When you think too much about something, it carves a groove in your mind. Whether it’s about a person, a past occurrence, or a future event, overthinking will incise a channel in your brain that can be difficult to escape. Although these may sound like simple metaphors spoken by a hopeless romantic (perhaps partially true), there is actually a neurological basis for these claims.
In neuroscience, there is a set of interacting brain structures known as the “default mode network” (DMN). The DMN links parts of the cerebral cortex (the most recently evolved part of our brain) with deeper and evolutionarily older structures that partially control our memory and emotion. Serving as well-established neurological highways, the DMN is most active when our mind is “wandering,” or at rest, which are usually the times we are thinking about others, ourselves, or about the past or future (i.e. time travel in the brain). These linkages have been documented using neuroimaging techniques like fMRI, where brains in a passive state have heightened DMN pathway activity. Just as a river channel becomes more established as more water is discharged through it, the DMN is strengthened by the activation and passage of thoughts.
The neuroscientist Mendel Kaelen proposes a beautiful and relevant metaphor that involves picturing the brain as a snow-covered hill, with thoughts being sleds gliding down it. As more and more sleds glide down the hill, they are inevitably drawn into pre-existing tracks. This magnet-like effect represents our thoughts being pulled into the most well-traveled neural connections in our brains. Over time, it becomes more difficult to take any path other than the ones already established. This is how overthinking something becomes a positive feedback loop where the more you think about it, the more difficult it is to escape.
We’ve all been caught in a track before, and maybe some of us are currently stuck in one, but continued neuroscience research is helping us identify ways in which we can temporarily flatten the snow and create a mind that is more impressionable and free-thinking. The figure shown here is extracted from Michael Pollen’s book “How to Change Your Mind.” A clear opening of neural pathways is seen from left to right, which shows the communication between brain networks in placebo recipients and people given psychedelic drugs, respectively.