Corpus callosum size and diffusion tensor anisotropy in adolescents and adults with schizophrenia.

The corpus callosum has been implicated as a region of dysfunctional connectivity in schizophrenia, but the association between age and callosal pathology is unclear. Magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI) were performed on adults (n=34) and adolescents (n=17) with schizophrenia and adult (n=33) and adolescent (n=15) age- and sex-matched healthy controls. The corpus callosum was manually traced on each participant׳s MRI, and the DTI scan was co-registered to the MRI. The corpus callosum was divided into five anteroposterior segments. Area and anisotropy were calculated for each segment. Both patient groups demonstrated reduced callosal anisotropy; however, the adolescents exhibited reductions mostly in anterior regions while the reductions were more prominent in posterior regions of the adults. The adolescent patients showed greater decreases in absolute area as compared with the adult patients, particularly in the anterior segments. However, the adults showed greater reductions when area was considered relative to whole brain white matter volume. Our results suggest that the initial stages of the illness are characterized by deficiencies in frontal connections, and the chronic phase is characterized by deficits in the posterior corpus callosum; or, alternatively, adolescent-onset schizophrenia may represent a different or more severe form of the illness.

Cigarette smoking and measures of impulsivity in a college sample.

BACKGROUND: An association between impulsivity and smoking has been consistently reported in the literature, but few studies have examined how distinct dimensions of impulsivity may relate differentially to smoking initiation versus persistent smoking. The aim of the current study was to examine the relationship between self-report and behavioral measures of impulsivity and smoking status in college students. METHODS: Participants (N = 243) completed a self-report history of tobacco use, 2 self-report measures of impulsivity (the Barratt Impulsiveness Scale and Zuckerman Sensation-Seeking Scale), and 2 behavioral measures (the Delay Discounting Task and Iowa Gambling Task). All participants were classified as never-smokers, triers, or smokers based on their smoking history, and between-group differences on the 4 measures were examined. RESULTS: On the self-report measures, all 3 groups differed on sensation seeking, with the never-smokers reporting the lowest levels and the smokers reporting the highest. Furthermore, the smokers reported significantly higher disinhibitory impulsivity than the triers and never-smokers. The groups did not differ on the behavioral measures. CONCLUSIONS: These results indicate that distinct dimensions of impulsivity characterize different smoking phenotypes. In particular, sensation seeking is associated with the initiation of smoking, whereas disinhibitory impulsivity is associated with the transition to more persistent and regular use of cigarettes.