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PubMed2006

Beyond the right hemisphere: brain mechanisms mediating vocal emotional processing.

Vocal perception is particularly important for understanding a speaker's emotional state and intentions because, unlike facial perception, it is relatively independent of speaker distance and viewing conditions. The idea, derived from brain lesion studies, that vocal emotional comprehension is a special domain of the right hemisphere has failed to receive consistent support from neuroimaging. This conflict can be reconciled if vocal emotional comprehension is viewed as a multi-step process with individual neural representations. This view reveals a processing chain that proceeds from the ventral auditory pathway to brain structures implicated in cognition and emotion. Thus, vocal emotional comprehension appears to be mediated by bilateral mechanisms anchored within sensory, cognitive and emotional processing systems.

Affect↗
PubMed1997

Temporal distortion products (kernel slices) evoked by maximum-length-sequences in auditory neuropathy: evidence for a cochlear pre-synaptic origin.

When special pseudo-random stimuli sequences (maximum length sequences: MLS) are combined with a deconvolution analysis technique, it is possible to derive new evoked potential components that are called kernels. The kernels give a measure of the temporal interactions that take place between the responses to successive stimuli. This may provide an objective neurophysiological test for the exploration of a dimension of hearing which has hitherto been limited to psychophysical methods. Until now, auditory short-latency kernels obtained by the MLS method have been related to the late portion of the brainstem auditory evoked potential (BAEP), suggesting that temporal interactions occur rather late in the auditory pathways. We report 4 children without any BAEP neural components, who all retained isolated cochlear microphonic potentials. Three of them produced click-evoked otoacoustic emissions and two of them demonstrated only moderately impaired audiometric thresholds. This combination of absent BAEP neural components with preserved otoacoustic emissions and cochlear microphonic potential corresponds to a peculiar pattern of auditory dysfunction recently coined "auditory neuropathy'. All 4 children exhibited well-defined kernels at latencies consistent with the microphonic potential. These data indicate that the cochlea itself can generate kernels at a presynaptic level. They open up the question of the identification of the physiological site(s) responsible for the generation of MLS-evoked kernels.

Adolescent↗
PubMed1992

Effects of sample size on the latency and amplitude of the auditory evoked response.

Experiment I investigated the effects of sample size (500 to 1500 stimulus repetitions) on the auditory brainstem response as a function of intensity (20 to 80 dB nHL) on a group of 10 normally hearing subjects. There was little change in identifiability, reliability, latencies, or amplitudes of Waves I, III, and V as the sample size increased from 500 or 750 to 1500 repetitions. These results suggest that 500 to 750 repetitions may be adequate when methods similar to those in the present study are used, and that the common clinical practice of employing approximately 1500 repetitions may unnecessarily prolong testing. Experiment II employed 12 hearing-impaired subjects who were tested at 10 to 40 dB SL using sample sizes from 250 to 4500 stimulus repetitions. Identifiability of all waves increased as sample size increased from 250 to 4500 repetitions. The largest changes in identifiability occurred when sample size increased from 250 to 1500 or 3000 repetitions, with little improvement as sample size increased from 3000 to 4500 repetitions. Examiners should monitor averaged responses and terminate testing as soon as a wave is identified. Contrary to expectation, there was no systematic change in the standard error of measurement for latency (approximately 0.07 ms) as sample size increased from 250 to 4500 repetitions. The standard error of measurement for amplitude decreased from approximately 100 nV with 500 repetitions to approximately 45 nV at 3000 repetitions. The improvement in reliability with increasing sample size may be explained by a decrease in the variability of background noise. A systematic decrease in amplitude also was observed as sample size increased. This observation may be explained by a reduction in the residual noise levels or because of time jitter or adaptation within the auditory pathways. Nonetheless, investigators who wish to use ABR amplitude measures for diagnosis may benefit from using a relatively large sample size.

Adult↗
PubMedDate not supplied

[Spinocerebellar ataxias type 1 and 2: comparison of clinical, electrophysiological and magnetic resonance evaluation].

BACKGROUND AND PURPOSE: Spinocerebellar ataxias type 1 (SCA1) and type 2 (SCA2) belong to neurodegenerative disorders of autosomal dominant inheritance, genetically and clinically heterogeneous, caused by the expansion of CAG trinucleotides. Trunk and limb ataxia, dysarthria, dysphagia, gaze palsy, sensory and motor axonal neuropathy are the dominant features in both entities. The aim of the study was to evaluate the differences between genotype and phenotype based on clinical and electrophysiological assessment of the visual, auditory pathways, and EEG alterations in comparison with the cerebellar and brain atrophy in MRI. MATERIAL AND METHODS: 44 patients with SCA1 and 24 cases with SCA2 confirmed molecularly were examined neurologically and using the International Cooperative Ataxia Rating Scale (ICARS). A correlation of clinical symptoms and signs, and CAG repeat numbers with EEG, visual (VEP) and brainstem auditory (BAEP) evoked potentials, and MRI alterations were evaluated. RESULTS: A statistically significant negative correlation between the age of disease onset and number of CAG repeats in both types of SCA was found. Examined patients with SCA2 were younger, with longer disease duration and more pronounced cerebellar and brain atrophy in MRI. We found a significant correlation between ICARS and CAG repeats in this group. The dysphagia, pyramidal tract involvement and depressive reaction were significantly frequent in SCA1 patients. However in SCA2 patients, the peripheral nerve damage and extrapyramidal signs were more prominent. The amplitude of P100 visual evoked potentials was significantly lower in SCA1 patients and negatively correlated with CAG repeats. CONCLUSIONS: These results provide further evidence for the phenotypic differences of genetically defined SCA1 and SCA2 patients, expressed by more frequent involvement of the pyramidal tract and depression reaction in SCA1, in contrast to peripheral nerve involvement and extrapyramidal signs in the clinical feature of SCA2 phenotype. Furthermore, atrophy of the brain and cerebellum revealed in MRI was more pronounced than electrophysiological functional alterations, especially in SCA2. The decreased amplitude of P100 VEP in SCA1 patients was the only electrophysiological parameter differentiating between both groups of patients.

Adult↗
PubMed1984

The central nucleus of the inferior colliculus in the cat.

The central nucleus of the inferior colliculus in the cat is distinguished by its unique neuropil. In Golgi-impregnated material, it is composed primarily of neurons with disc-shaped dendritic fields arranged into parallel arrays, or laminae, complemented by the laminar afferent axons from the lateral lemniscus. Large, medium-large, medium, and small varieties of disc-shaped cells are distinguished on the basis of the size of the dendritic field and cell body size, dendritic diameter, and dendritic appendages. A second major class of neurons in the central nucleus are the stellate cells with dichotomously branched, spherical-shaped dendritic trees. Simple, complex, and small stellate cells can be distinguished by their size and by the complexity of the dendritic and axonal branching. Laminar afferent axons are recognized by the nests of collateral side branches and the grapelike clusters of terminal boutons--thick, thin, and intermediate-sized varieties are apparent. Other axon types include local collaterals of central nucleus neurons, some of which are distinguished by their frequent and complex collaterals. In the central nucleus, the configuration of the fibrodendritic laminae, the presence of subdivisions, and the banding of afferent axons suggest levels of organization which are superimposed on the synaptic arrangements of the individual cell and axon types. The laminar pattern, as studied in serial Golgi-impregnated sections, differs from previous reports. The central nucleus contains subdivisions which can be distinguished by their laminar pattern, different proportions of cell types, and the packing density of the cell bodies and axonal plexus. The patterns of degeneration observed in Nauta-stained material after lesions of caudal auditory pathways show that thick and fine afferent fibers form dense bands of degeneration separated by sparse, fine-fiber degeneration. The bands are thicker than individual laminae but smaller than the subdivisions. The intrinsic organization of the neurons and axons, combined with the laminar organization, subdivisions, and banding patterns, each may contribute different aspects to the processing of auditory information in the central nucleus.

Animals↗
PubMed2003

Long-term outcome of neonatal hyperbilirubinaemia: subjective and objective audiological measures.

Neonatal hyperbilirubinaemia is a common cause of early onset sensorineural hearing loss. There is no exact method to detect the extent of the neurotoxicity of bilirubin. On the other hand, the auditory pathway is known to be one of the most sensitive parts of the central nervous system (CNS) to this toxic agent. This prospective follow-up study was performed to evaluate and compare the factors related to the hearing of neonates with severe hyperbilirubinaemia and an age-matched control group. Both of these groups were tested using auditory brainstem response (ABR) as well as evoked otoacoustic emissions. Additionally, both of these groups of children were evaluated subjectively using an early speech-language-communication evaluation questionnaire. There was no significant difference in either objective (ABR and evoked otoacoustic emission) or subjective assessment (questionnaire) between the study and control groups. Furthermore, no correlation between serum total bilirubin levels and ABR latencies or thresholds was found within the study group.

Brain Stem↗
PubMedDate not supplied

Somatosensory and brainstem auditory evoked potentials in alcoholic liver disease with and without encephalopathy.

Median somatosensory and brainstem auditory evoked potentials (SEP and BAEP) were studied in chronic alcoholics with and without complications of alcoholic liver disease. The alcoholics were divided into 4 groups: Group 1 with minimally abnormal liver function tests; Group 2 with hepatic failure; Group 3 with mild to moderate hepatic encephalopathy; and Group 4 with severe encephalopathy. A control group consisted of age-matched normal subjects. In the alcoholic groups, BAEPs showed a significant prolongation in the latencies of peaks III to VI and interpeaks I-III, III-V, and I-V. The peak latency prolongation was associated with a reduction in all peak amplitudes. In median SEPs, the cervical N13 and cortical N20 latencies were significantly delayed in the alcoholic groups. The amplitude of all cortical SEP components within 150 msec analysis time was also significantly reduced. In addition, the alcoholic groups had slowing in median nerve conduction and prolongation in central conduction time (N13 to N20 interpeak latency). In both BAEPs and SEPs, there were no differences in the peak amplitude and the peak latency among the alcoholic groups except for the late cortical SEP components which showed progressive prolongation and eventual absence from Groups 2 to 4. The present data indicate that chronic alcoholics have subclinical dysfunction in the central somatosensory and brainstem auditory pathways irrespective of the complications of alcoholic liver disease. However, the late components of the cortical SEPs can be affected in hepatic failure and hepatic encephalopathy.

Adult↗
PubMed2005

Information transmission defect identified and localized in language learning impaired children by means of electrophysiology.

Children with language processing deficits have various learning impairments and poor scholastic performance. In 3-10% of all children a specific language processing deficit can be identified by the Sound Connecting Sub-Test of the Illinois Test of Psycholinguistic-Abilities (SC-ITPA). These children among which we drew our index group (AS-Group) suffer from the disability to recognize isolated sounds as parts of words. Following linguistic terminology this is known as an auditory sequential sound processing deficit (ASSPD) Eighteen children (AS-Group) and 21 controls (C-Group) were subjected to mapped P300 evoked potential analyses of cortical response to acoustic stimulation in the oddball paradigm. The data presented here show that there exists significant relation between the P300 amplitude reduction and ASSPD. The P300 amplitude decrease measured in the AS-Group is due to a reduced information transmission in accordance with Johnson's Triarchic Model of the P300 Amplitude. The cerebral structures involved in poor language processing are localized at the left temporo-parietal cortex. This supports the hypothesis that the underlying neuronal defect of ASSPD is localized in the language center and not in the auditory pathway. The P300 amplitude may serve as electrophysiological tool to identify ASSPD and to quantify the degree of improvement in the course of specific therapy.

Auditory Perception↗
PubMedDate not supplied

Effect of anti-epileptic drug monotherapy and polypharmacy on visual and auditory evoked potentials.

Previous reports have suggested that some anticonvulsants may prolong somatosensory and auditory evoked potential latencies. We compared pattern-reversal visual and brainstem auditory evoked potentials in normal controls, patients on monotherapy, and patients taking polypharmacy. Visual evoked potential amplitudes were less in seizure patients, and P1 latencies were longer in epileptics on polypharmacy than controls. Absolute latencies of brainstem auditory evoked potentials were longer in polypharmacy patients than in controls or monotherapy patients. I-III, III-V, and I-V interpeak latencies were greater in polypharmacy patients than in those on monotherapy or controls. These findings suggest that anticonvulsants may affect conduction along visual and auditory pathways, and that antiepileptic drug polypharmacy and monotherapy may differ in their effects.

Adolescent↗
PubMed1987

Short-time course of adaptation pattern after noise exposure: electrophysiological studies in man.

Tone burst and click-evoked potentials were recorded in both humans and guinea pigs to determine whether responses associated with the cochlea and brainstem regions show a pattern of recovery from noise exposure similar to the polyphasic changes found for the pattern of early recovery from temporary threshold shift reported by Hirsh and Ward in 1952 [J. Acoust. Soc. Am. 24, p. 131]. During the 'post-stimulatory' phase following exposure for 5 min to broad-band noise at various intensity levels between 90 and 110 dB SPL, changes in amplitude and latency of the dominant complexes of the cortical and brainstem-evoked potentials were monitored for 5 min with 1.5- and 60-second time resolution. There was clear evidence of polyphasic processes at the cortical level, whereas in the brainstem region, large post-stimulatory amplitude shifts were generally accompanied by an asymptotic recovery. The relevance of the results to the different stations in the auditory pathway is evaluated by comparison with published electrophysiological data on activities at the different levels of the brainstem and the brain as reflected in evoked responses and single-unit recordings.

Adaptation, Physiological↗
PubMed1999

Lateralized auditory spatial perception and the contralaterality of cortical processing as studied with functional magnetic resonance imaging and magnetoencephalography.

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were used to study the relationships between lateralized auditory perception in humans and the contralaterality of processing in auditory cortex. Subjects listened to rapidly presented streams of short FM-sweep tone bursts to detect infrequent, slightly deviant tone bursts. The stimulus streams consisted of either monaural stimuli to one ear or the other or binaural stimuli with brief interaural onset delays. The onset delay gives the binaural sounds a lateralized auditory perception and is thought to be a key component of how our brains localize sounds in space. For the monaural stimuli, fMRI revealed a clear contralaterality in auditory cortex, with a contralaterality index (contralateral activity divided by the sum of contralateral and ipsilateral activity) of 67%. In contrast, the fMRI activations from the laterally perceived binaural stimuli indicated little or no contralaterality (index of 51%). The MEG recordings from the same subjects performing the same task converged qualitatively with the fMRI data, confirming a clear monaural contralaterality, with no contralaterality for the laterally perceived binaurals. However, the MEG monaural contralaterality (55%) was less than the fMRI and decreased across the several hundred millisecond poststimulus time period, going from 57% in the M50 latency range (20-70 ms) to 53% in the M200 range (170-250 ms). These data sets provide both quantification of the degree of contralaterality in the auditory pathways and insight into the locus and mechanism of the lateralized perception of spatially lateralized sounds.

Acoustic Stimulation↗
PubMed1997

Neural activity in the medial geniculate nucleus during auditory trace conditioning.

In classical trace conditioning the acquisition of a conditioned response (CR) is possible even though an interval (the trace interval) elapses between the conditioned stimulus (CS) and unconditioned stimulus (US). This implies that some neural representation of the CS (the stimulus trace) is able to support association between the two stimuli. The medial geniculate nucleus (MGN), particularly the medial division (mMGN), has been identified as one site in the auditory pathway where associative related changes in neural activity occur. If neurons in the MGN are involved in such a sensory trace and in acquisition of a CR, then it is expected that activity following an acoustic CS should be related to both stimulus and response. This study examined the extracellular activity of single units in the MGN during differential auditory trace conditioning of the rabbit nictitating membrane response (NMR). Two 150-ms tones (600 Hz and 1200 Hz) served as CS+ and CS-, and the US was periorbital electrostimulation. Changes in activity during the stimulus and trace interval were largest in the medial and dorsal MGN divisions on CS+ trials and on trials in which a CR was made. Examination of probe stimuli of short (50 ms) and long (600 ms) duration suggested that both CR latency and activity changes in the trace interval were related to stimulus duration and time-locked to stimulus offset. Comparisons of neural activity on the basis of fast or slow CR responses revealed different patterns of response--activity on fast CR trials was generally greater and tended to occur earlier. These results suggest that MGN neurons are involved in the maintenance of a sensory memory trace and possibly play a part in CR generation and timing.

Acoustic Stimulation↗
PubMed1995

The temporal relationship between the brainstem and primary cortical auditory evoked potentials.

Many methods are employed in order to define more precisely the generators of an evoked potential (EP) waveform. One technique is to compare the timing of an EP whose origin is well established with that of one whose origin is less certain. In the present article, the latency of the primary cortical auditory evoked potential (PCAEP) was compared to each of the seven subcomponents which compose the brainstem auditory evoked potential (BAEP). The data for this comparison was derived from a retrospective analysis of previous recordings of the PCAEP and BAEP. Central auditory conduction time (CACT) was calculated by subtracting the latency of the cochlear nucleus BAEP component (wave III) from that of the PCAEP. It was found that CACT in humans is 12 msec which is more than double that of central somatosensory conduction time. The interpeak latencies between BAEP waves V, VI, and VII and the PCAEP were also calculated. It was deduced that all three waves must have an origin rather more caudally within the central auditory system than is commonly supposed. In addition, it is demonstrated that the early components of the middle latency AEP (No and Na) largely reside within the time domain between the termination of the BAEP components and the PCAEP which would be consistent with their being far field reflections of midbrain and subcortical auditory activity. It is concluded that as the afferent volley ascends the central auditory pathways, it generates not a sequence of high frequency BAEP responses but rather a succession of slower post-synaptic waves. The only means of reconciling the timing of the BAEP waves with that of the PCAEP is to assume that the generation of all the BAEP components must be largely restricted to a quite confined region within the auditory nerve and the lower half of the pons.

Animals↗
PubMed1999

Cochlear implants and electrical brainstem stimulation in sensorineural hearing loss.

Cochlear implants and multichannel auditory brainstem implants enable patients with bilateral total or profound hearing loss to receive at least acoustic information. Both types of prosthesis are based on electrical stimulation of the auditory pathway. Different speech coding strategies and the number of electrodes used may influence the postoperative results. The preoperative evaluation of patients is of utmost importance. The cochlear implant is suitable for patients with hearing loss due to inner ear disorders, but who have functioning hearing nerve. Patients with a defect of the hearing nerve can be provided with an auditory brainstem implant.

Brain Stem↗
PubMedDate not supplied

Auditory brainstem potentials in uraemia.

Evoked response audiometry was carried out to assess the viability of the auditory pathway in haemodialysed patients. The latency of the waves III and V and I-V interpeak latencies were significantly longer in the renal patients compared to the control group. The I-V interpeak latency was longer in 8 of our 13 patients than the upper limit (4.38 ms) in our laboratory. The possible cause for the central auditory dysfunction may be multifactorial, including the effect of metastatic calcifications, repeated occurrence of disequilibrium syndrome, or some small, molecular, toxic, metabolic substance. The significance of the different factors may vary among different haemodialysis centres.

Adult↗
PubMed2001

Malnutrition and environmental stimulation in rats: interpeak intervals of the brainstem auditory evoked potentials.

The aim of this study was to investigate the effects of malnutrition, nutritional recovery, environmental stimulation and click intensity on the interpeak intervals of the waves of the Brainstem Auditory Evoked Potentials (BAEPs). The animals were divided into Well-nourished (W) and Malnourished (M) groups. At weaning, half of the M rats were submitted to nutritional recovery (R) until the test day. These groups were further subdivided into Stimulated (S) and Non-stimulated (N) rats. The BAEPs interpeak intervals I-III, I-IV and III-IV were analysed in independent groups of rats on the 18th, 22nd, 32nd and 42nd days of age. During the lactation period, stimulated rats presented shorter I-III, I-IV and III-IV interpeak intervals than Non-stimulated animals. This analysis also indicated a diet x stimulation x age interaction during the lactation period. The WN and MN groups showed a longer I-IV interval than the WS and MS groups, respectively, on the 18th and 22nd day of age, and the MN group also presented a longer I-IV interpeak interval than the WN group on the 22nd day of age. During the post-lactation period, stimulated animals showed shorter I-III and I-IV intervals than non-stimulated rats. Post hoc analysis indicated longer I-III and I-IV interpeak intervals in the MN than in the WN, RN and MS groups. Additionally, malnourished animals showed longer I-III and I-IV intervals than well-nourished and recovered rats when exposed to clicks of 90, 80 or 70 dB intensity. Malnutrition resulted in a delay of normal development of the brainstem auditory pathway indicated by the increases in the interpeak intervals of BAEPs waves, and environmental stimulation reduced these intervals, promoting faster nervous impulse transmission.

Acoustic Stimulation↗
PubMed1989

Brainstem auditory evoked potentials in patients with multi-infarct dementia and dementia of the Alzheimer type.

Brainstem auditory evoked potentials (BAEPs) were recorded in 25 patients with multi-infarct dementia (MID) (mean age 71.2 years), 16 patients with dementia of the Alzheimer type (DAT) (mean age 70.6 years), and 34 normal subjects (mean age 69.1 years). Both MID and DAT patients showed significant prolonged interpeak latencies between waves I and V (I-V IPLs) compared to normal subjects (p less than .001 and p less than .01, respectively). In patients with MID, both I-III IPLs and III-V IPLs were significantly longer than those of normal subjects (p less than .01 and p less than .01 respectively). On the other hand, only III-V IPLs were significantly prolonged in patients with DAT (p less than .01). There were no significant differences between MID and DAT with regard to any of the IPLs. Present results suggest that the brainstem lesions are located in the auditory pathways in patients with MID and DAT. However, with BAEP measurements, we were not able to discriminate between patients with MID and DAT.

Aged↗
PubMed1999

Central auditory speech test findings in individuals with subjective idiopathic tinnitus.

This study reports central auditory speech test performance of 25 consecutive patients with subjective idiopathic tinnitus of the severe disabling type. A preliminary study of 14 individuals who had subjective idiopathic tinnitus and complained of difficulty in hearing and understanding revealed a high incidence of abnormal central auditory speech test performance (71%), despite satisfactory peripheral hearing. The results (1) identify objectively for the first time that tinnitus affects specific components of the auditory pathway; (2) provide a basis for monitoring methods of tinnitus control; and (3) provide a basis for understanding "the interference effect" and problem of communication difficulties in patients with tinnitus of the severe disabling type.

Adult↗