Patrick Latuske, Department of Clinical Neurobiology at the Medical Faculty of Heidelberg University and German Cancer Research Center (DKFZ), Heidelberg, Germany
The superficial layers of the medial entorhinal cortex (MEC) contain a variety of spatially selective cell types that are thought to generate a metric representation of space. A prominent cell type there are grid cells that exhibit a regular, hexagonal firing pattern when an animal runs in an open environment. Anatomically, excitatory neurons in the MEC show high degree of variability ranging from stellate cells to pyramidal cells, and including several intermediate types in between. Here we investigated whether principal neurons recorded with extracellular techniques in the superficial layers of the MEC can be grouped into distinct groups based on their spike patterns at a millisecond time scale. Factor analysis of the spike-time autocorrelation revealed at least two groups, labelled bursty and non-bursty neurons, which also exhibit different spike waveforms. Bursty neurons were twice as likely to be classified as a grid cells compared to non-bursty neurons. Moreover, 70 % of the detected monosynaptic excitatory connections between principal cells and interneurons originate from bursty neurons. Together, these results suggest that bursty and non-bursty neurons form distinct neuronal populations differing in biophysical properties and network functions.