TITLE
Motor Cortical Plasticity in Schizophrenia: A Meta-Analysis of Transcranial Magnetic Stimulation – Electromyography Studies
SOURCE
Schizophrenia Research. 207:37-47, 2019 05.
AUTHORS
Mehta UM; Thanki MV; Padmanabhan J; Pascual-Leone A; Keshavan MS.
BACKGROUND
Several lines of investigations converge upon aberrant synaptic plasticity as a potential pathophysiological characteristic of schizophrenia. In vivo experiments using neuromodulatory perturbation techniques like Transcranial Magnetic and Direct Current Stimulation (TMS & tDCS) have been increasingly used to measure ‘motor cortical plasticity’ in schizophrenia. A systematic quantification of cortical plasticity and its moderators in schizophrenia is however lacking.
METHOD
The PubMed/MEDLINE database was searched for studies up to December 31st, 2017 that examined case-control experiments comparing neuromodulation following single-session of TMS or tDCS. The primary outcome was the standardized mean difference for differential changes in motor evoked potential (MEP) amplitudes measured with single-pulse TMS (MEP DELTA) between patients and healthy subjects following TMS or tDCS. After examining heterogeneity, meta-analyses were performed using fixed effects models.
RESULTS
A total of 16 datasets comparing cortical plasticity (MEP DELTA) between 189 schizophrenia patients and 187 healthy controls were included in the meta-analysis. Patients demonstrated diminished MEP DELTA with effect sizes (Cohen’s d) ranging from 0.66 (LTP-like plasticity) to 0.68 (LTD-like plasticity). Heterosynaptic plasticity studies demonstrated a greater effect size (0.79) compared to homosynaptic plasticity studies (0.62), though not significant (P=0.43). Clinical, perturbation protocol- and measurement-related factors, and study quality did not significantly moderate the aberrant plasticity demonstrated in schizophrenia.
CONCLUSIONS
Schizophrenia patients demonstrate diminished LTP- and LTD-like motor cortical plasticity, which is not influenced by the various clinical and experimental protocol related confounders. These consistent findings should encourage the use of perturbation-based biomarkers to characterize illness trajectories and treatment response
