EFFECT OF DESTROYING THREE LOCALIZED CEREBRAL CORTICAL AREAS FOR SOUND ON CORRECT CONDITIONED DIFFERENTIAL RESPONSES OF THE DOG'S FORELEG

Abstract

This study is concerned with the effect of extirpation of 3 separate cortical areas or combinations of the same upon what has been termed correct conditioned differential foreleg flexion. These cortical areas, all of which yield electrical responses from stimulation of the cochlea, are indicated by A, B and C and include all of the sylvian and ectosylvian gyri together with strips of the coronal and suprasylvian gyri. Two different sets of antagonistic analysers were used. In one set, based on tones, the positive and negative conditioned stimuli consisted respectively of tapping a bell or an iron cup once/sec. In the other set, based on timing, a bell tapped once/sec, or 3 times/sec. served for the positive and negative conditioned stimuli. To be correct, the positive response had to appear within 7 secs. (usually 1-3) and the negative had to be withheld for 15 secs. Bilateral deletion of areas A, B, C alone or of B and C together caused but little or no delay in appearance of previously acquired correct conditioned differential responses of the foreleg with 2 different sets of sound stimuli. Bilateral elimination of cortical areas A and B disrupted the usual association circuits for evoking correct conditioned differential responses for the 2 different sets of sound analysers. Re-establishment of these responses required 370-484 tests. The new mechanism was fully as accurate as the original, but was inferior in other respects. Unilateral elimination of cortical areas A, B and C permitted immediate return of correct conditioned differential responses with both sets of sound analysers. Bilateral destruction of areas A, B and C caused no noteworthy delay in the appearance of the positive conditioned reflex, but prevented reappearance of correct conditioned differential responses in over 1100 tests for each of 3 dogs with each set of analysers. Additional tests 6 mos. later revealed no return of function. The presence of area 3 on the left side of one dog in which this operation was attempted, permitted correct responses for the slow and fast bell stimuli, but abolished all correct responses for the bell and cup. Superficial coagulation of areas A, B and C in one dog resulted only in a delayed return of the correct responses. The first and chief effect noted from the larger lesions was one involving correct inhibition, inability to hold back foreleg flexion during a negative conditioned test. While the usual time interval between tests was about 2 min., all of the dogs which were able to make correct conditioned differential responses after the lesions were also able to respond correctly to a series of alternate positive and negative conditioned tests when the interval between tests was of 3 seconds'' duration.