Title

Random-Sequence Stimulation of the G1 Hair Afferent Unit

Document Type

Article

Publication Date

1990

Catalog Record

Catalog Record

Abstract

Impulse trains were recorded from the parent axon of the cat G1 hair afferent unit. Separate random (Poisson-like) trains of mechanical stimuli were applied to two coinnervated receptive field hairs individually or concurrently. The objective was to determine whether the parent axonal impulse train elicited by dual-hair stimulation was due to a temporal combining (“mixing”; Fukami, 1980) of the impulse trains elicited in the parent axon by the same stimulation to each hair alone. Both impulse rates and patterns were assessed. During single-hair random stimulation, impulse trains differed from stimulus trains, having lower mean rates and short-interval doublets. During dual-hair random stimulation, mean impulse frequencies were on average 36% less than those predicted for mixing. There were no correlations between stimulus amplitude and departures from mixing. As a further test of the mixing hypothesis, the two single-hair-elicited impulse trains were temporally merged (i.e., superimposed to form one impulse train). Such merged impulse trains were compared with the corresponding dual-hair-elicited impulse train. Dual-hair-elicited frequencies were typically less than those of the merged trains, despite the use of an absolute-refractory-period criterion during merging. The impulse patterns elicited by dual-hair stimulation usually differed from the merged-train patterns. Temporal coupling between stimuli and impulses was either variable or absent during single-hair random stimulation; such coupling was altered during dual-hair random stimulation. In summary, this work showed that the dual-hair responses could not be predicted from the single-hair responses. Limitations of the mixing hypothesis and possible biophysical mechanisms in the axonal arborization are discussed. The results are consistent with a general hypothesis of analog processing within the arborization of the parent axon.

DOI

10.3109/08990229009144696

Catalog Record

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