“…Another theory explaining speed-dependent changes in coordination stratifies ‘rhythm’ and ‘pattern’ control (Perret and Cabelguen, 1980; Koshland and Smith, 1989; Kriellaars et al, 1994; Burke et al, 2001; Lafreniere-Roula and McCrea, 2005), where populations of interneurons generating higher or lower frequency rhythms feed into separate populations coordinating distinct patterns of motor output (McCrea and Rybak, 2008; Ausborn et al, 2019). In support, studies in zebrafish and mice suggest separate spinal populations are active at different locomotor speeds with distinct patterns of motor output (McLean et al, 2008; Talpalar et al, 2013; Satou et al, 2020; Picton et al, 2022). Critically, however, rhythmogenesis is presumed to originate from a common mechanism regardless of speed, reliant on cellular properties or synaptic drive or both (Guertin, 2009; Brocard et al, 2010; Ryczko et al, 2010; Ziskind-Conhaim and Hochman, 2017; El Manira, 2023).…”