Multi-session Transcranial Direct Current Stimulation Over Primary Motor Cortex Facilitates Sequence Learning,...

Area of Science:

• Neuroscience
• Cognitive Science
• Motor Control

Background:

• Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) is known to enhance motor learning.
• The impact of tDCS on other brain regions, such as the prefrontal cortex (PFC), on motor sequence learning, including online and offline phases and long-term retention, remains less understood.

Purpose of the Study:

• To investigate the differential effects of tDCS applied to the prefrontal cortex (PFC), primary motor cortex (M1), and supplementary motor area complex on motor sequence learning.
• To determine the role of these brain regions in online learning, offline learning, and long-term retention of motor sequences.

Main Methods:

• Three experiments involving tDCS (anodal and cathodal) or sham stimulation applied to the PFC and M1 during motor sequence learning tasks.
• Assessment of learning metrics including reaction time and the number of chunks formed.
• A one-year delayed relearning test was conducted to evaluate long-term retention.

Main Results:

• tDCS applied to the PFC (both anodal and cathodal) resulted in impaired motor sequence learning, evidenced by slower reaction times and fewer chunks formed.
• Stimulation over M1 significantly improved both reaction time and chunk formation during learning.
• Participants who received M1 tDCS in the initial learning phase demonstrated faster relearning of motor sequences after a one-year interval compared to sham and PFC groups.

Conclusions:

• tDCS applied to the PFC negatively impacts motor sequence learning, irrespective of stimulation polarity.
• Stimulation of M1 using tDCS facilitates motor sequence learning and enhances long-term retention and relearning.
• These findings highlight the distinct roles of PFC and M1 in motor sequence learning and memory consolidation.