Dynamics of the single unit reactions in the visual cortex of the unanesthetized rabbit

The impulse activity of the visual neurons of an unanaesthetized rabbit was-recorded with the help of tungsten microelecirodes. According to the character of the background activity. the neurons are divided in 4 groups. The responses to a flash are determined by the correlation of the phases of excitation and inhibition; on this basis the neurons are divided into excitatory, excitatory-inhibitory, inhibitory, inhibitory-excitatory and non-responsive groups. The action of a sound (a click, the noise of the motor of a “recordina”) is characterized mainly by inhibition of both the background and the light-evoked activities. During rhythmic repetitions of the flashes the responses of the visual neurons manifest a marked stability. The following forms of dynamic changes taking place during repetitions of the light flashes, as well as of the complex of a click - a flash were established: stabilization of the responses (20.7 per cent): partial extinction (about 17 per cent); intensification (5 per cent): conditioning to time (10 per cent): sound and light association (8 per cent). The repeated presentations of a sound stimulus result in a complete extinction of the neuronal responses. The data obtained are explained as a convergence of specific and nonspecific influences on the visual neurons. It is supposed that conditioning on the neuronal level is due to a particular type of convergence, namely, “plastic convergence”. The data obtained refer to the sensory interaction studied at psychophysiological level. Sur le lapin non anesthésié. on enregistre les impulsions d'activitédes neurones visuels avec des microélectrodes en tungsténe. On divise ces neurones en 4 groupes selon le caractére de l'activitédu fond. On détermine les réponsesàunéclair lumineux en liaison avec les phases de l'excitation et de l'inhibition. Sur cette base on divise les neurones en groupes d'excitation, excitation-inhibition. inhibition, inhibition-excitation, et absence de réponse. L'effet d'un bruit (craquement ou bruit de moteur) se caractérise surtout par l'inhibition des activités, tant du fond qu'évoquées par la lumière. Pendant des répétitions rythmiques d'éclairs, les réponses des neurones visuels manifestent une stabilitétrès marquée. On a distinguéles formes suivantes de changements dynamiques qui se produisent durant des répétitions d'éclairs lumineux, aussi bien que du complexe craquement —éclair: stabilisation des réponses (20,7%). extinction partielle (environ 17%). intensific