The effects of insular and temporal lesions in cats on two types of auditory pattern discrimination

Abstract

Seven cats were tested before and after bilateral lesions of insular-temporal cortex on two types of auditory pattern discrimination. The first discrimination was between two frequency modulated tones, i.e., rising vs. falling frequencies. The second discrimination was between two pairs of pure tones, i.e., low-high vs. high-low frequencies. The animals were trained in a double grill ☐ to avoid a shock when they detected a change in the temporal pattern. Normal cats readily learned to discriminate FM patterns and two-tone patterns. Cats with large bilateral lesions of insular-temporal cortex (4 cases), however, failed to relearn the two-tone pattern discrimination even though in 3 cases discriminations of frequency modulated patterns was relearned. For each of these animals discriminations of sound onset and frequency change were also possible. Thus the effects of large insular-temporal lesions are more severe for pure tone pattern discriminations than for FM patterns. In 3 additional cases with smaller lesions of the insular-temporal area both FM and pure tone patterns were easily relearned and no differences were seen for the two types of pattern discrimination.