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Objective: To assess the efficacy of quetiapine, a recently introduced second generation antipsychotic medication, in reducing cognitive impairment in patients with schizophrenia., Design: Prospective, randomized, double-blind clinical trial., Patients: 25 patients who met the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, (DSM-IV) criteria for schizophrenia were recruited from 3 Canadian hospitals., Intervention and Outcome Measures: After a 48-hour washout period, 25 patients with schizophrenia were randomly assigned to double-blind treatment with quetiapine or haloperidol for 6 months and evaluated with rating scales for psychotic symptoms, mood and extrapyramidal side effects, as well as standardized neuropsychological measures sensitive to 6 cognitive domains: fine motor skill, attention span, verbal reasoning and fluency, visuospatial construction and fluency, executive skills and visuomotor tracking, and immediate recall of verbal and nonverbal materials. The measures were repeated 8 weeks and 6 months after treatment was initiated., Results: Quetiapine improved psychosis and mood without inducing extrapyramidal symptoms. Quetiapine also had beneficial effects on cognitive skills, particularly verbal reasoning and fluency skills and immediate recall, with additional improvements on executive skills and visuomotor tracking and on the average of the 6 cognitive domains with sustained treatment. Patients taking haloperidol showed improvements in general clinical status, but no specific improvements on the positive syndrome, the negative syndrome, depression ratings or cognitive skills., Conclusions: These preliminary results support the potential value of quetiapine for improving cognitive impairment in patients with schizophrenia and emphasize the importance of further research with this promising atypical antipsychotic.

Objective: To test the discriminant validity of a model predicting a dissociation between measures of right and left frontal lobe function in people with schizophrenia., Participants: Twenty-one clinically stable outpatients with schizophrenia., Interventions: Patients were administered the University of Pennsylvania Smell Identification Test (UPSIT), the Stroop Color-Word Test (Stroop), and the Positive and Negative Syndrome Scale (PANSS)., Outcome Measures: Scores on these tests and relation among scores., Results: There was a convergence of UPSII and Stroop interference scores consistent with a common cerebral basis for limitations in olfactory identification and inhibition of distraction. There was also a divergence of UPSIT and Stroop reading scores suggesting that the olfactory identification limitation is distinct from a general limitation of attention or a dysfunction of the left dorsolateral prefrontal cortex. Most notable was the 81% classification convergence between the UPSIT and Stroop incongruous colour naming scores compared with the near-random 57% classification convergence of the UPSIT and Stroop reading scores., Conclusions: These data are consistent with a right orbitofrontal dysfunction in a subgroup of patients with schizophrenia, although the involvement of mesial temporal structures in both tasks must be ruled out with further study. A multifactorial model depicting contributions from diverse cerebral structures is required to describe the pathophysiology of schizophrenia. Valid behavioural methods for classifying suspected subgroups of patients with particular cerebral dysfunction would be of value in the construction of this model.

This review of the clinical features of Huntington's disease incorporates recent developments in pathophysiology, preclinical diagnosis and treatment. Although the mechanism initiating and guiding the cell destruction in this illness is currently unknown, the excitatory neurotoxin and the energy metabolism models may provide a valuable direction for future research. Similarly, although the precise relation between the neuroanatomical damage in Huntington's disease and the functional disability is not clear, applications of recently developed neural connection models have implicated a number of important brain-behavior associations. Preclinical diagnostic procedures have evolved through successive iterations that have each contributed to increased reliability. New functional brain imaging techniques are sure to add to this promising domain in the future. Preclinical diagnosis has been stimulated by the recent isolation of the Huntington's gene which has also rekindled awareness of the importance of informed genetic counselling and the inherent ethical dilemmas in genetic testing. Treatment approaches to Huntington's disease have been confined to palliative care with secondary symptom management and psychotherapeutic support. Experimental therapeutic strategies for the illness itself have had a rather disappointing record to date. Further developments in NMDA antagonism and neural cell grafting may provide some hope for the future.