Anatomical evidence for cortical projections from the striatum in the cat.

Several anatomical and physiological studies have thus far failed to confirm the existence of striatocortical projections proposed in 1895 by Cajal. Evidence for such striatocortical projections was obtained in the present study using the horseradish peroxidase (HRP) tracing method. When 0.1-0.8 microliter of 30-50% HRP in saline was injected into different cortical regions in cats, HRP was transported to cells in different thalamic nuclei, striatum and the globus pallidus. Only large striatal cells, 30--60 micrometers in their long axes, contained HRP reaction product. After injection in area AI, the striatocortical cells were located in the dorsal parts of the middle third of putamen, where auditory cortical afferents are known to project, thereby suggesting reciprocal connections between the cerebral cortex and the striatum.