Stretch receptor responses to sinusoidal stimuli depend critically on modulation depth and background length

The correspondence between afferent discharges and sinusoidal length modulations was evaluated by average Lissajous displays of rate vs. length in isolated fast-adapting stretch receptor organs (FAO) of crayfish. Frequency effects were compared using modulation depths and background lengths within physiological ranges. The receptor remained silent with shallow and slow stimuli. With greater depths, more frequencies became effective, discharges occupied more of each cycle, and peak and overall rates increased. At large depths, increases were smaller or were substituted by decreases (overstretch).