Different Time Courses of Bovine Iris Sphincter and Dilator Muscles after Stimulation

Abstract

Responses of the bovine iris sphincter and dilator muscles evoked either by single electrical stimulation (1–50 ms) or repetitive pulses (0.1–1 ms for 0.1–0.7 s) were isometrically recorded in vitro. In response to electrical nerve stimulation, the bovine iris sphincter exhibited cholinergic contraction followed by slow relaxation, while the dilator predominantly showed cholinergic relaxation. In order to compare the time courses of the iris sphincter and the dilator, the two muscle strips were investigated under the same conditions. Regardless of the conditions of electrical stimulation and incubation time, significant differences were found between the iris sphincter and the dilator in their response time courses.

A unified model of the task-evoked pupil response

“…A popular heuristic analysis in systems neuroscience involves computing the correlation (or regression) between the time course of pupil size and neural activity in some population of interest, where pupil size is treated as a measurement of arousal level ( 14 , 15 ). The implicit assumption is that the neural input to the pupil tracks with arousal level and that delays and temporal summation caused by the sluggish response of the iris muscles ( 48 , 49 ) do not substantially obscure the underlying correlation between the neural signals. Another popular heuristic approach estimates arousal level based on the height of the pupil response (i.e., max or max-min size) ( 50 ).…”

A unified model of the task-evoked pupil response

“…A popular heuristic analysis in systems neuroscience involves computing the correlation (or regression) between the time course of pupil size and neural activity in some population of interest, where pupil size is treated as a measurement of arousal level [32, 29]. The implicit assumption is that the neural input to the pupil tracks with arousal level and that delays and temporal summation caused by the sluggish response of the iris muscles [84, 85] don’t substantially obscure the underlying correlation between the neural signals. Another popular heuristic approach estimates arousal level based on the height of the pupil response (i.e., max or max-min size) [86, 33].…”