Researchers at the UCL Sainsbury Wellcome Center conducted a survey to test how cells in the retrosplenial cortex of the brain encode the angular motion of the head for navigation during the day or night.
According to a study co-author and Associate Director of the Sainsbury Wellcome Center, Troy Margrie, while you sit in a moving train, objects outside move at the vehicle’s speed. In addition, they also move relative to each other.
Margie adds that the purpose of the study was to find out how the brain differentiates egocentric and heliocentric motion through internal and external information. Moreover, the study will, in the long run, help the researchers find out if individual brain cells can access self-motion and external visual motion signals.
The brain has better navigation when the light is on
Furthermore, researchers discovered that the retrosplenial cortex the direction and speed of the head using vestibular signals. The coding is more accurate when the lights are turned on.
Margrie states that visual landmarks are visible when lights are on, making it simpler to approximate the speed of your head’s movement. Inability to encode head speed lead to the loss of a sense of direction. For this reason, it is much harder to navigate when there are no lights, especially in new surroundings.
How researchers conducted the study
The team conducted the study on mice. They let the rodents move about a large space and recorded neuronal activity in each layer of the retrosplenial cortex to understand how navigation works, with or without light.
Researchers identified the angular head velocity cells, brain neurons that track the head direction and speed.
A senior research fellow and lead study author, Sepiedeh Keshavarzi, recorded the neurons when the head was fixed to allow certain motor or sensory information to be removed. The researcher looked at particular head rotations with and without visual cues against the freely moving conditions. He realized that visual information improves the speed of head motion even though vestibular signals are enough to trigger angular velocity signals of the head. The study shows that one cell can identify visual and vestibular cues.
The team plans to investigate the pathways that lead visual and vestibular information to the retrosplenial cortex and where they are relayed.
