[Reactions of neurons in the associative thalamic nuclei to peripheral stimulation of different modality]

Reactions of 252 neurons of the mediodorsal nucleus (MD) and 329 cells of the pulvinar-posterior-lateral complex (Pulv-LP) of the thalamus to separate the complex peripheral stimulations (visual, auditory and somatosensory) were studied in acute experiments on cats anaesthetized with a mixture of chloralose and nembutal. According to the character of the neuronal responses to peripheral stimuli three types of reactions were found: acceleration of the background activity (32.0% neurons in Pulv-LP and 20.6% in MD), inhibition (21.0% neurons in Pulv-LP and 24.2% in MD) and mixed (8.8% neurons in Pulv-LP and 4.0% in MD). No responses were observed in 37.4% neurons of Pulv-LP and in 51.2% of MD. Along with certain similarity, some specific features in the organization of Pulv-LP and MD were found. According to the response latency, the neuronal reactions to stimulation were divided into three groups: with short (less than 20 ms), medium (21--40 ms) and long (over 41 ms) latent period. The second group was the most numerous.