Focal increase of cerebral blood flow during stereognostic testing in man.

An attempt was made to study the regional cerebral blood flow (rCBF) pattern during stereognostic discrimination in man. The rCBF was measured in 18 subjects who had no major neurological defects. The clearance from the hemisphere of xenon 133 injected (133Xe) into the carotid artery was measured with a 254-channel dynamic gamma camera. During stereognostic discrimination with hand, mouth, or foot, the rCBF increased focally in the corresponding contralateral sensory-motor region and increased focally in the premotor part of the frontal lobe. The increase in the sensory region was attributed to the work of neurons extracting spatial features from the received input, while the increase in the motor region was ascribed to the formulation of motor strategies and motor commands. The physiological significance of the increase in the frontal region was unclear, tentatively, it was suggested to reflect the intention, selective attention, and decision of the subject.