Role of the parietal associative area of the cortex for "counting" behavior in dogs.

Experiments were performed on six dogs to study the effects of simultaneous and separate ablation of fields 5 and 7 of the parietal cortex on "counting" behavior. Dogs were trained to discriminate series of five sound clicks presented with variable interstimulus intervals from similar series consisting of three clicks. A food-related operant response (elevation of the right forepaw to place it on the feeder) was used to develop asymmetrical differentiation; the positive signal was a series of five clicks with variable interstimulus intervals and the negative (unreinforced) stimulus was a series of three clicks. Simultaneous bilateral ablation of fields 5 and 7 of the parietal cortex, like bilateral ablation only of field 5, produced profound impairment of differentiation lasting 2-3 months. Isolated bilateral ablation of field 7 produced no impairment of differentiation. These data led to the conclusion that field 5 of the parietal cortex is important for discriminating the numbers of sequential signals.