Internally driven vs. externally cued movement selection: a study on the timing of brain activity

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Medial supplementary motor areas (SMA) and lateral pre-motor areas (PMA) are thought to be functionally dissociated for internally driven versus externally cued movements.
• This dichotomy between SMA and PMA is considered relative, not absolute, prompting further investigation into the underlying neural mechanisms.

Purpose of the Study:

• To investigate the relative functional differences between SMA and PMA in movement selection.
• To determine whether observed differences in brain activity relate to duration, strength, or both.

Main Methods:

• Event-related potentials (ERPs) were recorded from healthy subjects performing right-hand digit movements.
• Movement selection was cued either by internal choice or external stimuli.
• Distributed source localization was used to analyze brain activity patterns.

Main Results:

• Movement selection, regardless of mode (internal vs. external), elicited similar electrical brain activity patterns in terms of configuration, order, and strength.
• Identical electrical brain activity configurations differed in duration between internal and external movement selection.
• Longer-lasting activity was observed in SMA for internal selection and in PMA for external selection.

Conclusions:

• The findings confirm distinct roles for SMA and PMA in internal versus external movement selection, supporting a relative functional dichotomy.
• This functional dissociation between SMA and PMA is primarily attributed to differences in activation duration, rather than differences in activation strength.