How do researchers find the cells that hold one memory? · Grey Matter

They mark the neurons that are active while an animal learns and then switch those same neurons back on.

How do researchers find the cells that hold one memory?

They mark the neurons that are active while an animal learns and then switch those same neurons back on. In the mice used by Tonegawa's laboratory, a neuron that turns on the activity gene c-fos also makes a light-gated channel, but only during a window opened by withdrawing a drug from the diet, so only the cells active during that one experience are tagged. Shining light through an implanted fibre onto the tagged cells of the dentate gyrus made the mice freeze as if they were back in the box where they had learned to fear a shock. Cells tagged in a harmless box did not, which is what shows the tag captured that particular memory.