本研究では，自然には存在しない感覚反転環境を用いることで，人間の脳内における多感覚統合処理を明らかにすることを目的としている．3か年計画の2年目となる平成30年度においては，まず，平成29年度に構築したヘッドマウントディスプレイと脳波計の同時利用による前庭感覚反転システム，および聴覚ウェアラブルデバイスと脳磁計の複合利用による聴覚反転システムの強化を行った．具体的には，実験参加者が直立姿勢または倒立姿勢となるような前庭感覚反転システムにおいて脳波計のワイヤレス化を行い，実験参加者の動作に伴って発生する電磁気ノイズを低減した．また，右耳（左耳）に呈示された音が左耳（右耳）に届くような聴覚反転システムにおいて，マルチスピーカーシステムを別途構築し，全方位の音源定位評価を実現した．次に，強化したシステムを用いて，感覚反転環境に対する順応の効果を脳計測によって調べた．いずれの感覚反転環境への接触直後でも，視覚情報とのミスマッチに由来する誤差伝播に固有な脳リズムが連合野で観測された．また，継続的な順応が可能な聴覚反転環境では，この脳リズムが順応の進行とともに減少していった．従来，多感覚統合処理を調べるにあたっては，単一感覚の処理で説明不可能な脳活動を抽出する差分手法が取られてきた．しかし，環境適応性に関わるこれらの知見は脳活動の量的な検討では得られないものであり，平成31年度の研究に繋がるものである．一方で，触覚反転環境については，デバイス面でシステムの構築に問題を抱えている．したがって平成31年度には，順応期間延長による聴覚反転環境への更なる環境適応性と定着性の検討に加えて，デバイスの再考による触覚反転システムの構築を実現し，多感覚統合機能の一般性を考察していく必要がある．
This study aims to clarify multisensory integration processing in the human brains by using reversed sensory environment that is impossible in a natural situation. In the second year (2018) of the 3-year plan, first, two experimental systems constructed in 2017 were strengthened: a reversed vestibular system with simultaneous use of a head mounted display and electroencephalography and a reversed auditory system with combinational use of an auditory wearable device and magnetoencephalography. Specifically, as for the reversed vestibular system that manipulates participants' body tilt to be either normal or inverted, electromagnetic noise produced by participants' movement was reduced by making the electroencephalographic device wireless. For the reversed auditory system in which a sound presented to right (left) ear was delivered to the left (right) ear, evaluation of omni-azimuth sound source localization was achieved by constructing the multiple speaker system separately. Next, brain activity was measured to examine the effects of adaptation to the reversed sensory environment using the strengthened systems. Immediately after the exposure to both reversed sensory environment, the brain oscillation specific to error propagation due to mismatch with visual information was observed in the association cortex. Moreover, in the reversed auditory environment in which continuous adaptation is possible, this oscillation was decreased along with the progress of the adaptation. Conventionally, in order to investigate the multisensory integration processing, a subtraction method has been used to extract brain activity that is difficult to explain by unisensory processing. However, these knowledge involving environmental adaptability cannot be obtained by quantitative discussion of brain activity, and leads to research in 2019. On the other hand, reversed somatosensory environment has a problem with system construction on the device side. Accordingly, in 2019, it is necessary to achieve the reversed somatosensory system by reconsidering the devices and to discuss generality of the multisensory integration function in addition to further examination of environmental adaptability and stability to reversed auditory environment with prolonged adaptation period.