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Pupillary light reflex to light inside the natural blind spot
Kentaro Miyamoto1, Ikuya Murakami2
11] Department of Life Sciences, The University of Tokyo, Tokyo 153-8902, Japan [2] Department of Physiology, The University of Tokyo School of Medicine, Tokyo 113-0033, Japan [3] Japan Society for the Promotion of Science, Tokyo 102-8472, Japan.
Scientific Reports
|June 27, 2015
Summary
Perceptual filling-in of the blind spot (BS) does not always trigger the pupillary light reflex (PLR). However, white light covering the BS unexpectedly enhanced the PLR, suggesting melanopsin-containing retinal cells receive light within the BS.
Area of Science:
- Neuroscience
- Visual Perception
- Ophthalmology
Background:
- The human blind spot (BS) normally lacks photoreceptors, yet the brain fills in missing visual information.
- The short-latency pupillary light reflex (PLR) is an involuntary pupil response mediated by subcortical visual pathways.
Purpose of the Study:
- To investigate if perceptually filled-in visual surfaces within the BS influence the magnitude of the short-latency pupillary light reflex (PLR).
Main Methods:
- Participants were exposed to stimuli designed to cover or surround the optic nerve head's blind spot (BS).
- The size of the pupillary light reflex (PLR) was measured in response to different light stimuli presented to the BS.
- Stimuli included red and white surfaces and rings, with and without perceptual filling-in within the BS.
Main Results:
- A red surface that was perceptually filled-in within the BS did not elicit a PLR.
- Conversely, a large white disk covering the BS induced a significantly larger PLR compared to a white ring stimulus.
- The size of the PLR was not correlated with the participants' subjective perception of the stimuli on a trial-by-trial basis.
Conclusions:
- Perceptual filling-in alone does not appear sufficient to trigger the short-latency pupillary light reflex (PLR).
- Light projected onto the blind spot (BS) can enhance the PLR, suggesting activation of subcortical visual pathways.
- Melanopsin-containing retinal cells are hypothesized to be involved in detecting light within the BS and modulating the PLR.
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