Stanford Researchers Put Flies on Spherical Treadmills in Motion Perception Experiment

Posted on January 30, 2014

Stanford researchers put flies on a spherical treadmill in order to understand how flies perceive motion. The researchers say they found flies perceive motion in a similar way to humans. Take a look:

Stanford's Thomas Clandinin, an associate professor of neurobiology and one of the authors of the study, says in a release, "What's really exciting to me is that no one would have expected this deep similarity between two animals that are so evolutionarily different."

The scientists say both humans and flies discern three types of information about a moving object: its speed, direction of motion and brightness. Human volunteers were tested by watching videos while researchers monitored their scalp electroencephalogram (EEG) signals. The human participants answered questions about their perception of motion based on the videos they were watching.

The flies were tethered to sticks and placed on tiny spherical treadmills. Videos were screened to the flies while their movements were monitored by scientists. The researchers could not ask the flies which way an image was moving, but scientists know that flies turn in the direction of motion and were able to use this fly fact when conducting the experiment.

The research was published here in Nature Neuroscience. The researchers say in the paper, "We found that fly and human visual systems encode the combined direction and contrast polarity of moving edges using triple correlations that enhance motion estimation in natural environments. Both species extracted triple correlations with neural substrates tuned for light or dark edges, and sensitivity to specific triple correlations was retained even as light and dark edge motion signals were combined. Thus, both species separately process light and dark image contrasts to capture motion signatures that can improve estimation accuracy. This convergence argues that statistical structures in natural scenes have greatly affected visual processing, driving a common computational strategy over 500 million years of evolution."