There are a million things that we do every day without thinking. Brushing our teeth, drying our hair after a shower, and unlocking our phone screen so we can check our messages are all part of our routine. But what takes place in the brain as we learn a new habit? Share on Pinterest What happens in the brain when habits take shape? What’s something you’ve learned to do without thinking? It might be locking the door behind you as you leave, which could lead to some panic later as you wonder if you actually remembered to do it. It might be driving to work. Have you ever had that uncanny experience of finding yourself at your destination without fully remembering how you got there? I certainly have, and it’s all thanks to the brain’s trusty autopilot mode. Habits drive our lives — so much so that sometimes we might want to break the habit, as the saying goes, and experience something new. But habits are a useful tool; when we do something enough times, we become effortlessly good at it, which is perhaps why Aristotle reportedly believed that “excellence […] is not an act but a habit.” So, what does habit formation look like in the brain? How do our neural networks behave as we learn something and consolidate it into an effortless behavior through repetition? These are the questions that Ann Graybiel and her colleagues — from the Massachusetts Institute of Technology in Chestnut Hill — set out to answer in a recent study, the findings of which are published in the journal Current Biology.

‘Bookending’ neural signals Although a habitual action seems so simple and effortless, it actually typically involves a string of small necessary movements — such as unlocking the car, getting into it, adjusting the mirrors, securing the seatbelt, and so on. This complex set of movements that amount to one routine action that we perform unconsciously is called “chunking,” and although we know that it exists, exactly how “chunks” form and stabilize has remained mysterious so far. The new study now suggests that some brain cells are tasked with “bookending” the chunks that correspond to habitual actions. In another study, Graybiel and her former team found that the striatum, a region of the brain previously associated with decision-making, also plays an important role in acquiring habits. Working with mice, the team noted that the patterns of signals transmitted between neurons in the striatum shifted as the animals were taught a new sequence of actions — turning in one direction at a sound signal while navigating a maze — which then evolved into a habit. At the beginning of the learning process, the neurons in the mice’s striata emitted a continuous string of signals, the scientists saw, but as the mice’s actions started to consolidate into habitual movements, the neurons fired their distinctive signals only at the beginning and at the end of the task performed. When a signaling pattern takes root, explain Graybiel and colleagues, a habit has taken shape and breaking it becomes a difficult endeavor.