![]() ![]() We emphasize that PD changes triggered by the deviants reflect a change in the internal state of the subject, and are unrelated to visual processing. One such example is the auditory ‘oddball’ paradigm, where the subject is habituated to a standard, predictable stimulus pattern, and is ‘surprised’ by infrequent deviant stimuli 23, 24, 26, 29. This could be accomplished by providing an occasional unexpected stimulus 7, 18, 23, 24, a salient or familiar stimulus 25, or by abruptly changing the statistical distribution of stimuli 23, 26– 29. PD changes can also be evoked exogenously by providing stimuli that capture the subject’s attention in a bottom-up fashion. Pupillometry can thus be used as a window into spontaneously fluctuating neuromodulatory tone across waking and sleep states 20, 21, providing a non-invasive metric to evaluate animal models of neuromodulatory defects in clinical populations 22. In animal models, PD is similarly modulated by listening effort and other top-down factors, and PD strongly correlates with cortical activity states 14– 18, and has been shown to closely track noradrenergic and cholinergic tone at fast and slow timescales respectively 19. These PD changes can be attributed to endogenous mechanisms, i.e., when the subject regulates their arousal or attention to achieve better task performance 5, 10. ![]() Increased effort from the subject is necessary, for example, when searching for visual targets 8, 9, or listening for meaningful sounds in cluttered, ambiguous, or noisy acoustic conditions 10– 13. With task engagement, the pupil dilates with increasing arousal or increasing mental effort 4– 7. In relaxed human subjects, the pupil diameter (PD) exhibits sustained low-frequency oscillations 1 mainly resulting from modulation of parasympathetic neural activity 2, 3. These results lay the foundation for using pupillometry as a reliable method of estimating thresholds in large experimental cohorts, and unveil the full potential of using pupillometry to explore broad similarities between humans and animal models.Įven in the absence of luminance changes, pupil size fluctuates in response to many endogenous and exogenous factors. ![]() We demonstrate that pupillometry yields reliable detection and discrimination thresholds across a range of simple (tones) and complex (conspecific vocalizations) stimuli that pupil responses can be robustly evoked using different stimulus contingencies (low-level acoustic changes, or higher level categorical changes) and that pupil responses are modulated by short-term training. In this study, we used an auditory oddball paradigm to estimate detection and discrimination thresholds across a wide range of stimuli in guinea pigs. Using pupillometry, previous studies in animal models have obtained threshold estimates to simple stimuli such as pure tones, but have not explored whether similar pupil responses can be evoked by complex stimuli, what other stimulus contingencies might affect stimulus-evoked pupil responses, and if pupil responses can be modulated by experience or short-term training. Pupillometry shows great promise as a non-invasive, easily-deployable method of comparing human and animal thresholds. Estimates of detection and discrimination thresholds are often used to explore broad perceptual similarities between human subjects and animal models. ![]()
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