Motor system plasticity after unilateral injury in the developing brain

Abstract

In maturity, motor skills depend on the corticospinal tract (CST) and brainstem pathways that together synapse on interneurons and motoneurons in the spinal cord. Descending signals to spinal neurons that mediate voluntary control can be distinguished from peripheral sensory signals, primarily for feedback control. These motor system circuits depend initially on developmental genetic mechanisms to establish their connections and neural activity- and use-dependent synaptic refinement during the early postnatal period to enable motor skills to develop. In this review we consider four key activity-dependent developmental mechanisms that provide insights into how the motor systems establish the proper connections for skilled movement control and how the same mechanisms also inform the mechanisms of motor impairments and developmental plasticity after corticospinal system injury: (1) synaptic competition between the CSTs from each hemisphere; (2) interactions between the CST and spinal cord neurons; (3) synaptic competition between the CST and proprioceptive sensory fibres; and (4) interactions between the developing corticospinal motor system and the rubrospinal tract (RuST). Our findings suggest that the corticospinal motor system effectively ‘oversees’ development of its subcortical targets through synaptic competition and trophic-like interactions and this has important implications for motor impairments after perinatal cortical stroke.

Intraventrikuläre Hirnblutungen des Frühgeborenen

“…Bei Neugeborenen mit Hirnblutung profitiert die langfristige Entwicklung der motorischen Fähigkeiten massiv von der Plastizität des kindlichen Gehirns. Beispielsweise können nicht kreuzende kortikospinale Fasern [21] für eine Innervation durch die ipsilaterale Hemisphäre sorgen, wenn die kontralaterale durch eine Blutung oder Ischämie geschädigt wurde [22]. Nicht kreuzende kortikospinale Fasern gibt es in unterschiedlichem Ausbildungsgrad auch bei Erwachsenen.…”

Neuroscience underlying rehabilitation: what is neuroplasticity?

“…Current understanding of neuroplasticity implies that synapses, fibres, and cells are overproduced early in maturation and subsequently compete for survival and efficacy within functional networks. Local (in)activity induces local plasticity and also widespread network changes, as predicted by an activity‐based model, which also provides arguments for promotion of self‐initiated activities, experiences, and intervention provided closer to the time of injury and during sensitive periods . Alternative pathways after brain injury are typically less efficient, though therapy can help strengthen them and enhance their function.…”

“…Yet, more relevant mechanisms to neurodevelopmental disorders and rehabilitation likely involve strengthening of previously silent, hardly‐used connections (e.g. ipsilateral corticospinal tract spinal projections), through long‐term synaptic potentiation, production of new synapses, fibre sprouting, and myelin changes . Current understanding of neuroplasticity implies that synapses, fibres, and cells are overproduced early in maturation and subsequently compete for survival and efficacy within functional networks.…”

“…ipsilateral corticospinal tract spinal projections), through long-term synaptic potentiation, production of new synapses, fibre sprouting, and myelin changes. 5 Current understanding of neuroplasticity implies that synapses, fibres, and cells are overproduced early in maturation and subsequently compete for survival and efficacy within functional networks. Local (in)activity induces local plasticity and also widespread network changes, as predicted by an activity-based model, which also provides arguments for promotion of self-initiated activities, experiences, and intervention provided closer to the time of injury and during sensitive periods.…”

“…Local (in)activity induces local plasticity and also widespread network changes, as predicted by an activity-based model, which also provides arguments for promotion of self-initiated activities, experiences, and intervention provided closer to the time of injury and during sensitive periods. 1,3,5 Alternative pathways after brain injury are typically less efficient, though therapy can help strengthen them and enhance their function.…”