[Conditioned reflex changes in the functional connections between adjacent and remote cortical neurons].

Abstract

A motor conditioned reflex to sound was elaborated in cats with electrodes (nichrome wire dia 50 mcm) chronically implanted in the auditory cortex. Multineuronal activity preceding by 30 s the conditioned signal was analysed. Impulse activity of two to three neurones was isolated from every record by means of an amplitude discriminator. Dependence between impulse series isolated either from one record or from records obtained with two electrodes placed at a distance of up to 200 mcm from one another, was estimated by crossover interval histograms. Consequently functional connections between neurones were defined by the dependence of impulse series. In the process of conditioning dynamic reorganization of interneuronal connections was revealed. With a stable reflex, the number of connections both between neurons in the microregion and between neurones of neighbouring microregions considerably increased due to an increased number of excitatory connections. After extinction of the reflex, the number of connections between adjacent neurons increased still more, though due to enhancement of the inhibitory type connections. Nonetheless, excitatory connections kept dominating. At the same time, the number of connections between neurons of the neighbouring microsystems sharply decreased.