Cerebral lateralization of praxis in right‐ and left‐handedness: Same pattern, different strength

Abstract

We aimed to investigate the effect of hand effector and handedness on the cerebral lateralization of pantomiming learned movements. Fourteen right-handed and 14 left-handed volunteers performed unimanual and bimanual tool-use pantomimes with their dominant or nondominant hand during fMRI. A left hemispheric lateralization was observed in the right- and left-handed group regardless of which hand(s) performed the task. Asymmetry was most marked in the dorsolateral prefrontal cortex (DLPFC), premotor cortex (PMC), and superior and inferior parietal lobules (SPL and IPL). Unimanual pantomimes did not reveal any significant differences in asymmetric cerebral activation patterns between left- and right-handers. Bimanual pantomimes showed increased left premotor and posterior parietal activation in left- and right-handers. Lateralization indices (LI) of the 10% most active voxels in DLPFC, PMC, SPL, and IPL were calculated for each individual in a contrast that compared all tool versus all control conditions. Left-handers showed a significantly reduced overall LI compared with right-handers. This was mainly due to diminished asymmetry in the IPL and SPL. We conclude that the recollection and pantomiming of learned gestures recruits a similar left lateralized activation pattern in right and left-handed individuals. Handedness only influences the strength (not the side) of the lateralization, with left-handers showing a reduced degree of asymmetry that is most readily observed over the posterior parietal region. Together with similar findings in language and visual processing, these results point to a lesser hemispheric specialization in left-handers that may be considered in the cost/benefit assessment to explain the disproportionate handedness polymorphism in humans.

Hemispheric asymmetries and the control of motor sequences

“…In particular, we noticed a significant involvement of the left relative to the right hemisphere, underlining that its higher-order control processes are required for an efficient motor performance [37,45,46]. This lateralisation profile was independent of hand dominance, which is in agreement with previous observations from tool-use and bimanual actions [23,26,47,56]. It implies that both hemispheres do not contribute equally to cognitive-motor processes, and is in line with work that has shown that patients with left-sided brain damage demonstrate deficits of the planning and execution of heterogeneous sequences, whereas impairment of repetitive sequences is more subtle [18].…”

Handgrip strength in medical students: Correlation with body mass index and hand dimensions

“…18,40 In our study, no significant difference in handgrip strength had been found between the dominant and non-dominant hands in left-handed students. A result, which had been revealed by others 41,42 This can be attributed to that most tools and appliances in daily living are designed for the right hand. Therefore, the left-handed people are compelled to use their non-dominant hands for many daily activities.…”

Attention Allocation and Task Representation during Joint Action Planning

“…We need to point out of course that EEG records electrical activity at the surface of the head and any claims regarding the brain sources of the ERPs should be treated with great caution. Keeping this in mind, it is worth mentioning that the left premotor cortex is considered to be part of a larger network that supports the production of object-directed movements (Vingerhoets et al, 2012) and that it is associated with the prediction and organization of effector-independent complex action sequences (Stadler, Schubotz, von Cramon, Springer,& Prinz, 2011;Haaland, Elsinger,Mayer,Durgerian, & Rao, 2004). Thus, it is conceivable that the enlarged CNV during joint action planning may reflect the implicit representation of the partnerʼs upcoming action and the organization of the two individual actions into a complex joint task.…”