Central Nervous System: Structure versus Injury and Regeneration versus Recovery

Abstract

Since classical times, the structural complexity of the mammalian central nervous system (CNS) has often been claimed to be one of the main obstacles for achieving adequate or clinically useful functional recovery after damage. The reconstruction of a CNS injured region will be aborted by failure in the reorganization of one or another of its multiple fiber-neuronal pathways and hence a complete functional recovery is unattainable. In other words, the CNS of high order animals has lost its regenerating ability, an ability otherwise retained by their peripheral nervous system. However, in recent years, the rigidity of this conception has been softened by an increasing awareness of the extraordinary plasticity of the CNS.^1–3 Recent observations indicate that some degree of rearrangement and/or remodeling at both structural and functional levels does occur normally in the CNS, particularly during late prenatal and early postnatal developments.⁴ Furthermore, the process of learning new tasks implies a CNS capacity to rearrange and/or to modify its basic circuitries in response to environmental influences.⁵ Therefore, CNS neurons and fibers seem to be able to rearrange the distribution of their different synaptic arrays and thereby to modify their functional activity and spatial interrelationships.