Biomedical subjects

Arnold Starr

Publications and source records attributed to Arnold Starr.

8 recordsLinked to original sources

PubMed2005

Event-related potentials accompanying motor preparation and stimulus expectancy in the young, young-old and oldest-old.

Although aging is accompanied by neurobiological changes and increased susceptibility to many neurological disorders, little is known about neurophysiological changes that start in old age. Here, neurophysiological changes during old age were assessed by recording brain potentials associated with motor preparation and stimulus expectancy (contingent negative variation, CNV) in young-old (60-69), oldest-old (85-98), and young (17-23) subjects. Individual trials began by a button press, followed 2.5 s later by either a low or high pitch tone. In the "motor" condition subjects responded following high pitch tones (P=0.20); in the "non-motor" condition subjects did not respond. Motor condition CNV amplitudes in the oldest old were more positive than the young and young-old groups, which were similar. In the non-motor condition, the young-old and oldest-old had similar CNV amplitudes that were positive in polarity, and were significantly different from young subjects. Motor potentials before button presses that started the trials were comparable among groups. Results show that neural activity associated with motor preparation and stimulus expectancy changes during advanced age, and that group differences can be modulated by task requirements.

Acoustic Stimulation↗

PubMed2004

Perceptual consequences of disrupted auditory nerve activity.

Perceptual consequences of disrupted auditory nerve activity were systematically studied in 21 subjects who had been clinically diagnosed with auditory neuropathy (AN), a recently defined disorder characterized by normal outer hair cell function but disrupted auditory nerve function. Neurological and electrophysical evidence suggests that disrupted auditory nerve activity is due to desynchronized or reduced neural activity or both. Psychophysical measures showed that the disrupted neural activity has minimal effects on intensity-related perception, such as loudness discrimination, pitch discrimination at high frequencies, and sound localization using interaural level differences. In contrast, the disrupted neural activity significantly impairs timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, temporal modulation detection, backward and forward masking, signal detection in noise, binaural beats, and sound localization using interaural time differences. These perceptual consequences are the opposite of what is typically observed in cochlear-impaired subjects who have impaired intensity perception but relatively normal temporal processing after taking their impaired intensity perception into account. These differences in perceptual consequences between auditory neuropathy and cochlear damage suggest the use of different neural codes in auditory perception: a suboptimal spike count code for intensity processing, a synchronized spike code for temporal processing, and a duplex code for frequency processing. We also proposed two underlying physiological models based on desynchronized and reduced discharge in the auditory nerve to successfully account for the observed neurological and behavioral data. These methods and measures cannot differentiate between these two AN models, but future studies using electric stimulation of the auditory nerve via a cochlear implant might. These results not only show the unique contribution of neural synchrony to sensory perception but also provide guidance for translational research in terms of better diagnosis and management of human communication disorders.

Acoustic Stimulation↗

PubMed2004

Auditory temporal processes in normal-hearing individuals and in patients with auditory neuropathy.

OBJECTIVE: To study objectively auditory temporal processing in a group of normal hearing subjects and in a group of hearing-impaired individuals with auditory neuropathy (AN) using electrophysiological and psychoacoustic methods. METHODS: Scalp recorded evoked potentials were measured to brief silent intervals (gaps) varying between 2 and 50ms embedded in continuous noise. Latencies and amplitudes of N100 and P200 were measured and analyzed in two conditions: (1) active, when using a button in response to gaps; (2) passive, listening, but not responding. RESULTS: In normal subjects evoked potentials (N100/P200 components) were recorded in response to gaps as short as 5ms in both active and passive conditions. Gap evoked potentials in AN subjects appeared only with prolonged gap durations (10-50ms). There was a close association between gap detection thresholds measured psychoacoustically and electrophysiologically in both normals and in AN subjects. CONCLUSIONS: Auditory cortical potentials can provide objective measures of auditory temporal processes. SIGNIFICANCE: The combination of electrophysiological and psychoacoustic methods converged to provide useful objective measures for studying auditory cortical temporal processing in normals and hearing-impaired individuals. The procedure used may also provide objective measures of temporal processing for evaluating special populations such as children who may not be able to provide subjective responses.

Acoustic Stimulation↗

PubMed2004

A dominantly inherited progressive deafness affecting distal auditory nerve and hair cells.

We have studied 72 members belonging to a large kindred with a hearing disorder inherited in an autosomal dominant pattern. We used audiological, physiological, and psychoacoustic measures to characterize the hearing disorders. The initial phenotypic features of the hearing loss are of an auditory neuropathy (AN) with abnormal auditory nerve and brainstem responses (ABRs) and normal outer hair cell functions [otoacoustic emissions (OAEs) and cochlear microphonics (CMs)]. Psychoacoustic studies revealed profound abnormalities of auditory temporal processes (gap detection, amplitude modulation detection, speech discrimination) and frequency processes (difference limens) beyond that seen in hearing impairment accompanying cochlear sensory disorders. The hearing loss progresses over 10-20 years to also involve outer hair cells, producing a profound sensorineural hearing loss with absent ABRs and OAEs. Affected family members do not have evidence of other cranial or peripheral neuropathies. There was a marked improvement of auditory functions in three affected family members studied after cochlear implantation with return of electrically evoked auditory brainstem responses (EABRs), auditory temporal processes, and speech recognition. These findings are compatible with a distal auditory nerve disorder affecting one or all of the components in the auditory periphery including terminal auditory nerve dendrites, inner hair cells, and the synapses between inner hair cells and auditory nerve. There is relative sparing of auditory ganglion cells and their axons.

Acoustic Impedance Tests↗

PubMed2004

Age-related differences in auditory event-related potentials during a cued attention task.

OBJECTIVE: To determine if aging is associated with differences in attentional regulation using behavioral and event-related potential (ERP) measures. METHODS: Younger (n=13;M=20 years) and older (n=12;M=76 years) subjects performed an auditory cued attention task. Verbal cues correctly (valid) or incorrectly (invalid) predicted the ear receiving a target tone 1.5 s later, or were uninformative (neutral). Targets were either 'high' (2000 Hz) or 'low' (1000 Hz) pitch monaural tones. Subjects pressed one of 4 buttons to indicate target ear and pitch. ERPs following cues and targets (P50, N100, P200, slow waves), and negative slow potentials (CNV) between cues and targets were assessed. RESULTS: Cue information had significant effects on reaction time for both groups (valid valid) but not older subjects. Target slow waves were also affected by cue information (invalid>valid), and the difference was larger and lasted longer in older subjects. Slow waves following cues were significantly larger in older subjects, but the subsequent CNV amplitudes were comparable among groups. CONCLUSIONS: When performing a cued attention task, age differences are present in transient ERPs following cues and targets. SIGNIFICANCE: Age differences in ERPs associated with attentional regulation support the hypothesis that attentional changes contribute to cognitive aging.

Acoustic Stimulation↗

PubMed2004

Visual encoding differentially affects auditory event-related potentials during working memory retrieval.

Previous working memory studies using auditory stimuli at both encoding and retrieval show amplitude decreases in event-related potentials (N100 and late positive wave, LPW) at retrieval as a function of memory load. This study tested if these effects are associated with phonological or semantic coding by presenting visual stimuli at encoding and auditory stimuli at retrieval. We hypothesized that event-related potentials associated with phonological but not semantic coding would be affected by modality differences at encoding and retrieval. Memory sets having one, three, or five visual digits were followed by auditory probes that subjects classified as present or absent from the set. Reaction time increased and LPW amplitudes decreased with increases in memory load, but there were no significant effects of memory load on N100 amplitude. Results suggest that with respect to brain activity that covaries with memory load, probe N100 amplitude is associated with phonological coding and LPW amplitude is associated with semantic coding.

Acoustic Stimulation↗

PubMed2003

Pathology and physiology of auditory neuropathy with a novel mutation in the MPZ gene (Tyr145->Ser).

We studied a family with hereditary sensory motor neuropathy and deafness accompanying a missense mutation in the MPZ gene. Pathological examination of the cochlea in one of the family members revealed marked loss of auditory ganglion cells and central and peripheral auditory nerve fibres within the cochlea. The inner hair cells were of normal number with preserved morphology. The outer hair cells were normal in number except for a 30% reduction in just the apical turn. Examination of the sural nerve and the auditory nerve adjacent to the brainstem showed marked loss of fibres with evidence of incomplete remyelination of some of the remaining fibres. Studies of auditory function in surviving family members using electrophysiological and psychoacoustic methods provided evidence that the hearing deficits in this form of auditory neuropathy were probably related to a decrease of auditory nerve input accompanying axonal disease. Altered synchrony of discharge of the remaining fibres was a possible additional contributing factor.

Aged↗

PubMedDate not supplied

Serial position effects in auditory event-related potentials during working memory retrieval.

It is established that recall of an item from a list of sequentially presented items is sensitive to the item's position in the memorized list. However, little is known about the brain mechanisms that mediate these serial position effects. Studies of working memory retrieval using event-related potentials report amplitude reductions during retrieval (auditory cortical N100, neocortical late positive wave [LPW]) as memory load increases. We tested the hypothesis that N100 and LPW amplitudes to probes are also affected by serial position. Event-related potentials were recorded from subjects performing an auditory working memory task. A set of one or five digits was memorized, then subjects classified a probe digit as either present or absent from the memory set. A control task was also given. Amplitudes of the N100 and LPW were reduced in the 5-item versus the 1-item set. In the 5-item set N100 amplitude was significantly larger for the initial (1st) serial position, relative to Positions 2-5, while linear increases in LPW amplitude were seen across serial positions (5th > 1st position). A control task without memorization showed no N100 or LPW amplitude changes with set size or serial position. The findings reveal that the N100 and LPW are influenced differently by serial position during working memory retrieval: N100 shows a primacy effect and LPW demonstrates a recency effect. The results suggest that primacy and recency effects may be mediated by different brain regions at different times during memory retrieval.

Adult↗