Table 1.

Discharge patterns of phrenic afferent neurons

Group	Species	Comments	References
Ia	Cat, rat	Ia fibers discharge primarily in phase with muscle lengthening (i.e., expiration/diaphragm relaxation); activity increases during DIA fatigue	Bałkowiec et al. (1995); Barstad et al. (1965); Corda et al. (1965); Hill (2001); Holt et al. (1991)
Ib	Cat, rat	Ib fibers discharge in phase with inspiration; activity increases with respiratory effort; activity may decrease during fatigue	Bałkowiec et al. (1995); Balzamo et al. (1992); Corda et al. (1965); Duron and Caillol (1973); Holt et al. (1991); Jammes and Balzamo (1992); Jammes et al. (1986)
III–IV	Cat, rat	III–IV afferents discharge with irregular patterns during eupnea; afferents are activated during ischemia and lactic acid infusion; DIA fatigue increases discharge of group IV but not III	Bałkowiec et al. (1995); Graham et al. (1986); Hill (2000); Jammes and Balzamo (1992); Jammes et al. (1986); Revelette et al. (1988); Teitelbaum et al. (1993a)

Listed are key publications providing descriptions of the discharge patterns of phrenic afferents. DIA, diaphragm.