The brain of a one-week old zebrafish has about 100,000 neurons, about one-millionth the number in a human brain. Using a modern microscopy method called “whole-brain light-sheet imaging,” scientists can map the entire brain of a living zebrafish to see which groups of neurons work together to produce different behavior.
In this example, the fish is swimming in a virtual reality arena, and the imaged neurons shown in different colors are active when the fish navigates in a particular direction (green = left, red = right, blue = straight). Neurons sending axons to the spinal cord are labeled cyan, and the rest of the brain is labeled in grey.
Because zebrafish brains have a common basic anatomy with other vertebrate brains including humans, research like this helps us gain insight into how our brains work to observe the environment around us, decide which behavior to perform, and turn our experience into memories that determine our future behavior.
Timothy W. Dunn, Yu Mu, Sujatha Narayan, Owen Randlett, Eva Naumann, Chao-Tsung Yang, Alexander F. Schier, Jeremy Freeman, Florian Engert and Misha B. Ahrens (Janelia Research Campus, HHMI and Harvard University)