Two chronic motor training paradigms differentially influence acute instrumental learning in spinally transected rats

Abstract

The effect of two chronic motor training paradigms on the ability of the lumbar spinal cord to perform an acute instrumental learning task was examined in neonatally (postnatal day 5; P5) spinal cord transected (i.e., spinal) rats. At ∼P30, rats began either unipedal hindlimb stand training (Stand-Tr; 20-25 min/day, 5 days/wk), or bipedal hindlimb step training (Step-Tr; 20 min/day; 5 days/wk) for 7 wks. Non-trained spinal rats (Non-Tr) served as controls. After 7 wks all groups were tested on the flexor-biased instrumental learning paradigm. We hypothesized that 1) Step-Tr rats would exhibit an increased capacity to learn the flexor-biased task relative to Non-Tr subjects, as locomotion involves repetitive training of the tibialis anterior (TA), the ankle flexor whose activation is important for successful instrumental learning, and 2) Stand-Tr rats would exhibit a deficit in acute motor learning, as unipedal training activates the ipsilateral ankle extensors, but not flexors. Results showed no differences in acute learning potential between Non-Tr and Step-Tr rats, while the Stand-Tr group showed a reduced capacity to learn the acute task. Further investigation of the Stand-Tr group showed that, while both the ipsilateral and contralateral hindlimbs were significantly impaired in their acute learning potential, the contralateral, untrained hindlimbs exhibited significantly greater learning deficits. These results suggest that different types of chronic peripheral input may have a significant impact on the ability to learn a novel motor task, and demonstrate the potential for experiencedependent plasticity in the spinal cord in the absence of supraspinal connectivity.

Plasticity After Spinal Cord Injury: Relevance to Recovery and Approaches to Facilitate It

“…Not surprisingly, training in one task does not necessarily translate into improvements in another task [53][54][55][56]. Even more surprising are findings that training in one task can even have detrimental effects on another task.…”

“…Even more surprising are findings that training in one task can even have detrimental effects on another task. For example, cats with complete SCI transections trained to walk on a treadmill had difficulties in standing in contrast to cats trained to stand, which performed worse in walking than untrained cats [53,56]. Likewise, rats with cervical SCI trained in a reaching task showed deficits in crossing a horizontal ladder [45] or increased activity induced by environmental enrichment promoted recovery in untrained tasks, but interfered with the training in reaching tasks [57].…”

Non-assisted treadmill training does not improve motor recovery and body composition in spinal cord-transected mice

“…Earlier reports showed also, using different modes of training, that spinal learning is task dependent. 14,15 Furthermore, some data suggest that the spinal cord itself needs to have reached a significant level of excitability for weight-bearing spinal stepping to be expressed. 16,17 It was also shown that the amount of hindlimb loading (using robotic-controlled weight support assistance) as well as the amount of training (number of steps) significantly alter stepping quality promoted by training.…”

Estratégia terapêutica após contusão da medula espinhal: recuperação funcional e estabilidade cortical sensório-motora

“…O treinamento na esteira é uma forma de atividade física intensamente investigada em estudos experimentais, tanto em humanos (Behrman e Harkema, 2000;Dobkin et al, 2003;Hutchinson et al, 2004;Giangregorio et al, 2005;Dietz, 2009), como em modelos animais (Kunkel-Bagden et al, 1993;De Leon et al, 1998;Edgerton et al, 2001;Ahn et al, 2006;Bigbee et al, 2007;Barriere et al, 2008). Kim et al (2006) afirmam que a recuperação da função motora após uma lesão é mediada por uma reorganização estrutural e funcional do sistema motor residual, que pode ser induzida pelo treinamento motor.…”

“…Como já foi dito no início da introdução, o treinamento na esteira é uma forma de atividade física intensamente investigada em estudos experimentais, tanto em humanos (Behrman e Harkema, 2000;Dobkin et al, 2003;Hutchinson et al, 2004;Giangregorio et al, 2005;Dietz, 2009;Duschau-Wicke et al, 2010), como em modelos animais (Kunkel-Bagden et al, 1993;De Leon et al, 1998;Edgerton et al, 2001;Ahn et al, 2006;Bigbee et al, 2007;Barriere et al, 2008;Heng e De Leon, 2009;Andrade et al, 2010). Já foi demonstrado que tanto em humanos como em ratos lesados medulares, o treinamento na esteira com suporte de peso resulta na melhora da habilidade de andar, e em alguns casos, os padrões de ativação muscular e a cinemática se aproximam daqueles de antes da lesão (Behrman e Harkema, 2000;Nooijen et al, 2009;Heng e De Leon, 2009).…”