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PubMed1995

Effects of eye position on auditory localization and neural representation of space in superior colliculus of cats.

The maps of visual and auditory space within the superior colliculus are in approximate register both with each other and with the underlying motor maps associated with orienting responses. The fact that eyes and ears can move independently poses a problem for the sensorimotor organization of these two modalities. By monitoring eye and pinna positions in alert, head-fixed cats, we showed that the accuracy of saccadic eye movements to auditory targets was little affected by eye eccentricity (range +/- 15 deg) at the onset of the sound. A possible neural basis for this behavioral compensation was suggested by recordings from superior colliculus neurons. The preferred sound directions of some neurons in the deep layers of this midbrain nucleus exhibited a shift with the direction of gaze, while in others the response throughout the auditory receptive field was either increased or decreased, suggesting that changes in eye position alter the gain of the auditory response.

Acoustic Stimulation↗
PubMed1978

Auditory spatial responses of young guinea pigs (Cavia porcellus) during and after ear blocking.

Newborn guinea pigs were tested to determine their ability to approach an auditory stimulus early in development. Observations of the behavior of 1-4-day-old animals in a circular eight-choice maze revealed a pronounced tendency to orient toward and approach a tape-recorded signal of guinea pig vocalizations. The occurrence of approach responses was reduced to chance in animals tested with one ear occluded by wax ear plugs which attenuated but did not totally eliminate sound. The effect of monaural ear blocks was more severe than binaural blocks, which reflects the importance of binaural cues in the maintenance of approach responses to sound. In a second study, the ability of older animals, 11-31 days of age, was examined. Directional approach responses to sound were also evident at this age, and ear plugs disrupted performance only under monaural conditions. Furthermore, in animals raised from birth with monaural ear blocks but tested without ear plugs, there was a subsequent disruption of performance for at least 21 days. These results indicate the importance of binaural cues in the development of early auditory spatial responses and suggest the need for appropriate binaural experience for subsequent localization of sounds.

Age Factors↗
PubMed2006

Three-dimensional localization of sperm whales using a single hydrophone.

A three-dimensional localization method for tracking sperm whales with as few as one sensor is demonstrated. Based on ray-trace acoustic propagation modeling, the technique exploits multipath arrival information from recorded sperm whale clicks and can account for waveguide propagation physics like interaction with range-dependent bathymetry and ray refraction. It also does not require ray identification (i.e., direct, surface reflected) while utilizing individual ray arrival information, simplifying automation efforts. The algorithm compares the arrival pattern from a sperm whale click to range-, depth-, and azimuth-dependent modeled arrival patterns in order to estimate whale location. With sufficient knowledge of azimuthally dependent bathymetry, a three-dimensional track of whale motion can be obtained using data from a single hydrophone. Tracking is demonstrated using data from acoustic recorders attached to fishing anchor lines off southeast Alaska as part of efforts to study sperm whale depredation of fishing operations. Several tracks of whale activity using real data from one or two hydrophones have been created, and three are provided to demonstrate the method, including one simultaneous visual and acoustic localization of a sperm whale actively clicking while surfaced. The tracks also suggest that whales' foraging is shallower in the presence of a longline haul than without.

Acoustics↗
PubMed1994

Intelligibility and localization of speech from virtual directions.

We studied the intelligibility of speech and the ability of listeners to localize speech when synthetic direction information was added to the signal. Masked thresholds for single synthesized words were measured for simulated, horizontal angular separations of speech in the presence of a masking noise. Speech recognition was measured using the Modified Rhyme Test; the masker was broad-band white noise. A single set of head-related transfer functions conditioned the speech and noise waveforms presented over headphones, and listeners were free to move their heads relative to the apparent directions of these signals. The masker was fixed at 0 deg, and when speech was presented from other azimuths, its intelligibility typically increased by 4 to 5 dB. Individuals' masked thresholds were variable yet repeatable, and the plot of threshold by azimuth seemed unique to each subject. In a separate test, the same listeners were asked to estimate the azimuth of items from the rhyme test. Localization was accurate and performance was similar to previous work, except that confusions of source locations in the front and rear hemispheres were evenly distributed across azimuth.

Adult↗
PubMed1985

Localization of pure tones and click trains by untrained humans.

Minimum audible angles (m.a.a.s) of untrained subjects were measured in a room using pure tone (0.5 to 8 kHz) and click train (noise) stimuli (two alternative, forced-choice, constant stimulus with feedback and head movements permitted, horizontal plane, 0 degree azimuth). The m.a.a.s and standard deviations (SD) were 3.0 degrees +/- 5.2 degrees for click trains and 10.9 degrees +/- 21.0 degrees for pure tones. The m.a.a.s did not vary significantly with frequency. The m.a.a.s and their SDs matched values reported from localization error studies. Narrowing the testing range from 32 degrees to 8 degrees resulted in random responses to the pure tones, though the click trains were readily localized. One subject presented with 2500 trials using an 8 kHz pure tone (with feedback, 16 degrees range) increased her responses from random to 88% correct during the testing. The click train m.a.a.s probably reflect the typical noise localizational abilities of the general population. For pure-tone m.a.a.s, experience/training may result in improved accuracy not applicable to the general public. The presence of a well defined time clue and a broad bandwidth sound results in significantly lower m.a.a.s than were obtained using pure tones which presumably present only interaural phase or intensity clues.

Acoustic Stimulation↗
PubMed2003

Multisensory enhancement of localization under conditions of induced myopia.

Enhanced behavioral performance mediated by multisensory stimuli has been shown using a variety of measures, including response times, orientation behaviors, and even simple stimulus detection. However, there has been little evidence for a multisensory-mediated improvement in stimulus localization. We suggest that this lack of effect may be a result of the high acuity of the visual system. To examine whether normal visual acuity may be masking any potential multisensory benefit for stimulus localization, we examined the ability of human subjects to localize visual, auditory and combined visual-auditory targets under conditions of normal and degraded vision. Under conditions of normal vision, localization precision (i.e., variability) was equivalent for visual and multisensory targets, and was significantly worse for auditory targets. In contrast, under conditions of induced myopia, visual localization performance was degraded by an average of 25%, while auditory localization performance was unaffected. However, during induced myopia, multisensory (i.e., visual-auditory) localization performance was significantly improved relative to visual performance. These results show a multisensory-mediated enhancement in human localization ability, and illustrate the cross-modal benefits that can be obtained when spatial information in one sense is compromised or ambiguous.

Acoustic Stimulation↗
PubMed1980

Localization of noise bands by Old World monkeys.

The acuity of auditory localization in Old World monkeys (Macaca) was determined psychophysically for 44 noise bands graded in bandwidth and center frequency. The acuity of localization was assessed through the method of constant stimuli under free-field conditions in an anechoic chamber. Monkeys were trained through positive-reinforcement operant-conditioning procedures to report a change in azimuth of the signal by releasing a response disk. The results show that localization thresholds are dependent upon the bandwidth of the signal over much of the macaque's range of audibility. Thresholds for the detection of a change in location varied from 18 degrees (for a signal 250 Hz in bandwidth centered at 11 200 Hz) to 4 degrees (for a signal 8000 Hz in bandwidth centered at 8000 Hz). The results suggest that the localization of spectrally complex signals is determined by a mechanism sensitive to periodicity (time-domain) information across the monkey's range of audibility.

Animals↗
PubMedDate not supplied

The effect of aminoglycoside antibiotics on the lateral line organ of Aplocheilus lineatus (Cyprinodontidae).

The effect of neomycin and streptomycin on the lateral line system of fishes was studied behaviourally by testing the animal's ability to localize a wave source. Increasing doses of both substances produce increasing loss of lateral line reactions, up to total inexcitability. The toxicity of both antibiotics was very similar. Lateral line sensitivity recovered 1-3 days after antibiotic removal.

Animals↗
PubMedDate not supplied

Coupling of visual to auditory cues during phonotactic approach in the phaneropterine bushcricket Poecilimon affinis.

In the duetting bushcricket species Poecilimon affinis the male calls at intervals of several seconds and is guided to the female by its short response clicks, which release phonotaxis only when perceived by the male during its sensory time window (40-170 ms after his call). The accuracy of phonotaxis in this acoustically open-loop system was investigated on a locomotion compensator with and without optical cues available. Phonotaxis in darkness was strongly meandrous with numerous roundabouts, while in a structured surrounding the oscillating course was attenuated. With a landmark available the male was able to maintain a straight course to the female. This is achieved by coupling of visual cues to an acoustically detected direction. Thus, in this species, the acoustic cues, which in the songs of continuously singing crickets and bushcrickets are permanently present, are replaced by optical ones. Restricting localization of female clicks to a short time window and using optical cues for target tracking allows straight orientation, even when guided by very short signals at long repetition intervals.

Acoustic Stimulation↗
PubMed2005

Sharing control between humans and automation using haptic interface: primary and secondary task performance benefits.

This paper describes a paradigm for human/automation control sharing in which the automation acts through a motor coupled to a machine's manual control interface. The manual interface becomes a haptic display, continually informing the human about automation actions. While monitoring by feel, users may choose either to conform to the automation or override it and express their own control intentions. This paper's objective is to demonstrate that adding automation through haptic display can be used not only to improve performance on a primary task but also to reduce perceptual demands or free attention for a secondary task. Results are presented from three experiments in which 11 participants completed a lane-following task using a motorized steering wheel on a fixed-base driving simulator. The automation behaved like a copilot, assisting with lane following by applying torques to the steering wheel. Results indicate that haptic assist improves lane following by least 30%, p < .0001, while reducing visual demand by 29%, p < .0001, or improving reaction time in a secondary tone localization task by 18 ms, p = .0009. Potential applications of this research include the design of automation interfaces based on haptics that support human/automation control sharing better than traditional push-button automation interfaces.

Analysis of Variance↗
PubMed1991

The role of head movement and pinnae in auditory localization in schizophrenia and psychosis.

This experiment examined the hypothesis that schizophrenics are less able than normals to make use of information concerning self movement when performing auditory localization tasks, and, therefore apply an alternative localization strategy, probably involving use of the pinnae. In this study three groups (healthy controls, schizophreniform patients and chronic schizophrenics) were compared in four experimental conditions: (1) head-movement and free pinnae; (2) static head and free pinnae; (3) head movement and covered pinnae; and (4) static head and covered pinnae. All subjects perform better with head movement than without it, with pinnae than with covered ones. Schizophreniform patients were affected more than normals by pinnae covering. This difference did not reach significance when normals were compared with chronic schizophrenics. A pronounced susceptibility to pinnae manipulation, correlated with medication level, appeared in the combined patient group in the moving condition. It was suggested that schizophreniform subjects, as compared to healthy controls are more depended on pinnae generated information for auditory localization and less able to compensate for its absence with movement generated information. The possibility that the effect is related to psychosis as such, rather than to schizophrenia in particular, was considered.

Adult↗
PubMed1995

A test of virtual auditory localization.

OBJECTIVE: The purpose of this study was to evaluate a test of virtual auditory localization including assessment of its ease of administration and its sensitivity to differences in binaural performance in children and adults. This test eliminates many potential problems inherent in any free-field localization test such as calibration problems, problems replicating source and listener locations, and issues associated with head movements. DESIGN: Binaural performance was measured using the virtual localization test and a simple binaural detection task, the masking-level difference (MLD), for three groups of subjects: adults, children with a negative history of otitis media, and children with a positive history of otitis media. There were five subjects in each group. The adults were all student volunteers; the children were recruited first and subsequently placed into groups based on their medical histories obtained from their physicians and parental reports. RESULTS: Results indicate that this test of virtual auditory localization is useful for measuring binaural performance in children and adults and is sensitive to differences in binaural processing. Performance of the adults and children with a negative history of otitis media was comparable on both of the binaural tests, and on the binaural detection task, was similar to that reported in the literature for normal-hearing listeners; but the children with a positive history of otitis media performed more poorly on both tests. CONCLUSIONS: The results of this study indicate that the virtual localization test described here is easy to administer to children and adults. The signal processing techniques used in this virtual auditory localization test lend themselves to straightforward comparisons across different laboratories and clinics and make this test a potentially useful clinical tool. The development of such a clinical test is currently under study.

Adult↗
PubMed1993

Auditory spectral discrimination and the localization of clicks in the sagittal plane.

Experiments show that the ability of human listeners to localize an impulsive sound in the medial sagittal plane (front, overhead, rear) deteriorates as the level of the sound increases. This negative level effect is strong for clicks but does not appear for broadband noise. It is conjectured that the negative level effect arises because the tonotopic excitation pattern is broadened for intense impulsive sounds. As a result, the spectral peaks and valleys, which are caused by anatomical filtering and which normally code for localization in the sagittal plane, are less recognizable. Filtered click discrimination experiments using headphones also show a negative level effect for clicks, but not for noise, and support this conjecture.

Acoustic Stimulation↗
PubMed2001

Spatio-temporal source imaging reveals subcomponents of the human auditory mismatch negativity in the cingulum and right inferior temporal gyrus.

We investigated the generators of the mismatch negativity by means of spatio-temporal source imaging on the basis of 64-channel electroencephalography data in order to study the time course and localization of proposed frontal sources. Results indicate that there are additional generators located both within the anterior cingulate gyrus and in the right inferior temporal gyrus, clearly separated from the supratemporal generators in space and time course. The cingulate generator is activated later than the temporal ones, which supports the hypothesis of a frontally located mechanism of involuntary switching of attention triggered by the temporal change detection system. Evidence for an additional right inferior temporal generator supports the hypothesis of right hemispheric dominance in early sound discrimination.

Acoustic Stimulation↗
PubMed2000

Selective attention fails to alter the dichotic listening lag effect: evidence that the lag effect is preattentional.

Berlin et al. (1973) reported that either stimulus from a dichotic pair of consonant-vowel syllables is processed preferentially when its presentation is delayed by 30-60 ms. In the first of three experiments with 60 normal right-handed adults, we replicated the Berlin et al. "lag effect," but only for asynchronies between 60 and 90 ms. In Experiment 2 subjects focused attention selectively on one ear. The results indicated that focused attention and stimulus asynchrony have additive effects: Performance improved at the attended ear irrespective of stimulus asynchrony, but the lag effect remained unchanged relative to the divided-attention condition. Experiment 3 entailed a signal detection task that allowed separate analysis of detection and localization accuracy. As in previous studies, selective attention to one ear increased the accuracy of localization but not detection at the attended ear. Both dependent measures indicated a lag effect that remained invariant as attention was manipulated. These findings imply that the lag effect is attributable to a preattentional stage of auditory processing.

Adult↗
PubMed2003

Acoustic factors govern developmental sharpening of spatial tuning in the auditory cortex.

Auditory localization relies on the detection and interpretation of acoustic cues that change in value as the head and external ears grow. Here we show that the maturation of these structures is an important determinant for the development of spatial selectivity in the ferret auditory cortex. Spatial response fields (SRFs) of high-frequency cortical neurons recorded at postnatal days (P) 33-39 were broader, and transmitted less information about stimulus direction, than in older ferrets. They also exhibited slightly broader frequency tuning than neurons recorded in adult animals. However, when infant neurons were stimulated through virtual ears of adults, SRFs sharpened significantly and the amount of transmitted information increased. This improvement was predicted by a model that generates SRF shape from the localization cue values and the neurons' binaural spectrotemporal response properties. The maturation of spatial response characteristics in auditory cortex therefore seems to be limited by peripheral rather than by central factors.

Acoustic Stimulation↗
PubMed1989

Single-unit activity related to active localization of acoustic and visual stimuli in the frontal cortex of the rhesus monkey.

Single-unit recordings were made in monkey periarcuate regions during the performance of limb movement tasks. A large class of neurons is described that appear to be involved in active localization of both acoustic and visual stimuli. These neurons failed to respond to stimuli of either modalities except in tasks where the location of the stimulus served as the cue for direction of movement.

Animals↗
PubMed1993

Auditory and visual localization performance in a sequential discrimination task.

Four subjects were tested in a two-alternative, forced-choice, three down-one up adaptive paradigm in which two 200-ms signals were presented sequentially with a 200-ms interstimulus interval. The subject's task was to indicate whether the second stimulus was to the right or left of the first. Tests were conducted with 57 dB (A-weighted), 1.0-kHz high-pass noise, the minimum audible angle (MAA) task, and with lights emitting 620 nm at a luminance level of 200 mL, the minimum visible angle (MVA) task. Localization performance in the MAA task was equal to or better than that obtained in the MVA task for all regions of the frontal field with only one exception, presentations at 0 degrees azimuth. The implications of these results are discussed.

Acoustic Stimulation↗