Some voluntary C-bends may be Mauthner neuron initiated.

Predatory fish sometimes capture a prey fish first by striking it from the side, allowing the predator to consume the stunned prey head first. The rapid body flexion that the predator uses to stun its prey is similar to the "C" shaped maneuver ("C-bend") that many fish species use when performing a C-start escape response. For most species, one of the two Mauthner neurons initiates the C-start and, together with other reticulospinal neurons, their activity determines the extent of the bend and the ultimate trajectory of the fish. Reported here is initial evidence of previously undescribed behaviors where goldfish strike an object while executing voluntary C-bends that are similar to their C-start escape responses. The overlapping distributions of turn durations, turn angles, and angular velocities suggest that at least some voluntary C-bends are initiated by the Mauthner neuron. This implies that the Mauthner neuron can be activated voluntarily in the absence of predator- or feeding-associated releasing stimuli.