網膜の光感受性細胞と気分や認知に関わる皮質脳領域をつなぐ神経経路の理解が深まり、気分障害の治療法開発につながる。 Improved understanding of a neural pathway connecting light-sensitive cells in the retina with the cortical brain regions involved in mood and cognition has implications for the development of treatments for mood disorders.
2022-07-06 ブラウン大学
このたび、ブラウン大学の科学者たちは、その理由を明らかにしました。
『米国科学アカデミー紀要』に掲載されたこの新しい研究で、研究チームは、機能的MRIを用いて、光の強さの信号が脳に到達する仕組みと、気分に関与する脳構造がその信号を処理する仕組みを明らかにした。その結果、認知処理や気分に関与する大脳皮質の一部の領域が、光の強さに対して感受性を示すことが明らかになりました。
この発見は、季節性情動障害や大うつ病性障害などの気分障害の理解や治療法につながるものだ.。
<関連情報>
光による気分および認知への影響の基質となりうるヒト前頭前野のluxotonic信号 Luxotonic signals in human prefrontal cortex as a possible substrate for effects of light on mood and cognition
Shai Sabbah , Michael S. Worden, Dimitrios D. Laniado , David M. Berson and Jerome N. Sanes
Proceedings of the National Academy of Science Published:July 6, 2022
DOI:https://doi.org/10.1073/pnas.2118192119
Significance
Humans sense changes in ambient illumination, thus luxotonic properties, unrelated to form vision, and these changes influence a wide range of functions, including circadian rhythms, visual reflexes, mood, and likely cognitive processing. While image-forming pathways in the primate brain detect minute changes in illumination, it remains unclear how light-intensity signals reach and become processed in brain structures involved in basic moods and their dysfunction, pathways that likely derive from intrinsically photosensitive retinal ganglion cells. Here, we show that prefrontal regions in the human brain have luxotonic signals. These signals have properties similar to intrinsically photosensitive retinal ganglion cells, and they may underlie light-intensity effects on complex behaviors.
Abstract
Studies with experimental animals have revealed a mood-regulating neural pathway linking intrinsically photosensitive retinal ganglion cells (ipRGCs) and the prefrontal cortex (PFC), involved in the pathophysiology of mood disorders. Since humans also have light-intensity–encoding ipRGCs, we asked whether a similar pathway exists in humans. Here, functional MRI was used to identify PFC regions and other areas exhibiting light-intensity–dependent signals. We report 26 human brain regions having activation that either monotonically decreases or monotonically increases with light intensity. Luxotonic-related activation occurred across the cerebral cortex, in diverse subcortical structures, and in the cerebellum, encompassing regions with functions related to visual image formation, motor control, cognition, and emotion. Light suppressed PFC activation, which monotonically decreased with increasing light intensity. The sustained time course of light-evoked PFC responses and their susceptibility to prior light exposure resembled those of ipRGCs. These findings offer a functional link between light exposure and PFC-mediated cognitive and affective phenomena.
