[Topography of the thalamo-cortical projections on trunk representation demonstrated by fluorescent neuro-tracers]

With the aim to study the detailed topography of the thalamo-cortical neurones projecting to the trunk representation zone of the first somatosensory area (SI), punctate injections of three different fluorescent tracers (Evans Blue, Nuclear Yellow and Fast Blue) were performed in the three physiologically defined subareas forming the trunk region of SI. These injections resulted in the labelling of three different cell aggregates, narrow in dorsoventral and mediolateral extent but elongated rostrocaudally, located in topographically distinct regions of the nucleus ventralis posterio-lateralis. The results suggest that the highly organized topography of the trunk representation of area SI is imposed by the thalamo-cortical input from VPL.