[Horseradish peroxidase labelled neurons of nonspecific thalamic nuclei projecting to the cat brain somatosensory zone I].

The morphology and topography of neurons whose axons form the thalamic nonspecific input to the primary somatosensory cortex were studied in the cat thalamus by the method of the retrograde transport of the horseradish peroxidase. The labelled cells were found in the dorsolateral part of the nucleus ventralis anterior, in the nucleus centralis lateralis, in the lateral part of the nucleus dorsalis medialis, in the dorsal part of the nucleus centrum medianum. A very small number of slightly stained cells were found in the nucleus paracentralis. The variety of the shape, size and intensity of labelling of the HRP-positive cells was observed in each thalamic structure. The results of the experiments indicate that not only the ventrobasal complex but also the nonspecific thalamic nuclei are projected to the primary somatosensory cortex. These data demonstrate the existence of multiple afferent thalamic inputs to the primary somatosensory cortex.