A groundbreaking new model reveals how neurons linked to spatial navigation can also store episodic memories, redefining our understanding of the neural basis of memory and cognition.
How One Brain Circuit Encodes Memories of Both Places and Events
A new computational model explains how neurons linked to spatial navigation can also help store episodic memories.
The discovery nearly five decades ago of cells within the brain’s hippocampus that store memories of specific locations has long been a subject of interest in neuroscience. These cells, known as place cells, play a crucial role in storing both spatial and episodic memories. While the mechanism behind how place cells encode spatial memory has been well-characterized, it remained a puzzle to understand how they encoded episodic memories.
According to a new model developed by MIT researchers, place cells, along with grid cells found in the entorhinal cortex, act as a scaffold that can be used to anchor memories as a linked series. This scaffold enables the storage of both spatial and episodic memories, even when there’s no spatial component involved.
The Connection Between Spatial and Episodic Memory
For a long time, researchers have been trying to understand the connection between spatial and episodic memory. Two hypotheses have been proposed to account for this overlap in function: one suggests that the circuit is specialized to store spatial memories because those types of memories are important to survival, while the other hypothesis proposes that the circuit is specialized to store episodic memories but also encodes spatial memory because location is an aspect of many episodic memories.
However, a third option proposed by MIT researchers suggests that the peculiar tiling structure of grid cells and their interactions with hippocampus are equally important for both types of memory. In this new model, the researchers hypothesized that grid cells interacting with hippocampal cells can act as a scaffold for storing either spatial or episodic memory.
How the Model Works
The model accurately replicates several features of biological memory systems, including large storage capacity, gradual degradation of older memories, and the ability to store enormous amounts of information in “memory palaces.” The researchers’ new model was able to perform tasks such as memorizing shuffled sequences of cards in card decks very well, suggesting that memory palaces take advantage of the memory circuit’s own strategy of associating inputs with a scaffold.
Future Directions
The researchers now plan to build on their model to explore how episodic memories could become converted to cortical “semantic” memory, or the memory of facts dissociated from the specific context in which they were acquired. They also aim to investigate how brain-like memory models could be integrated into modern machine learning.
This new understanding of how place cells and grid cells work together to encode both spatial and episodic memories has significant implications for our understanding of the human brain and its ability to store and recall complex information.
