Study of neural mechanisms of biofeedback using magnetoencephalography

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The purpose of this study was to clarify the neural process underlying the neurofeedback(or biofeedback) by using the magnetoencephalography (MEG) and fMRI. Two experiments were carried out. In Experiment 1, subjects were exposed to a series of visual and auditory inputs andwere instructed to detect a specified combination of color and tone. MEG was measured during the task. Source localization was performed based on the MEG. The result showed the following spatiotemporal features of neural activities relating to the task : In 90-130ms after onset of the input, neural activities were observed in both visual and auditory cortices, and in 160- 210ms they were in association areas in temporal and parietal cortices, while in 130-150ms and in 220-240ms they were in basal ganglia and the limbic system. The result shows the basal ganglia and the limbic system play an important role in the phase change in the discrimination task. Considering their mutual connection with the brain stem, they would constitute an informational path from the sensory system to the autonomic system enabling the learning in neurofeedback. In Experiment 2, an ambiguous random dot stereogram was displayed with a constant depth increase, whereas the subjects were trained to make a reciprocal depth sensation, which was possible due to the ambiguity. For each subject fMRI was measured during the task and neural activities were located on the MRI image. The result showed the activity in the prefrontal cortex as well as the visual cortex. In performing the task, subjects were required to break an existed frame of perception and make another one. It corresponds to the state alteration of consciousness, which play an crucial part in the learning process of neurofeedback. The result of Experiment 2 strongly suggests the importance of the prefrontal activity in the neurofeedback.