Neurobiology of learning and memory
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Neurobiol Learn Mem · Oct 2012
Dissociation between memory reactivation and its behavioral expression: scopolamine interferes with memory expression without disrupting long-term storage.
The reconsolidation hypothesis has challenged the traditional view of fixed memories after consolidation. Reconsolidation studies have disclosed that the mechanisms mediating memory retrieval and the mechanisms that underlie the behavioral expression of memory can be dissociated, offering a new prospect for understanding the nature of experimental amnesia. The muscarinic antagonist scopolamine has been used for decades to induce experimental amnesias The goal of the present study is to determine whether the amnesic effects of scopolamine are due to storage (or retrieval) deficits or, alternatively, to a decrease in the long-term memory expression of a consolidated long-term memory. ⋯ This recovery of memory expression was reconsolidation specific since a reminder that does not triggers reconsolidation process did not allow the recovery. A higher dose (5 μg/g) of scopolamine induced an amnesic effect that could not be reverted through reconsolidation, and thus it can be explained as an interference with memory storage and/or retrieval mechanisms. These results, showing that an effective amnesic dose of scopolamine (100 ng/g) negatively modulates long-term memory expression but not memory storage in the crab Chasmagnathus, are consistent with the concept that dissociable processes underlie the mechanisms mediating memory reactivation and the behavioral expression of memory.
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Neurobiol Learn Mem · Oct 2012
Maternal deprivation induces deficits in temporal memory and cognitive flexibility and exaggerates synaptic plasticity in the rat medial prefrontal cortex.
Early life adverse events can lead to structural and functional impairments in the prefrontal cortex (PFC). Here, we investigated whether maternal deprivation (MD) alters PFC-dependent executive functions, neurons and astrocytes number and synaptic plasticity in adult male Long-Evans rats. The deprivation protocol consisted of a daily separation of newborn Long-Evans pups from their mothers and littermates 3h/day postnatal day 1-14. ⋯ In parallel, MD induced in the prelimbic area of the medial PFC an upregulation of long-term potentiation (LTP), without any change in the number of neurons and astrocytes. We provide evidence that MD leads in adults to an alteration of the cognitive abilities dependent on the PFC, and to an exaggerated synaptic plasticity in this region. We suggest that this latter phenomenon may contribute to the impairments in the cognitive tasks.