Functional Organization of the Brain during Preparation for Recognition of Image Fragments

Abstract

Studies in adult subjects (n = 36) analyzed functional interactions in the prefrontal areas of the cortex with other cortical zones during preparation to recognize incomplete figures with different levels of fragmentation during sequential approximation to the complete image. Functional interactions were measured in terms of the imaginary part of the complex coherence of the EEG α rhythm. The nature of rearrangements in intracortical interactions was found to differ in subjects with high and low levels of recognition success. In successful subjects, changes in intracortical interactions during the period preceding as yet unrecognized stimuli occurred mainly in the right hemisphere, while during the period preceding recognized stimuli changes were mainly in the left hemisphere. In this group of subjects, α-rhythm coherence in both hemispheres increased in the situation of focused attention as compared with the situation of nonspecific attention. In unsuccessful subjects, conversely, α-rhythm coherence levels in both the right and left hemispheres decreased significantly on focused attention as compared with nonspecific attention. These results provide evidence that the co-tuning of electrical activity in the cortical zones, in terms of the α rhythm, is one of the mechanisms of their functional unification during the period of preparation to recognize incomplete figures.