scholarly journals Mammillothalamic disconnection alters hippocampo-cortical oscillatory activity and microstructure: Implications for diencephalic amnesia

2019 ◽  
Author(s):  
CM Dillingham ◽  
MM Milczarek ◽  
JC Perry ◽  
BE Frost ◽  
GD Parker ◽  
...  
Keyword(s):  
Paradoxical Sleep ◽  
Retrosplenial Cortex ◽  
Oscillatory Activity ◽  
Memory Processes ◽  
Mammillary Bodies ◽  
State Dependent ◽  
Diencephalic Amnesia ◽  
Mammillothalamic Tract ◽  
The Impact ◽  
Regional Synchrony

AbstractDiencephalic amnesia can be as disruptive as the more commonly known temporal lobe amnesia, yet the precise contribution of diencephalic structures to memory processes remains elusive. We used discrete lesions of the mammillothalamic tract to model aspects of diencephalic amnesia and assessed the impact of these lesions on multiple measures of activity and plasticity within the hippocampus and retrosplenial cortex. Lesions of the mammillothalamic tract had widespread indirect effects on hippocampo-cortical oscillatory activity within both theta and gamma bands. Both within-region oscillatory activity and cross-regional synchrony were altered. The network changes were state-dependent, displaying different profiles during locomotion and paradoxical sleep. Consistent with the associations between oscillatory activity and plasticity, complementary analyses using several convergent approaches revealed microstructural changes, which appeared to reflect a suppression of learning-induced plasticity in lesioned animals. Together, these combined findings suggest a mechanism by which damage to the medial diencephalon can impact upon learning and memory processes, highlighting important role for the mammillary bodies in the co-ordination of hippocampo-cortical activity.

scholarly journals Hippocampus-retrosplenial cortex interaction is increased during phasic REM and contributes to memory consolidation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Gomes de Almeida-Filho ◽  
Bruna Del Vechio Koike ◽  
Francesca Billwiller ◽  
Kelly Soares Farias ◽  
Igor Rafael Praxedes de Sales ◽  
...  
Keyword(s):  
Rem Sleep ◽  
Memory Consolidation ◽  
Retrosplenial Cortex ◽  
Contextual Fear Conditioning ◽  
Oscillatory Activity ◽  
Theta Oscillation ◽  
Contextual Fear ◽  
Before And After ◽  
Freely Behaving ◽  
Phasic Rem Sleep

AbstractHippocampal (HPC) theta oscillation during post-training rapid eye movement (REM) sleep supports spatial learning. Theta also modulates neuronal and oscillatory activity in the retrosplenial cortex (RSC) during REM sleep. To investigate the relevance of theta-driven interaction between these two regions to memory consolidation, we computed the Granger causality within theta range on electrophysiological data recorded in freely behaving rats during REM sleep, both before and after contextual fear conditioning. We found a training-induced modulation of causality between HPC and RSC that was correlated with memory retrieval 24 h later. Retrieval was proportional to the change in the relative influence RSC exerted upon HPC theta oscillation. Importantly, causality peaked during theta acceleration, in synchrony with phasic REM sleep. Altogether, these results support a role for phasic REM sleep in hippocampo-cortical memory consolidation and suggest that causality modulation between RSC and HPC during REM sleep plays a functional role in that phenomenon.

scholarly journals Neuromodulation of Astrocytic K+ Clearance

2021 ◽  
Vol 22 (5) ◽  
pp. 2520
Author(s):  
Alba Bellot-Saez ◽  
Rebecca Stevenson ◽  
Orsolya Kékesi ◽  
Evgeniia Samokhina ◽  
Yuval Ben-Abu ◽  
...  
Keyword(s):  
Oscillatory Behavior ◽  
Network Activity ◽  
Oscillatory Activity ◽  
Extracellular Potassium ◽  
Uptake Mechanism ◽  
Kir Channels ◽  
Neuronal Network Activity ◽  
Clearance Process ◽  
Spatial Buffering ◽  
The Impact

Potassium homeostasis is fundamental for brain function. Therefore, effective removal of excessive K+ from the synaptic cleft during neuronal activity is paramount. Astrocytes play a key role in K+ clearance from the extracellular milieu using various mechanisms, including uptake via Kir channels and the Na+-K+ ATPase, and spatial buffering through the astrocytic gap-junction coupled network. Recently we showed that alterations in the concentrations of extracellular potassium ([K+]o) or impairments of the astrocytic clearance mechanism affect the resonance and oscillatory behavior of both the individual and networks of neurons. These results indicate that astrocytes have the potential to modulate neuronal network activity, however, the cellular effectors that may affect the astrocytic K+ clearance process are still unknown. In this study, we have investigated the impact of neuromodulators, which are known to mediate changes in network oscillatory behavior, on the astrocytic clearance process. Our results suggest that while some neuromodulators (5-HT; NA) might affect astrocytic spatial buffering via gap-junctions, others (DA; Histamine) primarily affect the uptake mechanism via Kir channels. These results suggest that neuromodulators can affect network oscillatory activity through parallel activation of both neurons and astrocytes, establishing a synergistic mechanism to maximize the synchronous network activity.

scholarly journals Anterior thalamic lesions stop synaptic plasticity in retrosplenial cortex slices: expanding the pathology of diencephalic amnesia

Brain ◽  
2009 ◽  
Vol 132 (7) ◽  
pp. 1847-1857 ◽  
Author(s):  
D. L. F. Garden ◽  
P. V. Massey ◽  
D. A. Caruana ◽  
B. Johnson ◽  
E. C. Warburton ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Retrosplenial Cortex ◽  
Diencephalic Amnesia ◽  
Thalamic Lesions ◽  
Cortex Slices

scholarly journals Hippocampal–diencephalic–cingulate networks for memory and emotion: An anatomical guide

2017 ◽  
Vol 1 ◽  
pp. 239821281772344 ◽  
Author(s):  
Emma J. Bubb ◽  
Lisa Kinnavane ◽  
John P. Aggleton
Keyword(s):  
Prefrontal Cortex ◽  
Medial Temporal Lobe ◽  
Current Knowledge ◽  
Hippocampal Formation ◽  
Retrosplenial Cortex ◽  
Thalamic Nuclei ◽  
Mammillary Bodies ◽  
Individual Site ◽  
Multi Stage ◽  
Anterior Thalamic Nuclei

This review brings together current knowledge from tract tracing studies to update and reconsider those limbic connections initially highlighted by Papez for their presumed role in emotion. These connections link hippocampal and parahippocampal regions with the mammillary bodies, the anterior thalamic nuclei, and the cingulate gyrus, all structures now strongly implicated in memory functions. An additional goal of this review is to describe the routes taken by the various connections within this network. The original descriptions of these limbic connections saw their interconnecting pathways forming a serial circuit that began and finished in the hippocampal formation. It is now clear that with the exception of the mammillary bodies, these various sites are multiply interconnected with each other, including many reciprocal connections. In addition, these same connections are topographically organised, creating further subsystems. This complex pattern of connectivity helps explain the difficulty of interpreting the functional outcome of damage to any individual site within the network. For these same reasons, Papez’s initial concept of a loop beginning and ending in the hippocampal formation needs to be seen as a much more complex system of hippocampal–diencephalic–cingulate connections. The functions of these multiple interactions might be better viewed as principally providing efferent information from the posterior medial temporal lobe. Both a subcortical diencephalic route (via the fornix) and a cortical cingulate route (via retrosplenial cortex) can be distinguished. These routes provide indirect pathways for hippocampal interactions with prefrontal cortex, with the preponderance of both sets of connections arising from the more posterior hippocampal regions. These multi-stage connections complement the direct hippocampal projections to prefrontal cortex, which principally arise from the anterior hippocampus, thereby creating longitudinal functional differences along the anterior–posterior plane of the hippocampus.

scholarly journals Anterograde and Retrograde Effects of Benzodiazepines on Memory

2006 ◽  
Vol 6 ◽  
pp. 1460-1465 ◽  
Author(s):  
Daniel Beracochea
Keyword(s):  
Memory Processes ◽  
Retrieval Processes ◽  
Retrograde Memory ◽  
The Impact

Benzodiazepines are known as “acquisition-impairing” molecules, and their effects on anterograde memory processes are well described. In contrast, the impact of benzodiazepines on retrograde memory and, more particularly, on retrieval processes, is only marginally studied. This mini-review provides an overlook of the main studies evidencing an effect of benzodiazepines on retrograde memory, both in humans and animals, with special emphasis on retrieval processes. The conditions for the emergence of the benzodiazepine-induced retrieval impairments are also discussed.

scholarly journals Modeling the schizophrenias: subunit-specific NMDAR antagonism dissociates frontal δ and hippocampal θ modulation of ~140 Hz oscillations

2017 ◽  
Author(s):  
Benjamin Pittman-Polletta ◽  
Kun Hu ◽  
Bernat Kocsis
Keyword(s):  
Negative Symptoms ◽  
Paradoxical Sleep ◽  
Positive Symptom ◽  
Saline Control ◽  
Cortical Function ◽  
Specific Effects ◽  
High Frequency Oscillations ◽  
Dopaminergic Tone ◽  
Phase Amplitude ◽  
The Impact

ABSTRACTNMDAR antagonism alters mesolimbic, hippocampal, and cortical function, acutely reproducing the positive, cognitive, and negative symptoms of schizophrenia. These physiological and behavioral effects may depend differentially on NMDAR subtype-and region-specific effects. The dramatic electrophysiological signatures of NMDAR blockade in rodents include potentiated high frequency oscillations (HFOs, ~140 Hz), likely generated in mesolimbic structures, and increased HFO phase-amplitude coupling (PAC), a phenomenon related to goal-directed behavior and dopaminergic tone. This study examined the impact of subtype-specific NMDAR antagonism on HFOs and PAC. We found that positive-symptom-associated NR2A-preferring antagonism (NVP-AAM077), but not NR2B-specific antagonism (Ro25-6985) or saline control, replicated increases in HFO power seen with nonspecific antagonism (MK-801). However, PAC following NR2A-preferring antagonism was distinct from all other conditions. While θ-HFO PAC was prominent or potentiated in other conditions, NVP-AAM077 increased δ-HFO PAC and decreased θ-HFO PAC. Furthermore, active wake epochs exhibiting narrowband frontal δ oscillations, and not broadband sleep-associated δ, selectively exhibited δ-HFO coupling, while paradoxical sleep epochs having a high CA1 θ to frontal δ ratio selectively exhibited θ-HFO coupling. Our results suggest: (1) NR2A-preferring antagonism induces oscillopathies reflecting frontal hyperfunction and hippocampal hypofunction; and (2) HFO PAC indexes cortical vs. hippocampal control of mesolimbic circuits.

scholarly journals Comparable reduction in Zif268 levels and cytochrome oxidase activity in the retrosplenial cortex following mammillothalamic tract lesions

Neuroscience ◽  
2016 ◽  
Vol 330 ◽  
pp. 39-49 ◽  
Author(s):  
Aura Frizzati ◽  
Michal M. Milczarek ◽  
Frank Sengpiel ◽  
Kerrie L. Thomas ◽  
Christopher M. Dillingham ◽  
...  
Keyword(s):  
Cytochrome Oxidase ◽  
Oxidase Activity ◽  
Retrosplenial Cortex ◽  
Cytochrome Oxidase Activity ◽  
Mammillothalamic Tract

scholarly journals Multimodel Future Projections of Wintertime North Atlantic and North Pacific Tropospheric Jets: A Bayesian Analysis

2018 ◽  
Vol 31 (6) ◽  
pp. 2533-2545 ◽  
Author(s):  
D. Whittleston ◽  
K. A. McColl ◽  
D. Entekhabi
Keyword(s):  
Greenhouse Gas ◽  
North Atlantic ◽  
North Pacific ◽  
Current Model ◽  
Systematic Bias ◽  
Weighting Method ◽  
The North ◽  
State Dependent ◽  
The North Atlantic ◽  
The Impact

The impact of future greenhouse gas forcing on the North Atlantic and North Pacific tropospheric jets remains uncertain. Opposing changes in the latitudinal temperature gradient—forced by amplified lower-atmospheric Arctic warming versus upper-atmospheric tropical warming—make robust predictions a challenge. Despite some models simulating more realistic jets than others, it remains the prevailing approach to treat each model as equally probable (i.e., democratic weighting). This study compares democratically weighted projections to an alternative Bayesian-weighting method based on the ability of models to simulate historical wintertime jet climatology. The novel Bayesian technique is developed to be broadly applicable to high-dimensional fields. Results show the Bayesian weighting can reduce systematic bias and suggest the wintertime jet response to greenhouse gas forcing is largely independent of this historical bias (i.e., not state dependent). A future strengthening and narrowing is seen in both winter jets, particularly at the upper levels. The widely reported poleward shift at the level of the eddy-driven jet does not appear statistically robust, particularly over the North Atlantic, indicating sensitivity to current model deficiencies.

scholarly journals A Bayesian Approach for Inferring the Impact of a Discrete Character on Rates of Continuous-Character Evolution in the Presence of Background-Rate Variation

2019 ◽  
Vol 69 (3) ◽  
pp. 530-544 ◽  
Author(s):  
Michael R May ◽  
Brian R Moore
Keyword(s):  
Bayesian Approach ◽  
Null Model ◽  
Character Evolution ◽  
Rate Variation ◽  
Background Rate ◽  
Dependent Rate ◽  
State Dependent ◽  
Discrete Character ◽  
The Impact ◽  
Continuous Character

Abstract Understanding how and why rates of character evolution vary across the Tree of Life is central to many evolutionary questions; for example, does the trophic apparatus (a set of continuous characters) evolve at a higher rate in fish lineages that dwell in reef versus nonreef habitats (a discrete character)? Existing approaches for inferring the relationship between a discrete character and rates of continuous-character evolution rely on comparing a null model (in which rates of continuous-character evolution are constant across lineages) to an alternative model (in which rates of continuous-character evolution depend on the state of the discrete character under consideration). However, these approaches are susceptible to a “straw-man” effect: the influence of the discrete character is inflated because the null model is extremely unrealistic. Here, we describe MuSSCRat, a Bayesian approach for inferring the impact of a discrete trait on rates of continuous-character evolution in the presence of alternative sources of rate variation (“background-rate variation”). We demonstrate by simulation that our method is able to reliably infer the degree of state-dependent rate variation, and show that ignoring background-rate variation leads to biased inferences regarding the degree of state-dependent rate variation in grunts (the fish group Haemulidae). [Bayesian phylogenetic comparative methods; continuous-character evolution; data augmentation; discrete-character evolution.]

scholarly journals Dynamic Analysis of a Two-Language Competitive Model with Control Strategies

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Lin-Fei Nie ◽  
Zhi-Dong Teng ◽  
Juan J. Nieto ◽  
Il Hyo Jung
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Numerical Simulations ◽  
Control Strategy ◽  
Sufficient Conditions ◽  
Positive Order ◽  
State Dependent ◽  
Competitive Model ◽  
The Impact

The dynamic behavior of a two-language competitive model is analyzed systemically in this paper. By the linearization and the Bendixson-Dulac theorem on dynamical system, some sufficient conditions on the globally asymptotical stability of the trivial equilibria and the existence and the stability of the positive equilibrium of this model are presented. Nextly, in order to protect the endangered language, an optimal control problem relative to this model is explored. We derive some necessary conditions to solve the optimal control problem and present some numerical simulations using a Runge-Kutta fourth-order method. Finally, the languages competitive model is extended to this model assessing the impact of state-dependent pulse control strategy. Using the Poincaré map, differential inequality, and method of qualitative analysis, we prove the existence and stability of positive order-1 periodic solution for this control model. Numerical simulations are carried out to illustrate the main results and the feasibility of state-dependent impulsive control strategy.

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