The Japanese journal of neuropsychology

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ArticleTitle	Neuroimaging studies and neuropsychology
Language	J
AuthorList	Katsuyuki Sakai
Affiliation	Tamagawa University, Brain Science Institute
Publication	Japanese Journal of Neuropsychology: 31 (1), 34-41, 2015
Received
Accepted
Abstract	Neuropsychological research has contributed to the understanding of functional organization of the human brain based on the association between focal brain lesion and symptoms. Neuroimaging studies, on the other hand, have identified brain activation patterns while normal human subjects perform cognitive tasks that require a particular aspect of perception, action, and thought processes. In contrast to the localized functional brain map suggested by patient studies, neuroimaging studies very often show overlapped brain activation pattern between two completely different cognitive tasks. This suggests that a given cognitive task can be performed by not just a single dedicated brain region but a set of functionally-connected brain regions. In order to identify the interaction between brain regions, techniques to examine the functional connectivity has been developed. These techniques, however, do not offer information about the direction of signal transmission between brain regions. In this chapter, I am going to show a novel technique to examine the efficacy of signal transmission between brain regions based on transcranial magnetic stimulation (TMS) and electroencephalography. When we stimulate a particular brain region with a single pulse TMS, the activation is first induced in the stimulated region. The activation then spreads toward distant regions at about 10 msec. It then moves back to the stimulated region, and spreads more widely to distant regions. This back-and-forth sequence of signal transmission changes depending on task conditions, which indicates the functional status of the brain network. The pattern of neural signal transmission also shows history-dependent modulation, and this pattern can be dissociated from the pattern of regional activation. An interesting possibility is that this technique can be used to make inference about synaptic functions in the human brain. I believe that such biological understanding of the human brain function contributes to the assessment and treatment of neuropsychological symptoms of patients.
Keywords	functional magnetic resonance imaging, transcranial magnetic stimulation, functional connectivity, efficacy of signal transmission