Digitized analysis of abnormal hand–motor performance in schizophrenic patients

doi:10.1016/S0920-9964(99)00185-1

Schizophrenia Research

Volume 45, Issues 1–2, 29 September 2000, Pages 133-143

https://doi.org/10.1016/S0920-9964(99)00185-1 Get rights and content

Abstract

Many studies have shown a high prevalence of discrete neuromotor disturbances in schizophrenic patients. It was hypothesized that these disturbances are lateralized and reflect a neurodevelopmental disorder underlying schizophrenia. A new method for assessing subtle motor dysfunction and hemispheric asymmetries is the registration of hand movements with a digitizing tablet. Using this method, we studied hand–motor dysfunction and its lateralization in schizophrenics, as compared with healthy controls.

All subjects (27 schizophrenic patients, 13 of them without neuroleptic medication, the others under neuroleptics; 31 healthy controls) drew super-imposed concentric circles. We computed kinematic parameters reflecting velocity and automatization to quantify neurological soft signs (NSS).

The patients had significant impairments of regularity of repetitive hand movements, as compared with the healthy controls (F≥5.35; p≤0.024^∗). Comparing differences of left- and right-hand performance between patients and controls, we found longer stroke duration (F=(15,98); p=0.000***) and decreased automatization (F=18,14; p=0.000***), especially on the left side in schizophrenic patients.

Measuring hand movements with a digitizing tablet is a sensitive method for assessing subtle motor dysfunction in schizophrenic patients, not reflected in the scores of clinical scales. Our findings show NSS in schizophrenic patients, independently of neuroleptics. Further, the hypothesis of lateralization of cerebral structures generating NSS towards the right hemisphere in schizophrenia is supported.

Introduction

Neurological soft signs (NSS) are discrete motor and sensory disorders that cannot be linked to special cerebral lesions or dysfunction. Kraepelin was one of the first psychiatrists who observed NSS in many schizophrenic patients and described them (Kraepelin, 1919). Schröder et al. (1992) could demonstrate that NSS are more often found in schizophrenic patients than in other psychiatric patients or healthy controls. They are independent of neuroleptic medication in this population (Gupta et al., 1995). We also know that there exists a close relationship between NSS, especially disorders of motor coordination, and negative symptoms in schizophrenia (Heinrichs and Buchanan, 1988, Manschreck et al., 1990, Schröder, 1998).

Several investigators have studied the asymmetry of NSS in schizophrenic patients, too. Some of these studies support the hypothesis of left-hemispheric deficiencies in schizophrenic patients (e.g., Torrey, 1980). This hypothesis is supported by many morphological and functional studies. Crow (1990) gives an overview of these findings and postulates that abnormally reduced cerebral asymmetries reflect a genetically determined disturbance of cerebral development in schizophrenic patients.

However, some authors have reported motor abnormalities related to dysfunction in the right cerebral hemisphere in schizophrenia leading to significantly increased hemispheric asymmetries (e.g., Niethammer et al., 1998, Walker et al., 1994).

In most of these studies, clinical rating scales and neurological examinations were used in order to register NSS. Direct kinematic measurements of hand–motor dysfunction in schizophrenic patients offer a new approach. They are an objective tool for investigating functional disturbances reflecting the pathophysiology of psychiatric disorders. In a methodological study, we could show that kinematic handwriting parameters have middle to high temporal stability in healthy subjects and that hand–motor performance is influenced by some variables, especially age (Mergl et al., 1999). Therefore, this variable has to be controlled in studies using digitized analysis of hand movements in psychiatric patients.

So far, only a few scientists have used kinematic measurement methods for investigating hand–motor asymmetries in schizophrenic patients. Lohr and Caligiuri (1997) instructed 49 older schizophrenic patients, 6 manic patients, 10 patients with bipolar affective disorders and 30 healthy controls “to press and hold a stable level of force with their index finger placed on a strain gauge, while following a stable target representing that force on a computer monitor” (Lohr and Caligiuri, 1997, p. 196). The coefficient of force variation served as measure for hand-force instability. The hand–motor asymmetry score resulted from subtracting the right-hand force error score from the left one. A negative score indicates less stability for the right hand, whereas a positive score reflects less stability for the left hand. There were significant differences between the asymmetry scores of the schizophrenic patients and those of the control groups: the asymmetry score of the schizophrenic patients was negative, the score of manic patients was positive, and that of bipolar patients in between. Healthy controls showed an asymmetry score of approximately 0. Lohr and Caligiuri (1997) interpret these results as indicating left-hemispheric dysfunctions in schizophrenia and right-hemispheric dysfunctions in patients with mania.

In contrast, Gallucci et al. (1997) found little evidence of abnormal hemispheric specialization in schizophrenia concerning hand–motor function. The authors registered hand movements of schizophrenic patients and healthy controls who drew guirlands and arcades with both their dominant and non-dominant hand using a digitizing graphic tablet. In order to examine the NSS, they computed several kinematic parameters (e.g., stroke length and duration). Only one measure indicated reduced functional asymmetries of hand movements in schizophrenic patients (regularity of stroke duration). These findings do not confirm the theory of altered motor asymmetry in schizophrenia, but they do not falsify Crow's theory of structural temporal lobe asymmetries in schizophrenia (Crow, 1990): functional asymmetries do not always reflect structural asymmetries and vice versa.

In the present study, we used the new method of digitizing handwriting analysis for comparing schizophrenic patients with healthy controls concerning hand–motor dysfunction, assuming greater impairments for the patients. The second hypothesis, derived from the assumption of left-hemispheric dysfunction in schizophrenia, dealt with the differences between hand–motor performance of the dominant and the non-dominant hand. These differences were expected to be significantly reduced in schizophrenic patients compared with healthy controls.

In an additional explorative analysis, we examined the relationship between medication, psychopathology and cognitive status on one side, and hand–motor performance in schizophrenia on the other.

Section snippets

Subjects

We examined 27 partially remitted schizophrenic in-patients diagnosed according to ICD-10 criteria (F20.x) (Dilling et al., 1993) (21 male and six female) and having mean ages of 31.04 (range 20–54; SD 8.98) years. Their mean illness duration was 7.04 years (range 0.2–27; SD 7.12). All patients had given written consent to their participation, according to the Declaration of Helsinki (World Medical Association, 1997). Patients with neurological or internistic disease, mental retardation or

Results

Mean kinematic scores from the hand–motor examination are presented in Table 2.

Overall, the repetitive hand movements of schizophrenic patients were less consistent and automatized than those of the healthy controls; time spent in acceleration and mean stroke duration were significantly longer in patients.

Anomalous functional asymmetries occur for stroke duration and automatization. Whereas patients' stroke duration was obviously longer for the left than the right hands, this effect was less

Discussion

Our results clearly confirm the first hypothesis that the significantly higher prevalence of NSS in schizophrenic patients can be detected with digitizing graphic tablets analyzing fine motor performance. Particularly, we could demonstrate that the patients' simple, repetitive hand–motor performance is significantly impaired as to the degree of automatization, mean peak acceleration, mean stroke duration and regularity of velocity, acceleration and stroke duration. The loss of automatization

Acknowledgements

We gratefully acknowledge the assistance of cand. med. Willi Flatz and cand. med. Safet Sokullu in carrying out the hand motor investigations of the schizophrenic patients and Julian Rihl and Marlies Karsch in examining healthy controls' hand–motor performance.

The patients are gratefully acknowledged for their readiness to participate in our study.

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Digitized analysis of abnormal hand–motor performance in schizophrenic patients

Abstract

Introduction

Section snippets

Subjects

Results

Discussion

Acknowledgements

Control. Clin. Trials

Schizophr. Res.

Biol. Psychiatry

Schizophr. Res.

Biol. Psychiatry

J. Neurosci. Meth.

J. Neurosci. Meth.

Neuropsychologia

The Extrapyramidal Symptom Rating Scale

Can. J. Neurol. Sci.

Temporal lobe asymmetries as the key to the etiology of schizophrenia

Schizophr. Bull.

Computational analysis of open loop handwriting movements in Parkinson's disease: a rapid method to detect dopamimetic effects

Mov. Disord.

Gestörte Hirnfunktionen bei Schizophrenie

Neurological soft signs in neuroleptic-naive and neuroleptic-treated schizophrenic patients and in normal comparison subjects

Am. J. Psychiatry