Correlations of neuronal spike discharges of VL neurons during spontaneous firing and during the activity evoked by peripheral stimulation.

The temporal relations between simultaneously recorded neurons of the nucleus ventralis lateralis (VL) of cat thalamus were studied. The interaction and the functional connections between individual VL neurons are described. This was achieved with an application of cross correlation techniques. The response patterns of different individual neurons to somatic sensory and photic stimuli were also analyzed. For the purpose of classifying neurons as thalamocortical relay cells (T-C) and non relay cells (N-C) which do not project to the motor sensory cortex antidromic cortical stimulation was used. This stimulation was also used as conditioning one when proceeded peripheral stimuli. To analyze the nonspecific specific interactions upon single neurons conditioning photic stimuli were applied. The results show that T-C neurons are antidromically excited from a wide cortical areas and that the functional interaction between T-C neurons is mediated by a shared input from common sources. It is further postulated that N-C cells interposed between relay neurons subserve the functions of gating units modifying the neuronal network of lateral ventral nucleus of the thalamus.