Secret to interpreting neural code found in pitch-dark maze

All the information the body sends to the brain – like what we can see, hear, smell and feel – gets sent through nerves as electrical impulses called spike trains.

The rulebook for how the brain decodes spike trains is unknown, and working it out is made harder by the fact that the nervous system often carries the same message in many different ways. When the different versions of the same message reach the brain, it interprets all these signals together to decide how to behave. Professor Petri Ala-Laurila and his teams at Aalto University and the University of Helsinki have now been able to link behaviour in a mouse to specific spike-trains originating in its eyes.

The mice had been trained swim towards an extremely faint light in a pitch-dark maze, and the team measured how effective the mice were at finding it. Darkness had to be used because it critically reduces the number of relevant spike trains to the two most sensitive ones to dim light: one called the ON channel and one called the OFF channel. By creating a scenario where there are a limited number of spike trains getting sent for a specific input, the team were able to isolate which individual spike train controlled behaviour.