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At least 415 records · Page 23Linked to original sources
PubMed1987

The maturation of the central auditory conduction in preterm infants until three months post term. IV. Composite group averages of the cortical auditory evoked responses (ACRs).

Composite group averages were constructed from cortical auditory evoked responses (ACRs), which are recorded sequentially at maximally 8 conceptional age levels in 5 groups of 49 preterm infants, with additional inclusion of the records of 16 prematures obtained at different conceptional age levels. The group averages for the 5 gestational age groups showed replicable waveforms at all conceptional age (CA) levels reflecting the intragroup stability of the ACR complex. From the earliest age levels, from 25 weeks CA on, ACR group averages can be obtained, containing relative low voltage fast waves and high voltage slow waves. The most outstanding developmental changes in the ACR complex are the waveform changes. Until about 36 weeks CA a premature waveform is found, followed by a transitional phase with low voltage noisy records. Finally the adult waveform is found in the measurements at three months after term date. The latency values of the group averages are determined by the waveform changes. Persistent amplitude differences are found for the slow late waves between the vertex and the central temporal derivations.

Cerebral Cortex↗
PubMed2003

Prediction of auditory spatial acuity from neural images on the owl's auditory space map.

The owl can discriminate changes in the location of sound sources as small as 3 degrees and can aim its head to within 2 degrees of a source. A typical neuron in its midbrain space map has a spatial receptive field that spans 40 degrees--a width that is many times the behavioural threshold. Here we have quantitatively examined the relationship between neuronal activity and perceptual acuity in the auditory space map in the barn owl midbrain. By analysing changes in firing rate resulting from small changes of stimulus azimuth, we show that most neurons can reliably signal changes in source location that are smaller than the behavioural threshold. Each source is represented in the space map by a focus of activity in a population of neurons. Displacement of the source causes the pattern of activity in this population to change. We show that this change predicts the owl's ability to detect a change in source location.

Acoustic Stimulation↗
PubMed1985

Speech processing in the auditory system. I: The representation of speech sounds in the responses of the auditory nerve.

In a previous paper the speech evoked spatio-temporal response patterns recorded in large populations of auditory-nerve fibers in the cat were examined [M.I. Miller and M.B. Sachs, J. Acoust. Soc. Am. 74, 502-517 (1983)]. The distribution of the relative phases of synchronized activity emerges as an important response feature reflecting the stimulus spectral parameters. Specifically, each strong low-order harmonic of the stimulus (less than or equal to 1.5-2 kHz) dominates the synchrony of a relatively broad segment of fibers near its corresponding characteristic frequency (CF) location in a pattern which mirrors the underlying traveling wave component. Each such fiber segment can be roughly subdivided into two regions: (1) a region basal to the point of resonance of the harmonic where the fiber PST histograms accumulate only small delays (or phase shifts) relative to each other reflecting the fast speed of propagation of the traveling wave, and (2) a region at or very near the point of resonance where the responses exhibit drastic relative phase shifts owing to the sudden slow down of the traveling wave and the consequent rapid accumulation of phase shifts. These rapid phase shifts thus manifest themselves as steep and localized spatial discontinuities in an otherwise relatively uniform instantaneous pattern of activity across the fiber array, all occurring at the CF locations corresponding to the low-order harmonics of the stimulus.

Acoustic Stimulation↗
PubMed1985

Speech processing in the auditory system. II: Lateral inhibition and the central processing of speech evoked activity in the auditory nerve.

A biologically realistic model of a uniform lateral inhibitory network (LIN) is shown capable of extracting from the complex spatio-temporal firing patterns of the cat's auditory nerve the formants and low-order harmonics of synthetic voiced speech stimuli. The model provides a realistic mechanism to utilize the temporal aspects of the firing and thus supports the hypothesis that the neural coding of complex sounds in terms of average rates can be supplemented by the information coded in the synchronous firing. At low levels of intensity the LIN can sharpen the average rate profiles. At moderate and high levels the LIN uses the cues available in the distribution of phases of the synchronous activity which exhibit rapid relative phase shifts at specific characteristic frequency (CF) locations (corresponding to the frequencies of the low-order harmonics in the stimulus). These temporal phase shifts manifest themselves at the input of the LIN as steep and localized spatial discontinuities in the instantaneous pattern of activity across the fiber array. The LIN enhances its output from these spatially steep input regions while suppressing its output from spatially smooth input regions (where little phase shifts occur). In this manner the LIN recreates from the response patterns a representation of the stimulus spectrum using the temporal cues as spatial markers of the stimulus components rather than as absolute measures of their frequencies. Similar results are obtained with various lateral inhibitory topologies, e.g., recurrent versus nonrecurrent, single versus double layer, and linear versus nonlinear.

Animals↗
PubMed2005

Auditory responses in the cochlear nucleus of awake mustached bats: precursors to spectral integration in the auditory midbrain.

In the cochlear nucleus (CN) of awake mustached bats, single- and two-tone stimuli were used to examine how responses in major CN subdivisions contribute to spectrotemporal integrative features in the inferior colliculus (IC). Across CN subdivisions, the proportional representation of frequencies differed. A striking result was the substantial number of units tuned to frequencies <23 kHz. Across frequency bands, temporal response patterns, latency, and spontaneous discharge differed. For example, the 23- to 30-kHz representation, which comprises the fundamental of the sonar call, had an unusually high proportion of units with onset responses (39%) and low spontaneous rates (53%). Units tuned to 58-59 kHz, corresponding to the sharply tuned cochlear resonance, had slightly but significantly longer latencies than other bands. In units tuned to frequencies >30 kHz, 31% displayed a secondary excitatory peak, usually between 10 and 22 kHz. The secondary peak may originate in cochlear mechanisms for some units, but in others it may result from convergent input onto CN neurons. In 20% of units tested with two-tone stimuli, suppression of best frequency (BF) responses was tuned at least an octave below BF. These properties may underlie similar IC responses. However, other forms of spectral interaction present in IC were absent in CN: we found no facilitatory combination-sensitive interactions and very few combination-sensitive inhibitory interactions of the dominant IC type in which inhibition was tuned to 23-30 kHz. Such interactions arise above CN. Distinct forms of spectral integration thus originate at different levels of the ascending auditory pathway.

Acoustic Stimulation↗
PubMed1988

Neurophysiological aspects of auditory hallucinations. 99mTc-(HMPAO)-SPECT investigations in patients with auditory hallucinations and normal controls--a preliminary report.

In a symptom-oriented study 17 patients suffering from chronic auditory hallucinations were investigated by means of 99mTc-HMPAO-SPECT and compared with healthy controls. The results confirm the relative frontal hypoactivity in junction with a relative hyperactivity in the basal ganglia and mesial limbic structures in both hemispheres found in a previous pilot study in auditorily hallucinating patients. Our results should fortify the symptom-oriented approach in psychiatric research.

Adult↗
PubMed1986

Control of auditory hallucinations through occlusion of monaural auditory input.

A schizophrenic patient whose severe level of auditory hallucinations had proved refractory to neuroleptic medication was given two treatment techniques derived from Green's theory that hallucinations represent verbal activity in the non-dominant hemisphere. Voice activity was markedly reduced in frequency and severity over a six-month period, and led to general improvements in interpersonal functioning. There was evidence for independent and additive effects of the two techniques.

Adult↗
PubMed1983

Auditory brain stem responses and cortical auditory-evoked potentials in difficult-to-test children.

Brain-stem-evoked responses (BERs) and cortical auditory-evoked potentials (AEP) were recorded in 24 children showing severe behavioral disorders. BER testing always requires sedation if not general anesthesia. This allowed us to perform precise acoustic impedance measurements, and thus to find 3 glue ears. The electrophysiological tests revealed whether there was sensorineural deafness, which was cared for if necessary. Finally, when the BERs were normal, we evaluated the modifications in the cortical AEP, in relation to a clinical classification closely related to that of the DSM III of the American Academy of Psychiatry.

Adolescent↗
PubMed1982

Comparison between intracranially recorded potentials from the human auditory nerve and scalp recorded auditory brainstem responses (ABR).

Recordings from the intracranial part of the auditory nerve in patients undergoing operations for cranial nerve disorders show that the compound action potential of the nerve in response to tonebursts has a latency that matches the N2P2N3 complex of potentials recorded from the scalp using mastoid-vertex electrodes. The results indicate that the audiotory nerve gives rise to two of the peaks in the scalp-recorded potentials and not, as was earlier assumed, to only the first peak in the scalp-recorded ABR. Recordings from two locations on the nerve show identical waveshapes of the compound action potential and a difference in latency that can be accounted for by the conduction time of nerve.

Action Potentials↗
PubMed1986

The central auditory conduction at term date and three months after birth. II. Auditory brainstem response.

This communication describes the results of auditory brainstem responses (ABRs) obtained in 25 healthy mature newborns with a follow-up at 3 months of age. The combination of ipsi- and contralateral recordings, the intensity series and the comparison with the composite group averages are useful for the identification of the separate ABR components. Differences between the records after right or left ear stimulation were not observed. Comparing our data with those obtained by others, we conclude that the interpeak latency differences (IPLDs) offer a more consistent measure of ABR latency values than the peak latencies measured from stimulus onset. The simultaneously recorded ABRs ipsi- and contralateral to stimulation show both at term, and at 3 months, an equal central conduction time. The ABR II-V complex shows contralaterally a significant shift compared with the ipsilateral II-V complex. The significant latency changes observed between term and at 3 months are due mainly to the latency decrease in the II-III IPLD.

Age Factors↗
PubMed1989

[Estimation of surviving auditory nerve by electrically evoked auditory brainstem response (FABR)--comparison between extra-cochlear stimulation and intra-cochlear stimulation].

This study investigated the possibility of using electrically evoked auditory brainstem response (EABR) for predicting surviving spiral ganglion cell populations. EABR recordings were made from six kanamycin induced deaf cats by the round window monopolar stimulation (RW) and the scala tympani bipolar stimulation (ST). On completing the electrical stimulation, each animal was sacrificed and prepared for histological examination. The spiral ganglion cell populations were estimated by classifying them into four groups (0-25%, 25-50%, 50-75%, 75-100%) as a percentage of survival cells under magnification. EABR thresholds and input-output function of amplitude were compared with microscopic findings of surviving spiral ganglion cell populations. The results were as follows: 1) The rate of amplitude growth in response to increased stimulus intensity of electrically evoked potentials from ST was gradual, but that of RW was steep. 2) The vestibular potentials were elicited by RW, and at a lower stimulus intensity the RW waveform began to become distorted by the myogenic potentials. 3) EABR threshold was a poor predictor of surviving spiral ganglion cell populations. 4) There was a correlation between surviving spiral ganglion cell populations and the slope of the input-output functions of ST EABR. However, there was no correlation between that of RW EABR and the slope.

Animals↗
PubMed1990

[Clinical and electrophysiological investigations of hearing in neonates. I. Behavioral audiometry and auditory brainstem response in evaluation of the auditory apparatus in pre- and full-term neonates].

Auditory Brain stem Responses (ABRs) and behavioural thresholds were studied in 130 neonates born between 25 to 42 weeks of gestational age. ABR thresholds were determined by the weakest stimulus that elicited a recognizable and replicable wave V. Behavioural audiometric thresholds for 1 and 2 kHz pure tones were determined by taking the lowest of threshold for eliciting auro-palpebral reflex. In 130 tested neonates ABR responses were normal in 102 (78.5%) while 28 babies (21.5%) elicited a pathological response. In the normal ABR group mean thresholds values ranged between 24.7-35 dBHL, and it was observed that the thresholds diminished with neonatal maturation. Behavioural audiometry disclosed that 77.5% normal full-term neonates responded to pure tone 1000 Hz, with mean threshold of 92.83 dBHL, while only 59.09% of pre-term neonates responded to pure tone stimuli at 101 dBHL.

Audiometry↗
PubMed1979

Dynamic auditory localization: systematic replication of the auditory velocity function.

Two experiments explored the capability of normal-hearing adults to judge the apparent velocity of an unseen moving sound source. In exper. I, 9 naive and, 1 experienced S judged the velocity of a moving source emitting a .5-kc/s tone at 50 db SPL. S's head was in the center of a circle of 1.88-m radius swept by a small loudspeaker. In exper. II the sound was a low-pass-filtered (0.1-1 kc/s) noise at 50 db sound spectrum level. In both experiments perceived velocity was directly proportional to the actual velocity of the source. These results support out initial observations (Waugh et al, J. Aud. Res., 1979, 19, 103-1 10) that auditory velocity discrimination can be described as a power function with an exponent of 1.0. In exper. II the Ss also varied the sound source velocity by means of a variable resistor to produce a perceived velocity of 100 degrees/sec. Performance on the adaptive velocity production task was successfully predicted from the data of the absolute velocity judgment task. The Weber fraction was .052 for relatively fast-moving sound sources (100 degrees/sec). The ability to discriminate sound source velocity appears to be a well-defined feature of the dynamic binaural spatial system.

Audiometry↗
PubMed1989

[Development of the auditory threshold during the first months of life related to modifications of the physiology of the external auditory canal].

A study realised among 60 children by means of a probe tube microphone allowed us to determine the mean ear canal resonance by the newborn and the young children. This is noticeably less than the adult one. The ear canal reaches its adult physiology after one year, so it implies a somewhat different auditory sensibility by the newborns than by the adults, particularly in the 2000-4000 Hz range. We suggest that the A.B.R. wave I latency and thresholds modifications during children's first year of life are (at least partially and in the majority of cases) an ear canal physiological variation effect and that different calibrations should be used for newborns screening test and for adults purposes.

Aging↗
PubMed1983

Song structure without auditory feedback: emendations of the auditory template hypothesis.

Motor patterns of songs of swamp and song sparrows, Melospiza georgiana and M. melodia, deafened early in life display a significant degree of species-specific structure. Normal songs of the two species differ in the degree to which they are segmented. Swamp sparrow song consists of a single segment, and song sparrow songs are multisegmental. Song and swamp sparrows were deafened at 17 to 23 days, prior to the onset of song or subsong. The song sparrows developed more segments in their singing than the swamp sparrows. Species-specific trends were also evident in song durations and frequency characteristics. Abnormalities were found, however, in the morphology of the notes and syllables from which songs of early deafened sparrows are constructed. These results require emendation of the auditory template hypothesis of song learning in birds.

Animals↗
PubMedDate not supplied

[The plastic reorganization of the neuronal receptive fields of the auditory cortex and medial geniculate body evoked by microstimulation of the auditory cortex].

The effects of intracortical microstimulation (ICMS) on receptive fields (RFs) of simultaneously recorded auditory cortex (A1) and medial geniculate body (MGB) neurons were examined in rats under ketamine. Three types of neurons were distinguished according to the configuration of their RFs: mono-, be-, and polymodal. It was shown that RFs of adjacent neurons may be different and Rfs of distant (up to 1 mm in rostro-caudal direction) neurons may be similar. ICMS was able to produce changes in RF structure of A1 neurons at and near the stimulation side and also in homotopically related regions of MGB. RFs of homotopically related A1 and MGB neurons mostly changed in a similar way after ICMS. We suggest that the mechanism underlying the observed RF changes of A1 and MGB neurons in related to ICMS-induced long-term changes (LTP and LTD) in synaptic efficacy of the cortex-thalamus-cortex loop.

Acoustic Stimulation↗