Early motor resonance differentiates schizophrenia patients from healthy subjects and predicts social cognition performance

Background: Diminished motor resonance (facilitation of motor potentials during action observation) is possibly related to social cognition deficits in schizophrenia. Adequate social cognition requires the successful moment-to-moment appraisal of social stimuli over a temporal window. However, similar changes in motor resonance with successive action observation stimuli are unknown. We compared the time-course of motor resonance evoked during successive action observation stimuli between schizophrenia patients (antipsychotic-naive and medicated) and healthy subjects and examined its association with social cognition performance. Method: Fifty-four schizophrenia patients (33 antipsychotic-naive) and 45 healthy subjects underwent 10-recordings (T1 to T10) of cortical reactivity, using two single (sp)- and two paired-pulse (pp) transcranial magnetic stimulation (TMS) paradigms, while they observed goal-directed actions and a static image. They also underwent comprehensive social cognition assessments. Results: Sp-motor resonance revealed a significant quadratic time effect (initial fall and then rise) in patients and healthy subjects [F=12.21, P =0.001]. Such a pattern was not observed for pp-motor resonance. We categorized motor resonance as early (T1-T3), middle (T4-T7) and late (T8-T10) based on pair-wise comparisons. Early, but not middle or late sp-motor resonance was reduced in antipsychotic naive patients compared to the medicated patients and healthy subjects (F = 3.41, P =0.037). Social cognition composite score had significant correlations with both early sp-motor resonance (r = 0.34, P = 0.01) and early pp-motor resonance (r = 0.314, P = 0.02) in the combined patient group. Conclusions: Motor resonance time-courses did not vary across groups. The magnitude of early motor resonance was reduced in the antipsychotic-naIve schizophrenia group, compared to healthy subjects. Early phase motor resonance was associated with social cognition deficits in patients.