Activity- and use-dependent plasticity of the developing corticospinal system☆

Abstract

The corticospinal system (CS), critical for controlling skilled movements, develops during the late prenatal and early postnatal periods in all species examined. In the cat, there is a sequence of development of the mature pattern of terminations of corticospinal tract axons in the spinal gray matter, followed by motor map development of the primary motor cortex. Skilled limb movements begin to be expressed as the map develops. Development of the proper connections between CS axons and spinal neurons in cats depends on CS neural activity and motor behavioral experience during a critical postnatal period. Reversible CS inactivation or preventing limb use produces an aberrant distribution of CS axon terminations and impairs visually guided movements. This altered pattern of CS connections after inactivation in cats resembles the aberrant pattern of motor responses evoked by transcranial magnetic stimulation in hemiplegic cerebral palsy patients. Left untreated, these impairments do not resolve. We have found that activity-dependent processes can be harnessed in cats to reestablish normal CS connections and function. This finding suggests that CS connectivity and function might some day be restored in hemiplegic cerebral palsy.

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

“…Our finding of continuous development into adolescence also suggests that the window of opportunity for rehabilitation in children with neurodevelopmental disabilities is longer, assuming that the plasticity, i.e., "critical period," of the involved sensorimotor system remains high during this period (Armand et al 1997;Martin et al 2007). This interpretation is supported by findings in these children showing improvements in hand function with intense practice even in their adolescent years (Bonnier et al 2006;Eliasson et al 2006;Gordon et al 2007;Kuhtz-Buschbeck et al 2000).…”

“…In parallel with the development of the ascending and descending pathways between brain and hand, there are striking developmental processes taking place in the brain gray and white matter during childhood up to adolescence, e.g., expansion of the white matter and pruning of the cortical gray matter (Asato et al 2010;Giedd et al 1999;Lebel and Beaulieu 2011;Lebel et al 2008;Martin et al 2007;Paus et al 1999). We (Ehrsson et al 2001) demonstrated earlier that there is a greater activity in the fronto-parietal sensorimotor areas during the control of smaller forces than larger forces, with control of larger forces associated with increased activity in the M1 region.…”

Plasticity in the developing brain: Implications for rehabilitation

“…The active side maintains bilateral terminations at the expense of the silenced side. These experiments found that immobilization of an extremity also reduced innervation of the spinal cord by contralateral corticospinal tracts, suggesting that sensory activity from the limb also was important for plasticity of the developing corticospinal tracts [Martin et al, 2007].…”

La especialización hemisférica y la regulación de la conducta motora desde la perspectiva de la neurociencia cognitiva

“…La evidencia apunta a una representación reducida en el área M1 del hemisferio derecho en comparación con el izquierdo en las personas diestras, relacionado con una disminución de la destreza de la mano no dominante. 54 En las áreas de asociación, las funciones especializadas relacionadas con la planificación no están muy desarrolladas, 55 probablemente debido a la fuerte demanda de "pistas" para seleccionar una determinada representación externa que involucra el procesamiento motor de la nueva exploración de situaciones. 56 El tema del procesamiento de la exploración de nuevas situaciones es consistente con la teoría de que el hemisferio izquierdo actúa en aspectos del movimiento en circuito abierto (en base a programas motores bien establecidos), mientras que el hemisferio derecho es crucial para todos los aspectos del movimiento en circuito cerrado (dependiendo de la retroalimentación sensorial).…”