Biomedical subjects

D G Fishel

Publications and source records attributed to D G Fishel.

3 recordsLinked to original sources

PubMed1995

Head-shake vestibulo-ocular reflex testing: comparison of results with rotational chair testing.

The currently accepted "gold standard" for rotational testing of the vestibulo-ocular reflex uses a servo-controlled chair for sinusoidal whole-body rotation. Previous work in our laboratory has shown good concordance between conventional rotational chair testing and head-on-body (or "head-shake") testing for gain and phase values of the vestibulo-ocular reflex as recorded and analyzed on our rotational chair system's software. In this article we describe results obtained from 10 normal subjects and 20 patients with reduced caloric responses using a portable system being developed in our laboratory that allows an examiner to generate both whole-body and head-on-body rotational stimuli. Test frequencies within the range 0.25 to 1.0 Hz were chosen for comparison with results obtained by conventional rotational chair testing. Visual conditions for all tests included both visually enhanced vestibulo-ocular reflex (real earth-fixed target) and mentally enhanced vestibulo-ocular reflex (imagined earth-fixed target, in darkness or with vision obscured) paradigms. Our results show general agreement between head-shake and rotational chair testing and both manual whole-body rotation and head-shake testing on our portable system for vestibulo-ocular reflex gain and phase testing, with the largest differences noted at 1.0 Hz. Portable rotational testing was well tolerated by young and elderly subjects alike. We expect manual whole-body rotation and head-shake testing will be useful adjuncts for examining vestibulo-ocular reflex function when more formal rotational chair testing is not possible.

Adult↗

PubMed1995

Estrogen replacement therapy and postural stability in the elderly.

Postural instability and falls in the elderly patient constitute a major health care problem. The etiology is often multifactorial, involving abnormal sensory input (visual, vestibular, and somatosensory), poor central processing, and suboptimal musculoskeletal biomechanics. Estrogen replacement therapy has been shown to prevent Alzheimer's disease and to improve cognitive performance in women with dementia. It was, therefore, postulated that estrogen replacement may improve central processing speed, which would result in improved postural stability. In this prospective, randomized, double-blinded study, 87 elderly female subjects (age > 69) were examined by repeated dynamic platform posturography, to measure the effect of estrogen therapy versus placebo upon postural stability. Results indicate that those receiving estrogen had no significant improvement in postural stability at 2 and 8 months of treatment relative to those receiving placebo. Trail Making B test was used as the psychometric test of central processing speed. There was no significant effect of estrogen on this measure over the 8 months of observations. It is concluded that 8 months of estrogen replacement therapy has no significant effect on central processing speed or postural stability in a healthy older female population.

Aged↗

PubMedDate not supplied

Age-related modulation of the vestibulo-ocular reflex using real and imaginary targets.

In this study, we examined age-related effects upon modulation of the VOR with visual and imaginary targets during sinusoidal harmonic acceleration. Eight young (< 30 years) and 5 elderly (> 65 years) subjects were tested using sinusoidal whole-body rotation at 0.025 Hz, 0.1 Hz, and 0.5 Hz. Peak velocity for all trials was 50 degrees/s. Mean VOR gain and phase were calculated under the following paradigms: mental tasking (in darkness), visual enhancement (earth-fixed visual target), visual suppression (chair-fixed visual target), mental enhancement (earth-fixed imaginary target), and mental suppression (chair-fixed imaginary target). Test results from VOR trials in darkness with mental tasking were used as a reference for comparing results obtained from the various paradigms. Our results indicate significant changes in VOR gain for both age groups compared to VOR with mental tasking for the visually enhanced, visually suppressed, and mentally suppressed paradigms at all three frequencies. Neither group showed significant enhancement of VOR gain with an earth-fixed imaginary target at any frequency. Both groups were nearly equal in their abilities to enhance and suppress VOR gain under the visual paradigms. Younger subjects showed a significantly greater degree of gain suppression at 0.5 Hz than the older group for the mental suppression paradigm. VOR phase tended toward zero during the visual paradigms for both groups at all frequencies. For the mental imagery paradigms, VOR phase resembled values for VOR with mental tasking in the younger group at all three frequencies and in the older group at all but 0.1 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗