Rebound spiking in layer II medial entorhinal cortex stellate cells: Possible mechanism of grid cell function

• Published in: Neurobiology of learning and memory Vol. 129; pp. 83 - 98
• Main Authors: Shay, Christopher F., Ferrante, Michele, Chapman, G. William, Hasselmo, Michael E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2016; Elsevier BV
• Subjects: Action Potentials; Animals; Cellular biology; Electric Stimulation; Entorhinal Cortex - physiology; Female; Grid Cells - physiology; h-current; Inhibition; Male; Membrane Potentials; Models, Neurological; Neural Inhibition; Neurobiology; Neurons - physiology; Oscillations; Rats; Rats, Long-Evans; Resonance; Whole-cell; MSDB; Whole-cell; sMPOs; MRL; PV; Oscillations; h-current; mEC; D/V; Resonance; Inhibition; MRA
• ISSN: 1074-7427; 1095-9564; 1095-9564
• DOI: 10.1016/j.nlm.2015.09.004

•We tested rebound spiking properties in medial entorhinal cortex stellate cells.•Hyperpolarizing inputs eliciting rebound spikes occur in a specific phase range relative to sinusoidal input current.•Rebound spikes fall between the peak and descending zero crossing of the sinusoid.•Using Izhikevich neurons, we model the rebound spiking behaviors found in vitro.•Placing model neurons in a neural network we simulate 1D spatially periodic firing. Rebound spiking properties of medial entorhinal cortex (mEC) stellate cells induced by inhibition may underlie their functional properties in awake behaving rats, including the temporal phase separation of distinct grid cells and differences in grid cell firing properties. We investigated rebound spiking properties using whole cell patch recording in entorhinal slices, holding cells near spiking threshold and delivering sinusoidal inputs, superimposed with realistic inhibitory synaptic inputs to test the capacity of cells to selectively respond to specific phases of inhibitory input. Stellate cells showed a specific phase range of hyperpolarizing inputs that elicited spiking, but non-stellate cells did not show phase specificity. In both cell types, the phase range of spiking output occurred between the peak and subsequent descending zero crossing of the sinusoid. The phases of inhibitory inputs that induced spikes shifted earlier as the baseline sinusoid frequency increased, while spiking output shifted to later phases. Increases in magnitude of the inhibitory inputs shifted the spiking output to earlier phases. Pharmacological blockade of h-current abolished the phase selectivity of hyperpolarizing inputs eliciting spikes. A network computational model using cells possessing similar rebound properties as found in vitro produces spatially periodic firing properties resembling grid cell firing when a simulated animal moves along a linear track. These results suggest that the ability of mEC stellate cells to fire rebound spikes in response to a specific range of phases of inhibition could support complex attractor dynamics that provide completion and separation to maintain spiking activity of specific grid cell populations.