Deficits of information processing in schizophrenia
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The deficit of information processing is one of the core characteristics of patients with schizophrenia and at-risk populations. A deficit in capacity of information processing is especially a well-established marker, which suggests that it is biologically connected. Recently, it was proposed that slowness in information processing in schizophrenia is also biologically connected, and this is consistent with bradyphrenia, slowness of cognitive processing, which is a major characteristic of a subcortically-based brain disorder.;This study has two goals: the first is to find the point at which the deficiency of capacity of information processing becomes evident, and the second is to examine slowness of information processing for patients with schizophrenia, a clinically-at-risk population, and a genetically-at-risk population (healthy siblings of the patients). Their capacity and slowness of information processing are tested by using the Continuous Performance Test-Identical Pair (CPTIP).;A total number of 69 participants were included in this study. Twenty of them were probands, 27 of them were siblings and 22 of them were RAPP patients. Their age range was from 11 to 26, and majority of them was males.;The results indicated that both probands' and RAPP patients' deficits in capacity of information processing became evident with the lightest information load condition compared to healthy siblings. For the siblings, their performances on the CPT-IP declined in the highest processing demand task. In the speed of information processing comparison, all three groups did not show any significant improvement from shorter to longer duration of the time of stimulus in the CPT-IP.;There are three other findings from this research: First, as difficulty of the task increased, response bias became more liberal for all three groups, which implies that they tended to respond more positively as the task got harder. Second, this research demonstrates that sensitivity and response bias measures are independent from each other. Third, a parametric measure of sensitivity of the CPT-IP (d') is highly correlated with a nonparametric sensitivity index (A'), therefore, it is reasonable to use the more widely known parametric sensitivity index for future research.