Читать книгу The Behavior of Animals - Группа авторов - Страница 57

“Where is the object?” deals with “how should it be responded to?” This requires spatial vision in connection with analyses of object motion and depth: starting in the large-celled retina, continuing in related structures of LGN and processing—via corresponding areas V1-3, V5—in the posterior parietal cortex, PPC (Figure 2.11).

The PPC contains neurons responsible for target-oriented reaching or grasping involving arm, hand, and fingers. Such neurons fulfill integrative tasks. Motivation plays an essential role. If a satiated monkey was offered a banana, its visual fixation neurons failed to respond or discharged sluggishly and the animal ignored the banana (Mountcastle et al. 1975), in reminiscence of a comparable situation observed in toads.

The “what” and “where/how” processing streams are not completely segregated. A patient with damage to the “what” stream was able to reach for an object; however, if the object’s shape required an appropriate grasping pattern, the patient failed to grasp it.