The Behavioral Mapping of Psychomotor Slowing in Psychosis Demonstrates Heterogeneity Among Patients Suggesting Distinct Pathobiology

Abstract

Objectives Psychomotor slowing (PS) occurs in up to half of schizophrenia patients and is linked to poorer outcomes. As standard treatment fails to improve PS, novel approaches are needed. Here, we applied the RDoC framework using 3 units of analysis, ie, behavior, self-report, and physiology to test, whether patients with PS are different from patients without PS and controls. Methods Motor behavior was compared between 71 schizophrenia patients with PS, 25 without PS, and 42 healthy controls (HC) using 5 different measures: (1) for behavior, an expert rating scale: Motor score of the Salpêtrière Retardation Rating Scale, (2) for self-report, the International Physical Activity Questionnaire; and for physiology, (3) Actigraphy, which accounts for gross motor behavior, (4) Gait velocity, and (5) coin rotation task to assess manual dexterity. Results The ANCOVAs comparing the 3 groups revealed differences between patients with PS and HC in expert ratings, self-report, and instrumental measures (all P ≤ .001). Patients with PS also scored higher in expert ratings and had lower instrumental activity levels compared to patients without PS (all P ≤ .045). Instrumental activity levels correlated with an expert rating of PS (rho = −0.51, P-fdr corrected <.001) and classified similarly at 72% accuracy. Conclusions PS is characterized by slower gait, lower activity levels, and slower finger movements compared to HC. However, only actigraphy and observer ratings enable to clearly disentangle PS from non-PS patients. Actigraphy may become the standard assessment of PS in neuroimaging studies and clinical trials.

The pathobiology of psychomotor slowing in psychosis: altered cortical excitability and connectivity

“…PS also differed from HC in FA and rsFC. Thus, the group not only has distinct behavioural patterns, 24 but also aberrant neural connectivity in the motor system. 27 , 86 …”

“…Psychomotor slowing is frequent in schizophrenia and thought to arise from poor movement preparation, altered motor coordination, impaired movement execution as well as complex interactions with altered emotion processing. 15-23 , 24 The phenomenon can be assessed with clinical rating scales, instrumental measures such as actigraphy, or neurocognitive tests. 6 , 15 Within schizophrenia, we found a subgroup with severe psychomotor slowing that presented with reduced physical activity, slower gait and compromised dexterity.…”

“… 6 , 15 Within schizophrenia, we found a subgroup with severe psychomotor slowing that presented with reduced physical activity, slower gait and compromised dexterity. 24 Thus, a proportion of psychosis patients presents with severely altered behaviour, pointing to distinct pathobiology in subjects with psychomotor slowing.…”

“…Given that schizophrenia is associated with (i) alterations in the motor circuitry including higher neural resting-state activity in the sensorimotor cortex; and (ii) lower GABAergic tone and lower intracortical inhibition in the motor cortex, we may speculate that these alterations are most pronounced in patients with current psychomotor slowing, who may present distinct pathobiology. 24 Thus, this study aimed to test the differences in cortical excitability measures between healthy controls and patients with schizophrenia with or without psychomotor slowing. Furthermore, we probed whether cortical excitability measures were linked to specific alterations of structural and functional brain connectivity in schizophrenia.…”

Psychomotor slowing alters gait velocity, cadence, and stride length and indicates negative symptom severity in psychosis

“…Motor rating scales. Psychomotor slowing was assessed using the SRRS 33 that has been applied across depression and the broad psychosis spectrum 10,24,66,67 . As the SRRS comprises items on motor behaviour, cognitive impairment, and depressive symptoms, researchers have created a subscore solely comprised of motor items, the motor-SRRS (mSRRS 10 ).…”