Neurophysiological aftereffects of 10 Hz and 20 Hz transcranial alternating current stimulation over bilateral sensorimotor cortex

Lafleur, Louis-Philippe, Gabrielle Klees-Themens, Christine Chouinard-Leclaire, Félix Larochelle-Brunet, Sara Tremblay, Jean-Francois Lepage, & Hugo Théoret. 2020. Neurophysiological aftereffects of 10 Hz and 20 Hz transcranial alternating current stimulation over bilateral sensorimotor cortex. Brain Research. 1727: 146542.
 
Summary: Lafleur and colleagues (2020) applied 10 and 20 Hz tACS (1 mA) bilaterally to the motor cortex to determine how interhemispheric interactions were influenced by stimulation. By using a bilateral montage (C3-C4), the fields generated at either site were equal in magnitude but antiphase to each other. Using TMS over the left motor cortex, TACS at 10 Hz reduced the amplitude of single pulse MEPs when compared to sham and 20 Hz stimulation. Interhemispheric inhibition (IHI) of the left to right motor cortices was unchanged as were MEP amplitudes during physiological mirror movements (I.e., pinching in the contralateral hand) measured from the right hemisphere. 
 
Pro:  

• Novel use of bilateral stimulation with interhemispheric TMS protocols.
• Within-subject, double-blinded, sham-controlled design

 
Open Questions:  

• Does the online effect of antiphase stimulation differ from the immediate aftereffects of stimulation? What about at longer timescales post-tACS?

 
Contributed by: Christopher Walker, PhD