Targeting Personalized Brain States Reflecting Strong and Weak Corticospinal Tract Output in Real-time

Transcranial magnetic stimulation (TMS) interventions could feasibly strengthen residual corticospinal tract (CST) connections and enhance recovery of paretic hand function after stroke. To maximize the therapeutic effects of such interventions, they must be delivered during poststroke brain activity patterns during which TMS best activates the residual corticospinal tract and enhances neural transmission within it (i.e., brain state-dependent TMS). In this study, the investigators will test the feasibility of real-time, personalized brain state-dependent TMS in neurotypical adults. Participants will visit the laboratory for one day of testing. Upon arrival, participants will provide their informed consent; afterwards, they will complete eligibility screening. The investigators will then place recording electrodes on the scalp using a swim-type cap and on the left first dorsal interosseous, abductor pollicis brevis, and extensor digitorum communis muscles. After determining the location at which TMS best elicits muscle twitches in the left first dorsal interosseous, the investigators will determine the lowest possible intensity at which TMS elicits muscle twitches at least half of the time in this muscle. Then, the investigators will deliver 6 blocks of 100 single TMS pulses while the participant rests quietly with their eyes open; stimulation will be delivered at an intensity that is 20% greater than the lowest possible intensity at which TMS elicits muscle twitches at least half of the time. Afterwards, the investigators will use the muscle and brain activity recordings acquired during these 6 blocks to build a personalized mathematical model that identifies which patterns of brain activity correspond to the largest TMS-evoked muscle twitches. The investigators will then use this model to detect the occurrence of these brain activity patterns in real-time; when these patterns are detected, single TMS pulses will be delivered. Afterwards, all recording electrodes