Fourth International School On Mind, Brain And Education

2009, August 1-5

Hitachi, JAPAN

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Wearable optical topography for measurement of mutually interactive anterior prefrontal activity
Optical topography, a noninvasive modality for measuring brain function, is widely used to measure the brain activity of infants and children because it has a high level of safety and low constraints. We have developed a wearable optical topography (WOT) system that enables the simultaneous measurement of the brain functions of two or more people wearing an optical topography device and interacting in a natural manner (Atsumori, 2009). The wearable device covers the prefrontal cortex, where the frontal pole is related to sociality and the dorsolateral prefrontal cortex (DLPFC) is related to working memory and ethical assessment.
As ethical sense and sociality are related to the brain functions that occur when people interact, we have been trying to measure the brain functions that are related to the interactions with others by the simultaneous measurement of two or more people to understand the mechanism of ethical sense and sociality. Therefore, we used a simple task for measuring the mutually interactive anterior prefrontal activity using our WOT system. In an experiment, we measured the changes in the volume of cerebral blood of two people wearing an optical topography device. In each trial, they were told to push their button after counting ten seconds in their mind, and they were also told to adjust their timing so that it matched that of the other person. They kept closing their eyes during the experiment. The start time of counting and button pushing timings of the two people were presented by using short beep sounds from a speaker, and each button pushing time was recorded by a PC. There were ten trials with 20-s rest periods between trials. We found that in the frontal pole and DLPFC, when the temporal correlation between their brain activities was higher, the time lag between their button pushing was shorter. In some trials, the time lag was shorter than the reaction time of a go/no-go task performed by two people. These results probably show the effects of cooperation. They also suggest that the synchronization of the brain activities of two or more people is associated with their performance when they cooperate. The process of mutually adjusting the button pushing timing in each trial using the previous trial result is a cooperative working in this experiment.
We have demonstrated that investigating the relationship between the brain activities of two or more people when they interact is important and that our WOT system is suitable for this purpose. We will use this system to elucidate the brain functions that are related to interaction with others and use an approach based on brain science to investigate the mechanisms of ethical sense and sociality.