Abnormal visuomotor processing in schizophrenia

Abstract

Subtle disturbances of visual and motor function are known features of schizophrenia and can greatly impact quality of life; however, few studies investigate these abnormalities using simple visuomotor stimuli. In healthy people, electrophysiological data show that beta band oscillations in sensorimotor cortex decrease during movement execution (event-related beta desynchronisation (ERBD)), then increase above baseline for a short time after the movement (post-movement beta rebound (PMBR)); whilst in visual cortex, gamma oscillations are increased throughout stimulus presentation. In this study, we used a self-paced visuomotor paradigm and magnetoencephalography (MEG) to contrast these responses in patients with schizophrenia and control volunteers. We found significant reductions in the peak-to-peak change in amplitude from ERBD to PMBR in schizophrenia compared with controls. This effect was strongest in patients who made fewer movements, whereas beta was not modulated by movement in controls. There was no significant difference in the amplitude of visual gamma between patients and controls. These data demonstrate that clear abnormalities in basic sensorimotor processing in schizophrenia can be observed using a very simple MEG paradigm.

Keywords: Electrophysiological processes; Magnetoencephalography; Motor cortex; Schizophrenia; Visual cortex.

Fig. 1

Time frequency spectrograms. Percentage change from baseline in the trial-averaged signal at the locations of individuals’ peak decrease in motor beta (a&b) and increase in visual gamma (c & d) during stimulation. Data are averaged across controls (a & c) and patients (b & d). Visual stimulation and motor responses were from 0–2 s. On the right are example pseudo t-statistical images from a single representative subject showing the spatial signature of the beam-formed signal in the stimulus window (0.5–1.8 s) contrasted with a baseline window (7–8.3 s) in the beta (13–30 Hz) band (e) and gamma (30–70 Hz) band (f).

Fig. 2

Beta and gamma band responses. Mean timecourse of beta band amplitude in motor cortex (a) and gamma band amplitude in visual cortex (b), measured as a percentage difference from baseline (7–8.3 s); shaded areas show standard error of the mean (SEM) across participants. c) Mean percentage signal change from baseline in motor cortex during event-related beta desynchronisation (ERBD; 0.5–1.8 s) and post-movement beta rebound (PMBR; 2.3–4.3 s); and in visual gamma oscillations during stimulation (0.5–1.8 s). Error bars represent SEM.

Fig. 3

Timecourses for groups with equivalent numbers of button presses. Mean motor beta (a) and visual gamma (b) timecourses in groups of patients (red, N = 12) and controls (blue, N = 13) who made similar numbers of button presses (mean of 4–8 presses per trial). Shaded areas are SEM across participants.

Fig. 4

Effect of number of button presses. Mean beta timecourses for groups of patients (red) and controls (blue), defined by the quartiles of mean button press count across all volunteers, from lowest (a) to highest (d). Shaded areas represent SEM across all trials.

Fig. 5

Correlation between PMBR and severity of persisting psychotic illness. The amplitude of the post-movement beta rebound showed a significant negative correlation with a measure of overall psychotic illness severity persisting during a stable phase of illness in the patient group.