Dichotic listening in patients with splenial and nonsplenial callosal lesions.

The authors found splenial lesions to be associated with left ear suppression in dichotic listening of consonant-vowel syllables. This was found in both a rapid presentation dichotic monitoring task and a standard dichotic listening task, ruling out attentional limitations in the processing of high stimulus loads as a confounding factor. Moreover, directed attention to the left ear did not improve left ear target detection in the patients, independent of callosal lesion location. The authors' data may indicate that auditory callosal fibers pass through the splenium more posterior than previously thought. However, further studies should investigate whether callosal fibers between primary and secondary auditory cortices, or between higher level multimodal cortices, are vital for the detection of left ear targets in dichotic listening. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dichotic listening and corpus callosum magnetic resonance imaging in relapsing-remitting multiple sclerosis with emphasis on sex differences.

Twenty-five early-onset relapsing-remitting multiple sclerosis patients (12 women and 13 men) with mild disability were compared with 25 matched controls in a dichotic listening (DL) test under nonforced and forced attentional-shift conditions. Patients showed left ear impairment and no left ear advantage in the forced-left condition. Four corpus callosum (CC) regions were measured in patients on a rnidsaggital magnetic resonance imaging scan. The right ear score was negatively correlated whereas the left ear score was positively correlated with CC regions (significant only for the nonforced condition). Moreover, in men, the correlations with DL scores were linked mainly to the splenium and posterior isthmus, and in women, they were stronger for anterior isthmus and posterior body. An inverse correlation between months of disease evolution and CC area was found only in women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dichotic listening performance in relation to callosal area on the MRI scan.

The structural model of dichotic listening performance predicts reduced left ear scores in people with left hemisphere language dominance and impairment of the corpus callosum. The prediction was tested in patients with multiple sclerosis and evidence on the basis of magnetic resonance imaging (MRI) of callosal thinning. The results are partly in accordance with the structural model but indicate an effect of attentional set that correlated with quantitative measures of preserved callosal connections. The pattern of ear advantage was reversed in a small group of non-right-handed people. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic responses to shock-associated words in a nonattended message: a failure to replicate

Names of cities were shock associated and then embedded in material presented to the nonattended channel in a dichotic listening and shadowing situation. Despite earlier claims of differential responding to city names in the absence of awareness, no such differential responding was found. A test for conditioning following the dichotic listening task found that the subjects had been conditioned. Postexperimental interviews found that the subjects were aware of the city-shock contingency and had expected to be shocked during the dichotic listening task. Comparisons are made with other studies of galvanic skin responses to unattended words.     

Attention and automaticity in the processing of self-relevant information.

Studied the neglected aspect of social cognition: the way people select information for further processing from the vast amount available in social environments. A dichotic listening task was used in which 141 undergraduate Ss attended to or ignored self-relevant stimuli. It was found that self-relevant information required fewer attentional resources when presented to the attended channel, but more when presented to the rejected channel, relative to neutral words. This differential capacity allocation occurred despite Ss' lack of awareness of the contents of the rejected channel. Results support the existence and interaction of the 2 processes of attention in social information processing: a control process that regulates the contents of conscious awareness and an automatic process that attracts attention to stimuli without conscious intent. (70 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Iodine-131-MIBG scintigraphy in adults: interpretation revisited?

Functional reorganization of auditory attention was studied in 12 congenitally blind subjects and 12 controls using high-density event-related potentials during a highly focused dichotic listening task. Reaction times for the attend-ear intensity-deviant targets were markedly faster for the blind. Brain activity associated with sustained attention (N1 effect, Nd), and with the automatic detection of deviants in an unattended channel (MMN), did not exhibit reorganization. In contrast, marked plasticity changes were reflected in late auditory attentional processing (attend-ear targets), in the form of a prolonged negativity (200-450 ms post-stimulus) that was absent in the sighted subjects. The plasticity changes in the blind had a time course indicating progressive recruitment of parietal and then occipital regions, providing new evidence for cross-modal sensory reorganization in the blind.     

Processing capacity and switching attention in dichotic listening.

Describes 4 experiments with 82 undergraduates which indicate that (a) switching attention in a dichotic listening task requires processing capacity, and (b) increasing encoding difficulty reduces the amount of switching in a free recall dichotic listening task. Results are discussed in terms of a limited capacity processor model which contends that switching attention, encoding, and sustaining material all require processing capacity and that the S's strategy regarding switching attention is determined by the capacity available after capacity requirements for encoding are met. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dichotic listening performance, cognitive ability, and cerebral organization.

Explored linkages between dichotic listening performance, cognitive ability, and cerebral organization, addressing 3 main questions: (1) the relationship of sex, handedness, and familial sinistrality to auditory laterality and to selected aspects of cognitive performance; (2) the relationship between laterality and cognitive ability; and (3) the relationship between verbal and musical laterality. Two dichotic listening tests (one involving recognition of stop consonant-vowel syllables and the other, recognition of melodic patterns) were administered to 120 college students balanced for handedness, sex, and familial sinistrality. Ss also underwent psychometric tests. Results indicate an independence of verbal and nonverbal laterality effects and support a componential (modular) theory of brain organization rather than one of complementarity. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetric effects of ovarian hormones on hemispheric activity: Evidence from dichotic and tachistoscopic tests.

Previous studies have suggested a role of endogenously cycling ovarian hormones in the modulation of perceptual asymmetries. In the present investigation, participants were given perceptual asymmetry tests including verbal and nonverbal tachistoscopic and dichotic listening tasks during the menstrual and midluteal phases of the menstrual cycle. Salivary levels of estrogen and progesterone were also measured. Analyses of performance on the tachistoscopic tests revealed that left visual field, but not right visual field, accuracy was significantly lower for both verbal and nonverbal tasks at the midluteal phase than at the menstrual phase. Right ear performance on the nonverbal dichotic test was significantly reduced at the midluteal phase. Results suggest suppression of right hemisphere processing areas and possible reduction in callosal transfer efficiency at higher levels of ovarian steroids. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal Dichotic Listening and Manual Performance in Children With Congenital Unilateral Brain Lesions.

The authors assessed manual performance and verbal dichotic listening performance in 16 epilepsy-free children with congenital unilateral brain lesions and normal IQ to investigate cerebral reorganization. In all children, the paretic hand had fair grip function, but reaction times were impaired, and cerebral reorganization of hand function in those with right hemiplegia was shown by the high incidence of pathological left-handedness. The dichotic listening results showed that most children with left lesions had a left ear advantage significantly related to the extent of brain damage. This finding suggests that extent of cortical damage and presence of thalamic involvement, irrespective of neuropathology, are the primary factors inducing rightward cerebral language reorganization in children with unilateral congenital brain lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of aphasic and non-brain-injured adults on a dichotic CV-syllable listening task

A dichotic CV-syllable listening task was administered to a group of eleven non-brain-injured adults and to a group of eleven adult aphasics. The results of this study may be summarized as follows: 1)The group of non-brain-injured adults showed a slight right ear advantage for dichotically presented CV-syllables. 2)In comparison with the control group the asphasic group showed a bilateral deficit in response to the dichotic CV-syllables, superimposed on a non-significant right ear advantage. 3) The asphasic group demonstrated a great deal of intersubject variability on the dichotic task with six aphasics showing a right ear preference for the stimuli. The non-brain-injured subjects performed more homogeneously on the task. 4) The two subgroups of aphasics, a right ear advantage group and a left ear advantage group, performed significantly different on the dichotic listening task. 5) Single correct data analysis proved valuable by deleting accuracy of report for an examination of trials in which there was true competition for the single left hemispheric speech processor. These results were analyzed in terms of a functional model of auditory processing. In view of this model, the bilateral deficit in dichotic performance of the asphasic group was accounted for by the presence of a lesion within the dominant left hemisphere, where the speech signals from both ears converge for final processing. The right ear advantage shown by one asphasic subgroup was explained by a lesion interfering with the corpus callosal pathways from the left hemisphere; the left ear advantage observed within the other subgroup was explained by a lesion in the area of the auditory processor of the left hemisphere.     

Effects of sex and sex role attributions on the ear advantage in dichotic listening.

The Bem Sex Role Inventory (BSRI) and a dichotic listening task were administered to 30 participants in order to investigate the effect of polar sex (male, female) and spectral sex (masculinity, femininity) on hemispheric interactions. The dichotic pairs consisted of the consonant-vowel syllables Bee, Dee, Gee, Pee, Tee, and Kee. Although overall performance was the same across groups, women demonstrated smaller right ear advantages than men, due primarily to smaller right ear scores. Less masculine men also had smaller right ear advantages than more masculine men, but this difference was due primarily to greater left ear scores. These results were interpreted both in terms of the callosal relay and direct access models of hemispheric processing. Based on these interpretations, it was suggested that sex and sex role attribution have similar, but not identical effects on interhemispheric relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Controlling for stimulus dominance in dichotic listening tests: A modification of !l.

Dichotic listening procedures have been used to assess cerebral lateralization in normal Ss. One particularly useful technique is the use of stimuli that fuse into a single percept. Although this procedure has many advantages over other dichotic listening methods, it is particularly susceptible to stimulus dominance, which acts as noise in a S's response data, thus reducing the power of any statistical test of the ear advantage. It is proposed that the solution to this problem is a log-linear analysis of the response data to yield a λ-type index (λ*) that is a measure of ear dominance independent of stimulus dominance. Details of the analysis are provided, as well as a sample analysis of data collected from 104 right-handed and 30 left-handed Ss. Comparisons are drawn between the log-linear analysis and other methods that have been proposed to control for stimulus dominance in this single-response dichotic fusion procedure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masking produced by broadband noise presented in virtual auditory space

An attempt has been made to relate the masking effects studied under dichotic listening conditions to masking seen in the free field. Rather than use a free-field masking paradigm combined with monaural and binaural listening conditions, broadband maskers presented in virtual auditory space (VAS) have been used. Two virtual locations were tested: One was the right interaural axis (+90 degrees from the anterior midline) and the other was 40 degrees right of the anterior midline. Narrow-band (critical bandwidth) dichotic and diotic maskers were also derived from the VAS masker by bandpass filtering around the test frequency. This procedure preserved the interaural differences within the critical band about the test frequency but removed information outside the critical band. Using a diotic target tone of 0.6 kHz with a narrow-band masker centered on 0.6 kHz there was an increase in signal detection in the dichotic conditions when compared to that attributable to either ear alone. Furthermore, there was no further advantage in signal detection at this target frequency when a broadband VAS masker was used. This suggests that for low-frequency targets, the binaural differences within the critical band about the target frequency are sufficient for effective unmasking. In contrast, for a target frequency of 4 kHz, a dichotic narrow-band masker resulted in a reduction in detection compared to that attributable to either ear. However, detection improved to the level attributable to the far ear when a broadband VAS masker was used. This suggests that information outside the critical band is involved in the unmasking of high-frequency targets.     

Interhemispheric transfer in schizophrenics, depressives, and normals with schizoid tendencies.

Although several studies suggest that schizophrenics suffer from an impairment in the interhemispheric transfer (IHT) of information, methodological weaknesses in these studies preclude clear interpretation of their results. This study addresses these criticisms in order to provide a clearer test of the IHT theory. Schizophrenics, depressives, normal controls, and normals with schizoid tendencies were assessed on five measures of IHT (verbal and nonverbal dichotic listening, intermanual transfer, bimanual block design, finger sequence repetition) and two measures of unilateral hemispheric processing (lateral eye movements, auditory thresholds). Results consistently failed to support an IHT deficit interpretation of schizophrenia. Schizoid normals had a significantly greater right-ear advantage on verbal dichotic listening than both psychiatric groups, a result suggesting enhanced left-hemisphere activation in schizoid normals. It is concluded that the IHT theory requires stronger empirical substantiation than has been obtained to date to warrant further consideration as a central theory of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Baseline asymmetries in brain electrical activity predict dichotic listening performance.

Forty-four right-handed participants were assessed on 2 occasions 6 weeks apart on electrophysiological measures of activation asymmetry derived from spectral estimates of electroencephalogram (EEG) alpha power in homologous scalp electrodes. Approximately 4 months following the final EEG assessment. participants were administered a dichotic listening CV-syllables task. Overall, participants exhibited a highly significant right-ear advantage. Differences among individuals in ear asymmetry were predicted by the earlier recorded electrophysiological data. Participants with greater activation in left-sided posterior temporal and parietal regions showed a larger right-ear advantage. In addition, a larger right-ear advantage was predicted by right-sided prefrontal activation. These data indicate that some of the variance in dichotic listening performance can be explained by dispositional activation asymmetries and is associated with a complex pattern of posterior and anterior activation asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateralization of receptive language in preschoolers: Test–retest reliability in a dichotic listening task.

On 2 occasions dichotic digit tapes were presented to 29 right-handed children (aged 33–65 mo). Results indicate that the dichotic listening tasks yielded measures with sufficient test–retest stability to permit reliable group comparisons, but that such indices may differ in terms of their contamination by sample-specific distributions of ability levels. It is suggested that conclusions not be drawn from such measures unless different indices of laterality show converging results and that when groups are compared, investigators include tabulations of both the difference and accuracy scores in their results. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential neural contributions to native- and foreign-language talker identification.

Humans are remarkably adept at identifying individuals by the sound of their voice, a behavior supported by the nervous system’s ability to integrate information from voice and speech perception. Talker-identification abilities are significantly impaired when listeners are unfamiliar with the language being spoken. Recent behavioral studies describing the language-familiarity effect implicate functionally integrated neural systems for speech and voice perception, yet specific neuroscientific evidence demonstrating the basis for such integration has not yet been shown. Listeners in the present study learned to identify voices speaking a familiar (native) or unfamiliar (foreign) language. The talker-identification performance of neural circuitry in each cerebral hemisphere was assessed using dichotic listening. To determine the relative contribution of circuitry in each hemisphere to ecological (binaural) talker identification abilities, we compared the predictive capacity of dichotic performance on binaural performance across languages. Listeners’ right-ear (left hemisphere) performance was a better predictor of binaural accuracy in their native language than a foreign one. This enhanced role of the classically language-dominant left hemisphere in listeners’ native language demonstrates functionally integrated neural systems for speech and voice perception during talker identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endogenous and exogenous control of attention in dichotic listening.

Dichotic listening to verbal stimuli results in a right ear advantage (REA), indicating a left hemisphere processing superiority. The magnitude of the REA can be modulated by instructions to direct attention to the left or right ear stimulus. A previous study from our laboratory showed that presenting a prime syllable before the presentation of the dichotic syllables increases reports of the nonprimed syllable, apparently a negative priming effect that inhibits attention to the distracting prime representation. The present study combined attention instruction and priming, making up a 3 × 3 factorial design. The prime stimulus was a single consonant-vowel syllable presented binaurally just before onset of the dichotic consonant-vowel syllables. Results showed that both instructions and priming manipulations had an effect on which dichotic stimulus was selected. There was also a significant interaction between attention instruction and priming manipulation, indicating that the mechanism for instructed attention and the mechanism for negative priming work on the same level of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dynamics of attending: How people track time-varying events.

A theory of attentional dynamics is proposed and aimed at explaining how listeners respond to systematic change in everyday events while retaining a general sense of their rhythmic structure. The approach describes attending as the behavior of internal oscillations, called attending rhythms, that are capable of entraining to external events and targeting attentional energy to expected points in time. A mathematical formulation of the theory describes internal oscillations that focus pulses of attending energy and interact in various ways to enable attentional tracking of events with complex rhythms. This approach provides reliable predictions about the role of attending to event time structure in rhythmical events that modulate in rate, as demonstrated in 3 listening experiments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)