Commentary on “Homeostasis of exercise hyperpnea and optimal sensorimotor integration: The internal model paradigm” by Poon et al

In this paper Poon et al. (2007) summarize their innovative oncepts of the regulation of breathing during exercise and when O2 is inhaled, review the evidence that supports their ideas, nd elaborate on their concept of an internal model. They proose that breathing is optimally controlled, minimizing both the eviation of PCO2 from a desired level and the work of the resiratory muscles required to maintain PCO2 at that level, and hat it does this through the use of an internal model. Internal odels are neural mechanisms of two types that are used in oth biological and man-made control systems (Kawato, 1999; ursztyn et al., 2006). Forward internal models predict sensory ffects from efference copies of motor commands while inverse nternal models predict the motor command that will produce given effect such as the trajectory of movement of an arm. nternal models are faster than are feedback controls and can e used at higher gains without producing instability. Internal odels can be imbedded in feedback control systems (Kawato, 999). The hypothesis offered by Poon et al. (2007) accounts for diferences in the changes in PaCO2 when CO2 is breathed and when O2 is metabolically produced during exercise, but should also xplain the effects of lung disease on arterial PCO2 . The internal odel obviates the need for an explicit work signal. There is onsiderable evidence that internal models are involved in the otor control of limb and eye movements, and in the vestibuar system to help maintain balance (Morasso and Schieppati, 999; Scarchilli and Vercher, 1999; Snyder, 1999). Poon et al. 2007) are the first to apply this concept to the control of breathng.