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

✍ Scribed by J. P. Segundo; O. Diez Martínez

• Publisher: Springer-Verlag
• Year: 1985
• Tongue: English
• Weight: 896 KB
• Volume: 51
• Category: Article
• ISSN: 0340-1200
• DOI: 10.1007/bf00350777

✦ Synopsis

The correspondence between afferent discharges and sinusoidal length modulations (at 0.2-10 cps) was evaluated by average Lissajous displays of rate vs. length in isolated fast-adapting stretch receptor organs (FAO) of crayfish. Frequency effects (Diez Martinez et al., 1983) were compared using modulation depths and background lengths of, respectively, 1-10% of and 0.3-40% over resting length, well 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). With greater background lengths at 0.2 and 1 cps, individual and peak Lissajous rates increased, as did the overall value; eventually, the fiat extension disappeared. At 0.2 cps, Lissajous plots became ellipses; at 1 cps, loops became counter-clockwise. At 3 and 10 cps, rates augmented only with small increases; beyond, peak rates remained unchanged or dropped. In short, each characteristic of the transduction is apparent only within a domain defined by the stimulus features as well as by the way stimuli and afferent discharges are evaluated. Each domain overlaps partially with others but falls short of that used in nature. For example: the stimulus-response relation was linear with low frequencies, large background lengths and moderate depths when observing average Lissajous plots; saturations were present with the low frequency, shallow modulations without discharges; clockwise loops occurred with particular frequencies, background lengths and depths, but not with others. Hence, any simple and succinct description is only a local rule that holds exclusively within restrictive * Supported by funds from the Brain Research Institute and by a scholarship to ODM from the Departamento de Becas, UNAM constraints. Any generalization beyond this domain constitutes a misleading oversimplication.