Cortical Asymmetries during Hand Laterality Task Vary with Hand Laterality: A fMRI Study in 295 Participants

Abstract

The aim of this study was to characterize, using fMRI, the functional asymmetries of hand laterality task (HLT) in a sample of 295 participants balanced for handedness. During HLT, participants have to decide whether the displayed picture of a hand represent a right or a left hand. Pictures of hands’ back view were presented for 150 ms in the right or left hemifield. At the whole hemisphere level, we evidenced that the laterality of the hand and of the hemifield in which the picture was displayed combined their effects on the hemispheric asymmetry in an additive way. We then identified a set of 17 functional homotopic regions of interest (hROIs) including premotor, motor, somatosensory and parietal regions, whose activity and asymmetry varied with the laterality of the presented hands. When the laterality of a right hand had to be evaluated, these areas showed stronger leftward asymmetry, the hROI located in the primary motor area showing a significant larger effect than all other hROIs. In addition a subset of six parietal regions involved in visuo-motor integration together with two postcentral areas showed a variation in asymmetry with hemifield of presentation. Finally, while handedness had no effect at the hemispheric level, two regions located in the parietal operculum and intraparietal sulcus exhibited larger leftward asymmetry with right handedness independently of the hand of presentation. The present results extend those of previous works in showing a shift of asymmetries during HLT according to the hand presented in sensorimotor areas including primary motor cortex. This shift was not affected by manual preference. They also demonstrate that the coordination of visual information and handedness identification of hands relied on the coexistence of contralateral motor and visual representations in the superior parietal lobe and the postcentral gyrus.

The Impact of Handedness, Sex, and Cognitive Abilities on Left–Right Discrimination: A Behavioral Study

“…Studies have also often investigated the effect of handedness, with the same hypothesis that left-handers would have reduced brain lateralization and would be more prone to Left–Right Confusion ( Brandt and Mackavey, 1981 ). However, several studies that included a large sample of left-handers did not show any difference in hemispheric lateralization related to handedness ( Mazoyer et al, 2014 ; Tzourio-Mazoyer et al, 2015 ; Mellet et al, 2016 ; Biduła et al, 2017 ). In the same way, recent neuroimaging studies ( Hirnstein et al, 2011 ; Hjelmervik et al, 2015 ) found no reason to believe that sex differences in LRD were related to a more bilateral brain in women.…”

Bilateral carpal tunnel syndrome – A review

“…There were no differences in the extent of these distortions with respect to the dominant hand [20]. Fornander et al analyzed the effect of traumatic median nerve damage at carpal level on spatial activation of the primary cortical centres in functional MRI.…”

Understanding the Left Right Judgement Test: A Literature Review

“…Similar response times may also be explained using the results of the fMRI study. Mellet et al [24] confirmed that a shift away was exhibited during the LRJT in the sensorimotor cortex, including the motor cortex. This shift was affected by the presented hand images, but not by handedness.…”