Overview of results from TMS-EMG studies*
| Measure | Main findings | Hypothesis |
|---|---|---|
| Resting motor threshold | Fifteen studies reported no significant differences between medicated patients with chronic schizophrenia and healthy controls;54,60,78–90 1 study91 reported no significant difference between medication-naive or minimally treated (< 1 month) patients with first-episode psychosis and healthy controls; 1 study reported lower RMT in medicated patients;92 2 studies reported higher RMT in medicated patients with chronic schizophrenia;93,94 1 study showed higher RMT in medicated patients45 | Patients would show deficits in GABA-mediated cortical inhibition as measured by CSP and paired-pulse inhibition paradigms (e.g., SICI and LICI). Intracortical facilitation may not be significantly different between patients and healthy controls |
| Active motor threshold | Two studies reported no significant differences between patients with chronic schizophrenia (mostly medicated) and healthy controls84,86 or healthy siblings86 | |
| Amplitude of motor evoked potentials | Four studies found no significant differences between medicated and unmedicated patients with chronic schizophrenia and healthy controls;81,82,87,94 2 studies reported unaltered MEP sizes in medicated patients with first-episode schizophrenia58 and medicated patients;89 1 study found smaller MEP sizes in medicated chronic patients;54 1 study found increased MEP sizes in medicated patients with chronic schizophrenia;88 1 study found no significant differences between patients with recent-onset and multi-episode schizophrenia, people at risk and healthy controls; 1 study found smaller MEP sizes in people at risk compared to patients with first-episode schizophrenia and healthy controls45 | |
| Duration of cortical silent period | Four studies found no significant differences between medicated patients with chronic schizophrenia and healthy controls;45,86,93,95 2 studies reported significantly shorter CSP duration in medicated and unmedicated patients with chronic schizophrenia;84,96 1 study found longer CSP duration in medicated patients with chronic schizophrenia and people at risk, and no significant difference between the 2 groups;54 1 study reported longer CSP duration in patients with first-episode schizophrenia compared to people at risk and healthy controls, and no difference between the latter 2 groups;58 1 study reported longer CSP duration in patients for the 130% of the RMT but not for 90% maximum stimulator output94 | |
| Short-latency afferent inhibition | One study reported normal short-latency afferent inhibition in patients compared to healthy controls97 | |
| Transcallosal inhibition | Two studies reported increased duration of transcallosal inhibition in patients who used the single-pulse paradigm.79,80 | |
| Short-interval intracortical inhibition | Eight studies reported reduced SICI in medicated patients with chronic schizophrenia,45,54,60,81,82,89,93 patients with recent-onset schizophrenia60 and medicated patients with first-episode schizophrenia;58 1 study reported unchanged SICI in patients with chronic schizophrenia and medication resistance;95 1 study reported unchanged SICI in medicated patients with chronic schizophrenia at interstimulus intervals of 1, 2, 3 and 4 ms but when data for the 4 interstimulus intervals were pooled, patients showed reduced SICI;84 1 study reported reduced SICI in people at risk;56 1 study found unchanged SICI in people at risk.54 | |
| Intracortical facilitation | Seven studies reported no significant differences between medicated patients with chronic schizophrenia and healthy controls;45,54,60,82,84,93,95 1 study found no significant difference between people at risk, medicated patients with chronic schizophrenia and healthy controls;54 1 study reported mixed results: reduced intracortical facilitation in medicated patients with chronic schizophrenia compared to healthy controls in 1 experimental session, but no difference between the groups in another session that was 4~8 days apart89 | |
| Long-interval intracortical inhibition | One study found no differences between medicated patients and healthy controls93 |
CSP = cortical silent period; EMG = electromyography; GABA = γ-aminobutyric acid; LICI = long-interval intracortical inhibition; MEP = motor evoked potential; RMT = resting motor threshold; SICI = short=interval intracortical inhibition; TMS = transcranial magnetic stimulation.
↵* Unless otherwise specified, comparisons were made between patient groups or people at risk of psychosis and healthy controls.