Visual neglect during intracarotid amobarbital testing.

The unilateral suppression of hemispheric function by sodium amobarbital may result in hemispatial visual neglect, as measured by performance on a random letter cancellation task. Our study not only investigates this hypothesis but also attempts to identify more precisely the anatomic locus of control for directed attention to extrapersonal space by correlating scanning performance with EEG activity. Forty-eight consecutive patients with epilepsy underwent preoperative intracarotid amobarbital tests. The results indicated that disruption of scanning and contralateral neglect occurred only after right-hemisphere suppression and seemed specifically related to changes in right frontal lobe EEG activity. This pattern of performance held not only for right-handed subjects, but also for those who were left-handed, and even for those who had right-hemisphere language dominance.