A new study reveals some important information about brain cells that are involved in establishing one’s location and direction. The findings made by a group in Dartmouth College might contribute significantly in our understanding of neural mechanisms in navigation. This makes it very crucial in dealing with cases of brain damage that arise out of trauma, stroke or diseases like Alzheimer’s.
In order to successfully navigate to a destination, you need to know which direction you are currently facing and which direction to travel in. It is already known that mammals have brain cells that signal the direction that they are currently facing. The “place cells” are responsible for determining brain’s response to where you are and the “head direction cells” are responsible for steering you in a particular direction. The discovery of these two types of cells formed the basis of 2014 Physiology Nobel Prize to UCL Professor John O’Keefe. In another recent study, scientists in UCL found the role of a third type of cells present in a different area of the brain (entorhinal cortex). These cells referred to as the “grid cells” are activated at multiple places. Monitoring the location of all these active places revealed a repeating, grid-like pattern in a hexagonal array. Depending on how these grid cells fire, details of the path and distance we travelled could be revealed theoretically.
Dr. Martin Chadwick (UCL Experimental Psychology), lead author of the above study, said: “Our results provide evidence to support the idea that your internal ‘compass’ readjusts as you move through the environment. For example, if you turn left then your entorhinal region should process this to shift your facing direction and goal direction accordingly. If you get lost after taking too many turns, this may be because your brain could not keep up and failed to adjust your facing and goal directions.”
Subsequently, a new study led by Jeffrey Taube, Shawn Winter and Benjamin Clarke that appears in the journal Science Express, tried to take this discovery forward. They tried to investigate how the grid cell signal is generated. Microelectrodes were installed in the rat brain to record the activity of the cells. However, these electrodes did not interfere with spatial navigation abilities of the rat. Switching off of the brain area that contains “head direction” cells led to a disruption of the signal in the “grid cells”. However, the signal in the “place cells”, which are in a different part of the brain, was unaffected.
“These results indicate for the first time that although the grid cell signal is about places, the head direction cell information is critical for generating the grid signal,” Taube says. “These findings contribute to our understanding of the neural mechanisms underlying our abilities to successfully navigate our environment. Also, what makes this study so important is the fact that the entorhinal region is one of the first parts of the brain affected by Alzheimer’s disease. So the findings may also help to explain why people start to get lost in the early stages of the disease.
UCL Study http://bit.ly/1DQuLxC
Dartmouth study http://bit.ly/1yVZWAq