Towards a functional organization of episodic memory in the medial temporal lobe

Eichenbaum, Howard; Sauvage, Magdalena; Fortin, Norbert J.; Komorowski, Robert W.; Lipton, Paul A.

doi:10.1016/j.neubiorev.2011.07.006

Cited by 326 publications

(280 citation statements)

References 124 publications

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“…In conclusion, sequence cell activity is consistent with a fundamental role of the hippocampus in supporting the integration of information about specific items or events with the spatial and temporal context in which they occurred, a function critical to episodic memory (Eichenbaum et al, 2012;Allen and Fortin, 2013;Howard and Eichenbaum, 2015;Knierim, 2015). The present study…”

Section: Discussionsupporting

confidence: 82%

“…More specifically, the hippocampus, which receives a strong convergence of input from cortical regions, is thought to play a key role in associating information about specific events with the spatial and temporal contexts in which they occurred (Eichenbaum et al, 2012;Allen and Fortin, 2013;Howard and Eichenbaum, 2015;Knierim, 2015). Consistent with this view, neurons in hippocampal subregion CA1 have shown selectivity for specific stimuli, spatial locations, as well as specific time periods or temporal relationships (e.g., Wood et al, 1999;MacDonald et al, 2011;Igarashi et al, 2014b;Allen et al, 2016).…”

Section: Introductionmentioning

confidence: 91%

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Nonspatial sequence coding varies along the CA1 transverse axis

Elias

Asem

et al. 2018

Behavioural Brain Research

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The hippocampus plays a critical role in the memory for sequences of events, a defining feature of episodic memory. To shed light on the fundamental mechanisms supporting this capacity, we recently recorded neural activity in CA1 as rats performed a nonspatial odor sequence memory task. Our main finding was that, while the animals' location and behavior remained constant, a proportion of CA1 neurons fired differentially to odors depending on whether they were presented in or out of sequence (sequence cells). Here, we further examined if such sequence coding varied along the distal-to-proximal axis of the dorsal CA1 region (distal: toward subiculum; proximal: toward CA3). Differences in information processing along this axis have been suggested by recent anatomical and electrophysiological evidence that odor information may be more strongly represented in the distal segment, whereas spatial information may be more strongly represented in the proximal segment. Recorded neurons were grouped into four arbitrary sections of dorsal CA1, ranging from distal to proximal. We found that, although sequence cell coding was observed across the distal-to-proximal extent of CA1 from which we recorded, it was significantly higher in intermediate CA1, a region with more balanced anatomical input from lateral and medial entorhinal regions. More specifically, in that particular segment of CA1, we observed a significant increase in the magnitude of sequence coding of all cells, as well as in the sequential information content of sequence cells. Importantly, a different pattern was observed when examining the distribution of spatial coding from the same electrodes. Consistent with previous reports, our results suggest that spatial information was more strongly represented in the proximal section of CA1 (higher proportion of cells with place fields). These findings indicate that nonspatial sequence memory coding is not uniformly distributed along the transverse axis of CA1, and that this distribution does not simply follow the expected gradient based on the stimulus modality or the degree of spatial selectivity. Instead, the observed distribution suggests this form of sequence coding may be associated with convergent input from lateral and medial entorhinal regions, which is present throughout the proximodistal axis but higher in intermediate CA1.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 91%

Nonspatial sequence coding varies along the CA1 transverse axis

Elias

Asem

et al. 2018

Behavioural Brain Research

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“…Given that this projection conveys semantic ("what is it") information to hippocampus (Eichenbaum et al 2012;Reagh and Yassa 2014), the findings are of basic importance to Figure 6. Learning of cues conveyed by the LPP produces synaptic effects associated with lppLTP.…”

Section: Discussionmentioning

confidence: 91%

“…It is widely held that through this circuitry the hippocampus converts a sequence of inputs from cortex into representations that include semantic, spatial, and temporal components (Aggleton and Brown 1999;Eichenbaum 2000). Multiple studies suggest that transmission of this code back to cortex is essential for the construction and retrieval of episodic memory, a fundamental ingredient of orderly thought (Eichenbaum et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Atypical Endocannabinoid Signaling Initiates a New Form of Memory-Related Plasticity at a Cortical Input to Hippocampus

et al. 2017

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Endocannabinoids (ECBs) depress transmitter release at sites throughout the brain. Here, we describe another form of ECB signaling that triggers a novel form of long-term potentiation (LTP) localized to the lateral perforant path (LPP) which conveys semantic information from cortex to hippocampus. Two cannabinoid CB 1 receptor (CB 1 R) signaling cascades were identified in hippocampus. The first is pregnenolone sensitive, targets vesicular protein Munc18-1 and depresses transmitter release; this cascade is engaged by CB 1 Rs in Schaffer-Commissural afferents to CA1 but not in the LPP, and it does not contribute to LTP. The second cascade is pregnenolone insensitive and LPP specific; it entails co-operative CB 1 R/β1-integrin signaling to effect synaptic potentiation via stable enhancement of transmitter release. The latter cascade is engaged during LPP-dependent learning. These results link atypical ECB signaling to the encoding of a fundamental component of episodic memory and suggest a novel route whereby endogenous and exogenous cannabinoids affect cognition.

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“…[1][2][3] Effects of stress on cognition are complex and depend on factors including the nature, duration and timing of stress, and the specific cognitive task employed. [4][5][6] The hippocampus contributes greatly to memory, 7,8 and it has been increasingly recognized that processing of sensory signals into memories in rodents involves dorsal hippocampus networks. 9,10 In contrast, ventral hippocampus is endowed with distinct afferent/efferent connections 9,11 including robust pathways to amygdala, 12,13 which may enhance the emotional salience of memories.…”

Section: Introductionmentioning

confidence: 99%