Voltage dependence of subthreshold resonance frequency in layer II of medial entorhinal cortex

Center for Memory and Brain, Department of Psychology, Graduate Program for Neuroscience, Boston University, Boston, Massachusetts 02215, USA.
Hippocampus (Impact Factor: 4.16). 08/2012; 22(8):1733-49. DOI: 10.1002/hipo.22008
Source: PubMed


The resonance properties of individual neurons in entorhinal cortex (EC) may contribute to their functional properties in awake, behaving rats. Models propose that entorhinal grid cells could arise from shifts in the intrinsic frequency of neurons caused by changes in membrane potential owing to depolarizing input from neurons coding velocity. To test for potential changes in intrinsic frequency, we measured the resonance properties of neurons at different membrane potentials in neurons in medial and lateral EC. In medial entorhinal neurons, the resonant frequency of individual neurons decreased in a linear manner as the membrane potential was depolarized between -70 and -55 mV. At more hyperpolarized membrane potentials, cells asymptotically approached a maximum resonance frequency. Consistent with the previous studies, near resting potential, the cells of the medial EC possessed a decreasing gradient of resonance frequency along the dorsal to ventral axis, and cells of the lateral EC lacked resonant properties, regardless of membrane potential or position along the medial to lateral axis within lateral EC. Application of 10 μM ZD7288, the H-channel blocker, abolished all resonant properties in MEC cells, and resulted in physiological properties very similar to lateral EC cells. These results on resonant properties show a clear change in frequency response with depolarization that could contribute to the generation of grid cell firing properties in the medial EC.

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Available from: Christopher F Shay
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    • "Unlike other currents, such as I KA (Migliore et al., 2005), but consistent with previous experimental data on AP backpropagation in hippocampal CA1 PCs (Magee, 1998), increasing I h distribution with the distance from the soma only moderately affected back propagation of PIRS (Fig. 6C). We then asked if the intrinsic differences in SC neuronal morphologies (Garden et al., 2008) or I h kinetic properties (Shay et al., 2012) recorded experimentally along the DV axis of the mEC were responsible for the DV gradient observed in PIRS delay (Fig. 5B top left panel). Neuronal morphology and I h properties played a compensatory effect in regulating the PIRS delay, with the I h effect more closely resembling the experimental trend (SupplementaryFig. "
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    • "By tuning the a parameter in Eq. 6, we were able to produce cells with differential resonance frequencies at both depolarized membrane potentials (a2,b2) and near a cell's resting membrane potential (a3, b3). Similar to previous data, (Shay et al., 2012; Erchova et al., 2004) model cells showed decreased resonance frequencies with depolarization. In addition, Izhikevich neurons responded to square wave hyperpolarizing currents with a prominent sag potential, and fired rebound spikes upon release from the step current (c). "
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    • "The stellate cells in layer II of the medial entorhinal cortex have long been noted for their oscillatory character (Erchova et al., 2004) consisting of membrane potential oscillations (MPOs) and resonance properties (Engel et al., 2008; Giocomo and Hasselmo, 2008; Pastoll et al., 2012; Shay et al., 2012). More recently, it has been suggested that these cells participate in the grid-like firing fields with regard to an animals position in space. "
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