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. 2019 May 17;142(7):2149–2164. doi: 10.1093/brain/awz127

Figure 2.

Figure 2

Force control accuracy. (A) Raw data of single trials of grip force-tracking for a patient with schizophrenia (PSZ) and a healthy control subject (HC) for (i) the single-task force-tracking condition (Single) and the dual-task condition with (ii) dual-task distraction trial (Dual-DIST) and (iii) dual-task addition trial (Dual-ADD). Exerted force = solid line; target force (ramp-hold-and-release profile) = dotted grey line. Although the patient with schizophrenia seemed to perform the force matching task with less accuracy, the task was achieved; the overall modulation of force follows the target force throughout the trial, the force modulation is neither flat nor random, and the target hold-force level was reached (see Supplementary material for detailed analysis). (B) Mean RMS tracking-error (estimated marginal mean ± vertical bars: 95% confidence interval, CI) during Single (grey), Dual-DIST (pink) and Dual-ADD trials (cyan) for the three groups: patients with schizophrenia, healthy controls and siblings (SIB). Triangles represent data points of the individual subjects in each group and condition. Significant differences (LSD fisher post hoc tests for between group comparisons are shown as horizontal black brackets and within group comparisons as horizontal grey dashed brackets with: *P < 0.05; **P < 0.01, ***P < 0.001. For clarity, significant differences for between-group comparisons are only indicated between patients and healthy controls. Post hoc tests for between-group comparisons revealed that patients had increased error in the three conditions compared to controls (patients with schizophrenia versus healthy controls, Single: P = 0.03; Dual-DIST: P = 0.001; Dual-ADD: P < 0.001), but also to siblings (patients with schizophrenia versus siblings, Single: P = 0.04; DIST: P = 0.002; Dual-ADD: P < 0.001). Post hoc tests for within group comparisons revealed that DIST condition led to increased error compared to Single-task condition only in the patients with schizophrenia group (patient with schizophrenia: P = 0.003; healthy controls: P = 0.24; siblings: P = 0.88). However, Dual-ADD trials led to increased error compared to Single-task trials in all groups (patient with schizophrenia: P < 0.001; healthy controls: P < 0.001; siblings: P < 0.001).