Cutaneous receptive field organization in the ventral posterior nucleus ofthe thalamus in the common marmoset

Cutaneous receptive field organization in the ventral posterior nucleus of the thalamus in the common marmoset J. Neurophysiol. 82: 1865-1875, 1999. T he organization of cutaneous receptive fields in the ventroposterior (VP) t halamus of the common marmosets (Callithrix- jacchus) was determined from s ingle-unit recordings, and these data were correlated with the cytochrome o xidase (CO) histochemistry of the thalamus in the same animals. Under conti nuously maintained ketamine anesthesia, the receptive fields of a total of 192 single units were recorded from the right VP thalamus using 2 M Omega g lass microelectrodes. After the receptive fields were mapped, the brains we re reacted for CO histochemistry on 50-mu m coronal frozen sections through the entire VP thalamus. The majority of units were localized to the GO-rea ctive regions that define the medial and lateral divisions of VP (VPm and V PI). Apart from the expected finding of the face being represented in VPm a nd the body in VPI, reconstructing the electrode tracks and unit locations in the histological sections revealed a general association between discret e regions of CO reactivity and the representation of specific body regions. Some low-threshold cutaneous units were apparently localized to VPi (the C O weak regions dorsal, ventral, and interdigitating with, the CO regions of VP). These VPi units were clearly part of the same representational map as the VPI and VPm units. We conclude that the low-threshold cutaneous recept ive fields of the marmoset are organized in a single continuous representat ion of the contralateral body surface, and that this representation can mos t simply be interpreted as being folded or crumpled into the three-dimensio nal space of VP thalamus. The folded nature of the body map in VP may be re lated to the folded nature of VP as revealed by CO histochemistry.