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PubMed1989

Does selective attention influence the brain-stem auditory evoked potential?

We have re-examined the problem of selective attention in relation to brain-stem auditory evoked potentials (BAEPs). We compared BAEPs recorded in the relaxed individual with those elicited during visual attention and during auditory attention. Particular emphasis was placed on the use of a demanding visual task to ensure appropriately sustained levels of concentration by the subject for the durations of the tests. We measured the latency of wave I, the wave I-V interval and the amplitudes of waves I and V in 16 subjects in each of the conditions but could find no effect attributable to changes in states of attention. We conclude that there is no evidence for the actions of gating or switching mechanisms at early stages of the auditory pathways.

Adolescent↗

PubMed1990

Oversized, auditory responsive units of rostral, mid, and posterolateral thalamus.

Activity was recorded from 343 units of rostral, mid, and posterolateral thalamus following a conditioned click stimulus (CS). Over 40% of units responded with increased discharge in cats conditioned to blink to the CS. Twenty-nine units with short latency (less than 40 ms) responses were injected intracellularly with phaseolus lectin and identified morphologically; 83% had long, thick primary dendrites with smaller secondary branches. Almost half (46%) had larger somata than the largest previously described thalamic neurons of this morphologic classification. The results suggest that a previously unidentified class of oversized cells is likely to contain many short latency, auditory responsive units. A substantial number of these cells (36%) projected extrathalamically into the internal capsule, and thus may constitute a new auditory pathway between thalamus and cortex.

Acoustic Stimulation↗

PubMed1984

Intracranial pressure effects on auditory evoked responses in the rabbit: preliminary report.

Acute elevated intracranial pressure (ICP) effects on the auditory evoked response (AER) were studied in the rabbit. Simultaneous CSF infusions to increase ICP and contralateral ICP pressure recordings were done through bilateral ventriculostomies. During rarefaction auditory stimulation, a minicomputer obtained a time-locked AER from ongoing electroencephalographic activity at base line ICP mean pressure and at three levels of increased ICP (250, 500, and 700 mm CSF) above base line. The results showed a statistically significant increased latency of the N3-P3 portion of the AER as well as of the P1-P3 central conduction time. The amplitude of AERs appeared unchanged. The effect is reversible and presumably is a neuropraxic type pressure effect on brain stem auditory pathways. Its clinical relevance is discussed.

Acoustic Stimulation↗

PubMed1983

Maturation of the auditory brain stem response in rhesus monkeys (Macaca mulatta).

To document the maturational changes in the auditory brain stem response (ABR) of the rhesus monkey, longitudinal and cross-sectional data were collected on a panel of 31 animals during the first year of life. Each ABR test consisted of averaging 2048 responses to click stimuli delivered at a rate of 21 clicks/sec and elicited at 60, 40, 20 and 10 dB HL intensities in accordance with procedures described previously. The morphology of the ABR wave form recorded at birth was similar to that at 12 months of age and the latencies of the component waves decreased exponentially over this period. The magnitude of decrease in latency was greatest for wave IV and least for wave I. The regression lines for the log of the latencies of 3 waves on age were computed for 3 animals followed longitudinally and for the cross-sectional data set. The slopes of these regression lines were different among animals, indicating differing rates of maturation. However, these slopes were identical for the component waves of any one animal, suggesting that the rate of maturation was constant over the auditory pathway. These changes were similar in pattern to those reported for human data and suggest that the rhesus monkey may serve as an appropriate model of auditory development in man.

Animals↗

PubMed2002

Perinatal exposure to Aroclor 1254 impairs distortion product otoacoustic emissions (DPOAEs) in rats.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are a potential health hazard to human and wildlife populations. Low-frequency auditory impairments have previously been documented in Aroclor 1254 (A 1254)-exposed rats, including elevated behavioral auditory thresholds and decreased amplitude and prolonged latency auditory evoked brain stem responses (ABRs). Furthermore, outer hair-cell loss on the basilar membrane of the cochlea has been documented, demonstrating that the cochlea is a target organ for PCB ototoxicity. The current experiment assessed the effects of A1254 on cochlear function by measuring distortion product otoacoustic emissions (DPOAEs). ABRs were measured to determine the effects of A1254 on the central nervous system auditory pathways. Pregnant Long-Evans rats received either 0 or 6 mg/kg A1254 (po) in corn oil from gestation day 6 to lactational day 21. The auditory function of male and female offspring was assessed at approximately 18 months of age. The rats were anesthetized and a probe-unit, consisting of 2 insert earphones and a microphone, was positioned in the ear canal. DPOAE amplitudes were reduced and thresholds increased in the A1254-exposed rats. The deficits were most pronounced at the lowest frequencies tested (2.1-3.2 kHz), but deficits were also observed at higher frequencies (3.7-8.6 kHz). Males and females were equally affected at the lower frequencies, but females were more impaired at the higher frequencies. In contrast, ABR latencies and amplitudes were not altered by A1254 exposure. These findings provide the first functional evidence supporting a cochlear site of damage in PCB-induced hearing loss.

Animals↗

PubMed2003

Activity-dependent developmental plasticity of the auditory brain stem in children who use cochlear implants.

OBJECTIVES: 1) To determine if a period of early auditory deprivation influences neural activity patterns as revealed by human auditory brain stem potentials evoked by electrical stimulation from a cochlear implant. 2) To examine the potential for plasticity in the human auditory brain stem. Specifically, we asked if electrically evoked auditory potentials from the auditory nerve and brain stem in children show evidence of development as a result of implant use. 3) To assess whether a sensitive or critical period exists in auditory brain stem development. Specifically, is there an age of implantation after which there are no longer developmental changes in auditory brain stem activity as revealed by electrically evoked potentials? DESIGN: The electrically evoked compound potential of the auditory nerve (ECAP) and the electrically evoked auditory brain stem response (EABR) were recorded repeatedly during the first year of implant use in each of 50 children. The children all had pre- or peri-lingual onset of severe to profound sensorineural hearing loss and received their implants at ages ranging from 12 mo to 17 yr. All children received Nucleus cochlear implant devices. All children were in therapy and in school programs that emphasized listening and required the children to wear their implants consistently. RESULTS: Initial stimulation from the cochlear implant evoked clear responses from the auditory nerve and auditory brain stem in most children. There was no correlation between minimum latency, maximum amplitude, or slope of amplitude growth of initial responses with age at implantation for ECAP eN1, EABR eIII and eV components (p > 0.05). During the first year of implant use, minimum latency of these waves significantly decreased (p < 0.01, p < 0.0001, p < 0.0001, respectively). Neural conduction time, measured using the interwave latency of ECAP eN1-EABR eIII for lower brain stem and EABR eIII-eV for upper brain stem, decreased during the period of 6 to 12 mo of cochlear implant use (p < 0.01 (lower), p < 0.0001(upper)). The ECAP wave eN1 and the EABR wave eV showed significant increases in amplitude during time of implant use (p < 0.05 and p < 0.01, respectively). There were no correlations between the rate of interwave latency decrease and the rate of amplitude increases and the age at which children underwent implantation (p < 0.05). CONCLUSIONS: Activity in the auditory pathways to the level of the midbrain can be evoked by acute stimulation from a cochlear implant. EABR measures are not influenced by any period of auditory deprivation. Auditory development proceeds once the implant is activated and involves improvements in neural conduction velocity and neural synchrony. Underlying mechanisms likely include improvements in synaptic efficacy and possibly increased myelination. The developmental plasticity that we have shown in the human auditory brain stem does not appear from EABR data to be limited by a critical period during childhood.

Adolescent↗

PubMed1995

Relationship between frequency of spontaneous bursting and tonotopic position in the developing avian auditory system.

Neural activity in the developing brainstem auditory pathway of the chick embryo is dominated by a rhythmic pattern of spontaneous discharge. Neurons in nucleus magnocellularis (NM) and nucleus laminaris (NL), second and third order auditory nuclei, discharge spontaneously in synchronous bursts at periodic intervals. Rhythmic bursting is present as early as embryonic day 14 (E14), shortly after the onset of functional synaptogenesis, and gives way to an adult-like, steady level of firing on E19, two days prior to hatching. In the present experiment, multiple-unit recording techniques were used in E17 and E18 embryos to examine the relationship between rate of rhythmic bursting and tonotopic position in NM and NL. The mean rate of rhythmic bursting ranged from 0.21-0.71 Hz. Bursting rate varied systematically as a function of position, being faster at progressively higher frequency regions of the nuclei at both E17 (r = 0.75) and E18 (r = 0.86). In addition, the rate of bursting at a given location in the nuclei increased during development. The presence of a systematic relationship between the rate of rhythmic bursting and tonotopic location suggests that the spatio-temporal pattern of spontaneous discharges could provide developmental cues for the spatial ordering of auditory projections.

Acoustic Stimulation↗

PubMed1982

Logarithmic display of auditory evoked potentials.

Auditory evoked potentials (AEP) can be simultaneously recorded on-line as a succession of 11 waves, through a single input channel of a mini-computer. Since the response waves differ widely in frequency, a computing routine has been developed to display the whole response pattern in a single picture. Based upon a non-linear samples reduction of the digitized response, this routine allows a logarithmic transformation of the time axis. The method improves the identification of the AEP components and provides an objective estimate of the central auditory pathway for both neurophysiological and neuroclinical studies.

Computers↗

PubMed1990

Auditory brainstem responses to tonal stimuli in young and aging rats.

The auditory brain stem response (ABR) was studied in young adult and aged rats using 3,8 and 40 kHz tone pips. The expected inverse relationship between frequency and latency was observed in the younger group for waves I, II and III, while the response to the highest frequency stimulus had the longest latency at wave V. Absolute latencies for waves I through V each showed age-related increments with more pronounced changes occurring to 3 and 40 kHz stimuli than to the frequency of maximum sensitivity (8 kHz). Threshold increases with age for the highest frequency approximately doubled those for the lower frequencies. Examination of interpeak intervals (IPI) I-III, III-V and I-V revealed aging effects. The largest IPI I-V increment occurred to 3 kHz stimulation which reflects changes at both I-III and III-V sub-intervals. These results demonstrate electrophysiological correlates of aging due to transformations in the peripheral auditory system coupled with alterations in brainstem auditory pathways.

Acoustic Stimulation↗

PubMed1992

Influence of experimentally elevated blood viscosity on the auditory nerve-brainstem evoked response and threshold.

Blood viscosity, due to its effect on blood flow, is one of the determinants of oxygen delivery. Therefore the influence of elevated blood viscosity on hearing was studied in rats using the auditory brainstem response (ABR) threshold, wave 1 latency, brainstem transmission time (BTT) and wave 1/4 amplitude ratio. Whole blood viscosity (WBV) was elevated by 15-21% in two different ways: elevating the hematocrit (Polycythemia) by acclimation in a hypobaric chamber, or elevating the plasma viscosity by infusing a solution of Polyvinylpyrrolidone-360 (PVP). ABR was recorded before and 24 h after the blood viscosity was elevated, so that each rat served as its own control. Paired t-tests showed that there was no statistically significant difference in the ABR parameters in each of the groups as a consequence of blood viscosity elevation. In conclusion, the elevation of WBV to this degree for this duration, using two different techniques had no effect either on the function of the auditory nerve and the more peripheral sites, or on the central auditory pathway as studied by ABR.

Analysis of Variance↗

PubMed1992

Auditory brainstem evoked potentials (BAEPs) in lead-exposed workers.

Brainstem Evoked Potentials (BAEPs) were recorded in 49 lead exposed workers, and in a control group of 49 age- and sex-matched subjects, never exposed to neurotoxic substances. The mean duration of lead exposure was 7.4 (SD 5.6) yr. Blood lead concentration was analyzed in the morning of the experimental day (PbBc); an averaged PbB level was based on the levels of the 3 previous years (PbBm). Interpeak latency differences (IPLD) I-V, I-III and III-V were considered. The mean PbBc level was 54.6 (SD 16.1) micrograms/dl while the mean PbBm level was 53.5 (SD 15.9) micrograms/dl. Lead exposed workers showed a significant prolongation of IPLDs. IPLD I-V was longer in the subgroup with PbBm greater than 50 micrograms/dl (4.06 vs 3.98, c.l. 95% 0.00-0.16). These results are consistent with literature data and show that BAEPs may be a sensitive detector of subclinical lead effects on brainstem auditory pathways.

Adult↗

PubMedDate not supplied

[Auditory evoked potentials in alcoholics].

In this paper, auditory brain stem potentials in the group of 26 alcoholics were studied and a significantly delayed latencies of the peaks II through V as compared to the healthy control subjects were found. In addition, a statistically significant prolongation of brain stem transmission time (BTT) in alcoholics was observed. The study also suggests the possibility of monitoring the level of pathohistological changes of the central auditory pathway caused by excessive alcohol consumption.

Adult↗

PubMed1998

[Auditory evoked magnetic fields in patients of pure word deafness].

Auditory evoked magnetic fields (AEF) were recorded in 2 cases with pure word deafness. AEF examination were performed with a novel 129-channel vector neuromagnetic imaging system (SBI 100). The latency and the location of equivalent current dipole (ECD) of N100 m after 1,000 Hz tone burst stimulation, one of the most prominent peak of AEF, were evaluated. One patient, 59-year-old man, suffered from left putaminal hemorrhage and the other, 59-year-old man, had a history of bilateral putaminal hemorrhage. There was no N100 m detected in the left temporal lobe with the right ear stimulation in both patients. However normal N100 m was obtained in the right hemisphere with the left ear stimulation in both cases. And the position of ECD of N100 m in the right hemisphere were correctly superimposed on the Heschl gyrus in brain MRI. The pathophysiology of pure word deafness has been postulated that a disconnection between Wernicke area and bilateral auditory inputs played one of important roles in progression of pure word deafness. Because there was no pathological lesion in temporal lobe verified by MRI study in both patients, N100 m in the left could not be evoked due to interception of the auditory pathway to the Heschl gyrus, but not due to destruction of Heschl gyrus. AEF test is one of the most useful tools in order to estimate central auditory function in patients with pure word deafness.

Aphasia, Wernicke↗

PubMed1996

Auditory-evoked brainstem responses in the torpid deermouse.

This study examined auditory-evoked brainstem responses (ABR) in the deermouse (Peromyscus maniculatus) during torpor and arousal. The ABR of the euthermic deermouse consisted of five waves occurring in a time frame of 10 ms. During torpor, ABR wave I could be elicited at slow, but not fast stimulation rates indicating variability in neural activity along the auditory pathway. Arousal was heralded by the appearance of all the components of the ABR evoked in response to both slow and fast click rates signaling functional restoration of auditory neural activity during this phase.

Acoustic Stimulation↗

PubMedDate not supplied

Parallel processing in the auditory cortex of primates.

Evidence from anatomical tracer studies as well as lesions of the primary auditory cortex (AI) indicate that the principal relay nucleus of the auditory thalamus, the ventral part of the medial geniculate (MGv), projects in parallel to AI and the rostral area on the supratemporal plane of the macaque monkey. The caudomedial area, by contrast, receives input from MGv only indirectly via AI, and neurons in this area are often tuned to the spatial location of a complex sound. The belt areas on the lateral surface of the superior temporal gyrus receive input from the primary areas. Neurons in these areas respond better to more complex stimuli, such as band-pass noise pulses of frequency-modulated sweeps, than to pure tones. Often neurons in the lateral belt respond well to species-specific communication calls. The hypothesis is put forward that the central auditory pathways in the macaque monkey are organized into parallel streams, similar to the visual system, one for the processing of spatial information, the other for the processing of auditory "patterns". Evidence from neuroimaging studies in humans with MRI and PET are consistent with this hypothesis. Virtual auditory space stimuli lead to selective activation of an inferior parietal region, whereas speech-like stimuli activate superior temporal regions.

Animals↗

PubMed2000

Topographic and temporal indices of vowel spectral envelope extraction in the human auditory cortex.

The auditory-evoked neuromagnetic field elicited by single vowel formants and two-formant vowels was recorded under active listening conditions using a 37-channel magnetometer. There were three single formants with formant frequencies of 200, 400, and 800 Hz, another single formant with a formant frequency of 2600 Hz, and three vowels that were constructed by linear superimposition of the high- onto one of the low-frequency formants. P50 m and N100 m latency values were inversely correlated with the formant frequency of single formants. A strong effect of formant frequency on source location was obtained along the postero-anterior axis, which is orthogonal to the well-established latero-medial tonotopic gradient. Regardless of whether single formants or first formants of vowels were considered, N100 m sources were more anterior and sustained field sources were more posterior for higher-frequency than for lower-frequency formants. The velocity of the apparent posterior-to-anterior movement across cortical surface of N100 m sources first reported by Rogers et al. [Rogers, R. L., Papanicolaou, A. C., Baumann, S. B., Saydjari, C., & Eisenberg, H. M. (1990). Neuromagnetic evidence of a dynamic excitation pattern generating the N100 auditory response. Electroencephalography and Clinical Neurophysiology,77, 237-240] decreased as a function of latency. The amount of deceleration was positively correlated with formant frequency. Responses to the vowels were superadditive, indicating that the processes elicited by the constituents of composite stimuli interact at one or more stages of the afferent auditory pathway. Such interaction may account for the absence of a lateral-to-medial tonotopic mapping of first formant frequency. The source topography found may reflect activity in auditory fields adjacent to AI with the strength of the contribution varying with formant frequency. Alternatively, it may reflect sharpness-of-tuning and inhibitory response-area asymmetry gradients along isofrequency stripes within AI. Either alternative may be interpreted in terms of a spectral blurring mechanism that abstracts spectral envelope information from the details of spectral composition, an important step towards the formation of invariant phonetic percepts.

Adult↗

PubMed1975

Masking level difference: a measure of auditory processing capability.

MLDs are evidence of the superiority of the binaural auditory system. Cochlear lesions do not necessarily impair the MLD and persons with cortical lesions are also able to produce normal MLDs. The evidence for intermediate level auditory pathway lesions is more equivocal. The MLD is not the only measure of binaural hearing and binaural hearing is itself only one measure of a number of complex auditory processes. In this experiment measures of MLDs, localization, temporal integration, central masking and difference limen for intensity were made on 11 persons with normal hearing. Correlational analyses including factor analysis indicated that the MLD is a fairly independent measure but that central masking, brief tone audiometry and difference limen for intensity represent related auditory tasks. The relationship of localization tasks in this picture is unclear.

Acoustic Stimulation↗

PubMed1993

Assessment of central, peripheral, and autonomic nervous system functions in vibrating tool operators: neuroelectrophysiological studies.

To evaluate the effects of vibrating tool operation (i.e., combined stressors of local vibration, noise, cold climate, and heavy work) on the central, peripheral, and autonomic nervous systems, the short-latency somatosensory and brain stem auditory evoked potentials (SSEP and BAEP), the distribution of sensory median nerve conduction velocities (DCV), conventional median nerve conduction velocities (NCV), and the electrocardiographic R-R interval variability (CVRR) were measured in three groups of male vibrating tool operators and age-matched male healthy adults. Two components of the CVRR reflecting parasympathetic activity (C-CVRSA) and sympathetic activity (C-CVMWSA) were also examined. In the first group of vibrating tool operators (15 chain saw operators), all parameters of DCV (V10-V90 velocities) and sensory and motor nerve conduction velocities of NCV were significantly slowed. All peak latencies of SSEP were significantly prolonged, while no significant differences were found in the interpeak latencies of SSEP. The N9 peak latency of SSEP was significantly related to total working days. In the second group of the operators (12 chain saw and 8 brush saw operators), the I-V interpeak and V peak latencies of BAEP were significantly prolonged in the 12 chain saw operators; the I-V interpeak latency of BAEP was significantly correlated with the working years in the 8 brush saw operators. In the third group of vibrating tool operators, i.e., 13 operators with a history of vibration-induced white finger (VWF group) and 11 operators without VWF (non-VWF group), both the CVRR and C-CVRSA were significantly reduced in the VWF group; only the CVRR was significantly reduced in the non-VWF group. Similarly, the faster velocities of DCV (V70, V80, and V90 velocities) were significantly slowed in both the VWF and non-VWF groups. In conclusion, it is suggested that vibrating tool operation affects the faster sensory and motor nerve fibers, the parasympathetic activity, and the auditory pathway from the acoustic nerve to the brain stem.

Adult↗