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PubMed1987

The measurement of foot preference.

Foot preference has been given only superficial attention in studies of hemispheric lateralization, although it has potential utility for predicting hemispheric dominance. This paper reports the development of a reliable (alpha = 0.89) 11-item behavioral inventory of foot preference. Since footedness and handedness are only partially related, both must be measured reliably to identify individuals who have a consistent right or left side preference. It has yet to be determined whether footedness or handedness has the stronger relationship to other aspects of cerebral lateralization and whether both measures together predict lateralization better than one of them alone.

Brain↗
PubMed1989

Perceptual asymmetry on the dichotic fused words test and cerebral speech lateralization determined by the carotid sodium amytal test.

The rhymed fused dichotic words test was administered to 61 epileptic patients whose lesions were atrophic and predominantly unilateral. Subjects were categorized according to the side of speech representation, as determined by intracarotid sodium Amytal injection (left-hemisphere representation, 35 subjects; right-hemisphere representation, 4 subjects; bilateral representation, 22 subjects). Results indicated that 33 of the patients with left-hemisphere speech representation obtained right-ear advantages, and all four of the patients with right-hemisphere speech representation obtained left-ear advantages. The distribution of scores for patients with bilateral speech straddled the zero ear-advantage point, but overlapped both of the other two groups to some extent. Neither handedness, familial handedness, sex, nor side of epileptogenic focus had any significant effect on the observed asymmetries. It was also found that stimulus dominance effects have an important influence on the results, and must be taken into account in the interpretation of dichotic listening asymmetries. It is concluded that this test yields valid estimates of speech lateralization; it is also apparent that the magnitude of ear advantage may be an important variable insofar as the more extreme asymmetries appear to be exclusively associated with speech dominance of the contralateral hemisphere, whereas small-magnitude asymmetries are often associated with bilateral speech representation.

Adult↗
PubMed1989

Verbal and nonverbal auditory processing among left- and right-handed good readers and reading-disabled children.

Cerebral lateralization of left- and right-handed good readers and left- and right-handed reading disabled was examined with a sample of 60 children who ranged in age from 7-13 years via a dichotic selective attention task (free recall, directed left, directed right) using consonant-vowel (CV) and tonal stimuli. Several ANOVAs were conducted to evaluate gender, reader group, handedness, and stimuli effects of left- and right-ear reports across dichotic conditions. Results indicated males outperformed females across stimuli and conditions regardless of handedness and all subjects recalled more tonal stimuli than CV stimuli. More importantly, the expected REA (left hemisphere processing) was found for CV stimuli only by right-handed good readers across all three dichotic conditions. The left-handed good readers and left-handed reading-disabled children were left ear (LE) dominant in free recall and in the directed left condition, but were right ear (RE) dominant in the directed right condition. Conversely, right-handed reading-disabled children produced a REA during free recall and directed right conditions, but were LE dominant in the directed left condition. In contrast, a significant LEA (right hemisphere processing) was found for tonal stimuli across all dichotic conditions for all four groups. These findings lend support to the hypothesis that attentional factors have a greater influence on auditory processing of verbal than nonverbal stimuli for various groups of children and also suggest reversed or bilateralized processing abilities for language in strongly left-handed children with sinistral relatives.

Attention↗
PubMed1989

Left and right-handed dyslexic boys: an empirical test of some assumptions of the Geschwind-Behan hypothesis.

Twenty-six dyslexic boys (13 left-handers and 13 right-handers) were tested for hemispheric asymmetry with dichotic listening (DL) and a visual half-field test (VHF). The purpose of the study was an empirical test of the Geschwind-Behan [Proc. natn. Acad. Sci. USA 79, 5097-5100, 1982] hypothesis of a difference in hemispheric asymmetry between left- and right-handed dyslexic boys. Following Geschwind and Behan, left-handedness and dyslexia are caused by a common factor affecting the development of the left hemisphere in utero which results in a right hemisphere dominance. As a consequence, handedness but not language is shifted to the right hemisphere. We therefore predicted that left-handed dyslexics should be superior to right-handed dyslexics on visuospatial tasks, but perform similar to right-handers on verbal tasks. The results revealed a significant right ear advantage (REA) in both groups during a dichotic listening test to verbal stimuli. The left-handed group was however superior to the right-handed group in recognition of visuo-spatial stimuli presented in the left half-field in a visual half-field test. It is concluded that the results provide some, although weak, support for the Geschwind-Behan hypothesis.

Adolescent↗
PubMed1990

Immune and autoimmune diseases in dyslexic children.

One hundred and five dyslexic and 105 control children were compared for frequency of immune diseases, autoimmune diseases, and non-right-handedness in the light of the Geschwind-Behan (1982) "testosterone hypothesis". The results showed significantly more immune- and autoimmune-diseases int he dyslexic group. There were no differences between the groups in the frequency of non-right-handedness. There were no interactions with gender, although there were more non-right-handed boys than girls in the total sample. Mothers of children who were dyslexic experienced significantly more negative life-events during pregnancy, they also experienced the pregnancy as more difficult, and they had more spontaneous abortions. In conclusion, the results support some aspects of the "testosterone hypothesis", but they also point to a more complex pattern of interaction between the factors that still remain unanswered.

Adolescent↗
PubMed1996

Differences between Caucasians and American Indians on the cognitive laterality battery.

Caucasians scored significantly better than American Indian college students on verbal-sequential tests, but not on visuospatial tests, of Gordon's Cognitive Laterality Battery (CLB). Caucasians scored more right-biased than American Indians on the Edinburgh Handedness Inventory (EHI). The effects of percentage of Native American ancestry, strategy employed to recall serial sounds, bilingualism, familial sinistrality and handedness laterality on test performance were also analyzed. Results are consistent with hypotheses drawn from Annett's genetic theory of human laterality, if frequency distributions for the hypothesized rs+ gene are assumed to vary across the parent populations from which the samples were drawn.

Acoustic Stimulation↗
PubMed1996

Asymmetries in intermanual transfer of maze learning in right- and left-handed adults.

This study examined asymmetries in transfer learning on a finger maze as a function of handedness, hand at acquisition and maze orientation at transfer. In both handedness groups, right-hand acquisition enhanced opposite hand performance on an identical and a vertically reversed maze at transfer, relative to a mirror-reversed maze; left-hand acquisition, in turn, enhanced opposite hand transfer on the spatially reversed mazes relative to the identical maze. The findings suggest that different strategies (i.e. verbal versus spatial/motoric) come into play in maze learning depending on the hand used at acquisition (right versus left, respectively) rather than on overall hand dominance.

Adult↗
PubMed1996

Structure, functional and cerebral asymmetry: in vivo morphometry of the planum temporale.

Using high-resolution magnetic resonance (MR) imaging, the normal left-right asymmetry of the planum temporale (PT) can be quantified accurately and reliably in the intact human brain. The following main results have emerged from MR measurements of individual direction and degree of PT asymmetry. (1) Normal left-handers are less left-lateralized than normal right-handers, without significant gender effects. This confirms a structural-functional correlation in cerebral asymmetry. (2) The aforementioned handedness difference in PT asymmetry is also found in pairs of normal monozygotic twins discordant for handedness. Thus, structural brain asymmetry may not be genetically determined. (3) Whereas right-handed patients with developmental deficits of phonological processing have been reported to show decrease PT asymmetry, musicians with perfect pitch display exaggerated leftward asymmetry. Thus, increasing leftward asymmetry of auditory-related cortices covering the PT may be correlated with the processing capacity for certain auditory features. Studies of the PT as a structural marker of cerebral asymmetry will continue to contribute to a better understanding of the phylogeny and ontogeny of laterality.

Cerebral Cortex↗
PubMed1996

Structural asymmetries in the human forebrain and the forebrain of non-human primates and rats.

Possible asymmetries of the following structures were studied: volumes of total human hemispheres, cortex and white matter volumes in post-mortem- (unknown handedness) and living brains (male right-handers); volumes of the rat primary visual cortex, its mon- and binocular subfields, its layer iv and the density of myelinated fibres in layer iv; transmitter receptor densities (NMDA, AMPA, kainate and GABAA receptors) in sensorimotor regions of the rat cortex; volume of the motor cortex and the 3D-extent of the central sulcus in the post-mortem- (unknown handedness) and living human brain (male right-handers); petalia of the hemispheres in human (male right- and left-handers) and chimpanzee brains. Histological, MRI and receptor autoradiographic techniques were used. With the notable exceptions of the transmitter receptors and the total primary visual cortex in rats and the hemispheres in chimpanzees, which do not show any significant directional asymmetry, all other parameters studied are asymmetrically distributed between the right- and left hemispheres. The regional distribution pattern and the degree of asymmetry of frontal and occipital petalia in living human brains differ between right- and left-handers.

Animals↗
PubMed1994

Vision influences paw-preference in mice.

We studied the influence of vision on the expression of handedness in mice. In one experiment we submitted adult mice that had an opaque scleral contact lens fitted to one eye, to a paw-preference testing procedure. When the eye was occluded before training, the animals showed a clear preference for the paw ipsilateral to the open eye; however, we could not induce a shift in a previously determined, natural, paw-preference when the lens was placed over the eye ipsilateral to the spontaneously preferred paw; these results indicate that vision plays a role in the animal's choice of a paw during the learning phase of the paw-preference test. In a second experiment adult mice that had been subjected to unilateral eye removal at birth, underwent the same test. The enucleation did not appear to influence handedness with respect to both direction and strength. The latter result--we propose--reflects a reorganization of the visual system induced by neonatal enucleation.

Animals↗
PubMed1994

Anatomical-behavioral relationships: corpus callosum morphometry and hemispheric specialization.

We obtained midsagittal measures of the corpus callosum in 60 healthy young adults (right-handed and left-handed males and females), and examined whether individual differences in anatomical measures of callosal connectivity are related to behavioral laterality measures in the same subjects. In an attempt to tap functionally-distinct callosal "channels", four behavioral laterality tasks were used that differed in sensory modality (visual, auditory, tactile) and/or level of cognitive processing (sensory versus semantic). In addition, the tasks had both intrahemispheric and interhemispheric conditions. Sex differences were found for measures of the posterior body (i.e. isthmus) of the corpus callosum, which, in turn, interacted with handedness. In contrast, only handedness effects were found for the behavioral laterality measures. Anatomical-behavioral correlations did not disclose relationships between callosal size and performance on task conditions requiring sensory interhemispheric integration or transfer. Instead, the correlational findings are consistent with the view that the corpus callosum participates in such higher order "control" functions as the support of bilateral representation of language, functional interhemispheric inhibition, and the maintenance of hemispheric differences in arousal. This is consistent with the finding that regional callosal size is related to the number of small diameter fibers, which are presumed to interconnect homologous association cortices in the two hemispheres.

Adult↗
PubMedDate not supplied

Reversed temporal region asymmetries of P300 topography in left- and right-handed schizophrenic subjects.

The auditory P300 evoked potential was recorded in 36 subjects: left- (LH) and right-handed (RH) schizophrenic males and LH and RH normal controls. LH and RH normals showed no asymmetry in P300 scalp topography. LH and RH schizophrenics, however, showed lateralized asymmetries in temporal scalp regions: left < right P300 voltage asymmetry in RH schizophrenics and left > right P300 voltage asymmetry in LH schizophrenics. These data suggest that the schizophrenic pathology of P300 neural generators is lateralized according to handedness and provide the first evidence that LH and RH schizophrenics can be dissociated based on left-right voltage asymmetries in P300 topography. These findings further emphasize the need for control of handedness in P300 studies of schizophrenia.

Acoustic Stimulation↗
PubMed1983

Asymmetry of perception in free viewing of chimeric faces.

We have devised a new free-vision task to index functional cerebral asymmetry for processing facial characteristics. Confirming its sensitivity to properties of lateralized hemispheric functions, left- and right-handers were clearly differentiated on this task with respect to several aspects of performance that conform with known differences between handedness groups in hemispheric asymmetry. Additionally, there were highly reliable and stable individual differences in perceptual asymmetries within handedness. Analyses of items in the task revealed that most of the differences between items in the asymmetries they elicited were random.

Brain↗
PubMed1990

An investigation of immune system disorder as a "marker" for anomalous dominance.

Geschwind and Galaburda (1987) proposed that immune disorder (ID) susceptibility, along with left handedness and familial sinistrality (FS), is a "marker" for anomalous dominance. The theory predicts lesser left lateralization for language processes, lessened left hemisphere abilities, and enhanced right hemisphere abilities. We assessed language laterality (dichotic consonant vowel task) and performances on spatial and verbal tasks. Subjects were 128 college students. The factors of handedness, sex, FS, and immune disorder history (negative or positive) were perfectly counterbalanced. Left-handers were significantly less lateralized for language and scored lower than right-handers on the spatial tasks. Females scored lower on mental rotation than males, but performed comparably to males on the spatial relations task. The only effect of ID was by way of interaction with FS on both spatial tasks--subjects who were either negative or positive on both FS and ID status factors scored significantly higher than subjects negative for one but positive for the other factor. A speculative explanatory model for this interaction was proposed. The model incorporates the notion that FS and ID factors are comparably correlated, but in opposite directions, with hormonal factors implicated by other research as relevant for spatial ability differences. Finally, no support for the "anomalous dominance" hypothesis predictions was found.

Adult↗
PubMed1990

Women who excel on a spatial task: proposed genetic and environmental factors.

A "bent twig" model which incorporates Annett's genetic handedness theory with an environmental component predicted characteristics of college women likely to excel on a mental rotation task. Those likely to have the necessary combination of genetic potential and prior experiences are right-handed women with non-right-handed relatives who rate themselves high in spatial experiences. This subgroup significantly outperformed all other groups of right-handed women on the Vandenberg Mental Rotation Test. This study provides support for the view that family handedness and spatial experiences are important factors influencing mental rotation ability in women.

Adult↗
PubMed1990

Hemispheric asymmetries in attentional control: implications for hand preference in sensorimotor tasks.

Liepmann (1908) proposed that handedness reflects the greater capacity of one hemisphere to learn the execution of skilled movements. Although asymmetries in motor control are an important basis for hand asymmetries, recent studies have suggested that handedness may be determined by multiple factors. In the present study, we examine how attentional asymmetries may contribute to hand preferences. Right-handed subjects participated in a reaction time task in which they were given preliminary information about where a target stimulus would occur (selective attention) or which hand to use for responding (selective intention). Our findings indicate that these processes influence each other reciprocally and favor a state of optimal attentional and intentional preparation of the right hand. We suggest that these hemispheric asymmetries in attentional control contribute to hand preferences in certain sensorimotor tasks.

Adult↗
PubMed1976

Sex differences in patterns of EEG asymmetry.

This paper reports three studies showing sex differences in EEG asymmetry during self-generated cognitive and affective tasks. In the first experiment, bilateral EEG, quantified for alpha on-line, was recorded from right-handed subjects while they either whistled, sang or recited lyrics of familiar songs. The results revealed significant asymmetry between the whistle and talk conditions only for subjects with no familial left-handedness and, within this group, only for females and not for males. In the second experiment, bilateral EEG was recorded while right-handed subjects (with no familial left-handedness) self-induced covert affective and non-affective states. Results revealed significantly greater relative right-hemisphere activation during emotion versus non-emotion trials only in females; males showed no significant task-dependent shifts in asymmetry between conditions. The third experiment was designed to test the hypothesis that females show greater percent time asymmetry than males during biofeedback training for symmetrical and asymmetrical EEG patterns. Results confirmed this prediction as well as indicating that females show better control of such asymmetrical cortical patterning. These findings provide new neuropsychological support for the hypothesis of greater bilateral flexibility in females during self-generation tasks.

Affect↗
PubMedDate not supplied

Slow potentials preceding vocalisation.

Twenty-four subjects equally represented by males and females, and left- and right-handers, had slow potentials recorded prior to vocalisation of the same word 25 times ('Yes'), or a different word every sweep, chosen by the subject 5. Negativity on the scalp preceding generated words came earlier than preceding repetitions. Asymmetry in EEG was dependent on handedness, and occurred frontally in females, centrally in males. It is suggested that task-related differences in slow potentials preceding speech, and asymmetries associated with handedness, provide evidence that these potentials are not irretrievably contaminated by movement and respiratory artefacts.

Dominance, Cerebral↗