Think of how you feel during a long lecture or meeting… Do you feel like your brain is about to burst? As much as you would like to excuse yourself on account of having a “full brain” and go grab lunch, that might not be possible… Unfortunately, the picture above is totally wrong! Instead, as a recent study in Nature Neuroscience found, your brain does not get “full” to the point where it stops working. It just forgets irrelevant old memories to make room for new ones that you need to remember.
The study, conducted by Maria Wimber and colleagues in the UK, used a brain imaging technique known as functional magnetic resonance imaging (fMRI) to see the process of forgetting as it unfolded inside the human brain. Wimber and colleagues designed their experiment based on prior research, which suggested that learning and forgetting work together. Specifically, learning a new piece of information causes your memories of other pieces of information (often those that are most similar to the new information) to weaken. Although this might seem like a problem, neuroscientists argue that it actually helps you to recall relevant information as easily as possible.
To see forgetting inside the brain, participants in Wimber and colleagues’ study were asked to remember a word (e.g., “sand”) paired with two images (e.g., Marilyn Monroe and a hat). Throughout the experiment, participants retrieved the memory of “sand + Marilyn Monroe” four times. As a result of repeated retrieval, this combination became the stronger “target memory”, and the “sand + hat” pair became the similar “competing memory.”
While participants completed the task, Wimber and colleagues monitored their brain activity with fMRI. As the target memory was retrieved again and again, the researchers found that the brain activity associated with it increased. However, brain activity associated with the competing memory decreased, or was inhibited. Additionally, Wimber and colleagues noted that these changes were largest in areas near the front of the brain, particularly in the prefrontal cortex. Since prior research showed that the prefrontal cortex is involved in retrieval, the fact that there was activity in this area suggested that forgetting the competing memory was related to more efficient retrieval of the target.
If you have reached the end of this post, you may be worried about how easily your brain can forget things, and you may be wondering about techniques you can use to improve your memory. Before you click “Order Now!” to get that memory-enhancing computer game advertised on last night’s 3 AM infomercial, it is important to realize that forgetting is critical for making your brain run smoothly. Consider this scenario:
You spend three weeks reading a book. During that time, you commit all of the character’s names to memory, and remember details of the plot. When you finish the book, you move on to another one, obviously with different characters and a different plot. Since it would be difficult to remember the new book with details from the old one still in your head, the old information is gradually forgotten and replaced. Just think what it would be like if you remembered every detail of every book you ever read… It would be completely overwhelming!
As a result, one could say that your brain depends on forgetting to remember, but fortunately, it does not need to remember to forget.
Chudler, E. H. (2015). Functional Divisions of the Cerebral Cortex. Retrieved from https://faculty.washington.edu/chudler/functional.html
Devlin, H. (2013). What is Functional Magnetic Resonance Imaging (fMRI)? Retrieved from http://psychcentral.com/lib/what-is-functional-magnetic-resonance-imaging-fmri/
Kuhl, B. A., Dudukovic, N. M., Kahn, I., & Wagner, A. D. (2007). Decreased demands on cognitive control reveal the neural processing benefits of forgetting. Nature Neuroscience, 10(7), 908-914.
Kumfor, F., & Sicong, T. (2015). Health Check: can your brain be 'full'? Retrieved from https://theconversation.com/health-check-can-your-brain-be-full-40844
Merriam-Webster. (Ed.) (2015) Merriam-Webster (Online ed.). Springfield, MA: Merriam-Webster, Inc.
Preston, A. R., & Eichenbaum, H. (2013). Interplay of Hippocampus and Prefrontal Cortex in Memory. Current Biology, 23(17), R764-R773.
Wimber, M., Alink, A., Charest, I., Kriegeskorte, N., & Anderson, M. C. (2015). Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression. Nature Neuroscience, 18(4), 582-589.
Wimber, M., Bauml, K.-H., Bergstrom, Z., Markopoulos, G., Heinze, H.-J., & Richardson-Klavehn, A. (2008). Neural Markers of Inhibition in Human Memory Retrieval. The Journal of Neuroscience, 28(50), 13419-13427.