This project has employed paradigms in which people are asked to complete two tasks that overlap in time to isolate temporal relationships among elementary cognitive processes that are impaired versus intact in schizophrenia, particularly as they are related to central executive processes. The project has translated to schizophrenia research a series of dual-task interference paradigms from cognitive psychology that:
(1) have particular promise to differentiate between two distinctive models of attentional functioning
(2) offer opportunities to isolate which elementary cognitive processes are sources of attentional limitation because they cannot be completed simultaneously (Nuechterlein et al, 2006).
Four studies have been carried out to examine alternative loci for processing bottlenecks during divided attention in prodromal, first episode, and chronic schizophrenia patients. Reaction time studies detect a pause in Task 2 while central decision and response selection is completed in Task 1.
Briefly, the findings from this Project indicate that a structural processing bottleneck model accounts for divided attention in these paradigms in schizophrenia better than a processing resource model. The divided attention deficits in schizophrenia are evident in greater than normal temporal interference when tasks overlap substantially. Exaggerated structural processing bottlenecks are evident for response selection and motor processes in schizophrenia, but perceptual encoding seems to be completed in parallel without interference in schizophrenia as it is in normal subjects (Nuechterlein et al, submitted; Nuechterlein et al, in prep). A new paradigm to examine processing bottlenecks in motivated, hedonic decision-making situations has also been developed (Pashler et al, 2008).