2005; Clarac and Pearlstein 2007; Harris-Warrick 2010). The rhythmic output of a CPG originates either from emergent network properties deriving from mutual synaptic coupling between interneurons (e.g., locomotory rhythms, Satterlie 1985), endogenous bursting properties of individual pacemaker cells (e.g., respiration in mammals, Paton et al. Inhibitors,research,lifescience,medical 2006), or as a combination of both mechanisms (e.g., leech heart, Cymbalyuk et al. 2002). Even though all CPG circuits can endogenously produce rhythmic motor patterns without sensory feedback or other rhythmic inputs, most CPGs are nevertheless extensively modulated by sensory feedback (Pearson 1995; Beenhakker et al. 2005; Büschges and Gruhn 2008) and neuromodulators

(Dickinson 2006; Harris-Warrick 2011) to allow flexible adjustment to varying external conditions

(Pearson 2000). Besides locomotion, intraspecific Inhibitors,research,lifescience,medical communication with stereotypically repeated visual, vibratory, or acoustic signals is also based on centrally generated rhythmic motor activity. Crickets are a well-established model system for studying principles of species-specific Inhibitors,research,lifescience,medical acoustic communication (e.g., Huber 1962; Hoy and Paul 1973; Schildberger 1994; IKK Inhibitor VII supplier Poulet and Hedwig 2006; Schöneich and Hedwig 2010; Grace and Shaw 2011). The males produce a genetically fixed calling song pattern (Bentley and Hoy 1972) that has to match the sharply tuned auditory recognition mechanism of the conspecific females (Pollack and Hoy 1979; Weber and Thorson 1989). However, the neuronal network that generates the singing motor pattern is still a virtually

uncharted area (reviews: Kutsch and Huber 1989; Elsner 1994; Gerhardt and Huber 2002). From his pioneering studies, Huber (1955, 1960) initially Inhibitors,research,lifescience,medical concluded that the singing pattern is generated in distinct neuropiles of the cricket brain. Following experiments, however, demonstrated that the head ganglia are not directly involved Inhibitors,research,lifescience,medical in the central pattern generation of the crickets calling song (Otto 1971; Kutsch and Otto 1972). A pair of descending brain neurons merely controls the singing behavior by serving as command neurons that Molecular Cell activate the singing CPG with their tonic spike discharge (Hedwig 2000). As the mesothoracic ganglion houses the motoneurons, which are driving the sonorous wing movements, for some decades it was surmised that the singing CPG is also located in this ganglion (review: Kutsch and Huber 1989). Recent studies, however, demonstrated that the neural network that generates the singing motor pattern spans from the metathoracic (Hennig and Otto 1995) to the first unfused abdominal ganglion (Schöneich and Hedwig 2011), and preliminary experiments reported an ascending singing interneuron in the first unfused abdominal ganglion, which elicited and reset the singing motor pattern when stimulated with intracellular current injection (Schöneich and Hedwig 2011).