplifies signals enabling conscious perception to proceed. (3) Switch—networks that may interfere with conscious processing are switched off. (4) Wave—sequential processing through hierarchical lower to higher cortical regions produces a fully formed percept, encoded in frontoparietal working memory and medial temporal episodic memory systems for subsequent report of experience. The framework hypothesized here is intended to be nonexclusive and encourages the addition of other mechanisms with further progress. Ultimately, just as many mechanisms in biology together distinguish living from nonliving things, many mechanisms in neuroscience synergistically may separate conscious from nonconscious neural activity.

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