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PubMed1988

The relation between lorazepam-induced auditory amnesia and auditory evoked potentials.

We conducted a placebo-controlled double-blind investigation in 15 normal volunteers to study the time course of amnesia to auditory stimulation produced by lorazepam. We also studied the relationship between auditory amnesia and auditory evoked potentials to determine if long-latency auditory evoked potentials (LLAEPs) could be utilized as electrophysiologic predictors of memory. Amnesia was produced by administration of 0.05 mg/kg lorazepam intravenously. To separate the changes in LLAEPs due to generalized sedation from those associated with amnestic properties of a drug, a third group of subjects given 1.5 mg/kg secobarbital was included. Observed frequency and duration of amnesia to auditory stimulation after lorazepam was 58% and 3 hours, respectively (mean values), with marked diminuition of antirecall effect at 120 minutes. Administration of lorazepam increased the latency and decreased the amplitude of N1 and P3 components of LLAEPs. These changes appeared to be a result of generalized sedation rather than the amnestic properties of the drug. We failed to find a definite relationship between amnesia and changes in LLAEPs. We conclude that P3 component of LLAEPs cannot be utilized as an electrophysiologic predictor of amnesia in humans.

Adult↗
PubMed1984

Auditory and non-auditory subcortical afferents to the inferior colliculus in the rat.

Afferent projections to the rat inferior colliculus (IC) were studied by using the method of retrograde transport of horseradish peroxidase (HRP). Microinjection of HRP revealed an ordery arrangement of fiber projections between the cochlear and the central nucleus of IC; it entails a reversal of the dorso-ventral nucleotopic organization. An indistinct dorso-lateral nucleotopic projection was found between the lateral superior olivary nucleus and the central nucleus. Small number of neurons in some brainstem non-auditory structures were always labeled: the parabrachial region of the midbrain lateral tegmentum, the pars lateralis of substantia nigra, dorsal part of the central gray matter at a caudal 2/3 level of IC, and deep layers of the superior colliculus, ipsilaterally, and the spinal trigeminal and posterior column nuclei, contralaterally. Small injection restricted within the external and pericentral nuclei (cortical zone) of IC resulted in a higher distribution ratio of labeled neurons in the non-auditory structures as compared with those in the central nucleus. On the other hand, the ratio in the brainstem auditory nuclei decreased definitely after HRP-injection within the cortical zone, with an exception of the ipsilateral central nucleus of IC which contained many labeled cells following the injections in the cortical zone. The present results suggest a dual function of the inferior colliculus. The central nucleus acts as a relay station in the main auditory system, while the cortical zone, with its converging auditory, visual and somatic inputs, may act as a subcortical integration center for acoustico-motor behavior.

Afferent Pathways↗
PubMed2007

Connections of functional areas in the mustached bat's auditory cortex with the auditory thalamus.

The auditory thalamus is the major target of the inferior colliculus and connects in turn with the auditory cortex. In the mustached bat, biosonar information is represented according to frequency in the central nucleus of the inferior colliculus (ICc) but according to response type in the cortex. In addition, the cortex has multiple areas with neurons of similar response type compared to the single tonotopic representation in the ICc. To investigate whether these transformations occur at the level of the thalamus, we injected anatomical tracers into physiologically defined locations in the mustached bat's auditory cortex. Injections in areas used for target ranging labeled contiguous regions of the auditory thalamus rather than separate patches corresponding to regions that respond to the different harmonic frequencies used for ranging. Injections in the two largest ranging areas produced labeling in separate locations. These results indicate that the thalamus is organized according to response type rather than frequency and that multiple mappings of response types exist. Injections in areas used for target detection labeled thalamic regions that were largely separate from those that interconnect with ranging areas. However, injections in an area used for determining target velocity overlapped with the areas connected to ranging areas and areas involved in target detection. Thus, separation by functional type and multiplication of areas with similar response type occurs by the thalamic level, but connections with the cortex segregate the functional types more completely than occurs in the thalamus.

Acoustic Stimulation↗
PubMed1999

Do auditory responses recorded from awake animals reflect the anatomical parcellation of the auditory thalamus?

Previous studies performed in anesthetized animals have shown differences between the acoustic responses of neurons recorded from the different divisions of the medial geniculate body (MGB). This study aimed at determining whether or not such differences are also expressed when neurons are recorded from awake animals. The auditory responses of 130 neurons of the auditory thalamus were determined in awake, restrained guinea pigs while the state of vigilance of the animals was continuously monitored. There were significantly more 'on' phasic evoked responses and significantly fewer 'non-responsive' or 'labile' cells in the ventral division of the MGB (MGv) than in the other divisions. The response latencies and the variability of the latencies were smaller in the MGv than in the other divisions. The tuning of the neurons obtained from MGv and from the lateral part of the posterior complex were significantly sharper than those coming from the dorsal division of the MGB and the medial division. The mean threshold and the percentage of monotonic vs. non-monotonic intensity functions were not different in the subdivisions of the auditory thalamus. When compared with previous studies, the quantifications of the acoustic responses obtained in the present study gave values that differed from those reported under deep anesthesia, but were close to those reported under light anesthesia. Lastly, even if none of the physiological characteristic makes it possible, by itself, to determine the locus of recordings in the auditory thalamus, we conclude that the physiological characteristics of the evoked responses obtained in MGv differ from those of other divisions.

Acoustic Stimulation↗
PubMed1999

Auditory associative cortex dysfunction in children with autism: evidence from late auditory evoked potentials (N1 wave-T complex).

OBJECTIVES: Auditory processing at the cortical level was investigated with late auditory evoked potentials (N1 wave-T complex) in 4-8-year-old autistic children with mental retardation and compared to both age-matched normal and mentally retarded children (16 children in each group). METHODS: Two negative peaks which occurred in the 80-200 ms latency range were analyzed according to stimulus intensity level (50 to 80 dB SPL): the first culminated at fronto-central sites (N1b) and the second at bitemporal sites (N1c, equivalent to Tb of the T complex). The latter wave was the most prominent and reliable response in normal children at this age. RESULTS: Our results in autistic children indicated abnormalities of this wave with markedly smaller amplitude at bitemporal sites and pronounced peak latency delay (around 20 ms). Moreover, in both reference groups the intensity effect was found on both sides whereas in autistic children it was absent on the left side but present on the right. CONCLUSION: These findings in autistic children showing very disturbed verbal communication argue for dysfunction in brain areas involved in N1c generation i.e., the auditory associative cortex in the lateral part of the superior temporal gyrus, with more specific left side defects when auditory stimulus have to be processed.

Acoustic Stimulation↗
PubMed1990

Cells in the rat auditory system have sensory-delay correlates during the performance of an auditory working memory task.

Single unit activity was recorded from rat auditory cortex (AC), medial geniculate body (MGB), and inferior colliculus (IC) during performance of a continuous nonmatching-to-sample task. The rats made go and no-go responses to indicate whether the current tone was the same as (match) or different from (nonmatch) the preceding tone. Between 31% and 55% of the units from AC, MGB, and IC showed sensory correlates (differences in activity to the two types of tones), indicating an involvement in sensory discrimination. Twenty percent of the units from AC and MGB had delay correlates (sustained differential activity during the delay immediately after the tones), indicating an involvement in retention. Most of the units with delay correlates also had sensory correlates. These results suggest that the auditory system, especially AC and MGB, discriminates and retains auditory stimuli in an auditory working memory.

Animals↗
PubMed2000

Auditory agnosia restricted to environmental sounds following cortical deafness and generalized auditory agnosia.

We encountered a case of auditory agnosia restricted to environmental sounds, which was associated with the development of bilateral subcortical lesions after suffering a bilateral putaminal hemorrhage. The patient had a history of a putaminal hemorrhage on her left side without any major disability. Three years later, she suffered a putaminal hemorrhage on the other side. The clinical picture started with cortical deafness, then changed to generalized auditory agnosia for verbal and environmental sounds, and finally developed into auditory agnosia confined to the perception of environmental sounds. Her errors in a test of sound recognition were discriminative rather than associative in nature. Neuro-radiological examinations revealed bilateral subcortical lesions involving the fibers from the medial geniculate body to the temporal lobes after bilateral putaminal hemorrhage. This case suggested that the subcortical lesion involving bilateral acoustic radiation could cause either cortical deafness, auditory agnosia of all sounds, or auditory agnosia restricted to environmental sounds.

Agnosia↗
PubMed1991

Value of intraoperative brainstem auditory evoked potential monitoring in reducing the auditory morbidity associated with microvascular decompression of cranial nerves.

The present study was performed to determine whether the intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) during microvascular decompression operations is effective in preventing profound hearing loss or deafness in the ipsilateral ear. The authors retrospectively compared the auditory morbidity of posterior fossa microvascular decompression surgery for the treatment of tic douloureux and hemifacial spasm before and after the introduction of routine intraoperative BAEP monitoring in 1984. Each patient underwent a similar procedure performed by the same surgeon. The two patient groups were comparable with regard to age, sex, and indications for surgery, Auditory morbidity did not decline with the increasing experience of the surgeon prior to 1984; 10 (6.6%) of 152 primary operations (151 patients) in which monitoring was not performed were followed by a profound ipsilateral hearing loss or deafness. In the monitored group, none of 109 operations (104 patients) caused profound hearing loss or deafness. This significant decline in auditory morbidity is attributed by the authors to the use of intraoperative BAEP monitoring, which allows the surgeon to alter the operation in response to degradations in the wave patterns. Based on our experience and that of others, we believe that intraoperative BAEP monitoring is of value in reducing the auditory morbidity of posterior fossa microvascular decompression surgery.

Journal Article↗
PubMed2005

Auditory-visual speech perception and auditory-visual enhancement in normal-hearing younger and older adults.

OBJECTIVE: The purpose of the present study was to examine the effects of age on the ability to benefit from combining auditory and visual speech information, relative to listening or speechreading alone. In addition, the study was designed to compare visual enhancement (VE) and auditory enhancement (AE) for consonants, words, and sentences in older and younger adults. DESIGN: Forty-four older adults and 38 younger adults with clinically normal thresholds for frequencies of 4 kHz and below were asked to identify vowel-consonant-vowels (VCVs), words in a carrier phrase, and semantically meaningful sentences in auditory-only (A), visual-only (V), and auditory-visual (AV) conditions. All stimuli were presented in a background of 20-talker babble, and signal-to-babble ratios were set individually for each participant and each stimulus type to produce approximately 50% correct in the A condition. RESULTS: For all three types of stimuli, older and younger adults obtained similar scores for the A condition, indicating that the procedure for individually adjusting signal-to-babble ratios was successful at equating A scores for the two age groups. Older adults, however, had significantly poorer performance than younger adults in the AV and V modalities. Analyses of both AE and VE indicated no age differences in the ability to benefit from combining auditory and visual speech signals after controlling for age differences in the V condition. Correlations between scores for the three types of stimuli (consonants, words, and sentences) indicated moderate correlations in the V condition but small correlations for AV, AE, and VE. CONCLUSIONS: Overall, the findings suggest that the poorer performance of older adults in the AV condition was a result of reduced speechreading abilities rather than a consequence of impaired integration capacities. The pattern of correlations across the three stimulus types indicates some overlap in the mechanisms mediating AV perception of words and sentences and that these mechanisms are largely independent from those used for AV perception of consonants.

Acoustic Stimulation↗
PubMedDate not supplied

Auditory brainstem response in auditory assessment of acute severely burned children.

The burn population often requires ototoxic drugs in the treatment of infection. Previous investigations indicate that cochlear damage and auditory impairment may result from this medical therapy. In recent years, the auditory brainstem response (ABR) has assumed an important role in pediatric auditory assessment. We describe a test protocol for ABR assessment in the severely burned child. In a series of 69 acute severely burned children, 13% showed evidence of auditory deficit by the ABR. Based on our experiences, we recommend the inclusion of routine auditory evaluations, including ABR, in the diagnosis and rehabilitation of these children.

Adolescent↗
PubMed1979

Auditory evoked potentials and auditory behavior following prenatal and perinatal asphyxia in rhesus monkeys.

Two types of asphyxia were studied in monkeys, total asphyxia during mid-pregnancy (94--98 days gestation) and combined partial and total axphyxia at term (165 days gestation). Auditory evoked potentials and the acquisition of 2 auditory discrimination tasks were studied in asphyxiated animals as well as in group of controls. The brains of all asphyxiates were examined histologically. No auditory discrimination deficit was found in the asphyxiated animals; however, the auditory evoked potentials differentiated between control and asphyxiated animals, especially those with verified inferior colliculus damage.

Animals↗
PubMed1988

Contra- and ipsilateral auditory stimuli produce different activation patterns at the human auditory cortex. A neuromagnetic study.

Auditory evoked magnetic fields were recorded over the right hemisphere of healthy humans. The stimuli were noise bursts presented either to the contra- (C) or ipsilateral (I) ear in different combinations. The largest deflection of the responses, N100m (magnetic counterpart of electric N100), showed a field pattern which suggests activation of the supratemporal auditory cortex. In an oddball paradigm, where the standards (90%) were 400-ms noise bursts presented to the contralateral ear, and the deviants (10%) similar stimuli to the ipsilateral ear, the deviants elicited on the average 130% stronger equivalent dipoles for N100m than standards. Contralateral standards did not substantially decrease the response amplitude of ipsilateral deviants as compared with the response amplitude to ipsilateral stimuli alone presented at the interstimulus interval of the deviants. When two 50 ms noise bursts, separated by 310 ms, were presented once every 2 s, N100m evoked by the second stimulus of the pair was smaller when the stimuli were presented monaurally (C-C or I-I) than to different ears (I-C or C-I). The results suggest that contra- and ipsilateral auditory stimuli are analyzed, at least in part, in different neural networks at the human auditory cortex.

Acoustic Stimulation↗
PubMed1975

Albinism and auditory function in the laboratory mouse. I. Effects of single-gene substitutions on auditory physiology, audiogenic seizures, and developmental processes.

The effects of single-gene albino (c/c) mutations on auditory behavior and physiology were examined in congenic C57BL/6J mice. At 16 days of age, the c gene was additively associated with both reduced auditory functioning and lower body weight: 16-day-old c/c mice had higher auditory evoked potential (AEP) thresholds than +/c mice, which, in turn, had higher thresholds than +/+ mice; +/c mice were also intermediate with regard to body weight. Since these differences had nearly disappeared by 21 days of age, it was concluded that the c genes worked in an additive fashion to delay development during the period previously (Henry, 1967) found critical for inducing susceptibility to audiogenic seizures. At 16 days of age, albino mice (c/c) displayed susceptibility to audiogenic seizures, but nonalbino genotypes (+/c and +/+) were immune to the convulsive effects of sound. This behavior appeared to be a recessive trait at this age. But 5 days later, the behavioral phenotype exhibited incomplete dominance, with the +/c genotype displaying audiogenic seizures intermediate to those seen in the susceptible c/c and the nonsusceptible +/+ genotypes. These behaviors were compared to the thresholds and peak-to-peak amplitudes of the AEP, as seen in the input-output functions. It is suggested that differential development of the auditory systems in these genotypes is causally related to susceptibility to audiogenic seizures.

Acoustic Stimulation↗
PubMed1982

Scalp distribution of human auditory evoked potentials. II. Evidence for overlapping sources and involvement of auditory cortex.

The scalp distributions of human auditory evoked potentials (AEPs) between 20 and 250 msec were investigated using non-cephalic reference recordings. AEPs to binaural click stimuli were recorded simultaneously from 20 scalp locations over the right hemisphere in 11 subjects. Computer-generated isovoltage topographic maps at high temporal resolution were used to assess the stability of AEP scalp distributions over time and relate them to major peaks in the AEP wave forms. For potentials between 20 and 60 msec, the results demonstrate a stable scalp distribution of dipolar form that is consistent with sources in primary auditory cortex on the superior temporal plant near the temporoparietal junction. For potentials between 60 and 250 msec, the results demonstrate changes in AEP morphology across electrode locations and changes in scalp distribution over time that lead to two major conclusions. First, AEPs in this latency period are generated by multiple sources which partially overlap in time. Second, one or more regions of auditory cortex contribute significantly to AEPs in this period. Additional data are needed to determine the relative contribution of auditory cortex sources on the superior temporal plane and the lateral temporal surface and to identify AEP sources outside the temporal lobe.

Auditory Cortex↗
PubMed1996

Involvement of the caudal striatum in auditory processing: c-fos response to cortical application of picrotoxin and to auditory stimulation.

The topographical organization of corticostriatal connections have been postulated to follow a longitudinal pattern, each cortical area projecting on a longitudinal strip stretching along the whole rostro-caudal axis of the striatum. However, compared to the rostral striatal region, the caudal striatum exhibits distinct features in terms of connectivity and neuronal phenotype. The induction of c-fos expression in the striatum by cortical activation or sensory stimulation may throw more light on these functional corticostriatal relationships. In the present study, we examined the effects of cortical activation by local application of picrotoxin on the Fos-immunoreactivity (Fos-IR) in the striatum of the mouse, with special reference to the caudal part of the striatum. Activation of the auditory cortex induced a dense ipsilateral Fos-IR restricted to the caudal striatum i.e., in the caudo-medial striatum and in the caudal part of fundus striati, and a very sparse labelling in the medial region of the rostral striatum. Conversely, activation of both sensori-motor and visual cortices only resulted in Fos-IR in the main rostral part of the striatum, without response in the caudal extremity of the striatum. On the other hand, visual or auditory stimulation in awake animals failed to induce c-fos expression in the striatum. However, using quantitative in-situ hybridization for c-fos mRNA, we found that auditory, but not visual stimulation significantly potentiated the c-fos response to the D1 agonist SKF 38393 (2 mg/kg, i.p.) in the caudal part of the striatum. These functional observations suggest that, despite a more widespread cortico-striatal connection pattern deduced from tracing experiments, the strongest functional projections from the auditory system mainly converge onto a restricted part of the caudal striatum, according to a connection pattern that is reminiscent of the transverse segmentation proposed in early lesioning studies of corticostriatal projections.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1987

The human auditory brain stem as a generator of auditory evoked potentials.

Data on the size, location, and orientation of human brain stem auditory nuclei are discussed here from the point of view of the potential role of these structures in generation of the brain stem auditory evoked response. Due to reduction in size of several nuclei in the human brain stem, the structures most likely to be generators of far-field potentials are the cochlear nuclei, medial olivary nuclei, dorsal lemniscal nuclei, inferior colliculi, and their axonal projections. Consideration of the anatomy of the human auditory brain stem pathway forms the basis for a model of generation of auditory evoked potentials.

Animals↗
PubMed2004

Activation of the primary and association auditory cortex by the transition of sound intensity: a new method for functional examination of the auditory cortex in humans.

During functional MRI image acquisition, the scanning equipment generates substantial auditory noise, the effects of which are usually ignored. To investigate the neural activity in response to the transition of noise, we measured cerebral responses to short silent periods (1 and 5 s) during which the slice readout gradients were switched off. In all 15 normal volunteers, the 1 s silence bilaterally activated the primary and association auditory cortex. Subtraction of the response to the 1 s silent period from that to the 5 s silent period revealed the activation related to the onset (transition of sound from OFF to ON) event, indicating that the 1 s response is offset (transition of sound from ON to OFF) related. The complex response of the auditory cortex to the transition of the noise should be considered in designing functional MRI with auditory tasks.

Acoustic Stimulation↗
PubMed2003

Functional segregation of the temporal lobes into highly differentiated subsystems for auditory perception: an auditory rapid event-related fMRI-task.

With this study, we explored the blood oxygen level-dependent responses within the temporal lobe to short auditory stimuli of different classes. To address this issue, we performed an attentive listening event-related fMRI study, where subjects were required to concentrate during the presentation of different types of stimuli. Because the order of stimuli was randomized and not predictable for the subject, the observed differences between the stimuli types were interpreted as an automatic effect and were not affected by attention. We used three types of stimuli: tones, sounds of animals and instruments, and words. We found in all cases bilateral activations of the primary and secondary auditory cortex. The strength and lateralization depended on the type of stimulus. The tone trials led to the weakest and smallest activations. The perception of sounds increased the activated network bilaterally into the superior temporal sulcus mainly on the right and the perception of words led to the highest activation within the left superior temporal sulcus as well as in left inferior frontal gyrus. Within the left temporal sulcus, we were able to distinguish between different subsystems, showing an extending activation from posterior to anterior for speech and speechlike information. Whereas posterior parts were involved in analyzing the complex auditory structure of sounds and speech, the middle and anterior parts responded strongest only in the perception of speech. In summary, a functional segregation of the temporal lobes into several subsystems responsible for auditory processing was visible. A lateralization for verbal stimuli to the left and sounds to the right was already detectable when short stimuli were used.

Acoustic Stimulation↗