Effects of task difficulty on regional cerebral blood flow: relationships with anxiety and performance.

Associations have been described between task difficulty and autonomic arousal. This study addresses task difficulty effects on regional cerebral blood flow (rCBF), a measure of cortical activity. Earlier work suggested that in contrast to a positive association between anxiety and autonomic arousal, there is a curvilinear, inverted-U relationship between anxiety and cortical activity. A sample of 26 normal volunteers (14 men, 12 women) was administered the 133-Xenon inhalation technique for measuring rCBF. Measurements were taken under three conditions: Resting baseline, and Easy and Hard verbal analogy tasks. Subjects were grouped into three anxiety levels on the basis of their average score on a self-report measure. The rCBF was higher during task performance than at rest, but did not differ between the two difficulty conditions. There were Task × Hemisphere interactions showing the expected asymmetry of activation, with higher left hemispheric increase for the verbal task. Anxiety had an inverted-U relationship with both performance and rCBF, which were themselves positively related. These results with measures of central nervous system activity differ from those reported for autonomic responses. They indicate that anxiety effects on cortical activity may mediate the relation between anxiety and performance.