Handedness and task demands modulate motor cortex lateralization: A cross-sectional fNIRS study

Area of Science:

• Neuroscience
• Motor Control
• Cerebral Hemispheric Lateralization

Background:

• Motor control studies typically focus on right-handed individuals, overlooking factors influencing cortical activation asymmetry.
• Manual preference, hand dominance, and task type significantly impact brain lateralization during motor tasks.

Purpose of the Study:

• To compare cortical activation asymmetry in right-handed and left-handed individuals during distinct motor tasks.
• To investigate the influence of manual laterality on brain organization during upper limb movement.

Main Methods:

• Functional near-infrared spectroscopy (fNIRS) measured cortical activity in premotor cortex (PMC) and sensorimotor cortex (SMC).
• 25 right-handed and 25 left-handed participants performed distal and manipulation tasks with each hand.
• A Laterality Index assessed left-right hemisphere activation asymmetry.

Main Results:

• Right-handers exhibited predominantly contralateral cortical activation, while left-handers showed more bilateral activation.
• Activation asymmetry was more pronounced when using the right hand (non-dominant for left-handers).
• Task-specific motor demands modulated the degree of brain asymmetry.

Conclusions:

• Left-handers display less asymmetrical brain organization than right-handers, possibly due to enhanced interhemispheric connectivity.
• This bilateral organization in left-handers may facilitate neural recovery after conditions like stroke.
• Manual laterality is a critical factor to consider in neurophysiological and clinical studies of central nervous system disorders.