Increase of regional cerebral blood flow during mental effort in normals and in patients with focal brain disorders

Summary

Regional cerebral blood flow (rCBF) was recorded simultaneously in four circumscribed hemisphere regions in 30 subjects in double determinations by means of the intra-arterial ¹³³Xenon clearance technique. Group I was a control group of 10 subjects. Group II consisted of 12 subjects of which 4 were normals and 8 were patients without signs of organic local or diffuse cerebral disorders. Group III consisted of 8 patients with localized hemisphere lesions. During one of the rCBF measurements, the subjects in Groups II and III were asked to perform a digit-span-backward test.

In Group II the test gave rise to a small but significant increase in rCBF which averaged about 2.2 ml/100 g/min in mean rCBF, i. e. an increase of about 5 %, and 5.7 ml/100 g/min for gray matter flow, i.e. an increase of 8%. This increase was most evident in “suprasylvian” parts of the hemisphere. An increase in rCBF was also found in Group III with focal cerebral lesions. In four cases with circumscribed lesions which all involved superficial parts of the hemisphere, only small or no changes were seen during mentation within the lesions, and some marked augmentations outside the pathologic areas.

The augmentation of rCBF during the test probably reflects more or less regional functional (metabolic) accompaniments to mentation. It is likely that both general changes of the ‘arousal’ type, as well as localized gray matter changes take part in these events.