Consolidation of memory

Abstract

Animal studies have proven useful in addressing aspects of memory formation and consolidation that cannot be readily answered in research with humans. In particular, they offer the possibility of controlling both the extent and locus of brain lesions, and the exact nature of the experiences to be remembered. Taking advantage of these possibilities, recent studies indicated that the graded retrograde amnesia often seen after lesions to the hippocampal system is not uniform across lesion site and task, nor is it an indication that all of the remembered information available in intact subjects becomes available after hippocampal system lesions made a long time after learning. Rather, these studies support the notion that information is stored in both hippocampal and extrahipocampal sites, and that retrieval from different sites involves access to different kinds of information. The strongest evidence in support of this view is the set of findings indicating that when remote memories are retrieved, in either human or animal subjects that have suffered hippocampal system damage, these memories are not qualitatively the same as remote memories retrieved in intact subjects. In sum, memory appears to be rather more dynamic than most current conceptions allow, such that retrieval events trigger new encodings, and these new encodings engage the hippocampal system once again. As a result, older, reactivated memories become more resistant to disruption, and this mechanism helps to explain why graded retrograde amnesia is sometimes seen after brain damage. The use of new neuroimaging techniques, coupled with more sensitive neuropsychological tests in lesioned subjects, should further illuminate the complex nature of memory in coming years. It is likely that animal studies will continue to prove important in these developments. Hippocampus 2001;11:56–60. © 2001 Wiley‐Liss, Inc.

The Role of the Hippocampus in Long-Term Memory: Is It Memory Store or Comparator?

“…compared to the earlier traces [3,10,18,28,59,181,240,242], and in rats this is also true in the event of complete hippocampal lesions [30,270].…”

The Role of the Hippocampus in Long-Term Memory: Is It Memory Store or Comparator?

“…compared to the earlier traces [3,10,18,28,59,181,240,242], and in rats this is also true in the event of complete hippocampal lesions [30,270].…”

ERK2 and CREB activation in the amygdala when an event is remembered as “Fearful” and not when it is remembered as “Instructive”

“…Thus it is possible that, because of the relatively long training protocol that we employed, the locus of activation had moved from the hippocampus to another limbic or cortical area. This possibility is also supported by findings from amnesic patients and from models of amnesia (Mishkin et al, 1998;Jarrard, 2001;Nadel and Bohbot, 2001), which suggest that, with time, the role of the hippocampus in the memory formed is reduced, until the memory becomes independent of hippocampal activity and resistant to hippocampal damage.…”

The COST of explicit memory

“…The "relative" line is a measure of amnesic performance adjusted relative to normal subject performance (since normal memory also improves as events recede into the past; after Brown 2002) Based on his 1997 work, Weiskrantz yet holds to this position -any memory task that requires the present × past product is seen as being at risk. Nadel and Bohbot (2001) have voiced similar reservations. In the consolidation view, the hippocampus is only temporarily critical.…”

The Role of the Hippocampus in Long-Term Memory: Is It Memory Store or Comparator?

“…compared to the earlier traces [3,10,18,28,59,181,240,242], and in rats this is also true in the event of complete hippocampal lesions [30,270].…”

ERK2 and CREB activation in the amygdala when an event is remembered as “Fearful” and not when it is remembered as “Instructive”

“…Thus it is possible that, because of the relatively long training protocol that we employed, the locus of activation had moved from the hippocampus to another limbic or cortical area. This possibility is also supported by findings from amnesic patients and from models of amnesia (Mishkin et al, 1998;Jarrard, 2001;Nadel and Bohbot, 2001), which suggest that, with time, the role of the hippocampus in the memory formed is reduced, until the memory becomes independent of hippocampal activity and resistant to hippocampal damage.…”

The COST of explicit memory

“…The "relative" line is a measure of amnesic performance adjusted relative to normal subject performance (since normal memory also improves as events recede into the past; after Brown 2002) Based on his 1997 work, Weiskrantz yet holds to this position -any memory task that requires the present × past product is seen as being at risk. Nadel and Bohbot (2001) have voiced similar reservations. In the consolidation view, the hippocampus is only temporarily critical.…”

The Role of the Hippocampus in Long-Term Memory: Is It Memory Store or Comparator?

“…compared to the earlier traces [3,10,18,28,59,181,240,242], and in rats this is also true in the event of complete hippocampal lesions [30,270].…”

ERK2 and CREB activation in the amygdala when an event is remembered as “Fearful” and not when it is remembered as “Instructive”

“…Thus it is possible that, because of the relatively long training protocol that we employed, the locus of activation had moved from the hippocampus to another limbic or cortical area. This possibility is also supported by findings from amnesic patients and from models of amnesia (Mishkin et al, 1998;Jarrard, 2001;Nadel and Bohbot, 2001), which suggest that, with time, the role of the hippocampus in the memory formed is reduced, until the memory becomes independent of hippocampal activity and resistant to hippocampal damage.…”

The COST of explicit memory

“…The "relative" line is a measure of amnesic performance adjusted relative to normal subject performance (since normal memory also improves as events recede into the past; after Brown 2002) Based on his 1997 work, Weiskrantz yet holds to this position -any memory task that requires the present × past product is seen as being at risk. Nadel and Bohbot (2001) have voiced similar reservations. In the consolidation view, the hippocampus is only temporarily critical.…”