Hemispheric control of hand function in the human brain

The cerebral dominance argument holds that the hand is representative of the functions of the hemisphere by which it is controlled. An influx of visual information to that hemisphere should result in a disruption of simultaneous performance by the hand. This view was tested by requiring the subject to perform a sorting task with one hand whilst at the same time performing a visual task on which information was projected either to the hemisphere relating to hand performance or to its opposite member. Visual information projected to the same hemisphere does not interfere with the performance of the hand. This suggests that control of hand function can be switched from one hemisphere to the other as the need arises.