Droge M H, Leonard R B
J Neurophysiol. 1983 Jul;50(1):178-91. doi: 10.1152/jn.1983.50.1.178.
Rhythmic motoneuronal activity was recorded from decerebrated, paralyzed stingrays and compared with electromyograms recorded from the same animals. Before and after paralysis, a rostral-to-caudal sequence of alternation occurred between dorsal (elevator) and ventral (depressor) efferents. The swimming pattern was thus observed in the absence of phasic afferent input, and this constitutes fictive locomotion. After paralysis, both the intersegmental delay (time between activation at progressively caudal recording sites) and the burst duration remained linearly related to the swim cycle period. In many instances, neither the slope nor the intercept was significantly altered by immobilization. The intercepts all fell near the origin, indicating that the fictive rhythm remains constant phase coupled. Although the swimming rhythm was obtained after paralysis, some differences occurred. These included fewer and shorter spontaneous sequences, a greater range of cycle periods, and longer burst durations. During fictive swimming, the burst duration:cycle period ratio usually increased to 0.53 from 0.39 observed before paralysis. Therefore, the silent periods seen between burst discharges in antagonist efferents during movement were often absent after paralysis. Mechanical stimulation of the tail reduced both cycle periods and burst durations; however, the burst:cycle ratio remained greater than or equal to 0.50. The linear relation between burst duration and cycle period found for spontaneous sequences was not changed by stimulation of the tail. During fictive swimming the inter- and intrasegmental coupling that characterizes stingray swimming becomes labile. Abnormal coupling appears more often during sequences with long swim cycles. Intrasegmental coupling is tighter than intersegmental coupling at any cycle period. Rhythmic activity at one segmental level can be independent of activity at other levels. This suggests that multiple oscillator circuits exist that are not dependent on propriospinal circuits interconnecting different segments. Rhythmicity in elevator and depressor motoneurons is not dependent on reciprocal connections between the circuitry driving the motor nuclei. Therefore, separate oscillators for elevators and depressors appear to be present within one spinal segment.
从去脑、麻痹的黄貂鱼中记录有节律的运动神经元活动，并与从同一动物记录的肌电图进行比较。在麻痹前后，背侧（上举肌）和腹侧（下压肌）传出神经之间出现了从吻端到尾端的交替序列。因此，在没有相位传入输入的情况下观察到了游泳模式，这构成了虚拟运动。麻痹后，节段间延迟（在逐渐靠尾端的记录部位激活之间的时间）和爆发持续时间与游泳周期时长仍呈线性关系。在许多情况下，固定化对斜率和截距均无显著改变。截距都落在原点附近，表明虚拟节律保持恒定的相位耦合。尽管游泳节律是在麻痹后获得的，但仍出现了一些差异。这些差异包括自发序列更少、更短，周期时长范围更大，以及爆发持续时间更长。在虚拟游泳期间，爆发持续时间与周期时长的比值通常从麻痹前观察到的0.39增加到0.53。因此，在运动期间拮抗肌传出神经爆发放电之间出现的静息期在麻痹后常常不存在。对尾巴进行机械刺激会缩短周期时长和爆发持续时间；然而，爆发与周期的比值仍大于或等于0.50。尾巴刺激并未改变自发序列中爆发持续时间与周期时长之间的线性关系。在虚拟游泳期间，黄貂鱼游泳所特有的节段间和节段内耦合变得不稳定。在长游泳周期的序列中，异常耦合更常出现。在任何周期时长下，节段内耦合都比节段间耦合更紧密。一个节段水平的节律性活动可以独立于其他水平的活动。这表明存在多个振荡器电路，它们不依赖于连接不同节段的脊髓固有电路。上举肌和下压肌运动神经元的节律性不依赖于驱动运动核的电路之间的相互连接。因此，在一个脊髓节段内似乎存在上举肌和下压肌的独立振荡器。
