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Background: Some studies have reported psychotic symptom exacerbation during "pharmacologic challenge" paradigms using dopamine agonists. Few studies, however, have examined the effects of these agonists on neurocognitive functions in patients with schizophrenia. This study assessed the effects of methylphenidate infusion on an oral word production test with demonstrated sensitivity to frontal lobe lesions, and on clinical state., Methods: Patients were tested at two different phases; at the onset of their first-episode of schizophrenia (acute phase), and then again after they had responded to treatment and were clinically stable (stabilization phase). During each phase, patients were tested prior to and following methylphenidate infusion. Symptom clusters (i.e., positive, negative, and disorganization) were formed from SANS and SADS-C (+PD) ratings at each of these four timepoints., Results: Patients produced significantly more words at preinfusion and while stabilized, suggesting that overall, decreased dopamine activity was associated with better word production. Redundant errors (i.e., perseverations of previously mentioned words and production of multiple words with the same roots) increased significantly following infusion in the stabilized phase. Disorganization symptoms increased significantly following infusion, regardless of study phase., Conclusions: These findings are consistent with previous theoretical and empirical findings relating dopamine activity to verbal output, a "redundancy bias" in cognitive control, and exacerbation of disorganization symptoms.

The evidence for frontal lobe structural abnormalities in schizophrenia using magnetic resonance (MR) imaging has been mixed, but most studies used either single slice measures or total volumes of a single frontal region, neither of which is sensitive to potential volume differences in more specific subregions. This study employed reliable methods for parcellation of the frontal lobes from MR images based on the sulcal anatomy. Following a cytoarchitectonic theory that distinguishes dorsomedial (archicortically derived) from ventrolateral (paleocortically derived) frontal subregions, we measured the superior frontal gyrus, anterior cingulate gyrus, and orbital frontal region in 19 first-episode schizophrenia patients and 26 healthy comparison subjects. Results indicated that male patients had significantly larger right orbital frontal volume compared to their left orbital frontal volume and compared to healthy men. Among male patients larger right orbital frontal volume was significantly correlated with smaller right 'archicortical' (i.e. anterior cingulate and superior frontal gyri) volume. Furthermore, the ratio of right orbital frontal to right 'archicortical' volume was significantly and positively correlated with level of delusions among male patients. These findings suggest that there may be reciprocal controls on 'archicortical' and 'paleocortical' neurodevelopment among men with schizophrenia, and that larger paleocortical relative to archicortical volumes may be associated with increased delusions.

Handedness questionnaire items from the General Scale of the Lateral Preference Schedule (Dean, 1988) were administered to 423 intellectually gifted and 226 nongifted children to investigate the underlying processes that contribute to laterality. Handedness items were factor analyzed using principal components (PC) analysis with varimax rotation. PC analyses computed separately for gifted and nongifted left and right-handed writers yielded very different factor structures. Left-handers (regardless of gifted status) tended to have factor structures marked by items that loaded saliently on more than one factor. Whereas a four factor solution best fit the data for the nongifted left-handers, a three factor solution was the best fit for the gifted left-handed children. The factor structure for the left-handed gifted children was marked by two factors where the item "draw" was the only item to load both positively and saliently, a pattern not evident among the nongifted left-handers. These results suggested different underlying patterns contributing to laterality among these groups of children.

This study investigated high school students' marijuana usage patterns in relation to their harmfulness ratings of 15 licit and illicit drugs, perceived negative consequences from using marijuana, and types of defense mechanisms employed. Subjects were classified into one of five pattern-of-use groups based on marijuana usage: principled nonusers, nonusers, light users, moderate users, and heavy users. Principled nonusers (individuals who have never used marijuana and would not do so if it was legalized) rated marijuana, hashish, cocaine, and alcohol as significantly more harmful than heavy users. A cluster analysis of the drugs' harmfulness ratings best fit a three cluster solution and were named medicinal drugs, recreational drugs, and hard drugs. In general, principled nonusers rated negative consequences from using marijuana as significantly more likely to occur than other groups. Principled nonusers and heavy users utilized reversal from the Defense Mechanism Inventory, which includes repression and denial, significantly more than nonusers, indicating some trait common to the two extreme pattern-of-use groups.