Mean Pupil Diameter Research Articles

Mating induces pupillary dilatation in female rats: Role of pelvic nerve

In the present study, we demonstrate that natural or artificial vaginal stimulation exerts a powerful effect on autonomic activity, as measured by pupillary diameter. Pupillary diameter was recorded approximately 3–5 sec after copulatory mounts, intromissions, ejaculations or experimenter delivered stimulation. The pupil was magnified 43× and its diameter was measured directly from a calibrated video screen. Mating tests were performed on 13 female rats which received at least one complete ejaculatory series. Compared to the premount (baseline) value (1.01 mm), mean pupillary diameters were significantly greater during (a) mounts without intromissions (1.20 mm; 20% increase), (b) mounts with intromissions (1.34 mm; 33% increase), or (c) ejaculation (1.49 mm; 48% increase. Mean pupillary diameter during the post-ejaculatory interval (0.95 mm; 6% decrease) did not differ significantly from the premount baseline. Since the mean pupillary diameter at the last intromission before ejaculation was significantly larger (by 18%) than the diameter at the first intromission, repeated intromissions may generate a gradually increasing net sympathetic response reaching a peak at ejaculation. In order to identify the adequate stimuli for increasing pupillary diameter, we applied external genital stimulation (flank-perineal palpation), internal genital stimulation (probing the vaginal cervix with a glass rod), or both combined. Vaginal stimulation alone produced near-maximal pupillary dilatation; external genital stimulation was less effective, and combined internal and external genital stimulation was more effective. Thus, vaginal afferent activity is an adequate stimulus to produce pupillary dilatation. Furthermore, bilateral pelvic neurectomy markedly attenuated the effect of vaginal stimulation on dilating the pupil. Since pupillary diameter is at least partly a function of autonomic tone, this “bioassay” indicates that genital stimulation may produce a net sympathetic activating effect.

Patterns of daytime sleepiness in narcoleptics and normals: A pupillometric study

Pupil diameter was measured in light and dark conditions every half hour for 6.5–10 h in 3 normal controls and 3 narcoleptics. Mean pupillary diameter was significantly smaller in the narcoleptic group than in the normal group. Pupil activity was correlated with pupil diameter only in the dark condition in narcoleptics. Pupil diameter varied with a circa 90 min periodicity in the narcoleptics but not in the normal controls. These results indicate firstly, that one-time assessment of pupil size is insufficient; and secondly, that the appearance of these rhythms may be the result of a defect in arousal mechanisms of narcoleptics which usually play an inhibitory role.

A model for nonlinear stochastic behavior of the pupil.

In this paper we present new experimental results that show pupillary noise to be multiplicative in a particular fashion with greatest variance in midrange and smaller variance at high and low ranges. This confirms the finding of multiplicative noise by Stanten and Stark (1966), but modifies and extends the relationship they suggested between standard deviation and mean pupil diameter. We propose a parametric model of the iris muscle which not only describes the static characteristics of pupil response to given stimuli, but also explains its random fluctuations in terms of probability density functions. We emphasize the point that the range nonlinearity is not due to decreased gain at the extrema of the pupil range, but is operational over a wide portion of the pupillary behavioral range, hence its name--"expansive range nonlinearity". We conclude that noise amplitude, which is a function of the pupil diameter, closely parallels the changes in deterministic gain. Thus pupil noise can be simply considered as cross-talk additive Gaussian noise injected into the pupil system at midbrain level.

Pupillographic Assessment of Sexual Interest and Sexual Arousal

Hess (1972) suggested that subjectively attractive stimuli produce dilation of the pupil while subjectively unpleasant stimuli gave constriction. He extended this 'attractiondilation,' 'aversion+onstriction' hypothesis to sexual stimuli. Atwood and Howell ( 197 1 ) reported that pupillary responses of paedophiliacs to pictures of adult females were primarily contraction while other types of offenders mainly showed dilation. Bernick, et al. (197 1 ) found good agreement between degree of sexual arousal (assessed by verbal reports) and pupil size to various sexual films. Unfortunately direct measures of sexual arousal appear not to have been used in pupillometric studies. In contradiction to Hess's viewpoint, Janisse (1973) demonstrated that aversive as well as attractive material can produce pupillary dilation. The research reported in this paper attempts to compare the hypotheses of Hess and Janisse, using sexual stimuli. Thirreen male hererosexuals were tested. These were security hospital patients detained for sexual deviance. Subjects controlled the delivery of monochrome slides of (a) semi-nude men, (b) semi-nude women, and (c) neutral scenes (country-side). Mean volunrary viewing times were taken as the measure of sexual interest. On a separate testing period, and using the same set of slides, mean pupil diameter (relative to neutrals) was measured by an infra-red video technique. Sexual aroussl was scored as an index of increase in diameter of the penis during the viewing of heterosexual and homosexual films. Except for penile plethysmography, subjects were unaware of the measures being taken. The hypothesis that degree of sexual interest is related to increase in pupil diameter was confirmed with slides of adult females (s = 0.56, p < 0.05) but for slides of men. r was -0.34: a significant shift in direction p < 0.05. The measure of sexual arousal to heterosexual films gave a non-significant correlation with pupil diameter to pictures of females (T = 0.41), but again the correlation between increases in penis diameter to homosexual films and pupil diameter to slides of men was negative (+ = -4.32). a significant switch in direction p < 0.10. In summary, the Janisse hypothesis is upheld: both attractive and aversive st~muli can produce pupillary dilation. However, ongoing work in this laboratory suggests that sexual material produces much greater pupillary dilation effects than aversive or horror stimuli.