Neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time. Representational drift occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery. How can animals possibly make any lasting sense of the world if their neural responses to that world are constantly in flux? If such flux is common, “there must be mechanisms in the brain that are undiscovered and even unimagined that allow it to keep up.”

• Uncategorized