%0 Journal Article
%T Disrupted Central Inhibition after Transcranial Magnetic Stimulation of Motor Cortex in Schizophrenia with Long-Term Antipsychotic Treatment
%A Aulikki Ahlgr¨¦n-Rimpil£¿inen
%A Hannu Lauerma
%A Seppo K£¿hk£¿nen
%A Ilpo Rimpil£¿inen
%J ISRN Psychiatry
%D 2013
%R 10.1155/2013/876171
%X Aims. Schizophrenia is a neuropsychiatric disorder associated with mental and motor disturbances. We aimed to investigate motor control, especially central silent period (CSP) in subjects with schizophrenia ( ) on long-term antipsychotic treatment compared to healthy controls ( ). Methods. Latency and duration of motor evoked potentials (MEPs) and CSPs were measured with the help of single pulse transcranial magnetic stimulation (TMS) and intramuscular electrodes. After stimulation of the dominant and nondominant motor cortex of abductor digiti minimi (ADM) and tibialis anterior (TA) muscle areas, respective responses were measured on the contralateral side. Results. MEPs did not differ significantly between the groups. Multiple CSPs were found predominantly in subjects with schizophrenia, which showed a higher number of CSPs in the dominant ADM and the longest summarized duration of CSPs in the nondominant ADM ( ) compared to controls. Conclusions. There were multiple CSPs predominantly in the upper extremities and in the dominant body side in subjects with schizophrenia. Behind multiple CSPs may lie an impaired regulation of excitatory or inhibitory neurotransmitter systems in central motor pathways. Further research is needed to clarify the role of the intramuscular recording methods and the effect of antipsychotics on the results. 1. Introduction Transcranial magnetic stimulation (TMS) of the motor cortex is a useful non-invasive method that enables investigation of motor cortex excitability and central inhibitory mechanisms in the central nervous system. The commonly measured parameters of the motor responses include motor conduction time (MCT), transient suppression of ongoing motor activity (central silent period = CSP), and latency and duration of CSP and motor evoked potential (MEP) amplitude. The lowest stimulus intensity that induces an appropriate response in the target muscle is considered to be motor threshold of the motor cortex [1]. The induction mechanism of the central silent period (CSP) is not completely understood. It has been suggested to consist of an initial part of spinal origin and of a later part of cortical origin [2¨C4] or to be of cortical, supraspinal origin, being generated in the primary motor cortex [5]. The CSP is probably controlled by complex subcortical extrapyramidal systems with numerous interneuronal synapses associated with (GABAergic) inhibitory circuits [6]. There are several TMS studies dealing with motor control in schizophrenia [7, 8], which is considered to be a neuropsychiatric disorder associated with
%U http://www.hindawi.com/journals/isrn.psychiatry/2013/876171/