Developmental improvements in dynamic control of fingertip forces last throughout childhood and into adolescence

Abstract

Dayanidhi S, Hedberg Å, Valero-Cuevas FJ, Forssberg H. Developmental improvements in dynamic control of fingertip forces last throughout childhood and into adolescence.

Decrease in Muscle Contraction Time Complements Neural Maturation in the Development of Dynamic Manipulation

“…A prior version of this test has been shown to capture a unique trait of dynamic fingertip force coordination, which is different from pinch strength in typically developing children through adolescence (Vollmer et al, 2010). Moreover, pinch strength is a poor predictor of dynamic manipulation abilities per se given that both experimental and analytical results show that muscle strength (which can be used to stiffen the fingers) does not help achieve higher levels of performance during these unstable dynamical tasks (Venkadesan et al, 2007;Dayanidhi et al, 2013).…”

“…To test dynamic manipulation abilities, subjects were asked to use their dominant index and thumb to compress an instrumented slender spring prone to buckling as far as possible, and hold for at least 3 s. This spring, based on the validated Strength-Dexterity Test (Valero-Cuevas et al, 2003), becomes more unstable as it is compressed, requiring faster control of fingertip force direction with increasing compression making it impossible to compress fully (Venkadesan et al, 2007;Dayanidhi et al, 2013). The maximal level of compression (ϳ2-3 N) is therefore a surrogate for the maximal level of instability that can be controlled and therefore a measure of dynamic manipulation ability.…”

“…For the dynamic manipulation task, we identified the average maximal level of compression as described previously (Venkadesan et al, 2007;Dayanidhi et al, 2013). For each subject, the mean of the force during the sustained compression phases was calculated for all their attempts, and three maximum values were averaged to create a metric for dynamic manipulation ability, which we call the dynamic manipulation score (DMS), in units of grams of force (gmf).…”

“…Dexterous manipulation capabilities have a prolonged period of development during childhood (Forssberg et al, 1991) and adolescence (Vollmer et al, 2010;Dayanidhi et al, 2013). These improvements have been primarily attributed to neural factors, including developmental plasticity of the corticospinal tract Olivier et al, 1997;Martin, 2005) via microstructural changes (Lebel et al, 2008), myelination , and synaptogenesis .…”

Activity in the brain network for dynamic manipulation of unstable objects is robust to acute tactile nerve block: An fMRI study

“…In recent fMRI studies manipulation of unstable objects, which puts a larger demand on the on-line control of the fingertip forces preventing the object to buckle and slip out of the hand, was investigated (Mosier et al, 2011;Holmstrom et al, 2011). The unstable objects were constructed by compression springs that can be built with different requirements for strength (i.e., stiffness) and dexterity (i.e., propensity to buckle), respectively (ValeroCuevas et al, 2003, Dayanidhi et al, 2013. It was discovered that specific parts of the network for dexterous manipulation are more involved in the control of the direction of the fingertip force vector (i.e., bilateral primary motor cortex, left premotor cortices and intraparietal sulcus, right somatosensory cortex and bilateral cerebellum), while different parts of the left primary sensory-motor cortices and bilateral cerebellum are more involved in the control of force magnitude.…”