In some experiments the light controls were engineered to alter how the flies jump, beat their wings and fly in an escape response. In other experiments, the light controls were used to activate dopamine neurons that stimulated walking and affected the types of paths the flies chose to follow. Loss of dopamine cell activity in humans underlies Parkinson's disease, a movement disorder.
Unfocused laser light was used to "broadcast" the signal to genetically engineered "phototriggers" that were expressed only in specific groups of cells. Changing conditions of the light pulses altered the activity level of the flies and the direction of their flight. These responses to laser light demonstrated a direct link between specific neurons and specific behaviors.
Gero Miesenböck, associate professor of cell biology at Yale, and principal investigator of the study, explained that the photoreceptors are ion channels that spark action potentials when illuminated. Depending on which neurons are light-sensitive, the remote-controlled flies jump, fly or change their walking patterns on command.
"The ability to control brain functions non-invasively opens many new possibilities for the analysis of neural circuits, the search for the cellular substrates of behavior, and, possibly even restoring function after injury or disease," said Miesenböck "This is a significant step toward moving neuroscience to active and predictive manipulation of behavior."
But, is it mind control? The authors demonstrate that even headless flies take mindful flight if the correct set of neurons is photo-activated.
Miesenböck and Susana Lima, a graduate student and co-author of the paper, anticipate that a future remote control system may be the way to study how neural circuits are wired and how they function, as well as how cell actions and connections are related to more complex behaviors like learning, aggression and even abstract thought. The optical controls might also enable the construction of "bionic" computers -- hybrid devices in which neural circuits are interfaced with electronic circuits.
The work was funded by grants from the National Institutes of Health and Miesenböck was supported as a Searle Scholar, an Alfred P. Sloan and Klingenstein Fellow and a Beckman Young Investigator.
Citation: Cell: (April 8, 2005)