Specific and non-specific inhibition induced by LP-pulvinar inputs to area 7 of the rhesus monkey.

Evidence is presented that inputs from the LP and/or medial or lateral pulvinar nuclei to area 7 neurons may induce not only previously reported enhancement effects but also an assortment of inhibitory effects. Among the latter, both nonspecific and highly specific inhibitions were observed. The high order nature of the network under consideration is reflected by the great variety of types of inhibition observed: non specific general and also specific types of inhibition. Among the specific types preferential inhibition was observed in which the visually evoked but not the spontaneous discharges were affected. In another highly specific type of inhibition, there is cancellation of an added value to the visual response by a cognitive component of the stimulus, a type termed negation. The large variety of interactions observed is interpreted on the basis of massive and varied converging inputs to these cells from the above-mentioned brain regions. An hypothesis is proposed on the basis of these data that the posterior parietal neurons respond to visual stimuli in a way that is uniquely modifiable by a large variety of other added stimuli related to behavioral parameters of the situation and to the various grades of complexity of the visual stimulus. It is assumed that interaction of interneurons of a variety of types is responsible for this large repertoire of processing capacity.