Biomedical subjects

S M Woolley

Publications and source records attributed to S M Woolley.

10 recordsLinked to original sources

PubMed2001

Hair cell regeneration and recovery of auditory thresholds following aminoglycoside ototoxicity in Bengalese finches.

Birds regenerate auditory hair cells when original hair cells are lost. Regenerated hair cells become innervated and restore hearing function. Functional recovery during hair cell regeneration is particularly interesting in animals that depend on hearing for vocal communication. Bengalese finches are songbirds that depend on auditory feedback for normal song learning and maintenance. We examined the structural and functional recovery of the Bengalese finch basilar papilla after aminoglycoside ototoxicity. Birds were treated with the ototoxic aminoglycoside, amikacin, daily for 1 week. Treatment resulted in hair cell loss across the basal half of the basilar papilla and corresponding high frequency hearing loss. Hair cell regeneration and recovery of auditory brainstem responses were compared in the same animals. Survival times following treatment were between 1 day and 12 weeks. Analysis of structural recovery at weekly intervals indicated that hair cells in the Bengalese finch papilla require a maximum of 1 week to regenerate and appear with immature morphology at the epithelial surface. An additional 6 days are required for adult-like morphology to develop. Repopulation of the damaged region was complete by 8 weeks. Recovery of auditory thresholds began 1 week after treatment and reached asymptote by 4 weeks. Slight residual threshold shifts at 2.0 kHz and above were observed up to 12 weeks after treatment. Direct comparison of structural and functional recovery indicates that auditory thresholds recover maximally before a full complement of hair cells has regenerated.

Amikacin↗

PubMed1999

High-frequency auditory feedback is not required for adult song maintenance in Bengalese finches.

Male Bengalese finches do not normally change their vocal patterns in adulthood; song is stereotyped and stable over time. Adult song maintenance requires auditory feedback. If adults are deafened, song will degrade within 1 week. We tested whether feedback of all sound frequencies is required for song maintenance. The avian basilar papilla is tonotopically organized; hair cells in the basal region encode high frequencies, and low frequencies are encoded in progressively apical regions. We restricted the spectral range of feedback available to a bird by killing either auditory hair cells encoding higher frequencies or those encoding both high and low frequencies and documented resultant changes in song. Birds were treated with either Amikacin alone to kill high-frequency hair cells or Amikacin and sound exposure to target hair cells across the entire papilla. During treatment, song was recorded from all birds weekly. After treatment and song recording, evoked-potential audiograms were evaluated on each bird, and papillas were evaluated by scanning electron microscopy. Results showed that hair cell damage over 46-63% of the basal papilla and the corresponding high-frequency hearing loss had no effect on song structure. In birds with hair cell damage extending further into the apical region of the papilla and corresponding low-frequency and high-frequency hearing loss, song degradation occurred within 1 week of beginning treatment and was comparable with degradation after surgical deafening. We conclude that either low-frequency spectral cues or temporal cues via feedback of the song amplitude envelope are sufficient for song maintenance in adult Bengalese finches.

Amikacin↗

PubMed1997

Bengalese finches Lonchura Striata domestica depend upon auditory feedback for the maintenance of adult song.

Male birds of age-limited song-learning species develop their full song repertoires in the first year of life. For this type of song learner, once song is stabilized in adulthood, it is highly stereotyped and stable over time. Traditionally, it has been believed that age-limited song learners do not depend on auditory feedback for the maintenance of adult song. A recent report, however, showed that adult song in zebra finches, age-limited learners, does change after long-term deafness. We report here that another species of age-limited learner, Bengalese finches, depends critically on auditory feedback for adult song maintenance. We surgically deafened adult males and recorded song for 12 weeks after surgery. Results show that song degraded significantly within 1 week of surgery and continued to degrade over the next 11 weeks. This represents a more rapid degradation of song than has been seen previously in age-limited species. Song deficits after deafening included a marked decrease in syllable sequence stereotypy, skewed syllable distribution within song bouts, degradation of syllable phonology, and dropped, combined, and new or unrecognizable syllables. Decreased sequence stereotypy and combined syllables appeared within 1 week of deafening and did not worsen over time. Skewed syllable distributions and syllable phonology changes appeared after 1 week and did worsen. Occurrences of dropped and new syllables appeared within 1 week and increased over time. Comparison with other species indicates that much variability exists among species in the extent to which auditory feedback is necessary for song maintenance.

Acoustic Stimulation↗

PubMed1997

An assessment of falls in elderly men and women.

BACKGROUND: The assessment of falls in the elderly has moved from disease-oriented approaches, which attempt to identify single causative factors, to performance-oriented evaluations of functional deficits. This study examined the abilities of elderly fallers and nonfallers to perform various functional activities and to provide some rationale for performance differences by assessing the integrity of specific systems within the sensory, central processing control, and effector components of balance control. METHODS: Twenty-two elderly subjects, aged 69-93 years, categorized as either a faller or a nonfaller, were assessed on their ability to perform the functional activities of static balance, walking, and stair descent. In addition, the balance control components of sensory input: vision, vestibular function, and proprioception; the central processing control system components: mental status, selective attention, perceptual style, and simple and choice reaction time; and the effector system: isometric strength were assessed. RESULTS: The data indicated that fallers exhibited significantly reduced static balance, walking and stair descent performance than the nonfallers. The fallers exhibited significantly lower selective attention abilities and increased choice resisted reaction times, both measures of the central processing control system component. The nonfallers exhibited reduced proprioceptive function, suggesting that this is not a major contributor to the performance of balance and mobility skills. CONCLUSIONS: The data suggest that actual performance of mobility skills is an efficient means of identifying potential fallers. The decrements in functional activity performance appear to be related to central information processing control components, specifically selective attention and choice reaction time. The significant correlations between the sensory input, central processing control, and effector components with the functional activities suggest that the marginal declines in the sensory and effector components may have an additive effect, which may adversely affect the ability of fallers to perform the functional activities. The data suggest that selective attention and choice reaction time are the two most significant balance control components predictive of falls.

Accidental Falls↗

PubMed1995

Visually-controlled leg movements embedded in a walking task.

Accurate control of alternating leg movements in walking was considered as a visually controlled target aiming task. Nine subjects aimed alternate feet at targets along a walkway, using nine combinations of amplitude and target width giving index of difficulty values between 2.59 and 6.16. Movement time was compared to the same subjects performing reciprocal tapping tasks with arm and leg. Alternating target aiming tasks were the most rapid of all tasks studied. Explanations of this effect in terms of learning and elimination of direction changes were consistent with the data from all conditions. Visual control can be expected in normal walking only for target sizes smaller than about 300 mm, i.e., under unusual accuracy requirements.

Adult↗

PubMed1995

Postural stability following mild head or whiplash injuries.

Studies of the sequelae of head injury suggest that cochlear and vestibular dysfunctions, comprise some of the most frequently reported delayed complications following head trauma. To date, little attention has been given to the relation between post-traumatic subjective symptoms of dizziness and the objective measures of postural stability or balance. The purpose of this study was to quantify the balance deficits in individuals who had developed symptoms of dizziness following mild head and whiplash injuries. The balance abilities of 29 patients, who developed dizziness following some type of mild head or whiplash injury, were compared to those of 51 healthy symptom-free subjects. Balance was assessed by examining the center-of-pressure movements, in the anterior-posterior and medial-lateral directions, and the total movement displacement. The isolated contributions of visual and somatosensory inputs were estimated by comparing the magnitudes of the center-of-pressure movements for the various sensory conditions. Data were collected from three 30-second trials of each combination of three visual conditions (accurate, absent, and inaccurate) and two somatosensory conditions (accurate and inaccurate), with the patient standing on a fixed-force platform. Univariate analyses of variance indicated that the group with head injury, compared to the control group, exhibited significantly greater anterior-posterior movements in four of the six sensory conditions and greater total movement displacement during the inaccurate vision/inaccurate somatosensation condition. These data suggest that patients who have sustained head or neck trauma exhibit increased reliance on accurate visual input and are unable to utilize vestibular orienting information to resolve conflicting information from the visual and somatosensory systems.

Adolescent↗

PubMed1994

Static stabilometry, transcranial Doppler, and single photon emission computed tomography in patients with central dizziness.

Previous studies have found that transcranial doppler (TCD) and single photon emission computed tomography (SPECT) are effective means of diagnosing cerebral blood flow disorders in patients with central dizziness whose etiology was unknown by standard audiologic and/or vestibular assessment techniques. Also, static stabilometry, which measures a person's standing center of pressure (COP) movements, has been used to distinguish between patients with central neurologic and peripheral vestibular disorders. The purpose of this retrospective study was to examine the relation between TCD, SPECT, and stabilometry in patients with central dizziness attributable to cerebral blood flow disorders. Stabilometry testing was conducted on 50 normal subjects and 31 subjects with dizziness, the latter group consisting of persons with cerebral dysautoregulation, migraines, and unknown etiology with negative or positive SPECT results. The results indicated that patients with cerebral dysautoregulation were not significantly different from normal subjects or the other three groups in their COP movements. The other three groups exhibited significantly higher COP movements than the normal subjects, particularly when visual inputs were compromised. Patients with negative SPECT results were significantly different in their COP movements from the other three groups of subjects with dizziness. These results suggest that the pattern of COP movements may be useful in identifying patients with postural dysfunctions whose etiology may then be detected by TCD and SPECT.

Adult↗

PubMed1993

Differentiation of balance deficits through examination of selected components of static stabilometry.

Stabilometry, which measures the body's center of pressure (COP) movements, during relaxed standing, has been used to distinguish individuals with vestibular and neurologic dysfunctions from normal subjects. The purpose of this study was to determine whether mathematical differences in the magnitudes of the COP obtained from six somatosensory testing conditions could be used to discriminate between different types of balance deficits. Stabilometry measures, using a fixed force platform, were obtained from normal (N = 52) and dizzy (N = 149), peripheral vestibular dysfunction (PVD), post-concussion syndrome (PCS), psychogenic (PSG), and unknown/undetermined etiology (UNK). The data significantly differentiated CVD, PVD and PSG patients from normals and between some of the dizzy groups: CVD versus PVD, PCS; and PSG versus CVD, PVD, PCS and UNK. The measures of anterior-posterior COP movements provided the greatest discrimination.

Adolescent↗

PubMedDate not supplied

Progenitor cell cycling during hair cell regeneration in the vestibular and auditory epithelia of the chick.

We investigated nucleotide-labeling patterns during ongoing hair cell regeneration in the avian vestibular epithelium and during drug-induced regeneration in the avian auditory epithelium. For utricle experiments, post-hatch chicks received an injection of bromodeoxyuridine (BrdU) and were allowed to survive from 2 hours to 110 days after the injection. Utricles were fixed and immunoreacted to detect BrdU. The number of BrdU-labeled nuclei in the hair cell and support cell layers of the utricular sensory epithelium changes significantly between 2 hours and 110 days post-BrdU. At 2 hours, most labeled cells are isolated, while by 5-10 days, the majority of labeled cells are organized in pairs that are most frequently composed of a hair cell and a support cell. Pairs of labeled cells are seen as late as 110 days. Clusters of more than 3 labeled cells are uncommon at all time-points. The total number of labeled cells increases approximately 1.5-fold between 5 and 60 days post-BrdU. This increase is due primarily to a rise in the number of labeled support cells, and it is likely that it represents additional rounds of division by a subset of cells that were labeled at the time of the BrdU injection. There is a significant decrease in labeled nuclei in the hair cell layer between 60 and 110 days post-BrdU, suggesting that hair cells die during this period. To investigate support cell recycling in the drug-damaged auditory epithelium, we examined nucleotide double labeling after separate injections of BrdU and tritiated thymidine. A small number of support cells that incorporate BrdU administered at 3 days post-gentamicin treatment also label with tritiated thymidine administered between 17 and 38 hours later. We conclude that a small population of support cells recycles during regeneration in both the normal utricle and the drug-damaged basilar papilla.

Animals↗

PubMedDate not supplied

The effect of hyperbaric oxygen treatment on postural stability and gait of a brain injured patient: single case study.

Hyperbaric oxygen (HBO) therapy has been found to reduce intracranial and cerebrospinal fluid pressures, and increase grey matter metabolic activity in patients with brain injuries. To date, few studies have quantitatively assessed the changes in the patient's functional outcomes following this expensive therapeutic intervention. The purpose of this case study was to examine the immediate and longer term changes in postural stability and gait in a 17 year old patient who sustained a traumatic brain injury, following administration of hyperbaric oxygen (HBO) therapy combined with physical and occupational therapy. The patient underwent assessments of postural stability and gait 1 week prior to HBO therapy, immediately following, and 6 weeks after completion of HBO therapy. Some improvements in postural stability were observed immediately following HBO, although these improvements were not evident 6 weeks later. Only slight improvements were noted in his walking abilities immediately following the intervention, with essentially little change evident 6 weeks later. The results of this do not support anecdotal evidence that there were substantial improvements in the subject's postural stability and gait following HBO therapy.

Adolescent↗