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Results for “Auditory Perception”

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PubMed2003

Auditory-visual speech perception examined by fMRI and PET.

Cross-modal binding in auditory-visual speech perception was investigated by using the McGurk effect, a phenomenon in which hearing is altered by incongruent visual mouth movements. We used functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). In each experiment, the subjects were asked to identify spoken syllables ('ba', 'da', 'ga') presented auditorily, visually, or audiovisually (incongruent stimuli). For the auditory component of the stimuli, there were two conditions of intelligibility (High versus Low) as determined by the signal-to-noise (SN) ratio. The control task was visual talker identification of still faces. In the Low intelligibility condition in which the auditory component of the speech was harder to hear, the visual influence was much stronger. Brain imaging data showed bilateral activations specific to the unimodal auditory stimuli (in the temporal cortex) and visual stimuli (in the MT/V5). For the bimodal audiovisual stimuli, activation in the left temporal cortex extended more posteriorly toward the visual-specific area in the Low intelligibility condition. The direct comparison between the Low and High audiovisual conditions showed increased activations in the posterior part of the left superior temporal sulcus (STS), indicating its relationship with the stronger visual influence. It was discussed that this region is likely to be involved in cross-modal binding of auditory-visual speech.

Acoustic Stimulation↗

PubMed1992

Learning during general anaesthesia: implicit recall after methohexitone or propofol infusion.

Forty-four patients undergoing coronary artery surgery were allocated randomly to receive an infusion of propofol or methohexitone as a hypnotic supplement to a fentanyl-based anaesthetic technique. A taped message was played to the patients, consisting of 10 words associated with prompt sentences and a suggestion for a specific postoperative behavioural response. Twenty patients (10 propofol and 10 methohexitone) (perioperative group) were exposed to the taped message during surgery and in the immediate postoperative period and the other 24 patients (postoperative group) were exposed to the tape only in the postoperative period, after return to the intensive care unit (ICU). No patient had explicit recall of any events during the period when the tape was played. The patients in the propofol group who heard the tape during surgery had significant implicit recall of the word associations compared with the equivalent 10 methohexitone patients (P = 0.004), when tested 48 h after surgery. The patients who were played the tape whilst receiving identical infusion regimens for sedation in the ICU did not demonstrate implicit recall of the word associations in either the propofol or the methohexitone groups. There was no evidence of a response to the specific behavioural suggestion during the postoperative interview. The results confirm that auditory perception can occur during clinically adequate anaesthesia, and that suppression of auditory awareness or learning is a function of both the pharmacological degree of sedation and the degree of surgical stimulation.

Anesthesia, General↗

PubMed2001

Role of mammalian auditory cortex in the perception of elementary sound properties.

Studies in several mammalian species have demonstrated that bilateral ablations of the auditory cortex have little effect on simple sound intensity and frequency-based behaviors. In the rat, for example, early experiments have shown that auditory ablations result in virtually no effect on the rat's ability to either detect tones or discriminate frequencies. Such lesion experiments, however, typically examine an animal's performance some time after recovery from ablation surgery. As such, they demonstrate that the cortex is not essential for simple auditory behaviors in the long run. Our study further explores the role of cortex in basic auditory perception by examining whether the cortex is normally involved in these behaviors. In these experiments we reversibly inactivated the rat primary auditory cortex (AI) using the GABA agonist muscimol, while the animals performed a simple auditory task. At the same time we monitored the rat's auditory activity by recording auditory evoked potentials (AEP) from the cortical surface. In contrast to lesion studies, the rapid time course of these experimental conditions preclude reorganization of the auditory system that might otherwise compensate for the loss of cortical processing. Soon after bilateral muscimol application to their AI region, our rats exhibited an acute and profound inability to detect tones. After a few hours this state was followed by a gradual recovery of normal hearing, first of tone detection and, much later, of the ability to discriminate frequencies. Surface muscimol application, at the same time, drastically altered the normal rat AEP. Some of the normal AEP components vanished nearly instantaneously to unveil an underlying waveform, whose size was related to the severity of accompanying behavioral deficits. These results strongly suggest that the cortex is directly involved in basic acoustic processing. Along with observations from accompanying multiunit experiments that related the AEP to AI neuronal activity, our results suggest that a critical amount of activity in the auditory cortex is necessary for normal hearing. It is likely that the involvement of the cortex in simple auditory perceptions has hitherto not been clearly understood because of underlying recovery processes that, in the long-term, safeguard fundamental auditory abilities after cortical injury.

Animals↗

PubMed1998

Hyperalgesia or hypervigilance? An evoked potential approach to the study of fibromyalgia syndrome.

Past research on the phenomenon of enhanced pain sensitivity in fibromyalgia syndrome (FS) revealed evidence for both a higher pain magnitude in response to nociceptive stimuli (hyperalgesia) and a general perceptual amplification of sensations (hypervigilance). In order to distinguish between these two aspects of disturbed sensory processing in FS, cerebral evoked potentials after brief painful laser and auditory stimuli were measured in 10 FS patients. Results were compared with those from age-matched painfree controls. Amplitudes of middle-latency (N1) and long-latency (P2) laser evoked potentials (LEPs) were significantly higher in FS than in controls. Furthermore, laser intensity at pain but not at sensation threshold was lower in FS than in controls. However, auditory evoked potentials (AEPs) did not differ between groups. Enhanced N1 and P2 amplitudes of LEPs suggest stronger sensory and attentional processing of nociceptive information in FS, respectively. The concept of hypervigilance is challenged by the failure to find differences in auditory perception among FS and control patients. Yet, the importance of unpleasant intensities of auditory stimulation, not applied in this study, to reveal abnormal non-nociceptive perceptual amplification in FS is discussed.

Arousal↗

PubMed2004

Lateralization of ventral and dorsal auditory-language pathways in the human brain.

Recent electrophysiological investigations of the auditory system in primates along with functional neuroimaging studies of auditory perception in humans have suggested there are two pathways arising from the primary auditory cortex. In the primate brain, a 'ventral' pathway is thought to project anteriorly from the primary auditory cortex to prefrontal areas along the superior temporal gyrus while a separate 'dorsal' route connects these areas posteriorly via the inferior parietal lobe. We use diffusion MRI tractography, a noninvasive technique based on diffusion-weighted MRI, to investigate the possibility of a similar pattern of connectivity in the human brain for the first time. The dorsal pathway from Wernicke's area to Broca's area is shown to include the arcuate fasciculus and connectivity to Brodmann area 40, lateral superior temporal gyrus (LSTG), and lateral middle temporal gyrus. A ventral route between Wernicke's area and Broca's area is demonstrated that connects via the external capsule/uncinate fasciculus and the medial superior temporal gyrus. Ventral connections are also observed in the lateral superior and middle temporal gyri. The connections are stronger in the dominant hemisphere, in agreement with previous studies of functional lateralization of auditory-language processing.

Adult↗

PubMed2005

Electrophysiological and speech perception measures of auditory processing in experienced adult cochlear implant users.

OBJECTIVE: This study determined the relationship between auditory evoked potential measures and speech perception in experienced adult cochlear implant (CI) users and compared the CI evoked potential results to those of a group of age- and sex-matched control subjects. METHODS: CI subjects all used the Nucleus CI-22 implant. Middle latency response (MLR), obligatory cortical potentials (CAEP), mismatch negativity (MMN) and P3a auditory evoked potentials were recorded. Speech perception was evaluated using word and sentence tests. RESULTS: Duration of deafness correlated with speech scores with poor scores reflecting greater years of deafness. Na amplitude correlated negatively with duration of deafness, with small amplitudes reflecting greater duration of deafness. Overall, N1 amplitude was smaller in CI than control subjects. Earlier P2 latencies were associated with shorter durations of deafness and higher speech scores. In general, MMN was absent or degraded in CI subjects with poor speech scores. CONCLUSIONS: Auditory evoked potentials are related to speech perception ability and provide objective evidence of central auditory processing differences across experienced CI users. SIGNIFICANCE: Since auditory evoked potentials relate to CI performance, they may be a useful tool for objectively evaluating the efficacy of speech processing strategies and/or auditory training approaches in both adults and children with cochlear implants.

Acoustic Stimulation↗

PubMed2003

Extending the domain of center frequencies for the compressive gammachirp auditory filter.

The gammatone filter was imported from auditory physiology to provide a time-domain version of the roex auditory filter and enable the development of a realistic auditory filterbank for models of auditory perception [Patterson et al., J. Acoust. Soc. Am. 98, 1890-1894 (1995)]. The gammachirp auditory filter was developed to extend the domain of the gammatone auditory filter and simulate the changes in filter shape that occur with changes in stimulus level. Initially, the gammachirp filter was limited to center frequencies in the 2.0-kHz region where there were sufficient "notched-noise" masking data to define its parameters accurately. Recently, however, the range of the masking data has been extended in two massive studies. This paper reports how a compressive version of the gammachirp auditory filter was fitted to these new data sets to define the filter parameters over the extended frequency range. The results show that the shape of the filter can be specified for the entire domain of the data using just six constants (center frequencies from 0.25 to 6.0 kHz and levels from 30 to 80 dB SPL). The compressive, gammachirp auditory filter also has the advantage of being consistent with physiological studies of cochlear filtering insofar as the compression of the filter is mainly limited to the passband and the form of the chirp in the impulse response is largely independent of level.

Attention↗

PubMedDate not supplied

Locating voices in space: a perceptual model for auditory hallucinations?

INTRODUCTION: Auditory hallucinations are often perceived as being located in external auditory space ("outside the head"), like real auditory perceptions, but in the absence of a speaker or other external stimulus. METHOD: A selective literature review of the spatial phenomenology of auditory hallucinations and the cognitive neuroscience of locating real voices in external space was undertaken. An auditory-perceptual model of external auditory hallucinations was developed in healthy right-handed subjects using functional magnetic resonance imaging and the presentation of speech in virtual acoustic space. RESULTS: Karl Jaspers inextricably linked "reality" and "externality" of auditory hallucinations. Although these two properties do not always occur simultaneously in hallucinating patients, the issue of "externality" is important from both a clinical and neuroscientific perspective. In an auditory-perceptual model of auditory hallucinations, association cortex in the left planum temporale is critically involved in the perception of real voices as located in external space. Right-sided voice stimuli are associated with greater neural response in the dominant (left) auditory cortex than left-sided stimuli. Subjects are better at identifying the spatial location of voices presented on the right than on the left. CONCLUSION: The auditory-perceptual model described helps identify candidate brain systems likely to be involved in the pathogenesis of auditory hallucinations in schizophrenia, and is distinct from other models, which use concepts of "internal monitoring" and "inner speech". Its application, in the cognitive neuroscientific investigation of the phenomenology of auditory hallucinations, may shed further light on the mechanisms underlying this distressing experience.

Journal Article↗

PubMed1984

Consequences of auditory deprivation in animals and humans.

An electron microscopic study of the cerebral cortex of mutant deaf mice (Deol's dn gene) has shown differences in synaptic organisation between these mice and normally hearing ones. In the auditory cortex of the deaf mice, there are fewer synapses and these are larger than in the normally hearing, whereas there is no difference between these two categories in the visual cortex. These results are the reverse of those observed by other authors in the occipital cortex of rats raised in an enriched or impoverished environment. In humans, the functional consequences of early hearing loss have been investigated on moderately to severely deaf (60-80 db mean loss) youngsters, who have been tested for their capacity of categorical perception, auditory discrimination, and production of significant contrasts between stop consonants. Categorical perception was absent in all but one subject. Auditory discrimination was poor for both the voiced-voiceless contrast and the place of articulation contrast. In the production experiments, the subjects had greater difficulty in producing the voiced-voiceless than the place of articulation contrasts. The possible relevance of these animal and human studies to cochlear implantation is discussed.

Acoustic Stimulation↗

PubMed1999

Temporal and speech processing deficits in auditory neuropathy.

Auditory neuropathy affects the normal synchronous activity in the auditory nerve, without affecting the amplification function in the inner ear. Patients with auditory neuropathy often complain that they can hear sounds, but cannot understand speech. Here we report psychophysical tests indicating that these patients' poor speech recognition is due to a severe impairment in their temporal processing abilities. We also simulate this temporal processing impairment in normally hearing listeners and produce similar speech recognition deficits. This study demonstrates the importance of neural synchrony for auditory perceptions including speech recognition in humans. The results should contribute to better diagnosis and treatment of auditory neuropathy.

Acoustic Stimulation↗

PubMed2004

Sequential effects of increasing propofol sedation on frontal and temporal cortices as indexed by auditory event-related potentials.

BACKGROUND: It is an open question whether cognitive processes of auditory perception that are mediated by functionally different cortices exhibit the same sensitivity to sedation. The auditory event-related potentials P1, mismatch negativity (MMN), and early right anterior negativity (ERAN) originate from different cortical areas and reflect different stages of auditory processing. The P1 originates mainly from the primary auditory cortex. The MMN is generated in or in the close vicinity of the primary auditory cortex but is also dependent on frontal sources. The ERAN mainly originates from frontal generators. The purpose of the study was to investigate the effects of increasing propofol sedation on different stages of auditory processing as reflected in P1, MMN, and ERAN. METHODS: The P1, the MMN, and the ERAN were recorded preoperatively in 18 patients during four levels of anesthesia adjusted with target-controlled infusion: awake state (target concentration of propofol 0.0 microg/ml), light sedation (0.5 microg/ml), deep sedation (1.5 microg/ml), and unconsciousness (2.5-3.0 microg/ml). Simultaneously, propofol anesthesia was assessed using the Bispectral Index. RESULTS: Propofol sedation resulted in a progressive decrease in amplitudes and an increase of latencies with a similar pattern for MMN and ERAN. MMN and ERAN were elicited during sedation but were abolished during unconsciousness. In contrast, the amplitude of the P1 was unchanged by sedation but markedly decreased during unconsciousness. CONCLUSION: The results indicate differential effects of propofol sedation on cognitive functions that involve mainly the auditory cortices and cognitive functions that involve the frontal cortices.

Acoustic Stimulation↗

PubMed1965

AUDITORY NERVE: ELECTRICAL STIMULATION IN MAN.

Auditory perceptions produced in a person deaf to acoustic stimulation were studied by electrically exciting the auditory nerve through permanently implanted electrodes. Pulsed current as small as 1 microampere peak-to-peak could be perceived. Pitch, as reported by the subject, varied with electrode selection, current amplitude, and pulse repetition rate from about 70 to at least 300 pulses per second. Loudness increased with amplitude and duration of pulse stimuli, and to a lesser extent with repetition rate. The total range in amplitude of the stimulus, from threshold to an uncomfortable loudness, was 15 to 20 decibels. Simultaneous stimulation in separate electrodes produced a number of complex effects.

Acoustic Stimulation↗

PubMed2006

Auditory processing deficits in growth restricted fetuses affect later language development.

An increased risk for language deficits in infants born growth restricted has been reported in follow-up studies for more than 20 years, suggesting a relation between fetal auditory system development and later language learning. Work with animal models indicate that there are at least two ways in which growth restriction could affect the development of auditory perception in human fetuses: a delay in myelination or conduction and an increase in sensorineural threshold. Systematic study of auditory function in growth restricted human fetuses has not been reported. However, results of studies employing low-risk fetuses delivering as healthy full-term infants demonstrate that, by late gestation, the fetus can hear, sound properties modulate behavior, and sensory information is available from both inside (e.g., maternal vascular) and outside (e.g., noise, voices, music) of the maternal body. These data provide substantive evidence that the auditory system is functioning and that environmental sounds are available for shaping neural networks and laying the foundation for language acquisition before birth. We hypothesize that fetal growth restriction affects auditory system development, resulting in atypical auditory information processing in growth restricted fetuses compared to healthy, appropriately-grown-for-gestational-age fetuses. Speech perception that lays the foundation for later language competence will differ in growth restricted compared to normally grown fetuses and be associated with later language abilities.

Child↗

PubMed1997

Auditory event-related potentials in post- and prelingually deaf cochlear implant recipients.

The development of central auditory functions in cochlear implant (CI) patients was studied over six months of rehabilitation. Examinations were performed beginning with the first week after processor calibration, and in monthly follow-up sessions thereafter. The subjects were given a simple auditory perception task (detection of a 400 Hz and a 1450 Hz tone), as well as an oddball-paradigm (detection of one of the tones as a rare deviant). Auditory evoked potentials, reaction time and errors were recorded. Results from five patients, two postlingually deaf and three prelingually deaf CI recipients are shown. Generally, in the auditory evoked potentials of patients a shortening of N100 latency towards those of subjects with normal hearing was seen from month to month. However, in the prelingually deaf patients this effect was weaker and more variable over time. Three CI recipients showed a P300 component in the oddball-paradigm in correlation with their performance. Two prelingually deaf patients failed to show a P300 in the oddball-paradigm. For both components, the N100 and the P300 we found a larger spreading over the skull in the patients compared to a normal hearing person. The results show that from the very first days after initial processor fitting prelingually and postlingually deaf CI recipients may show cortical correlates of stimulus processing and discrimination. For some components of the auditory evoked potentials an initial temporal change but a maintained larger spreading over the skull was seen.

Cochlear Implantation↗

PubMed2003

The synergy between speech production and perception.

Speech intelligibility is known to be relatively unaffected by certain deformations of the acoustic spectrum. These include translations, stretching or contracting dilations, and shearing of the spectrum (represented along the logarithmic frequency axis). It is argued here that such robustness reflects a synergy between vocal production and auditory perception. Thus, on the one hand, it is shown that these spectral distortions are produced by common and unavoidable variations among different speakers pertaining to the length, cross-sectional profile, and losses of their vocal tracts. On the other hand, it is argued that these spectral changes leave the auditory cortical representation of the spectrum largely unchanged except for translations along one of its representational axes. These assertions are supported by analyses of production and perception models. On the production side, a simplified sinusoidal model of the vocal tract is developed which analytically relates a few "articulatory" parameters, such as the extent and location of the vocal tract constriction, to the spectral peaks of the acoustic spectra synthesized from it. The model is evaluated by comparing the identification of synthesized sustained vowels to labeled natural vowels extracted from the TIMIT corpus. On the perception side a "multiscale" model of sound processing is utilized to elucidate the effects of the deformations on the representation of the acoustic spectrum in the primary auditory cortex. Finally, the implications of these results for the perception of generally identifiable classes of sound sources beyond the specific case of speech and the vocal tract are discussed.

Auditory Cortex↗

PubMed1984

Functional properties of auditory-nerve fibers during postnatal development in the kitten.

The discharges of the auditory-nerve fibers were studied in kittens between 2-40 days of age. Up to the 10th postnatal day, fibers could be divided into two main categories: fibers with spontaneous activity (SA) that respond to sound and fibers without SA but with evoked responses. A third, smaller, category, fibers having neither SA nor evoked activity, was also present. The development of SA comprises two phases. The first, lasting from birth up to the third postnatal week, shows a relatively fast increase and the second, lasting up to adulthood, a slower increase. Typical tone burst responses can be recorded at the end of the first postnatal week. Thereafter reactivity steadily increases especially after the 10th postnatal day. In young animals, rate level function is characterized by a steep segment with a low dynamic range followed by a decrease in activity that lasts until the end of the second week. At this point adult-like functions may be observed, although maximal firing still increases for some weeks. Tuning curves and threshold sensitivity tend to develop inversely at corresponding frequencies. Fibers with low characteristic frequencies reach adult threshold before that of high frequency fibers and high frequency fibers reach adult tuning before low frequency fibers. A comparison of auditory-nerve fiber activity in kittens show that maturation of most functional characteristics lasts several weeks after birth and in some cases continues after the first postnatal month.

Action Potentials↗

PubMed1986

Auditory response properties of neurons in the claustrum and putamen of the cat.

The auditory response properties of single neurons in claustrum and putamen were studied in response to simple dichotic stimuli (viz. noise-and tone-bursts) in chloralose-anaesthetized cats. Neurons in claustrum were commonly weakly driven with long latency, were broadly tuned and were excited by stimulation of either ear (EE). Putamen neurons, in contrast, were securely driven with short latency, showed irregular tuning with a preference for low frequencies and were either EE or excited only by the contralateral ear (EO). The differences between claustrum and putamen responses can be related to differences in connections with the auditory cortical fields and with auditory thalamus. Some neurons were also tested for visual responsiveness: auditory and visual cells were intermingled in both nuclei and only a small percentage of cells were bimodal. In contrast to the visual and somatosensory input to claustrum, which are derived from primary cortical fields, the auditory input to claustrum is apparently derived from non-primary cortical regions, suggesting a fundamentally different role for processing of auditory information in claustrum.

Animals↗

PubMed1982

Cortical evoked potentials in response to brief modulation of signal amplitude. Experiments on auditory temporal resolution.

Human cortical evoked potentials were monitored with scalp electrodes as an indicator of the ability to resolve brief changes in an auditory signal. For a brief period in the middle of a noise pulse its intensity was increased or decreased. The magnitude and duration of this change was varied to establish (1) the threshold for the cortical evoked potential and (2) the effect on the evoked response (amplitude, latency) in the suprathreshold region. To evoke a stimulus-specific potential pattern, durations of about 16 ms were required for intensity changes of +3 dB. With an intensity step of +9 dB, the threshold duration was reduced to 4-6 ms. A brief increase in intensity was more associated with distinctly lower thresholds and larger response amplitudes than an equivalent reduction in intensity, duration being equal. These results confirm the critical durations found in psychoacoustic studies that offer valuable evidence as to the ability to resolve brief changes in an auditory signal.

Animals↗