Tolerances of responses to visual patterns in neurons of the posterior inferotemporal cortex in the macaque against changing stimulus size and orientation, and deleting patterns.

Neuronal activities were recorded in areas TEO and TE of the inferotemporal cortex in four hemispheres of two monkeys during the performance of a visual pattern discrimination task. Tolerances of responses to patterns against changing stimulus size and orientation, and deleting patterns halves were investigated and compared between TEO and TE neurons. Of 311 neurons tested, 80 (26%) responded to one or more patterns out of four standard patterns. Of these 80 neurons, 50 (63%) were recorded in area TEO and 30 (38%) in area TE. Neurons responsive to patterns were recorded in both areas TEO and TE, however degrees of tolerance of responses were different between TEO and TE neurons. Tolerances of TEO neurons were moderate and degrees of tolerance varied from neuron to neuron. Responses to particular patterns were dependent on stimulus size, stimulus orientation, and/or completeness of patterns. By contrast, tolerances of TE neurons were generally strong. Responses to particular patterns were not affected by changing stimulus size, changing stimulus orientation nor deleting patterns halves. These results suggest that area TEO rather than area TE is involved in detecting and processing particular visual shapes.