When we experience something, it is no-brainer that we make a memory out of it. It starts as a short-term memory
and if significant
enough, are then slowly converted into a long-term one.
However, scientists from Riken-MIT Center for Neural Circuit Genetics found new data showing that memories were actually formed simultaneously in the hippocampus (short-term memory)and the cortex (long-term memory), challenging the long-held fact that memories are first formed in the former and then stored in the latter as solidified in the case of Henry Molaison in the 1950s. Molaison had a brain
surgery to treat his epilepsy which damaged his hippocampus, disabling him to form new memories. He can, however recall memories before he had the operation, leading neuroscientists to conclude that the hippocampus was the area responsible for making fresh memories.
Utilizing mice, they've control the activity of its individual neurons
using a light beamed into the brain. This means that they could literally turn the memories on and off. So, the researcers turned off the short-term memory in the hippocampus and manually turned on the long-term memory. Results showed that even when the short-term memory is absent, the mice can still remember as long as there's still the long-term one.
This showed that while the storage area of both memories is still the same, we are actually making two sets of memories at the same time- both in the cortex and the hippocampus simultaneously. Whilst only the neurons in the hippocampus fire memory retrieval for the first few days, memories in the cortex mature eventually.
These results surprised even the authors. "This is contrary to the popular hypothesis that has been held for decades. This is a significant advance compared to previous knowledge, it's a big shift," Prof. Susumu Tonegawa told the BBC News
. This discovery can actually aid in some diseases such as dementia and Alzheimer's! As what Prof. Tonegawa said, "Understanding how this happens may be relevant in brain disease
So that memory of new coffee you've tasted yesterday or that cute dog you've seen last week along the way has actually been input both in your short-term and long-term memories (even this article)! Oh, interesting.