Activity-Dependent Plasticity of Spinal Circuits in the Developing and Mature Spinal Cord

Abstract

Part of the development and maturation of the central nervous system (CNS) occurs through interactions with the environment. Through physical activities and interactions with the world, an animal receives considerable sensory information from various sources. These sources can be internally (proprioceptive) or externally (such as touch and pressure) generated senses. Ample evidence exists to demonstrate that the sensory information originating from large diameter afferents (Ia fibers) have an important role in inducing essential functional and morphological changes for the maturation of both the brain and the spinal cord. The Ia fibers transmit sensory information generated by muscle activity and movement. Such use or activity-dependent plastic changes occur throughout life and are one reason for the ability to acquire new skills and learn new movements. However, the extent and particularly the mechanisms of activity-dependent changes are markedly different between a developing nervous system and a mature nervous system. Understanding these mechanisms is an important step to develop strategies for regaining motor function after different injuries to the CNS. Plastic changes induced by activity occur both in the brain and spinal cord. This paper reviews the activity-dependent changes in the spinal cord neural circuits during both the developmental stages of the CNS and in adulthood.

Spinal microcircuits comprising dI3 interneurons are necessary for motor functional recovery following spinal cord transection

“…Such changes have been proposed to underlie spontaneous or training-induced changes in motor output in spinal cord injury patients (Harkema, 2008; Knikou, 2010; Dietz, 2012) and in animal models of spinal cord injury (Côté and Gossard, 2004; Frigon et al, 2009; Tillakaratne et al, 2010; Martin, 2012; van den Brand et al, 2012; Houle and Côté, 2013; Takeoka et al, 2014). Similar mechanisms of plasticity may also occur during learning in intact developing and mature spinal cords (Tahayori and Koceja, 2012; Grau, 2014). Studying such changes at synapses between dI3 INs and their target locomotor circuit neurons may reveal specific mechanisms underlying this plasticity.…”

Functional O-GlcNAc modifications: Implications in molecular regulation and pathophysiology

“…The brain and spinal cord represent the main contributors to CNS function and enable whole system communication through synaptic stimulation (Moore, 1993; Tahayori & Koceja, 2012; Zhang et al , 2003). While only constituting a small portion of an organism’s mass, the CNS requires a significant amount of metabolic fuel, utilizing approximately 50% of the total glucose load (Fehm et al , 2006).…”

Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation

“…After that, the work of Donald Hebb was very important to the concept of long-term potentiation (LTP), namely by suggesting that two neurons that fire together and are close enough may grow some connections or undergo metabolic changes that increase their ability to communicate [8]. This happens because chemical synapses have the ability to change their strength [9].…”

“…Sensory information from Ia afferent fibers (transmitting information about muscle activity and movement) play an essential role in inducing functional and morphological changes that lead to the maturation of the brain and the spinal cord [9], independently of the SCI level and whether it is complete or incomplete [10]. Thus, activity-dependent plasticity refers to the changes in the central nervous system (CNS) associated with movement [9] and reflects one of the basic forms of learning in humans [11]. These neural changes happen throughout the life span at both the brain and spinal cord level.…”