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. 2015 May 29;593(Pt 11):2403–2426. doi: 10.1113/JP270121

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© 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society

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Intact systems: maintenance of left–right alternation at any locomotor frequency

A and B, results of simulations using Model and Model 2, respectively. Left column in both panels shows two examples of activity (integrated histograms) of all four RG centres of the models that correspond to two (one low and one high) oscillation frequencies. The right column in each panel exhibits the phase differences between the activity of: (left) flexor (l-RG-F) and (left) extensor (l-RG-E) centres (top), left (l-RG-F) and right (r-RG-F) flexor centres (middle), and left (l-RG-E) and right (r-RG-E) extensor centres (bottom) as a function of oscillation frequency. Each black square (n = 50) represents a separate simulation. In each simulation, α was randomly chosen from a range of α ([0, 0.12] for Model 1 and [0, 0.1] for Model 2) and model parameters and initial conditions were randomly redistributed. C, experimental results from wild-type mice from studies by Talpalar et al. (2013) presented in the same style (previously unpublished data). The left column shows two examples of raw recordings (black) from four lumbar ventral roots (flexor rL2 and lL2, and extensor rL5 and lL5) superimposed with the rectified and integrated (yellow) traces, that exhibit oscillations at two (one low and one high) locomotor frequencies. The right column shows flexor–extensor (top), lL2-rL2 flexor (middle) and lL5-rL5 extensor (bottom) phase differences for each preparation/episode (black squares) plotted against locomotor frequency. Error bars show angular dispersion. The vertical dashed lines separate the lower, medium and higher frequencies. Note that in both intact models (A and B) and in experimental studies on wild-type mice (C), the black squares representing left–right flexor and left–right extensor phase differences are concentrated around 0.5 indicating left–right alternating activity over the whole range of frequencies. In this and following figures, the blue bars highlight left–right alternating activity. -E, extensor; -F, flexor; l, left; r, right; RG, rhythm generator.

Inline graphic — Intact systems: maintenance of left–right alternation at any locomotor frequency

A and B, results of simulations using Model and Model 2, respectively. Left column in both panels shows two examples of activity (integrated histograms) of all four RG centres of the models that correspond to two (one low and one high) oscillation frequencies. The right column in each panel exhibits the phase differences between the activity of: (left) flexor (l-RG-F) and (left) extensor (l-RG-E) centres (top), left (l-RG-F) and right (r-RG-F) flexor centres (middle), and left (l-RG-E) and right (r-RG-E) extensor centres (bottom) as a function of oscillation frequency. Each black square (n = 50) represents a separate simulation. In each simulation, α was randomly chosen from a range of α ([0, 0.12] for Model 1 and [0, 0.1] for Model 2) and model parameters and initial conditions were randomly redistributed. C, experimental results from wild-type mice from studies by Talpalar et al. (2013) presented in the same style (previously unpublished data). The left column shows two examples of raw recordings (black) from four lumbar ventral roots (flexor rL2 and lL2, and extensor rL5 and lL5) superimposed with the rectified and integrated (yellow) traces, that exhibit oscillations at two (one low and one high) locomotor frequencies. The right column shows flexor–extensor (top), lL2-rL2 flexor (middle) and lL5-rL5 extensor (bottom) phase differences for each preparation/episode (black squares) plotted against locomotor frequency. Error bars show angular dispersion. The vertical dashed lines separate the lower, medium and higher frequencies. Note that in both intact models (A and B) and in experimental studies on wild-type mice (C), the black squares representing left–right flexor and left–right extensor phase differences are concentrated around 0.5 indicating left–right alternating activity over the whole range of frequencies. In this and following figures, the blue bars highlight left–right alternating activity. -E, extensor; -F, flexor; l, left; r, right; RG, rhythm generator.