Model of gradual phase shift of theta rhythm in the rat

CA1 pyramidal cell is modeled by a linked series of passive compartments representing the soma and different parts of the dendritic tree. Intracellular postsynaptic potentials are simulated by conductance changes at one or more compartments. By assuming an infinite homogeneous extracellular medium and a particular geometrical arrangement of pyramidal cells, field potential profiles are generated from the current source-sinks of the compartments. The pyramidal cells are driven at the theta (theta)-frequency at different sites of the dendritic tree in order to simulate external driving of hippocampus by the septal cells. Inhibitory or excitatory driving at different sites gives extracellular dipole fields of different null zones and maxima. Phase reversal (180 degrees) of a dipole field generated by synchronous synaptic currents is completed within a depth of 150 micron. By driving two spatially distinct but overlapping dipole fields slightly phase-shifted (30-90 degrees) from each other, the resultant field shows a gradual phase shift of 180 degrees in over 400 micron depth and no (stationary) null zones. The latter field correspond to the theta-profiles seen in the freely moving rat. Somatic inhibition is proposed to be the synaptic process generating the theta-field potentials (named dipole I) in the urethananesthetized or curarized rat. Dipole I has amplitude maxima at the basal dendritic and the distal apical dendritic layers, with a distinct null zone and phase reversal at the apical side of the CA1 pyramidal cell layer. Rhythmic distal dendritic excitation, time-delayed to somatic inhibition, is proposed to be the additional dipole (dipole II) found in freely moving rats. The combination of dipoles I and II, phase-shifted from each other, causes the gradual theta-field phase shift. Experimental studies indicate that dipole I is atropine-sensitive and probably driven by a cholinergic septohippocampal input, whereas dipole II is atropine-resistant and may come from a pathway through both the septum and the entorhinal cortex. Variations of the phase profiles of the theta-field in freely moving rats by administration of anesthetic and cholinergic drugs and by normal changes in theta-frequency could be accounted for by the proposed model. Changes of the intracellular membrane potential, cellular firing rate, and evoked excitability at different phases of the theta-rhythm in anesthetized and freely moving rats can be predicted from the model, and they are in general agreement with the extant literature. In conclusion, theta-field is generated by a rhythmic somatic inhibition phase-shifted with a distal apical-dendritic excitation.(ABSTRACT TRUNCATED AT 400 WORDS)

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Regulation of IPSP Theta Rhythm by Muscarinic Receptors and Endocannabinoids in Hippocampus

Journal of Neurophysiology ◽

10.1152/jn.00480.2005 ◽

2005 ◽

Vol 94 (6) ◽

pp. 4290-4299 ◽

Cited By ~ 27

Author(s):

Christian G. Reich ◽

Miranda A. Karson ◽

Sergei V. Karnup ◽

Lauren M. Jones ◽

Bradley E. Alger

Keyword(s):

Pyramidal Cell ◽

Acetylcholine Receptors ◽

Theta Rhythm ◽

Pyramidal Cells ◽

Muscarinic Acetylcholine Receptors ◽

Mammalian Brain ◽

Ca1 Region ◽

Theta Frequency ◽

Hippocampal Theta ◽

Apical Dendrites

Theta rhythms are behaviorally relevant electrical oscillations in the mammalian brain, particularly the hippocampus. In many cases, theta oscillations are shaped by inhibitory postsynaptic potentials (IPSPs) that are driven by glutamatergic and/or cholinergic inputs. Here we show that hippocampal theta rhythm IPSPs induced in the CA1 region by muscarinic acetylcholine receptors independent of all glutamate receptors can be briefly interrupted by action potential–induced, retrograde endocannabinoid release. Theta IPSPs can be recorded in CA1 pyramidal cell somata surgically isolated from CA3, subiculum, and even from their own apical dendrites. These results suggest that perisomatic-targeting interneurons whose output is subject to inhibition by endocannabinoids are the likely source of theta IPSPs. Interneurons having these properties include the cholecystokinin-containing cells. Simultaneous recordings from pyramidal cell pairs reveal synchronous theta-frequency IPSPs in neighboring pyramidal cells, suggesting that these IPSPs may help entrain or modulate small groups of pyramidal cells.

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Linking minimal and detailed models of CA1 microcircuits reveals how theta rhythms emerge and how their frequencies are controlled

10.1101/2020.07.28.225557 ◽

2020 ◽

Author(s):

Alexandra P Chatzikalymniou ◽

Melisa Gumus ◽

Anton R Lunyov ◽

Scott Rich ◽

Jeremie Lefebvre ◽

...

Keyword(s):

Pyramidal Cell ◽

Theta Rhythm ◽

Computational Models ◽

Pyramidal Cells ◽

Cell Types ◽

Minimal Models ◽

Detailed Model ◽

Theta Frequency ◽

Hippocampal Theta

AbstractThe wide variety of cell types and their inherent biophysical complexities pose a challenge to our understanding of oscillatory activities produced by cellular-based computational models. This challenge stems from the high-dimensional and multi-parametric nature of these systems. To overcome this issue, we implement systematic comparisons of minimal and detailed models of CA1 microcircuits that generate intra-hippocampal theta rhythms (3-12 Hz). We leverage insights from minimal models to guide detailed model explorations and obtain a cellular perspective of theta generation. Our findings distinguish the pyramidal cells as the theta rhythm initiators and reveal that their activity is regularized by the inhibitory cell populations, supporting an ‘inhibition-based tuning’ mechanism. We find a strong correlation between the pyramidal cell input current and the resulting LFP theta frequency, establishing that the intrinsic pyramidal cell properties underpin network frequency characteristics. This work provides a cellular-based foundation from which in vivo theta activities can be explored.

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Effects of 5-HT3 Receptor Antagonism on Hippocampal Cellular Activity in the Freely Moving Rat

Journal of Neurophysiology ◽

10.1152/jn.1997.77.1.517 ◽

1997 ◽

Vol 77 (1) ◽

pp. 517-521 ◽

Cited By ~ 36

Author(s):

Jeffrey Reznic ◽

Ursula Staubli

Keyword(s):

Firing Rate ◽

Pyramidal Cells ◽

Long Term Potentiation ◽

Behavioral Activity ◽

Cellular Activity ◽

Receptor Antagonism ◽

Freely Moving Rats ◽

Average Change ◽

Freely Moving ◽

Change In Mean

Reznic, Jeffrey and Ursula Staubli. Effects of 5-HT3 receptor antagonism on hippocampal cellular activity in the freely moving rat. J. Neurophysiol. 77: 517–521, 1997. Recent physiological studies conducted in the hippocampi of freely moving rats have revealed that systemic injections of the selective serotonin-3 (5-HT3) receptor antagonist ondansetron facilitate induction of long-term potentiation (LTP), increase the frequency of the theta electroencephalogram rhythm, and enhance retention of memory in hippocampally dependent tasks. To gain insight into the cellular mechanisms underlying these observations, in the present study we examined the effects of intraperitoneal injections of ondansetron on the firing rate of CA1 interneurons and pyramidal cells in the dorsal hippocampi of freely moving rats. Mean firing rates of a substantial proportion (17 of 27) of isolated neurons were significantly different before and after ondansetron injection (500 and 1,000 μg/kg). Of the interneurons that exhibited an effect, all (11 of 11) significantly decreased their mean firing rate, with an average change of −22.4 ± 3.9% (mean ± SE) across cells. Eighty-three percent (5 of 6) of pyramidal cells showing a change in mean firing rate displayed a significant increase in activity, with an average change of 56.3 ± 25.6% across cells. Ondansetron (1.0 mg/kg ip) had no detectable effect on spontaneous behavioral activity as measured by line crossings and rearings in an open-field apparatus. The present results show that pharmacological blockade of 5-HT3 receptors causes a reduction in firing activity of a subset of CA1 hippocampal interneurons, with concomitant increases in the firing rate of pyramidal cells. These changes may be directly related to the ondansetron-induced enhancement of LTP induction and memory formation observed in previous studies.

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Pharmacology of theta phase shift in the hippocampal CA1 region of freely moving rats

Electroencephalography and Clinical Neurophysiology ◽

10.1016/0013-4694(84)90142-1 ◽

1984 ◽

Vol 58 (5) ◽

pp. 457-466 ◽

Cited By ~ 37

Author(s):

Stan Leung Lai-Wo

Keyword(s):

Phase Shift ◽

Ca1 Region ◽

Hippocampal Ca1 Region ◽

Freely Moving Rats ◽

Hippocampal Ca1 ◽

Freely Moving ◽

Theta Phase

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Oscillatory Entrainment of Thalamic Neurons by Theta Rhythm in Freely Moving Rats

Journal of Neurophysiology ◽

10.1152/jn.00771.2010 ◽

2011 ◽

Vol 105 (1) ◽

pp. 4-17 ◽

Cited By ~ 25

Author(s):

Marian Tsanov ◽

Ehsan Chah ◽

Nick Wright ◽

Seralynne D. Vann ◽

Richard Reilly ◽

...

Keyword(s):

Local Field ◽

Theta Rhythm ◽

Theta Oscillations ◽

Thalamic Nuclei ◽

Population Activity ◽

Freely Moving Rats ◽

Anterior Thalamic Nuclei ◽

Freely Moving ◽

Electrophysiological Characterization ◽

Firing Properties

The anterior thalamic nuclei are assumed to support episodic memory with anterior thalamic dysfunction a core feature of diencephalic amnesia. To date, the electrophysiological characterization of this region in behaving rodents has been restricted to the anterodorsal nucleus. Here we compared single-unit spikes with population activity in the anteroventral nucleus (AV) of freely moving rats during foraging and during naturally occurring sleep. We identified AV units that synchronize their bursting activity in the 6–11 Hz range. We show for the first time in freely moving rats that a subgroup of AV neurons is strongly entrained by theta oscillations. This feature together with their firing properties and spike shape suggests they be classified as “theta” units. To prove the selectivity of AV theta cells for theta rhythm, we compared the relation of spiking rhythmicity to local field potentials during theta and non-theta periods. The most distinguishable non-theta oscillations in rodent anterior thalamus are sleep spindles. We therefore compared the firing properties of AV units during theta and spindle periods. We found that theta and spindle oscillations differ in their spatial distribution within AV, suggesting separate cellular sources for these oscillations. While theta-bursting neurons were related to the distribution of local field theta power, spindle amplitude was independent of the theta units' position. Slow- and fast-spiking bursting units that are selectively entrained to theta rhythm comprise 23.7% of AV neurons. Our results provide a framework for electrophysiological classification of AV neurons as part of theta limbic circuitry.

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Nasal respiration is necessary for the emergence of ketamine-induced high frequency network oscillations and behavioral hyperactivity in freely moving rats

10.1101/2020.07.22.213850 ◽

2020 ◽

Author(s):

Jacek Wróbel ◽

Władysław Średniawa ◽

Gabriela Bernatowicz ◽

Jaroslaw Zygierewicz ◽

Daniel K Wójcik ◽

...

Keyword(s):

High Frequency ◽

Behavioral Activation ◽

Brain Regions ◽

Basal Respiration ◽

Oscillatory Activity ◽

High Frequency Oscillations ◽

Freely Moving Rats ◽

Theta Frequency ◽

Freely Moving ◽

Subcortical Regions

AbstractChanges in oscillatory activity are widely reported after subanesthetic ketamine, however their mechanisms of generation are unclear. Here, we tested the hypothesis that nasal respiration underlies the emergence of high-frequency oscillations (130-180 Hz, HFO) and behavioral activation after ketamine in freely moving rats. We found ketamine 20 mg/kg provoked “fast” theta sniffing in rodents which correlated with increased locomotor activity and HFO power in the OB. Bursts of ketamine-dependent HFO were coupled to “fast” theta frequency sniffing. Theta coupling of HFO bursts were also found in the prefrontal cortex and ventral striatum which, although of smaller amplitude, were in phase with OB activity. Haloperidol 1 mg/kg pretreatment prevented ketamine-dependent increases in fast sniffing and instead HFO coupling to slower basal respiration. Consistent with ketamine-dependent HFO being driven by nasal respiration, unilateral naris blockade led to an ipsilateral reduction in ketamine-dependent HFO power compared to the control side. Bilateral nares blockade reduced ketamine-induced hyperactivity and HFO power and frequency. In conclusion, nasal entrainment of ketamine-dependent HFO across cortical and subcortical regions at theta frequencies represents a mechanism of orchestrated neural activity across distinct brain regions. The dense divergent connectivity of the olfactory system serves to broadcast this HFO to limbic areas.

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Faculty Opinions recommendation of Fiberoptic system for recording dendritic calcium signals in layer 5 neocortical pyramidal cells in freely moving rats.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1090036.543224 ◽

2007 ◽

Author(s):

John Lisman

Keyword(s):

Pyramidal Cells ◽

Calcium Signals ◽

Freely Moving Rats ◽

Freely Moving

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Generation of theta rhythm in medial entorhinal cortex of freely moving rats

Brain Research ◽

10.1016/0006-8993(80)90006-2 ◽

1980 ◽

Vol 189 (1) ◽

pp. 49-66 ◽

Cited By ~ 195

Author(s):

Susan J. Mitchell ◽

James B. Ranck

Keyword(s):

Entorhinal Cortex ◽

Theta Rhythm ◽

Medial Entorhinal Cortex ◽

Freely Moving Rats ◽

Freely Moving

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Amplification and linearization of distal synaptic input to cortical pyramidal cells

Journal of Neurophysiology ◽

10.1152/jn.1994.72.6.2743 ◽

1994 ◽

Vol 72 (6) ◽

pp. 2743-2753 ◽

Cited By ~ 103

Author(s):

O. Bernander ◽

C. Koch ◽

R. J. Douglas

Keyword(s):

Pyramidal Cell ◽

Synaptic Input ◽

Striate Cortex ◽

Dendritic Tree ◽

Pyramidal Cells ◽

Synaptic Efficacy ◽

Induced Voltage ◽

Apical Tuft ◽

Voltage Dependent ◽

The Relationship

1. Computer simulations were used to study the effect of voltage-dependent calcium and potassium conductances in the apical dendritic tree of a pyramidal cell on the synaptic efficacy of apical synaptic input. The apical tuft in layers 1 and 2 is the target of feedback projections from other cortical areas. 2. The current, Isoma, flowing into the soma in response to synaptic input was used to assess synaptic efficacy. This measure takes full account of all the relevant nonlinearities in the dendrities and can be used during spiking activity. Isoma emphasizes current flowing in response to synaptic input rather than synaptically induced voltage change. This measure also permits explicit characterization of the input-output relationship of the entire neuron by computing the relationship between presynaptic input and postsynaptic output frequency. 3. Simulations were based on two models. The first was a biophysically detailed 400-compartment model of a morphologically characterized layer 5 pyramidal cell from striate cortex of an adult cat. In this model eight voltage-dependent conductances were incorporated into the somatic membrane to provide the observed firing behavior of a regular spiking cell. The second model was a highly simplified three-compartment equivalent electrical circuit. 4. If the dendritic tree is entirely passive, excitatory synaptic input of the non-N-methyl-D-aspartate (non-NMDA) type to layers 1, 2, and 3 saturate at very moderate input rates, because of the high input impedance of the apical tuft. Layers 1 and 2 together can deliver only 0.25 nA current to the soma. This modest effect is surprising in view of the important afferents that synapse on the apical tuft and is inconsistent with experimental data indicating a more powerful effect. 5. We introduced in a controlled manner a voltage-dependent potassium conductance in the apical tuft, gK, to prevent saturation of the synaptic response. This conductance was designed to linearize the relationship between presynaptic input frequency and the somatic current. We also introduced a voltage-dependent calcium conductance along the apical trunk, gCa, to amplify the apical signal, i.e., the synaptic current reaching the soma. 6. To arrive at a specific relationship between the presynaptic input rate and the somatic current delivered by the synaptic input, we derived the activation curves of gK and gCa either analytically or numerically. The resultant voltage-dependent behavior of both conductances was similar to experimentally measured activation curves.(ABSTRACT TRUNCATED AT 400 WORDS)

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