scholarly journals Grid cell firing may arise from interference of theta frequency membrane potential oscillations in single neurons

Hippocampus ◽  
2007 ◽  
Vol 17 (12) ◽  
pp. 1252-1271 ◽  
Author(s):  
Michael E. Hasselmo ◽  
Lisa M. Giocomo ◽  
Eric A. Zilli
Keyword(s):  
Membrane Potential ◽  
Grid Cell ◽  
Single Neurons ◽  
Potential Oscillations ◽  
Theta Frequency ◽  
Cell Firing ◽  
Membrane Potential Oscillations

scholarly journals Linking Cellular Mechanisms to Behavior: Entorhinal Persistent Spiking and Membrane Potential Oscillations May Underlie Path Integration, Grid Cell Firing, and Episodic Memory

2008 ◽  
Vol 2008 ◽  
pp. 1-12 ◽  
Author(s):  
Michael E. Hasselmo ◽  
Mark P. Brandon
Keyword(s):  
Membrane Potential ◽  
Episodic Memory ◽  
Entorhinal Cortex ◽  
Path Integration ◽  
Grid Cell ◽  
Physiological Data ◽  
Cellular Mechanisms ◽  
Potential Oscillations ◽  
Cell Firing ◽  
Membrane Potential Oscillations

The entorhinal cortex plays an important role in spatial memory and episodic memory functions. These functions may result from cellular mechanisms for integration of the afferent input to entorhinal cortex. This article reviews physiological data on persistent spiking and membrane potential oscillations in entorhinal cortex then presents models showing how both these cellular mechanisms could contribute to properties observed during unit recording, including grid cell firing, and how they could underlie behavioural functions including path integration. The interaction of oscillations and persistent firing could contribute to encoding and retrieval of trajectories through space and time as a mechanism relevant to episodic memory.

Intrinsic Theta-Frequency Membrane Potential Oscillations in Hippocampal CA1 Interneurons of Stratum Lacunosum-Moleculare

1999 ◽  
Vol 81 (3) ◽  
pp. 1296-1307 ◽  
Author(s):  
C. Andrew Chapman ◽  
Jean-Claude Lacaille
Keyword(s):  
Membrane Potential ◽  
Hippocampal Slices ◽  
Stratum Radiatum ◽  
Potential Oscillations ◽  
Spike Threshold ◽  
Hippocampal Ca1 ◽  
Theta Frequency ◽  
Stratum Lacunosum Moleculare ◽  
Membrane Potential Oscillations

Intrinsic theta-frequency membrane potential oscillations in hippocampal CA1 interneurons of stratum lacunosum-moleculare. The ionic conductances underlying membrane potential oscillations of hippocampal CA1 interneurons located near the border between stratum lacunosum-moleculare and stratum radiatum (LM) were investigated using whole cell current-clamp recordings in rat hippocampal slices. At 22°C, when LM cells were depolarized near spike threshold by current injection, 91% of cells displayed 2–5 Hz oscillations in membrane potential, which caused rhythmic firing. At 32°C, mean oscillation frequency increased to 7.1 Hz. Oscillations were voltage dependent and were eliminated by hyperpolarizing cells 6–10 mV below spike threshold. Blockade of ionotropic glutamate and GABA synaptic transmission did not affect oscillations, indicating that they were not synaptically driven. Oscillations were eliminated by tetrodotoxin, suggesting that Na+ currents generate the depolarizing phase of oscillations. Oscillations were not affected by blocking Ca2+ currents with Cd2+ or Ca2+-free ACSF or by blocking the hyperpolarization-activated current ( I h) with Cs+. Both Ba2+ and a low concentration of 4-aminopyridine (4-AP) reduced oscillations but TEA did not. Theta-frequency oscillations were much less common in interneurons located in stratum oriens. Intrinsic membrane potential oscillations in LM cells of the CA1 region thus involve an interplay between inward Na+ currents and outward K+ currents sensitive to Ba2+ and 4-AP. These oscillations may participate in rhythmic inhibition and synchronization of pyramidal neurons during theta activity in vivo.

scholarly journals Conductances Mediating Intrinsic Theta-Frequency Membrane Potential Oscillations in Layer II Parasubicular Neurons

2008 ◽  
Vol 100 (5) ◽  
pp. 2746-2756 ◽  
Author(s):  
Stephen D. Glasgow ◽  
C. Andrew Chapman
Keyword(s):  
Membrane Potential ◽  
Network Activity ◽  
Potential Oscillations ◽  
Cationic Current ◽  
Artificial Cerebrospinal Fluid ◽  
Theta Frequency ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Cell Current ◽  
Membrane Potential Oscillations

Ionic conductances that generate membrane potential oscillations in neurons of layer II of the parasubiculum were studied using whole cell current-clamp recordings in horizontal slices from the rat brain. Blockade of ionotropic glutamate and GABA synaptic transmission did not reduce the power of the oscillations, indicating that oscillations are not dependent on synaptic inputs. Oscillations were eliminated when cells were hyperpolarized 6–10 mV below spike threshold, indicating that they are mediated by voltage-dependent conductances. Application of TTX completely eliminated oscillations, suggesting that Na+ currents are required for the generation of the oscillations. Oscillations were not reduced by blocking Ca2+ currents with Cd2+ or Ca2+-free artificial cerebrospinal fluid, or by blocking K+ conductances with either 50 μM or 5 mM 4-aminopyridine (4-AP), 30 mM tetraethylammonium (TEA), or Ba2+(1–2 mM). Oscillations also persisted during blockade of the muscarinic-dependent K+ current, IM, using the selective antagonist XE-991 (10 μM). However, oscillations were significantly attenuated by blocking the hyperpolarization-activated cationic current Ih with Cs+ and were almost completely blocked by the more potent Ih blocker ZD7288 (100 μM). Intrinsic membrane potential oscillations in neurons of layer II of the parasubiculum are therefore likely driven by an interaction between an inward persistent Na+ current and time-dependent deactivation of Ih. These voltage-dependent conductances provide a mechanism for the generation of membrane potential oscillations that can help support rhythmic network activity within the parasubiculum during theta-related behaviors.

Local Generation of Theta-Frequency EEG Activity in the Parasubiculum

2007 ◽  
Vol 97 (6) ◽  
pp. 3868-3879 ◽  
Author(s):  
Stephen D. Glasgow ◽  
C. Andrew Chapman
Keyword(s):  
Membrane Potential ◽  
Hippocampal Formation ◽  
Brain Slices ◽  
Stratum Radiatum ◽  
Potential Oscillations ◽  
Eeg Activity ◽  
Ca1 Region ◽  
Adjacent Structures ◽  
Theta Frequency ◽  
Membrane Potential Oscillations

The parasubiculum is a major component of the hippocampal formation that receives inputs from the CA1 region, anterior thalamus, and medial septum and that projects primarily to layer II of the entorhinal cortex. Hippocampal theta-frequency (4–12 Hz) electroencephalographic (EEG) activity has been correlated with sensorimotor integration, spatial navigation, and memory functions. The present study was aimed at determining if theta is also generated locally within the parasubiculum versus volume conducted from adjacent structures. In urethan-anesthetized rats, the phase-reversal of theta activity between superficial and deep layers of the parasubiculum was demonstrated using differential recordings from movable bipolar electrodes that eliminate the influence of volume-conducted activity. Parasubicular theta was abolished by atropine, and was in phase with theta in stratum radiatum/lacunosum-moleculare of the CA1 region. Whole cell current-clamp recordings in brain slices were then used to determine if parasubicular theta may be generated in part by membrane potential oscillations in layer II neurons. Membrane potential oscillations occurred in most layer II neurons, including four putative interneurons, when cells were held at near-threshold voltages using current injection. The frequency of oscillations increased from 3.2 to 6.1 Hz when bath temperature was raised from 22 to 32°C, and oscillations persisted in the presence of blockers of fast ionotropic glutamatergic and GABAergic synaptic transmission. Oscillations are therefore likely generated by intrinsic, voltage-dependent ionic conductances. These results indicate that theta field activity is generated locally within the parasubiculum and that intrinsic membrane potential oscillations, synchronized by local inhibitory inputs, may contribute to the generation of this activity.

Modelling the interrelations between calcium oscillations and ER membrane potential oscillations

1997 ◽  
Vol 63 (2-3) ◽  
pp. 221-239 ◽  
Author(s):  
Marko Marhl ◽  
Stefan Schuster ◽  
Milan Brumen ◽  
Reinhart Heinrich
Keyword(s):  
Membrane Potential ◽  
Calcium Oscillations ◽  
Potential Oscillations ◽  
Membrane Potential Oscillations ◽  
Er Membrane

Ionic mechanisms for the subthreshold oscillations and differential electroresponsiveness of medial entorhinal cortex layer II neurons

1993 ◽  
Vol 70 (1) ◽  
pp. 144-157 ◽  
Author(s):  
R. Klink ◽  
A. Alonso
Keyword(s):  
Membrane Potential ◽  
Entorhinal Cortex ◽  
Inward Rectification ◽  
Voltage Level ◽  
Medial Entorhinal Cortex ◽  
Potential Oscillations ◽  
Subthreshold Oscillations ◽  
Outward Rectification ◽  
Ionic Mechanisms ◽  
Membrane Potential Oscillations

1. Layer II of the medial entorhinal cortex is composed of two electrophysiologically and morphologically distinct types of projection neurons: stellate cells (SCs), which are distinguished by rhythmic subthreshold oscillatory activity, and non-SCs. The ionic mechanisms underlying their differential electroresponsiveness, particularly in the subthreshold range of membrane potentials, were investigated in an "in vitro" slice preparation. 2. In both SCs and non-SCs, the apparent membrane input resistance was markedly voltage dependent, respectively decreasing or increasing at hyperpolarized or subthreshold depolarized potential levels. Thus the neurons displayed inward rectification in the hyperpolarizing and depolarizing range. 3. In the depolarizing range, inward rectification was blocked by tetrodotoxin (TTX, 1 microM) in both types of neurons and thus shown to depend on the presence of a persistent low-threshold Na+ conductance (gNap). However, in the presence of TTX, pronounced outward rectification became manifest in the subthreshold depolarizing range of membrane potentials (positive to -60 mV) in the SCs but not in the non-SCs. 4. The rhythmic subthreshold membrane potential oscillations that were present only in the SCs were abolished by TTX and not by Ca2+ conductance block with Cd2+ or Co2+. Subthreshold oscillations thus rely on the activation of voltage-gated Na+, and not Ca2+, conductances. The Ca2+ conductance block also had no effect on the subthreshold outward rectification. 5. Prominent time-dependent inward rectification in the hyperpolarizing range in the SCs persisted after Na(+)- and Ca2+ conductance block. This rectification was not affected by Ba2+ (1 mM), but was blocked by Cs+ (1-4 mM). Therefore, it is most probably generated by a hyperpolarization-activated cationic current (Q-like current). However, the Q-like current appears to play no major role in the generation of subthreshold rhythmic membrane potential oscillations, because these persisted in the presence of Cs+. 6. On the other hand, in the SCs, the fast, sustained, outward rectification that strongly developed (after Na+ conductance block) at the oscillatory voltage level was not affected by Cs+ but was blocked by Ba2+ (1 mM). Barium was also effective in blocking the subthreshold membrane potential oscillations. 7. In the non-SCs, which do not generate subthreshold rhythmic membrane potential oscillations or manifest subthreshold outward rectification in TTX, Ca2+ conductance block abolished spike repolarization and caused the development of long-lasting Na(+)-dependent plateau potentials at a high suprathreshold voltage level. At this level, where prominent delayed rectification is present, the Na+ plateaus sustained rhythmic membrane potential oscillations.(ABSTRACT TRUNCATED AT 400 WORDS)

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