Have I been here before? Almost everyone around the world confesses they have felt it at least once in their lives.
How does the brain accomplish this feat, especially when exploring the world?
A new study could answer the question. Recent research by Dartmouth College reveals that where memories of familiar places are stored in the brain.
Scientists discovered three brain regions in the posterior cerebral cortex that form a link between the brain’s perceptual and memory systems. Scientists dubbed these regions as place-memory areas.
Lead author Adam Steel, a Neukom Fellow with the department of psychology and brain sciences in the Robertson Lab at Dartmouth, said, “As we navigate our surroundings, information enters the visual cortex and somehow ends up as knowledge of where we are — the question is where this transformation into spatial knowledge occurs. We think that the place-memory areas might be where this happens. When you look at the brain areas that process visual scenes and those that process spatial memories, these place-memory areas form a bridge between the two systems. Each of the brain areas involved in visual processing is paired with a place-memory counterpart.”
During the study, participants were asked to recall the places they had been in reality. While recalling, fMRI was performed, which produced high-resolution, subject-specific maps of brain activity.
By mapping the brain activity of individual participants using real-world places that they had been to, scientists could untangle the brain’s fine-grained organization.
In one experiment, scientists give a list to participants. The list includes the people that they knew personally and places they have visited in real life. Then, while in the fMRI scanner, the participants imagined seeing those people or visiting those places. Comparing the brain activity between people and places revealed the place-memory areas.
When scientists compared these newly identified regions to the brain areas that process visual scenes, the new regions were overlapping but distinct.
This was surprising for scientists as the classic understanding is that the brain areas that perceive should be the same areas engaged during memory recall.
In the second experiment, scientists determined whether the place-memory areas were involved in recognition of familiar places. During fMRI scanning, participants were presented with panning images of familiar and unfamiliar real-world locations downloaded from Google Street View.
Scientists then observed the neural activity and found that the place-memory areas were more active when images of familiar places were shown. The scene-perception regions did not show the same enhancement when viewing familiar places. This suggests that the place-memory areas play an essential role in recognizing familiar locations.
Steel said, “Our findings help explain how a generic image of a clock tower becomes one that we recognize, such as Baker-Berry Library’s tower here on Dartmouth’s campus.”
Senior author Caroline Robertson, an assistant professor of psychological and brain sciences at Dartmouth, said, “It’s thrilling to discover a new set of brain areas. Learning how the mind is organized is at the heart of the quest of understanding what makes us human.”
“The place-memory network provides a new framework for understanding the neural processes that drive memory-guided visual behaviors, including navigation.”
- Adam Steel, Madeleine M. Billings, Edward H. Silson, Caroline E. Robertson. A network linking scene perception and spatial memory systems in posterior cerebral cortex. Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-22848-z