DENDRITIC ORIENTATION OF THALAMOCORTICAL PROJECTION NEURONS IN THE VENTROBASAL COMPLEX OF MACAQUES

This study describes the orientation of dendritic arbors from intracel lularly labeled thalamocortical projection (TCP) neurons of Macaca fas cicularis or Macaca mulatta. All neurons were located in the ventrobas al complex and responded to non-noxious stimuli. Each neuron was compo sed of dendrites that Varied considerably in size and each dendrite te nded to occupy a particular region of the perisomatic space with minim al overlap with other dendrites. Quantitative and qualitative analysis of the dendritic arbors of the labeled neurons showed they had an asy mmetric distribution so that some regions of the perisomatic space con tained more of the dendritic tree than others. Eleven of the thirteen reconstructed neurons had a larger percentage of the dendritic tree pr ojecting into the medial portion of the perisomatic space. These resul ts show that the dendritic arbors of macaque TCP neurons are not organ ized in a radially symmetric pattern as previously described and the a symmetric distribution of dendrites may be related to synaptic input.