| The role of hemispheric specialization is well defined for posterior cortices. However, it has not been sufficiently studied in the frontal lobes. The lateralization of frontal lobe functioning is traditionally characterized only by the language/non-language dichotomy. The language/non-language distinction, however, can be viewed as a specific example of a more fundamental process. Based on the theory developed by Goldberg and Costa (1981) it is hypothesized that the left prefrontal cortex (PFC) is critical for cognitive stability (maintaining an internalized plan or strategy), while the right PFC is important for the maintenance of cognitive plasticity (switching between cognitive strategies and processing novel information).;A group of 20 subjects with well lateralized left and right PFC lesions (5 of each sex having left and right lesions) were administered two novel tasks (SP1 and SP2) and a set of standard neuropsychological tests (WAIS-R and Raven's Standard Progressive Matrices (RSPM)). A group of 34 healthy controls (17 males and females) were also administered SP1 and SP2 and a personality questionnaire measuring traits similar to cognitive stability and plasticity.;The psychometric properties of SP1 and SP2 in the healthy controls revealed high test/retest reliability and substantial convergent validity with the Extroversion scale from the Eysenck Personality Questionnaire.;A significant gender difference in both healthy controls and lesion subjects was found. Healthy control females responded in a plastic fashion (target independent), while healthy control males responded in a more stable (target dependent) manner.;There was a diametric effect in males with lateralized PFC lesions: a left PFC lesion produced a bias toward plasticity, while a right PFC lesion produced a bias toward stability, relative to matched healthy controls. Unexpectedly, females with left or right PFC lesions had a bias toward cognitive stability, relative to matched healthy controls. Possible explanations for the occurrence of the results and their implications in understanding hemispheric specialization in the PFC, and gender differences, were presented. |
