Development of tactile discrimination capacity in Macaca mulatta. III. Effects of total removal of primary somatic sensory cortex (SmI) in infants and juveniles

Abstract

Four infant macaques between the ages of 3.0 and 5.1 weeks and three juvenile macaques between the ages of 79.9 and 109.3 weeks received unilateral lesions of all cytoarchitectural fields (Brodmann's areas 3, 1 and 2) in the hand area of the postcentral gyrus. These total SmI-lesioned infants acquired the size and texture tasks within the same time period and with the same efficiency as normal infants. On some size- and texture-ALL tasks they actually performed significantly better than partial SmI-lesioned or normal infants. The normal acquisition and ALL performance of the infants with total SmI lesions contrasts with that of the juveniles with comparable lesions. On size acquisition and ALL tasks, with the contralateral hand, total SmI-lesioned juveniles were significantly inferior to normal and total SmI-lesioned infants and to partial SmI-lesioned juveniles. During texture acquisition with the contralateral hand, the total SmI-lesioned juveniles made significantly more errors than normal and total SmI-lesioned infants. The capacity to recover from partial SmI lesions extends into the second year of life and is a gradual process which may be mediated by remaining SmI subdivisions. By contrast, the capacity to recover from total SmI lesions is restricted to infants and is a rapid process which must depend on other areas within the damaged, or possibly the intact, hemisphere.