New insight into how the brain encodes and accesses memory
Several decades ago, scientists from the UK and Norway received the Nobel Prize for memory-related research. In the course of their work, they discovered something known as ‘place cells’ in the brains of rodents. These are neurons that fire in the hippocampus in relation to specific physical locations. In this study, the researchers found that specific regions of the hippocampus fired in a specific order while the rats were navigating a maze, and then fired again in the same sequence when the animal entered REM sleep.
This early study suggests that the brain replays sequences from real life while in a dream state. As such, dreaming could be a form of after-the-fact rehearsal that helps to solidify memory and learning. Similar place cells were identified in patients with epilepsy – except this time they were connected to a virtual space in a video game. When the patients entered familiar zones in the game, the same place cells fired again.
‘Place Cells’ in Human Subjects
A new study conducted by researchers at Ohio State University and published in Proceedings of the National Academy of Science delves further into this phenomenon. In the study, young adults were given smart phones to be hung around the neck. These phones automatically took photos throughout the day.
After a month, these photos were replayed for the subjects, who were asked to conjure a vivid memory related to the scene in question. The scientists studied brain scans of the subjects whilst they viewed the photos and retrieved memories. This allowed the researchers to zero in on the area in the brain where both time and place are recorded.
Taking Memory out of the Lab
Scientists already understand that memory is episodic in nature, and that the brain organises memories in relation to one another. Two events that took place in the same relative time frame will be encoded close to one another in the physical space of the brain. Memories encoded in the location can have similar connections.
This research is promising for many reasons. It helps us better understand the episodic nature of memory and how our brains function, which will allow us to craft more effective forms of cognitive training and working memory training in the future. It also casts light on memory disorders such as Alzheimer’s, dementia and trauma-related disorders. As we discover more about how the brain creates and retains memories, we’ll become better at treating memory disorders whilst boosting memory capacity in healthy patients.