20 Second Memory Can Save a Life

Earlier in the semester, we talked about certain animals that used specific techniques to escape their predators such as the moths that used the E1 and E2 receptors in their ears to detect how far or close the bat was from them so that they could get away in time. Likewise, Zebrafish larvae use a rare form of memory to get away from its predators' attacks. An experiment performed on the Zebrafish larvae by researchers at the University of California, Berkeley showed that the larvae seem to have the ability to remember a rhythm taught to them by using flashes of light for about 20 seconds after the flashes stop. In the experiment, when the light was flashed the larvae moved their tails according to the beat of the flashes, and when the light was turned off the larvae continued to move its tail in the same exact beat for about 20 seconds longer. Also the brain activity was examined during the flashing and after the flashing stopped, and the results showed that their brains portrayed activity that was adjusted to the rhythm (of the flashes) even after the flashes ceased .

Researchers believe that the Zebrafish larvae use this short span of memory to their advantage. To us humans 20 seconds might mean absolutely nothing but as for the Zebrafish whose greatest fear is being attacked by the dragonfly larvae, 20 seconds mean the chance to live a little longer than expected. Researchers say that the dragonflies' attacks may be somewhat rhythmic and thus by learning the rhythm of their attacks the Zebrafish are able to predict and break away from the next attack.

The article can be found here.


Update: Well the experiment was done to get an in depth idea of how animals keep track of smaller increments of time. For instance we know that many animals regulate their day through their internal biological clock known as the circadian rhythm, but researchers are now interested to know if they are able to perform activities that require them to keep account of smaller periods of time ("like how quickly their predators are approaching," http://sciencenow.sciencemag.org/cgi/content/full/2008/1015/2). In the specific experiment explained in my article, the researchers saw that the zebrafish larvae flipped their tails every time the light flashed at six second intervals, and even after the lights were turned off they continued to flip their tails at the same rhythm very precisely. Researchers tested the larvae's ability to learn the rhythms at different durations and frequencies of the light flashing and they never failied to learn the pattern. Even though they weren't able to remember the pattern for too long, as a matter of fact no longer than 20 seconds this still proves that they are able to keep track of small intervals of time (in seconds and minutes) and thus can use this to defend themselves from their predators.

Also some of you were confused with how this memory span actually helps them escape from their predators. It is not that the flashing of the lights exactly imitates their predators attacks, but them being able to learn a rhythm helps them predict the next attack and escape as fast as possible. In terms of the zebrafish larvae whose predator is the dragonfly larvae, the 20 second memory span does seem quite beneficial. The dragonfly larvae is known to be very unsuccessful in attacking its prey. So when the dragonfly first misses its prey, it takes them a couple of seconds to re-adjust and attack again, thus if the dragonfly misses a couple of times it allows the zebrafish to learn the pattern of the attack and predict the next attack and escape accordingly.


Posted by Tazneena Ishaque (9)