May Functional Imaging be Helpful for Behavioral Assessment in Children? Regions of Motor and Associative Cortico-Subcortical Circuits Can be Differentiated by Laterality and Rostrality.

BACKGROUND: Cortico-subcortical circuits are organized into the sensorimotor, associative, and limbic loop. These neuronal preconditions play an important role regarding the understanding and treatment of behavioral problems in children. Differencing evidence argues for a lateralized organization of the sensorimotor loop and a bilateral (i.e., non-lateralized) organization of the associative loop. However, a firm behavioral-neurobiological distinction of these circuits has been difficult, specifically in children. OBJECTIVES: Thus, the aim was a comprehensive functional visualization and differentiation of the sensorimotor and the associative circuit during childhood. As a new approach, laterality and rostrality features were used to distinguish between the two circuits within one single motor task. METHODS: Twenty-four healthy boys performed self-paced index finger tapping with each hand separately during functional magnetic resonance imaging at 3 Tesla. RESULTS: 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. A conjunction analysis confirmed bilateral involvement of known associative regions including pre-SMA, rostral SMA, and rostral putamen. CONCLUSION: A functional visualization of two distinct corticostriatal circuits is provided in childhood. Both the sensorimotor and associative circuit may be discriminated by their laterality characteristics already in minors. Additionally, the results support the concept of a modified functional subdivision of the SMA in a rostral (associative) and caudal (motor) part. A further development of this approach might help to nurture behavioral assessment and neurofeedback training in child mental health.

Finger tapping-related activation differences in treatment-naïve pediatric Tourette syndrome: a comparison of the preferred and nonpreferred hand.

BACKGROUND: Disturbances of motor circuitry are commonly encountered in Tourette syndrome (TS). The aim of this study was to investigate simple motor performance differences between boys with TS and healthy controls. METHODS: We attempted to provide insight into motor network alterations by studying a group of treatment-naïve patients suffering from 'pure' TS, i.e., without comorbid symptomatology at an early stage of disease. We used functional MRI to compare activation patterns during right (preferred) and left (nonpreferred) index finger tapping between 22 TS boys (12.6 ± 1.7 years) and 22 age-matched healthy control boys. RESULTS: Boys with TS revealed altered motor network recruitment for right (dominant) and left (nondominant) index finger tapping. Brain activation patterns in response to index finger tapping of the nonpreferred left hand reflected the most prominent differences, including activation decrease in contralateral sensorimotor cortex while recruiting premotor and prefrontal regions along with the left inferior parietal lobule to a greater extent. CONCLUSIONS: This study demonstrates clear functional differences of simple index finger tapping in early-stage TS. We suggest that this reflects the requirement for additional brain networks to keep a normal performance level during the actual task and adaptive mechanisms due to continuous tic suppression and performance in TS.