Nozomi Naoi

機能的近赤外分光法 (fNIRS) は, 簡便性, 拘束性の低さなどの特徴からも, 多くの認知神経科学的研究が行われてきた。本稿では, その中でも発達認知神経科学の領域に着目し, 定型発達脳と自閉症スペクトラム障害 (ASD) という非定型発達脳について我々の fNIRS 研究をもとに述べる。最初に触覚という知覚処理の脳機能の違いを定型群と発達障害群で比較検討した研究からは, Aβ線維由来, CT 線維由来の機能の異なる触覚刺激の違いに関わらず ASD 群は前頭前野の反応が弱く, 心拍反応も弱いことが示された。ASD 群は社会的タッチと呼ばれるCT線維由来の触覚だけに違いがあるわけではない可能性が示された。続いて, ASD 児の発達支援前と支援後で fNIRS 計測し, 支援効果を客観的に評価する試みと現在得られている結果について紹介する。以上は, fNIRS が発達脳の基礎研究ばかりでなく臨床的にも充分応用できる可能性があることを示している。

Preterm infants are at increased risk of language-related problems later in life; however, few studies have examined the effects of preterm birth on cerebral responses to speech at very early developmental stages. This study examined cerebral activation and functional connectivity in response to infant-directed speech (IDS) and adult-directed speech (ADS) in full-term neonates and preterm infants at term-equivalent age using 94-channel near-infrared spectroscopy (NIRS). The results showed that compared with ADS, IDS increased activity in larger brain areas such as the bilateral frontotemporal, temporal, and temporoparietal regions, both in full-term and preterm infants. Preterm infants exhibited decreased activity in response to speech stimuli in the right temporal region compared with full-term infants, although the significance was low. Moreover, preterm infants exhibited increased interhemispheric connectivity compared with full-term controls, especially in the temporal and temporoparietal regions. These differences suggest that preterm infants may follow different developmental trajectories from those born at term owing to differences in intrauterine and extrauterine development.

In human verbal communication, not only lexical information, but also paralinguistic information plays an important role in transmitting the speakers’ mental state. Paralinguistic information is conveyed mainly through acoustic features like pitch, rhythm, tempo and so on. These acoustic features are generally known as prosody. It is known that some species of birds can discriminate certain aspects of human speech. However, there have not been any studies on the discrimination of prosody in human language which convey different paralinguistic meanings by birds. In the present study, we have shown that the Java sparrow (Padda oryzivora) can discriminate different prosodic patterns of Japanese sentences. These birds could generalize prosodic discrimination to novel sentences, but could not generalize sentence discrimination to those with novel prosody. Moreover, unlike Japanese speakers, Java sparrows used the first part of the utterance as the discrimination cue.