fMRI Investigation of an Experimental Executive Function Measure: Comparison of the Texas Card Sorting Test to the Wisconsin Card Sorting Test in Healthy Adults
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Although executive functioning is one of the most studied constructs in neuropsychology, it remains one of the most elusive and enigmatic skill sets to measure and understand. The Wisconsin Card Sorting Test (WCST) is commonly used to assess executive functioning, though it has been criticized for its lengthy administration time and negative feedback component. The Texas Card Sorting Test (TCST) was developed as a problem-solving measure to be applied in linguistically diverse samples, and does not have the limitations of the WCST. The overall purpose of the present study was to validate the TCST as a measure of frontal and subcortical function, and to compare the TCST to the WCST. Twenty-five healthy volunteers underwent functional magnetic resonance imaging (fMRI) while performing computerized versions of the WCST and TCST. Significant activations during the TCST were observed in the prefrontal cortex (BA 6, 9, 44-47), the basal ganglia, bilateral parietal areas (BA 7&39), left cingulate gyrus (BA 24, 31,&32), right superior temporal areas (BA 41&22), left parahippocampal and middle temporal gyri, and right occipital lobe (BA 18&19). Compared to the WCST, the TCST showed increased activity bilaterally in the frontal lobe (BA 6&47), right frontal areas (BA 10&11), the caudate, right superior temporal lobe (BA 38, 41, 42), right temporal lobe (BA 22&34), and left occipital lobe (BA 19&31). Behaviorally, no significant correlations were seen between the WCST and TCST performance variables. This research supports the TCST as a measure of frontal-subcortical function. The TCST appears to be particularly sensitive to orbitofrontal/caudate circuitry as well as superior temporal areas, with greater activation overall observed in right cerebral areas. Given the lack of correlation on behavioral performance variables and the distinct differences in neural correlates, the TCST may assess cognitive processes that are different from the WCST. The TCST has promising potential as a clinical neuropsychological instrument.