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Spike-induced ordering: Stochastic neural spikes provide immediate adaptability to the sensorimotor system. Proc Natl Acad Sci U S A 2020; 117:12486-12496. [PMID: 32430332 PMCID: PMC7275765 DOI: 10.1073/pnas.1819707117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The functional advantages of using a stochastically spiking neural network (sSNN) instead of a nonspiking neural network (NS-NN) have remained largely unknown. We developed an architecture which enabled the parametric adjustment of the spikiness (i.e., impulsive dynamics and stochasticity) of the sSNN output and observed that stochastic spikes instantaneously induced the ordered motion of a dynamical system. We demonstrated the benefits of sSNNs using a musculoskeletal bipedal walker and, moreover, showed that the decrease in the spikiness of motor neuron output leads to a reduction in adaptability. Stochastic spikes may aid the adaptation of a biological system to sudden perturbations or environmental changes. Our architecture can easily be connected to the conventional NS-NN and may superimpose the on-site adaptability. Most biological neurons exhibit stochastic and spiking action potentials. However, the benefits of stochastic spikes versus continuous signals other than noise tolerance and energy efficiency remain largely unknown. In this study, we provide an insight into the potential roles of stochastic spikes, which may be beneficial for producing on-site adaptability in biological sensorimotor agents. We developed a platform that enables parametric modulation of the stochastic and discontinuous output of a stochastically spiking neural network (sSNN) to the rate-coded smooth output. This platform was applied to a complex musculoskeletal–neural system of a bipedal walker, and we demonstrated how stochastic spikes may help improve on-site adaptability of a bipedal walker to slippery surfaces or perturbation of random external forces. We further applied our sSNN platform to more general and simple sensorimotor agents and demonstrated four basic functions provided by an sSNN: 1) synchronization to a natural frequency, 2) amplification of the resonant motion in a natural frequency, 3) basin enlargement of the behavioral goal state, and 4) rapid complexity reduction and regular motion pattern formation. We propose that the benefits of sSNNs are not limited to musculoskeletal dynamics. Indeed, a wide range of the stability and adaptability of biological systems may arise from stochastic spiking dynamics.
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Günseli E, Aly M. Preparation for upcoming attentional states in the hippocampus and medial prefrontal cortex. eLife 2020; 9:e53191. [PMID: 32255423 PMCID: PMC7237206 DOI: 10.7554/elife.53191] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 04/07/2020] [Indexed: 12/23/2022] Open
Abstract
Goal-directed attention is usually studied by providing individuals with explicit instructions on what they should attend to. But in daily life, we often use past experiences to guide our attentional states. Given the importance of memory for predicting upcoming events, we hypothesized that memory-guided attention is supported by neural preparation for anticipated attentional states. We examined preparatory coding in the human hippocampus and mPFC, two regions that are important for memory-guided behaviors, in two tasks: one where attention was guided by memory and another in which attention was explicitly instructed. Hippocampus and mPFC exhibited higher activity for memory-guided vs. explicitly instructed attention. Furthermore, representations in both regions contained information about upcoming attentional states. In the hippocampus, this preparation was stronger for memory-guided attention, and occurred alongside stronger coupling with visual cortex during attentional guidance. These results highlight the mechanisms by which memories are used to prepare for upcoming attentional goals.
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Affiliation(s)
- Eren Günseli
- Department of Psychology, Columbia UniversityNew YorkUnited States
- Department of Psychology, Sabanci UniversityIstanbulTurkey
| | - Mariam Aly
- Department of Psychology, Columbia UniversityNew YorkUnited States
- Affiliate Member, Zuckerman Mind Brain Behavior Institute, Columbia UniversityNew YorkUnited States
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3
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Tarder-Stoll H, Jayakumar M, Dimsdale-Zucker HR, Günseli E, Aly M. Dynamic internal states shape memory retrieval. Neuropsychologia 2020; 138:107328. [DOI: 10.1016/j.neuropsychologia.2019.107328] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 12/13/2019] [Accepted: 12/22/2019] [Indexed: 12/30/2022]
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Disney AA, Higley MJ. Diverse Spatiotemporal Scales of Cholinergic Signaling in the Neocortex. J Neurosci 2020; 40:720-725. [PMID: 31969490 PMCID: PMC6975298 DOI: 10.1523/jneurosci.1306-19.2019] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/16/2019] [Accepted: 10/21/2019] [Indexed: 12/18/2022] Open
Abstract
ACh is a signaling molecule in the mammalian CNS, with well-documented influence over cognition and behavior. However, the nature of cholinergic signaling in the brain remains controversial, with ongoing debates focused on the spatial and temporal resolution of ACh activity. Generally, opposing views have embraced a dichotomy between transmission as slow and volume-mediated versus fast and synaptic. Here, we provide the perspective that ACh, like most other neurotransmitters, exhibits both fast and slow modes that are strongly determined by the anatomy of cholinergic fibers, the distribution and the signaling mechanisms of receptor subtypes, and the dynamics of ACh hydrolysis. Current methodological approaches remain limited in their ability to provide detailed analyses of these underlying factors. However, we believe that the continued development of novel technologies in combination with a more nuanced view of cholinergic activity will open critical new avenues to a better understanding of ACh in the brain.Dual Perspectives Companion Paper: Forebrain Cholinergic Signaling: Wired and Phasic, Not Tonic, and Causing Behavior, by Martin Sarter and Cindy Lustig.
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Affiliation(s)
- Anita A Disney
- Department of Neurobiology, Duke University, Durham, North Carolina 27710, and
| | - Michael J Higley
- Department of Neuroscience, Kavli Institute for Neuroscience, Yale University, New Haven, Connecticut 06520
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Sajedin A, Menhaj MB, Vahabie AH, Panzeri S, Esteky H. Cholinergic Modulation Promotes Attentional Modulation in Primary Visual Cortex- A Modeling Study. Sci Rep 2019; 9:20186. [PMID: 31882838 PMCID: PMC6934489 DOI: 10.1038/s41598-019-56608-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 12/16/2019] [Indexed: 12/30/2022] Open
Abstract
Attention greatly influences sensory neural processing by enhancing firing rates of neurons that represent the attended stimuli and by modulating their tuning properties. The cholinergic system is believed to partly mediate the attention contingent improvement of cortical processing by influencing neuronal excitability, synaptic transmission and neural network characteristics. Here, we used a biophysically based model to investigate the mechanisms by which cholinergic system influences sensory information processing in the primary visual cortex (V1) layer 4C. The physiological properties and architectures of our model were inspired by experimental data and include feed-forward input from dorsal lateral geniculate nucleus that sets up orientation preference in V1 neural responses. When including a cholinergic drive, we found significant sharpening in orientation selectivity, desynchronization of LFP gamma power and spike-field coherence, decreased response variability and correlation reduction mostly by influencing intracortical interactions and by increasing inhibitory drive. Our results indicated that these effects emerged due to changes specific to the behavior of the inhibitory neurons. The behavior of our model closely resembles the effects of attention on neural activities in monkey V1. Our model suggests precise mechanisms through which cholinergic modulation may mediate the effects of attention in the visual cortex.
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Affiliation(s)
- Atena Sajedin
- Department of Electrical Engineering, Amirkabir University of Technology, Hafez Ave., 15875-4413, Tehran, Iran
| | - Mohammad Bagher Menhaj
- Department of Electrical Engineering, Amirkabir University of Technology, Hafez Ave., 15875-4413, Tehran, Iran.
| | - Abdol-Hossein Vahabie
- School of Cognitive Sciences (SCS), Institute for Research in Fundamental Sciences (IPM), 19395-5746, Tehran, Iran
| | - Stefano Panzeri
- Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems @UniTn, Istituto Italiano di Tecnologia, 38068, Rovereto, Italy
| | - Hossein Esteky
- Research Group for Brain and Cognitive Sciences, School of Medicine, Shahid Beheshti Medical University, 19839-63113, Tehran, Iran.
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Duncan K, Semmler A, Shohamy D. Modulating the Use of Multiple Memory Systems in Value-based Decisions with Contextual Novelty. J Cogn Neurosci 2019; 31:1455-1467. [PMID: 31322467 DOI: 10.1162/jocn_a_01447] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
With multiple learning and memory systems at its disposal, the human brain can represent the past in many ways, from extracting regularities across similar experiences (incremental learning) to storing rich, idiosyncratic details of individual events (episodic memory). The unique information carried by these neurologically distinct forms of memory can bias our behavior in different directions, raising crucial questions about how these memory systems interact to guide choice and the factors that cause one to dominate. Here, we devised a new approach to estimate how decisions are independently influenced by episodic memories and incremental learning. Furthermore, we identified a biologically motivated factor that biases the use of different memory types-the detection of novelty versus familiarity. Consistent with computational models of cholinergic memory modulation, we find that choices are more influenced by episodic memories following the recognition of an unrelated familiar image but more influenced by incrementally learned values after the detection of a novel image. Together this work provides a new behavioral tool enabling the disambiguation of key memory behaviors thought to be supported by distinct neural systems while also identifying a theoretically important and broadly applicable manipulation to bias the arbitration between these two sources of memories.
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The Firing Rate Speed Code of Entorhinal Speed Cells Differs across Behaviorally Relevant Time Scales and Does Not Depend on Medial Septum Inputs. J Neurosci 2019; 39:3434-3453. [PMID: 30804092 DOI: 10.1523/jneurosci.1450-18.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 02/06/2019] [Accepted: 02/10/2019] [Indexed: 12/13/2022] Open
Abstract
The firing rate of speed cells, a dedicated subpopulation of neurons in the medial entorhinal cortex (MEC), is correlated with running speed. This correlation has been interpreted as a speed code used in various computational models for path integration. These models consider firing rate to be linearly tuned by running speed in real-time. However, estimation of firing rates requires integration of spiking events over time, setting constraints on the temporal accuracy of the proposed speed code. We therefore tested whether the proposed speed code by firing rate is accurate at short time scales using data obtained from open-field recordings in male rats and mice. We applied a novel filtering approach differentiating between speed codes at multiple time scales ranging from deciseconds to minutes. In addition, we determined the optimal integration time window for firing-rate estimation using a general likelihood framework and calculated the integration time window that maximizes the correlation between firing rate and running speed. Data show that these time windows are on the order of seconds, setting constraints on real-time speed coding by firing rate. We further show that optogenetic inhibition of either cholinergic, GABAergic, or glutamatergic neurons in the medial septum/diagonal band of Broca does not affect modulation of firing rates by running speed at each time scale tested. These results are relevant for models of path integration and for our understanding of how behavioral activity states may modulate firing rates and likely information processing in the MEC.SIGNIFICANCE STATEMENT Path integration is the most basic form of navigation relying on self-motion cues. Models of path integration use medial septum/diagonal band of Broca (MSDB)-dependent MEC grid-cell firing patterns as the neurophysiological substrate of path integration. These models use a linear speed code by firing rate, but do not consider temporal constraints of integration over time for firing-rate estimation. We show that firing-rate estimation for speed cells requires integration over seconds. Using optogenetics, we show that modulation of firing rates by running speed is independent of MSDB inputs. These results enhance our understanding of path integration mechanisms and the role of the MSDB for information processing in the MEC.
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Gu Z, Alexander GM, Dudek SM, Yakel JL. Hippocampus and Entorhinal Cortex Recruit Cholinergic and NMDA Receptors Separately to Generate Hippocampal Theta Oscillations. Cell Rep 2018; 21:3585-3595. [PMID: 29262336 DOI: 10.1016/j.celrep.2017.11.080] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 10/10/2017] [Accepted: 11/21/2017] [Indexed: 11/25/2022] Open
Abstract
Although much progress has been made in understanding type II theta rhythm generation under urethane anesthesia, less is known about the mechanisms underlying type I theta generation during active exploration. To better understand the contributions of cholinergic and NMDA receptor activation to type I theta generation, we recorded hippocampal theta oscillations from freely moving mice with local infusion of cholinergic or NMDA receptor antagonists to either the hippocampus or the entorhinal cortex (EC). We found that cholinergic receptors in the hippocampus, but not the EC, and NMDA receptors in the EC, but not the hippocampus, are critical for open-field theta generation and Y-maze performance. We further found that muscarinic M1 receptors located on pyramidal neurons, but not interneurons, are critical for cholinergic modulation of hippocampal synapses, theta generation, and Y-maze performance. These results suggest that hippocampus and EC neurons recruit cholinergic-dependent and NMDA-receptor-dependent mechanisms, respectively, to generate theta oscillations to support behavioral performance.
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Affiliation(s)
- Zhenglin Gu
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, US Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Georgia M Alexander
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, US Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Serena M Dudek
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, US Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Jerrel L Yakel
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, US Department of Health and Human Services, Research Triangle Park, NC 27709, USA.
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Duncan KD, Schlichting ML. Hippocampal representations as a function of time, subregion, and brain state. Neurobiol Learn Mem 2018. [PMID: 29535044 DOI: 10.1016/j.nlm.2018.03.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
How does the hippocampus represent interrelated experiences in memory? We review prominent yet seemingly contradictory theoretical perspectives, which propose that the hippocampus distorts experiential representations to either emphasize their distinctiveness or highlight common elements. These fundamentally different kinds of memory representations may be instantiated in the brain via conjunctive separated codes and adaptively differentiated codes on the one hand, or integrated relational codes on the other. After reviewing empirical support for these different coding schemes within the hippocampus, we outline two organizing principles which may explain the conflicting findings in the literature. First focusing on where the memories are formed and stored, we argue that distinct hippocampal regions represent experiences at multiple levels of abstraction and may transmit them to distinct cortical networks. Then focusing on when memories are formed, we identify several factors that can open and maintain specialized time windows, during which the very same hippocampal network is biased toward one coding scheme over the others. Specifically, we discuss evidence for (1) excitability-mediated integration windows, maintained by persistently elevated CREB levels following encoding of a specific memory, (2) fleeting cholinergically-mediated windows favoring memory separation, and (3) sustained dopaminergically-mediated windows favoring memory integration. By presenting a broad overview of different hippocampal coding schemes across species, we hope to inspire future empirical and modeling research to consider how factors surrounding memory formation shape the representations in which they are stored.
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Affiliation(s)
- Katherine D Duncan
- Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada.
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10
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Abstract
Why are people sometimes able to recall associations in exquisite detail while at other times left frustrated by the deficiencies of memory? Although this apparent fickleness of memory has been extensively studied by investigating factors that build strong memory traces, researchers know less about whether memory success also depends on cognitive states that are in place when a cue is encountered. Motivating this possibility, neurocomputational models propose that the hippocampus's capacity to support associative recollection (pattern completion) is biased by persistent neurochemical states, which can be elicited by exposure to familiarity and novelty. We investigated these models' behavioral implications by assessing how recent familiarity influences different memory-retrieval processes. We found that recent familiarity selectively benefitted associative memory (Experiment 1) and that this effect decayed over seconds (Experiment 2), consistent with the timescale of hippocampal neuromodulation. Thus, we show that basic memory computations can be shaped by a subtle, biologically motivated manipulation.
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Affiliation(s)
- Anuya Patil
- Department of Psychology, University of Toronto
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11
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Differences in neurochemical profiles of two gadid species under ocean warming and acidification. Front Zool 2017; 14:49. [PMID: 29093740 PMCID: PMC5661927 DOI: 10.1186/s12983-017-0238-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 10/13/2017] [Indexed: 11/24/2022] Open
Abstract
Background Exposure to future ocean acidification scenarios may alter the behaviour of marine teleosts through interference with neuroreceptor functioning. So far, most studies investigated effects of ocean acidification on the behaviour of fish, either isolated or in combination with environmental temperature. However, only few physiological studies on this issue were conducted despite the putative neurophysiological origin of the CO2-induced behavioural changes. Here, we present the metabolic consequences of long-term exposure to projected ocean acidification (396–548 μatm PCO2 under control and 915–1272 μatm under treatment conditions) and parallel warming in the brain of two related fish species, polar cod (Boreogadus saida, exposed to 0 °C, 3 °C, 6 °C and 8 °C) and Atlantic cod (Gadus morhua, exposed to 3 °C, 8 °C, 12 °C and 16 °C). It has been shown that B. saida is behaviourally vulnerable to future ocean acidification scenarios, while G. morhua demonstrates behavioural resilience. Results We found that temperature alters brain osmolyte, amino acid, choline and neurotransmitter concentrations in both species indicating thermal responses particularly in osmoregulation and membrane structure. In B. saida, changes in amino acid and osmolyte metabolism at the highest temperature tested were also affected by CO2, possibly emphasizing energetic limitations. We did not observe changes in neurotransmitters, energy metabolites, membrane components or osmolytes that might serve as a compensatory mechanism against CO2 induced behavioural impairments. In contrast to B. saida, such temperature limitation was not detected in G. morhua; however, at 8 °C, CO2 induced an increase in the levels of metabolites of the glutamate/GABA-glutamine cycle potentially indicating greater GABAergic activity in G.morhua. Further, increased availability of energy-rich substrates was detected under these conditions. Conclusions Our results indicate a change of GABAergic metabolism in the nervous system of Gadus morhua close to the optimum of the temperature range. Since a former study showed that juvenile G. morhua might be slightly more behaviourally resilient to CO2 at this respective temperature, we conclude that the observed change of GABAergic metabolism could be involved in counteracting OA induced behavioural changes. This may serve as a fitness advantage of this respective species compared to B. saida in a future warmer, more acidified polar ocean. Electronic supplementary material The online version of this article (10.1186/s12983-017-0238-5) contains supplementary material, which is available to authorized users.
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12
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Hummos A, Nair SS. An integrative model of the intrinsic hippocampal theta rhythm. PLoS One 2017; 12:e0182648. [PMID: 28787026 PMCID: PMC5546630 DOI: 10.1371/journal.pone.0182648] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/21/2017] [Indexed: 11/23/2022] Open
Abstract
Hippocampal theta oscillations (4–12 Hz) are consistently recorded during memory tasks and spatial navigation. Despite several known circuits and structures that generate hippocampal theta locally in vitro, none of them were found to be critical in vivo, and the hippocampal theta rhythm is severely attenuated by disruption of external input from medial septum or entorhinal cortex. We investigated these discrepancies that question the sufficiency and robustness of hippocampal theta generation using a biophysical spiking network model of the CA3 region of the hippocampus that included an interconnected network of pyramidal cells, inhibitory basket cells (BC) and oriens-lacunosum moleculare (OLM) cells. The model was developed by matching biological data characterizing neuronal firing patterns, synaptic dynamics, short-term synaptic plasticity, neuromodulatory inputs, and the three-dimensional organization of the hippocampus. The model generated theta power robustly through five cooperating generators: spiking oscillations of pyramidal cells, recurrent connections between them, slow-firing interneurons and pyramidal cells subnetwork, the fast-spiking interneurons and pyramidal cells subnetwork, and non-rhythmic structured external input from entorhinal cortex to CA3. We used the modeling framework to quantify the relative contributions of each of these generators to theta power, across different cholinergic states. The largest contribution to theta power was that of the divergent input from the entorhinal cortex to CA3, despite being constrained to random Poisson activity. We found that the low cholinergic states engaged the recurrent connections in generating theta activity, whereas high cholinergic states utilized the OLM-pyramidal subnetwork. These findings revealed that theta might be generated differently across cholinergic states, and demonstrated a direct link between specific theta generators and neuromodulatory states.
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Affiliation(s)
- Ali Hummos
- Department of Health Informatics, University of Missouri, Columbia, Missouri, United States of America
- Department of Psychiatry, University of Missouri, Columbia, Missouri, United States of America
| | - Satish S. Nair
- Department of Electrical & Computer Engineering, University of Missouri, Columbia, Missouri, United States of America
- * E-mail:
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Baginskas A, Kuras A. Retinal co-mediator acetylcholine evokes muscarinic inhibition of recurrent excitation in frog tectum column. Neurosci Lett 2016; 629:137-142. [PMID: 27394688 DOI: 10.1016/j.neulet.2016.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 06/27/2016] [Accepted: 07/06/2016] [Indexed: 12/13/2022]
Abstract
Acetylcholine receptors contribute to the control of neuronal and neuronal network activity from insects to humans. We have investigated the action of acetylcholine receptors in the optic tectum of Rana temporaria (common frog). Our previous studies have demonstrated that acetylcholine activates presynaptic nicotinic receptors, when released into the frog optic tectum as a co-mediator during firing of a single retinal ganglion cell, and causes: a) potentiation of retinotectal synaptic transmission, and b) facilitation of transition of the tectum column to a higher level of activity. In the present study we have shown that endogenous acetylcholine also activates muscarinic receptors, leading to a delayed inhibition of recurrent excitatory synaptic transmission in the tectum column. The delay of muscarinic inhibition was evaluated to be of ∼80ms, with an extent of inhibition of ∼2 times. The inhibition of the recurrent excitation determines transition of the tectum column back to its resting state, giving a functional sense for the inhibition.
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Affiliation(s)
- Armantas Baginskas
- Department of Physics, Mathematics and Biophysics, Medical Academy, Lithuanian University of Health Sciences, Eiveniu 4, Kaunas LT 50161, Lithuania.
| | - Antanas Kuras
- Laboratory of Neurophysiology, Neuroscience Institute, Medical Academy, Lithuanian University of Health Sciences, Eiveniu 4, Kaunas LT 50161, Lithuania
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Schomaker J, Meeter M. Short- and long-lasting consequences of novelty, deviance and surprise on brain and cognition. Neurosci Biobehav Rev 2015; 55:268-79. [DOI: 10.1016/j.neubiorev.2015.05.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/01/2015] [Accepted: 05/04/2015] [Indexed: 12/15/2022]
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Septo-hippocampal signal processing: breaking the code. PROGRESS IN BRAIN RESEARCH 2015; 219:103-20. [PMID: 26072236 DOI: 10.1016/bs.pbr.2015.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The septo-hippocampal connections appear to be a key element in the neuromodulatory cholinergic control of the hippocampal neurons. The cholinergic neuromodulation is well established in shifting behavioral states of the brain. The pacemaker role of medial septum in the limbic theta rhythm is demonstrated by lesions and pharmacological manipulations of GABAergic neurons, yet the link between the activity of different septal neuronal classes and limbic theta rhythm is not fully understood. We know even less about the information transfer between the medial septum and hippocampus--is there a particular kind of processed information that septo-hippocampal pathways transmit? This review encompasses fundamental findings together with the latest data of septo-hippocampal signal processing to tackle the frontiers of our understanding about the functional significance of medial septum to the hippocampal formation.
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A computational theory of hippocampal function, and tests of the theory: New developments. Neurosci Biobehav Rev 2015; 48:92-147. [DOI: 10.1016/j.neubiorev.2014.11.009] [Citation(s) in RCA: 226] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Revised: 10/24/2014] [Accepted: 11/12/2014] [Indexed: 01/01/2023]
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Hummos A, Franklin CC, Nair SS. Intrinsic mechanisms stabilize encoding and retrieval circuits differentially in a hippocampal network model. Hippocampus 2014; 24:1430-48. [PMID: 24978936 PMCID: PMC9121438 DOI: 10.1002/hipo.22324] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 06/13/2014] [Accepted: 06/16/2014] [Indexed: 01/09/2023]
Abstract
Acetylcholine regulates memory encoding and retrieval by inducing the hippocampus to switch between pattern separation and pattern completion modes. However, both processes can introduce significant variations in the level of network activity and potentially cause a seizure-like spread of excitation. Thus, mechanisms that keep network excitation within certain bounds are necessary to prevent such instability. We developed a biologically realistic computational model of the hippocampus to investigate potential intrinsic mechanisms that might stabilize the network dynamics during encoding and retrieval. The model was developed by matching experimental data, including neuronal behavior, synaptic current dynamics, network spatial connectivity patterns, and short-term synaptic plasticity. Furthermore, it was constrained to perform pattern completion and separation under the effects of acetylcholine. The model was then used to investigate the role of short-term synaptic depression at the recurrent synapses in CA3, and inhibition by basket cell (BC) interneurons and oriens lacunosum-moleculare (OLM) interneurons in stabilizing these processes. Results showed that when CA3 was considered in isolation, inhibition solely by BCs was not sufficient to control instability. However, both inhibition by OLM cells and short-term depression at the recurrent CA3 connections stabilized the network activity. In the larger network including the dentate gyrus, the model suggested that OLM inhibition could control the network during high cholinergic levels while depressing synapses at the recurrent CA3 connections were important during low cholinergic states. Our results demonstrate that short-term plasticity is a critical property of the network that enhances its robustness. Furthermore, simulations suggested that the low and high cholinergic states can each produce runaway excitation through unique mechanisms and different pathologies. Future studies aimed at elucidating the circuit mechanisms of epilepsy could benefit from considering the two modulatory states separately.
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Affiliation(s)
- Ali Hummos
- Department of Health Informatics, University of Missouri, Columbia, Missouri
- Department of Psychiatry, University of Missouri, Columbia, Missouri
| | - Charles C. Franklin
- Department of Electrical & Computer Engineering, University of Missouri, Columbia, Missouri
| | - Satish S. Nair
- Department of Electrical & Computer Engineering, University of Missouri, Columbia, Missouri
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Müller C, Remy S. Dendritic inhibition mediated by O-LM and bistratified interneurons in the hippocampus. Front Synaptic Neurosci 2014; 6:23. [PMID: 25324774 PMCID: PMC4179767 DOI: 10.3389/fnsyn.2014.00023] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 09/09/2014] [Indexed: 12/20/2022] Open
Abstract
In the CA1 region of the hippocampus pyramidal neurons and GABAergic interneurons form local microcircuits. CA1 interneurons are a diverse group consisting of many subtypes, some of which provide compartment-specific inhibition specifically onto pyramidal neuron dendrites. In fact, the majority of inhibitory synapses on pyramidal neurons is found on their dendrites. The specific role of a dendrite-innervating interneuron subtype is primarily determined by its innervation pattern on the distinct dendritic domains of pyramidal neurons. The efficacy of dendritic inhibition in reducing dendritic excitation depends on the relative timing and location of the activated excitatory and inhibitory synapses. In vivo, synaptic properties such as short-term plasticity and neuro-modulation by the basal forebrain, govern the degree of inhibition in distinct dendritic domains in a dynamic, behavior dependent manner, specifically during network oscillation such as the theta rhythm. In this review we focus on two subtypes of dendrite-innervating interneurons: the oriens-lacunosum moleculare (O-LM) interneuron and the bistratified interneuron. Their molecular marker profile, morphology, and function in vivo and in vitro are well studied. We strive to integrate this diverse information from the cellular to the network level, and to provide insight into how the different characteristics of O-LM and bistratified interneurons affect dendritic excitability, network activity, and behavior.
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Affiliation(s)
- Christina Müller
- Neuronal Networks Group, German Center for Neurodegenerative Diseases within the Helmholtz Association Bonn, Germany
| | - Stefan Remy
- Neuronal Networks Group, German Center for Neurodegenerative Diseases within the Helmholtz Association Bonn, Germany ; Department of Epileptology, University of Bonn Bonn, Germany
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Tiganj Z, Hasselmo ME, Howard MW. A simple biophysically plausible model for long time constants in single neurons. Hippocampus 2014; 25:27-37. [PMID: 25113022 DOI: 10.1002/hipo.22347] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 08/04/2014] [Accepted: 08/05/2014] [Indexed: 11/10/2022]
Abstract
Recent work in computational neuroscience and cognitive psychology suggests that a set of cells that decay exponentially could be used to support memory for the time at which events took place. Analytically and through simulations on a biophysical model of an individual neuron, we demonstrate that exponentially decaying firing with a range of time constants up to minutes could be implemented using a simple combination of well-known neural mechanisms. In particular, we consider firing supported by calcium-controlled cation current. When the amount of calcium leaving the cell during an interspike interval is larger than the calcium influx during a spike, the overall decay in calcium concentration can be exponential, resulting in exponential decay of the firing rate. The time constant of the decay can be several orders of magnitude larger than the time constant of calcium clearance, and it could be controlled externally via a variety of biologically plausible ways. The ability to flexibly and rapidly control time constants could enable working memory of temporal history to be generalized to other variables in computing spatial and ordinal representations.
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Affiliation(s)
- Zoran Tiganj
- Department of Psychological and Brain Sciences, Center for Memory and Brain, Boston University, Boston, Massachusetts
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20
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Rowe DL, Hermens DF. Attention-deficit/hyperactivity disorder: neurophysiology, information processing, arousal and drug development. Expert Rev Neurother 2014; 6:1721-34. [PMID: 17144785 DOI: 10.1586/14737175.6.11.1721] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this review, we draw on literature from both animal and human neurophysiological studies to consider the neurochemical mechanisms underlying attention-deficit/ hyperactivity disorder (ADHD). Psychophysiological and neuropsychological research is used to propose possible etiological endophenotypes of ADHD. These are conceptualized as patients with distinct cortical-arousal, information-processing or maturational abnormalities, or a combination thereof, and how the endophenotypes can be used to help drug development and optimize treatment and management. To illustrate, the paper focuses on neuro- and psychophysiological evidence that suggests cholinergic mechanisms may underlie specific information-processing abnormalities that occur in ADHD. The clinical implications for a cholinergic hypothesis of ADHD are considered, along with its possible implications for treatment and pharmacological development.
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Affiliation(s)
- Donald L Rowe
- The Brain Dynamics Centre and Department of Psychological Medicine, Westmead Hospital and University of Sydney, NSW, Australia.
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21
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Hasselmo ME, Stern CE. Theta rhythm and the encoding and retrieval of space and time. Neuroimage 2013; 85 Pt 2:656-66. [PMID: 23774394 DOI: 10.1016/j.neuroimage.2013.06.022] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 05/28/2013] [Accepted: 06/04/2013] [Indexed: 11/25/2022] Open
Abstract
Physiological data demonstrates theta frequency oscillations associated with memory function and spatial behavior. Modeling and data from animals provide a perspective on the functional role of theta rhythm, including correlations with behavioral performance and coding by timing of spikes relative to phase of oscillations. Data supports a theorized role of theta rhythm in setting the dynamics for encoding and retrieval within cortical circuits. Recent data also supports models showing how network and cellular theta rhythmicity allows neurons in the entorhinal cortex and hippocampus to code time and space as a possible substrate for encoding events in episodic memory. Here we discuss these models and relate them to current physiological and behavioral data.
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Affiliation(s)
- Michael E Hasselmo
- Center for Memory and Brain, Department of Psychology and Graduate Program for Neuroscience, Boston University, 2 Cummington Mall, Boston, MA, 02215, USA.
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22
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Kesner RP. A process analysis of the CA3 subregion of the hippocampus. Front Cell Neurosci 2013; 7:78. [PMID: 23750126 PMCID: PMC3664330 DOI: 10.3389/fncel.2013.00078] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/08/2013] [Indexed: 12/30/2022] Open
Abstract
From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued recall primarily for spatial information. These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the dentate gyrus (DG) via mossy fiber inputs into the CA3a,b. The CA3a,b is also important for encoding of spatial information requiring the acquisition of arbitrary and relational associations. All these tasks are assumed to operate within an autoassociative network function of the CA3 region. The CA3a,b also supports retrieval of short-term memory information based on a spatial pattern completion process. Based on afferent inputs into CA3a,b from the DG via mossy fibers and afferents from the entorhinal cortex into CA3a,b as well as reciprocal connections with the septum, CA3a,b can bias the process of encoding utilizing the operation of spatial pattern separation and the process of retrieval utilizing the operation of pattern completion. The CA3a,b also supports sequential processing of information in cooperation with CA1 based on the Schaffer collateral output from CA3a,b to CA1. The CA3c function is in part based on modulation of the DG in supporting pattern separation processes.
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Affiliation(s)
- Raymond P Kesner
- Department of Psychology, University of Utah Salt Lake City, UT, USA
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23
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Hirel J, Gaussier P, Quoy M, Banquet JP, Save E, Poucet B. The hippocampo-cortical loop: spatio-temporal learning and goal-oriented planning in navigation. Neural Netw 2013; 43:8-21. [PMID: 23500496 DOI: 10.1016/j.neunet.2013.01.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 01/30/2013] [Accepted: 01/31/2013] [Indexed: 11/25/2022]
Abstract
We present a neural network model where the spatial and temporal components of a task are merged and learned in the hippocampus as chains of associations between sensory events. The prefrontal cortex integrates this information to build a cognitive map representing the environment. The cognitive map can be used after latent learning to select optimal actions to fulfill the goals of the animal. A simulation of the architecture is made and applied to learning and solving tasks that involve both spatial and temporal knowledge. We show how this model can be used to solve the continuous place navigation task, where a rat has to navigate to an unmarked goal and wait for 2 seconds without moving to receive a reward. The results emphasize the role of the hippocampus for both spatial and timing prediction, and the prefrontal cortex in the learning of goals related to the task.
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Affiliation(s)
- J Hirel
- ETIS, ENSEA, Université de Cergy-Pontoise, CNRS F-95000 Cergy-Pontoise, France
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24
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Hunsaker MR, Kesner RP. The operation of pattern separation and pattern completion processes associated with different attributes or domains of memory. Neurosci Biobehav Rev 2012; 37:36-58. [PMID: 23043857 DOI: 10.1016/j.neubiorev.2012.09.014] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Revised: 09/19/2012] [Accepted: 09/26/2012] [Indexed: 12/21/2022]
Abstract
Pattern separation and pattern completion processes are central to how the brain processes information in an efficient manner. Research into these processes is escalating and deficient pattern separation is being implicated in a wide array of genetic disorders as well as in neurocognitive aging. Despite the quantity of research, there remains a controversy as to precisely which behavioral paradigms should be used to best tap into pattern separation and pattern completion processes, as well as to what constitute legitimate outcome measures reflecting impairments in pattern separation and pattern completion. This review will discuss a theory based on multiple memory systems that provides a framework upon which behavioral tasks can be designed and their results interpreted. Furthermore, this review will discuss the nature of pattern separation and pattern completion and extend these processes outside the hippocampus and across all domains of information processing. After these discussions, an optimal strategy for designing behavioral paradigms to evaluate pattern separation and pattern completion processes will be provided.
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Affiliation(s)
- Michael R Hunsaker
- Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California, Davis Medical Center, 2805 50th Street, Room 1415, Sacramento, CA 95817, USA.
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25
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Saleewong T, Srikiatkhachorn A, Maneepark M, Chonwerayuth A, Bongsebandhu-phubhakdi S. Quantifying altered long-term potentiation in the CA1 hippocampus. J Integr Neurosci 2012; 11:243-64. [PMID: 22934805 DOI: 10.1142/s0219635212500173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Long-term potentiation (LTP) of synaptic transmission is a widely accepted model of learning and memory. In vitro brain slice techniques were used to investigate the effects of cortical-spreading depression and picrotoxin, an antagonist of the gamma-aminobutyric acid A (GABA(A)) receptor, on the tetanus-induced long-term potentiation of field excitatory postsynaptic potentials. Cortical-spreading depression is involved in glutamate desensitization; on the other hand, GABA(A) antagonists could increase postsynaptic excitability. This study shows that picrotoxin effectively induced long-term potentiation with 142.25 ± 4.18% of the baseline in the picrotoxin group (n = 8) versus 134.36 ± 2.35% of the baseline in the control group (n = 10). In group with picrotoxin applied to CSD, we obtained the smallest magnitude of LTP (120.15 ± 3.73% of the baseline, n = 8). These results suggest that picrotoxin could increase hippocampal activity and LTP; on the contrary, CSD reduced LTP magnitude. In addition, the results also suggest that the decay rate of post-tetanic potentiation has a direct relationship with LTP. Moreover, data were interpreted by nonlinear least squares quantifying, and LTP could also be quantified. The nonlinear attribute of LTP had an influence on the fitting, with respect to increasing the accuracy of the parameters and the compatibility of combination of stimuli that produce LTP.
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Affiliation(s)
- T Saleewong
- Biomedical Engineering Program, Faculty of Engineering, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok, Thailand 10330
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26
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Duncan K, Sadanand A, Davachi L. Memory's penumbra: episodic memory decisions induce lingering mnemonic biases. Science 2012; 337:485-7. [PMID: 22837528 DOI: 10.1126/science.1221936] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
How do we decide if the people we meet and the things we see are familiar or new? If something is new, we need to encode it as a memory distinct from already stored episodes, using a process known as pattern separation. If familiar, it can be used to reactivate a previously stored memory, by a process known as pattern completion. To orchestrate these conflicting processes, current models propose that the episodic memory system uses environmental cues to establish processing biases that favor either pattern separation during encoding or pattern completion during retrieval. To assess this theory, we measured how people's memory formation and decisions are influenced by their recent engagement in episodic encoding and retrieval. We found that the recent encoding of novel objects improved subsequent identification of subtle changes, a task thought to rely on pattern separation. Conversely, recent retrieval of old objects increased the subsequent integration of stored information into new memories, a process thought to rely on pattern completion. These experiments provide behavioral evidence that episodic encoding and retrieval evoke lingering biases that influence subsequent mnemonic processing.
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Affiliation(s)
- Katherine Duncan
- Department of Psychology, Columbia University, New York, NY 10027, USA
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27
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Associative memory storage and retrieval: involvement of theta oscillations in hippocampal information processing. Neural Plast 2011; 2011:683961. [PMID: 21961072 PMCID: PMC3180781 DOI: 10.1155/2011/683961] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 06/25/2011] [Accepted: 07/09/2011] [Indexed: 12/26/2022] Open
Abstract
Theta oscillations are thought to play a critical role in neuronal information processing, especially in the hippocampal region, where their presence is particularly salient. A detailed description of theta dynamics in this region has revealed not only a consortium of layer-specific theta dipoles, but also within-layer differences in the expression of theta. This complex and articulated arrangement of current flows is reflected in the way neuronal firing is modulated in time. Several models have proposed that these different theta modulators flexibly coordinate hippocampal regions, to support associative memory formation and retrieval. Here, we summarily review different approaches related to this issue and we describe a mechanism, based on experimental and simulation results, for memory retrieval in CA3 involving theta modulation.
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28
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Spatiotemporal coupling between hippocampal acetylcholine release and theta oscillations in vivo. J Neurosci 2010; 30:13431-40. [PMID: 20926669 DOI: 10.1523/jneurosci.1144-10.2010] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Both acetylcholine (ACh) and theta oscillations are important for learning and memory, but the dynamic interaction between these two processes remains unclear. Recent advances in amperometry techniques have revealed phasic ACh releases in vivo. However, it is unknown whether phasic ACh release co-occurs with theta oscillations. We investigated this issue in the CA1 region of urethane-anesthetized male rats using amperometric and electrophysiological recordings. We found that ACh release was highly correlated with the appearance of both spontaneous and induced theta oscillations. Moreover, the maximal ACh release was observed around or slightly above the pyramidal layer. Interestingly, such release lagged behind theta initiation by 25-60 s. The slow ACh release profile was matched by the slow firing rate increase of a subset of medial-septal low-firing-rate neurons. Together, these results establish, for the first time, the in vivo coupling between phasic ACh release and theta oscillations on spatiotemporal scales much finer than previously known. These findings also suggest that phasic ACh is not required for theta initiation and may instead operate synergistically with theta oscillations to promote neural plasticity in the service of learning and memory.
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29
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Nishiyama M, Togashi K, Aihara T, Hong K. GABAergic activities control spike timing- and frequency-dependent long-term depression at hippocampal excitatory synapses. Front Synaptic Neurosci 2010; 2:22. [PMID: 21423508 PMCID: PMC3059709 DOI: 10.3389/fnsyn.2010.00022] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 05/30/2010] [Indexed: 11/22/2022] Open
Abstract
GABAergic interneuronal network activities in the hippocampus control a variety of neural functions, including learning and memory, by regulating θ and γ oscillations. How these GABAergic activities at pre- and postsynaptic sites of hippocampal CA1 pyramidal cells differentially contribute to synaptic function and plasticity during their repetitive pre- and postsynaptic spiking at θ and γ oscillations is largely unknown. We show here that activities mediated by postsynaptic GABAARs and presynaptic GABABRs determine, respectively, the spike timing- and frequency-dependence of activity-induced synaptic modifications at Schaffer collateral-CA1 excitatory synapses. We demonstrate that both feedforward and feedback GABAAR-mediated inhibition in the postsynaptic cell controls the spike timing-dependent long-term depression of excitatory inputs (“e-LTD”) at the θ frequency. We also show that feedback postsynaptic inhibition specifically causes e-LTD of inputs that induce small postsynaptic currents (<70 pA) with LTP-timing, thus enforcing the requirement of cooperativity for induction of long-term potentiation at excitatory inputs (“e-LTP”). Furthermore, under spike-timing protocols that induce e-LTP and e-LTD at excitatory synapses, we observed parallel induction of LTP and LTD at inhibitory inputs (“i-LTP” and “i-LTD”) to the same postsynaptic cells. Finally, we show that presynaptic GABABR-mediated inhibition plays a major role in the induction of frequency-dependent e-LTD at α and β frequencies. These observations demonstrate the critical influence of GABAergic interneuronal network activities in regulating the spike timing- and frequency-dependences of long-term synaptic modifications in the hippocampus.
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Affiliation(s)
- Makoto Nishiyama
- Department of Biochemistry, New York University School of Medicine New York, NY, USA
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30
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Nolan CR, Wyeth G, Milford M, Wiles J. The race to learn: Spike timing and STDP can coordinate learning and recall in CA3. Hippocampus 2010; 21:647-60. [DOI: 10.1002/hipo.20777] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2010] [Indexed: 11/07/2022]
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31
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Return of Excitatory Waves from Field CA1 to the Hippocampal Formation Is Facilitated after Tetanization of Schäffer Collaterals during Sleep. ACTA ACUST UNITED AC 2010; 40:315-23. [DOI: 10.1007/s11055-010-9258-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 06/09/2008] [Indexed: 11/30/2022]
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32
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Cutsuridis V, Cobb S, Graham BP. Encoding and retrieval in a model of the hippocampal CA1 microcircuit. Hippocampus 2009; 20:423-46. [PMID: 19489002 DOI: 10.1002/hipo.20661] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Vassilis Cutsuridis
- Department of Computing Science and Mathematics, University of Stirling, Stirling, FK9 4LA, United Kingdom.
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33
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Hunsaker MR, Tran GT, Kesner RP. A double dissociation of subcortical hippocampal efferents for encoding and consolidation/retrieval of spatial information. Hippocampus 2008; 18:699-709. [PMID: 18493950 DOI: 10.1002/hipo.20429] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
CA3 lesions impair encoding, whereas CA1 lesions impair retrieval during learning of a Hebb-Williams maze. CA3 efferents in the fimbria were transected, taking care to spare cholinergic and GABAergic afferents. CA1 efferents in the dorsal fornix were similarly transected. Fimbria transections, but not dorsal fornix transections, resulted in deficits for the encoding of spatial information during learning of a Hebb-Williams maze. Dorsal fornix, but not fimbria, transections resulted in deficits for retrieval of spatial memory during learning of a Hebb-Williams maze. These results reveal a double dissociation for the roles of CA3 and CA1 subcortical efferents in encoding and retrieval processes that mirror the double dissociation seen after excitotoxic lesions of CA1 and CA3. These data provide support for the theory that the cholinergic projections from the septal nuclei modulate the dynamics for encoding and consolidation/retrieval in the hippocampus.
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Affiliation(s)
- Michael R Hunsaker
- Department of Psychology, University of Utah, Salt Lake City, Utah 84112, USA
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34
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Abstract
Central nervous system cholinergic neurons arise from several discrete sources, project to multiple brain regions, and exert specific effects on reward, learning, and memory. These processes are critical for the development and persistence of addictive disorders. Although other neurotransmitters, including dopamine, glutamate, and serotonin, have been the primary focus of drug research to date, a growing preclinical literature reveals a critical role of acetylcholine (ACh) in the experience and progression of drug use. This review will present and integrate the findings regarding the role of ACh in drug dependence, with a primary focus on cocaine and the muscarinic ACh system. Mesostriatal ACh appears to mediate reinforcement through its effect on reward, satiation, and aversion, and chronic cocaine administration produces neuroadaptive changes in the striatum. ACh is further involved in the acquisition of conditional associations that underlie cocaine self-administration and context-dependent sensitization, the acquisition of associations in conditioned learning, and drug procurement through its effects on arousal and attention. Long-term cocaine use may induce neuronal alterations in the brain that affect the ACh system and impair executive function, possibly contributing to the disruptions in decision making that characterize this population. These primarily preclinical studies suggest that ACh exerts a myriad of effects on the addictive process and that persistent changes to the ACh system following chronic drug use may exacerbate the risk of relapse during recovery. Ultimately, ACh modulation may be a potential target for pharmacological treatment interventions in cocaine-addicted subjects. However, the complicated neurocircuitry of the cholinergic system, the multiple ACh receptor subtypes, the confluence of excitatory and inhibitory ACh inputs, and the unique properties of the striatal cholinergic interneurons suggest that a precise target of cholinergic manipulation will be required to impact substance use in the clinical population.
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Affiliation(s)
- Mark J Williams
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390-8564, USA.
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35
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Sizemore M, Perkel DJ. Noradrenergic and GABA B receptor activation differentially modulate inputs to the premotor nucleus RA in zebra finches. J Neurophysiol 2008; 100:8-18. [PMID: 18463188 DOI: 10.1152/jn.01212.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Neuromodulators can rapidly modify neural circuits, altering behavior. Songbirds provide an excellent system for studying the role of neuromodulation in modifying circuits that underlie behavior because song learning and production are mediated by a discrete set of interconnected nuclei. We examined the neuromodulatory effects of noradrenergic and GABA B receptor activation on synaptic inputs to the premotor robust nucleus of the arcopallium (RA) in zebra finches using whole cell voltage-clamp recording in vitro. In adults, norepinephrine strongly reduced input from the lateral magnocellular nucleus of the anterior nidopallium (LMAN) but only slightly reduced the input from nucleus HVC (proper name), the excitatory input from axon collaterals of other RA neurons, and input from GABAergic interneurons. The effect of norepinephrine was mimicked by the alpha2 adrenoceptor agonist UK14,304 and blocked by the alpha2 antagonist yohimbine. Conversely, the GABA B receptor agonist baclofen strongly decreased HVC, collateral, and GABAergic inputs to RA neurons while causing little reduction in the LMAN input. In juveniles undergoing song learning, norepinephrine reduced the LMAN input, caused only a small reduction in the HVC input, and greatly reduced the collateral and GABAergic inputs. Baclofen caused similar results in juvenile and adult birds, reducing HVC, collateral, and GABAergic inputs significantly more than the LMAN input. Significant increases in paired-pulse ratio accompanied all reductions in synaptic transmission, suggesting a presynaptic locus. The reduction in the LMAN input by norepinephrine may be important for mediating changes in song elicited by different social contexts and is well-placed to play a role in song learning.
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Affiliation(s)
- Max Sizemore
- Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, Washington, USA.
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36
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Rózsa B, Katona G, Kaszás A, Szipöcs R, Vizi ES. Dendritic nicotinic receptors modulate backpropagating action potentials and long-term plasticity of interneurons. Eur J Neurosci 2008; 27:364-77. [PMID: 18215234 DOI: 10.1111/j.1460-9568.2007.05999.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stratum radiatum interneurons, unlike pyramidal cells, are rich in nicotinic acetylcholine receptors (nAChRs); however, the role of these receptors in plasticity has remained elusive. As opposed to previous physiological studies, we found that functional alpha7-subunit-containing nAChRs (alpha7-nAChRs) are abundant on interneuron dendrites of rats. Moreover, dendritic Ca2+ transients induced by activation of alpha7-nAChRs increase as a function of distance from soma. The activation of these extrasynaptic alpha7-nAChRs by cholinergic agonists either facilitated or depressed backpropagating action potentials, depending on the timing of alpha7-nAChR activation. We have previously shown that dendritic alpha7-nAChRs are involved in the regulation of synaptic transmission, suggesting that alpha7-nAChRs may play an important role in the regulation of the spike timing-dependent plasticity. Here we provide evidence that long-term potentiation is indeed boosted by stimulation of dendritic alpha7-nAChRs. Our results suggest a new mechanism for a cholinergic switch in memory encoding and retrieval.
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Affiliation(s)
- Balázs Rózsa
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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37
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Ovsepian SV. Differential cholinergic modulation of synaptic encoding and gain control mechanisms in rat hippocampus. Neurosci Res 2008; 61:92-8. [PMID: 18325614 DOI: 10.1016/j.neures.2008.01.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2007] [Revised: 01/19/2008] [Accepted: 01/22/2008] [Indexed: 10/22/2022]
Abstract
Recent studies have highlighted a variety of cognitive effects caused by cholinolytic drug injections into different cortical structures. These findings were largely interpreted as evidence for location-specific cholinergic modulation of synaptic encoding mechanisms. Here, using evoked field responses in anaesthetized rat dorsal hippocampus we show that in addition to reinforcement of synaptic connections (long-term potentiation, LTP), endogenous acetylcholine also regulates firing gain of CA1 pyramidal neurons (EPSP-spike potentiation). Gain augmentation upon increase in cholinergic drive involves evoked synchronous firing at both apical and basal afferent projections, unlike enhancement of activity-induced LTP constrained to the basal afferent system. These data indicate that acetylcholine can act as an effective input and gain controller in the hippocampus. Modulation of synaptic plasticity would determine the relative dominance of afferent inputs while the facilitation of synchronous firing is likely to promote a more generalized spread of excitation and long range communication within the limbic cortex.
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Affiliation(s)
- Saak V Ovsepian
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Dublin 2, Ireland.
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38
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Clearwater JM, Rennie CJ, Robinson PA. Mean field model of acetylcholine mediated dynamics in the cerebral cortex. BIOLOGICAL CYBERNETICS 2007; 97:449-460. [PMID: 17965874 DOI: 10.1007/s00422-007-0186-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 09/24/2007] [Indexed: 05/25/2023]
Abstract
A recent continuum model of the large scale electrical activity of the cerebral cortex is generalized to include cholinergic modulation. In this model, dynamic modulation of synaptic strength acts over the time scales of nicotinic and muscarinic receptor action. The cortical model is analyzed to determine the effect of acetylcholine (ACh) on its steady states, linear stability, spectrum, and temporal responses to changes in subcortical input. ACh increases the firing rate in steady states of the system. Changing ACh concentration does not introduce oscillatory behavior into the system, but increases the overall spectral power. Model responses to pulses in subcortical input are affected by the tonic level of ACh concentration, with higher levels of ACh increasing the magnitude firing rate response of excitatory cortical neurons to pulses of subcortical input. Numerical simulations are used to explore the temporal dynamics of the model in response to changes in ACh concentration. Evidence is seen of a transition from a state in which intracortical inputs are emphasized to a state where thalamic afferents have enhanced influence. Perturbations in ACh concentration cause changes in the firing rate of cortical neurons, with rapid responses due to fast acting facilitatory effects of nicotinic receptors on subcortical afferents, and slower responses due to muscarinic suppression of intracortical connections. Together, these numerical simulations demonstrate that the actions of ACh could be a significant factor modulating early components of evoked response potentials.
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Affiliation(s)
- J M Clearwater
- School of Physics, University of Sydney, Sydney, NSW 2006, Australia.
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39
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Neuromodulation by glutamate and acetylcholine can change circuit dynamics by regulating the relative influence of afferent input and excitatory feedback. Mol Neurobiol 2007; 36:184-200. [PMID: 17952661 DOI: 10.1007/s12035-007-0032-z] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Accepted: 02/02/2007] [Indexed: 10/23/2022]
Abstract
Substances such as acetylcholine and glutamate act as both neurotransmitters and neuromodulators. As neuromodulators, they change neural information processing by regulating synaptic transmitter release, altering baseline membrane potential and spiking activity, and modifying long-term synaptic plasticity. Slice physiology research has demonstrated that many neuromodulators differentially modulate afferent, incoming information compared to intrinsic and recurrent processing in cortical structures such as piriform cortex, neocortex, and the hippocampus. The enhancement of afferent (external) pathways versus the suppression at recurrent (internal) pathways could cause cortical dynamics to switch between a predominant influence of external stimulation to a predominant influence of internal recall. Modulation of afferent versus intrinsic processing could contribute to the role of neuromodulators in regulating attention, learning, and memory effects in behavior.
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40
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Kremin T, Hasselmo ME. Cholinergic suppression of glutamatergic synaptic transmission in hippocampal region CA3 exhibits laminar selectivity: Implication for hippocampal network dynamics. Neuroscience 2007; 149:760-7. [PMID: 17964734 DOI: 10.1016/j.neuroscience.2007.07.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 06/28/2007] [Accepted: 07/11/2007] [Indexed: 11/24/2022]
Abstract
Acetylcholine may help set the dynamics within neural systems to facilitate the learning of new information. Neural models have shown that if new information is encoded at the same time as retrieval of existing information that is already stored, the memories will interfere with each other. Structures such as the hippocampus have a distinct laminar organization of inputs that allows this hypothesis to be tested. In region CA1 of the rat (Sprague Dawley) hippocampus, the cholinergic agonist carbachol (CCh) suppresses transmission in stratum radiatum (SR), at synapses of the Schaffer collateral projection from CA3, while having lesser effects in stratum lacunosum-moleculare (SLM), the perforant path projection from entorhinal cortex (Hasselmo and Schnell, 1994). The current research extends support of this selectivity by demonstrating laminar effects in region CA3. CCh caused significantly greater suppression in SR than in SLM at low concentrations, while the difference in suppression was not significant at higher concentrations. Differences in paired-pulse facilitation suggest presynaptic inhibition substantially contributes to the suppression and is highly concentration and stratum dependent. This selective suppression of the recurrent excitation would be appropriate to set CA3 dynamics to prevent runaway modification of the synapses of excitatory recurrent collaterals by reducing the influence of previously stored associations and allowing incoming information from the perforant path to have a predominant influence on neural activity.
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Affiliation(s)
- T Kremin
- Ernest Gallo Clinic & Research Center, University of California at San Francisco, 5858 Horton Street, Suite 200, Emeryville, CA 94680, USA.
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41
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Li S, Topchiy I, Kocsis B. The effect of atropine administered in the medial septum or hippocampus on high- and low-frequency theta rhythms in the hippocampus of urethane anesthetized rats. Synapse 2007; 61:412-9. [PMID: 17372965 DOI: 10.1002/syn.20388] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cholinergic mechanisms are critical for the generation of hippocampal theta rhythm. Cholinergic innervation of the hippocampus originates from the medial septum (MS) and cholinergic receptors are expressed in both the MS and hippocampus. In this study, we compared the effects of the muscarinic receptor antagonist atropine in the MS and the hippocampus on theta generation. Hippocampal theta rhythm was elicited by electrical stimulation of the pontine reticular formation using series of stimuli with varying intensities. Atropine was administered either systemically (50 mg/kg i.p.) or locally in the MS (microdialysis; 25 and 75 mM for 30 or 90 min) or in the hippocampus on one side (microinjection; 20 or 40 ug). The relative power at the peak theta frequency was calculated and averaged over episodes of low-intensity and high-intensity stimulations. We found that atropine drastically reduced theta rhythmic synchronization when injected in either location. After MS administration of atropine, however, high-frequency theta elicited by high-intensity stimuli was more resistant (58% and 67% decrease after 25 mM and 75 mM atropine, respectively) than slow theta elicited by low-intensity stimuli (86% and 91% decrease). There was no significant difference between the powers of the two oscillations after hippocampal injections (70-75% decrease). We conclude that the theta suppressing effect of atropine involves both hippocampal and septal mechanisms and that low-frequency theta as compared with fast theta rhythm is more sensitive to muscarinic acetylcholine receptor antagonism in the MS but not in the hippocampus.
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Affiliation(s)
- Shaomin Li
- Laboratory of Neurophysiology, Department of Psychiatry, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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42
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Lopez-Hernandez G, Placzek AN, Thinschmidt JS, Lestage P, Trocme-Thibierge C, Morain P, Papke RL. Partial agonist and neuromodulatory activity of S 24795 for alpha7 nAChR responses of hippocampal interneurons. Neuropharmacology 2007; 53:134-44. [PMID: 17544457 DOI: 10.1016/j.neuropharm.2007.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 04/09/2007] [Accepted: 04/18/2007] [Indexed: 11/29/2022]
Abstract
S 24795 evoked methyllycaconitine-sensitive inward currents in voltage-clamped hippocampal interneurons with maximum amplitude about 14% that of ACh-evoked responses. Experiments with rat alpha7 receptors expressed in Xenopus oocytes confirmed that S 24795 is a partial agonist of alpha7 nAChR with an EC(50) of 34+/-11 microM and I(max) of approximately 10% relative to ACh. When 60 microM ACh was co-applied to alpha7-expressing oocytes along with increasing concentrations of S 24795, there was a progressive decrease in response compared to the responses to 60 microM ACh alone (IC(50) 45+/-9 microM). The positive allosteric modulator 5-hydroxyindole potentiated ACh- and S 24795-evoked responses of alpha7 receptors in both oocytes and hippocampal interneurons. In hippocampal slice experiments, depending on the ACh concentrations in the application pipette and the ratio of ACh to S 24795, co-application of S 24795 with ACh variously increased, decreased, or had no effect on responses, compared to ACh alone. In order to estimate the effective dilution factor for the pressure application experiments, we tested alpha7 receptors in oocytes with ACh alone and in co-application with S 24795 at the same ratios as in the slice experiments, but at varying dilution factors. The pattern of interaction seen in the slice experiments was most closely matched under the conditions of a 3:100 dilution, suggesting that the pipette solution was diluted approximately 30-fold at the site of action. This dilution factor was consistent with the potency of ACh and S 24795 in the oocyte expression system (EC(50)s approximately 30 microM).
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Affiliation(s)
- Gretchen Lopez-Hernandez
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL 32610, USA
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43
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Hunsaker MR, Rogers JL, Kesner RP. Behavioral characterization of a transection of dorsal CA3 subcortical efferents: comparison with scopolamine and physostigmine infusions into dorsal CA3. Neurobiol Learn Mem 2007; 88:127-36. [PMID: 17350296 PMCID: PMC2095787 DOI: 10.1016/j.nlm.2007.01.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 01/23/2007] [Accepted: 01/25/2007] [Indexed: 10/23/2022]
Abstract
Cholinergic projections from the medial septum and diagonal band of Broca into the hippocampus have long been implicated in learning and memory. Projections from CA3 to neurons in the medial septum and the diagonal band of Broca have been anatomically characterized. The present experiments were designed to evaluate interactions between the dorsal CA3 subcortical efferents and the cholinergic efferents from the medial septum and diagonal band of Broca for spatial and nonspatial (visual object) novelty detection in the rat. In Experiment 1, physostigmine and scopolamine (both 0.4 microL at 30 microM) were infused into dorsal CA3 and animals were tested on a spatial and nonspatial (visual object) novelty detection paradigm. Scopolamine infusions into dorsal CA3 caused deficits for both spatial and nonspatial (visual object) novelty detection. Physostigmine infusions into dorsal CA3 enhanced both spatial and nonspatial (visual object) novelty detection. These data support models proposing that acetylcholine may control the dynamics for encoding, consolidation, and retrieval in the hippocampus. In Experiment 2, a selective transection of dorsal CA3 efferents in the fimbria resulted in deficits for spatial and nonspatial (visual object) novelty detection. These deficits were similar to the deficits caused by scopolamine infusions into dorsal CA3. These data demonstrate that dorsal CA3 and the medial septum/diagonal band of Broca interact, and that dorsal CA3 influences cholinergic inputs into the hippocampus to facilitate encoding.
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Affiliation(s)
- Michael R Hunsaker
- University of Utah, Department of Psychology, Salt Lake City, UT 84112, USA
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Giocomo LM, Hasselmo ME. Difference in time course of modulation of synaptic transmission by group II versus group III metabotropic glutamate receptors in region CA1 of the hippocampus. Hippocampus 2007; 16:1004-16. [PMID: 17039485 DOI: 10.1002/hipo.20231] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We investigated the time course of modulation of synaptic transmission by group II and group III metabotropic glutamate receptors in region CA1 of the hippocampus. In the presence of 50 microM picrotoxin, pressure pulse application of 1 mM glutamate resulted in a fast onset of suppression of synaptic transmission in stratum lacunosum moleculare and a slower onset of suppression in stratum radiatum, with both effects returning to baseline over the course of several minutes. Application of 50 microM of the group II agonist (2R,4R)-APDC in stratum lacunosum moleculare resulted in the same fast onset of suppression while having no effect in stratum radiatum. Pressure pulse application of 100 microM DL-AP4 in stratum lacunosum moleculare and stratum radiatum resulted in a much slower onset of suppression of synaptic transmission than (2R,4R)-APDC. Suppression by (2R,4R)-APDC was accompanied by a rapid enhancement of paired pulse facilitation, indicative of a presynaptic mechanism. This demonstrates that activation of group II mGluRs in the hippocampus causes a fast onset of suppression in stratum lacunosum moleculare, while activation of group III mGluRs causes a slower onset of suppression. The difference in time course for group II vs. group III mGluRs suggests a different functional role, with group II playing a potential role in making synapses act as low pass filters.
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Affiliation(s)
- Lisa M Giocomo
- Program in Neuroscience, Center for Memory and Brain, Boston University, Boston, MA 02214, USA.
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45
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Meeter M, Talamini L, Schmitt JAJ, Riedel WJ. Effects of 5-HT on memory and the hippocampus: model and data. Neuropsychopharmacology 2006; 31:712-20. [PMID: 16132065 DOI: 10.1038/sj.npp.1300869] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
5-Hydroxytryptamine (5-HT) transmission has been implicated in memory and in depression. Both 5-HT depletion and specific 5-HT agonists lower memory performance, while depression is also associated with memory deficits. The precise neuropharmacology and neural mechanisms underlying these effects are unknown. We used neural network simulations to elucidate the neuropharmacology and network mechanisms underlying 5-HT effects on memory. The model predicts that these effects are largely dependent on transmission over the 5-HT1A and 5-HT3 receptors, which regulate the selectivity of retrieval. It also predicts differential memory deficit profiles for 5-HT depletion and overactivation. The latter predictions were confirmed in studies with healthy and depressed participants undergoing acute tryptophan depletion or ipsipirone challenge. The results suggest that the memory impairments in depressed subjects may be related to 5-HT undertransmission, and support the notion that 5-HT1A agonists ameliorate memory deficits in depression.
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Affiliation(s)
- Martijn Meeter
- Department of Cognitive Psychology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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Hasselmo ME. What is the function of hippocampal theta rhythm?--Linking behavioral data to phasic properties of field potential and unit recording data. Hippocampus 2005; 15:936-49. [PMID: 16158423 DOI: 10.1002/hipo.20116] [Citation(s) in RCA: 329] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The extensive physiological data on hippocampal theta rhythm provide an opportunity to evaluate hypotheses about the role of theta rhythm for hippocampal network function. Computational models based on these hypotheses help to link behavioral data with physiological measurements of different variables during theta rhythm. This paper reviews work on network models in which theta rhythm contributes to the following functions: (1) separating the dynamics of encoding and retrieval, (2) enhancing the context-dependent retrieval of sequences, (3) buffering of novel information in entorhinal cortex (EC) for episodic encoding, and (4) timing interactions between prefrontal cortex and hippocampus for memory-guided action selection. Modeling shows how these functional mechanisms are related to physiological data from the hippocampal formation, including (1) the phase relationships of synaptic currents during theta rhythm measured by current source density analysis of electroencephalographic data from region CA1 and dentate gyrus, (2) the timing of action potentials, including the theta phase precession of single place cells during running on a linear track, the context-dependent changes in theta phase precession across trials on each day, and the context-dependent firing properties of hippocampal neurons in spatial alternation (e.g., "splitter cells"), (3) the cholinergic regulation of sustained activity in entorhinal cortical neurons, and (4) the phasic timing of prefrontal cortical neurons relative to hippocampal theta rhythm.
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Affiliation(s)
- Michael E Hasselmo
- Department of Psychology, Center for Memory and Brain, Program in Neuroscience, Boston University, Boston, MA 02215, USA.
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Tateno T, Jimbo Y, Robinson HPC. Spatio-temporal cholinergic modulation in cultured networks of rat cortical neurons: spontaneous activity. Neuroscience 2005; 134:425-37. [PMID: 15993003 DOI: 10.1016/j.neuroscience.2005.04.049] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Revised: 04/01/2005] [Accepted: 04/27/2005] [Indexed: 10/25/2022]
Abstract
Activation of the cholinergic innervation of the cortex has been implicated in sensory processing, learning, and memory. At the cellular level, acetylcholine both increases excitability and depresses synaptic transmission, and its effects on network firing are hard to predict. We studied the effects of carbachol, a cholinergic agonist, on network firing in cultures of rat cortical neurons, using electrode arrays to monitor the activity of large numbers of neurons simultaneously. These cultures show stable spontaneous synchronized burst firing which propagates through dense synaptic connections. Carbachol (10-50 microM), acting through muscarinic receptors, was found to induce a switch to asynchronous single-spike firing and to result in a loss of regularity and fragmentation of the burst structure. To obtain a quantitative measure of cholinergic actions on cortical networks, we applied a cluster Poisson-process model to sets of paralleled spike-trains in the presence and absence of carbachol. This revealed that the time series can be well-characterized by such a simple model, consistent with the observed 1/f(b)-like spectra (0.04<b<2.08). After applying higher concentrations of carbachol the property of the spectra shifted toward a Poisson-process (white) spectrum. These results indicate that cholinergic neurotransmitters have a strong and reliable desynchronizing action on cortical neural activity.
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Affiliation(s)
- T Tateno
- Department of Physiology, Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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48
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Rowe DL, Robinson PA, Gordon E. Stimulant drug action in attention deficit hyperactivity disorder (ADHD): inference of neurophysiological mechanisms via quantitative modelling. Clin Neurophysiol 2005; 116:324-35. [PMID: 15661111 DOI: 10.1016/j.clinph.2004.08.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE To infer the neural mechanisms underlying tonic transitions in the electroencephalogram (EEG) in 11 adolescents diagnosed with attention deficit hyperactivity disorder (ADHD) before and after treatment with stimulant medication. METHODS A biophysical model was used to analyse electroencephalographic (EEG) measures of tonic brain activity at multiple scalp sites before and after treatment with medication. RESULTS It was observed that stimulants had the affect of significantly reducing the parameter controlling activation in the intrathalamic pathway involving the thalamic reticular nucleus (TRN) and the parameter controlling excitatory cortical activity. The effect of stimulant medication was also found to be preferentially localized within subcortical nuclei projecting towards frontal and central scalp sites. CONCLUSIONS It is suggested that the action of stimulant medication occurs via suppression of the locus coeruleus, which in turn reduces stimulation of the TRN, and improves cortical arousal. The effects localized to frontal and central sites are consistent with the occurrence of frontal delta-theta EEG abnormalities in ADHD, and existing theories of hypoarousal. SIGNIFICANCE To our knowledge, this is the first study where a detailed biophysical model of the brain has been used to estimate changes in neurophysiological parameters underlying the effects of stimulant medication in ADHD.
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Affiliation(s)
- D L Rowe
- School of Physics, University of Sydney, Camperdown, NSW 2006, Australia.
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49
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Rowe DL. A FRAMEWORK FOR INVESTIGATING THALAMOCORTICAL ACTIVITY IN MULTISTAGE INFORMATION PROCESSING. J Integr Neurosci 2005; 4:5-26. [PMID: 16035138 DOI: 10.1142/s0219635205000707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 02/21/2005] [Indexed: 11/18/2022] Open
Abstract
A framework for investigating information processing in cortico-thalamocortical (cortico-TC) networks is presented, that in part can be used to model and interpret individual changes in electroencephalographic spectra and event-related potentials such as those from the Brain Resource International Database. Scientific work covering neurophysiology, TC firing modes, and TC models are explored in the framework to explain how the brain might process complex information in a multistage process. It is proposed that the thalamus and the cortico-TC system have unique ionic properties and transmission delays (in humans), which are suited to the function of taking "snapshots" or samples of complex environmental stimuli, rather than continuous data streams. This leads to careful and sequential coordination of stimulus and response processes, and increases the probability of information transfer and the resulting information complexity in higher cortical regions. Given the scope of this framework, the multidimensional and standardized Brain Resource International Database provides a pertinent set of measures for both testing hypotheses generated from the model, and for fitting the model to experimental data to investigate mechanisms underlying information processing.
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Affiliation(s)
- Donald L Rowe
- The Brain Dynamics Center, University of Sydney and Westmead Hospital, NSW 2145, Australia.
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50
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Kunec S, Hasselmo ME, Kopell N. Encoding and retrieval in the CA3 region of the hippocampus: a model of theta-phase separation. J Neurophysiol 2005; 94:70-82. [PMID: 15728768 DOI: 10.1152/jn.00731.2004] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Past research conducted by Hasselmo et al. in 2002 suggests that some fundamental tasks are better accomplished if memories are encoded and recovered during different parts of the theta cycle. A model of the CA3 subfield of the hippocampus is presented, using biophysical representations of the major cell types including pyramidal cells and two types of interneurons. Inputs to the network come from the septum and the entorhinal cortex (directly and by the dentate gyrus). A mechanism for parsing the theta rhythm into two epochs is proposed and simulated: in the first half, the strong, proximal input from the dentate to a subset of CA3 pyramidal cells and coincident, direct input from the entorhinal cortex to other pyramidal cells creates an environment for strengthening synapses between cells, thus encoding information. During the second half of theta, cueing signals from the entorhinal cortex, by the dentate, activate previously strengthened synapses, retrieving memories. Slow inhibitory neurons (O-LM cells) play a role in the disambiguation during retrieval. We compare and contrast our computational results with existing experimental data and other contemporary models.
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Affiliation(s)
- Steve Kunec
- Center for Biodynamics, Department of Mathematics and Statistics, Boston University, 111 Cummington Street, Boston, Massachusetts 02215, USA.
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