Different patterns of corticopontine projections from separate cortical fields within the inferior parietal lobule and dorsal prelunate gyrus of the macaque.

Corticopontine projection patterns were studied after injections of an 3H-leucine and 3H-proline mixture into each of four distinct cortical fields within the inferior parietal lobule and dorsal prelunate gyrus. Different preferential patterns of pontine labeling were observed for each of the four cortical areas studied. Multiple injections across the dorsal aspect of the prelunate gyrus (area DP) yielded scattered patches of label limited to the dorsolateral pontine nuclear region. A single injection within the lateral intraparietal area (area LIP), located in the caudal portion of the lateral bank of the intraparietal sulcus resulted in a series of labeled patches across the dorsal tier of cells stretching across the dorsal portions of the dorsolateral, peduncular and dorsal pontine nuclei. Injection of the cortex on the caudal aspect of the inferior parietal convexity (area 7a) produced multiple patches of label along the lateral margin of the ventral, lateral, and dorsolateral nuclei. Injection of area 7b resulted in label along the lateral aspects of the ventral, lateral and dorsolateral nuclei, as seen with area 7a injections, as well as additional label in the ventromedial portions of the ventral, peduncular and paramedian pontine nuclei. These results provide supporting anatomic evidence for the functional subdivision of the inferior parietal lobule and dorsal aspect of the prelunate gyrus and provide new information about the organization of cortical projections to the primate pontine nuclei.