Transcranial Magnetic Stimulation to Improve Gesture Control

Schizophrenia is associated with poor social functioning, which is perturbed by deficits in social interaction including nonverbal communication. The use of hand gestures is critical for nonverbal communication, but the majority of schizophrenia patients has severe gesture impairments. Today no intervention may ameliorate gesture impairments. Patients with gesture impairments have altered structure and function of the gesture network, particularly the left inferior frontal gyrus (IFG) and also the left inferior parietal lobe (IPL). Noninvasive brain stimulation techniques may alter local brain function. Repetitive transcranial magnetic stimulation (rTMS) and particularly theta burst stimulation (TBS) for a few mins is a very safe method to alter brain states locally for approximately 1 hour. Indeed, facilitatory stimulation of the left frontal cortex by transcranial direct current stimulation (tDCS) demonstrated improved gesture perception and interpretation in healthy subjects. In addition, inhibitory stimulation with continuous theta burst stimulation (cTBS) over left IFG may perturb gesture performance in healthy subjects. Thus, the investigators hypothesize that local changes of brain activity within the gesture network would change gesture performance. Particularly, facilitatory intermittent theta burst stimulation (iTBS) of the left IFG would improve gesture performance. The investigators will test single sessions of rTMS in healthy subjects and schizophrenia patients. If one of the protocols proves to have superior effects, this result will help to plan interventional trials targeting social interaction deficits in schizophrenia. The aim of the study is to determine the effect of one session of iTBS over the left IFG on gesture performance compared to cTBS over the right IPL (active comparator) and one placebo rTMS sessions. This is a randomized, double-blind, cross-over, placebo-controlled single-center trial in 20 patients with schizophrenia spectrum disorders and 20 healthy controls. After baseline assessment of gesture performance, participants will receive one rTMS protocol at each time point, immediately followed by assessments of gesture performance and dexterity. rTMS sessions will be separated by 48 hours. Gesture performance will be measured with video recorded Test of Upper Limb Apraxia, which is rated blindly according to a manual.

Inclusion criteria

• Right handed according to the Edinburgh Handedness Inventory
• Ability and willingness to participate in the study
• Ability to provide written informed consent
• Informed Consent as documented by signature (Appendix Informed Consent Form)
• Spent majority of childhood/adolescence in Switzerland
• Patients: schizophrenia spectrum disorder according to Diagnostic and Statistical Manual version 5 (DSM-5)

Exclusion criteria

• Women who are pregnant or breast feeding
• Metal objects on or in the body (e.g. grenade splinter, cardiac pacemaker, vessel clips, metal prostheses, contraceptive coil, cochlear implants, hearing aid, tooth implant)
• History of neurosurgery, any severe head wounds, history of neurologic disorders impacting gesture, e.g. Parkinson's disease, stroke, multiple sclerosis sclerosis and epilepsy, convulsion or seizure
• History of any hearing problems or ringing in the ears.
• Active drug addiction except nicotine
• Controls: first-degree relatives with schizophrenia spectrum disorders