During the course of my project "Sensorimotor cortex in prosimian primates" I have begun to look in anthropoids for patterns of cortical organization and thalamocortical connections homologous to those in prosimians. In my previous studies of Macaca and Galago I found that unilateral lesions of either primary (SI) or secondary (SII) somatic sensory cortex did not result in the severe and irreversible tactile discrimination deficits found after the same cortical removals in adult members of each species. Our studies of thalamocortical connections in Galago have indicated that the ventroposterior thalamus (VP, the major thalamic replay nucleus to SI and SII) extended collaterals to both SI and SII before 5 weeks of age (the age at which early lesions were made in behavioral studies). In adult animals, a single VP neuron projected either to SI or SII but not with collaterals to both areas. The current studies in Macaca were designed to examine the tactile discrimination capacity of animals receiving SI lesions prenatally in the third trimester or at 5 weeks postnatally when tested on a new tactile discrimination apparatus which allows for more precise measurement of tactile discrimination thresholds than earlier methods. Comparisons will be made of the hand contralateral to the normal vs the SI-lesioned hemisphere as well as to thresholds of normal animals. A third animal also is being trained on these same tasks to compare tactile capacities before and after a unilateral SI lesion made in a mature macaque. These tow infants and on adult, age being trained on tactile discrimination tests and it is anticipated that the full battery of tests will be completed in 6 months. When these animals have completed the behavioral testing they will be moved to Vanderbilt U, where electrophysiological recordings will be done in the remaining somatic sensory area (SII) in the lesioned hemisphere. Retrograde fluorescent tracers will be injected in the remaining area (and in the homotypical SII area of contralateral hemisphere) to compare the pattern of VP thalamic projections in the normal and damaged hemisphere as a function of age. It is expected that those animals with prenatal SI damage will show patterns of VP projections to SII that resemble those of prosimians, with direct VP projections to SII in contrast to normal connection in which VP projects to SI. These studies are expected to demonstrate whether the direct VP-SII connections that exist in adult Galago exist in fetal Macaca but are lost during postnatal maturation and if such aberrant VP-SII projections remain in the animal with fetal SI lesion