Face encoding and psychometric testing in healthy dextrals with right hemisphere language

Objective: To document how right hemisphere language dominance in neurologically normal right-handed individuals affects lateralization of face encoding and level of performance in neuropsychological tests. Methods: Three healthy right-handed adults with predominantly right hemisphere language activation during single-word or sentence-level processing were identified from 210 consecutive right-handed subjects studied using blood oxygenation level-dependent contrast fMRI. These three study subjects (S1 to S3) underwent a second scanning session where they performed word and face encoding. Their functional scans were contrasted with those obtained from six healthy control subjects (C1 to C6) with left hemisphere language dominance. Psychometric tests were performed on the study subjects. Results: Right hemisphere-dominant language activation was reproduced in the second scanning session in the three study subjects. The extent to which the lateralization of face encoding was reversed varied. Right hemisphere language was associated with lower (but within normal) verbal IQ compared with performance IQ in two of three volunteers. Verbal and nonverbal memory scores were normal and did not differ appreciably. Conclusion: Right hemisphere-dominant language in healthy dextrals exists but is rare. The extent to which face encoding is reversed in these individuals is variable. Cognitive function does not appear to be significantly compromised even though some psychometric test scores are asymmetric in favor of nonverbal performance when the reversal of lateralization of face and word memory is not complete.