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Event-related Potentials During Target-response Tasks to Study Cognitive Processes of Upper Limb Use in Children with Unilateral Cerebral Palsy
Published on: January 11, 2016
Children with congenital spastic hemiplegia obey Fitts' Law in a visually guided tapping task
B C M Smits-Engelsman1, E A A Rameckers, J Duysens
1Motor Control Lab, Department of Kinesiology, K.U. Leuven, Leuven, Belgium. bengelsman@avansplus.nl
Insights
Children with cerebral palsy (CP) still follow Fitts' Law in aiming tasks, demonstrating the law's robustness even with motor control challenges. This study confirms Fitts' Law applies to children with congenital spastic hemiplegia (CSH).
Area of Science:
- Motor Control
- Human Movement Science
- Neurorehabilitation
Background:
- Fitts' Law typically governs precise aiming movements.
- Children with cerebral palsy (CP) exhibit significant motor difficulties, raising questions about their adherence to Fitts' Law.
- Assessing motor control in CP is complex, often confounding motor output deficits with cognitive processing issues.
Purpose of the Study:
- To investigate whether children with congenital spastic hemiplegia (CSH) adhere to Fitts' Law during a simple aiming task.
- To determine if Fitts' Law is robust enough to apply to individuals with central nervous system damage affecting motor control.
- To differentiate motor output deficits from cognitive processing in children with CP using a controlled task.
Main Methods:
- A simple tapping task was designed to evaluate Fitts' Law.
- Twenty-two children with CSH and 22 typically developing children participated.
- Movement time was measured for targets of varying width (2.5-5 cm) and distance (10-20 cm), yielding Indices of Difficulty (ID) from 2-4 bits.
Main Results:
- Children with CSH showed prolonged reaction and movement times in their affected hand compared to controls.
- Movement time in children with CSH was significantly related to the Index of Difficulty, consistent with Fitts' Law.
- While the intercept (tapping movement time) was higher in CSH, the slope (task difficulty sensitivity) and cognitive processing capacity were similar to controls.
Conclusions:
- Children with congenital spastic hemiplegia (CSH) demonstrate adherence to Fitts' Law, despite pronounced fine motor control impairments.
- Fitts' Law appears highly robust, applicable even in populations with central nervous system damage.
- The findings suggest that basic motor control principles, as described by Fitts' Law, remain intact in children with CSH.
Abstract:
Fitts' Law is commonly found to apply to motor tasks involving precise aiming movements. Children with cerebral palsy (CP) have severe difficulties in such tasks and it is unknown whether they obey Fitts' Law despite their motor difficulties. If Fitts' Law still does apply to these children, this would indicate that this law is extremely robust and that even performance of children with damaged central nervous systems can adhere to it. The integrity of motor control processes in spastic CP is usually tested in complex motor tasks, making it difficult to determine whether poor performance is due to a motor output deficit or to problems related to cognitive processes since both affect movement precision. In the present study a simple task was designed to evaluate Fitts' Law. Tapping movements were evaluated in 22 children with congenital spastic hemiplegia (CSH) and 22 typically developing children. Targets (2.5 and 5 cm in width) were placed at distances of 10 and 20 cm from each other in order to provide Indices of Difficulty (ID) of 2-4 bits. Using this Fitts' aiming task, prolonged reaction and movement time (MT) were found in the affected hand under all conditions in children with CSH as compared to controls. Like in the control group, MT in children with CSH was related to ID. The intercept 'a', corresponding to the time required to realize a tapping movement, was higher in the affected hand of the children in the CSH group. Although, the slope b (which reflects the sensitivity of the motor system to a change in difficulty of the task) and the reciprocal of slope (that represents the cognitive information processing capacity, expressed in bits/s) were similar in both groups. In conclusion, children with CSH obey Fitts' Law despite very obvious limitations in fine motor control.
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