Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Zebrafish yield clues to how we process visual information

02.11.2010
To a hungry fish on the prowl, the split-second neural processing required to see, track, and gobble up a darting flash of prey is a matter of survival.

To scientists, it's a window into how our brain coordinates the eye motions that enable us to hit a baseball, sidestep an errant skateboarder, and otherwise make our way in a world full of danger and opportunity.

This process is now better understood, thanks to a team of scientists that imaged the activity of individual neurons in a part of a zebrafish's brain called the optic tectum. The optic tectum receives signals from the retina, filters them, then sends the signals to other parts of the brain that control motion.

They found that when the fish saw something that resembles prey zipping by, the output neurons in the optic tectum are strongly activated. These output neurons send signals to the rest of the brain — a jolt to spark the fish into action and give chase.

But when the fish saw large flashes of light and dark, the equivalent of a bland world devoid of potential prey, the output neurons in the optic tectum are weakly activated.

"We can see, for the first time, how neurons in the fish's optic tectum take visual information and convert it into an output that drives action," says Ehud Isacoff, a biophysicist who holds joint appointments with Lawrence Berkeley National Laboratory's Physical Biosciences and Materials Sciences Divisions and UC Berkeley's Department of Molecular and Cell Biology.

Isacoff conducted the research with a team of scientists that includes Claire Wyart, a scientist in his UC Berkeley lab; Filippo Del Bene of Herwig Baier's University of California at San Francisco lab; and Loren Looger of the Janelia Farm Research Institute in Virginia.

They report their research in the October 29 issue of the journal Science.

Their work could shed light on how we process visual information. The optic tectum in fish is related to the superior colliculus in the human brain, which coordinates eye motion.

"We are particularly sensitive to high-contrast, moving objects that fill only a small portion of our visual field," says Isacoff. "When you stand next to a busy road and track cars going by, the coordination of the motor control in the eyes that allows you to visually track cars is very important."

To learn more about this flow of visual information, the scientists used a state-of-the-art combination of fluorescent imaging and microscopy. Fish were genetically developed in which specifically targeted neurons in their optic tectum expressed a gene encoding an engineered fluorescent protein. The protein lights up whenever calcium enters the cell during electrical activity. Using fast microscopy to observe this fluorescence, the scientists watched individual neurons blink on and off as they transmit signals.

When the fish were shown movies that blanketed much of their visual field with stimuli, the neurons in the output portion of the optic tectum sent a weak signal to the rest of the brain. No food, no action.

But when the fish watched a movie of thin, moving black bars that mimic the size and speed of swimming prey such as paramecia, the output portion of the optic tectum lit up.

"We identified a difference in the optic tectum's output between visual information that covers the whole visual field versus a small object moving across it," says Isacoff.

The scientists next set out to determine what happens inside the optic tectum to cause this difference. How does the optic tectum take visual information from the retina that indicates potential prey, and translate it into a call to action on the output side?

They found that a movie that stimulates the entire visual field activates a wide swath of neurons in the input portion of the optic tectum, including many inhibitory neurons. These inhibitory neurons conspire to drown out the signal as it travels deeper through the optic tectum. By the time the signal arrives at the output portion of the optic tectum, it's very faint.

"The inhibition is so dominant that it kills the signal," says Isacoff.

But when a tiny object moves across the visual field, a much smaller number of inhibitory neurons are excited. This allows a tiny sliver of signal to travel through the optic tectum and arrive at the output portion largely uninhibited.

The scientists tested the role of inhibitory neurons by blocking the neurons' function and observing how this impairment affected the zebrafish's ability to catch prey.

"We know that the inhibitory neurons are the key to this process because if we interfere with their function the animal loses the ability to hunt," says Isacoff.

The research was supported in part by the National Institutes of Health's Nanomedicine Development Center for the Optical Control of Biological Function and by a Frontiers in Integrative Biological Research grant from the National Science Foundation.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California for the DOE Office of Science. Visit our website: http://www.lbl.gov/

Dan Krotz | EurekAlert!
Further information:
http://www.lbl.gov

More articles from Life Sciences:

nachricht Tag it EASI – a new method for accurate protein analysis
19.06.2018 | Max-Planck-Institut für Biochemie

nachricht How to track and trace a protein: Nanosensors monitor intracellular deliveries
19.06.2018 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Carbon nanotube optics provide optical-based quantum cryptography and quantum computing

19.06.2018 | Physics and Astronomy

How to track and trace a protein: Nanosensors monitor intracellular deliveries

19.06.2018 | Life Sciences

New material for splitting water

19.06.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>