For many years, most researchers believed the left cerebral hemisphere to be specialized for language and the right for perception and mental imagery. In the early 1980's, it became clear, however, that the left hemisphere is actually better than the right at some imagery tasks, but it is worse than the right at other imagery tasks and roughly as good as the right at still other imagery tasks. It is now clear that complex tasks such as imagery are not performed by a single part of the brain, but rather arise from the joint action of many components working in concert. Some of these actions apparently are carried out by the left hemisphere, and some are carried out by the right. This research will characterize the nature of these component processes and will determine how they are lateralized to the left or right hemisphere. For example, experiments will examine the processes that allow one to activate a pattern into a visual image, to rotate patterns in images, and to "inspect" patterns in images. Patients who have suffered damage to the left or right cerebral hemisphere will be tested on a set of imagery tasks, and their deficits compared. The theory underlying the research holds that some tasks will be impaired more following damage to the left hemisphere than the right and others will be impaired more following damage to the right hemisphere. Examination of which tasks are always lateralized in the same way as certain other tasks will provide evidence for the existence of distinct processes. Furthermore, these patterns of lateralization will allow for the test of computer models of how experience affects cerebral lateralization. The increased understanding of imagery gained from this research is relevant to training in various branches of science and engineering, because of the critical role of imagery in the spatial thinking so necessary in those areas. If we understand the component processes of imagery and which processes are used in which kinds of tasks, we may be able to train people to use imagery more effectively in their thinking. Such training might allow students who would otherwise drop out of visually oriented technical disciplines to succeed in such work.
