VISUAL-DISCRIMINATION IMPAIRMENTS FOLLOWING LESIONS OF THE SUPERIOR TEMPORAL SULCUS ARE NOT SPECIFIC FOR FACIAL STIMULI

Six rhesus monkeys took part in an experiment on visual learning. In t hree of the monkeys the part of the superior temporal sulcus in which many of the cells respond selectively to some aspect of faces was remo ved, while the remaining three animals served as unoperated controls. In Experiment 1 they learned a series of two-choice visual discriminat ions between patterns. The animals with lesions of the superior tempor al sulcus were markedly impaired. The discriminations were of two type s: in the first, the discriminanda differed in shape (e.g. Y and 3), w hile in the second they differed only in their orientation (e.g. [and] ). Unlike animals with lesions to the neighbouring inferior temporal c ortex who are impaired on shape but not orientation discriminations, a nimals with lesions of the superior temporal sulcus were equally impai red on both types of discrimination. In Experiment 2 the same six anim als learned a series of discriminations between discriminanda which co nsisted of photographs of pairs of eyes. Each discrimination was betwe en a set of eyes which looked directly at the viewer and a set in whic h the gaze was laterally averted to varying degrees. Again, animals wi th lesions of the superior temporal sulcus showed a marked impairment. We conclude that this impairment may be a general impairment in two-c hoice visual discrimination learning, rather than a selective impairme nt in discrimination of eye gaze. This result warns against a simple i nterpretation or the function of this area as a ''face area'', concern ed only, or chiefly, with the perception and significance of parts of the body, notably faces, and their movements.