Auditory findings in brain stem disorders.
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Adolescent↗
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Results for “Auditory Perception”
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Changes in loudness after stapedectomy.
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Acoustic Stimulation↗
Acoustic reflex threshold measurement in hearing aid selection.
Aided speech discrimination scores were obtained for 18 patients with sensorineural hearing loss. Monosyllabic word discrimination lists with a competing message of connected discourse at a signal-to-noise ratio of +10 dB were used as the test stimuli, and measurements were made at four hearing aid gain settings for each subject. One of the gain settings was determined by measuring the acoustic reflex threshold for filtered noise in the ear contralateral to the aided ear. Two other settings were at +/- 10 dB relative to the reflex threshold gain setting; the fourth setting was determined with a traditional approach. Mean speech discrimination scores were highest at the reflex threshold gain setting and similar at the other three settings.
Acoustic Stimulation↗
Audiotympanometric findings in myasthenia gravis.
Myasthenia gravis can be a difficult diagnostic and therapeutic problem. Our study on six patients consisted of pure-tone audiograms, tympanometry, and acoustic reflex tests. Positive findings in the myasthenia gravis patients prior to medication included hyperacusis and increase in the intensity of sound required to elicit an acoustic reflex. Following medication, the hyperacusis lessened and the intensity of sound required to elicit the acoustic reflex decreased. During follow-up of two of the patients we encountered cholinergic (overdosage) crisis in one patient and myasthenic (underdosage) crisis in the other patient. Muscle weakness can be a common factor in both conditions. The acoustic reflex test can differentiate between the two types of crises. We believe audiotympanometric tests can aid in diagnosis and treatment of myasthenia gravis patients.
Acoustic Stimulation↗
Middle component averaged electroencephalic responses to tonal stimuli from normal neonates. Initial report.
Tone-pips, centered at 1,000 Hz, were used to elicit middle component averaged electroencephalic responses (AERs) (8 to 90 ms) from five normal neonates. The stimuli were presented monaurally at 10-, 30-, and 50-dB HL, with regard to adult behavioral thresholds. Averaged electroencephalic responses were also derived for no-stimulus control conditions. The initial portion of the stimulus-elicited AER waveforms was similar to that obtained from adults. An objective, scoring procedure, based on predetermined rules, was used to determine peak latencies and to quantify point-to-point amplitudes. Inspection of the scored data revealed that latencies decreased and amplitudes increased as the stimulus magnitude increased, as has also been reported for adults. Unlike adult responses, the middle components from the neonates in this study were identifiable only when recorded from the side of the head ipsilateral to the ear stimulated.
Auditory Perception↗
Auditory brainstem response and behavioral audiometry. Developmental correlates.
Development correlates of auditory brainstem evoked responses (ABRs) and behavioral audiometry in a total of 112 normal subjects consisting of 78 infants (age, 1 to 18 months), 24 children (age, 2 to 5 years), and ten adults (age, 18 to 22 years) were studied to provide normative data for audiological and neurological applications. Thresholds of ABR, as determined by minimum stimulus intensities evoking wave V, decreased with age. Neonates had the highest ABR thresholds, and adults had the lowest. A similar pattern was observed for behavioral sensitivity as that for the ABR thresholds. Response functions determined by both methods converged with age. They crossed between the ages of 2 and 3 years. There was a trend for all peak latencies to decrease with age. This effect was particularly pronounced for the later ABR components.
Acoustic Stimulation↗
Effect of peripheral hearing loss on the masking level difference.
The effects of both symmetric and asymmetric peripheral hearing loss on the masking level difference (MLD) at 500 Hz were studied in 651 subjects with conductive or sensorineural hearing loss and 270 normal controls. The data supported the hypothesis that the modification in MLD due to peripheral hearing loss results from deterioration in threshold in the antiphasic condition. These results provide correction factors for the normal MLD range as functions of boundary frequency of sensorineural loss above 500 Hz and degree of both symmetric and asymmetric sensitivity loss at 500 Hz in both subjects with conductive hearing loss and those with sensorineural hearing loss.
Adolescent↗
Learning disability in children with postmeningitic cochlear implants.
OBJECTIVE: To determine the effects of learning disability on measures of auditory perception, receptive language development, and sequential organization in children with postmeningitic cochlear implants. DESIGN: Retrospective study. Follow-up ranged from 12 months to 7 years. SETTING: Tertiary care center. PATIENTS: Ten pediatric patients with cochlear implants, 5 with documented learning disability. MAIN OUTCOME MEASURE: Pediatric cochlear implant test battery performance. RESULTS: Children with learning disability showed slower progress, more inconsistencies, and lower test scores than their partners without learning disability. CONCLUSION: Learning disability is not a contraindication to cochlear implantation, but preoperative counseling must be available to families and support personnel about preoperative achievements and expectation for these children.
Child↗
Delineation of single-word semantic comprehension deficits in aphasia, with anatomical correlation.
In 3 of 18 aphasic patients pure deficits in semantic comprehension at the single-word level were defined through a series of tasks that excluded possible confounding deficits in auditory perception, visual perception, or speech production. In these pure cases, deficits were found at the superordinate, equivalence, and subordinate levels of single-word semantic processing. Pure semantic deficits were found to be correlated with damage to the left posterior temporal and inferior parietal region; patients whose damage spared this area did not evince such deficits, and the converse was also true. This study confirms the existence of separable deficits in semantic comprehension and points conclusively to the left posterior temporal and inferior parietal region as being critical for semantic processing. This anatomical localization is in keeping with anatomical studies from nonhuman primates, suggesting that these regions may be concerned with multimodal processing and integration of language.
Aphasia↗
Effects of restricted cochlear lesions in adult cats on the frequency organization of the inferior colliculus.
Restricted cochlear lesions in adult animals result in plastic changes in the representation of the lesioned cochlea, and thus in the frequency map, in the contralateral auditory cortex and thalamus. To examine the contribution of subthalamic changes to this reorganization, the effects of unilateral mechanical cochlear lesions on the frequency organization of the central nucleus of the inferior colliculus (ICC) were examined in adult cats. Lesions typically resulted in a broad high-frequency hearing loss extending from a frequency in the range 15-22 kHz. After recovery periods of 2.5-18 months, the frequency organization of ICC contralateral to the lesioned cochlea was determined separately for the onset and late components of multiunit responses to tone-burst stimuli. For the late response component in all but one penetration through the ICC, and for the onset response component in more than half of the penetrations, changes in frequency organization in the lesion projection zone were explicable as the residue of prelesion responses. In half of the penetrations exhibiting nonresidue type changes in onset-response frequency organization, the changes appeared to reflect the unmasking of normally inhibited inputs. In the other half it was unclear whether the changes reflected unmasking or a dynamic process of reorganization. Thus, most of the observed changes were explicable as passive consequences of the lesion, and there was limited evidence for plasticity in the ICC. The implications of the data with respect to the primary locus of the changes and to the manner in which they contribute to thalamocortical reorganization are considered.
Acoustic Stimulation↗
Functional organization and hemispheric comparison of primary auditory cortex in the common marmoset (Callithrix jacchus).
Hemispheric fine-grain maps of primary auditory cortex (AI) were derived from microelectrode penetrations in the temporal gyrus of the common marmoset (Callithrix jacchus) to 1) compare the functional organization of AI in the marmoset with other mammalian species and 2) compare the right and left AI maps in individual monkeys. Frequency receptive fields (FRFs) were recorded with pure tones. Five FRF parameters were analyzed: characteristic frequency, threshold, sharpness of tuning 10 dB and 40 dB above threshold, and minimum response latency. The present study confirms that the functional organization of AI is characterized by a robust tonotopic frequency gradient overlaid with spatially clustered distributions of other FRF parameters. Globally, this functional organization of AI in the common marmoset is similar to that in other mammalian species. With respect to within-subject hemispheric comparisons of the five FRF parameters, a coherent pattern of asymmetry is not evident in marmoset AI. The overall results indicate that the basic functional organization between hemispheres is similar but not identical.
Acoustic Stimulation↗
Localization of sound after section of the brachium of the inferior colliculus.
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Animals↗
Inferior colliculus of the house mouse. I. A quantitative study of tonotopic organization, frequency representation, and tone-threshold distribution.
Electrophysiological mapping was used to study frequency representation in the inferior colliculus (IC) of the mouse. In the lateral nucleus (LN) only part of the frequency range of hearing was represented and tonotopicity was separate from that in the rest of the IC. Highest frequencies occupied the medial part (M) of the central nucleus (CN). A single complete representation of the hearing range was present only if representations in the dorsal cortex (plus dorsomedial nucleus) and CN (including M) were combined. Continuous isofrequency planes making up these nuclei (without the lateral part of the CN) were reconstructed. They tilted from medial to lateral and from caudal to rostral. The steepness of the slopes increased from caudal to rostral and from dorsal to ventral (i.e., with increasing frequency). Isofrequency planes had similar angles of deviation from the horizontal plane as described for dendritic laminae in the CN. Differences of mapping in the lateral part of the CN from that in the rest of the CN could be explained by the different organization of laminae in this part. The relative amounts of IC depth and volume occupied by parts of the mouse audible frequency range were quantified. Frequency representation along IC depth was not proportional to that along cochlear length. Compared with the relative density of afferent nerve fiber supply within given frequency ranges represented along the basilar membrane, there is a relative under-representation in the IC up to 15-20 kHz and an over-representation of higher frequencies. Highest absolute tone sensitivity (lowest threshold) was found in neurons forming a column (running perpendicular to isofrequency planes) in the center of the IC. Results are discussed with regard to frequency representation, intrinsic neuronal organization, and functional segregation in the IC of mammals.
Animals↗
The very distal part of the basilar papilla in the chicken: a morphological approach.
The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.
Animals↗
Alarm call responsivity of mallard ducklings: I. The acoustical boundary between behavioral inhibition and excitation.
Mallard (Anas platyrhychos) maternal assembly calls have fast repetition rates (notes/sec), which promote behavioral excitation in ducklings (i.e., vocalizing, approaching). On the other hand, maternal alarm calls have slow repetition rates, which promote behavioral inhibition (i.e., cessation of vocalizations, "freezing"). This study assesses the nature of the acoustical boundary separating these 2 behavioral states. Maternally naive ducklings were tested to 1 of 2 series of altered alarm calls that either increased or decreased in repetition rate every minute by 2/10 sec. Ducklings in control groups were exposed to a constant repetition rate for comparable periods of time. The inhibitory and disinhibitory responses of ducklings revealed that a relatively sharp acoustical boundary between inhibitory and excitatory repetition rates exists around 2.6 to 2.8 notes/sec. This transitional region happens to coincide with the range within which neither maternal assembly nor maternal alarm calls occur. Thus, there is a genuine match along this acoustical dimension between auditory perception of ducklings and the 2 major species-typical vocalizations of mallards.
Animals↗
Developmental changes in chickens' masked thresholds.
Masked thresholds were estimated at four frequencies (.25, .5, 1, and 2 kHz) in three levels of broadband noise (approximately 0, 10, and 20 dB/Hz) in over 100 chickens at 0 and 4 days of age. An adaptive procedure was based on delays in ongoing peeps that occurred when chicks heard the tones over the background noise. Masked thresholds decreased an average of 1 dB per day immediately after birth. This increasing sensitivity is more likely due to nonsensory factors, similar to distraction masking reported in human neonates, than to improving frequency resolution. Masked thresholds in these neonates are otherwise affected by spectrum level and frequency in the same way as the responses of mature subjects: thresholds increase by nearly 1 dB for each dB of increase in the spectrum level of the masker, and by approximately 3 dB for each octave of frequency. Thus, although elevated by some nonsensory effect, masked thresholds in newborn chicks are similar to those in humans.
Animals↗
Assessing the influence of scanner background noise on auditory processing. I. An fMRI study comparing three experimental designs with varying degrees of scanner noise.
We compared two experimental designs aimed at minimizing the influence of scanner background noise (SBN) on functional MRI (fMRI) of auditory processes with one conventional fMRI design. Ten subjects listened to a series of four one-syllable words and had to decide whether two of the words were identical. This was contrasted with a no-stimulus control condition. All three experimental designs had a duration of approximately 17 min: 1) a behavior interleaved gradients (BIG; Eden et al. [1999] J Magn Reson Imaging 41:13-20) design (repetition time, TR, = 6 s), where stimuli were presented during the SBN-free periods between clustered volume acquisitions (CVA); 2) a sparse temporal sampling technique (STsamp; e.g., Gaab et al., [2003] Neuroimage 19:1417-1426) acquiring only one set of slices following each of the stimulations with a 16-s TR and jittered delay times between stimulus offset and image acquisition; and 3) an event-related design with continuous scanning (ERcont) using the stimulation design of STsamp but with a 2-s TR. The results demonstrated increased signal within Heschl's gyrus for the STsamp and BIG-CVA design in comparison to ERcont as well as differences in the overall functional anatomy among the designs. The possibility to obtain a time course of activation as well as the full recovery of the stimulus- and SBN-induced hemodynamic response function signal and lack of signal suppression from SBN during the STsamp design makes this technique a powerful approach for conducting auditory experiments using fMRI. Practical strengths and limitations of the three auditory acquisition paradigms are discussed.
Acoustic Stimulation↗
Hippocampal-dependent memory is impaired in heterozygous GAP-43 knockout mice.
Cajal proposed that the rearrangement and growth of neurites and synaptic terminals is a substrate for the formation and storage of long-term memories. Proteins that regulate this learning-dependent growth are therefore likely to be "core determinants" (Sanes and Lichtman, Nat Neurosci 1999; 2:597-604) of such information storage processes. Although the growth-associated, protein kinase C (PKC) substrate GAP-43 has been oft-implicated in synaptic plasticity and memory, it has never been demonstrated that a reduction in the level of this protein has a deleterious effect on memory, because most homozygotes die perinatally. In this report, we observe significant memory impairments in heterozygous GAP-43 knockout mice with GAP-43 levels reduced by one-half. Impaired memory for a context was demonstrated in contextual fear conditioning. Importantly, no significant impairments in cued conditioning or on tests of nociceptive or auditory perception were observed in the heterozygous knockout, indicating that the observed impairments were unlikely related to performance or acquisition factors and are the result of reduced GAP-43 levels in the hippocampus. The present results, taken together with the prior demonstration of enhanced memory in transgenic mice overexpressing GAP-43, provide strong evidence for a pivotal role of hippocampal GAP-43 in the bidirectional regulation of mnemonic processing.
Amygdala↗