Scientists Discover New System In The Brain For Forming Memories
For the longest time, scientists have always believed that the hippocampus is the main part of the brain responsible for forming memories. Now, a new study found that a brain region called entorhinal cortex plays an independent role in memory formation.
In the new study published in the journal Science, researchers at the Institute of Science and Technology Austria (IST Austria), discovered that, in mice studies, the entorhinal cortex replays memories of movements independent of input from the hippocampus.
How Are Memories Formed?
The entorhinal cortex was long dubbed as a subservient to the hippocampus. Now, it could be considered a new system for memory formation that works in parallel to the hippocampus. When people experience an event, the brains form an episodic memory, which is unique to each individual.
The hippocampus has neurons called place cells which correspond to a specific point in the surrounding physical environment. One part of the brain that reports to the hippocampus is the medial entorhinal cortex (MEC), which sends input to the hippocampus.
When a spatial memory is formed, the grid cells in the MEC act like a navigational system that provides the hippocampus with information on where, for instance, an animal is and give cues to how far or in what direction it has moved.
When a memory is recalled, the MEC has been considered just secondary to the hippocampus. Though MEC has its own cells with spatial location, its role has been underplayed, the Medical News Today reports.
The Entorhinal Cortex's Role
"Until now, the entorhinal cortex has been considered subservient to the hippocampus in both memory formation and recall. But we show that the medial entorhinal cortex can replay the firing pattern associated with moving in a maze independent of the hippocampus," Jozsef Csicsvari , lead author of the study, said as reported by Science Daily.
"The entorhinal cortex could be a new system for memory formation that works in parallel to the hippocampus," he added.
Working on rats, they recorded the neural activity of rats while they attempted to find their way out of the maze. They found that apart from the hippocampus, the MEC was also firing neurons during sleep and waking cycles. This means that these firing sequences were seen to occur independently of the hippocampus, suggesting that the MEC has a separate role.
"The hippocampus alone does not dominate how memories are formed and recalled. Instead, the entorhinal cortex and the hippocampus are probably two systems for memory formation and recall. Despite being interrelated, the two regions may work in parallel. They may recruit different pathways and play different roles in memory," Joseph O'Neill, co-author of the study, explained.