Repeated tDCS at Clinically Relevant Field Intensity Can Boost Concurrent Motor Learning in Rats

Area of Science:

• Neuroscience
• Motor Learning
• Brain Stimulation

Background:

• Transcranial direct current stimulation (tDCS) uses weak electric fields, with limited demonstrated behavioral effects in animal models.
• Previous research has not established whether concurrent behavioral training and repeated tDCS sessions can yield significant outcomes.
• Investigating tDCS efficacy in animal models is crucial for understanding its therapeutic potential in humans.

Purpose of the Study:

• To test the hypothesis that weak tDCS, when combined with behavioral training and repeated sessions, produces sizable behavioral effects in a rodent model.
• To evaluate the impact of concurrent anodal tDCS and motor skill training on learning dynamics and corticospinal excitability.
• To explore potential interactions between tDCS effects, paw preference, and motor performance.

Main Methods:

• A rodent model of dexterous motor skill learning using an automated pellet-reaching task was employed.
• Male rats underwent 10 daily sessions of concurrent epicranial tDCS (2 V/m at the motor cortex) with behavioral training.
• Behavior was recorded using high-speed video, and motor-evoked potentials (MEPs) were measured via epidural microstimulation.

Main Results:

• The anodal tDCS group showed a significantly higher rate of motor skill learning compared to the sham-control group (p=0.008).
• tDCS did not systematically affect motor-evoked potentials, indicating no significant change in corticospinal excitability.
• Post hoc analysis revealed that tDCS modulated motor learning specifically in right-pawed animals, improving reaching success and reducing stereotypy.

Conclusions:

• Repeated and concurrent anodal tDCS can enhance motor skill learning at clinically relevant field intensities in a rodent model.
• The observed motor learning enhancement by tDCS interacted with paw preference and was independent of changes in corticospinal excitability.
• These findings support the potential of targeted tDCS protocols for improving motor rehabilitation strategies.