Cell in the entorhinal cortex (Credit:Journal of Neuroscience )
By Tushna Commissariat
Last week I wrote about physicists in Europe who have developed a model to better understand the neuron activity in the brain that occurs when we listen to music. Their simulations suggest that certain notes sound harmonious because of the consistent rhythmic firing of neurons in the auditory system. They quantified this effect by showing that neural signals are regularly spaced for frequencies that are pleasant sounding, but are erratic for those that are not. The same researchers also said that their model may also provide insights into other senses, such as vision, that employ similar neural processing systems. Hot on the heels of that statement, this week I came across a paper in the Journal of Neuroscience discussing how neurons work to “code position in space” – simply put, the team looked at what mental processes occur while your brain perceives the space you are in and helps you to navigate within it.
Motoharu Yoshida and colleagues at Boston University in the US investigated how the rhythmic activity of nerve cells supports spatial navigation. The scientists showed that cells in the entorhinal cortex – which is located in the medial temporal lobe of the brain and acts as the main interface between the hippocampus and neocortex, playing an essential role in episodic and spatial memory formation – oscillate with individual frequencies, with the frequencies depending upon the positions of the cells within that cortex. Until now, it was believed that the frequency was modulated by the interaction with neurons in other brain regions, but in the light of these new data, this may be incorrect.
“The brain seems to represent the environment like a map with perfect distances and angles” explains Yoshida. “However, we are not robots with GPS in our head. But the rhythmic activity of the neurons in the entorhinal cortex seems to create a kind of map.” The activity of individual neurons in this region of the brain represents different positions in space, according to the researchers. The rhythmic activity of each cell may enable us to code a set of positions, forming a regular grid in the brain. Researching the capacity that most animals and mammals have for spatial navigation is always of interest, as a through understanding of it could lead to a clear picture of how our brains function in general.