Tested 36 male sprague-dawley blinded rats in a t maze on 5 2-choice tactile discriminations. 2 groups had bilateral lesions of the 2 somatosensory cortical areas made either simultaneously or with a 35-day interval between sides. Other groups had 1- or 2-stage sham operations. Ss with 1-stage lesions performed more poorly than ss with 2-stage lesions. Ss with simultaneous lesions also performed worse than ss with 1-stage sham operations, although ss with sequential lesions did not differ from 2-stage sham operates. In a 2nd experiment with 28 ss, 1 group had small bilateral somatosensory cortex lesions that were enlarged to full size after 35 days. These ss performed better than ss with tissue removed in 1 operation, although they performed more poorly than controls when discrimination scores were pooled. (20 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)