Neuropsychological indicators of heteromodal cortex (dys)function relevant to conditioned blocking measures of attention in schizophrenia
Background. Learning a predictive relationship between two events can block learning about an added event (conditioned blocking, CB). Patients with nonparanoid schizophrenia can show reduced CB and learn about the similar consequences of the added event. What parts of the brain are involved in the functions required in learning the CB task and actually showing 'blocking' - a part of normal selective attention processes? As a first approximation, we ask if neuropsychological test performance sensitive to specific cortical regions is associated with these two functions. Methods. This study reports on the relationship of associative learning and CB measures of attention obtained with a visuospatial maze-like task to signs of heteromodal cortex function provided by performance on a battery of 10 neuropsychological tasks. These tasks were sensitive to frontal, parietal and temporal lobe function of the left and right hemisphere. Acquisition criteria for the task were achieved by 62 patients with schizophrenia and 62 matched controls but not by 39 other people with schizophrenia. Results. First right-hemisphere, visuo-spatial abilities were generally associated with faster task-learning (e.g. visual reproduction, immediate and delayed, picture-completion), and patients that could not learn the task were poorer on tests emphasising set-switching and problem-solving abilities associated with left frontal lobe function (e.g. trail-making, block-design). Second CB expression depended on Stroop- and Mooney-faces-task performance that are reported to require cingulate and parietal lobe function. Conclusions. As would be predicted right hemisphere function was implicated in performing a visuospatial learning task. The additional CB requirement incurred additional anterior cingulate and right parietal involvement. Functionally this probably reflected effortful attentional processes, and illustrates the problems of patients with schizophrenia in switching between automatic and controlled processing strategies. The results are astonishingly consistent with imaging studies implicating brain regions such as the cingulate and intra-parietal sulcus in attention (Mesulam, 1999)
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