Cognitive Dysfunction In Parkinson's

TMS: Repetitive TMS will be administered using a 70-mm diameter air-cooled figure-of-8 coil and SuperRapid2 Stimulator (Magstim, Jali Medical US distributors, Woburn, MA). Repetitive pulses will be delivered to the right and left pre-frontal cortex (Brodman area 46) using a frameless stereotactic navigation system and the subject's MRI in Brainsight software. Stimuli will be delivered at 20 Hz at 90% of the subjects resting motor threshold (rMT) for 25 trains of 30 pulses per train, inter-train interval of 30 seconds for a total of 750 pulses per hemisphere. The same TMS parameters as active stimulation but with the coil held at 90° to the scalp to induce similar somatic sensations and noise as in the active group with minimal direct brain effects.

Sham TMS will be administered with a Magstim sham coil with electrodes attached to mimic the sounds and sensation of real TMS. The site and frequency of stimulation will be identical to the real TMS described above.