[Responses of the vibrissal projection zone of the cat somatosensory projection zone to afferent activation].

Responses of 375 neurons of SI cortex region in the vibrissae projection zone were recorded in unanesthetized cats: responses to electrical stimulation of infraorbital nerve and mechanical stimulation of vibrissae were studied. Nerve and vibrissae stimulation evoked complex synaptic potentials (short EPSPs followed by IPSPs) in most neurons primary IPSPs were found in other units. The corresponding changes of impulse activity could be recorded in many neurons extracellularly. Initial inhibition was evoked by vibrissae stimulation more frequently (in 45% units comparing to 16% when the nerve was stimulated). Difference of minimal EPSP and IPSP latencies during intraorbital nerve stimulation was 0.8 ms, difference of mean values--1.4 ms. Directional sensitivity of cortical neurons (to the changes in direction of vibrissae deflection) is demonstrated. Neurons located in the close proximity may possess different pattern of directional sensitivity. It is supposed that short latency neuronal inhibition in SI cortical zone is mainly afferent (not recurrent). Probable mechanisms of directional sensitivity of the studied neurons are discussed.