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Intrasaccadic perception triggers pupillary constriction.

ABSTRACT: It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye's pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward motion for vertical gratings; upward and downward motion for horizontal gratings. When participants made a saccade perpendicular to the gratings' orientation (e.g., a leftward saccade for a vertical grating), the eye's peak velocity matched the gratings' motion. As a result, the retinal image was approximately stable for a brief moment during the saccade, and this gave rise to an intrasaccadic percept: A normally invisible stimulus became visible when eye velocity was maximal. Our results confirm and extend previous studies by demonstrating intrasaccadic perception using a reflexive measure (pupillometry) that does not rely on subjective report. Our results further show that intrasaccadic perception affects all stages of visual processing, from the pupillary response to visual awareness.

SUBMITTER: Mathot S

PROVIDER: S-EPMC4558071 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Intrasaccadic perception triggers pupillary constriction.

Mathôt Sebastiaan S Melmi Jean-Baptiste JB Castet Eric E

PeerJ 20150804

It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye's pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward m ...[more]

PMID: 26339536

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Project description:Eyeblink conditioning is the most popular paradigm for studying classical conditioning in humans. But the fact that eyelids are under voluntary control means it is ultimately impossible to ascertain whether a blink response is 'conditioned' or a timed 'voluntary' blink response. In contrast, the pupillary response is an autonomic response, not under voluntary control. By conditioning the pupillary response, one might avoid potential volition-related confounds. Several attempts have been made to condition the pupillary constriction and dilation responses, with the earliest published attempts dating back to the beginning of the 20th century. While a few early studies reported successful conditioning of pupillary constriction, later studies have failed to replicate this. The apparatus for recording pupil size, the type of stimuli used and the interval between the stimuli has varied in previous attempts-which may explain the inconsistent results. Moreover, measuring the pupil size used to be cumbersome compared with today when an eyetracker can continuously measure pupil size non-invasively. Here we used an eyetracker to test whether it is possible to condition the autonomic pupillary constriction response by pairing a tone (CS) and a light (US) with a 1s CS-US interval. Unlike in previous studies, our subjects went through multiple training sessions to ensure that any potential lack of conditioning would not be due to too little training. A total of 10 participants went through 2-12 conditioning sessions, each lasting approximately 20 min. One training session consisted of 75 paired, tone + light, trials and 25 randomly interspersed CS alone trials. The eyetracker (Tobii Pro Nano), continuously measured participants' pupil size. To test statistically whether conditioning of the pupillary response occurred we compared the pupil size after the tone on the first session and the last session. The results showed a complete lack of evidence of conditioning. Though the pupil size varied slightly between participants, the size did not change as a result of the training-irrespective of the number of training sessions. The data replicate previous findings that pupillary constriction does not show conditioning. We conclude that it is not possible to condition pupillary constriction-at least not by pairing a tone and a light. One hypothesis is that when pupillary conditioning has been observed in previous studies, it has been mediated by conditioning of an emotional response.

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Intrasaccadic perception triggers pupillary constriction.

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Intrasaccadic perception triggers pupillary constriction.

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