Differenzierung motorischer kortiko-subkortikaler Netzwerke mit funktioneller Magnetresonanztomographie

Abstract

Cortico-subcortical connections are organized in circuits. These are divided in a tripartite manner into the sensorimotor, associative and limbic loop. Corresponding subdivision has been shown for cortical areas as well as for basal ganglia. Evidence argues for a lateralized organization of the sensorimotor loop and a bilateral organization of the associative loop. Despite much research in this field in the last decades, an overall functional map of the corticostriatal circuits is lacking, and distinction of the circuits has been difficult. Thus, the aim was a comprehensive functional visualization and differentiation of the sensorimotor and the associative circuit. As a new approach, laterality features were used to distinguish between the circuits within one single motor task. 24 healthy boys performed self-paced index finger tapping with each hand separately during functional magnetic resonance imaging at 3 Tesla. The sensorimotor circuit was hypothesized to be clearly lateralized. Indeed, a contrast analysis for left against right hand movement revealed lateralized activation in typical sensorimotor regions such as primary sensorimotor cortex, caudal supplementary motor area (SMA), caudal putamen and thalamus. The associative circuit was hypothesized to be represented bilaterally. A conjunction analysis confirmed bilateral involvement of known associative regions including pre-SMA, rostral SMA and rostral putamen. A clear functional visualization of two distinct corticostriatal circuits is provided, as well as a new means to discriminate the sensorimotor and associative circuit easily by their laterality characteristics. This new approach can prove useful in early detection, diagnostics and evaluation of therapeutic intervention of movement disorders such as Parkinson's disease, Chorea Huntington, an ischemic stroke or in Tourette syndrome. Additionally, the results extend previous findings of a modified functional subdivision of the SMA.