[Organization of the projections of the cortex of the sulcus cruciatus to the centromedian and parafascicular nuclei in cats].

In order to study the HRP retrograde axonal transport, injections of horseradish peroxidase (HRP) were made in the centromedian and parafascicular nuclei of the cat. The centromedian nucleus receives more cortical projections than the parafascicular nucleus. After centromedian and parafascicular nuclei injections, retrograde labeling was more abundant in the ventral bank of the cruciate sulcus than in its dorsal bank. Area 4 projects preferentially to the centromedian nucleus. These projections arise mainly in sector gamma of area 4. Projections from area 6 a beta to the centromedian and parafascicular nuclei are slightly more numerous than those arising in 6 a alpha. Projections from the sectors of motor and premotor areas located in the depth of the cruciate sulcus are scanty. These projections, however, are mainly directed to the centromedian nucleus and the lateral portions of the parafascicular nucleus. Cortical neurons projecting to centromedian and parafascicular nuclei are mainly situated in the superficial and intermediate sublayers of layer V. Only scarce projections arise from neurons located in layer VI.