Watching Fish Think

Written by on February 5, 2013 in Fish, Marine Life
Adult Zebrafish.

Adult Zebrafish. Photo credit: NOAA.

For the first time, scientists watched a fish think. They successfully imaged the brain activity of a zebrafish and were able to see it thinking while it watched its prey.

The researchers used zebrafish because their larvae have translucent heads, making it exceptionally easy to see their brains. To see the thinking process, the researchers developed a genetically engineered protein that lights up when brain cells fire. They then bred zebrafish to express the protein in a region of the brain that controls eye movement. They were able to see signals in the fish’s brain whenever something moved in front of the fish.

The researchers conducted a series of experiments to map the brain activity of the zebrafish larvae:

  1. They placed a dot–moving back and forth or blinking on and off–in front of the fish. Under a fluorescent microscope, the scientists watch the signals in the fish’s brain mirror the movement of the dot.
  2. They placed prey (a live paramecium) within sight of the zebrafish but didn’t allow the fish to move. They were able to watch the fish track the paramecium’s movement.
  3. They placed the paramecium in the same dish as the fish and allowed the fish to swim freely. They watched as the fish found and swam towards the prey.

In addition to tracking eye movement, this technique could be used to map other areas of the brain that are involved in locomotion or even behavior.

Translucent juvenile zebrafish.

Translucent juvenile zebrafish. Photo courtesy of the National Institutes of Health.

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Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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