scholarly journals Shared rhythmic subcortical GABAergic input to the entorhinal cortex and presubiculum

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Tim James Viney ◽  
Minas Salib ◽  
Abhilasha Joshi ◽  
Gunes Unal ◽  
Naomi Berry ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Gamma Oscillations ◽  
Medial Septum ◽  
Theta Oscillations ◽  
Cortical Circuits ◽  
Cellular Mechanisms ◽  
Neuronal Synchrony ◽  
Theta Frequency ◽  
Episodic Memories ◽  
Gabaergic Modulation

Rhythmic theta frequency (~5–12 Hz) oscillations coordinate neuronal synchrony and higher frequency oscillations across the cortex. Spatial navigation and context-dependent episodic memories are represented in several interconnected regions including the hippocampal and entorhinal cortices, but the cellular mechanisms for their dynamic coupling remain to be defined. Using monosynaptically-restricted retrograde viral tracing in mice, we identified a subcortical GABAergic input from the medial septum that terminated in the entorhinal cortex, with collaterals innervating the dorsal presubiculum. Extracellularly recording and labeling GABAergic entorhinal-projecting neurons in awake behaving mice show that these subcortical neurons, named orchid cells, fire in long rhythmic bursts during immobility and locomotion. Orchid cells discharge near the peak of hippocampal and entorhinal theta oscillations, couple to entorhinal gamma oscillations, and target subpopulations of extra-hippocampal GABAergic interneurons. Thus, orchid cells are a specialized source of rhythmic subcortical GABAergic modulation of ‘upstream’ and ‘downstream’ cortico-cortical circuits involved in mnemonic functions.

scholarly journals Theta Modulation in the Medial and the Lateral Entorhinal Cortices

2010 ◽  
Vol 104 (2) ◽  
pp. 994-1006 ◽  
Author(s):  
Sachin S. Deshmukh ◽  
D. Yoganarasimha ◽  
Horatiu Voicu ◽  
James J. Knierim
Keyword(s):  
Entorhinal Cortex ◽  
Hippocampal Neurons ◽  
Theta Oscillations ◽  
Neural Firing ◽  
Physiological Mechanisms ◽  
Cortical Input ◽  
Theta Frequency ◽  
Temporal Encoding ◽  
Cortical Inputs ◽  
Delta Oscillations

Hippocampal neurons show a strong modulation by theta frequency oscillations. This modulation is thought to be important not only for temporal encoding and decoding of information in the hippocampal system, but also for temporal ordering of neuronal activities on timescales at which physiological mechanisms of synaptic plasticity operate. The medial entorhinal cortex (MEC), one of the two major cortical inputs to the hippocampus, is known to show theta modulation. Here, we show that the local field potentials (LFPs) in the other major cortical input to the hippocampus, the lateral entorhinal cortex (LEC), show weaker theta oscillations than those shown in the MEC. Neurons in LEC also show weaker theta modulation than that of neurons in MEC. These findings suggest that LEC inputs are integrated into hippocampal representations in a qualitatively different manner than the MEC inputs. Furthermore, MEC grid cells increase the scale of their periodic spatial firing patterns along the dorsoventral axis, corresponding to the increasing size of place fields along the septotemporal axis of the hippocampus. We show here a corresponding gradient in the tendency of MEC neural firing to skip alternate theta cycles. We propose a simple model based on interference of delta oscillations with theta oscillations to explain this behavior.

scholarly journals Cooling of medial septum reveals theta phase lag coordination of hippocampal cell assemblies

2019 ◽  
Author(s):  
Peter C. Petersen ◽  
György Buzsáki
Keyword(s):  
Spatial Navigation ◽  
Medial Septum ◽  
Neuronal Firing ◽  
Theta Oscillations ◽  
Phase Lag ◽  
Cell Assemblies ◽  
Theta Frequency ◽  
Theta Phase ◽  
Temperature Manipulation ◽  
Phase Coordination

SummaryHippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary ‘pacemaker’ timing signal is imposed on the hippocampal system or it may assist in organizing target subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to test these models. Cooling of the MS reduced both theta frequency and power, was associated with enhanced incidence of errors in a spatial navigation task but did not affect spatial correlates of neurons. MS cooling decreased theta frequency oscillations of place cells, reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. Thus, septal computation contributes not only theta pacing but is also critical for sustaining precise theta phase-coordination of cell assemblies in the hippocampus.

scholarly journals The lateral septum as a regulator of hippocampal theta oscillations and defensive behavior in rats

2015 ◽  
Vol 113 (6) ◽  
pp. 1831-1841 ◽  
Author(s):  
San-San A. Chee ◽  
Janet L. Menard ◽  
Hans C. Dringenberg
Keyword(s):  
Medial Septum ◽  
Theta Activity ◽  
Lateral Septum ◽  
Theta Oscillations ◽  
Gating Mechanism ◽  
Plus Maze ◽  
Theta Frequency ◽  
Hippocampal Theta ◽  
Precise Role

Hippocampal theta oscillations are linked to various processes, including locomotion, learning and memory, and defense and affect. The lateral septum (LS) has been implicated in the generation of the hippocampal theta rhythm, but its precise role in this process is not well understood. Here, we investigated the effects of direct pharmacological inhibition or disinhibition of the dorsal LS (dLS) on the frequency of hippocampal theta activity elicited by stimulation of the reticular formation in urethane-anesthetized rats. We found that bilateral infusions of the GABAA receptor agonist muscimol into the dLS significantly increased theta frequency. Strikingly, intra-dLS infusions of the GABAA receptor antagonist GABAzine largely abolished reticularly elicited theta activity. We also locally injected these same compounds into the medial septum (MS) to test for neuroanatomical specificity. In contrast to the effects seen in the dLS, intra-MS infusions of muscimol had no effect on theta frequency, whereas intra-MS infusions of GABAzine increased theta frequency. Given the hypothesized role of hippocampal theta in behavioral defense, we also examined the effects of intra-dLS application of muscimol in two models of anxiety, the elevated plus maze and the novelty-induced suppression of feeding paradigm; both tests revealed clear, anxiolytic-like effects following muscimol infusions. The fact that dLS-muscimol increased theta frequency while also reducing anxiety-like behaviors challenges the influential theta suppression model of anxiolysis, which predicts a slowing of theta with anxiolytic compounds. More importantly, the experiments reveal a novel role of the LS, especially its dorsal aspects, as an important gating mechanism for the expression of theta oscillations in the rodent hippocampus.

Pacemaker Neurons for the Theta Rhythm and Their Synchronization in the Septohippocampal Reciprocal Loop

2002 ◽  
Vol 87 (2) ◽  
pp. 889-900 ◽  
Author(s):  
Xiao-Jing Wang
Keyword(s):  
Theta Rhythm ◽  
Medial Septum ◽  
Theta Oscillations ◽  
Biophysical Modeling ◽  
Cellular Mechanisms ◽  
Brain Rhythm ◽  
Network Simulations ◽  
Low Threshold ◽  
Inhibitory Circuit ◽  
Hippocampal Theta

Hippocampal theta (4–10 Hz) oscillation represents a well-known brain rhythm implicated in spatial cognition and memory processes. Its cellular mechanisms remain a matter of debate, and previous computational work has focused mostly on mechanisms intrinsic to the hippocampus. On the other hand, experimental data indicate that GABAergic cells in the medial septum play a pacemaker role for the theta rhythm. We have used biophysical modeling to address two major questions raised by the septal pacemaker hypothesis: what is the ion channel mechanism for the single-cell pacemaker behavior and how do these cells become synchronized? Our model predicts that theta oscillations of septal GABAergic cells depend critically on a low-threshold, slowly inactivating potassium current. Network simulations show that theta oscillations are not coherent in an isolated population of pacemaker cells. Robust synchronization emerges with the addition of a second GABAergic cell population. Such a reciprocally inhibitory circuit can be realized by the hippocampo-septal feedback loop.

scholarly journals P2-071: IMPAIRED IN VIVO GAMMA OSCILLATIONS IN THE MEDIAL ENTORHINAL CORTEX OF KNOCK-IN ALZHEIMER MODEL

2019 ◽  
Vol 15 ◽  
pp. P598-P598
Author(s):  
Heechul Jun ◽  
Shogo Soma ◽  
Ananya Dasgupta ◽  
Kei Igarashi
Keyword(s):  
Entorhinal Cortex ◽  
Gamma Oscillations ◽  
Medial Entorhinal Cortex

scholarly journals Flexible theta sequence compression mediated via phase precessing interneurons

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Angus Chadwick ◽  
Mark CW van Rossum ◽  
Matthew F Nolan
Keyword(s):  
Action Potentials ◽  
High Capacity ◽  
Theta Oscillations ◽  
Sequence Generation ◽  
Spike Sequences ◽  
Theta Frequency ◽  
Neural Substrate ◽  
Hippocampal Theta ◽  
Novel Model ◽  
Sequence Compression

Encoding of behavioral episodes as spike sequences during hippocampal theta oscillations provides a neural substrate for computations on events extended across time and space. However, the mechanisms underlying the numerous and diverse experimentally observed properties of theta sequences remain poorly understood. Here we account for theta sequences using a novel model constrained by the septo-hippocampal circuitry. We show that when spontaneously active interneurons integrate spatial signals and theta frequency pacemaker inputs, they generate phase precessing action potentials that can coordinate theta sequences in place cell populations. We reveal novel constraints on sequence generation, predict cellular properties and neural dynamics that characterize sequence compression, identify circuit organization principles for high capacity sequential representation, and show that theta sequences can be used as substrates for association of conditioned stimuli with recent and upcoming events. Our results suggest mechanisms for flexible sequence compression that are suited to associative learning across an animal’s lifespan.

scholarly journals Optogenetic activation of SST-positive interneurons restores hippocampal theta oscillation impairment induced by soluble amyloid beta oligomersin vivo

2018 ◽  
Author(s):  
Hyowon Chung ◽  
Kyerl Park ◽  
Hyun Jae Jang ◽  
Michael M Kohl ◽  
Jeehyun Kwag
Keyword(s):  
Learning And Memory ◽  
Peak Power ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Field Potential ◽  
Theta Oscillations ◽  
Ca1 Pyramidal Neurons ◽  
Theta Frequency ◽  
Hippocampal Theta

AbstractAbnormal accumulation of amyloid β oligomers (AβO) is a hallmark of Alzheimer’s disease (AD), which leads to learning and memory deficits. Hippocampal theta oscillations that are critical in spatial navigation, learning and memory are impaired in AD. Since GABAergic interneurons, such as somatostatin-positive (SST+) and parvalbumin-positive (PV+) interneurons, are believed to play key roles in the hippocampal oscillogenesis, we asked whether AβO selectively impairs these SST+ and PV+ interneurons. To selectively manipulate SST+ or PV+ interneuron activity in mice with AβO pathologyin vivo, we co-injected AβO and adeno-associated virus (AAV) for expressing floxed channelrhodopsin-2 (ChR2) into the hippocampus of SST-Cre or PV-Cre mice. Local field potential (LFP) recordingsin vivoin these AβO–injected mice showed a reduction in the peak power of theta oscillations and desynchronization of spikes from CA1 pyramidal neurons relative to theta oscillations compared to those in control mice. Optogenetic-activation of SST+ but not PV+ interneurons in AβO–injected mice fully restored the peak power of theta oscillations and resynchronized the theta spike phases to a level observed in control mice.In vitrowhole-cell voltage-clamp recordings in CA1 pyramidal neurons in hippocampal slices treated with AβO revealed that short-term plasticity of SST+ interneuron inhibitory inputs to CA1 pyramidal neurons at theta frequency were selectively disrupted while that of PV+ interneuron inputs were unaffected. Together, our results suggest that dysfunction in inputs from SST+ interneurons to CA1 pyramidal neurons may underlie the impairment of theta oscillations observed in AβO-injected micein vivo.Our findings identify SST+ interneurons as a target for restoring theta-frequency oscillations in early AD.

scholarly journals Thalamic theta phase alignment predicts human memory formation and anterior thalamic cross-frequency coupling

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Catherine M Sweeney-Reed ◽  
Tino Zaehle ◽  
Jürgen Voges ◽  
Friedhelm C Schmitt ◽  
Lars Buentjen ◽  
...  
Keyword(s):  
Human Memory ◽  
Gamma Oscillations ◽  
Memory Formation ◽  
Anterior Thalamic Nucleus ◽  
Memory Processing ◽  
Phase Alignment ◽  
Theta Frequency ◽  
Frequency Coupling ◽  
Theta Phase ◽  
Cross Frequency Coupling

Previously we reported electrophysiological evidence for a role for the anterior thalamic nucleus (ATN) in human memory formation (<xref ref-type="bibr" rid="bib29">Sweeney-Reed et al., 2014</xref>). Theta-gamma cross-frequency coupling (CFC) predicted successful memory formation, with the involvement of gamma oscillations suggesting memory-relevant local processing in the ATN. The importance of the theta frequency range in memory processing is well-established, and phase alignment of oscillations is considered to be necessary for synaptic plasticity. We hypothesized that theta phase alignment in the ATN would be necessary for memory encoding. Further analysis of the electrophysiological data reveal that phase alignment in the theta rhythm was greater during successful compared with unsuccessful encoding, and that this alignment was correlated with the CFC. These findings support an active processing role for the ATN during memory formation.

scholarly journals Coherent and intermittent ensemble oscillations emerge from networks of irregular spiking neurons

2016 ◽  
Vol 115 (1) ◽  
pp. 457-469 ◽  
Author(s):  
Mahmood S. Hoseini ◽  
Ralf Wessel
Keyword(s):  
Single Neuron ◽  
Experimental Studies ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Peak Frequency ◽  
Spiking Neurons ◽  
Network Activity ◽  
Cortical Circuits ◽  
Model Network ◽  
Low Rate

Local field potential (LFP) recordings from spatially distant cortical circuits reveal episodes of coherent gamma oscillations that are intermittent, and of variable peak frequency and duration. Concurrently, single neuron spiking remains largely irregular and of low rate. The underlying potential mechanisms of this emergent network activity have long been debated. Here we reproduce such intermittent ensemble oscillations in a model network, consisting of excitatory and inhibitory model neurons with the characteristics of regular-spiking (RS) pyramidal neurons, and fast-spiking (FS) and low-threshold spiking (LTS) interneurons. We find that fluctuations in the external inputs trigger reciprocally connected and irregularly spiking RS and FS neurons in episodes of ensemble oscillations, which are terminated by the recruitment of the LTS population with concurrent accumulation of inhibitory conductance in both RS and FS neurons. The model qualitatively reproduces experimentally observed phase drift, oscillation episode duration distributions, variation in the peak frequency, and the concurrent irregular single-neuron spiking at low rate. Furthermore, consistent with previous experimental studies using optogenetic manipulation, periodic activation of FS, but not RS, model neurons causes enhancement of gamma oscillations. In addition, increasing the coupling between two model networks from low to high reveals a transition from independent intermittent oscillations to coherent intermittent oscillations. In conclusion, the model network suggests biologically plausible mechanisms for the generation of episodes of coherent intermittent ensemble oscillations with irregular spiking neurons in cortical circuits.

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