Functional demanded excitability changes of human hand motor area

Area of Science:

• Neuroscience
• Human Physiology
• Motor Control

Background:

• The first dorsal interosseous (FDI) and abductor digit minimi (ADM) muscles play crucial roles in hand dexterity.
• Understanding functional differences between these muscles during various contractions is essential for motor control research.

Purpose of the Study:

• To investigate functional differences between FDI and ADM muscles during dynamic and static index and little finger abductions.
• To determine if these functional differences are associated with changes in cortical excitability.

Main Methods:

• Simultaneous recording of motor evoked potentials (MEPs) via transcranial magnetic stimulation (TMS) and force curves during dynamic and static contractions.
• Determination of rest motor thresholds (RMTs) and active motor thresholds (AMTs) for FDI and ADM muscles.
• Recording responses to subcortical stimulation to differentiate cortical and subcortical contributions.

Main Results:

• Target matching errors were significantly smaller for dynamic contractions in the FDI compared to the ADM muscle.
• The FDI muscle exhibited lower active motor thresholds and larger MEPs during dynamic contractions versus static ones, unlike the ADM muscle.
• Responses to subcortical stimulation remained consistent across contraction types for both muscles, suggesting cortical involvement.

Conclusions:

• Task-dependent differences in motor evoked potential facilitation exist between the FDI and ADM muscles.
• These observed functional differences are attributed to task-specific changes in cortical excitability during motor activation.