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Biomedical subjects

H J Greenberg

Publications and source records attributed to H J Greenberg.

At least 19 recordsLinked to original sources
PubMed1984

The P3 potential and its clinical usefulness in the objective classification of dementia.

Two groups of normal subjects and three groups of demented subjects of specific etiology and severity (mild and moderate arteriosclerotic; moderate Alzheimer's) were compared on the basis of P3 latency and amplitude. P3 latency was found to be a useful parameter for the demonstration of cognitive dysfunction in patients with dementia, which supports the findings of Goodin et al. (1978). Clinically, the efficacy of using P3 latency as an objective test in determining the severity of dementia, can be questioned by two results of this study. First, P3 latency could not separate mildly demented patients from normals. Second, no significant difference was found for counts to the infrequent stimulus between the normal subjects, neurologically-impaired patients and patients with mildly arteriosclerotic dementia. However, P3 latency did enable separation of patients with a moderate classification of dementia from normal subjects. More importantly, P3 latency separated patients with mild and moderate arteriosclerotic dementia. This result indicated that P3 latency was sensitive enough to separate patients with dementia of the same etiology at different stages of the disease.

Aged↗
PubMed1984

Effect of psychophysical backward masking on human brain-stem responses (ABR).

A backward-masking (BWM) paradigm was used to obtain measurements on 4 normal young adults of psychophysical BWM and of the analogous electrophysiological masking from human auditory brain-stem responses. The same stimuli and Ss were used in both experiments. Psychophysical BWM was determined to a 100-musec click masked by a 100-msec white noise after time delays of 1, 5, 10, 25, and 100 msec and at noise masker levels of 50, 65, and 80 db SPL. As previously demonstrated, more psychophysical BWM occurs at short delta ts (1 to 10 msec) than at longer delays and masked thresholds are greater as masker level increases. In the electrophysiological experiment, using delta ts = 1, 5, and 10 msec, the extent to which wave V latency was affected by the following masker was determined for various experimental conditions. Wave V latency increased with a decrease in delta t, for maskers above probe level, except that latency was not significantly affected by any masker level at delta t = 10 msec.

Acoustic Stimulation↗
PubMed1981

Slow brain stem responses (SN10) to tone pips in normally hearing newborns and adults.

The recently discovered slow negative brain stem response at 10 ms (SN10) was investigated as a tool for assessment of hearing in 20 newborns and 20 adults. Tone pips of 500, 1 000 and 2 000 Hz and a click were presented at 60, 40 and 20 dB re normal hearing level. The SN10 response varied systematically as a function of frequency and intensity. SN10 was not observed for all stimuli, but percentages of detection improved as frequency and intensity increased. Newborns demonstrated significantly longer latencies than adults for all stimuli. The results suggest that SN10 is a reliable indicator of peripheral hearing for frequencies of 1 000 Hz and higher.

Adult↗
PubMed1981

Low-level acoustic reflex thresholds.

The acoustic reflex threshold can be detected at lower than normal sound pressure levels by means of facilitation. This procedure entails simultaneous presentation of a high-frequency facilitating tone at a level just below reflex threshold and a second reflex-eliciting tone. The second tone is reduced in intensity until no further reflex activity is observed. When hearing was normal, less signal intensity was needed to elicit the acoustic reflex when facilitation was used. There was a greater amount of reflex threshold improvement when the facilitating and eliciting tones were presented monotically. Sensorineural hearing loss allowed small or no reflex threshold change with facilitation.

Acoustic Stimulation↗
PubMed1981

Predicting hearing loss from the acoustic reflex.

An alternative procedure for predicting hearing threshold level (HTL) from the acoustic reflex threshold (ART) was explored. The ART was measured with an otoadmittance meter using pure tones (.5, 1, 2, or 4 kc/s) or noise-band (.1-1.6; 1.8-6; .1-6 kc/s) reflex-eliciting signals, on 75 normal Ss and 83 Ss with mild-to-severe sensorineural hearing loss. The largest positive linear relationship (R = .83) was found between the pure-tone average HTL at .5, 1, 2, and 4 kc/s vs the ART using the high-pass noise (1.8-6 kc/s) combined with the ART to .5 kc/s. Regression equations were developed to predict the 4-frequency PTA and other indexes of hearing sensitivity from these ARTs.

Adolescent↗
PubMed1979

Effects of ethyl alcohol on the contralateral and ipsilateral acoustic reflex threshold.

Contralateral and ipsilateral acoustic reflex thresholds were measured in response to 500-, 1000-, and 2000-Hz pure tones after the ingestion of a 50% alcohol solution. Acoustic reflex threshold measurements were obtained preingestion and at blood-alcohol concentrations of 0.03 to 0.10% in 0.01% increments. A linear relationship existed between acoustic reflex threshold and blood-alcohol concentration, with the greatest shift at 0.10% being 11 dB for contralateral stimulation and 7 dB for ipsilateral. No frequency effects were found. Results can be explained by the anatomical differences in the contralateral and ipsilateral pathways.

Adult↗
PubMed1979

Relationship between loudness discomfort level and acoustic reflex threshold for normal and sensorineural hearing-impaired individuals.

The relationship between loudness discomfort level (LDL) and acoustic reflex threshold (ART) was determined by comparing the ART to the LDL obtained by the psychophysical method of constant stimuli. Randomly presented stimuli of 1000 Hz, 2000 Hz, and a multi-talker speech noise were presented to normal and sensorineural hearing-impaired listeners. The listener's task was to judge whether the stimulus was at a level that was: (1) too loud or uncomfortably loud; or (2) not too loud or not uncomfortably loud. Prior to the judgement of the subject acoustic reflex threshold were determined. Both LDL and ART were found to be significantly higher for the hearing-impaired group. For the pure tone stimuli, LDL for the hearing-impaired group was at or below the ART. Significant differences were shown to exist between LDL and ART for each group. A multiple regression analysis indicated significant correlations between LDL and ART. Ranges of prediction error were selected to investigate the ability of ART to predict LDL. Both pure tone and speech ART successfully predicted LDL within +/- 10 dB for a high percentage of the subjects.

Adolescent↗
PubMed1979

Speech intelligibility in stapedectomized individuals.

We assessed the types of speech errors made in relation to the acoustic reflex. Ten subjects with unilateral stapedectomies were presented with consonant-vowel nonsense syllables in low pass noise at 70, 95, and 110 dB SPL in each ear. Hearing sensitivity for all subjects was normal or near-normal bilaterally. In the operated ear, speech intelligibility was significantly poorer than in the unoperated ear at all intensity levels. A distinctive feature analysis supported this finding. The data suggest that word discrimination testing in quiet does not adequately reveal the success of stapedectomy surgery. The distinctive feature analysis indicated that rather than consider the acoustic reflex as limiting the forward spread of masking into high frequencies, it would be better to describe it as a general aural overload regulator.

Acoustic Stimulation↗
PubMed1977

Clinical acoustic reflex threshold measurements in infants.

Acoustic reflex thresholds elicited using clinical acoustic impedance techniques were obtained on normal infants between one month and one year of age. Reflex activating signals of 500, 1000, 2000 Hz, low-pass, high-pass, and white noise were used. Less intensity was required to elicit the acoustic reflex to the noise than to the pure tones, with the 500-Hz tone requiring the greatest intensity. Inference of auditory thresholds from the acoustic reflex indicated the presence of normal hearing in the infant group.

Acoustic Impedance Tests↗
PubMedDate not supplied

Bone-conduction masking for threshold assessment in auditory brain stem response testing.

The viability of applying Sensorineural Acuity Level (SAL) audiometry to auditory brain stem response (ABR) testing was investigated using 38 subjects with normal hearing, conductive, sensorineural, and mixed hearing losses. The stimuli were clicks, 4000, 2000, and 1000 Hz tone-pips. After ABR thresholds (ABRt) were obtained, bone-conducted noise was used to mask the response to a stimulus 5 dB above ABR threshold (ABRt + 5). Estimates of behavioral bone-conduction thresholds were made by observing the amount of noise needed to mask ABRt + 5. Estimates of behavioral air-conduction thresholds were based upon ABRt. Results indicated that ABRt was within +/- 10 dB of behavioral air-conduction threshold across subject groups at least 74% of the time for all tone-pip stimuli. ABRt was within +/- 15 dB of the pure-tone average of 1000, 2000, and 4000 Hz 75% of the time when click stimuli were used. Derived bone-conduction thresholds were within +/- 10 dB of the actual bone-conduction threshold at least 73% of the time for all stimuli. It was concluded that, when used in a conservative manner, the application of SAL audiometry to ABR testing may increase the reliability and confidence with which decisions are made concerning the type and degree of hearing loss in difficult-to-test patients.

Adult↗
PubMedDate not supplied

Influence of ear canal air pressure on acoustic reflex threshold.

This study was undertaken to investigate the effects of ear canal air pressure variation on the threshold of acoustic reflex. The acoustic reflex threshold was obtained to 500 and 1000 Hz activating signals as pressure was varied between +/- 200 mm H2O. The results demonstrated a reduction in sensitivity of the acoustic reflex with variations in positive or negative air pressure. Observation of the conductance component of admittance consistently required higher intensity levels to elicit the acoustic reflex. Clinical implications are that external air pressure can vary within a range of +/- 80 mm H2O and continue to maintain the acoustic reflex threshold close to its value obtained at maximum compliance.

Adult↗
PubMedDate not supplied

Acoustic reflex thresholds using conventional and tracking methods.

Relationship between acoustic reflex thresholds obtained using conventional and tracking procedures was investigated. In the tracking method, the intensity of the stimulus from a self-recording audiometer is adjusted by the experimenter to bracket the acoustic reflex threshold as visually observed on the meter of an acoustic impedance measuring device. Acoustic reflex thresholds were obtained to pure tones of 500, 1000, and 4000 Hz. High correlations and no significant differences were obtained between the two threshold methods. It was concluded that the tracking method which allows easier control of stimulus parameters and response recording can provide acoustic reflex threshold data similar to those obtained using a conventional method.

Audiometry↗
PubMedDate not supplied

Effects of ethyl alcohol on the acoustic reflex threshold.

Acoustic reflex thresholds for pure tones and white nose were measured every 20 min for 4 hr after the ingestion of ethyl alcohol. The average maximum acoustic reflex threshold shift was 11 dB, occurring on the average at 100 min, and returning to base-line levesl at approximately 200 min postingestion. These data lend support to the classification of ethyl alcohol as a sedative, and should caution the clinician when interpreting acoustic reflex threshold data from persons who have ingested small amounts of alcohol.

Adult↗
PubMedDate not supplied

Acoustic admittance of the ear in the geriatric person.

The effects of age on acoustic admittance in a geriatric population were investigated in persons ranging in age from 50 to beyond 70 years. The results demonstrated a significant decrease in admittance for the 70-year-old group, with the change being primarily attributable to a decrease in susceptance. Women consistently demonstrated lower admittance than men. The data obtained suggest that different norms for static admittance be applied to persons above 70 years of age.

Acoustics↗
PubMedDate not supplied

Effects of human middle ear muscle contractions on speech intelligibility.

The present study assessed the relationship between the acoustic reflex and speech intelligibility. Monosyllabic words mixed with noise were presented at -6, -3.0 and +3 dB signal-to-noise ratios. The word lists were presented with a 2000-Hz tone in the contralateral ear at a level 15 dB above or 20 dB below the acoustic reflex threshold to evaluate intelligibility differences with the acoustic reflex contracted and relaxed. The results indicated that a significant decrement in speech intelligibility differences with the acoustic reflex contracted and relaxed. The results indicated that a significant decrement in speech intelligibility occurred with the reflex contracted at signal-to-noise ratios of -3, and 0 dB. Slight but not significant decrements were seen at -6 and +3 dB signal-to-noise ratios. These results are discussed along with possible reasons for the lack of agreement with previous research.

Adult↗