Modifications of dynamic and static behavior by small-length perturbations in crayfish stretch receptor organs.

To investigate whether static and dynamic sensitivities of slowly and rapidly adapting stretch receptor organs (SAO and RAO, respectively) or crayfish are different when perturbed compared with those in conventional laboratory experiments, receptors were submitted to ramplike length changes of different velocities separated by long-duration, constant lengths of different values. They were perturbed at random by fast, small-amplitude length variations called "jitter." First-order afferent discharges were recorded extracellularly. Quantifications involved the separate estimation of static and dynamic response components. In the SAO, jitter (1) augmented the static sensitivity, (2) decreased the dynamic sensitivity, (3) simplified response profiles by decreasing nonlinearities and increasing transduction fidelity in terms of coding length. In the RAO, jitter (1) changed the behavior from phasic to tonic with length sensitivity, (2) decreased the dynamic sensitivity to values close to those of the unperturbed SAO, (3) increased transduction fidelity for stimulus length and decreased nonlinearities. Perturbation effects suggest that differences between SAO and RAO are more quantitative than qualitative. Moreover, they have general implications and are relevant to other mechanoreceptors at other levels in the CNS.