How do memories persist? A tasty insight
The latest research from npj Science of Learning
Taste plays a surprisingly strong role in memories. A massaman curry at your local Thai restaurant might instantly transport you back to the beaches of southern Thailand. Or maybe the slightly sharp taste of the beef burrito you had a few years ago predicted intestinal turmoil and has, as a result, kept you well away from anything resembling Mexican takeout ever since.
The second example, in which taste led to bad consequences, is probably the main reason that taste memories can be so strong; it’s a way to protect against future food-induced harm and therefore serves an important evolutionary purpose. The strength of this learning is appealing to researchers, who use a similar process to study taste memories in animals. In this laboratory test, an animal is trained to eat something it likes, perhaps something sweet, but at the same time experimenters secretly feed it something that upsets its stomach. Afterwards, the animal forms a memory that makes it avoid the sweet food. This is conditioned taste aversion, or CTA.
In this study, the researchers used CTA to understand memories at a molecular level. Specifically, their question was whether new proteins need to be made just to form a long-term memory, or whether they can also affect how well the memory persists. Proteins are the ultimate product of genes turning on, and do all sorts of different things in a cell. It’s already quite well known that for a memory to last more than an hour or so, new proteins need to be made. The key insight from this study is that new proteins that affect memory persistence continue to be made for days after the memory has been formed. What’s more, whereas making new proteins helps in forming long-term memories, making new proteins hinders the persistence of a memory that has already formed. In other words, the same process (making new proteins) has opposite effects on memory, depending on when during learning that process occurs.
The bigger picture
How relevant is this research to learning in humans, for example in the classroom? Right now, not very. But all of us must have wondered why some memories last and others don’t, and knowing the molecular details of memory persistence opens up the potential to tinker with the process. Maybe a drug will be developed that helps convert short-term memories into long-term memories. According to this investigation, the same drug, given at a different time, might make long-term memories less persistent, with the potential for alleviating post-traumatic stress disorder.
The dual effect of the drug used in this particular study raises concerns that enhancing one memory could simultaneously disrupt a memory that was formed earlier. There would also be questions of how specific such a drug could be for a given memory or learning process, and the perennial problem of drug delivery would need to be overcome. There are also ethical issues to consider: is a drug to artificially enhance learning ok by society? Under what circumstances? What if, as would be likely, the drug was more easily accessible to the rich than the poor?
To be clear, this isn’t happening in a hurry. These are issues for the future, but realistically ones that we should be considering now, before significant artificial cognitive enhancement becomes a reality.