[Horseradish peroxidase-labeled sources of thalamic projections in the area of the somatosensory cortex representing the vibrissae in the rat].

Localization and morphology of neuronal groups in the ventrobasal thalamic complex that project to the vibrissae area in the somatosensory rat cortex were studied by means of retrograde axonal transport of horseradish peroxidase (HRP). The HRP-labelled cells were located in the ventroposterolateral nucleus of the ventrobasal complex and were grouped in "barreloids" 100-120 microns wide. Staining of several "barreloids" even when the injection was made in a restricted area of the cortex and the growth of labelled cells number in each "barreloid" with an increase in the injection area suggested the existence of divergence as well as convergence of thalamocortical specific connections. Various forms of relay neurons and different extent of HRP-granule inclusion may reflect their different functional value in thalamocortical relationship.