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Biomedical subjects

Mark S Redfern

Publications and source records attributed to Mark S Redfern.

23 records · Page 2Linked to original sources
PubMed2002

Adaptation of vibration-induced postural sway in individuals with Parkinson's disease.

Postural control requires accurate integration of visual, vestibular, cutaneous, and proprioceptive sensory information. Previous research suggests that patients with Parkinson's disease (PD) may have difficulty with this integration process, particularly involving incongruent visual information. The purpose of this study was to determine whether PD patients also show difficulty in adaptation to erroneous proprioceptive information. Postural reactions to soleus muscle vibration were explored in 8 PD patients, 8 healthy elderly, and 8 young adults. Postural sway was recorded using an electromagnetic motion analysis system in four conditions (2 vision x 2 vibration) with four trials in each condition to test subjects' adaptation to the vibrator stimulus. The results showed that PD patients did adapt to the vibration across trials, similar to those of both control groups. It was concluded that PD patients in the early stages of the disease could override inaccurate proprioceptive inputs, relying more on true vestibular and/or visual information. These results suggest that the basal ganglia are not critical for this adaptation process in postural control.

Adaptation, Physiological↗
PubMed2002

Attentional dynamics in postural control during perturbations in young and older adults.

Temporal dynamics of attention during postural perturbations in young and older adults were investigated. Nineteen young and older subjects performed simple reaction time tasks during translational platform perturbations. Auditory or visual stimuli were presented randomly at delays from the onset of the platform perturbation. Reaction time was slowed before and during the platform movement, particularly in older subjects. Reaction times to stimuli presented at a 250-millisecond delay or later were not influenced by perturbation. The reaction times to the auditory stimuli were influenced more by perturbation than were those to visual targets. The postural response was unaltered by the presence of the reaction time task, but it differed between groups. Attention is engaged in response to a perturbation during the preperturbation time and during the initiation of the postural response in young and older adults. Sensory selection occurs in young and older adults, but to a greater degree in older subjects.

Accidental Falls↗
PubMed2002

Voluntary upper-extremity movements in patients with unilateral peripheral vestibular hypofunction.

BACKGROUND AND PURPOSE: People with peripheral vestibular pathology demonstrate motor impairments when responding and adapting to postural platform perturbations and during performance of sit-to-stand and locomotor tasks. This study investigated the influence of unilateral peripheral vestibular hypofunction on voluntary arm movement. SUBJECTS AND METHODS: Subjects without known neurological impairments and subjects with vestibular impairments performed 3 voluntary arm movements: an overhead reach to a target, a sideward reach to a target, and a forward flexion movement through 90 degrees. Subjects performed these tasks under precued and choice reaction time conditions. During all tasks, body segment motion was measured. Head velocity measurements were calculated for the side task only. RESULTS: Subjects with vestibular loss restricted upper body segment motion within the frontal and transverse planes for the 90-degree and overhead tasks. Average angular head velocity was lower for the group with vestibular hypofunction. Task uncertainty (the introduction of a choice reaction time paradigm) differentially influenced the groups regarding head velocity at target acquisition. DISCUSSION AND CONCLUSION: Individuals with vestibular loss altered their performance of voluntary arm movements. Such alterations may have served to minimize the functional consequences of gaze instability.

Analysis of Variance↗
PubMedDate not supplied

Effects of nortriptyline and paroxetine on postural sway in depressed elderly patients.

Tricyclic antidepressants (TCAs) have previously been found to be related to an increased incidence of falls in elderly persons. Recent pharmacoepidemiologic and nursing home studies have suggested that the risk of falls and fractures in elderly patients receiving selective serotonin reuptake inhibitors (SSRIs) is not different from that of patients receiving TCAs. The authors therefore evaluated postural sway in an older population of depressed patients randomly assigned to treatment with either nortriptyline or paroxetine and did not find any change in postural sway after 6 weeks' treatment with either antidepressant. Further studies with other SSRIs are needed.

Aged↗