Present address: Department of Physiology, Medical College, Xian Jiao Tong University, Xian Shaanxi 710061, China.
Divergence and convergence of thalamocortical projections to premotor and supplementary motor cortex: a multiple tracing study in the macaque monkey
Article first published online: 7 MAR 2005
European Journal of Neuroscience
Volume 21, Issue 4, pages 1007–1029, February 2005
How to Cite
Morel, A., Liu, J., Wannier, T., Jeanmonod, D. and Rouiller, E. M. (2005), Divergence and convergence of thalamocortical projections to premotor and supplementary motor cortex: a multiple tracing study in the macaque monkey. European Journal of Neuroscience, 21: 1007–1029. doi: 10.1111/j.1460-9568.2005.03921.x
- Issue published online: 7 MAR 2005
- Article first published online: 7 MAR 2005
- Received 22 June 2004, revised 4 November 2004, accepted 2 December 2004
- motor thalamus;
- non-human primate;
- retrograde tracing;
The premotor cortex of macaque monkeys is currently subdivided into at least six different subareas on the basis of structural, hodological and physiological criteria. To determine the degree of divergence/convergence of thalamocortical projections to mesial [supplementary motor area (SMA)-proper and pre-SMA] and lateral (PMd-c, PMd-r, PMv-c and PMv-r) premotor (PM) subareas, quantitative analyses were performed on the distribution of retrograde labelling after multiple tracer injections in the same animal. The results demonstrate that all PM and SMA subareas receive common inputs from several thalamic nuclei, but the relative contribution of these nuclei to thalamocortical projections differs. The largest difference occurs between subareas of SMA, with much greater contribution from the mediodorsal (MD) and area X, and a smaller contribution from the ventral lateral anterior (VLa) and ventral part of the ventral lateral posterior (VLpv) to pre-SMA than to SMA-proper. In PM, differences between subareas are less pronounced; in particular, all receive a significant contribution from MD, the ventral anterior (VApc) and area X. However, there are clear gradients, such as increasing projections from MD to rostral, from VLa and VLpv to caudal, and from dorsal VLp (VLpd) to dorsal premotor subareas. Intralaminar nuclei provide widespread projections to all premotor subareas. The degree of overlap between thalamocortical projections varies among different PM and SMA subareas and different sectors of the thalamus. These variations, which correspond to different origin and topography of thalamocortical projections, are discussed in relation to functional organizations at thalamic and cortical levels.