Temporal and spatial context in the mind and brain

Howard, Marc W.

doi:10.1016/j.cobeha.2017.05.022

Cited by 33 publications

(28 citation statements)

References 67 publications

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“…Instead, we found that the MTL → PFC system was the only system that showed preferential processing of an item in time over the ongoing maintenance of item identity, revealing an MTL → PFC network that uniquely subserved working memory for both space and time. This finding is consistent with sparse evidence implicating both the MTL and the PFC in temporal memory, sequential ordering, and transitive inference (e.g., if A > B and B > C, then A > C), but the direction of interaction between these regions was not tested previously [ 37 – 40 ]. Importantly, we observed that the MTL directed the PFC during the processing of spatiotemporal information (see [ 41 ] for evidence of rodent hippocampal subregion directional connectivity to the PFC for spatial versus temporal processing), while concurrent PFC theta oscillations directed the MTL regardless of the information being processed.…”

Section: Discussionsupporting

confidence: 87%

Dynamic frontotemporal systems process space and time in working memory

et al. 2018

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How do we rapidly process incoming streams of information in working memory, a cognitive mechanism central to human behavior? Dominant views of working memory focus on the prefrontal cortex (PFC), but human hippocampal recordings provide a neurophysiological signature distinct from the PFC. Are these regions independent, or do they interact in the service of working memory? We addressed this core issue in behavior by recording directly from frontotemporal sites in humans performing a visuospatial working memory task that operationalizes the types of identity and spatiotemporal information we encounter every day. Theta band oscillations drove bidirectional interactions between the PFC and medial temporal lobe (MTL; including the hippocampus). MTL theta oscillations directed the PFC preferentially during the processing of spatiotemporal information, while PFC theta oscillations directed the MTL for all types of information being processed in working memory. These findings reveal an MTL theta mechanism for processing space and time and a domain-general PFC theta mechanism, providing evidence that rapid, dynamic MTL–PFC interactions underlie working memory for everyday experiences.

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Section: Discussionsupporting

confidence: 87%

Dynamic frontotemporal systems process space and time in working memory

et al. 2018

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“…We found that the activity of populations in the human MTL changed gradually over at least a minute, adding to a large and growing body of evidence that neural states change gradually in the MTL (Manns et al, 2007;Mankin et al, 2012;Hyman et al, 2012;Cai et al, 2016;Rashid et al, 2016; for review, see Howard, 2017). The present results suggest that these gradually changing states are recovered during retrieval of an episodic memory.…”

Section: Implications For Theory Of Hippocampus and Episodic Memorysupporting

confidence: 78%

Human Episodic Memory Retrieval Is Accompanied by a Neural Contiguity Effect

2018

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Cognitive psychologists have long hypothesized that experiences are encoded in a temporal context that changes gradually over time. When an episodic memory is retrieved, the state of context is recovered-a jump back in time. We recorded from single units in the medial temporal lobe of epilepsy patients performing an item recognition task. The population vector changed gradually over minutes during presentation of the list. When a probe from the list was remembered with high confidence, the population vector reinstated the temporal context of the original presentation of that probe during study, a neural contiguity effect that provides a possible mechanism for behavioral contiguity effects. This pattern was only observed for well remembered probes; old probes that were not well remembered showed an anti-contiguity effect. These results constitute the first direct evidence that recovery of an episodic memory in humans is associated with retrieval of a gradually changing state of temporal context, a neural "jump back in time" that parallels the act of remembering. Episodic memory is the ability to relive a specific experience from one's life. For decades, researchers have hypothesized that, unlike other forms of memory that can be described as simple associations between stimuli, episodic memory depends on the recovery of a neural representation of spatiotemporal context. During study of a sequence of stimuli, the brain state of epilepsy patients changed slowly over at least a minute. When the participant remembered a particular event from the list, this gradually changing state was recovered. This provides direct confirmation of the prediction from computational models of episodic memory. The resolution of this point means that the study of episodic memory can focus on the mechanisms by which this representation of spatiotemporal context is maintained and sometimes recovered.

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“…First, in addition to stimulus-evoked activity, the activity of some neurons involved in episodic memory should also change gradually over time. This prediction aligns with a large body of animal work showing that neural ensembles in the hippocampus, amygdala and prefrontal cortex change slowly over time scales up to at least tens of minutes (Manns, Howard, & Eichenbaum, 2007;Hyman, Ma, Balaguer-Ballester, Durstewitz, & Seamans, 2012;Mankin et al, 2012;MacDonald, Lepage, Eden, & Eichenbaum, 2011;Salz et al, 2016;Rubin, Geva, Sheintuch, & Ziv, 2015;Cai et al, 2016;Rashid et al, 2016;Howard, 2017). Second, during retrieval of an existing memory, the prior state (temporal context) associated with an episodic memory should be restored.…”

Section: Introductionsupporting

confidence: 78%

Human episodic memory retrieval is accompanied by a neural contiguity effect

Folkerts

Rutishauser

Howard

2017

Preprint

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Cognitive psychologists have long hypothesized that experiences are encoded in a temporal context that changes gradually over time. When an episodic memory is retrieved, the state of context is recovered-a jump back in time. We recorded from single units in the MTL of epilepsy patients performing an item recognition task. The population vector changed gradually over minutes during presentation of the list. When a probe from the list was remembered with high confidence, the population vector reinstated the temporal context of the original presentation of that probe during study-a neural contiguity effect that provides a possible mechanism for behavioral contiguity effects. This pattern was only observed for well-remembered probes; old probes that were not well-remembered showed an anti-contiguity effect. These results constitute the first direct evidence that recovery of an episodic memory in humans is associated with retrieval of a gradually-changing state of temporal context-a neural "jump-back-in-time" that parallels the act of remembering. Significance statement. Episodic memory is the ability to re-live a specific experience from one's life. For decades, researchers have hypothesized that, unlike other forms of memory that can be described as simple associations between stimuli, episodic memory depends on the recovery of a neural representation of spatiotemporal context. During study of a sequence of stimuli, the brain state of epilepsy patients changed slowly over at least a minute. When the participant remembered a particular event from the list, this gradually-changing state was recovered. This provides direct confirmation of the prediction from computational models of episodic memory. The resolution of this point means that the study of episodic memory can focus on the mechanisms by which this representation of spatiotemporal context is maintained and, sometimes recovered.

show abstract

Temporal and spatial context in the mind and brain

Cited by 33 publications

References 67 publications

Dynamic frontotemporal systems process space and time in working memory

Dynamic frontotemporal systems process space and time in working memory

Human Episodic Memory Retrieval Is Accompanied by a Neural Contiguity Effect

Human episodic memory retrieval is accompanied by a neural contiguity effect

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