Comment on van den Brand et al (2012): voluntary control, yes; of locomotion, probably not

Using rats trained and tested in an upright posture, Gregoire Courtine and colleagues claim voluntary control of locomotion is restored after paralyzing spinal cord injury. In our polemical article we propose that the cortical and brainstem plasticity they report produces voluntary postural adjustments that enhance potent afferent feedback associated with upright bipedal locomotion, rather than voluntary control over lumbosacral locomotor circuitry. They have not considered recent findings (Sławińska et al., Journal of Physiology, 2012) that their upright posture paradigm contributes to locomotor capability after spinal cord injuries and that the upright bipedal posture alone provides sensory feedback from load receptors of the hindlimbs that potently facilitates locomotor activity of hindlimbs in the absence of training, drug application, or supraspinal influence. We propose that postural adjustments that move a centre of mass forward activate the locomotor CPG in the upright posture, rather than direct voluntary control of locomotion, account for their results (van den Brand et al., Science 2012).

30 October 2012