Asperger's disorder (AD) is a disorder in the autism spectrum. This new diagnostic concept, still under some debate (Volkmar et al., 2000), indicates a syndrome characterized by behavioral features typical of autism in the absence of significant deficits of cognitive functioning (American Psychiatric Association, 2000). Hypodopaminergia in autism (Ernst et al., 1997) may lead to secondary dopaminergic hypersensitivity (Segawa and Nomura, 1992). The dopaminergic dysfunction and the structural abnormalities in the basal ganglia (Jacobson et al., 1988) may explain the presumed neuroleptic intolerance in autistic patients (Scahill and Koenig, 1999) and the primary motor abnormalities (Leary and Hill, 1996).
Movement disorders are common in AD, manifesting clinically as clumsiness Gillberg, 1995, Smith, 2000 and Weimer et al., 2001, a lack of motor coordination (Miyahara et al., 1997), and stereotypic, repetitive movements (Ringman and Jankovic, 2000). Furthermore, AD patients may suffer from other motor disorders associated with comorbid disorders such as Tourette's syndrome (TS) (Kadesjö and Gillberg, 2000) and attention deficit hyperactivity disorder (ADHD) (Ghaziuddin et al., 1998). Both TS and ADHD are characterized by motor symptoms and show some evidence of dopaminergic dysregulation and striatal dysfuction Malison et al., 1995, Seeman and Madras, 1998, Thapar et al., 1999 and Sheppard et al., 2000.
Actometry (actigraphy) is a direct method for measuring motor activity both quantitatively and qualitatively, developed from accelerometry. Although validated for sleep-studies (Sadeh et al., 1989), it has been increasingly used in neuropsychiatry to record day time motor activity (Teicher, 1995) in ADHD subtypes Porrino et al., 1983 and Dane et al., 2000, antisocial personality disorder (Virkkunen et al., 1994), and neuroleptic-induced movement disorders (Poyurovsky et al., 2000), for example. Multichannel movement recording offers new opportunities to specify extrapyramidal movement disorders Foerster and Smeja, 1999 and Tuisku et al., 1999.
We hypothesized that lower limb motor activity may be abnormal in AD, in view of the susceptibility to movement disorders, comorbidity aspects and the evident dopaminergic dysfunction in infantile autism. Moreover, we wanted to determine whether motor symptoms related to hypodopaminergia, such as akathisia or RLS (Turjanski et al., 1999), would appear. Both akathisia and RLS demonstrate increased motor activity during rest Montplaisir et al., 1998 and Tuisku et al., 1999 and a specific actometric movement pattern Kazenwadel et al., 1995, Collado-Seidel et al., 1999 and Tuisku et al., 1999.
To test our hypothesis, we performed three-channel actometry for the quantitative and qualitative assessment of rest activity in AD. We wanted to compare the AD movement indices and the movement patterns with the normal rest activity of healthy controls.
