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Auditory spatial attention using interaural time differences.

Previous probe-signal studies of auditory spatial attention have shown faster responses to sounds at an expected versus an unexpected location, making no distinction between the use of interaural time difference (ITD) cues and interaural-level difference cues. In 5 experiments, performance on a same-different spatial discrimination task was used in place of the reaction time metric, and sounds, presented over headphones, were lateralized only by an ITD. In all experiments, performance was better for signals lateralized on the expected side of the head, supporting the conclusion that ITDs can be used as a basis for covert orienting. The performance advantage generalized to all sounds within the spatial focus and was not dissipated by a trial-by-trial rove in frequency or by a rove in spectral profile. Successful use by the listeners of a cross-modal, centrally positioned visual cue provided evidence for top-down attentional control.

Adult↗

Location and frequency cues in auditory selective attention.

The roles of frequency and location cues in auditory selective attention were investigated in a series of experiments in which target tones were distinguished from distractors by frequency, location, or the conjunction of frequency and location features. When frequency separations in high-rate tone sequences were greater than 1 octave, participants were fastest at identifying targets defined by frequency and were sometimes faster at identifying conjunction than location targets. Frequency salience diminished as filtering demands were reduced: At long interstimulus intervals (> 2.0 s), performance was superior in location conditions. The results suggest that frequency may play a role in auditory selective attention tasks analogous to the role of spatial position in visual attention.

Adolescent↗

Does auditory streaming require attention? Evidence from attentional selectivity in short-term memory.

R. P. Carlyon, R. Cusack, J. M. Foxton, and I. H. Robertson (2001) have argued that attention is crucial for auditory streaming. The authors review R. P. Carlyon et al.'s (2001) arguments and suggest that a pertinent literature, the irrelevant sound paradigm--demonstrating preattentive auditory streaming--has been overlooked. In illustration of this alternative approach, the authors include a novel single experiment demonstrating the impact of preattentive auditory streaming on short-term serial memory. It is concluded that R. P. Carlyon et al.'s (2001) results do not definitively demonstrate that auditory streaming processes are dependent on attention; indeed, they are compatible with alternative accounts of the relationship between perceptual organization and attention.

Analysis of Variance↗

Apparent distance of sounds recorded in echoic and anechoic chambers.

With miniature microphones inserted into the external ear canals of a model and the sound source 90 degrees to left of midline, low-pass, and broadband noise bursts were picked up and recorded on magnetic tape. The bursts were generated in two highly contrasting acoustic environments: an anechoic and an echoic chamber. The taped sounds were played back monaurally and binaurally via headphones to 16 listeners seated in an acoustically neutral setting. They were instructed to estimate the distance of the stimuli. Apparent distances of bursts recorded in the echoic or reverberant chamber far exceeded those recorded in the anechoic chamber. It mattered not whether the sounds were presented monaurally or binaurally. What did influence distance estimates dramatically was the frequency composition of the stimuli. Low-pass sounds recorded in either acoustic environment were consistently judged to be further removed than high-pass sounds recorded in the same setting. They were also more likely to appear from behind the listener. In our moment-to-moment transaction with the acoustic environment, distant sounds generally have less acoustic energy in the higher audio frequency. We suggest that this lifetime of auditory experience influenced our listeners' scale of relative distance.

Auditory Perception↗

Eye position and the control of auditory attention.

In a binaural selective-listening task, subjects' performance was strongly influenced by the position of their eyes, Subjects remembered fewest words from the relevant message and made the most intrusion errors when looking in the direction of the irrelevant input. Looking away from the relevant message but in a direction from which no auditory input originated was not significantly different from looking toward the relevant input. As the speakers were arrayed along a vertical line, the results cannot be interpreted as reflecting activation of the cerebral hemispheres (unlike earlier related work). The results are discussed in terms of the control of auditory attention.

Attention↗

Attention switching and patterns of sound locations in counting clicks.

The present study investigates the process of auditory attention switching by means of experiments in which observers counted the number of monaurally and interaurally presented clicks. Several studies have reported that the number of interaurally presented events was underestimated relative to monaurally presented ones. Ten Hoopen and Vos, however, could not replicate this phenomenon. The data from Experiment 1 demonstrate that such a discrepancy is caused by the different orders in which the monaural and interaural sequences were presented. With blocked presentation, interaural sequences were counted less well than monaural sequences, whereas there was no difference when all sequence types were randomized. An attention-switching mechanism was proposed to account for performance on interaural sequences during blocked presentation. In the random case observers presumably did not switch their attention to and fro, but "multiplexed" the channels. Experiment 2 investigated whether observers can deliberately suppress the process of attention switching when confronted with blocked interaural sequences. The results show that they cannot, which suggests that attention switching is an automatic process.

Adult↗

Selective attention to multidimensional auditory stimuli.

Event-related brain potentials (ERPs) elicited by multidimensional auditory stimuli were recorded from the scalp in a selective-attention task. Subjects listened to tone pips varying orthogonally between two levels each of pitch, location, and duration and responded to longer duration target stimuli having specific values of pitch and location. The discriminability of the pitch and location attributes was varied between groups. By examining the ERPs to tones that shared pitch and/or locational cues with the designated target, we inferred interrelationships among the processing of these attributes. In all groups, stimuli that failed to match the target tone in an easily discriminable cue elicited only transitory ERP signs of selective processing. Tones sharing the "easy" but not the "hard" cue with the target elicited ERPs that indicated more extensive processing, but not as extensive as stimuli sharing both cues. In addition, reaction times and ERP latencies to the designated targets were not influenced by variations in the discriminability of pitch and location. This pattern of results is consistent with parallel, self-terminating models and holistic models of processing and contradicts models specifying either serial or exhaustive parallel processing of these dimensions. Both the parallel, self-terminating models and the holistic models provide a generalized mechanism for hierarchical stimulus selections that achieve an economy of processing, an underlying goal of classic, multiple-stage theories of selective attention.

Acoustic Stimulation↗

Memory of auditory lists by rhesus monkeys (Macaca mulatta).

Monkey auditory memory was tested with increasing list lengths of 4, 6, 8, and 10 sounds. Five-hundred and twenty environmental sounds of 3-s duration were used. In Experiment 1, the monkeys initiated each list by touching the center speaker. They touched 1 of 2 side speakers to indicate whether a single test sound (presented from both side speakers simultaneously) was or was not in the list. The serial-position functions showed prominent primacy effects (good first-item memory) and recency effects (good last-item memory). Experiment 2 repeated the procedure without the list-initiation response and with a variable intertrial interval. The results of both experiments were similar and are discussed in relation to theories and hypotheses of serial-position effects.

Animals↗

Functional characteristics of auditory temporal-spatial short-term memory: evidence from serial order errors.

The functional characteristics of auditory temporal-spatial short-term memory were explored in 8 experiments in which the to-be-remembered stimuli were sequences of bursts of white noise presented in spatial locations separated in azimuth. Primacy and recency effects were observed in all experiments. A 10-s delay impaired recall for primacy and middle list items but not recency. This effect was shown not to depend on the response modality or on the incidence of omissions or repetitions. Verbal and nonverbal secondary tasks did not affect memory for auditory spatial sounds. Temporal errors rather than spatial errors predominated, suggesting that participants were engaged in a process of maintaining order. This pattern of results may reflect characteristics that serial recall has in common with verbal and spatial recall, but some are unique to the representation of memory for temporal-spatial auditory events.

Attention↗

Effects of spatial context during acquisition on the recall of attributive information.

We found that learners were sensitive to the spatial context in which various information was obtained and that they could use it symbolically to aid recall even when spatial cues were not available during testing. In three experiments, televised and purely aural statements made by various speakers were presented at distinct locations in the recipient's immediate surroundings. This was found to increase attributive recall compared to (a) all information sources in a single place, (b) information sources in several places but with place not consistently linked with information sources, and (c) use of a nonspatial stimulus context consistently associated with information source, such as the physical appearance of announcers. Theoretically, we conclude, with Hasher and Zacks, the place provides especially privileged cues and that not all content-correlated background stimuli are equipotent cues in associative learning. Practically, we recommend that in order to remember who said what, it helps to have speakers in separate and distinct places.

Cues↗

Preexposure and extinction effects of lithium chloride induced taste-potentiated aversions for spatially contiguous auditory food cues in rats.

Taste potentiated illness-induced aversions for noisy food were studied in Sprague-Dawley rats. The rats ate from receptacles containing salty food and a contiguous tone produced by speakers under the food followed by lithium chloride injections. In preference tests, the rats then avoided noisy food in favor of quiet food followed by extinction and spontaneous recovery of the auditory aversion over repeated nonreinforced trials. Other rats were given either 4 or 10 days of exposure to the noisy food prior to taste-toxicosis treatment. None of these rats subsequently avoided noisy food. The importance of spatial contiguity and methodological variation in associating nongustatory food cues with illness is discussed.

Animals↗

Visual and auditory spatial and nonspatial delayed-response performance by Korsakoff and non-Korsakoff alcoholic and aging individuals.

Thirty-six male alcoholics (13 with Korsakoff's syndrome) and 24 controls performed visual and auditory delayed-response tasks sensitive to prefrontal cortical damage in nonhuman primates. Korsakoff patients were consistently impaired compared with other subjects. Impairments by Korsakoff patients were evident when demands were placed on visual processing time (brief stimulus durations), and the deficits became exaggerated with increased demands on short-term memory. Under the most difficult experimental conditions, controls and non-Korsakoff alcoholics who were over 50 years old performed somewhat worse compared with younger groups 27-49 years old. Age-linked deficits were mild compared with Korsakoffs' deficits, and age-group differences disappeared with easier task demands. The results implicate cortical pathology in alcoholism and normal chronological aging and suggest that prefrontal damage accompanies alcoholic Korsakoff's syndrome.

Age Factors↗

Free-field binaural unmasking in ferrets.

Free-field detection by normal and monaural ferrets of a 500-Hz tone presented over 1 laterally placed loudspeaker and partially masked by narrow-band noise from 2 sources was studied at 2 angular separations of the noise sources (0 degree and 180 degrees). Monaural listening was achieved either by plugging 1 ear canal or removing 1 cochlea. Normal ferrets showed an improvement in detectability of the tone when there was a 180 degrees separation between the noise sources. This unmasking of the tone was abolished in both groups of monaural ferrets, suggesting that the unmasking was due to binaural processing. The development of an animal model demonstrating free-field binaural unmasking, in a species other than humans, will allow investigation into the functional consequences of experimental hearing loss.

Animals↗

Studies of binaural detection in the rabbit (Oryctolagus cuniculus) with Pavlovian conditioning.

A Pavlovian conditioned eyeblink response in rabbits (Oryctolagus cuniculus) was used to study psychoacoustical phenomena previously demonstrated in human listeners and other animals. This article contains the results of a tone-in-noise detection study to examine 2 psychoacoustical phenomena in rabbit and in human listeners: (a) the binaural masking level difference (BMLD) and (b) differential performance across reproducible noise masker waveforms. The rabbits demonstrated a BMLD comparable in size to other species. Significant differences in performance across reproducible noise masker waveforms were seen in the rabbits. This performance was compared with the performance of human listeners using the same set of waveforms.

Adult↗

Effect of visual experience on the habituation of orienting behavior.

Orienting behavior elicited by novel visual and auditory stimuli was examined in light-reared (LR) and dark-reared (DR) rats at 30, 60, 90, or 120 days of age. Orienting behavior was assessed by examining the rat's ability to interrupt ongoing licking and perform appropriate head and postural adjustments when apparently moving or stationary light displays or tones were presented. When the lights were first presented to the LR and DR rats, their orienting behavior did not differ at any of the ages examined. However, age and visual experience did influence habituation and recovery of orienting with changes in the light display. The older DR rats habituated with fewer repeated presentations of the light displays than their LR counterparts and did not recover orienting as effectively to all the subsequent changes of the light displays. The younger LR and DR rats did not differ reliably. These results are discussed with regard to the nature of the habituation process for rodents and the relation between visual experience and habituation of attentional responses.

Animals↗

Aging and single versus multiple cues in source monitoring.

Participants heard words said by 2 speakers and later decided who said each word. The authors varied the perceptual distinctiveness of the speakers and the distinctiveness of the cognitive operations participants performed on the words. Relative to younger adults, older adults had significantly lower source monitoring scores when perceptual or cognitive operations conditions were similar but not when either cue was more distinctive. Combining cues did not affect source monitoring of younger adults but hurt older adults' performance relative to the distinctive perceptual condition. Evidently, older adults generate cognitive cues at the expense of encoding perceptual cues; any deficit in binding perceptual and semantic information disadvantages them more in source monitoring than in old/new recognition. There was no correlation between neuropsychological tests assessing frontal function and source monitoring in older adults.

Adolescent↗

Age differences in using source-relevant cues.

Subjects heard words originating from 2 speakers and later decided which of the 2 speakers said the words. Older adults had difficulty with source monitoring when perceptual cues from 2 sources were similar (2 female speakers), but this difficulty was overcome when perceptual cues were distinctive (a male and a female speaker) and were the only salient cues to source. Older adults also benefited from distinctive spatial cues when these were the only salient cues to source. Older adults, however, experienced difficulties in using multiple cues (both perceptual and spatial) to source effectively, whereas younger adults were able to use multiple cues to enhance their source-monitoring performance. It is suggested that age differences in source monitoring result from differential cue utilization.

Adult↗

An auditory illusion predicted from a weighted cross-correlation model of binaural interaction.

In humans, the lateral movement of an acoustic source produces dynamic changes in the relative sound-pressure level and time of arrival of the acoustic wave at the 2 ears. The dynamic nature of these cues is assumed to play an important role in the perception of lateral motion. A phenomenon of auditory motion is reported whose lateral direction and relative velocity may be specified while interaural differences are kept constant. The stimulus producing this percept is a narrowband wave-form whose instantaneous bandwidth is a cosine function of time. This phenomenon is predicted from a model of cross-correlation that estimates the running position of an image from a weighted combination of 2 variables: (a) magnitude of interaural delay, with smaller delays receiving more weight, and (b) consistency of interaural information across frequency.

Auditory Perception↗