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At least 1,765 records · Page 98Linked to original sources
PubMed2006

Neural correlates of coherent audiovisual motion perception.

Real-life moving objects are often detected by multisensory cues. We investigated the cortical activity associated with coherent visual motion perception in the presence of a stationary or moving auditory noise source using functional magnetic resonance imaging. Twelve subjects judged episodes of 5-s random-dot motion containing either no (0%) or abundant (16%) coherent direction information. Auditory noise was presented with the displayed visual motion that was moving in phase, was moving out-of-phase, or was stationary. Subjects judged whether visual coherent motion was present, and if so, whether the auditory noise source was moving in phase, was moving out-of-phase, or was not moving. Performance was greatest for a moving sound source that was in phase with the visual coherent dot motion compared with when it was in antiphase. A random-effects analysis revealed that auditory motion activated extended regions in both cerebral hemispheres in the superior temporal gyrus (STG), with a right-hemispheric preponderance. Combined audiovisual motion led to activation clusters in the STG, the supramarginal gyrus, the superior parietal lobule, and the cerebellum. The size of the activated regions was substantially larger than that evoked by either visual or auditory motion alone. The congruent audiovisual motion evoked the most extensive activation pattern, exhibiting several exclusively activated subregions.

Acoustic Stimulation↗
PubMed1978

Binaural analysis in the aging auditory system.

In a simulation of the "cocktail party" problem, subjects listened to recordings of a target voice, obscured by four background voices from adjacent locations in space. Listening conditions were either dichotic (with interaural directional cues preserved) or diotic (same input to both ears, directional cues removed). Elderly subjects were unable to use binaural directional cues as effectively as young subjects to improve intelligibility of the target voice. The results suggest that there is an age related deficit in the ability to perform the binaural signal analysis necessary to effectively separate speech signals from noise.

Adult↗
PubMed1983

Cerebral laterality and psychopathology: a review of dichotic listening studies.

Studies using dichotic listening tasks have reported findings suggestive of alterations of cerebral laterality in schizophrenia and affective disorders. In a review of these findings, an effort was made to take into account four factors: (1) type of dichotic listening task; (2) performance level; (3) clinical state of patients at the time of testing; (4) diagnostic subtype of patients. A convergence of evidence indicates that the last two factors are of major importance. Several studies have found a relationship between clinical state and dichotic ear asymmetry. Greater severity of illness in schizophrenic and depressed patients is associated with reduced laterality, and clinical remission is accompanied by a normalization of laterality. While thie relationship appears to hold for both verbal and nonverbal dichotic tasks in depressed patients, that is not the case for schizophrenic patients. Studies have also reported evidence of differences in dichotic ear asymmetry between diagnostic subtypes of schizophrenia (i.e., paranoid vs. nonparanoid patients) and affective disorders (i.e., bipolar vs. unipolar patients). This evidence suggests the existence of homogeneous subgroups with distinctive laterality patterns and clinical characteristics.

Auditory Perception↗
PubMed1996

Mismatch response of the human brain to changes in sound location.

WE investigated whether the enhanced negativity of the human event-related brain potential elicited by changes in auditory lateralization is due to a higher-order change-detection process or whether it can be explained exclusively in terms of selective sensory adaptation. Infrequent changes in lateralization of a repetitive standard tone, generated by changes in interaural time differences, elicited a frontocentrally distributed negative brain wave in the 100-250 ms range relative to stimulus onset. This brain wave was also elicited when possible sensory adaptation was prevented by controlling for the state of refractoriness of location-specific neurones. The results demonstrate that changes in lateralization elicit a genuine mismatch negativity (MMN), indicating the activity of an automatic higher-order change-detection process.

Adult↗
PubMed1998

Neuropsychological evidence of the functional integration of visual, auditory and proprioceptive spatial maps.

We infer the functional integration of the visual, auditory and proprioceptive spatial maps from the behaviour of a patient (G.A.) with left visual neglect, i.e. a derangement of visual space representation. G.A. was required to point manually to left, centre or right acoustic stimuli, under visual control or blindfolded, with the responding hand (left or right) located either on the left, centre or right space. G.A.'s manual pointing responses to left auditory stimuli were strongly influenced by the visual spatial information and by the proprioceptive spatial information related to the position of the responding effector. In the visual control condition, when the patient performed the task with the left effector located on the left, pointing responses to left auditory stimuli were shifted towards the right intact visual space. In contrast, when the visual spatial information was rendered less salient, i.e. in the blindfolded condition, and the effector was again located on the left, manual pointing responses were confined to the previously ignored left space. These findings are consistent with the view that the acoustic representation is modulated by the impaired visual representation and by the proprioceptive spatial map related to the position of the responding effector.

Acoustic Stimulation↗
PubMed1998

A distinct low-level mechanism for interaural timing analysis in human hearing.

The detection of phase or timing differences, and amplitude differences between the two ears are cues for the spatial analysis of sound by humans. Previous physiological and anatomical studies of animals suggest that phase and amplitude differences between the ears may depend on different pathways, though human psychophysical studies suggest that interaural phase and amplitude differences between the two ears may be coded in the same way. Here we describe detailed psychophysical analysis of a subject with multiple sclerosis affecting the brain stem. He has a complete deficit in the detection of phase between the ears with preserved detection of interaural amplitude. The results prove that a distinct mechanism exists in humans for interaural phase detection.

Acoustic Stimulation↗
PubMed1999

Selective interference reveals dissociation between auditory memory for location and pitch.

Effects of interfering task-irrelevant tones varying in location or pitch on auditory location and pitch n-back tasks were investigated to study whether there is segregation of spatial and non-spatial information processing in the auditory working memory. The subjects performed spatial and non-spatial auditory 1- and 2-back tasks with and without location or pitch interference. In the 1-back tasks, location but not pitch interference significantly impaired location task performance whereas pitch but not location interference disrupted pitch task performance. In the 2-back tasks, neither the location nor the pitch task performance was differentially disrupted by the distractors, suggesting that there is memory load-dependent segregation in the handling of location and pitch information in the neuronal networks engaged in auditory working memory.

Acoustic Stimulation↗
PubMed1999

Contrasting spatial hearing deficits in hemianopia and spatial neglect.

Spatial hearing deficits have been described in widely differing pathologies, including bilateral temporal or unilateral parietal lesions, hemispherectomy, spatial neglect and right-sided cortical lesions without neglect. However, the topography of spatial hearing deficits after cortical lesions is only poorly understood, unlike that of vision and touch. We investigated the auditory subjective straight ahead (SSA) with a new technique of binaural sound source simulation using broad-band single pulses which were filtered with head-related transfer functions and delivered with a 5 degree resolution over headphones in front space. Normal subjects showed quite accurate judgments of the SSA, with a small but significant shift to the left of centre (-1.7 degrees) in the horizontal plane. Hemineglect without a scotoma, produced a large ipsilesional deviation of the auditory SSA (+22 degrees), while two hemianopic subjects, both without neglect, showed the opposite deviation of their perceived auditory SSA towards their contralesional, blind hemifield (+10 vs -28 degrees). Two control patients with unilateral lesions, both without neglect and without hemianopia, produced normal judgments of their auditory SSA (-3.0 degrees, +3.8 degrees). These results suggest at least two contrasting influences on directional spatial hearing after unilateral cortical lesions: hemianopia vs hemispatial neglect. The results are interpreted in favour of multisensory convergence of visual and auditory information in directional spatial hearing.

Acoustic Stimulation↗
PubMed2000

Simultaneous bilateral mismatch response to right- but not leftward sound lateralization.

Magnetoencephalography (MEG) was used to compare mismatch responses between hemispheres to changes in sound-source direction. Sixteen adults listened passively to two types of complex non-language sounds presented in separate blocks with midline standards and right- and left-lateralized deviants. Mismatch dipole amplitudes were larger contra- than ipsilaterally to the deviants. Both hemispheres processed right deviants simultaneously, whereas to left deviants, the left dipole peaked 20 ms later than the right dipole. A second experiment using the same standards but midline spectral deviants showed no interhemispheric differences. Here mismatch latencies were about 60 ms longer than in the location mismatch experiment. This suggested both fast, contralaterally dominant location mismatch responses and facilitated detection of auditory spatial deviance in the right hemifield.

Acoustic Stimulation↗
PubMed2001

Temporal and spatial dependency of the ventriloquism effect.

The perception of the spatial location of an auditory stimulus can be captured by a spatially disparate visual stimulus, a phenomenon known as the ventriloquism effect. This study investigated the temporal and spatial dependency of this illusion. In the temporal domain, only disparities of 50-100 ms were perceived as simultaneous, and disparities where the visual stimulus occurred before the auditory stimulus were more effective in creating the illusion. In the spatial domain, the illusion was elicited most strongly at spatial disparities below spatial discrimination thresholds. There was also a significant interaction between temporal and spatial disparities. These results indicate that both temporal and spatial parameters are critical in the perception of real world objects in extrapersonal space.

Acoustic Stimulation↗
PubMed2001

Changes in acoustic features and their conjunctions are processed by separate neuronal populations.

We investigated the relationship between the neuronal populations involved in detecting change in two acoustic features and their conjunction. Equivalent current dipole (ECD) models of the magnetic mismatch negativity (MMNm) generators were calculated for infrequent changes in pitch, perceived sound source location, and the conjunction of these two features. All of these three changes elicited MMNms that were generated in the vicinity of auditory cortex. The location of the ECD best describing the MMNm to the conjunction deviant was anterior to those for the MMNm responses elicited by either one of the constituent features. The present data thus suggest that at least partially separate neuronal populations are involved in detecting change in acoustic features and feature conjunctions.

Adult↗
PubMed2001

Cerebral mechanisms underlying orienting of attention towards auditory frequency changes.

Brain mechanisms underlying detection of auditory frequency changes were studied with event-related potentials (ERPs) in 14 human subjects discriminating visual stimuli. Scalp-current density mapping revealed bilateral components of mismatch negativity (MMN) in frontal and auditory cortices. Deviance-related activations in frontal and temporal cortex began to be significant at 94 ms and 154 ms in the right hemisphere, and at 128 ms and 132 ms in the left hemisphere. The magnitude of MMN-neuroelectric currents from the left temporal cortex correlated significantly (r = -0.56, p < 0.05) with distraction caused by MMN-eliciting deviant tones. These results suggest a complex cerebral circuitry involved in frequency change detection and strongly support the role of this circuitry in driving attention involuntarily towards potentially relevant frequency changes in the acoustic environment.

Adult↗
PubMed2001

Transient spatial attention modulates distinct components of the auditory ERP.

We recorded ERPs to pairs of externally presented tones, T1 and T2, in the absence of attentional cues to determine whether attention is momentarily sustained at the location of a behaviourally relevant sound, and what effect this focusing of attention might have on the neural response to target stimuli. ERPs to T2 were more negative when the preceding T1 was presented on the same side of fixation than when T1 was presented on the opposite side of fixation. This negative difference consisted of an early, parietal phase and a later, frontocentral phase. These results confirm and extend previously reported effects of transient spatial attention on auditory ERPs, and they demonstrate that transient spatial attention has a distinct and robust effect on the early stages of stimulus processing in the auditory system.

Acoustic Stimulation↗
PubMed2002

Comparison of neural activity preceding reaches to auditory and visual stimuli in the parietal reach region.

We examined the responses of neurons in the parietal reach region (PRR) during reaches to the remembered locations of auditory or visual stimuli. We found that the firing rate of PRR neurons contained information about the location of auditory and visual stimuli. For neurons tested with visual stimuli, the amount of information remained constant throughout the task. In contrast, for neurons tested with auditory stimuli, the amount of target-location information increased as the trial evolved. During the reach period of the task, the amount of information that was carried by neurons tested with auditory stimuli was not statistically different from the amount carried by neurons tested with visual stimuli. We interpret these data to suggest that the type of information that PRR neurons encode evolves throughout a task.

Acoustic Stimulation↗
PubMed2002

Intrinsic optical signals from rat primary auditory cortex in response to sound stimuli presented to contralateral, ipsilateral and bilateral ears.

In the auditory cortex, primitive features of acoustic stimuli are represented for auditory scene analysis. A typical example of a feature representation is the tonotopic map, in which sound frequencies are spatially arranged in an orderly manner. Some neurons in the auditory cortex are sensitive to sound source location, which is another important feature for auditory scene analysis. In the present study, using the intrinsic optical imaging technique, we attempted to visualize the two-dimensional pattern of neuronal population responses in the primary auditory cortex of rats to pure tones presented at various frequencies and sound intensities. The observed arrangements of sound frequencies were consistent with those obtained by electrophysiological mapping, which indicates that our intrinsic optical recording can visualize populational responses of neurons. We also found different temporal patterns of intrinsic signals elicited in response to contralateral, ipsilateral, and bilateral ear stimulations. Finally we try to explain the observed differential time courses of intrinsic signal responses from the theoretical point of view on the conduction of neural activities, based on the so far anatomically identified neural pathways in the rodent auditory system.

Acoustic Stimulation↗
PubMed2002

Stepping out of the spotlight: MMN attenuation as a function of distance from the attended location.

In this report we present neurophysiological evidence that spatial separation between attended and unattended sound sources influences a listener's ability to register changes in sounds presented outside the focus of attention. Standard and deviant stimuli were presented at three azimuth locations. Participants were asked to press a key whenever they heard a deviant at a designated location. Mismatch negativity waves were generated for deviants at the attended location and were attenuated for deviants occurring 30 degrees away from the attended location. Mismatch negativities were not observed at distances of 60 degrees or more. The results are consistent with a spotlight model of auditory attention in which the processing of stimuli outside the attentional focus is attenuated as a function of increasing distance from the focus.

Acoustic Stimulation↗
PubMed2003

Task-dependent visual coding of sound position in visuospatial neglect patients.

Recent neurophysiological evidence has shown that sound position can be coded in multiple frames of reference in the animal brain (i.e. head-centred, eye-centred, or intermediate head/eye centred). Here, we provide evidence for multiple coding of sound positions in humans, by studying pointing to sounds in 14 right brain-damaged (RBD) patients with or without visual neglect (a visuospatial neurological disturbance typically affecting contralesional space). Patients were asked to indicate the position of free-field sounds, either with a hand-pointing or with a head-turning response. Pointing movements were performed either blindfolded or with eyes open, but no visual feedback was available about sound position or the motor response. All RBD patients showed some impairment in sound localisation, particularly for sounds towards the contralesional side. In addition, task-irrelevant vision was more detrimental for hand-pointing than head-turning responses, only for neglect patients. We propose that this finding reflects visual coding of sound position when the eyes are open, which extends the pathological visuospatial bias of neglect patients to sound localisation. Moreover, the absence of any modulatory effects of ambient vision when head-turning responses were adopted suggests task-dependent visual coding of sound position, in agreement with multiple frames of reference for sound localisation.

Aged↗
PubMed2003

The right supratemporal plane hears the distance of objects: neuromagnetic correlates of virtual reality.

The neural mechanisms of auditory distance perception, a function of great biological importance, are poorly understood. Where not overruled by conflicting factors such as echoes or visual input, sound intensity is perceived as conveying distance information. We recorded neuromagnetic responses to amplitude variations over both supratemporal planes, with and without auditory spatial simulations. In the absence of other cues for distance, including those provided by auditory virtual reality, amplitude changes elicited enhanced preattentive responses over the right temporal lobe, indicating hemispheric lateralization of the 'where' pathway in the human. Lesion studies in monkeys and humans have shown that the rostral part of the right superior temporal cortex contributes to spatial awareness in the visual domain. Our data indicate that the distance to a sound source is processed within the adjacent right auditory cortex, thus extending the recent model of a right-hemisphere temporal multisensory matrix that subserves the integration of space-related data across visual and auditory modalities.

Adult↗