Morphologic Cerebral Asymmetries and Handedness

Foundas, Anne L.; Leonard, Christiana M.; Heilman, Kenneth M.

doi:10.1001/archneur.1995.00540290091023

Cited by 161 publications

(21 citation statements)

References 53 publications

(3 reference statements)

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“…The planum temporale has been considered one center of activity for the adult N100m [9,13,14]. N100m source asymmetry might be concordant with anatomical data showing excesses of frontal and peri-rolandic cortex in the left hemisphere and of posterior parietal lobe in the right hemisphere [15][16][17]. According to Binder et al [17], larger frontal and peri-rolandic mass on the left side pushes the point of upward deflection of the sylvian fissure posteriorly and tilts the planum temporale back.…”

Section: Discussionmentioning

confidence: 72%

Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia

Heim

Eulitz²,

Elbert³

2003

NeuroReport

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The current study aimed at determining whether the deviance of hemispheric asymmetry in the auditory cortex of children with dyslexia is also evident in dyslexic adults.Ten adult dyslexic subjects and 10 normally literate controls were presented with the syllable [ba:] while event-related brain activity was recorded from both hemispheres using whole-head magnetoencephalography. In control subjects, the auditory N100m source was found to be asymmetrical with a more anterior localization in the right than in the left perisylvian cortex (di¡erence ¼ 0.78 cm). The N100 m dipoles in dyslexic adults did not exhibit the same interhemispheric asymmetry (di¡erence ¼ À0.06 cm). The results indicate that reduced hemispheric laterality of perisylvian regions in dyslexia persists into adulthood.

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Section: Discussionmentioning

confidence: 72%

Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia

Heim

Eulitz²,

Elbert³

2003

NeuroReport

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“…Since the AHR and AAR are major branches of the sylvian fissure, they are readily identifiable on sagittal MRI sections; therefore, the depths of these convolutions can be measured and asymmetries of the pars triangularis can be calculated. To learn if there are anatomic asymmetries of the pars triangularis, these convolutions were measured on sagittal volumetric MRI in a group of normal right-and left-handers (26). Results of our study demonstrated that whereas the right-handers had a significant leftward asymmetry of the pars triangularis, the left-handers were more anomalous.…”

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confidence: 82%

“…Because asymmetries of the frontal operculum have been more difficult to demonstrate than asymmetries of the planum temporale (13,(16)(17)(18) and given the recommendations of Witelson and Kigar (25) regarding measuring the intrasulcal cortical surface area of this region, we developed a method of measuring the pars triangularis on volumetric MRI scans (26). The pars triangularis constitutes a portion of Broca's area (Brodmann's area 45).…”

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confidence: 99%

“…Therefore, a rule-based system was devised to assure reliability in identifying the AHR and AAR. This system was based on the anatomy of the sylvian fissure and anterior branches (40,41) and used parameters described in recent publications (20,24,26). The Talairach and Tournoux (39) coordinate system provided a reliable method to confirm the location of the rami, since within a brain the AHR and AAR in the left and right hemispheres are located at approximately the same x-y coordinates.…”

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confidence: 99%

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Pars triangularis asymmetry and language dominance.

Foundas

Leonard

Gilmore

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

137

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The pars triangularis is a portion of Broca's area. The convolutions that form the inferior and caudal extent of the pars triangularis include the anterior horizontal and anterior ascending rami of the sylvian fissure, respectively. To learn if there are anatomic asymmetries of the pars triangularis, these convolutions were measured on volumetric magnetic resonance imaging scans of 11 patients who had undergone selective hemispheric anesthesia (Wada testing) to determine hemispheric speech and language lateralization. Of the 10 patients with language lateralized to the left hemisphere, 9 had a leftward asymmetry of the pars triangularis. The 1 patient with language lateralized to the right hemisphere had a significant rightward asymmetry of the pars triangularis. Our data suggest that asymmetries of the pars triangularis may be related to speech-language lateralization.Paul Broca (1) described eight right-handed patients who lost the facility of speech and were found to have left hemispheric lesions. Broca (1) thought that the left third frontal convolution, including pars triangularis, was critical for speech. Although subsequent studies have demonstrated that left-sided lesions restricted to the third frontal convolution are probably associated with only transient loss of speech (2, 3) lesions of the right third frontal convolution rarely produce any speech deficits. These observations suggest that although the left inferior frontal lobe appears to be important in speech production, other undamaged areas can either compensate or substitute for this area. Both cortical stimulation (4, 5) and functional imaging studies (6-9) have provided support for the role of the left inferior frontal lobe in speech production. Wernicke (10) demonstrated that a lesion in the posterior portion of the left superior temporal lobe produced a syndrome different from that described by Broca (1). Whereas Broca's patients lost the capacity to speak fluently but retained comprehension, Wernicke's patients retained the ability to speak fluently but were impaired at comprehending speech. Subsequently, morphological cerebral asymmetries in the posterior superior temporal speech region (planum temporale) were demonstrated on postmortem brains (11-15), with a predominant leftward asymmetry of the planum temporale. However, consistent asymmetries of the inferior frontal region have been more difficult to demonstrate on postmortem studies (13,(16)(17)(18). Therefore, the distinctive morphological asymmetries of the planum temporale have been thought to be the neuroanatomical substrate for speech and language. Furthermore, the planum temporale constitutes part of cytoarchitectonic areas TA and TB, which are auditory association cortices important in higher order processing of auditory language input. However, direct evidence supporting this structurefunction relationship has been lacking.With the advent of three-dimensional volumetric magnetic resonance imaging (MRI), in vivo quantitative analysis of the The publication costs of this ...

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“…In spite of a paucity of data, relationships between handedness and some structural brain asymmetries are implicated, particularly with regard to planum temporale asymmetries that are often reported as reduced or more frequently reversed in left-handers (Steinmetz et al, 1991;Foundas et al, 1995;Habib et al, 1995;Shapleske et al, 1999;Foundas et al, 2002;Herve et al, 2006). The influences of hand preference on cerebral torque asymmetries are less conclusive.…”

Section: Handedness Effectsmentioning

confidence: 98%

Asymmetries of cortical shape: Effects of handedness, sex and schizophrenia

Narr¹,

Bilder²,

Lüders³

et al. 2007

NeuroImage

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Some evidence suggests that sex, handedness and disease processes associated with schizophrenia affect the magnitude and/or direction of structural brain asymmetries. There are mixed findings, however, on how these factors influence cerebral torque, when torque is assessed with linear or volumetric measurements. We obtained MRI data from 67 healthy (30 males, 10 non-dextrals) and 84 schizophrenia subjects (60 males; 16 non-dextrals) and applied cortical pattern matching to spatially relate and compare differences in the surface morphology of the two cerebral hemispheres at high spatial resolution. Asymmetry indices, computed at thousands of matched hemispheric locations, were used to examine effects of sex, handedness and schizophrenia on hemispheric shape asymmetries while controlling for age and the other factors. Highly significant and discriminative right-frontal and left parietal-occipital surface expansions and protrusions (petalias) were mapped within groups. Although hemispheric shape asymmetries appeared less pronounced within female non-dextrals, asymmetry indices were not shown to differ significantly across sex, hand preference or diagnosis, or to reveal interactions of handedness with sex or diagnosis. Our 3D maps of spatially detailed anterior and posterior hemispheric shape asymmetries reflect subtle geometric distortions in hemispheric surface morphology that cannot be characterized with 2D or volumetric methods. Inter-individual variations in hemispheric torque appear minimally influenced by sex, dextrality or disease status. Biological factors driving language dominance or other lateralized brain functions dissociable from handedness, may more closely relate to hemispheric shape asymmetries, while the lateralization of other discrete brain

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Morphologic Cerebral Asymmetries and Handedness

Cited by 161 publications

References 53 publications

Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia

Altered hemispheric asymmetry of auditory N100m in adults with developmental dyslexia

Pars triangularis asymmetry and language dominance.

Asymmetries of cortical shape: Effects of handedness, sex and schizophrenia

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