Outcome of cognitive–behavioral therapy for depression: Relation to hemispheric dominance for verbal processing.

Unmedicated depressed outpatients were tested on dichotic syllable and complex tone tests prior to receiving 16 weekly sessions of cognitive therapy (n?=?31 ) or 6–12 weeks of placebo treatment (n?=?45). Cognitive-therapy responders had twice the right-ear (left hemisphere) advantage for syllables when compared with nonresponders but did not differ from nonresponders on the nonverbal task. The larger right-ear advantage in cognitive-therapy responders was due to better right-ear accuracy; they did not differ from nonresponders in left-ear accuracy. No differences in perceptual asymmetry or accuracy were found between placebo responders and nonresponders. Right-ear accuracy for syllables was the best predictor of response to cognitive therapy in a logistic regression analysis. The findings suggest that greater left-hemisphere advantage for verbal processing is associated with more favorable outcome of cognitive therapy for depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual asymmetry differences between major depression with or without a comorbid anxiety disorder: A dichotic listening study.

Predictions that anxious and nonanxious depression would differ in perceptual asymmetry (PA), as well as in sensitivity for perceiving emotional words, were evaluated using dichotic listening tasks. A total of 149 patients having a major depressive disorder (51 with and 98 without an anxiety disorder) and 57 healthy controls were tested on fused-word and complex tone tasks. The anxious and nonanxious depression groups showed a consistent difference in PA across tasks; that is, the anxious group had a larger left-ear advantage for tones and a smaller right-ear advantage for words when compared with the nonanxious group. There was no group difference in sensitivity for perceiving emotional words. Patients having an anxious depression appear to have a greater propensity to activate right than left-hemisphere regions during auditory tasks, whereas those having a nonanxious depression have the opposite hemispheric asymmetry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of three strategies of attention in dichotic monitoring.

Investigated 3 strategies of attention in 108 Ss in 3 age groups (7, 11, and 20 yrs). Ss monitored lists of monaural and dichotic words and responded manually to target words. Target detection rates in unequal division of attention (Exp I) showed that selection of the relevant input improved with age. The degree of attenuation of the irrelevant input was dependent on which ear was being ignored, but this effect interacted with age. The 7-yr-olds could not attend effectively to left-ear items. Exp II simplified the focusing strategy by eliminating response requirements to the irrelevant input. Selectivity improved with this strategy, particularly in 7-yr-olds. Equal division of attention between the 2 ears (Exp III) revealed a constant right-ear advantage in each age group. Differentiation of the 3 voluntary strategies improved between ages 7 and 11. In adults, the 3 strategies were clearly distinguished. Results are interpreted in terms of a multiprocess model of attention: Perceptual factors such as dichotic interaction and hemispheric asymmetry were strategy dependent but not age dependent. Voluntary selective attention was age dependent and affected the degree to which hemispheric asymmetry could be overcome. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual asymmetry in psychosis-prone college students: Evidence for left-hemisphere overactivation.

The hypothesis that psychosis-prone students demonstrate a pattern of exaggerated perceptual asymmetry across both left- and right-hemisphere dichotic-listening tasks (consonant-vowel [CV] and tonal contour discrimination) was investigated. Ss who scored high on the Perceptual Aberration or Magical Ideation scale or both (n?=?20) demonstrated a significantly exaggerated right-ear advantage on a CV task in relation to normal control Ss (n?=?27) but showed a reduced left-ear advantage on a tone task. The hypothesis of exaggerated functional lateralization across hemispheres in the psychosis-prone Ss was not supported, but the results are consistent with a hypothesis of left hemisphere overactivation in this sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Secretory expression of a single-chain insulin precursor in yeast and its conversion into human insulin

It has been proposed that prenatal testosterone (T) may contribute to the development of hand preference and cerebral functional asymmetry in humans. To investigate any persisting association between T and asymmetry in adulthood, left-handed (LH) and right-handed (RH) men and women were administered a hand preference questionnaire and the Fused Dichotic Words Test. Testosterone was measured in samples of saliva. Results showed that LH subjects of both sexes had lower salivary T concentrations than their RH counterparts. Among LH males, subjects with a right-ear advantage in dichotic listening tended to have lower T concentrations than subjects with a left-ear advantage. These results are consistent with the notion that T may be involved in the development of hand preference and cerebral functional asymmetry.     

Asymmetries of selective listening and attention switching in children.

Administered a selective listening task to 155 normal right-handed 3–12 yr old children. The stimuli consisted of dichotic digits, ranging from single pairs to strings of 4 pairs/trial. Each S attempted to focus attention on 1 ear for 8 practice trials and 28 test trials before switching attention to the opposite ear. Separate analyses of correct responses and intrusion errors yielded almost identical results: There was a significant right-ear advantage (REA) and a developmental increase in overall performance, but there was no developmental change in degree of asymmetry. The REA increased with increasing list length, but independent analyses for each list length failed to reveal any developmental changes in REA. Listening asymmetry was influenced markedly by the order in which the ears were monitored; Ss of all ages had difficulty in switching attention from right ear to left. Results support the developmental invariance hypothesis of cerebral lateralization and demonstrate that auditory asymmetry is not merely a direct reflection of some fixed structural asymmetry in the brain. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective listening asymmetry in preschool children.

42 right-handed preschoolers listened to dichotic presentations of digit names in 2 experimental sessions. Ss were told to report only the digit arriving at the designated ear; the target ear was designated prior to the dichotic presentation in one session (precuing condition) and after the presentation in the other session (postcuing condition). A significant right-ear superiority was found for all 3 dependent variables: number of correct identifications, total number of digits reported from each ear, and number of intrusion errors. Thus, the procedure demonstrated a marked asymmetry and, therefore, left lateralization of verbal processing in children as young as 3 yrs of age. Since the magnitude of asymmetry was as great in the precuing condition as in the postcuing condition, input factors (perceptual or attentional factors) are sufficient to account for the right-ear superiority. There was no age difference in degree of right-ear advantage. Correlations between asymmetry scores in the 2 sessions ranged between .60 and .68 for the 3 dependent variables. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Left-ear superiority in children for processing auditory emotional material.

Investigated hemispheric asymmetries in children for processing auditory material varying in emotional intonation or verbal content. 31 kindergartners, 32 4th graders, and 32 8th graders reported on the emotional content and on the verbal content of dichotically presented sentences. Ss listened to tapes of 4 phrases spoken in tones that were happy, sad, angry, or neutral and to sentences that varied in verbal content only. Ss also completed a handedness questionnaire and a hearing test. All age groups showed a left-ear advantage for reporting on the emotional material and a right-ear advantage for reporting on the verbal material. For the emotional task, the degree of ear asymmetry did not vary significantly as a function of emotional category. Findings indicate the the right hemisphere is specialized for mediating auditory emotional stimuli as early as 5 yrs of age. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of directed attention on cerebral asymmetries in normal and learning-disabled children.

Using a dichotic listening task employing both undirected and directed attention conditions, cerebral asymmetries were examined in matched populations of 32 normal and 32 learning-disabled (LD) children (ages 7 yrs 6 mo–13 yrs 2 mo). The analysis of recall performance indicated that development was not a significant factor in either group; both the normal and LD Ss showed a right-ear effect, although the LD Ss performed at a degraded level and were unable to demonstrate a right-ear advantage (REA) when attention was directed to the left ear, unlike normal Ss, who produced the REA despite the directed attention conditions. Results suggest that LD children probably do not suffer from developmental delays but rather from a defect in callosal functioning that interferes with their ability to process verbal information simultaneously. (41 ref) (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)     

Orientation of selective effects of body tilt on visually induced perception of self-motion

In this study, to test an inference from the 1991 Previc hypothesis that right-handers have a right-ear advantage, the durations of hearing for the right and left ears were compared for 81 right- and 45 left-handed high school students. In the present study, right-handedness was associated with a right-ear advantage and left-handedness was associated with a left-ear advantage. In addition, there was a significant positive correlation between the durations of hearing for the right and left ears and the scores for right-handedness for right-handed subjects. The durations of hearing for the right and left ears were negatively correlated with the left-handedness for left-handed subjects. These results suggest hand preference may be related to asymmetry of aural sensitivity.     

Investigation of Functional Hemispheric Asymmetry of Language in Tinnitus Sufferers.

The authors tested functional hemispheric asymmetry through word dichotic listening and lateralized lexical decision tasks in tinnitus patients and controls stimulated by a continuous tinnitus-like noise to test the influence of a tinnitus-like external stimulation. A classic right-ear advantage was shown in the auditory task for all but right-ear tinnitus patients, who performed as equally badly when the stimuli were presented to the right and left ears. Concerning the visual task, all participants demonstrated the expected right visual field advantage for word stimuli. Moreover, those who submitted to external stimulation demonstrated normal asymmetric patterns. These data suggest a specific effect of tinnitus on central processing and provide evidence for a functional reorganization induced by this auditory phantom perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal exposure to diethylstilbestrol (DES) and the development of sexually dimorphic cognitive abilities and cerebral lateralization.

Investigated the possibility that the perinatal hormonal environment is related to the development of cognitive sex differences in humans by comparing 25 women who had been exposed prenatally to DES, a synthetic estrogen, to their unexposed sisters. All Ss completed word fluency and spatial relations tests, the Wonderlic Personnel Test, and a dichotic listening task. The DES-exposed Ss showed a more masculine pattern of lateralization (i.e., a stronger right-ear advantage) than did their sisters on a verbal dichotic task. However, no differences were observed between exposed and unexposed Ss in verbal or visuospatial ability. Although interpretation of these data must be cautious, they provide some support for a relationship between high prenatal estrogen levels and the development of masculine-typical function in humans. Implications for previous studies of biological contributions to cognitive sex differences and possible mechanisms for estrogenic effects on the development of lateralization are discussed. (114 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dichotic-listening measures of brain laterality in mania.

Dichotic syllable and complex tone tests were used to compare performance asymmetries in 35 manic patients with 26 normal controls and to determine whether there were changes in laterality with remission of the manic state. Relationships of performance asymmetries to treatment outcome and symptom features were also examined. Compared with normal controls, manic patients showed overall poorer accuracy, particularly for complex tones presented to the left ear, and they failed to show the normal left-ear (right-hemisphere) advantage for complex tones. Abnormal laterality for complex tones was present in patients who later responded to treatment but not in nonresponders. In the euthymic state, patients showed improved left-ear accuracy for complex tones and more normal perceptual asymmetry. These findings suggest that mania is associated with a decrement in right-hemisphere processing of complex tonal information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemisphere-specific interference in dichotic listening: Task variables and individual differences.

In Exps I and II, 214 right-handed college students were required to identify dichotically presented CV syllables with either no concurrent memory (CM) load or with a CM load of 6 low-imagery nouns. Based on performance on their initial set of no-load trials, Ss were assigned to either a right-, left-, or no-ear advantage (REA, LEA, or NEA) group. Results for the REA group were similar to the results of previous studies of visual laterality and concurrent activity: Introducing a CM load of 6 words reduced recognition of right-ear CVs but not left-ear CVs. Furthermore, these effects persisted across 2 blocks of no-load and memory-load trials. This Memory Load?×?Ear interaction was weaker in the NEA group and tended to be reversed in the LEA group. About 10% of Ss showed a consistent LEA for CV recognition, and, for these Ss, introducing a CM load of 6 words reduced recognition of left-ear CVs but did not change the recognition of right-ear CVs. Again, these effects persisted across 2 blocks of no-load and memory load trials. Exp III (48 Ss) was similar to Exps I and II except that the CM task involved nonsense shapes that could probably be processed by either hemisphere. Introducing this concurrent nonverbal memory task did not reduce the recognition of either right- or left-ear CVs. Results indicate that the verbal nature of the concurrent task appears to be critical, as in previous visual laterality experiments. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive abilities and hemispheric lateralization in females following idiopathic precocious puberty.

Compared 12 right-handed adolescent females with a history of idiopathic precocious puberty (IPP) to 12 closely pair-matched normal controls of similar maturational status. All Ss were aged 13–20 yrs. Cognitive abilities were assessed by subtests of the WISC and Primary Mental Abilities Test, and by combination scales derived from these subtests. Brain hemispheric lateralization was measured by 2 dichotic listening tests. Results show that IPP Ss and controls did not differ in verbal abilities or in dichotic consonant–vowel discrimination. IPP was associated with lower spatial ability. It is concluded that pubertal maturation is associated with spatial but not verbal ability. Left-hemisphere functioning does not seem to constitute a mediating mechanism for this association but a slight weakness of right-hemisphere functioning is suggested by poor left-ear performance on the staggered spondaic word test. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric specialization and ear advantages in processing speech.

Reviews research on the hemispheric asymmetry model of relative ear advantages in the processing of auditory stimuli. Physiological studies of activation of the hemispheres in humans support left-hemisphere speech-processing specialization and contralateral sound field dominance. Electrophysiological studies in animals, effects of commissurotomy, hemispherectomy, and unilateral temporal lobe lesions on dichotic performance in humans, as well as stimulus dominance effects in intact Ss indicate that the assumption of ipsilateral sensory pathway suppression during competitive stimulation is unwarranted. Dichotic presentation is not necessary to produce a right-ear advantage (REA), and selective attention to one or the other ear frequently tends to alter the magnitude of the REA. A modified structural model that incorporates the effects of directed attention is proposed. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric laterality and memory bias for threat in anxiety disorder.

Examined auditory perceptual asymmetries and explicit memory biases for threat in patients with panic disorder and generalized anxiety disorder relative to healthy control Ss. They did not find a greater explicit memory bias for threat in the anxiety patients. However, explicit memory biases for threat were associated with perceptual asymmetry scores; patients with a greater right-ear (left hemisphere) advantage exhibited an explicit memory bias for threat material, whereas patients with a lower right-ear advantage displayed apparent cognitive avoidance of threat material. Memory for threat words was unrelated to perceptual asymmetry in healthy control Ss. These findings suggest that neuropsychological variables may partly determine the degree to which anxiety patients process threatening stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do tricyclic responders have different brain laterality?

A previous study showed that depressed patients who improved with tricyclic antidepressant medication had dichotic complex tones test results suggesting right-hemisphere dysfunction relative to nonresponders and controls (G. E. Bruder et al., 1990). A new sample of 68 depressed patients completed dichotic consonant-vowel (CV) and complex tones (CT) tests and then were treated with imipramine or placebo. A significant Ear?×?Test?×?Treatment?×?Response interaction was accounted for by significantly poorer left-ear accuracy for CVs among imipramine responders compared with nonresponders, placebo responders, and controls. CV left-ear accuracy was also significantly greater among placebo responders than placebo nonresponders; and controls. The results only partially replicate the prior study in that evidence of right-hemisphere dysfunction in tricyclic responders was seen for the CV test but not the CT test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)