Activity of motor cortex neurons during backward locomotion

Abstract

Forward walking (FW) and backward walking (BW) are two important forms of locomotion in quadrupeds. Participation of the motor cortex in the control of FW has been intensively studied, whereas cortical activity during BW has never been investigated. The aim of this study was to analyze locomotion-related activity of the motor cortex during BW and compare it with that during FW. For this purpose, we recorded activity of ndividual neurons in the cat during BW and FW. We found that the ischarge frequency in almost all neurons was modulated in the hythm of stepping during both FW and BW. However, the modulation atterns during BW and FW were different in 80% of neurons. To etermine the source of modulating influences (forelimb controllers s. hindlimb controllers), the neurons were recorded not only during uadrupedal locomotion but also during bipedal locomotion (with ither forelimbs or hindlimbs walking), and their modulation patterns ere compared. We found that during BW (like during FW), modulation n some neurons was determined by inputs from limb controllers f only one girdle, whereas the other neurons received inputs from oth girdles. The combinations of inputs could depend on the direction f locomotion. Most often (in 51% of forelimb-related neurons nd in 34% of the hindlimb-related neurons), the neurons received nputs only from their own girdle when this girdle was leading and rom both girdles when this girdle was trailing. This reconfiguration of puts suggests flexibility of the functional roles of individual cortical eurons during different forms of locomotion. © 2011 the American Physiological Society.