Then they exposed all the tadpoles, however they were reared, to blue LED light flashes delivered via a fiber optic cable mounted next to the eye.
What they found over the course of several experiments was that the neural networks in the tectums of tadpoles reared under normal conditions developed a faster, more cohesive, and stronger response (in terms of the number of neurons) to light.
The tectal neural networks of tadpoles kept in the dark during development failed to progress at all. Those whose NMDA receptors were blocked occupied a middle ground, showing more progress than dark-reared tadpoles but less than normal tadpoles. Tadpoles, they found, train their brains with the light they see.
Aizenman said he hopes the calcium ion imaging technique will prove useful in a wide variety of other neuroscience experiments, including studying how tadpoles neurally encode behaviors such as fleeing when they see certain stimuli.
In the meantime, his team and Berson's have added to the understanding scientists have been building of how creatures turn the somewhat mushy approximations of their brains at birth into high-functioning animal minds.
"That's what everybody is after," Aizenman said. "How do you get this fine-tuned, finely wired brain in the first place?"
|Contact: David Orenstein|