Teaching a computer to behave like a zebrafish wasn’t Martin Haesemeyer’s goal.
In fact, the research associate in the labs of Florian Engert, professor of molecular and cellular biology, and Alexander Schier, the Leo Erikson Life Sciences Professor of Molecular and Cellular Biology, was hoping to build a system that worked differently than zebrafish with an eye toward comparing how both process temperature information.
What he got instead was a system that almost perfectly mimicked the zebrafish — and that could be a powerful tool for understanding biology. The work is described in a July 31 paper published in Neuron.
“Initially, what I was curious about was some kind of comparison study, to look at zebrafish and something like Drosophila and see if their brains do this the same way,” Haesemeyer said. “And as a cheaper alternative than getting another animal to do it, I chose the artificial neural network, and I was surprised it worked so well.”
Using open-source software tools, Haesemeyer built a neural network with an architecture different from that of the zebrafish brain, gave it some basic rules on how to process temperature changes, and then allowed it to “learn” how to do it for itself.
“Essentially, what the network learns is … a filter function for extracting rates of change from a stimuli,” Haesemeyer said. “It makes what it thinks is the best movement, and then as the inputs change because it’s in a different place, it moves again, and starts to navigate the heat gradient. And after learning, it can do that quite well.”
But it wasn’t simply the network’s ability to navigate that interested Haesemeyer — it was the fact that it seemed to do it in a way identical to the fish.
“There were two things I looked at,” he said. “The first was, for lack of a better term, how well did its behavior compare to zebrafish? Does it follow similar rules to zebrafish? And indeed it does.
“I can also measure how quickly it integrates stimulus,” he continued. “I had earlier done that with zebrafish, and the results from the artificial network agree, so even though I didn’t tell the network that it should pay attention to the temperature every half-second, which the fish does, it learned a similar skill.”