Post activity effects in mechanoreceptor afferents of the cockroach

Abstract

1. Giant interneurons of the cockroachPeriplaneta americana show reduced responsiveness, for up to 800 ms, following activation by sound via their cereal inputs. The reduction in responsiveness is evident when tested either by a sound test stimulus, or by electrical stimulation of the cereal nerve. 2. Afferent axons of cereal filiform hair sensilla exhibit a reduced responsiveness during and immediately following activation by sound. 3. Use of oscillatory sound stimuli, rather than continuous deflections of the filiform hairs, circumvents the possibility that slow mechanical restitution of receptor elements after deflection is the cause of the post activity reduced responsiveness. 4. The magnitude of reduction in responsiveness of cereal afferents closely parallels their post activity afterpotential. 5. Amplitude and duration of the afterpotential were found to increase with stimulus intensity and to have the largest values at a stimulus frequency of 250 Hz and 300 ms duration. 6. The afterpotential curve was found to fit the equationV t= V(1-e −t/τ) τ=60 ms, at stimulus frequency of 100 Hz. 7. It is predicted that the reduced responsiveness of cereal afferents following activity will increase the threshold for escape immediately after a running bout.