Objective Abnormal 50 and 100ms event-related brain activity derived from paired-click procedures are a well established finding in schizophrenia. There is little agreement on whether ratio score (second click/first click) paired-click group differences reflect an encoding or gating abnormality. In addition, the functional implications of the ratio score deficit remain unclear. In the present study, EEG and MEG were used to examine paired-click measures as well as the cognitive correlates of paired-click activity. Method Electroencephalographic (EEG) Cz and whole-cortex magnetoencephalographic (MEG) data were acquired during the standard paired-click paradigm in 73 controls and 79 patients with schizophrenia. Paired-click ratio scores were obtained at 50ms (P50 at Cz, M50 at left and right superior temporal gyrus, STG) and 100ms (N100 at Cz, M100 at left and right STG). Subjects were administered a cognitive battery assessing attention, working memory, and long-delay memory. An IQ estimate was also obtained. Results Groups differed on ratio score and S1 amplitude measures. 50ms and 100ms ratio and S1 amplitude scores predicted variance in attention (primarily S1 amplitude), working memory, and long-delay memory. The attention findings remained after removing variance associated with general cognitive ability (i.e., IQ). Conclusions Associations between paired-click measures and cognitive performance in patients supports 50ms and 100ms ratio and amplitude scores as clinically significant biomarkers of schizophrenia. In general, cognitive performance was better predicted by the ability to encode auditory information rather than the ability to filter redundant information.
A growing body of evidence suggests that moderate to vigorous activity levels can affect quality of life, cognition, and brain structure in patients diagnosed with schizophrenia. However, physical activity has not been systematically studied during the period immediately preceding the onset of psychosis. Given reports of exercise-based neurogenesis in schizophrenia, understanding naturalistic physical activity levels in the prodrome may provide valuable information for early intervention efforts. The present study examined 29 ultra high-risk (UHR) and 27 matched controls to determine relationships between physical activity level, brain structure (hippocampus and parahippocampal gyrus), and symptoms. Participants were assessed with actigraphy for a 5-day period, magnetic resonance imaging (MRI), and structured clinical interviews. UHR participants showed a greater percentage of time in sedentary behavior while healthy controls spent more time engaged in light to vigorous activity. There was a strong trend to suggest the UHR group showed less total physical activity. The UHR group exhibited smaller medial temporal volumes when compared to healthy controls. Total level of physical activity in the UHR group was moderately correlated with smaller parahippocampal gyri bilaterally (right: r=.44, left: r=.55) and with occupational functioning (r=−.36; of negative symptom domain), but not positive symptomatology. Results suggest that inactivity is associated with medial temporal lobe health. Future studies are needed to determine if symptoms are driving inactivity, which in turn may be affecting the health of the parahippocampal structure and progression of illness. Although causality cannot be determined from the present design, these findings hold important implications for etiological conceptions and suggest promise for an experimental trial.
Behavioral inhibition is a temperamental trait that refers to slow approach to novel items, shyness towards new people, and fearfulness in new situations, and individuals may develop inhibited response styles by as early as two years of age. There are important methodological considerations in the assessment of early temperament, with parental report and observational measures providing both corroborative and unique data. The present study examined behavioral inhibition measured by parental report and observational measures in a genetically informative sample to delineate the agreement between the methods and the uniqueness of each method, and to estimate the magnitude of genetic and environmental influences on the common and unique variance. The biometric, psychometric, and rater bias models were conducted to study the covariance between measurement modalities. Overall, the results suggested a common phenotype was assessed by both parents and observers. The latent phenotype underlying parental and observational measures of behavioral inhibition was moderately to substantially heritable.
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