Do thalamic regions which project to rostral primate motor cortex receive spinothalamic input?

The purpose of this study was to examine whether spinal pathways terminate in regions of the primate thalamus which project directly to the motor cortex. In order to examine this issue we employed a 'double labeling' procedure which utilized transport of both anterograde and retrograde tracers in the same macaque. One tracer substance was injected into the cervical spinal cord and the other was injected into the rostral zone of primary motor cortex. We observed no overlap of spinothalamic terminations and thalamic regions which project to the motor cortex. Thus, our results provide no anatomical support for a direct thalamic relay of peripheral afferent input to the motor cortex of primates.