Hemispheric Processing Deficits in Patients with Paranoid Schizophrenia

The purpose of the present study was to investigate hemispheric deficits in individuals with paranoid schizophrenia on four kinds of tasks: dichoptic viewing tasks involving verbal and nonverbal visual stimuli, and dichotic listening tasks involving verbal and nonverbal auditory stimuli. As dependent measures, both accuracy and speed of (correct) responding were measured. The sample recruited for this study consisted of 18 patients with paranoid schizophrenia, 15 outpatients with anxiety disorders, and 20 controls with no history of psychiatric disorders. Results indicated that, relative to the controls, the paranoid schizophrenic patients were less accurate and less efficient on auditory-verbal tasks requiring right hemisphere processing. Unlike the controls, the paranoid schizophrenic patients manifested a lateralized left hemisphere advantage.     

Hemispheric processing deficits in patients with paranoid schizophrenia

The purpose of the present study was to investigate hemispheric deficits in individuals with paranoid schizophrenia on four kinds of tasks: dichoptic viewing tasks involving verbal and nonverbal visual stimuli, and dichotic listening tasks involving verbal and nonverbal auditory stimuli. As dependent measures, both accuracy and speed of (correct) responding were measured. The sample recruited for this study consisted of 18 patients with paranoid schizophrenia, 15 outpatients with anxiety disorders, and 20 controls with no history of psychiatric disorders. Results indicated that, relative to the controls, the paranoid schizophrenic patients were less accurate and less efficient on auditory-verbal tasks requiring right hemisphere processing. Unlike the controls the paranoid schizophrenic patients manifested a lateralized left hemisphere advantage.     

Neuropsychological Deficits in Relation to Symptoms of ADHD: Independent Contributions and Interactions

Twelve children with and without Down syndrome (DS) performed eight subtests of an apraxia battery to determine under what conditions children with DS had difficulty performing representational and nonrepresentational gestures. Participants with DS also completed a dichotic listening test. Participants with DS performed just as well as control participants on all aspects of the apraxia battery except a subtest in which they were required to pantomime tool use from verbal instruction. This suggests that children with DS have difficulty generating an action from memory following verbal instruction. Given the sufficient context or visual demonstration, children with DS performed similar to the other participants. As well, there was a great deal of within-group variability for dichotic listening ear advantage. Participants with a greater left ear advantage on the dichotic listening test committed more errors on an imitation test that also included a verbal component than participants with a greater right ear advantage.     

Speech perception and motor control in children with Down syndrome.

Twelve children with and without Down syndrome (DS) performed eight subtests of an apraxia battery to determine under what conditions children with DS had difficulty performing representational and nonrepresentational gestures. Participants with DS also completed a dichotic listening test. Participants with DS performed just as well as control participants on all aspects of the apraxia battery except a subtest in which they were required to pantomime tool use from verbal instruction. This suggests that children with DS have difficulty generating an action from memory following verbal instruction. Given the sufficient context or visual demonstration, children with DS performed similar to the other participants. As well, there was a great deal of within-group variability for dichotic listening ear advantage. Participants with a greater left ear advantage on the dichotic listening test committed more errors on an imitation test that also included a verbal component than participants with a greater right ear advantage.     

Lateralized hemisphere activity in relation to personality and degree course

Personality dimensions of Psychoticism (P), Extraversion (E) and Neuroticism (N) were related to multiple measures of lateralized hemispheric processing in order to test the predictions of right hemisphere overactivation in E, right hemisphere underactivation in N, and left hemisphere under- activation/overactivation in P. It was also predicted that architecture students would be characterized by right hemisphere activation and language students by left hemisphere activation. Lateral eye movements, verbal and nonverbal dichotic listening tasks, and Block Design and Digit Span subtests of the WAIS were assessed in 43 undergraduates, together with personality and degree course. High P scores were characterized by fewer rightward eye movements and hence reduced left hemisphere activation, while high N scores were characterized by poorer Block Design and superior Digit Span performance. These results which indicate a relationship between Psychoticism and left hemisphere underactivation are in conflict with the finding of Raine and Manders (1988) (Br. J. Clin. Pschol. In press) overactivation in those with high schizoid personality scores, a discrepancy which may be resolved by the notion that P reflects a different form of psychosis-proneness to other schizoid scales.     

Neuropsychological assessment of learning disabilities: a discriminant analysis

The neuropsychological test scores of 23 learning disabled children were compared with those of a matched population of normal children in the 9-1 to 13-1 age range. All children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R), a dichotic listening task involving both free and directed recall conditions, a handedness inventory, the Tactile Performance Test and the Category Test from the Halstead-Reitan Neuropsychological Test Battery. A multivariate analysis of variance resulted in a significant separation between groups (p less than .001) using these procedures. A stepwise discriminant function analysis revealed that both of the directed dichotic tasks contributed the most of all 13 measures to the significant group separation. In addition, other cognitive tasks found to discriminate normal from learning disabled children include general verbal processes, concept formation, and tactile memory. These findings suggest that the directed dichotic listening procedure and the WISC-R Verbal IQ measure are reasonably valuable clinical tools in the classification of learning disabilities.     

Smoking reduces language lateralization: a dichotic listening study with control participants and schizophrenia patients

Schizophrenia has been associated with deficits in functional brain lateralization. According to some authors, the reduction of asymmetry could even promote this psychosis. At the same time, schizophrenia is accompanied by a high prevalence of nicotine dependency compared to any other population. This association is very interesting, because sex-dependent effects of smoking in auditory language asymmetries have been reported recently, and the verbal domain is also one major focus in cognitive deficit studies of schizophrenia. Thus, the altered laterality pattern in schizophrenia could, at least in part, result from secondary artefacts due to smoking rather than being a pure cause of the disease itself. To test this hypothesis, the present study examined auditory language lateralization in 67 schizophrenia patients and in 72 healthy controls in a phonemic and an emotional dichotic listening task. Our findings replicate previous research, in that smoking reduces language lateralization in men in phonemic dichotic listening. In addition, we show that smoking also reduces laterality in women in the emotional dichotic listening task. Thus, smoking alters phonemic and emotional language asymmetries differentially for men and women, with a stronger effect for men in the left hemisphere phonemic task, and a stronger effect for women in the right hemisphere emotional task. Together, these findings point towards an effect of smoking which is possibly independent of sex and hemisphere. Importantly, by testing equal numbers of smoking and non-smoking patients and controls, we found no schizophrenia-associated asymmetry effect. Possible neurobiological mechanisms with which smoking may alter auditory microcircuits and thereby diminish left-right differences are discussed.     

Pharmacological effects on lateralized behavior

Sixteen student volunteers were administered a placebo and 50 mg. of chlorpromazine in tablet form, on separate occasions, two hours before testing. The three tests measured dichotic listening performance, lateral eye movements while answering questions about spatial location and verbal meaning, and lateralized facial expression while relating pleasant and unpleasant life incidents. Results showed that chlorpromazine increased the number of trials showing an ear advantage in dichotic listening. Chlorpromazine reduced lateral and increased vertical eye movements in response to the questions about spatial location and verbal meaning. Under the placebo both negative and positive emotions were expressed more in the left face. Although chlorpromazine did not affect this lateralization of negative emotions, the expression of positive emotions occurred equally often on the two sides of the face under chlorpromazine. Results may be related to an effect of chlorpromazine on the asymmetrical dopamine pathways of the brain. It is suggested that the findings may be related to a left hemisphere deficit in schizophrenia.     

Dichotic listening in children: age-related changes in direction and magnitude of ear advantage

Children between the ages of 5 and 12 years were tested with dichotic listening tests utilizing single syllable words and random presentations of digits. They produced a higher prevalence of left ear dominance than expected, especially among right-handed children when tested with words. Whether more children demonstrate the LEA because of right hemisphere dominance for language or because there is less stability in ear advantage direction at younger ages cannot be fully resolved by this study. When ear advantages were measured by subtracting each child's lower score from the higher score without regard to right or left direction, an age-related trend toward lower measures of ear advantage was evident. This trend was greater for dichotic words than for dichotic digits. Structural factors that may be related to these results and possible influences of attention and verbal workload on the two kinds of dichotic stimuli are discussed.     

An experiential avoidance conceptualization of depressive rumination: Three tests of the model

This study examined an experiential avoidance conceptualization of depressive rumination in 3 ways: 1) associations among questionnaire measures of rumination, experiential avoidance, and fear of emotions; 2) performance on a dichotic listening task that highlights preferences for non-depressive material; and 3) psychophysiological reactivity in an avoidance paradigm modeled after the one used by Borkovec, Lyonfields, Wiser, and Deihl (1993) in their examination of worry. One hundred and thirty-eight undergraduates completed questionnaire measures and participated in a clinical interview to diagnose current and past episodes of depression. Of those, 100 were randomly assigned to a rumination or relaxation induction condition and participated in a dichotic listening task, rumination/relaxation induction, and depression induction. Questionnaire measures confirmed a relationship between rumination status and avoidance; however, no significant effects were found in the dichotic listening task. Psychophysiological measures indicated no difference in physiological response to a depression induction among high ruminators (HR). However, low ruminators (LR) in the relaxation condition exhibited a larger IBI response than LR in the rumination condition. Overall, these results provide partial support for an avoidance conceptualization of depressive rumination. Implications of these findings are discussed.     

Handedness and sex differences in hemispheric asymmetry

A study was designed to assess the contributions of the factors of sex and familial history to cerebral dominance, where cerebral dominance was inferred from laterality on a dichotic listening task. The 144 subjects were selected from a larger sample on the basis of handedness, sex, and familial history of sinistrality, and tested on a task involving the dichotic presentation of CV syllables. Analysis of the data indicated that in female subjects, the presence of familial sinistrality increased the likelihood that they present atypical left-ear superiorities, while in males the converse was the case. Moreover, there was a significant sex difference overall, such that males were more clearly lateralized than females. A review of other dichotic listening studies provided support for the reliability of this sex difference for dichotic tasks using verbal material. A review of the clinical literature indicated that the hypothesis of a sex difference is at least tenable and merits further investigation. However, the possibility that there is a sex difference in the cognitive strategy used in dichotic listening cannot be ruled out.     

Right hemisphere comprehension of verbs in patients with complete forebrain commissurotomy: Use of the dichotic method and manual performance

The paradigm of dichotic listening was used to investigate verbal comprehension in the right, so-called “nonverbal,” hemisphere. Verbal commands were presented to the right and left ears in the simultaneous (dichotic) paradigm. There were striking instances, especially when the left hemisphere was occupied with some extraneous task, in which the right hemisphere understood the verbal command and executed the appropriate motor responses. In those instances the left hemisphere gave no overt response. Although the left hemisphere was usually dominant, it can be nevertheless concluded that not only can the right hemisphere understand verbal commands but can also express itself manually by executing actions more complex than object retrieval or pointing. As has been known for some time, the blockage of the ipsilateral pathway seems so complete during dichotic listening in the commissurotomy patient that there is no report of the words in the left ear—only of those presented to the right. At the same time there is normal report when words are presented to the left ear alone. It was found in the present study, however, that this model is too simple and only applies to the verbal response paradigm of dichotic listening. Under circumstances of dichotic presentation where the stimulus in the left ear (ipsilateral pathway) is necessary or important to the left hemisphere for completing a task, words from both pathways are reported. One may conclude that there exists a gating mechanism in each hemisphere that controls the monitoring of each auditory pathway and the degree of ipsilateral suppression.     

Are creativity and schizotypy products of a right hemisphere bias?

Prior research has shown associations between higher creativity (e.g., semantic association, verbal fluency), higher schizotypy (e.g., magical ideation), and relatively stronger right hemisphere laterality measures--when each of the three pairings has been studied individually. Our prior study related creativity and schizotypy to signal detection theory response criterion aspects of laterality. The present study attempted to integrate findings regarding these three constructs and to replicate the signal detection theory laterality results by providing measures of all three constructs in a within subjects design. Participants were 60 undergraduates who completed a test battery including two measures of creativity, three measures of schizotypy, a lateralized lexical decision task, and a dichotic listening task. Results are consistent with individual differences in creativity and schizotypy being partly related to a response criterion favoring right hemisphere, possibly nonconscious, processing. Dichotic listening results revealed a strong association of better right hemisphere (left ear) localization ability and creativity.     

Sex differences in dichotic listening

The present study quantified the magnitude of sex differences in perceptual asymmetries as measured with dichotic listening. This was achieved by means of a meta-analysis of the literature dating back from the initial use of dichotic listening as a measure of laterality. The meta-analysis included 249 effect sizes pertaining to sex differences and 246 effect sizes for the main effect of laterality. The results showed small and homogeneous sex differences in laterality in favor of men (d=0.054). The main effect of laterality was of medium magnitude (d=0.609) but it was heterogeneous. Homogeneity for the main effect of laterality was achieved through partitioning as a function of task, demonstrating larger asymmetries for verbal (d=0.65) than for non-verbal tasks (d=0.45). The results are discussed with reference to top-down and bottom-up factors in dichotic listening. The possible influence of a publication bias is also discussed.     

Hemispheric dominance, dichotic listening and lateral eye movement behaviour

Abstract.— Because lateral corrective eye movements have been shown to influence the results of the dichotic listening test, it was supposed that differences in the scoring on this test by right and left eye movers could be found. Only in the entire group of 22 right handed subjects and in the subgroup of 8 right eye movers a significant right ear superiority was found. In the left mover group (14 subjects) right ear superiority in dichotic listening was not significant. These results are interpreted in terms of possible interhemispheric differences in the level of "activity", facilitating or hampering perception of verbal material in the contralateral ear.     

Unilateral forced nostril breathing affects dichotic listening for emotional tones

Unilateral forced nostril breathing (UFNB) through the left nostril is associated with enhanced spatial abilities, whereas UFNB through the right nostril is associated with enhanced verbal abilities. However, the effects of UFNB on standard tasks of laterality (e.g., dichotic listening) are unknown. This study employed dichotic listening for word targets, which typically exhibits a right ear advantage (REA), and dichotic listening for emotional targets, which typically exhibits a left ear advantage (LEA). Participants were asked to breathe either through their dominant nostril (congruent UFNB) or to breathe through their non-dominant nostril (incongruent UFNB) for the entire testing session. There was a significant three-way interaction between the type of dichotic listening task, nostril dominance, and nostril assignment, with the expected REA for word targets and the expected LEA for emotional targets-with one exception. Right nostril dominant participants assigned to the congruent condition exhibited an LEA for emotional targets (p < .05). The other three groups exhibited the expected LEA/right hemisphere advantage for the detection of emotional targets and all groups exhibited the expected REA/left hemisphere advantage for detection of word targets. As such, possible bias induced by tactile stimulation of the contralateral face cannot account for these results. Thus, our data are consistent with a selective enhancement of right hemispheric lateralized functions by right nostril UFNB.     

Stimulus-dominance effects and lateral asymmetries for language in normal subjects and in patients with a single functional hemisphere

The assessment of language laterality by the dichotic fused-words test may be impaired by interference effects revealed by the dominant report of one member of the stimuli-pair. Stimulus-dominance and ear asymmetry were evaluated in normal population (48 subjects of both sex and handedness) and in 2 patients with a single functional hemisphere. Results show that in normals the number of stimulus-dominated responses is five times higher than in patients, and is negatively correlated to the index of laterality. It is suggested that dichotic stimuli may interfere one with another during the subcortical acoustic processing and at cortical level, when competing for verbal output. Subcortical interference accounts for stimulus-dominance in the single-hemisphere patients. In normal subjects, the dichotic discrimination is disturbed mainly during the hemispheric cross-talk needed for the oral-verbal processing of dichotic inputs. The frequency of 'interhemispheric' interference, as well as the extents of ear asymmetry, may both depend on differences in the processing stage of the competing inputs, and then they may be influenced by differential verbal skills of LH and RH. Very unequal levels of verbal analysis of the dichotic stimuli may hinder reciprocal interference during the hemispheric cross-talk thus yielding large ear asymmetries associated to small dominance effects.     

Consonant-vowel lateralization in dyslexic children: deficit or compensatory development?

Two studies with the same subjects examined dyslexic children's puzzling superiority in forced left ear (LE) dichotic recall with consonant-vowel (CV) combinations. Thirty dysphonemic dyslexics were compared to 30 age-matched and 30 younger reading-matched normal readers. The children were tested in directed attention dichotic listening and in pseudoword decoding, word recognition, reading comprehension, spelling, arithmetic, and general intelligence (IQ). Failure to replicate the LE effect in the first experiment or in free-recall trials suggests its probable origin in aberrant attention/arousal rather than in deviant verbal lateralization. Experiment two replicated the superior LE effect in comparison to both control groups but also found the dyslexics poorer at the right ear (RE). Laterality coefficients confirmed that the dyslexics were more weakly lateralized. Corrections for stimulus dominance revealed that the uncorrected scores (1) concealed the extreme difficulty of the task and (2) obscured floor effects in the LE performance of the normals. Correlations suggest cautiously that CV lateralization may be associated inversely with reading comprehension and word decoding in the dyslexics and normal readers. The results provide mild support for the hypothesis that weak attentional lateralization for CVs in dyslexia may result from the precocious development of posterior right hemisphere attentional systems in compensation for presumed posterior left hemisphere lesions. No support was found for the competing hypothesis that such weak lateralization may be a component of the dyslexics' primary, correlated, or secondary deficit symptomatology.     

Predictors of therapeutic response to treatments for depression: a review of electrophysiologic and dichotic listening studies

There are few clinical or biologic predictors of response to treatments for depression. This article reviews growing evidence that electrophysiologic and neurocognitive measures of brain function may be of value as predictors of therapeutic response to antidepressants. Initial studies using dichotic listening, quantitative electroencephalography, or event-related brain potential measures have found differences between treatment responsive and nonresponsive subgroups of depressed patients. The neurophysiologic basis for these differences and the potential clinical utility of electrophysiologic and dichotic predictors of treatment outcome remain to be determined in future studies.     

Reduced lateralization in verbal dichotic listening in adolescent psychopaths

One possible explanation for previous findings of abnormal linguistic processing in psychopaths is that they are less lateralized for verbal processes. This study tests the hypothesis that adolescent psychopaths show evidence of reduced lateralization on a verbal dichotic listening task. Four self-report and behavioral measures of psychopathy were used to define psychopathy using cluster analytic techniques in 40 juvenile offenders aged 13 to 18 years. Psychopaths were found to have reduced ear asymmetries relative to nonpsychopaths, a result indicating reduced lateralization for verbal material. The effect does not appear to be mediated by group differences in age, ethnic background, IQ, overall performance, left-handedness, selective attention to one ear, or interhemispheric transfer deficits. This result suggests that the previous finding by Hare and McPherson is robust, provides some preliminary validity for the assessment of psychopathy before age 18, and indicates initial support for the utility of cluster analytic techniques in the assessment of psychopathy.