Reduced finger tapping speed in patients with schizophrenia and psychomotor slowing: an exploratory fMRI study

Abstract

Introduction: Motor symptoms are frequent in patients with schizophrenia and have multiple presentations, one of which is psychomotor slowing. Understanding the neural basis of psychomotor slowing may help improve future therapies in schizophrenia. Here, we performed task-fMRI using a finger-tapping task in slowed patients.

Methods: The study included 36 patients with schizophrenia and psychomotor slowing (Salpêtrière-Retardation-Rating-Scale-Score (SRRS) >15), 11 non-slowed patients with schizophrenia, and 33 healthy controls who successfully performed a motor task during fMRI, with four conditions: paced and fast thumb-index finger tapping and thumb alternating finger opposition. The performance was videotaped and taps were counted. We compared task-related neural substrates between groups, task complexity and movement onset.

Results: Slowed patients with schizophrenia showed significantly lower tapping speed than controls in both unpaced conditions (Δ=-.80 (CI=-1.46; -.14)taps/s, p=.019; Δ=-.80 (CI=-1.32; -.28)taps/s, p=.003) while non-slowed patients had a tapping speed between the other two groups.

Discussion: In both task complexity and movement onset factor levels, all the groups activated sensorimotor areas. Slowed patients had no regulation of the task-dependent cerebellar involvement while showing insufficient deactivation of the SPL, pointing to altered recruitment of neural resources in response to motor demands in schizophrenia especially when associated with psychomotor slowing.

Keywords: fMRI; finger-tapping; psychomotor slowing; psychosis; schizophrenia; task-fMRI.

Figure 1

Schematic depiction of the task conditions. TIF _paced: Sound-paced thumb-index finger tapping; TIF _unpaced : unpaced thumb-index finger tapping; TAF _paced : Sound-paced thumb-alternating finger opposition; TAF _unpaced : unpaced thumb-alternating finger opposition; Rx: run number x. Adapted Figure from Wüthrich et al. (49) under CC license.

Figure 2

Scatter plot of the correlation between motor-related clinical scales and performance during TAF _unpaced . The solid line is the “line of best fit”, a line that minimizes the vertical distances between the data points and the line itself. The “line of best fit” is a useful way of representing the linear trend. The gray shading around the line represents the 95% confidence interval around the line of best fit. TAF _unpaced , unpaced thumb alternating finger opposition; SRRS, Salpêtrière retardation rating scale; BFCRS, Bush-Francis catatonia rating scale; UPDRS, unified Parkinson’s disease rating scale.

Figure 3

Main group and interaction effects from the 3x2x2 model. Red scale represents the significance of the F-tests. (A) Main effect of group, (B) Main effect of movement onset, (C) Main effect of complexity, (D) interaction group by complexity, (E) group by onset, (F) interaction complexity by movement onset.

Figure 4

Main group and interaction effect from the 2x2x2 model. Red scale represents the significance of the F-tests. (A) Main effect of movement onset, (B) Main effect of complexity, (C) interaction group by complexity, (D) interaction complexity by movement onset.

Figure 5

Activations (red) and deactivations (blue) per groups for both complexity and movement onset factor levels. HC, healthy controls; non-PS, non-slowed patients; PS, slowed patients; complexity TIFs: combined TIF _paced and TIF _unpaced ; complexity TAFs combined TAF _paced and TAF _unpaced , movement onset paced combined TIF _paced and TAF _paced ; movement onset unpaced combined TIF _unpaced and TAF _unpaced. . TIF, thumb-index finger tapping; TAF, thumb-alternating finger opposition; eq, equivalent; PANSS, positive and negative syndrome scale; OLZ, olanzapin.

Figure 6

Between groups comparison in whole-brain BOLD response regarding both complexity and movement onset factor levels. Red refers to HC > non-PS, HC> PS, and HC-SCZ. Blue refers to non-PS >HC, PS >HC, and SCZ>HC. HC, healthy controls; non-PS, non-slowed patients; PS, slowed patients; complexity TIFs: combined TIF _paced and TIF _unpaced ; complexity TAFs combined TAF _paced and TAF _unpaced , movement onset paced combined TIF _paced and TAF _paced ; movement onset unpaced combined TIF _unpaced and TAF _unpaced. . TIF, thumb-index finger tapping; TAF, thumb-alternating finger opposition; eq, equivalent; PANSS, positive and negative syndrome scale; OLZ, olanzapin; PS, patients with slowing; non-PS, patients without slowing; HC, healthy controls.

Figure 7

Group by conditions comparison in ROI extracted beta values from significant clusters of HC vs schizophrenia contrasts. The figure displays trimmed violin plots including box-and-whisker plots. The center line represents the median value, the lower bound of the box represents the 25th percentile, the upper bound of the box the 75th percentile, and the whiskers represent 3 times the interquartile range. *p < 0.05, **p < 0.01, ***p < 0.001, ****p< 0.0001. Red is for PS, yellow for non-PS, and blue for HC. R, right; L, left; M1, primary motor cortex; Cerebellum, cluster covering lobules; IV-V-VI HC, healthy controls; non-PS, non-slowed patients; PS, slowed patients; TIF, thumb-index finger tapping; TAF, thumb-alternating finger opposition.

Figure 8

Scatter plots of the correlation between brain activation and performance during TIF and TAF _unpaced conditions in HC. The solid line is the “line of best fit”, a line that minimizes the vertical distances between the data points and the line itself. The “line of best fit” is a useful way of representing the linear trend. The gray shading around the line represents the 95% confidence interval around the line of best fit. L M1, left primary motor cortex; L S1, left primary sensory motor cortex; HC, healthy controls.