Behavior of neurons in the abducens nucleus of the alert cat--II. Internuclear neurons.

摘要: The activity of 43 antidromically identified abducens internuclear neurons with conduction velocities ranging from 14 to 54 m/s was analyzed in alert cats during spontaneous and vestibular induced eye movements. discharge rate significantly increased successive adducting positions the contralateral eye. Slopes rate-position (k) relationships ranged 3.1 17.9 spikes/deg (mean 12.01 ± 3.1). Threshold −19° +3°. Frequency saturation never observed for any neuron within oculomotor range. Although straight lines were selected illustrate relationships, exponential curves always provided best statistical fit demonstrating that an enhancement frequency potentiation must accompany more eccentric fixations on direction. Internuclear showed a low variability firing (<3.0%) less than 1 s. Variability both longer repeated same position. Discharge rates found depend upon direction preceding movement animal's level alertness. Separate regression relations following saccades off directions differed slope (100%), but not threshold. static hysteresis non-motoneuron shows this property be central neural circuit prior extraocular motoneuron. slopes plots all decreased (100%) when alertness changed “alert” (1 0.2saccades/s) “drowsy” (0.5 0.2saccades/s). Thresholds, however, altered. Discharge abruptly 10.4 2.5 ms direction, 20.5 7.8ms before direction. Internuclear neuronal affected by pure vertical saccades. During saccades, did saturate, velocity linear fashion. Exponential functions often data better due difference rate-velocity vs (rs) 0.99 4.10 spikes/s/deg/s 2.16 0.93). decreased, it seldom ceased. Rate-velocity measured fast phase nystagmus (rsv = 2.09 0.88) no significant differences rs 82% cases. However, rsv values different slow (rv 2.52 1.1) six out 10 neurons. intraburst continuously changing profile similar described motoneurons cat monkey. Exponential-like changes near end saccades. Compared motoneurons, irregular rate, higher k r (1.4 1.9 times, respectively), lower thresholds recruitment at given Given increases r, time constants (Ts rs/k) also 1.4 times motoneurons. All parameters predictably modified exhibited directional hysteresis. Discharge correlated vergence movements 5/13 monocular eye, responded those conjugate movement. There was, response ipsilateral These suggest synaptic organization between medial rectus gaze. Sinusoidal rotation dark Hz produced lead instantaneous envelope respect position orbit 42.6. constant (T0) calculated transfer function 152.9 43.1 ms. This value individual Ts rs/k (174.9 66.6), Tsv rsv/k (169.1 63.4) Tv rv/k (201.2 67.0) quotients; (143.1 35.1). Every participated horizontal movements, except vergence. relationship 0.3 findings argue distribution cell sizes may ordered alike populations. By contrast, relation coefficient suggests neurons, as pool, are excitable which correlates well their roles