Motor sequence complexity and performing hand produce differential patterns of hemispheric lateralization

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• Brain damage studies suggest left hemisphere dominance for complex motor sequence control.
• This lateralization is hypothesized to stem from cognitive planning demands.

Purpose of the Study:

• Investigate hemispheric asymmetries in sensorimotor and association cortex during motor sequencing.
• Determine the neural basis of left hemisphere dominance in complex motor planning.

Main Methods:

• Whole-brain functional magnetic resonance imaging (fMRI) in healthy right-handed subjects.
• Comparison of brain activation volumes during simple and complex finger sequences with right and left hand.
• Analysis of reaction times to assess advanced planning demands.

Main Results:

• Left hemisphere showed greater activation in superior parietal, premotor, and thalamic areas for complex sequences and left-hand movements.
• No significant volumetric asymmetries were found in the primary sensorimotor cortex (SMC).
• Increased signal intensity in left parietal and premotor cortex correlated with sequence complexity.

Conclusions:

• Sensorimotor cortex activity relates to motor execution, independent of sequence complexity.
• Left dorsal premotor and parietal areas are critical for advanced planning in complex motor sequences, irrespective of the hand used.