1. The supraspinal control of locomotion - Cutaneous mechanosensory-evoked locomotion

This aspect of the research in the lab is aimed at gaining a better understanding of the cellular mechanisms underlying the supraspinal control of locomotion in vertebrates. We examine how sensory inputs initiate locomotor activity in a lower vertebrate, the lamprey. We also seek to identify the role of different regions of the central nervous system involved in the control and initiation of locomotion. Supraspinal locomotor regions play a key role in goal-directed locomotion where internal cues provide the triggering signal of locomotion. We also examine the mechanisms by which locomotion is initiated and controlled by external sensory inputs as well as by internal cues related to basic biological functions such as feeding, exploration, and reproduction. Because the general anatomical and physiological organization of the central nervous system is highly conserved between different species of vertebrates, information gained in lampreys will provide useful knowledge applicable to other vertebrates, including humans.

Cutaneous mechanosensory-evoked locomotion

In lower vertebrates such as lampreys, sensory inputs play a significant role in triggering locomotor bouts. For instance, cutaneous inputs can elicit locomotion allowing the animal to move away from a stimulus. This is referred to as escape locomotion or escape swimming. We have identified the neural circuitry (pathways and neurotransmitters) and some of the cellular mechanisms involved in escape locomotion triggered by sensory input. We have shown that the transformation of a sensory input into a motor command relies largely on the intrinsic properties of the reticulospinal neurons, which are targets of these sensory inputs. Escape locomotion results from a persisting activation of reticulospinal neurons.

The sensory inputs that are important for initiating and controlling locomotor behavior are strongly modulated by the central networks responsible for locomotion. We have described a cholinergic muscarinic modulation of sensory inputs to reticulospinal neurons that appears to originate from the cholinergic cells contained in the mesencephalic locomotor region, or MLR. Other neuromodulators such as serotonin also gate the transmission from sensory inputs to reticulospinal cells by acting both directly on the sensory transmission and on the reticulospinal cells themselves.

This research is supported by the Canadian Institutes of Health Research.