Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Involuntary Maybe, but Certainly Not Random

16.02.2009
Our eyes are in constant motion. Even when we attempt to stare straight at a stationary target, our eyes jump and jiggle imperceptibly.

Although these unconscious flicks, also known as microsaccades, had long been considered mere “motor noise,” researchers at the Salk Institute for Biological Studies found that they are instead actively controlled by the same brain region that instructs our eyes to scan the lines in a newspaper or follow a moving object.

Their findings, published in the Feb. 13, 2009 issue of Science, provide new insights into the importance of these movements in generating normal vision.

“For several decades, scientists have debated the function, if any, of these fixational eye movements,” says Richard Krauzlis, Ph.D., an associate professor in the Salk Institute’s Systems Neurobiology Laboratory, who led the current study. “Our results show that the neural circuit for generating microsaccades is essentially the same as that for voluntary eye movements. This implies that they are caused by the minute fluctuations in how the brain represents where you want to look.”

“There was a lot of past effort to figure out what fixational eye movements contribute to our vision,” adds lead author Ziad Hafed, Ph.D., Sloan-Swartz Fellow in the Systems Neurobiology Laboratory, “but nobody had looked at the neural mechanism that generates these movements. Without such knowledge, one could only go so far in evaluating microsaccades’ significance and why they actually exist.”

Wondering whether the command center responsible for generating fixational eye movements resides within the same brain structure that is in charge of initiating and directing large voluntary eye movements, Hafed decided to measure neural activity in the superior colliculus before and during microsaccades.

He not only discovered that the superior colliculus is an integral part of the neural mechanism that controls microsaccades, but he also found that individual neurons in the superior colliculus are highly specific about which particular microsaccade directions and amplitudes they command—whether they be, say, rightward or downward or even oblique movements. “Data from the population of neurons we analyzed shows that the superior colliculus contains a remarkably precise representation of amplitude and direction down to the tiniest of eye movements,” says Krauzlis.

The Salk researchers, in collaboration with Laurent Goffart, Ph.D., a professor at the Institut de Neurosciences Cognitives de la Méditerranée in Marseille, France, also temporarily inactivated a subset of superior colliculus neurons and analyzed the resulting changes in microsaccades. They discovered that a fully functional superior colliculus is required to generate normal microsaccades.

“Because images on the retina fade from view if they are perfectly stabilized, the active generation of fixational eye movements by the central nervous system allows these movements to constantly shift the scene ever so slightly, thus refreshing the images on our retina and preventing us from going ‘blind,’” explains Hafed. “When images begin to fade, the uncertainty about where to look increases the fluctuations in superior colliculus activity, triggering a microsaccade,” adds Krauzlis.

Microsaccades may, however, do more than prevent the world around us from fading when we stare at it for too long. Even when our gaze is fixed, our attention can shift to an object at the periphery that attracts our interest. In an earlier study, Hafed discovered that although we may avert our eyes from an attractive man or woman, microsaccades will reveal such objects of attraction because their direction is biased toward objects to which we are unconsciously attracted.

By showing in the current study that the superior colliculus is involved in generating microsaccades, Hafed and his colleagues could now explain why this happens. “The superior colliculus is a major determinant of what is behaviorally relevant in our visual environment, so paying attention to one location or the other alters superior colliculus activity and therefore alters these eye movements as well,” says Hafed.

The Salk Institute for Biological Studies in La Jolla, California, is an independent nonprofit organization dedicated to fundamental discoveries in the life sciences, the improvement of human health, and the training of future generations of researchers. Jonas Salk, M.D., whose polio vaccine all but eradicated the crippling disease poliomyelitis in 1955, opened the Institute in 1965 with a gift of land from the City of San Diego and the financial support of the March of Dimes.

Gina Kirchweger | Newswise Science News
Further information:
http://www.salk.edu

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>