Consolidating new memories requires the amygdala and

After Molaison underwent a bilateral medial temporal lobe resection to alleviate epileptic symptoms the patient began to suffer from memory impairments.

The case of Henry Molaison, formerly known as patient H.

M., became a landmark in studies of memory as it relates to amnesia and the removal of the hippocampal zone and sparked massive interest in the study of brain lesions and their effect on memory.

Molaison also showed signs of retrograde amnesia spanning a period of about 3 years prior to the surgery suggesting that recently acquired memories of as long as a couple years could remain in the MTL prior to consolidation into other brain areas.

Research into other patients with resections of the MTL have shown a positive relationship between the degree of memory impairment and the extent of MTL removal which points to a temporal gradient in the consolidating nature of the MTL.

Long-term memory, when discussed in the context of synaptic consolidation, is memory that lasts for at least 24 hours.

An exception to this 24-hour rule is long-term potentiation, or LTP, a model of synaptic plasticity related to learning, in which an hour is thought to be sufficient.The result of the gene expression is the lasting alteration of synaptic proteins, as well as synaptic remodeling and growth.In a short time-frame immediately following learning, the molecular cascade, expression and process of both transcription factors and immediate early genes, are susceptible to disruptions.In recent decades, advancements in cellular preparations, molecular biology, and neurogenetics have revolutionized the study of consolidation.Providing additional support is the study of functional brain activity in humans which has revealed that the activity of brain regions changes over time after a new memory is acquired.Distributed learning has been found to enhance memory consolidation, specifically for relational memory.

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