Summary

It is widely held that schizophrenia is associated with a variety of subtle sensory and motor impairments – so called neurological soft signs – that may impact on manual dexterity. Neurological soft signs (NSS) in schizophrenia appear to be part of the underlying disorder. The motor deficit of the hand, however, may also worsen as a side effect of antipsychotic treatment. Within the theoretical framework of internal models schizophrenia has been associated with a deficit of self-monitoring and awareness of action. Deficient monitoring of the sensory consequences of voluntary movement may be directly related to the motor deficit to be found in schizophrenia. This chapter summarizes kinetic and kinematic aspects of impaired manual dexterity in schizophrenia and discusses the motor disability within the context of internal models for the sensorimotor processing of voluntary actions.

Introduction

Early in the 20th century, Bleuler (1908) and Kraepelin (1919) described several motor abnormalities in schizophrenia, such as problems in the sequencing and spacing of steps when walking and dyscoordination of hand and arm movements when performing handiwork and crafts. In this era antipsychotic drugs did not exist and, consequently, these early clinical observations cannot simply be considered a side effect of antipsychotic treatment. Today, deficits of fine motor performance, also referred to as neurological soft signs (NSS), are still observed in a substantial proportion of schizophrenic subjects, but their nature is still not completely understood and their semiology is not easily distinguishable from side effects of antipsychotic treatment.