Impact of visual landmarks on the activity of grid cells and other spatially selective neurons of the medial entorhinal cortex.
The medial entorhinal cortex is populated by several types of spatially selective neurons. Their main function is to provide spatial representations that assist navigation. Among these different cell types, grid cells have been studied more intensively. It has been proposed that the activity of grid cells is controlled mainly by motion cues generated internally during movement and by geometrical information related to the shape of an environment. In this talk, I will present data showing how visual landmarks influence the activity of grid cells. We found that grid periodicity rapidly disappears when visual input is eliminated. Moreover, their firing activity appears to contain information not only about the location of the animal but also about which visual landmarks are present around the animal. We also discovered that head-direction cells of the MEC react incoherently to changes in visual landmarks. Together, our findings highlight the strong influence of visual landmarks on the firing activity of MEC neurons.