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[Cover Caption] Other Issues:	Contents: Volume 86, Issue 1; January, 2006. [Index by Author]  Articles
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Cover: During locomotion, a stimulation (stim) of skin afferents of the dorsum of the foot gives rise to a variety of reflex responses that are appropriate for each phase of the locomotor cycle and result from dynamic interactions between reflex pathways and the central locomotor program. This is illustrated by responses recorded in a flexor muscle (Br for brachialis in red) and an elbow extensor/shoulder retractor muscle (Tri for the long head of triceps brachii in blue). The red panels indicate responses in Br, whereas the blue panels illustrate responses in Tri. Stimulation of the superficial radial cutaneous nerve during swing (red panel, top left) evokes an excitatory response in the elbow flexor muscle Br seen as an increase in the electromyogram (EMG) of the locomotor burst. The raster displayed in that panel shows 10 consecutive short-latency excitatory responses (note time base) followed by inhibition. During stance (red panel, bottom left), the same stimulus does not evoke responses in Br. During swing, the same stimulation gives rise to an excitatory response in Tri that is silent during that phase of the locomotor cycle (blue panel, top right). Again, the raster display shows a consistent short-latency excitatory response in Tri. Conversely, during stance (blue panel, bottom left), the response in Tri is inhibitory despite the fact that Tri is active at that phase of the locomotor cycle. The overall result is that, during swing, the cocontraction of elbow flexor and extensor muscles lock the joint while the whole limb is protracted away from an impeding obstacle. During stance, not only is the limb not flexed, which would be disruptive, but the supporting extensor muscle is inhibited to reduce the risk of potential damage. The scheme of the spinal cord above illustrates how the cutaneous afferent inputs can reach Br and Tri motoneurons through different pathways relayed through the central pattern generator (CPG) or interneurons (In) that can be selected either at the spinal level or through the influence of supraspinal structures. The localization of generic neurons and CPG within the spinal cord is not meant to be anatomically exact. The muscle recordings are taken from Reference 147 of the corresponding article in this issue. Thanks to Daniel Cyr and Claude Gauthier for some of the original artwork. See Rossignol, Serge, Re Cover: During locomotion, a stimulation (stim) of skin afferents of the dorsum of the foot gives rise to a variety of reflex responses that are appropriate for each phase of the locomotor cycle and result from dynamic interactions between reflex pathways and the central locomotor program. This is illustrated by responses recorded in a flexor muscle (Br for brachialis in red) and an elbow extensor/shoulder retractor muscle (Tri for the long head of triceps brachii in blue). The red panels indicate responses in Br, whereas the blue panels illustrate responses in Tri. Stimulation of the superficial radial cutaneous nerve during swing (red panel, top left) evokes an excitatory response in the elbow flexor muscle Br seen as an increase in the electromyogram (EMG) of the locomotor burst. The raster displayed in that panel shows 10 consecutive short-latency excitatory responses (note time base) followed by inhibition. During stance (red panel, bottom left), the same stimulus does not evoke responses in Br. During swing, the same stimulation gives rise to an excitatory response in Tri that is silent during that phase of the locomotor cycle (blue panel, top right). Again, the raster display shows a consistent short-latency excitatory response in Tri. Conversely, during stance (blue panel, bottom left), the response in Tri is inhibitory despite the fact that Tri is active at that phase of the locomotor cycle. The overall result is that, during swing, the cocontraction of elbow flexor and extensor muscles lock the joint while the whole limb is protracted away from an impeding obstacle. During stance, not only is the limb not flexed, which would be disruptive, but the supporting extensor muscle is inhibited to reduce the risk of potential damage. The scheme of the spinal cord above illustrates how the cutaneous afferent inputs can reach Br and Tri motoneurons through different pathways relayed through the central pattern generator (CPG) or interneurons (In) that can be selected either at the spinal level or through the influence of supraspinal structures. The localization of generic neurons and CPG within the spinal cord is not meant to be anatomically exact. The muscle recordings are taken from Reference 147 of the corresponding article in this issue. Thanks to Daniel Cyr and Claude Gauthier for some of the original artwork. See Rossignol, Serge, Rejean Dubuc, and Jean-Pierre Gossard. Physiol Rev 86: 89–154,2006.