Last weekend, I went to a cinema in the USA for the first time. I was conscious of two things—taking in the cine-going experience in a new country, and reminiscing about the last time I was at a theatre with my friends a year ago.
Is This Memory Already Stored Inside Me?
When we come across a situation, there are two conflicting processes that can take place- a new memory can be formed, or an old memory can be retrieved. Both these processes involve a common region of the brain called the hippocampus. However, despite the effortlessness with which we form memories and simultaneously recall old ones, the two processes themselves involve very different networks. Recalling a memory involves maximizing overlap with existing memories. On the contrary, forming a new memory involves minimizing the overlap with other memories. These are two conflicting requirements; how, then, does the brain decide what to do?
Recent experiments by researchers at Columbia University and New York University are showing that this decision is influenced by incidents prior to the decision. That is, prior incidents bias our brain either towards forming a new memory or towards recalling an existing one.
Participants were presented with pictures of novel and familiar objects and asked to classify them into one of three classes— identical, different, or similar but not identical to a previously encountered object. The ‘test’ objects were very similar to previous objects, but had subtle differences. It was found that participants who had been primed with a series of new objects tended to classify these as not identical, whereas participants who had been primed with familiar objects tended to classify them as identical. In another experiment, participants were found to form links between overlapping memories better if these overlapping memories had been formed after a retrieval of a memory, and their ability to form links between memories was less if the memories had been formed after a new memory had been formed. That is, a preceding experience definitely affects how a memory is stored in the brain with respect to other memories.