"How a fly's brain calculates its position in space." "Flies are relatively unperturbed by the indignities of wind currents."

"Cheng Lyu, a graduate student in the Gaby Maimon lab, glued fruit flies to miniature harnesses that hold only the insects' heads in place, enabling him to record brain activity while leaving the flies free to flap their wings and steer their bodies through a virtual environment. The setup contained several visual cues, including a bright light representing the sun and a field of dimmer dots that could be adjusted to make the fly feel like it was being blown backward or sideways."

"As expected, the head direction cells consistently indicated the fly's orientation to the sun, simulated by the bright light, independently of the dimmer dots' motion. In addition, the researchers identified a new set of cells that indicated which way the flies were traveling, and not just the direction their head was pointing. For example, if the flies were oriented directly toward the sun in the east while being blown backward, these cells indicated that the flies were (virtually) traveling west." "This is the first set of cells known to indicate which way an animal is moving in a world-centered reference frame."

"A physics student plotting an object's trajectory will break the trajectory into components of motion, plotted along the x- and y-axis. Similarly in the fly brain, four classes of neurons that are sensitive to visual motion indicate the fly's traveling direction as components along four axes. Each neuronal class can be thought of as representing a mathematical vector. The vector's angle points in the direction of its associated axis. The vector's length indicates how fast the fly is moving along that direction." "Amazingly, a neural circuit in the fly brain rotates these four vectors so that they are aligned properly to the angle of the sun and then adds them up. The result is an output vector that points in the direction the fly is traveling, referenced to the sun."

"Vector math is more than just an analogy for the computation taking place. Rather, the fly brain appears to be literally performing vector operations."

How a fly's brain calculates its position in space

#discoveries #neuroscience