chimeric stimulation
a procedure used by Roger Sperry and colleagues to study the functions of the two isolated cerebral hemispheres in split-brain patients. In a typical experiment, participants are presented with an image of a chimeric face, showing the left half of one face joined to the right half of a different face. Both halves are shown in gray scale and are adjusted to fit in an apparently natural way. In patients with a surgically severed corpus callosum, the left hemisphere perceives the left half of visual space, and the right hemisphere perceives the right half. If the patient’s eyes are fixating on the midline of the chimeric face, each hemisphere fills in the missing half by symmetry, yielding two separate percepts of two different faces. Sperry suggested that in split-brain patients there may be two conscious streams in the two hemispheres. See also commissurotomy; left-hemisphere consciousness; right-hemisphere
consciousness.