About this Research Topic
The spinal cord is a complex structure devoted to the analysis and integration of sensory information with descending commands to organize and execute motor
patterns and autonomic functions. We are just beginning to understand the mechanisms by which spinal neural networks accomplish these various functions in different environmental contexts. Since the pioneer work by Sherrington and Eccles - that provided the foundations of our knowledge on elementary circuitry and cellular properties- the spinal cord of mammals has been a fundamental model system for our current understanding of the structure, function and plasticity of the spinal cord. However, as realized by Cajal, the study of the spinal cord in lower vertebrates could give valuable information about structural and functional adaptations to particular body plans or behaviours, providing hints about universal mechanisms of spinal circuits.
The unique advantages provided by some lower vertebrates, such as tissue transparency and the facility for genetic manipulations of zebrafish, have made them useful models to study the development of spinal circuits underlying locomotor behaviour. Several studies in tadpoles have revealed fundamental information about how neuronal activity during spinal cord development shapes the assembly of circuits to assure functional stability. Work done in other low vertebrates such as lampreys, Amphibia (e.g., salamanders, frogs) and some reptiles contributed fundamental insights on the synaptic and cellular functional principles of spinal cord circuits. The use of integrated preparations amenable in some low vertebrates models have allowed to bridge the gap between the dynamics at the cellular level with stereotyped locomotor behaviours, an approach difficult to achieve in mammals and usually reserved for simple neural circuits in invertebrates.
Unlike the mammalian spinal cord, some low vertebrates have the remarkable ability for self-repair after injury. For example, in lamprey, salamanders and some fish spinal cord injury is followed by endogenous regeneration with anatomical and functional restoration. Although turtles –which like mammals are amniotes- are not able of the same kind of regeneration, they react to injury with a more adaptive response. These animals reconnect the transected cord by forming a bridge of tissue that supports the navigation of regenerating axons leading to substantial locomotor recovery. Thus, low vertebrates represent ideal models to study regeneration after traumatic injury providing useful clues about strategies that may be followed to restore function in mammalian species. A transcriptomic study suggests that spinal reconnection in anamniotes is different from those in turtles, which seem use a genetic toolkit that is also available in mammals and other amniotes.
The aim of this Research Topic is to gather seminal work done in low vertebrate models that has and is contributing to our understanding of the function and plasticity of the spinal cord.
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.