<P> Systematic studies of anterograde amnesia started to emerge in the 1960s and 1970s . 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 . After Molaison underwent a bilateral medial temporal lobe resection to alleviate epileptic symptoms the patient began to suffer from memory impairments . Molaison lost the ability to encode and consolidate newly learned information leading researchers to conclude the medial temporal lobe (MTL) was an important structure involved in this process . 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 . </P> <P> These studies were accompanied by the creation of animal models of human amnesia in an effort to identify brain substrates critical for slow consolidation . Meanwhile, neuropharmacological studies of selected brain areas began to shed light on the molecules possibly responsible for fast consolidation . 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 . This change can occur as quickly as a couple hours after the memory has been encoded suggesting that there is a temporal dimension to the reorganization of the memory as it is represented in the brain . </P> <P> Synaptic consolidation, or late - phase LTP, is one form of memory consolidation seen across all species and long - term memory tasks . 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 . Synaptic consolidation is achieved faster than systems consolidation, within only minutes to hours of learning in goldfish . LTP, one of the best understood forms of synaptic plasticity, is thought to be a possible underlying process in synaptic consolidation . </P> <P> The standard model of synaptic consolidation suggests that alterations of synaptic protein synthesis and changes in membrane potential are achieved through activating intracellular transduction cascades . These molecular cascades trigger transcription factors that lead to changes in gene expression . 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 . Disruptions caused by specific drugs, antibodies and gross physical trauma can block the effects of synaptic consolidation . </P>

Memory consolidation and reconsolidation what is the role of sleep