カオス解析を用いた快－不快情動の定量評価

摘要

近年，日本では介護を必要とする高齢者が増加してい冬．特に，発話や四肢体動による意思伝達機能を失った重度の要介護者の場合，感情や身体的・精神的苦痛に対する客観的な判断が求められることから，情動の定量評価技術の確立は重要な課題である．従来研究では，感情の評価として脳機能イメージングを用いた手法が行われているが，脳の複雑性に着目して情動評価を行った研究は少ない・そこで，本研究では基礎検討としてカオス解析の指標であるリアプノフ指数を用いて感情の背景因子である快－不快情動を定量評価した．具体的には，安静時及び不快音聴取時の前頭葉における酸素化ヘモグロビン濃度の時系列変化からリアプノフ指数を算出して比較検討を行った．実験の結果，不快昔聴取時は安静時に比べリアプノフ指数が有意に小さく，また心理変化量との間に中程度以上の相関がみられたことから，提案手法が快－不快情動の定量評価において有効な指標となる可能性を示した．%Recently, aged people who require nursing care is expected increase in Japan. Especially, in case of people requiring intensive nursing care due to severe difficulty in communication by means of speech or gesture, objective evaluation of their emotional states as well as physical or mental pain is required. Therefore, it is important to establish the method for objective evaluation of emotions. Functional neuroimaging has been used so far to evaluate objective evaluation of emotions. However, there are few studies that evaluated emotions by focusing on complexity of the brain. Therefore, we aimed to preliminarily evaluate pleasant - unpleasant emotions quantitatively by using the lyapunov exponent that is an index of chaotic states. The lyapunov exponents calculated from temporal change of oxygenated hemoglobin concentration in the prefrontal region were compared between during the resting state and during listening to an unpleasant sound. As a result, the lyapunov exponent during listening to an unpleasant sound was significantly lower compared with that during the resting state. There was moderate or more than moderate correlation between the lyapunov exponent and the pleasant - unpleasant psychological value measured using a visual analog scale. These results suggest that our method is a useful index for emotional evaluation.