A model representing brainstem neurons, five segments of the central pattern generator, and their interconnections was developed. The effect of brief pulse perturbations of different strengths on the intersegmental coupling were examined under two conditions: animal brain attached and disconnected. Coupling was defined as the number of cycles required for phase lags to become stable after a perturbation. A graded response to perturbations, strongly reduced after-effects and quicker return-to-stable swimming behavior were observed with the brain attached. In the intact animal, such increased sensitivity to perturbations and stronger intersegmental coupling may provide greater flexibility and adaptability.
