An Experimental-Anatomical Study on the Cortical Projection of the Posterior Ventral Nuclei in the Cat

The present investigation is an attempt to study the cortical projection of the posterior ventral nuclei of the cat by the Nauta-Gygax method. 1. Preterminal degeneration is found in both primary and secondary sensory areas (SI and SII) in all cases with lesions in the posterior ventral nuclei. 2. The posterior ventral nuclei are composed of the posteromedial and posterolateral ventral nuclei. The former projects to the coronal gyrus (face area of SI) and the anteriormost part of the anterior ectosylvian gyrus (face area of SII) in a somatotopically organized manner. 3. The ventromedial part of the posterolateral ventral nucleus sends fibers to the lateral sigmoid gyrus (arm area of SI) and the anteroinferior part of the anterior ectosylvian gyrus (arm area of SII). 4. The dorsolateral part of the posterolateral ventral nucleus projects to the posterior sigmoid gyrus (leg area of SI) and the posterosuperior part of the anterior ectosylvian gyros (leg area of SII). 5. The cortical projecting areas in both SI and SII of the posteromedial ventral nucleus are continuous, while those in both SI and SII of the posterolateral ventral nucleus, particularly its dorsolateral part, are separated. 6. The paralaminar part of the lateral ventral nucleus projects mainly to the motor area in the anterior sigmoid gyrus. 7. The cortical projecting areas in SI of various parts of the posterior ventral nuclei tend to overlap each other. The cortical projecting areas of the posteromedial ventral nucleus extensively overlap with the motor area in the anterior sigmoid gyrus, while those of the posterolateral ventral nucleus, particularly of its dorsolateral part, do not spread into the motor area. 8. The cortical projecting areas in SII of different parts of the posterior ventral nuclei overlap each other, although they are essentially organized in a somatotopical manner.