EFFECT OF PREFRONTAL BRAIN LESIONS ON CORRECT CONDITIONED DIFFERENTIAL RESPONSES IN DOGS

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Abstract
It was reported previously that prefrontal lobectomy with the exception of the afferent olfactory system abolished correct conditioned differential responses from olfactory stimulation but not from auditory or tactile stimulation. The purpose of this study is to localize the area concerned. The results show that lesion A, which involved a 5 mm. square of cortex rostral to the cruciate sulcus and lesion B, a bilateral extirpation extending from the cruciate sulci to the olfactory lobes, produced no noteworthy effect on correct conditioned differential responses from olfactory or auditory stimulation. On the other hand, lesion C, which removed, bilaterally, 3-or 4-mm. strips of cortex extending cephalad and ventrad along the inner margin of the presylvian sulci to the porous sulci, or similar lesions D, which extended lesser distances dorso-caudad but greater distances ventrad, abolished correct conditioned responses of the foreleg from olfactory stimulation for over 5000 tests, which extended over intervals of 6 mos.'' duration. Like responses from auditory stimulation were not affected by these lesions. The defect following lesions C and D was inability to withhold the foreleg response for a negative conditioned stimulus or lack of correct inhibition. Since lesions C or D destroyed nearly all of Tower''s prefrontal inhibitory field or all of suppressor band 8s of o''ther authors without injury to the lateral olfactory tract, it is likely that they destroyed the important efferent center for evoking the olfactory negative conditioned reflex. Consideration was given in the discussion to the possible origin outlet and function of this and other cerebral suppressor areas.
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