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Cerebral asymmetries: complementary and independent processes.

Badzakova-Trajkov G, Häberling IS, Roberts RP, Corballis MC - PLoS ONE (2010)

Bottom Line: Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene.This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech.It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Auckland, Auckland, New Zealand. g.badzakova@auckland.ac.nz

ABSTRACT
Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene. This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech. It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing. Here we use functional magnetic resonance imaging with a sample of 155 subjects to measure asymmetrical activation induced by speech production in the frontal lobes, by face processing in the temporal lobes, and by spatial processing in the parietal lobes. Left-frontal, right-temporal, and right-parietal dominance were all intercorrelated, suggesting that right-cerebral biases may be at least in part complementary to the left-hemispheric dominance for language. However, handedness and parietal asymmetry for spatial processing were uncorrelated, implying independent lateralizing processes, one producing a leftward bias most closely associated with handedness, and the other a rightward bias most closely associated with spatial attention.

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Related in: MedlinePlus

Asymmetrical activation elicited for speech production, spatial processing, and face processing.(A) Group activations from the random effects analysis for the Word Generation Task–WGT. Activations are displayed laterally on a cortical surface rendered brains and through axial slices; (B) Group activations from the random effects analysis for the Landmark Task–LT; (C) Group activations from the random effects analysis for the Faces Task–FT; (D) Activations for the three tasks are shown together on a rendered brain (lateral view) (red = WGT; green = LT; blue = FT); (E) Regions of interest (ROIs) used for calculating the laterality indices for each of the tasks are also shown (top = coronal view; bottom = axial view). Displayed results are significant at p<.05 with family-wise error (FWE) rate correction for multiple comparisons.
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pone-0009682-g001: Asymmetrical activation elicited for speech production, spatial processing, and face processing.(A) Group activations from the random effects analysis for the Word Generation Task–WGT. Activations are displayed laterally on a cortical surface rendered brains and through axial slices; (B) Group activations from the random effects analysis for the Landmark Task–LT; (C) Group activations from the random effects analysis for the Faces Task–FT; (D) Activations for the three tasks are shown together on a rendered brain (lateral view) (red = WGT; green = LT; blue = FT); (E) Regions of interest (ROIs) used for calculating the laterality indices for each of the tasks are also shown (top = coronal view; bottom = axial view). Displayed results are significant at p<.05 with family-wise error (FWE) rate correction for multiple comparisons.

Mentions: Laterality indices were calculated for each subject using the LI toolbox available from the SPM website [21]. This applies a bootstrapping technique allowing about 10 000 indices to be calculated at different thresholds yielding a robust mean, maximum, and minimum index. Taking thresholds into account, an overall weighted bootstrapped laterality index is calculated. Indices range from −1 to +1, with extremes representing complete lateralization to the right and left, respectively. This weighted mean index was calculated for three regions of interest (ROIs) (see Figure 1) that were pre-defined in the LI toolbox [21]; the ROIs were the frontal lobes for word generation, the temporal lobe for the faces task, and the parietal lobes for the landmark task.


Cerebral asymmetries: complementary and independent processes.

Badzakova-Trajkov G, Häberling IS, Roberts RP, Corballis MC - PLoS ONE (2010)

Asymmetrical activation elicited for speech production, spatial processing, and face processing.(A) Group activations from the random effects analysis for the Word Generation Task–WGT. Activations are displayed laterally on a cortical surface rendered brains and through axial slices; (B) Group activations from the random effects analysis for the Landmark Task–LT; (C) Group activations from the random effects analysis for the Faces Task–FT; (D) Activations for the three tasks are shown together on a rendered brain (lateral view) (red = WGT; green = LT; blue = FT); (E) Regions of interest (ROIs) used for calculating the laterality indices for each of the tasks are also shown (top = coronal view; bottom = axial view). Displayed results are significant at p<.05 with family-wise error (FWE) rate correction for multiple comparisons.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2837380&req=5

pone-0009682-g001: Asymmetrical activation elicited for speech production, spatial processing, and face processing.(A) Group activations from the random effects analysis for the Word Generation Task–WGT. Activations are displayed laterally on a cortical surface rendered brains and through axial slices; (B) Group activations from the random effects analysis for the Landmark Task–LT; (C) Group activations from the random effects analysis for the Faces Task–FT; (D) Activations for the three tasks are shown together on a rendered brain (lateral view) (red = WGT; green = LT; blue = FT); (E) Regions of interest (ROIs) used for calculating the laterality indices for each of the tasks are also shown (top = coronal view; bottom = axial view). Displayed results are significant at p<.05 with family-wise error (FWE) rate correction for multiple comparisons.
Mentions: Laterality indices were calculated for each subject using the LI toolbox available from the SPM website [21]. This applies a bootstrapping technique allowing about 10 000 indices to be calculated at different thresholds yielding a robust mean, maximum, and minimum index. Taking thresholds into account, an overall weighted bootstrapped laterality index is calculated. Indices range from −1 to +1, with extremes representing complete lateralization to the right and left, respectively. This weighted mean index was calculated for three regions of interest (ROIs) (see Figure 1) that were pre-defined in the LI toolbox [21]; the ROIs were the frontal lobes for word generation, the temporal lobe for the faces task, and the parietal lobes for the landmark task.

Bottom Line: Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene.This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech.It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Auckland, Auckland, New Zealand. g.badzakova@auckland.ac.nz

ABSTRACT
Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene. This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech. It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing. Here we use functional magnetic resonance imaging with a sample of 155 subjects to measure asymmetrical activation induced by speech production in the frontal lobes, by face processing in the temporal lobes, and by spatial processing in the parietal lobes. Left-frontal, right-temporal, and right-parietal dominance were all intercorrelated, suggesting that right-cerebral biases may be at least in part complementary to the left-hemispheric dominance for language. However, handedness and parietal asymmetry for spatial processing were uncorrelated, implying independent lateralizing processes, one producing a leftward bias most closely associated with handedness, and the other a rightward bias most closely associated with spatial attention.

Show MeSH
Related in: MedlinePlus