Читать книгу The Behavior of Animals - Группа авторов - Страница 58

Animals, including humans, may guide their perception toward interesting parts of a scene and suppress uninteresting ones. In a behavioral experiment monkeys were trained to draw their attention either to a red or a green stripe (Barinaga 1997). In the neurophysiological experiment both stripes were presented in the excitatory visual receptive field of a red-sensitive neuron of area V4. The neuron responded to the red stimulus. If both stimuli were presented and the monkey was prompted to focus on the red one, the neuron fired as expected. However, requested to focus on the green stripe, the red-sensitive neuron was silent albeit the red stripe, too, was present in its excitatory receptive field.

Studies applying functional neuroimaging technologies in humans offer a look at the activity pattern in cortical visual areas. The regional neural activity depends on which property of an object the test-person shows interest. If a person is asked to focus on an object’s motion, an area corresponding to V5 is mainly activated. Paying attention to the color, an area corresponding to V4 is principally responsive. When shape is the focus, greatest activation is elsewhere along the “what” processing stream. In another task, photos of faces in frames were shown. Asking whether the faces looked different, ITC was strongly activated. Requesting whether a face was positioned symmetrically in the frame, activation shifted to the PPC.