Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Our pupil moves to the rhythm of the environment

08.05.2020

Regular processes in the environment improve our eyesight

When we find something particularly beautiful or impressive, we literally get big eyes: Our pupils dilate. The pupil controls how much light enters the eye and falls on the retina.


The pupil opens and closes quickly in the rhythm of the incoming light (purple). If there is also a light-independent environmental rhythm (orange), the pupil is also controlled by this rhythm.

Caspar M. Schwiedrzik

When there is a lot of light, the pupil contracts; when there is little light, it opens again. Neuroscientists from the German Primate Center (DPZ) - Leibniz Institute for Primate Research and the European Neuroscience Institute Göttingen have now found out in a study of humans and rhesus monkeys that the movement of the pupil is not only reflexively controlled by the amount of incident light, but unconsciously also by our mind.

Thus, the pupil can follow rhythms that arise in the environment. In this way, the opening of the pupil is optimally adapted to our environment which enhances perception (Journal of Neuroscience).

... more about:
»Neuroscience »Pupil »diameter »rhesus monkeys »rhythm

Sensory impressions from our environment are often rhythmic, not only when we hear, but also when we see. For example, the blue light of a passing ambulance flashes about 120 times per minute.

We also react unconsciously to visual events in our environment, which can be registered by our senses as regular patterns. From these patterns our brain can, for example, deduce when the next flash of blue light will hit the eye and prepare itself for it.

An important factor in vision is the adjustment of the pupil diameter. Smaller pupils provide a sharper image, while larger pupils allow more light to reach the retina, making it more likely that even weak stimuli will be processed at all.

Pupil diameter is controlled by the pupillary reflex, which automatically, i.e. without our knowledge or intention, adjusts the pupil muscles to the incidence of light. But not all relevant environmental information is contained in the amount of incident light alone.

Computations are therefore required in the brain that go beyond the capabilities of a reflex to take into account all available information. The aim of this study, funded by the German Research Foundation (DFG), was to find out whether and to what extent pupil dynamics are controlled fully automatically or whether they are also influenced by more complex rhythms in the environment.

For the investigations, pupil movements of two male rhesus monkeys (Macaca mulatta) and several test subjects of both sexes were measured using a high-speed video camera, while the subjects were shown sequences of images of human faces at a temporal frequency of two hertz. A dark background was shown between the images.

The alternation of background and image causes the pupil to dilate and contract in rhythm with the images. During the experiments, the order of the images was manipulated - they were grouped in pairs so that a particular image always followed a particular other image.

Thus, there are two rhythms to which the pupil reacts: a fast one (two hertz), which results from the alternation of image and background, and one at half that pace (one hertz), which results from the arrangement of the images as pairs.

The sequence of the pairs is not given by the light itself, and therefore requires an additional computation of environmental rhythms in the brain. Since the luminance of the faces in all pictures as well as the dark background in the "pauses” remained unchanged, but the arrangement of the pictures varied, conclusions could be drawn about the influence of this additional computation on pupil dynamics.

In addition to the structured sequence, randomly arranged images with the same frequency (two hertz) were shown. A comparison of the results between structured and unstructured image sequences at the same image frequency shows that in both species studied the pupil follows not only the light-related rhythm of the images, but also the more complex rhythm of the pairs.

Pupil movement in a slow (one hertz) rhythm keeps the pupil open longer, as if a pair should not be interrupted by the closing of the pupil. This allows more light to reach the retina. "The additional information contained in the environment thus complements the information already reaching the retina via the incident light," says Caspar Schwiedrzik, head of the junior research group "Perception and Plasticity".

Furthermore, the study was able to show that this contributes to an improvement in perception, even if the test subjects are not aware that there is a rhythm in the environment. "Pupil control is therefore not purely reflexive, but is also influenced by our unconscious thoughts," adds Schwiedrzik.

Wissenschaftliche Ansprechpartner:

Dr. Caspar Schwiedrzik
Phone: +49 (0) 551 39-61371
Email: CSchwiedrzik@dpz.eu

Originalpublikation:

Schwiedrzik CM, Sudmann SS (2020): Pupil diameter tracks statistical structure in the environment to increase visual sensitivity. Journal of Neuroscience, JN-RM-0216-20; DOI: https://doi.org/10.1523/JNEUROSCI.0216-20.2020

Weitere Informationen:

http://medien.dpz.eu/pinaccess/pinaccess.do?pinCode=ucPoJnKmjTwO - Printable pictures
https://www.dpz.eu/en/home/single-view/news/unsere-pupille-bewegt-sich-im-rhythm... - Presse release on DPZ website

Dr. Susanne Diederich | idw - Informationsdienst Wissenschaft

Further reports about: Neuroscience Pupil diameter rhesus monkeys rhythm

More articles from Life Sciences:

nachricht Enzymes as double agents: new mechanism discovered in protein modification
07.07.2020 | Westfälische Wilhelms-Universität Münster

nachricht Protein linked to cancer acts as a viscous glue in cell division
07.07.2020 | Rensselaer Polytechnic Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

Im Focus: Gentle wall contact – the right scenario for a fusion power plant

Quasi-continuous power exhaust developed as a wall-friendly method on ASDEX Upgrade

A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...

Im Focus: ILA Goes Digital – Automation & Production Technology for Adaptable Aircraft Production

Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

 
Latest News

Quick notes in the genome

07.07.2020 | Life Sciences

Limitations of Super-Resolution Microscopy Overcome

07.07.2020 | Life Sciences

Put into the right light - Reproducible and sustainable coupling reactions

07.07.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>