Synaptic plasticity and learning and memory: LTP and beyond

Abstract

Long-term potentiation (LTP) of synaptic activity is by far the most popular and widely researched model of synaptic plastic changes that might occur during learning. Numerous recent reports, however, have not found a correlation between the inducibility of LTP in the hippocampus and the ability of animals to learn hippocampus-dependent tasks. For example, some experiments with gene deletion (knockout) mice strains have shown that in some strains LTP is not inducible in the dentate gyrus, in area CA3, or CA1, but the animals are still able to learn spatial tasks. This apparent mismatch has rejuvenated the discussion concerning whether LTP is a good model for mechanisms that underlie memory formation in the nervous system. This review analyzes the conditions under which LTP is induced or learning takes place and suggests reasons for the mismatches that can occur and what we can learn from them. High-frequency stimulation protocols and in vitro assays cannot be seen to resemble natural firing patterns or conditions found in the brain. More physiological experimental conditions, especially in vivo recording in awake animals, could lead the way to the development of improved models of learning mechanisms that better correlate with learning abilities of animals.

Modulation of Hippocampal Plasticity and Cognitive Behavior by Short-term Blueberry Supplementation in Aged Rats

“…While precursor cells at the stage examined, have not yet differentiated into mature phenotypes (Fig. 2C), such immature cells, produced in the hiliar region of the dentate gyrus (Kuhn et al, 1996), show greater long-term potentiation, a feature closely associated with neuronal plasticity and improvements in hippocampally-related cognitive behavior (Laroche et al, 1995, Richter-Levin et al, 1995, Holscher 1999) more readily than mature granule cells . Therefore, these findings support the notion that proliferation itself may be capable of improving spatial memory and learning in the blueberry-supplemented animals.…”

Activity Deprivation Leads to Seizures in Hippocampal Slice Cultures: Is Epilepsy the Consequence of Homeostatic Plasticity?

“…Loss of this control can lead to seizures and epilepsy. Although control of excitability is a highly complex cellular property (Hille, 2001), plasticity of excitability has been traditionally measured either as a change in synaptic efficacy (Baudry, 1998;Gerber et al, 2004;Holscher, 1999;Lisman and McIntyre, 2001;Martin et al, 2000;Tsodyks 2002), intrinsic excitability (Aizenman et al, 2003;Aizenman and Linden, 2000;Armano et al, 2000;Daoudal and Debanne 2003;Frick et al, 2004;Him and Dutia, 2001), or a combinatorial effect of intrinsic, synaptic and/or neuromodulatory effects (Cantrell and Catterall, 2001;Cantrell et al, 1999;Frick et al, 2004;Mansvelder et al, 2002;van Welie et al, 2004).…”

Mechanism of Action of Low Dose Preparations from <i>Coffea arabica</i>, <i>Gelsemium</i> and <i>Veratrum</i> Based on <i>in Vivo</i> and <i>in Vitro</i> Neurophysiological Findings

“…Since the effect was not only observed during single stimuli but also during theta burst stimulation, the resulting increase of long term potentiation as induced by this stimulation pattern leads to the conclusion that time and space dependent memory processes should be improved in the presence of Coffea. For discussion of LTP in the literature see [31].…”