ATTENTION AND DUAL-TASK INTERFERENCE

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We propose to use a translational behavioral science strategy to bring paradigms with greater analytic power to the study of attention in schizophrenia and also to develop further basic paradigms of relevance to schizophrenia. Dual-task interference studies have particular promise for clarifying the processes involved in attentional limitations in schizophrenia. They allow direct tests of whether impairments during performance of two overlapping tasks are due to specific forms of central structural bottlenecks, as opposed to the graded capacity sharing that would be predicted by processing resource limits. Using a specific type of dual-task paradigm, the Psychological Refractory Period paradigm, it is also possible to identify the locus of structural processing bottlenecks, that is, processing points at which certain cognitive operations cannot be completed simultaneously. Five studies at UCLA with 96 prodromal, 100 first-episode, and 80 chronic patients and equal numbers of demographically comparable normal subjects will use Psychological Refractory Period paradigms that have well-documented utility in basic cognitive research for detecting and locating a processing bottleneck in dual-task performance. The first four will test whether the "cognitive architecture" affecting dual-task interference is altered in persons with prodromal symptoms or in first-episode or chronic schizophrenia patients, such that the processing bottleneck includes perceptual encoding or response production in addition to response selection processes. The fifth clinical study will examine whether retrieval from long-term memory is a component of the central bottleneck as it is in normal subjects and, if so, whether memory retrieval causes an abnormally large disruption (i.e. longer delay) in dual-task performance in the patients. Short-term longitudinal studies will determine whether certain components of dual-task interference become more severe over time, predict psychosis onset, and are particularly strong predictors of functional outcome. Predictive contributions of perceptual encoding, memory retrieval, response selection, and response production processes will be differentiated. While these initial clinical studies are completed, development of basic cognitive paradigms at UCSD will address critical issues concerning preparatory processes in dual-task situations. Deficits in other preparatory processes and in working memory in schizophrenia indicate the relevance of developing these new paradigms, which will later be applied in refined form with clinical samples at UCLA. This research should substantially increase our understanding of the links between specific forms of attentional impairment, symptom development, and functional outcome in schizophrenia.