We determined whether head position with regard to gravity is an important context for angular vestibuloocular reflex (aVOR) gain adaptation. Vertical aVOR gains were adapted with monkeys upright or on side by rotating the animals about an interaural axis in phase or out of phase with the visual surround for 4 h. When aVOR gains were adapted with monkeys upright, gain changes were symmetrical w...

Irregular vestibular afferents exhibit significant phase leads with respect to angular velocity of the head in space. This characteristic and their connectivity with vestibulospinal neurons suggest a functionally important role for these afferents in producing the vestibulo-collic reflex (VCR). A goal of these experiments was to test this hypothesis with the use of weak galvanic stimulation of ...

[Purpose] We investigated the effect of rhythmic ankle movement on the contralateral soleus H-reflex. The H-reflex was evoked from the right soleus muscle. [Subjects and Methods] Healthy humans rhythmically moved the left ankle (movement condition) or held the left ankle stationary (stationary condition) at one of three positions corresponding to the ankle positions at which the H-reflex was ev...

The present study examined the effects of sustained anticipatory anxiety on the affective modulation of the eyeblink startle reflex. Towards this end, pleasant, neutral and unpleasant pictures were presented as a continuous stream during alternating threat-of-shock and safety periods, which were cued by colored picture frames. Orbicularis-EMG to auditory startle probes and electrodermal activit...

Electrophysiological recordings of the H-reflex and nonnociceptive flexion reflex were obtained from pentobarbital-anesthetized Intact rats and from both, anesthetized and unanesthetized groups of Acute and Chronic Spinal rats. Results showed that the flexor, but not H-reflex, of Chronic Spinal rats was significantly larger than that of all other groups, which did not differ among themselves. T...

The potentiation of H-reflexes during effort has been studied in 16 patients with mild hemiparesis. Impaired potentiation was present in all but one patient, and was still evident in some who had recovered fully from weakness. A tentative explanation has been proposed for these findings; it is suggested that there is loss of a background facilitatory pathway to motoneurones.

BACKGROUND Possible utility of high-dose i.v. melatonin as an anaesthetic adjuvant has not been studied. This study compared its effects with thiopental and propofol. METHODS Sprague Dawley rats were assigned to receive bolus or cumulative i.v. doses of melatonin, thiopental or propofol. Righting reflex, hindpaw withdrawal to a noxious stimulus, response to tail clamping and haemodynamic effe...

H-reflex down-conditioning increases GABAergic terminals on spinal cord motoneurons. To explore the origins of these terminals, we studied the numbers and distributions of spinal cord GABAergic interneurons. The number of identifiable GABAergic interneurons in the ventral horn was 78% greater in rats in which down-conditioning was successful than in naive rats or rats in which down-conditioning...

The amplitude of the H-reflex declines when activated repetitively. The magnitude of decline is greater when the amplitude of the H-reflex is small. To explore whether pre- or postsynaptic factors contribute to the differences observed in H-reflexes of different sizes, changes in the amplitude of H-reflexes of different sizes were measured during a train of stimulation in 10 normal subjects. Am...

The excitability of the monosynaptic reflex pathway was tested in infants and children from birth to four years of age during waking and sleeping. The H reflex, evoked in the soleus muscle, was used to calculate the ratio, maximal H to maximal M, construct recruitment curves and test reflex excitability by the paired stimulus method. The excitability of the monosynaptic reflex pathway during th...