Wisconsin Card Sorting Test synchronizes the prefrontal, temporal and posterior association cortex in different frequency ranges and extensions

Abstract

Current findings show some brain regions consistently related to performance of the Wisconsin Card Sorting Test (WCST). An increase of local cerebral blood flow or metabolic demands has been detected in those regions. Functional integration of the neuronal circuits that subserve the task performance, based upon the identification of the oscillations and their distributed cerebral sources, has not been accomplished previously. The event-related tonic oscillations within a period of 2,000 msec after the stimulus onset and the probable neural substrate were evaluated in healthy volunteers by variable-resolution brain electrical tomography (VARETA). The WCST induced a significant increase of delta, theta, beta-2, and gamma oscillations, but decrease of alpha. Areas such as the frontal subregions, temporal, cingulate, parahippocampal, parietal, occipitotemporal cortex, and occipital poles showed modified activity during the task, with EEG spectral band selectivity as well as some overlapping among them. Frontal and temporal regions generated the delta/theta oscillations. Additionally, the occipitotemporal and parietal regions were the source of the delta activity, lacking theta activation. The parietal region also showed tonic alpha, beta-2 and gamma changes. These data imply that different processes have been simultaneously mediated during task performance. Relationships among the individual bands, the neural substrata and the specific cognitive process that support the task were established. The selectively distributed delta, theta, alpha, beta-2 and gamma oscillations reflect communication networks through variable populations of neurons, with functional relations to the working memory functions and the information processing that subserve the WCST performance.

Figure 1

The WCST, as presented on the computer monitor. Top row: the reference card including the three categories; bottom row: the target card.

Figure 2

Brain electrical tomography (VARETA) in the frequency domain. The cortical sources of maximum to δ oscillations during the WCST on the average brain from the PBA are showed. The images show different activated region in the δ range resulting in functional interconnected areas, that sustain the test performance. In the top row the picture corresponds to the activation of the frontotemporal regions (a) and the ventro‐occipitotemporal area (b). The row at the bottom shows a coronal section of the activated temporal areas (inferotemporal, parahippocampal). Plane of sections are in Talairach space: (a, b) sagittal x = 21, (c) coronal y = −18. R, right; L, left; A, anterior; P, posterior. Scale refers to P‐values. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Figure 3

VARETA. Regions with a maximal peak for the θ oscillations with different patterns of activation are shown. The bilateral frontotemporal activation (right) in a particular frequency, in contrast to the interhemispheric asymmetry for another θ frequency (left), can be observed. There are areas that participate in more than one network. Plane of axial section: Z = 0. (Talairach space). Scale refers to P‐values. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Figure 4

VARETA. The maximum of inhibition of the α range during the WCST solution. α desynchronization occurs over wide areas of the scalp, such as the right occipitotemporal region (A) or restricted to the right parietal area (B). R, right; L, left; A, anterior; P, posterior. Scale refers to P‐values. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Figure 5

VARETA. Right: the sources of β‐2 oscillation restricted to a small region in the left hemisphere, while the contralateral region (left) develops γ oscillation. Note the selective laterality to the oscillations. Scale refers to P‐values. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]