Medial entorhinal spike clusters carry more finely tuned spatial information than single spike

Abstract Many cells within the entorhinal cortex (EC) fire relatively infrequently, with the majority of their spikes separated by many hundreds of milliseconds. However, most cells are seen to occasionally fire two or more spikes in quick succession. Recent evidence has shown that, in EC grid cells, “burstier” cells; cells that fire more of their spikes in bursts, have more well defined spatial characteristics than cells that fire fewer bursts. We divide the spikes fired by single cells into single spikes and “clusters” of spikes occuring within 100ms. We show that these burst “clusters” of spikes fired by cells in MEC convey more finely tuned spatial and directional information than the numerically more common single spikes. In addition, we find that introducing environmental uncertainty decreases the ratio of clusters fired to single spikes. Most crucially, we find that single spikes are less spatially precise than clusters, and these spikes are more closely entrained to LFP theta than clusters. These findings demonstrate that clusters of spikes in EC convey more specific information about space than single spikes, may reflect “certainty” about spatial position and direction, and may represent a different firing “mode” in which intraregional communication is less relevant than interregional traffic.