“…Rhythm-generating networks are likely present in early vertebrates, but studies in non-mammalian vertebrates are rather limited. A single microcircuit located in a region rostrolateral to the trigeminal motor nucleus is present in the lamprey (Rovainen, 1983(Rovainen, , 1985Russell, 1986;Thompson, 1985;Bongianni et al, 1999Bongianni et al, , 2002Bongianni et al, , 2006Martel et al, 2007a;Mutolo et al, 2007Mutolo et al, , 2010Mutolo et al, , 2011Cinelli et al, 2013Cinelli et al, , 2014Cinelli et al, , 2016Cinelli et al, , 2017Cinelli et al, , 2020b; for review see Bongianni et al, 2016;Milsom, 2018), a jawless fish that diverged from the main vertebrate line about 560 million years ago (Kumar and Hedges, 1998). This neural aggregate, termed the paratrigeminal respiratory group (pTRG), is necessary and sufficient for rhythm generation driving gill movements that can be recorded primarily from the vagus nerve (for review see Bongianni et al, 2016).…”