The fasciola cinereum subregion of the hippocampus is important for the acquisition of visual contextual memory

Memory retrieval dysfunction is a symptom of schizophrenia, autism spectrum disorder (ASD), and absence epilepsy (AE), as well as an early sign of Alzheimer’s disease. To date, few drugs have been reported to enhance memory retrieval. Here, we found that a coral-derived natural product, excavatolide-B (Exc-B), enhances contextual memory retrieval in both wild-type and Cav3.2−/− mice via repressing the delayed rectifier potassium current, thus lowering the threshold for action potential initiation and enhancing induction of long-term potentiation (LTP). The human CACNA1H gene encodes a T-type calcium channel (Cav3.2), and its mutation is associated with schizophrenia, ASD, and AE, which are all characterized by abnormal memory function. Our previous publication demonstrated that Cav3.2−/− mice exhibit impaired contextual-associated memory retrieval, whilst their retrieval of spatial memory and auditory cued memory remain intact. The effect of Exc-B on enhancing the retrieval of context-associated memory provides a hope for novel drug development.

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A possible role of astrocytes in contextual memory retrieval: An analysis obtained using a quantitative framework

Frontiers in Computational Neuroscience ◽

10.3389/fncom.2013.00145 ◽

2013 ◽

Vol 7 ◽

Cited By ~ 17

Author(s):

Shivendra Tewari ◽

Vladimir Parpura

Keyword(s):

Memory Retrieval ◽

Contextual Memory

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Novel Scenes Improve Recollection and Recall of Words

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2008.20086 ◽

2008 ◽

Vol 20 (7) ◽

pp. 1250-1265 ◽

Cited By ~ 38

Author(s):

Daniela B. Fenker ◽

Julietta U. Frey ◽

Hartmut Schuetze ◽

Dorothee Heipertz ◽

Hans-Jochen Heinze ◽

...

Keyword(s):

Specific Activity ◽

Activity Patterns ◽

Long Term Potentiation ◽

Contextual Memory ◽

Memory Enhancement ◽

Term Potentiation ◽

Outdoor Scenes ◽

Indoor And Outdoor ◽

Hippocampus Dependent Memory

Exploring a novel environment can facilitate subsequent hippocampal long-term potentiation in animals. We report a related behavioral enhancement in humans. In two separate experiments, recollection and free recall, both measures of hippocampus-dependent memory formation, were enhanced for words studied after a 5-min exposure to unrelated novel as opposed to familiar images depicting indoor and outdoor scenes. With functional magnetic resonance imaging, the enhancement was predicted by specific activity patterns observed during novelty exposure in parahippocampal and dorsal prefrontal cortices, regions which are known to be linked to attentional orienting to novel stimuli and perceptual processing of scenes. Novelty was also associated with activation of the substantia nigra/ventral tegmental area of the midbrain and the hippocampus, but these activations did not correlate with contextual memory enhancement. These findings indicate remarkable parallels between contextual memory enhancement in humans and existing evidence regarding contextually enhanced hippocampal plasticity in animals. They provide specific behavioral clues to enhancing hippocampus-dependent memory in humans.

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Nucleus reuniens is required for encoding and retrieving precise, hippocampal-dependent contextual fear memories in rats

10.1101/340190 ◽

2018 ◽

Author(s):

Karthik R. Ramanathan ◽

Reed L. Ressler ◽

Jingji Jin ◽

Stephen Maren

Keyword(s):

Prefrontal Cortex ◽

Spatial Memory ◽

Fear Conditioning ◽

Medial Prefrontal Cortex ◽

Thalamic Nucleus ◽

Nmda Receptor Antagonist ◽

Pavlovian Fear Conditioning ◽

Contextual Memory ◽

Nucleus Reuniens ◽

Contextual Fear

AbstractThe nucleus reuniens (RE) is a ventral midline thalamic nucleus that interconnects the medial prefrontal cortex (mPFC) and hippocampus (HPC). Considerable data indicate that HPC-mPFC circuits are involved in contextual and spatial memory; however, it is not clear whether the RE mediates the acquisition or retrieval of these memories. To examine this question, we inactivated the RE with muscimol before either the acquisition or retrieval of Pavlovian fear conditioning in rats; freezing served as the index of fear. We found that RE inactivation before conditioning impaired the acquisition of contextual freezing, whereas inactivation of the RE prior to retrieval testing increased the generalization of freezing to a novel context; inactivation of the RE did not affect either the acquisition or expression of auditory fear conditioning. Interestingly, contextual conditioning impairments were absent when retrieval testing was also conducted after RE inactivation. Contextual memories acquired under RE inactivation were hippocampal-independent, insofar as contextual freezing in rats conditioned under RE inactivation was insensitive to intra-hippocampal infusions of the NMDA receptor antagonist, D,L-amino-5-phosophonovaleric acid (APV). Together, these data reveal that the RE supports hippocampal-dependent encoding of precise contextual memories that allow discrimination of dangerous from safe contexts. When the RE is inactive, however, alternate neural systems acquire an impoverished contextual memory that is only expressed when the RE is offline.SIGNIFICANCE STATEMENTThe midline thalamic nucleus reuniens (RE) coordinates communication between the hippocampus and medial prefrontal cortex, brain areas critical for contextual and spatial memory. Here we show that temporary pharmacological inactivation of RE impairs the acquisition and precision of contextual fear memories after Pavlovian fear conditioning in rats. However, inactivating the RE prior to retrieval testing restored contextual memory in rats conditioned after RE inactivation. Critically, we show that imprecise contextual memories acquired under RE inactivation are learned independently of the hippocampus. These data reveal that the RE is required for hippocampal-dependent encoding of precise contextual memories to support the discrimination of safe and dangerous contexts.

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