Journal of neurophysiology
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1. The modulation of the short-latency stretch reflex during walking at different walking speeds was investigated and compared with the stretch reflex during standing in healthy human subjects. 2. Ankle joint stretches were applied by a system able to rotate the human ankle joint during treadmill walking in any phase of the step cycle. ⋯ During the stance phase the maximal EMG stretch reflex had a phase lead of approximately 120 ms with respect to the maximal background EMG and a phase lead of approximately 250 ms with respect to the maximal nonreflex torque. 7. The constant latency of the stretch reflex during a step implied that the ankle extensor muscle spindles are always taut during walking. 8. The relatively high amplitude of the stretch reflex in late swing and at heel contact made it likely that the stretch reflex contributed to the activation of the ankle extensor muscles in early stance phase.
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1. Membrane currents of hair cells in acutely excised or cultured mouse utricles were recorded with the whole cell voltage-clamp method at temperatures between 23 and 36 degrees C. 2. Type I and II hair cells both had delayed rectifier conductances that activated positive to -55 mV. 3. ⋯ Warming the cells to 36 degrees C produced parallel shifts in gK,L's activation range (0.8 +/- 0.3 mV/degrees C, n = 8), and in the resting potential (0.6 +/- 0.3 mV/degrees C, n = 4). Thus the high input conductances were not an artifact of unphysiological temperatures but remained high near body temperature. It remains possible that in vivo gK,L's activation range is less negative and input conductances are lower; the large variance in the voltage range of activation suggests that it may be subject to modulation.
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Comparative Study Clinical Trial Controlled Clinical Trial
Comparison of human cerebral activation pattern during cutaneous warmth, heat pain, and deep cold pain.
1. We wished to determine whether there are differences in the spatial pattern and intensity of synaptic activity within the conscious human forebrain when different forms and intensities of innocuous and noxious thermal stimuli are experienced. Accordingly, positron emission tomography (PET) with intravenous injection of H2(15)O was used to detect increases in regional cerebral blood flow (rCBF) in normal humans as they discriminated differences in the intensity of noxious and innocuous thermal stimulation applied to the nondominant (left) arm. ⋯ For discrimination between tonic innocuous cold and tonic cold pain, the left hand was immersed to the wrist, throughout each of six scans, in water kept at an average temperature of either 20.5 +/- 1.15 degrees C (mean +/- SD) or 6.02 +/- 1.18 degrees C (mean +/- SD) on alternate scans. All subjects rated the intensity of the stimuli on a scale in which 0 indicated no pain and 10 represented barely tolerable pain. Subjects rated the 20 degrees C water immersion as painless (average rating 0.18 +/- 0.48, mean +/- SD), but gave ratings indicating i
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Randomized Controlled Trial Clinical Trial
Human express saccade makers are impaired at suppressing visually evoked saccades.
1. We report the oculomotor behavior of human subjects who produce unusually high numbers (> 30%) of express saccades (latency range 85-135 ms) in the overlap saccade task, where express saccades are usually absent or small in number (< 15%). We refer to these subjects as "express saccade makers" (ES makers). 2. ⋯ The collicular fixation neurons are probably the final common pathway in the control of active fixation, and are in mutual inhibitory relationship with the saccade cells. 6. The decreased saccadic control observed in the ES makers suggests that saccade execution in humans is also gated by a fixation system. These ES makers may have reduced voluntarily control over saccade generation as a result of a defect or poor development of their fixation system.
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1. We studied seven subjects with cerebellar lesions and seven control subjects as they made reaching movements in the sagittal plane to a target directly in front of them. Reaches were made under three different conditions: 1) "slow-accurate," 2) "fast-accurate," and 3) "fast as possible." All subjects were videotaped moving in a sagittal plane with markers on the index finger, wrist, elbow, and shoulder. ⋯ Because of this, interaction torques often determined the pattern of incoordination of the elbow and shoulder that produced the curved trajectory and target overshoot. In the slow-accurate condition, we reason that the cerebellar subjects may use a decomposition strategy so as to simplify the movement and not have to control both joints simultaneously. From these results, we suggest that a major role of the cerebellum is in generating muscle torques at a joint that will predict the interaction torques being generated by other moving joints and compensate for them as they occur.