Over the past thirty years a significant amount of research has accumulated showing the correlation of oscillatory activity with learning, memory, and perception. A new paper “Oscillatory Synchronization in Large-Scale Cortical Networks Predicts Perception” (published January 27, 2011 in Neuron) provides evidence that dynamic networks across cortical areas phase-lock and synchronize their oscillatory activity to support perception. The research team developed a new analysis method using electroencephalography (EEG) and magnetic resonance imaging (MRI) data that enabled an unbiased search for synchronized networks across the entire human brain.
Note: Supplemental information for this paper is available in a twenty-two page PDF file.
In the experiments described in this paper, human subjects reported the way they experienced an ambiguous audiovisual stimulus of two approaching bars that crossed over and then continued to move apart from each other. At the moment that the two bars crossed, a click sound was played. Perception of this stimulus spontaneously alternated between two bars bouncing off of each other and one bar passing the other. The addition of the click increased the relative frequency that subjects saw the bars bouncing off each other, which points to the integration of the visual and auditory stimuli.
The major finding emerged when the authors compared cortico-cortical coherence at the source level between stimulation and baseline periods. A highly structured cortical network showed enhanced beta frequency coherence (15–23 Hertz) during stimulation. This network included the extrastriate visual areas, the frontal eye fields, and posterior parietal and temporal cortices. Most striking, the authors found that beta synchrony was not only enhanced during stimulus processing, but also predicted the subject’s perception of the stimulus as two bars bouncing off of each other.
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