Memory processes

Fig. 2. The shape-memory process, where Tis temperature, (a) The cycle where the parent phase undergoes a self-accommodating martensite transformation on cooling to the 24 variants of martensite. No macroscopic shape change occurs. The variants coalesce under stress to a single martensite variant, resulting in deformation. Then, upon heating, they revert back to the original austenite crystallographic orientation, and reverse transformation, undergoing complete recovery to complete the cycle, (b) Shape deformation. Strain recovery is typically ca 7%.

CaM plays a key role in many cellular processes. In the CNS, it is involved in synaptic transmission and neuronal plasticity associated with short-term and longterm potentiation, and learning and memory processes. 

Even if there is a link between the presence of tangles and plaques and the emergence of AzD, it is by no means certain how those markers could be responsible for all the symptoms. They do not seem to be sufficiently numerous or widely spread to disrupt brain function to the extent that eventually occurs in AzD, although their preferential location in the hippocampus and the known association of that area with memory processing could explain the loss of that faculty. 

NEUROTRANSMITTERS IN MEMORY PROCESSING AND APPROPRIATE SYNAPTIC FUNCTION... 

Since ACh appears to be important in memory processing and as its concentration is significantly reduced in appropriate brain areas in AzD then augmenting its action should at least improve memory function. ACh activity may be increased by... 

Apart from this paradoxical exception, it is clear that at higher doses alcohol intoxication is associated with impaired performance across a range of tasks involving psychomotor, attentional and memory processing. At moderate to high doses, alcohol impairs the formation of new memories and disrupts working memory. However, established memory is left relatively unimpaired, suggesting that... 

Messier C, Pierre J, Desrochers A and Gravel M (1998). Dose-dependent action of glucose on memory processes in women Effect on serial position and recall priority. Brain Research Cognition, 7, 221-233. 

While the conditional gene knockout experiments are supportive of a role for the NMDA receptors in memory, they are less than fully conclusive in linking the synaptic coincidence-detection feature of the NMDA receptor to memory formation. Like all loss-of-function studies, CA1-specific gene-knockout experiments could, in theory, produce memory impairment via a mechanism independent of the coincidence-detection function of the NMDA receptor. For example, one may argue that the physical absence of the NMDA receptor channels may cause subtle structural reconfiguration at the synapse, thereby altering normal synaptic transmission. Therefore, the memory impairment in CA1-specific NR1 knockout mice does not allow a firm conclusion that the coincidence-detection function of NMDA receptors controls learning and memory processes at the cellular level. 

Wittenberg, G. M. and Tsien, I. Z. An emerging molecular and cellular framework for memory processing by the hippocampus. Trends Neurosci. 25 501-505,2002. 

A few studies have been performed with event-related potentials (ERP) to examine the cognitive effects of THC. In subjects viewing emotionally valenced words (neutral, negative, or positive), THC produced a behavioral decrease in recognition rate (Leweke et al. 1998). The ERPs showed the typical difference between old and new words (enhanced positivity for old words beginning 250 milliseconds poststimulus), and THC enhanced the positivity in response to old words. This counterintuitive dissociation between ERPs and behavioral indices was interpreted as a reflection of implicit memory processes underlying the ERP effect. 

Gallagher M, Kapp B. 1981. Effects of phentolamine administration into the amygdala complex of rats on time-dependent memory processes. Behav Neural Biol 31(1) 90-95. 

The massive amyloid deposition in the form of parenchymal plaques and/or in cerebrovascular amyloid (cerebral amyloid angiopathy) is associated with neuronal loss and dysfunction. In particular the cholinergic neurons of the basal forebrain, which are involved in the memory processes, are affected and neuron loss in these nuclei accounts for some of the AD symptoms. 

Sitaram N, Weingartner H, GiUinJC, Physostigmine, improvement oflong-term memory processes in normal humans. Science 201 272—276, 1978. 

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