Dual-task study of cognitive and postural interference: a preliminary investigation of the automatization deficit hypothesis of developmental co-ordination disorder.

BACKGROUND: The purpose of this study was to investigate whether children with developmental co-ordination disorder and balance problem (DCD-BP) had greater problems than controls in performing a primary balance task while concurrently completing different cognitive tasks varying in oral or listening cognitive complexity, as well as to investigate the automatization deficit hypothesis of DCD-BP. METHODS: Children with DCD-BP (n= 39), along with age-matched control counterparts (n= 39), were placed on automatic processing situation under dual-task conditions. All children were required to perform a primary task, five dual-task paradigms (oral counting task, auditory-verbal reaction task, auditory-choice reaction task, auditory-memory task and articulation alone) and an eyes-closed balancing task. RESULTS: In the primary task condition, the differences were not statistically significant (P= 0.393) between children with and without DCD-BP. However, children with DCD-BP were significantly more impaired on three of five dual-task conditions (oral counting task: P= 0.003; auditory-verbal reaction task: P= 0.011; auditory-memory task: P= 0.041) compared with the single-task situation, with the exception of the auditory-choice reaction task (P= 0.471) and articulation alone (P= 0.067). CONCLUSIONS: These results suggest that children with DCD-BP were more cognitively dependant and may have an automatization deficit.

Common abnormal kinetic patterns of the knee in gait in spastic diplegia of cerebral palsy.

We studied the kinetic characteristics of the knee in patients with spastic diplegia. Twenty three children with spastic diplegia were recruited and had their 46 limbs categorised into the following four groups: jump (n=7), crouch (n=8), recurvatum (n=14) and mild (n=17). In the crouch pattern, the patients usually had a larger and longer lasting internal knee extensor moments in stance suggesting that rectus femoris had a relatively high activation. In the recurvatum pattern, the internal knee flexor moment was large and long lasting in stance. The biceps femoris showed less activity on EMG although the knee flexor moment was large and we concluded that the soft tissue behind the knee joint provided this flexor moment. In the jump knee pattern there was abnormal power generation at the knee and ankle joints in initial stance, which did not contribute to normal progression but aided upward body motion. In the mild group the kinetic data was similar to that seen in normal children. Knowledge of kinetic patterns in these patients may help in their subsequent management.

Frequency spectral characteristics of standing balance in children and young adults.

Past research has shown that spectral frequency characteristics of a balance control system may be useful for early detection of minor changes in the system. Since there is a lack of information regarding the frequency spectrum of children's balance control system, this study was undertaken to investigate and compare the spectral frequency characteristics of standing balance control between children and young adults under altered sensory environments. Seventeen children (9 females, 8 males, mean age 7.8+/-0.9 years) and the same number of female and male young adults (mean age 21.1+/-1.3 years) were tested for standing balance under six sensory conditions. These conditions were created by crossing the three levels of the visual factor (open eye, closed eye, sway-referenced vision) with the two levels of the somatosensory factor (fixed foot support, compliant foot support). The median spectral frequencies of the shear forces in the anterior-posterior (A/P) and the medial-lateral (M/L) directions were used as dependent variables. The results showed that children had higher median spectral frequency of the A/P shear force than young adults and this difference was not affected by the somatosensory factor. The median spectral frequency in the M/L direction was not different between the groups. The higher rate of body mass vibration of children in the A/P direction implies that children may not have fully developed the ankle strategy for maintaining standing balance, but nonetheless have developed the same efficiency of using vision for their reference of standing balance.

Vestibular system in performance of standing balance of children and young adults under altered sensory conditions.

Inputs from the visual, somatosensory and vestibular systems must be integrated efficiently to activate appropriate motor responses in maintaining optimal balance. This study examined the standing balance of 17 children (7 to 10 years old) and 17 young adults (19 to 23 years old) as a function of sensory organization, sensory system efficiency, and postural strategy adopted. Tests of standing balance were administered under six sensory conditions created by simultaneous alteration of the visual (full, occluded, or sway-referenced) and the somatosensory inputs (fixed-foot or compliant-foot support). The sway area and the sway amplitude of the center of pressure were measured and analyzed. Three findings are notable. The function of sensory organization for balance control was poorer for the children than the young adults. The functional efficiency of the somatosensory and the visual systems of children have developed to the young adult level, but that of the vestibular system has not. There was no difference between children and young adults in hip control, but there was in ankle control when the vestibular input was the only reliable source of sensory input. These results suggest that the functional efficiency of the vestibular system in children 7 to 10 years of age may still be developing. This may account for their poorer function of sensory organization and lower performance of standing balance.

Performance of static standing balance in children with spastic diplegic cerebral palsy under altered sensory environments.

Seven children with spastic diplegic cerebral palsy and 14 age- and gender-matched nondisabled children participated in the present study for an investigation and comparison of their static standing balance under altered sensory environments. The type of visual input (full, occluded, or sway referenced vision) and the type of somatosensory input (fixed or compliant foot support) were varied factorially to give six sensory environments. Each participant was tested barefooted for 30 s under all six conditions. A force platform collected the ground reaction force, from which standing balance was calculated as the sway area of the center of pressure. The results showed that when somatosensory information was reliable (fixed foot support), there was no significant difference in stance stability between the children with spastic diplegic cerebral palsy and their matched controls, and both types of children were equally affected by the type of visual input. However, when somatosensory information was unreliable (compliant foot support), the difference in stance stability between the children with spastic diplegic cerebral palsy and their matched controls was significantly greater when the visual input was deprived (occluded) or unreliable (sway referenced) than when it was reliable. These results suggest that the children with spastic diplegic cerebral palsy may have difficulties in resolving intersensory conflicts for maintenance of standing balance, or the demands of motor control in sensory conflict conditions outweigh the motor ability of children with spastic diplegic cerebral palsy.