No abstract

The identification of local detectors, command neurons, and modulator neurons has opened up the possibility of the structural identification of individual synaptic contacts supporting the functioning of the reflex arc. Nonassociative plasticity (habituation and sensitization) are [sic] realized at the level of the receptors and potential-dependent calcium channels through dephosphorylation-phosphorylation of receptor and channel proteins. Associative plasticity (the development and extinction of the conditioned reflex) includes two levels of regulation: short-term (through dephosphorylation-phosphorylation of receptor and channel proteins) and long-term (through the expression of genes coding structural and translocational genes). Its selectivity is an extremely important characteristic of associative plasticity. The mechanism of associative plasticity is based on the principles of the Hebb plastic synapse, supplemented by indication of the role of nonspecific (modulating) influences.

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This review discusses the information content of perceptual and semantic evoked potentials arising in humans as a result of instantaneous changes in nonverbal and verbal stimuli. The amplitudes of perceptual and semantic evoked potentials were found to correlate positively with subjects' assessments of the differences between these stimuli. Multidimensional scaling matrixes of evoked potential amplitudes and subjective assessments of differences on pairwise substitution of stimuli showed that the actual colors and color names occupied a four-dimensional spherical color space and were encoded by excitation vectors of identical lengths. Color differences were equal to the absolute differences between their excitation vectors, while semantic differences in color names corresponded to the absolute difference vectors represented by long-term color memory traces. These data were reviewed in the framework of a spherical model of cognitive processes.