COMPARISON OF THE PATTERNS OF CALLOSAL CONNECTIONS IN LATERAL PARIETAL CORTEX OF THE RAT, MOUSE AND HAMSTER

In a recent study of the second somatosensory area (SmII) in the rat i t was reported that the somatotopic map in the cortex lateral to the p rimary somatosensory area (SmI) is closely related to local features o f the callosal pattern. The existence of this relationship suggests th at knowledge of the overall pattern of callosal connections in the cor tex lateral to SmI may facilitate the description of the somatotopic o rganization of lateral parietal cortex in other rodents. We tested thi s suggestion by comparing the callosal patterns in lateral parietal co rtex in the rat, mouse and hamster. Our finding that the callosal patt ern in the mouse closely resembles that in the rat supports the idea t hat the callosal pattern reflects the underlying somatotopy because th e maps of Smn: described previously in the mouse and rat are Very simi lar to each other. In addition, on the basis of our observation that t he callosal pattern in the hamster is very similar to that in the rat and mouse, we predict that these three rodent species share a common s omatotopic plan in lateral parietal cortex.