嚥下の神経機構

The Neural Mechanisms Underlying Swallowing

嚥下は，反射性にも随意性にも誘発可能な運動である。また，嚥下は必要な栄養や水分を口腔から咽頭，食道を経て胃へと送り込む消化管活動であるだけでなく，誤嚥や窒息を防ぐための防御反応でもある。嚥下運動の誘発とパターン形成に関わるのは延髄のパターン発生器と呼ばれる細胞集団であり，咽喉頭からの入力や大脳皮質などからの入力が閾値を超えることにより，一連の活動が引き起こされる。

Abstract

Swallowing is regarded as the first step in nutrition; it transports food boluses and liquid from the mouth to the stomach and is a defensive response to prevent aspiration. Swallowing movements are produced by a central pattern generator (CPG) located in the lower brainstem. The swallowing CPG includes two main groups of neurons: one is located within the nucleus tractus solitarii and contains the generator neurons involved in triggering, shaping, and timing the sequential or rhythmic swallowing pattern and the other is located in the ventrolateral medulla and contains switching neurons that distribute the swallowing drive to various pools of related motoneurons. Swallowing movements can be triggered by either central inputs or peripheral inputs from pharyngeal and laryngeal regions, but the precise neural mechanisms of the swallowing CPG remain to be fully elucidated. This review discusses the fundamental knowledge of ingestion behaviors, with a focus on swallowing.