Phased mirror tracing outcomes correlate with several hemisphericity measures

Recently, subjects, separated into two large groups by the Dichotic Deafness Test (DDT), a new brain laterality measure. These were significantly correlated with groups separated by two preference-based hemisphericity-type questionnaires, the Preference Questionnaire (PrefQ) and Polarity Questionnaire (PolQ). Here, Mirror-Tracing, another potential biophysical measure of hemisphericity earlier reported to be weakly correlated with laterality, was tested using 171 subjects, the DDT, and both questionnaires. No correlations between the DDT, PrefQ, and PolQ separation methods and Mirror Tracing outcomes were found until individuals identified as having left brain affect were removed from the population. Then, robust correlations appeared for the remaining right-affect subjects alone (n=82). These correlations became even higher when the left brain affect subjects that had been removed (n=89) were "phase corrected" from a contralateral to an ipsilateral connectivity for motor dominance and then returned to the sample (n=171). These Phased Mirror-Tracing (PMT) outcomes were also significantly correlated with 10 of the 11 statements of the PolQ. Thus, PMT joins the DDT as a second performance-based measure of laterality whose outcomes significantly correlated with those of preference-based hemisphericity questionnaires.     

Asymmetry questionnaire outcomes correlate with several hemisphericity measures

The asymmetry questionnaire segregated subjects (n=143) into two groups. These were significantly correlated with similar groups separated, not only by three new biophysical hemisphericity protocols (Dichotic Deafness Test, Phased Mirror Tracing, Best Hand Test), but also by two preference-type measures (polarity questionnaire, preference questionnaire). Each of the 15 asymmetry questionnaire statements was significantly correlated with the outcomes of these five laterality measures. This is the third questionnaire whose outcomes correlate with those of the new biophysical measures of hemisphericity.     

Corpus callosum size is linked to dichotic deafness and hemisphericity, not sex or handedness

Individuals differ in the number of corpus callosum (CC) nerve fibers interconnecting their cerebral hemispheres by about threefold. Early reports suggested that males had smaller CCs than females. This was often interpreted to support the concept that the male brain is more "lateralized" or "specialized," thus accounting for presumed male predominance in mathematics, as well as for aggressive behavior. Ultimately, meta-analyses of these many reports found no significant overall sex differences in inter-cerebral information carrying capacity. Here, using quantitative MRI, we found the midline CC area of 113 subjects was significantly correlated, not with handedness or sex, but with dichotic deafness, and even more so with redefined hemisphericity, the latter accounting for over 19% of CC variability. That is, both dichotic hearing and right brain-oriented individuals of either sex had significantly larger CCs than dichotically deaf or left brain-oriented persons. Thus, current traditions of brain laterality and gender may benefit from revisions that include redefined hemisphericity.     

Cerebral dominance in aphasia recovery.

This investigation studied the patterns of ear preference of a group of 25 aphasic adults through the administration of two verbal dichotic tests and retests over a 2-month interval of time. These dichotic tests were a Dichotic Digits Test (DDT) and a Dichotic Animal Names Test (DANT). Schuell's short test of aphasia was given twice over this interval to assess language recovery. Results indicated that as aphasics improve in language, cerebral dominance becomes more firmly established in the right cerebral hemisphere. The data in this study tend to support a dominance shift hypothesis in the recovery of language after aphasia.     

Dichotic listening with forced attention in patients with temporal lobe epilepsy: significance of left hemisphere cognitive dysfunction

Fifty right-handed patients with focal temporal lobe epilepsy were administered a dichotic listening test with consonant-vowel syllables under non-forced, forced right and forced left attention conditions, and a neuropsychological test battery. Dichotic listening performance was compared in subgroups with and without left hemisphere cognitive dysfunction, measured by the test battery, and in subgroups with left and right temporal epileptic focus. Left hemisphere cognitive dysfunction led to more correct responses to left ear stimuli in all three attention conditions, and fewer correct responses to right ear stimuli in the non-forced attention condition. This was probably caused by basic left hemisphere perceptual dysfunction. Dichotic listening was less affected by a left-sided epileptic focus than by left hemisphere cognitive dysfunction. General cognitive functioning influenced dichotic listening performance stronger in forced than in non-forced attention conditions. Larger cerebral networks were probably involved in the forced attention conditions due to the emphasis on conscious effort.     

Hemispheric cognitive style: a comparison of three instruments

In this study, the author tested the reliability, concurrent validity, and predictive validity of three hemispheric cognitive style instruments: (a) the Preference Test (PT; R. Zenhausern, 1978), (b) the Polarity Questionnaire (PQ; B. E. Morton, 2002), and (c) the Wagner Preference Inventory II (WAPI II; R. F. Wagner & K. A. Wells, 1985). Participants were either teachers or teachers in training. The prediction criterion was in the area of teaching licensure. Scores on the PQ had extremely low reliability, and correlations with the PT and the WAPI II were not significantly different from zero. In addition, the PQ did not correlate with the licensure area. The author found that both the PT and the WAPI II had reasonable levels of reliability, and both instruments were able to explain a small percentage of the variance in the teaching licensure area. Using factor analysis of the PT, the author found a 7-factor structure, which suggests that hemispheric cognitive style might be decomposable into separate holist analytic and visual-verbal dimensions.     

Prediction of fine motor skills of children having language and speech disorders

Relationships between the fine motor skills and linguistic abilities of 37 developmentally delayed children, ages 5 to 9 yr., were studied using a battery of expressive and receptive language tests, a measure of fine motor performance, a dichotic listening test, and individual intelligence tests. While IQs and MAs were not related to fine motor skills, both expressive and receptive language test scores showed moderate to moderately high correlations, the highest single relationship being the Test for the Auditory Comprehension of Language. In concert with CAs, a dichotic right-ear test score, the Auditory Comprehension Test, predicted fine motor-skill indices substantially; R = .80. Strong relationships appear between linguistic and fine motor skills in an age group not previously investigated and at higher levels than reported in studies of infants and very young children. Dichotic results were abnormal in a majority of the children.     

Executive functions in dyslexia.

This study focused on executive functions in dyslexia. A group of 43 heavily-affected young dyslexics, divided into two groups based on the results of a receptive language test, and 20 non-dyslexic controls, were tested with a Dichotic Listening Test, the Stroop Color Word Test and the Wisconsin Card Sorting Test. The dyslexic subjects demonstrated significant impairment on all tasks, but with different patterns of impairment according to the subgrouping. The subgroups were equally impaired on the Dichotic Listening Test, but differed on the Stroop and the Wisconsin Tests. The data support a hypothesis suggesting executive problems in dyslexia, depending on receptive language skills.     

Executive Functions in Dyslexia

This study focused on executive functions in dyslexia. A group of 43 heavily-affected young dyslexics, divided into two groups based on the results of a receptive language test, and 20 non-dyslexic controls, were tested with a Dichotic Listening Test, the Stroop Color Word Test and the Wisconsin Card Sorting Test. The dyslexic subjects demonstrated significant impairment on all tasks, but with different patterns of impairment according to the subgrouping. The subgroups were equally impaired on the Dichotic Listening Test, but differed on the Stroop and the Wisconsin Tests. The data support a hypothesis suggesting executive problems in dyslexia, depending on receptive language skills.     

Line bisection-based hemisphericity estimates of university students and professionals: evidence of sorting during higher education and career selection

Recently, hemisphericity has been assessed by six intercorrelated methods. Here, one of these, the "Best Hand Test," a two-hand line bisection-based biophysical method relatively independent of language, culture, or education, was applied to the measurement of hemisphericity distributions within large groups. Entering university students (n=402) enrolled in three lower division courses were chosen as a reference population. Each of these classes contained about 56% left brain-oriented individuals. In contrast, mean student left-brain distributions in four specialized, upper level courses (n=180), ranged from 35 to 68%, suggestive of hemisphericity sorting. Even more pronounced hemisphericity distribution differences were found within university representatives of 15 professions (n=421) and within professional subspecialists (n=45). For example, of biochemists (n=18), 83% were left brain-oriented, while among astronomers (n=21), only 29% were. These results are of intrinsic interest, and demonstrate the capability of the Best Hand Test to estimate hemisphericity in large groups.     

Lateral asymmetry in subgroups of dyslexic children

It has been proposed that in examining hemispheric dominance in dyslexics, investigators must make a distinction between subtypes of the disorder. Using the Denver Reading and Spelling Test, 72 dyslexics were divided into three groups: dysphonetics, dyseidetics, and nonspecifics. Three measures of hemispheric dominance were administered: a dichotic listening test, a hemiretinal test with linguistic stimuli, and a hemiretinal test with spatial stimuli. Results indicated that the three subgroups of dyslexics did not differ from one another on measures of hemispheric dominance. Dyslexics, taken as a group, tended to show an exaggerated right ear advantage on the dichotic listening test, in comparison with that of controls. It was proposed that the dichotic listening test may be confounded by attentional deficits in the dyslexics.     

Age-related decrement in auditory selective attention

Young (n = 30), middle-aged (n = 32), and old (n = 28) adults repeated (shadowed) words presented to the left ear at 60 words per minute with and without distracter words presented to the other ear. Dichotic shadowing error rate increased with age. An attempt to eliminate the age effect by adjusting for age differences in monaural shadowing errors, fluid intelligence, and pure-tone hearing loss did not succeed. When the analyses were confined to subjects who made no monaural shadowing errors, dichotic shadowing errors still increased linearly with age. These results showed that there are selective-attention deficits in older adults that cannot be accounted for by the uncertainty of the target location.     

Complementarity of Linguistic and Prosodic Processes in the Intact Brain

Despite considerable speculation in the research literature regarding the complementarity of functional lateralization of prosodic and linguistic processes in the normal intact brain, few studies have directly addressed this issue. In the present study, behavioral laterality indices of emotional prosodic and traditional linguistic speech functions were obtained for a sample of healthy young adults, using the dichotic listening method. After screening for adequate emotional prosody and linguistic recognition abilities, participants completed the Fused Rhymed Words Test (FRWT; Wexler & Halwes, 1983) and the Dichotic Emotion Recognition Test (DERT; McNeely & Netley, 1998). Examination of the difference in ear asymmetries for these measures within individuals revealed a complementary pattern in 78% of the sample. However, the correlation between laterality quotients for the FRWT and DERT was near zero, supporting Bryden's model of "statistical" complementarity (e.g., Bryden, 1990).     

Electrographic correlates of lateral asymmetry in the processing of verbal and nonverbal auditory stimuli

A veraged evoked potentials (AEP) to verbal (digits) and nonverbal (clicks) auditory stimuli were recorded from left and right temporal leads in ten right-handed Ss. With dichotic presentation, there was no significant difference in accuracy of report of the clicks heard in each ear, but significantly more digits were identified correctly from the right ear than from the left. Dichotic verbal stimuli elicited AEP whose early components were of greater amplitude, and whose later components were of shorter latency, from the left hemisphere than from the right. No consistent latency or amplitude differences were observed between AEP from the left and right hemispheres when clicks were presented dichotically.     

The Role of Dichotic Listening Performance and Tasks of Executive Functions in Reading Impairment: A Discriminant Function Analysis

This study focused on the role of dichotic listening performance for the identification of reading impaired subtypes. Dichotic listening (DL), using verbal stimuli, has shown to be a valid measure of language lateralization. Usually, lateralization is estimated from the proportion of right ear over left ear accuracy during a free recall test procedure. However, it has been suggested that a more accurate estimate of laterality can be obtained by using a directed attention procedure. A sample of 43 reading disabled children of whom 18 showed signs of impaired language comprehension skills and 25 without language comprehension impairments, were compared to 20 age, and gender, matched controls on dichotic listening performance in both an unbiased free recall task and in a directed attention task using consonant-vowel syllables as dichotic stimuli. A laterality index was calculated for left and right ear stimuli reported during both the free recall condition and the attended ear-scores for the two directed attention conditions. Although both DL procedures yielded significant group differences, with a lower laterality score for the reading disabled compared to the controls, there was no main effect of DL-procedure or group × procedure interaction. Taken alone, DL performance could correctly classify 42% of the reading impaired samples, but together with other measures of executive functions, discriminant function analyses yielded 90.74% accuracy in classifying reading impaired children. The result indicates that DL together with tests of executive functions are valuable tools for assessment of reading impaired subjects.     

Fakeability and correlates of the perception and preference inventory

This paper reports three studies designed to look at the usefulness of the Perception and Preference Inventory (PAPI). The first study looked at the fakeability of the PAPI by asking one group to fake good, another to fake bad, and a third group to respond honestly. Just over hald of the items yielded significant differences between the three groups, with most differences being between the fake bad and control group. In the second study the PAPI was correlated with the Eysenck Personality Questionnaire. Extraversion-Introversion and to a lesser extent neuroticism was correlated with PAPI subscores, particularly the dimensions of work direction and work style. Five of the seven subscale scores from the PAPI were correlated with extraversion. In the third study the PAPI was correlated with the Baddeley Reasoning Test, which is itself correlated with many intelligence tests. There were very few significant correlations. Implications for the measurement of personality and individual differences in occupational and industrial settings are considered.     

Dichotic listening in college students who report auditory hallucinations

College students were placed in 2 groups, hallucinators and nonhallucinators, on the basis of their responses to a verbal hallucinations questionnaire. Both groups were given a consonant-vowel version of a Dichotic Listening Test under 3 conditions: nonforced, forced-right, and forced-left. When hallucinators were instructed to attend to the left ear stimuli (forced-left condition), they had fewer correct responses to right ear syllables than did nonhallucinators. This resulted in a left ear advantage for hallucinators. When nonhallucinators were instructed to attend to the left ear, they maintained a right ear advantage. Results suggest that auditory hallucinations in college students are associated with differences in hemispheric functioning.     

Auditory neglect after right frontal lobe and right pulvinar thalamic lesions

Auditory unilateral neglect or extinction to simultaneous stimulation is reported in a right-handed male with a lesion in the right frontal lobe and in the right thalamic pulvinar area. The patient was submitted to stereotactic thalamotomy for a post-traumatic intentional ataxia in the left extremities. He was subjected to repeated tests with dichotic listening to consonant-vowel syllables under three different attentional instructions. He was also tested monaurally with the same stimulus materials as used in the dichotic test. The results showed almost complete extinction of the left ear input during dichotic presentations, despite normal hearing when tested with audiometer screening. The left ear extinction effect was independent of instructions to attend to the left or right ear input. However, during monaural presentation, correct left ear reports increased to about 85%. The results are interpreted as showing an auditory attentional neglect caused by the right frontal and pulvinar lesions.     

The role of dichotic listening performance and tasks of executive functions in reading impairment: a discriminant function analysis.

This study focused on the role of dichotic listening performance for the identification of reading impaired subtypes. Dichotic listening (DL), using verbal stimuli, has shown to be a valid measure of language lateralization. Usually, lateralization is estimated from the proportion of right ear over left ear accuracy during a free recall test procedure. However, it has been suggested that a more accurate estimate of laterality can be obtained by using a directed attention procedure. A sample of 43 reading disabled children of whom 18 showed signs of impaired language comprehension skills and 25 without language comprehension impairments, were compared to 20 age, and gender, matched controls on dichotic listening performance in both an unbiased free recall task and in a directed attention task using consonant-vowel syllables as dichotic stimuli. A laterality index was calculated for left and right ear stimuli reported during both the free recall condition and the attended ear-scores for the two directed attention conditions. Although both DL procedures yielded significant group differences, with a lower laterality score for the reading disabled compared to the controls, there was no main effect of DL-procedure or group x procedure interaction. Taken alone, DL performance could correctly classify 42% of the reading impaired samples, but together with other measures of executive functions, discriminant function analyses yielded 90.74% accuracy in classifying reading impaired children. The result indicates that DL together with tests of executive functions are valuable tools for assessment of reading impaired subjects.     

The role of the left and right thalamus in language asymmetry: dichotic listening in Parkinson patients undergoing stereotactic thalamotomy

Fourteen patients with Parkinson's disease (rigidity and unilateral tremor as main symptoms) were treated with stereotactic thalamotomy. The operation was performed in either the left or right ventrolateral thalamus, depending on which hand (or foot) was most affected with tremor. Nine patients were operated on the left side and four on the right side. All patients were tested for asymmetry of language functioning with dichotic presentations of consonant-vowel (CV) syllables. The patients had to indicate which of the two syllables he/she heard on each trial. Dichotic listening was performed before and after the operation, as well as during electrical stimulation of the VL nucleus just before the lesion was carried out. The results revealed essentially three things: an overall reduced right ear advantage (REA) in the patient group compared to what is known from studies of healthy individuals; an increase in REA during left-sided stimulations; and a marked reduction in REA after left-sided lesions. It is concluded that the present data support the notion put forward by Ojemann (e.g., 1975) of a lateralized activating gating mechanism in the left VL nucleus that gates access for language information to the appropriate cortical areas. The gating mechanism seems to be activated by stimulation, and deactivated after lesions. Dichotic listening may thus be a heuristic instrument in assessment of language functions in Parkinson patients.