Have you ever bumped into the wall while feeling around, trying to find the bathroom door in the middle of the night? If so, it was probably your “place” cells miscommunicating with your “head direction” cells, deep in the tissues of your brain.
In the hippocampus – a region buried deep within your brain – neurons that respond as place cells are on high alert, firing constantly as an animal explores its environment, says senior cognitive science major Ashlesha Dhuri ’16 (CLAS) . These cells communicate with the head direction cells and act as a compass, learning and memorizing details of the environment to aid in navigation.
Dhuri has been exploring this relationship for her honor’s thesis in the laboratory of Professor of Psychological Sciences Etan Markus. Her work not only forms a baseline for understanding how animals navigate their environment, but could have future implications for understanding memory and Alzheimer’s disease.
The Markus lab focuses on memory task experiments in rats to study aging, memory encoding, neural network representation, and competition between brain systems. Dhuri’s experiments involve observing how rats navigate different environments.
Since rats are nocturnal, they should be able to navigate well in the dark, says Dhuri.
“Their place cells and head direction cells should still continue to fire reliably,” she says, even when it is pitch dark.
The experiment consisted of giving groups of rats 60 seconds to find an escape platform in a water maze. Some rats had regular room lights on to help them find their way, while others had to navigate in the dark, with only a white noise machine to help orient them to their surroundings.
Dhuri and her partner, senior physiology and neurobiology major Sarthak Patel ’16 (CLAS), then reversed the experiment: The “dark” rats learned the maze in the light and the “light” rats learned the maze in the dark.
The experiment revealed that while the rats learned faster with visual cues, they were still able to find their way out in the dark, says Dhuri. So in the complete absence of visual information, rats are still able to learn a spatial navigation task.
Researching different areas of the brain is essential to discovering more about how humans learn and form memories, says Dhuri. The more researchers know about how the brain operates, she says, then the closer humans will be to finding a cure for degenerative brain diseases, like Alzheimer’s disease.
The hippocampus is one of the areas of the brain most affected in Alzheimer’s patients, so understanding better how this part of the brain learns and forms memories will help form a baseline for studies of the disease. When humans age, there is change in the hippocampus that affects the aging process, Dhuri says, and that change in structure of the hippocampus can lead to Alzheimer’s.
In October of 2015, Dhuri attended the Society for Neuroscience Conference in Chicago, the largest conference for brain studies in the world. She says that despite being one of the few undergraduates in attendance, she received great feedback on her work and ideas for future experiments.
One idea, she says, is to use injected drugs to deactivate different parts of the rats’ brains and repeat the water maze experiment, to help understand what different brain areas affect performance.
Dhuri hopes to attend graduate school to become a primary physician and to continue learning about details of memory and cognition.
“The more you learn about the brain through research, the more you can understand about what functions map to which structures. It’s a matter of coding,” says Dhuri. “And the more you know now, the more you’ll understand for future research.”
By: Reid DiRenzo, College of Liberal Arts and Sciences