Search

Binaural interaction in the brainstem and middle latency auditory evoked potentials to intensity (dI) and timing differences (dT) between the two ears was studied in 10 normal hearing young adults. A component reflecting binaural interaction in the brainstem potentials occurred at approximately 7 ms and was of largest amplitude when dI and dT were 0. The latency of the binaural interaction component gradually shifted and its amplitude decreased as dI or dT increased and binaural interaction became undetectable when dI = 16 dB or when dT > or = 1.6 ms. In the middle latency potentials binaural interaction components peaking at 20, 32, and 45 ms were defined that were also largest when dI and dT = 0. The latency of the interaction did not shift with changes in dT and dI whereas the amplitude gradually decreased but binaural interaction components were still evident even at the largest values of dI (30 dB) and dT (3 ms). Psychophysical judgments of binaural perceptions showed binaural fusion of the stimuli to persist with dT values up to 1.6 ms and that lateralization of the intracranial image was complete when either dT = 1.6 ms or when dI = 16 dB. The results suggest that the presence of a binaural interaction component of auditory brainstem potentials correlates with the fusion of binaural click stimuli and the amplitude of the binaural interaction component correlates inversely with the degree of lateralization of the intracranial image. Binaural interaction components of middle latency potentials persist and continue to change even after the binaural stimuli cannot be fused.

Binaural interaction occurs in the auditory evoked potentials when the sum of the monaural auditory evoked potentials are not equivalent to the binaural evoked auditory potentials. Binaural interaction of the early- (0-10 ms), middle- (10-50 ms) and long-latency (50-200 ms) auditory evoked potentials was studied in 17 normal young adults. For the early components, binaural interaction was maximal at 7.35 ms accounting for a reduction of 21% of the amplitude of the binaural evoked potentials. For the middle latency auditory evoked potentials, binaural interaction was maximal at 39.6 ms accounting for a reduction of 48% of the binaural evoked potential. For the long-latency auditory evoked potentials, binaural interaction was maximal at 145 ms accounting for a reduction of 38% of the binaural evoked potential. In all of the auditory evoked potentials binaural interaction was long lasting around the maxima. The binaural interaction component extends for several milliseconds in the brainstem to tens of milliseconds in the middle- and long-latency components. Binaural interaction takes the form of a reduction of amplitude of the binaural evoked potential relative to the sum of the monaural responses, suggests that inhibitory processes are represented in binaural interaction using evoked potentials. Binaural processing in the auditory pathway is maximal in the time domain of the middle-latency components reflecting activity in the thalamo-cortical portions of the auditory pathways.

The contribution of the cerebral cortex to the generation of sensory evoked potentials was studied in an infant with hydranencephaly. On CT scan no tissue above the thalamus was noted. Long-latency potentials to auditory stimuli were absent whereas the short-latency or brain-stem auditory evoked potentials and some of the components of the middle latency auditory evoked potentials (No and Po) were present. To visual stimulation only the electroretinogram was detected. To somatosensory stimulation only the spinal cord potentials could be detected. The absence of long-latency components in each of the sensory modalities supports the concept that these potentials require intact cerebral hemispheres in man.

Binaural interactions in brain-stem auditory evoked potentials and in middle latency auditory evoked potentials were studied in 18 normal hearing adults and 10 normal term infants. Binaural interactions at the times of ABR waves V and VI were comparable in term infants and adults. Binaural interaction during the time domain of the middle latency auditory evoked potentials was the greatest at N20 in term infants and at N40 in adults. Measurement of binaural interaction during maturation may be a useful tool in assessing neurologically affected infants.

The auditory evoked brain stem potential was recorded in 14 normal full-term infants and nine normal-hearing adults. Silver-silver chloride electrodes were placed at nasion, forehead, vertex, each mastoid over the bony prominence, and the seventh cervical vertebra (noncephalic reference) in order to study the scalp distribution of the auditory brain stem response. Large differences in the scalp distribution between the newborn and adult populations were observed. At the ipsilateral mastoid, an x wave occurring at approximately 2 ms and a y wave occurring at approximately 3.3 ms were identified in the adult; this contrasts to a y wave at approximately 3.7 ms in the neonate. It appears that there are either separate generators for some of the components in the adult versus the neonate, and/or as the nervous system matures, myelinization occurs with a concomitant change in the scalp distribution of the auditory brain stem potentials.

Insomnia affects millions of people worldwide, and non-pharmacological treatment options are limited. A bed excited with multiple vibration sources was used to explore beat frequency vibration (BFV) as a non-pharmacological treatment for insomnia. A repeated measures design pilot study of 14 participants with mild-moderate insomnia symptom severity (self-reported on the Insomnia Severity Index) was conducted to determine the effects of BFV, and traditional standing wave vibration (SWV) on sleep latency and sleep electrocortical activity. Participants were monitored using high-density electroencephalography (HD-EEG). Sleep latency was compared between treatment conditions. A trend of decreasing sleep latency due to BFV was found for unequivocal sleep latency (p ≤ 0.068). Neural complexity during wake, N1, and N2 stages were compared using Multi-Scale Sample Entropy (MSE), which demonstrated significantly lower MSE between wake and N2 stages (p ≤ 0.002). During N2 sleep, BFV showed lower MSE than the control session in the left frontoparietal region. As a measure of information integration, reduced entropy may indicate that BFV decreases conscious awareness during deeper stages of sleep. SWV caused reduced alpha activity and increased delta activity during wake. BFV caused increased delta activity during N2 sleep. These preliminary results suggest that BFV may help decrease sleep latency, reduce conscious awareness, and increase sleep drive expression during deeper stages of sleep. SWV may be beneficial for decreasing expression of arousal and increasing expression of sleep drive during wake, implying that beat frequency vibration may be beneficial to sleep.

Objective: This study identified, digitally recorded, edited and evaluated 89 bisyllabic Vietnamese words with the goal of identifying homogeneous words that could be used to measure the speech recognition threshold (SRT) in native talkers of Vietnamese., Design: Native male and female talker productions of 89 Vietnamese bisyllabic words were recorded, edited and then presented at intensities ranging from -10 to 20 dBHL. Logistic regression was used to identify the best words for measuring the SRT. Forty-eight words were selected and digitally edited to have 50% intelligibility at a level equal to the mean pure-tone average (PTA) for normally hearing participants (5.2 dBHL)., Study Sample: Twenty normally hearing native Vietnamese participants listened to and repeated bisyllabic Vietnamese words at intensities ranging from -10 to 20 dBHL., Results: A total of 48 male and female talker recordings of bisyllabic words with steep psychometric functions (>9.0%/dB) were chosen for the final bisyllabic SRT list. Only words homogeneous with respect to threshold audibility with steep psychometric function slopes were chosen for the final list., Conclusions: Digital recordings of bisyllabic Vietnamese words are now available for use in measuring the SRT for patients whose native language is Vietnamese.

Objective: Masking level difference (MLD) tests are an established component of auditory processing test batteries; however, normative data for these tests vary according to procedure. The purpose of this study was to establish a standardized procedure for clinical use in the measurement of the MLD., Design: A newly developed computer software program using both an adaptive procedure (MLDA) and a Békésy procedure (MLDB) was evaluated in this study., Study Sample: Forty normal-hearing, native-English speaking adults between the ages of 18 and 26 years were included in the study., Results: Both the MLDA and MLDB procedures showed statistically significant sex differences in the masked thresholds used to obtain the MLD, but not for the calculated MLD value; hence, normative data need not be reported separately by sex. Furthermore, statistically significant differences between procedures were observed, with the MLDA procedure producing higher MLDs. The MLDA procedure permitted a d' analysis, which could not be determined using the MLDB procedure. For MLDA, d' = 1.4, test sensitivity = 96.4%, and test specificity = 60.3%., Conclusions: The results of this study indicate that MLDA is a more efficient testing procedure due to MLDA's higher MLD average and the statistical data available (d', and measures of sensitivity and specificity).

The Special Olympics Healthy Hearing Program provides a unique opportunity to determine the hearing service needs of individuals with mild intellectual disabilities participating in athletic endeavors in countries throughout the world. The Healthy Hearing Program screened 855 of 1800 athletes with intellectual disability over a period of a week at Nagano, Japan. Of 855 athletes screened, 58% passed the DPOAE screen and therefore required no further testing. Of the remaining 42%, 186 did not pass pure-tone screening. This number of athletes represents 21.8% of all athletes screened. Tympanometry outcomes for the 186 athletes failing pure-tone screening showed 56% (104) also failing this measure of middle-ear function. 65% of these 104 athletes' outer ear canals were blocked/partially-blocked with cerumen. This amount is in contrast to the 38% presence of cerumen for the 82 athletes failing pure-tone screening but passing tympanometry.

Despite the large number of individuals who speak Russian, only a limited number of high-quality speech audiometry materials are available in a standard dialect of Russian. Thus, the purpose of this study was to develop and evaluate speech audiometry materials that can be used to measure word recognition and SRT testing in quiet for native speakers of Russian. Familiar monosyllabic and bisyllabic words were digitally recorded by male and female talkers of Russian and subsequently evaluated by native listeners. Using logistic regression, psychometric functions were then calculated for all words. Selected monosyllabic words were digitally adjusted to create word recognition lists which are relatively homogeneous with respect to audibility and psychometric slope. Speech reception threshold materials were developed by selecting twenty-five bisyllabic words with relatively steep psychometric function slopes (12.1%/dB and 9.9 %/dB) and digitally equating their intensity to match the mean PTA of the native listeners. Digital recordings of the resulting psychometrically equivalent speech audiometry materials are available on compact disc.

This study investigated the effect of variable interstimulus intervals (ISIs) in a group of normal and ADHD (attention deficit hyperactivity disorder) adults on behavioral reaction time and the auditory P300 event-related potential. This study involved 20 adult subjects with no history of ADHD and 11 adult subjects diagnosed with ADHD. The subjects were instructed to respond to the common stimuli and ignore the rare stimulus. Significant differences in the latency of the P300a, P300b, the amplitude of the P300b, and in the number of false alarms and correct rejections between ISIs were observed in the normal group. The group with ADHD failed to show any significant differences between ISIs. Psychophysical measures of hits showed significant differences for the number of hits for ISI 2 (2 sec) between the two groups. False alarms and correct rejections for all ISIs showed significant differences between groups. Significant group differences were seen for latency of the P300a and P300b at each of the three ISIs, for amplitude of the P300a and P300b for ISI 1 and ISI 3, and for the amplitude of the P300b for ISI 2. There was a greater separation in the group with ADHD between the P300a and P300b suggesting a processing lag in that group.

This study investigated the effect of variable interstimulus intervals (ISIs) on behavioral reaction time (RT) and on the latency and amplitude of the auditory P300 using an auditory continuous performance task (ACPT) paradigm. Twenty subjects were instructed to respond to common stimuli and ignore a rare stimulus. Common stimuli were 1000-, 1500-, and 2000-Hz pure tones. The rare stimulus was a 250-Hz pure tone. ISIs of 1, 2, and 4 seconds were used for this investigation. A significant correlation between ISI, reaction time, P300 latency, correct rejections, and false alarm rates was found. A significant correlation between P300 latency, P300 amplitude, correct rejections, and false alarm rates was also observed. Likewise, a statistically significant increase in reaction time (RT) was observed as ISI increased. The ACPT paradigm in conjunction with the auditory P300 response can measure both behavioral and electrophysiologic changes that occur during active auditory attention and auditory cognitive processing tasks.

Brainstem auditory evoked potentials and middle latency auditory evoked potentials were recorded from 21 normal hearing children between 8 and 13 years of age. An age-matched control group of 13 children was used to compare the results of 8 children diagnosed with ADHD. One sample of 2000 averages was collected for right monaural, left monaural, and binaural stimulus presentation conditions. The binaural interaction component was then determined using the formula: [(right monaural+left monaural)--binaural]. Absolute latencies and amplitudes for waves V, N20, P30, and N40 were then compared using descriptive statistics, analysis of variance, and matched t-tests. Percent binaural interaction was also computed for both groups. Significant differences were noted between control and ADHD groups on measures of N40 amplitudes for binaural stimulation, N40 amplitude for the sum of the right and left monaural waveforms, and percent binaural interaction at N40. These results suggest a dysfunction or immaturity in the auditory activity of the thalmo-cortical projections.

A series of 20 normal newborn term infants and 12 infants born to mothers who had abused opiates during pregnancy were studied. Auditory brainstem-evoked potentials were used to describe neurophysiologic dysfunction in a group of drug-addicted term infants. Significant differences in the auditory brainstem-evoked potentials were found between the two groups. Specifically, a decrease in the central conduction times was noted for the I-III interpeak interval, suggesting neurophysiologic dysfunction in the area of the pons and cerebellum.

Fifteen infants with hydrocephalus ranging in age from 32 to 43 weeks from conception were studied. The auditory brainstem response (ABR) was measured 48 h prior to the placement of a CSF shunt and within 5 days following shunt insertion. Results of this study showed a general improvement in the ABR following placement of the shunt. No consistent patterns were observed that allowed a clear explanation of the cause and effect of the abnormal ABR. However, the changes seen in the ABR are caused by increased CSF pressure, which may compress the transmission fibers, and generators of the ABR producing a type of neuropraxis. Early shunting appears to have a better outcome on the ABR than later shunting.

The auditory evoked response (AER) was used to study the effect of increased intracranial pressure (ICP) on the auditory pathway in normal New Zealand rabbits and in those made hydrocephalic by intracisternal injections of kaolin. AERs were studied: (a) in the normal and then in the hydrocephalic animal; and (b) in the hydrocephalic animal during further ICP elevation by cerebrospinal fluid infusion. The AER was obtained from ongoing electroencephalographic activity after rarefaction auditory clicks presented at 90 dB sound pressure equivalent. In comparing base line normal AERs to those found in hydrocephalic conditions, a statistically significant increase in latency for AER components N2, P2, and P5 was noted in hydrocephalic rabbits. Increased ICP in the hydrocephalic model showed an increase in the latencies of AER components for P0 and P1 at 250 mm H2O, and a prolongation of P3-P5 central conduction time at 700 mm H2O above base line cerebrospinal fluid pressure. In addition, a decrease in the P4/N5 amplitude and an increase in P1-P3 central conduction times at 700 mm H2O was observed. The differences between normal and hydrocephalic rabbit AER base lines may be the result of the chronically increased ICP and presumed chronic anatomical changes within the auditory pathway due to kaolin itself. The differences in the AER from base line hydrocephalus to acute increased ICP may indicate that the hydrocephalic system is more sensitive to acute neuropraxic pressure effects on the brain stem auditory structures than is the normal brain.

This investigation confirmed previous studies indicating that the middle and inner ear of the guinea pig have a pronounced tendency to healing. Middle ear hemorrhage of surgical origin appears to stop quickly in the guinea pig. A surgically created perforation of the round window with or without removal of perilymphatic fluid by suction resulted in a spontaneous healing of the round window membrane in 12/13 animals. Perilymphatic hemorrhage, associated with short post-surgical interval was found in a substantial number of cases. The origin of the perilymphatic hemorrhage is doubtful. Degeneration of the organ of Corti was found in four ears in three animals and appeared to be correlated to the perilymphatic hemorrhage. Electrophysiological measurements appeared to correlate well with the anatomical findings for one animal with very small changes and for three animals with pronounced middle and inner ear pathology. In three additional animals less agreement was observed. In general these animals showed a more pronounced decrease of function than would be expected by the anatomy.