scholarly journals The role of piriform associative connections in odor categorization

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Xiaojun Bao ◽  
Louise LG Raguet ◽  
Sydni M Cole ◽  
James D Howard ◽  
Jay A Gottfried
Keyword(s):  
Activity Patterns ◽  
Piriform Cortex ◽  
Discrimination Performance ◽  
Object Identification ◽  
Pattern Separation ◽  
Odor Perception ◽  
Drug Induced ◽  
Multivariate Pattern ◽  
The Brain

Distributed neural activity patterns are widely proposed to underlie object identification and categorization in the brain. In the olfactory domain, pattern-based representations of odor objects are encoded in piriform cortex. This region receives both afferent and associative inputs, though their relative contributions to odor perception are poorly understood. Here, we combined a placebo-controlled pharmacological fMRI paradigm with multivariate pattern analyses to test the role of associative connections in sustaining olfactory categorical representations. Administration of baclofen, a GABA(B) agonist known to attenuate piriform associative inputs, interfered with within-category pattern separation in piriform cortex, and the magnitude of this drug-induced change predicted perceptual alterations in fine-odor discrimination performance. Comparatively, baclofen reduced pattern separation between odor categories in orbitofrontal cortex, and impeded within-category generalization in hippocampus. Our findings suggest that odor categorization is a dynamic process concurrently engaging stimulus discrimination and generalization at different stages of olfactory information processing, and highlight the importance of associative networks in maintaining categorical boundaries.

Interactions of Excitatory and Inhibitory Feedback Topologies in Facilitating Pattern Separation and Retrieval

2012 ◽  
Vol 24 (1) ◽  
pp. 32-59
Author(s):  
Jane X. Wang ◽  
Michal Zochowski
Keyword(s):  
Memory Management ◽  
Activity Patterns ◽  
Pattern Separation ◽  
Memory Recall ◽  
Cognitive States ◽  
Management Processes ◽  
Inhibitory Feedback ◽  
Global And Local ◽  
The Brain

Within the brain, the interplay between connectivity patterns of neurons and their spatiotemporal dynamics is believed to be intricately linked to the bases of behavior, such as the process of storing, consolidating, and retrieving memory traces. Memory is believed to be stored in the synaptic patterns of anatomical circuitry in the form of increased connectivity densities within subpopulations of neurons. At the same time, memory recall is thought to correspond to activation of discrete areas of the brain corresponding to those memories. Such regional subpopulations can selectively activate during memory recall or retrieval, signifying the process of accessing a single memory or concept. It has been shown previously that recovery of single memory activity patterns is mediated by global neuromodulation signifying transition into different cognitive states such as sleep or awake exploration. We examine how underlying topology can affect memory awake activation and sleep reactivation when such memories share increasing proportions of neurons. The results show that while single memory activation is diminished with increased overlap, pattern separation can be recovered by offsetting excitatory associations between two memories with targeted and heterogeneous inhibitory feedback. Such findings point to the importance of excitatory-to-inhibitory current balance at both the global and local levels in the context of memory retrieval and replay, and highlight the role of network topology in memory management processes.

scholarly journals The Olfactory Mosaic: Bringing an Olfactory Network Together for Odor Perception

Perception ◽  
2016 ◽  
Vol 46 (3-4) ◽  
pp. 320-332 ◽  
Author(s):  
Emmanuelle Courtiol ◽  
Donald A. Wilson
Keyword(s):  
Learning Experience ◽  
Piriform Cortex ◽  
Behavioral Responses ◽  
Neural Mechanisms ◽  
Odor Perception ◽  
Dynamic Interactions ◽  
Molecular Features ◽  
Primary Sensory Cortex ◽  
The Many

Olfactory perception and its underlying neural mechanisms are not fixed, but rather vary over time, dependent on various parameters such as state, task, or learning experience. In olfaction, one of the primary sensory areas beyond the olfactory bulb is the piriform cortex. Due to an increasing number of functions attributed to the piriform cortex, it has been argued to be an associative cortex rather than a simple primary sensory cortex. In fact, the piriform cortex plays a key role in creating olfactory percepts, helping to form configural odor objects from the molecular features extracted in the nose. Moreover, its dynamic interactions with other olfactory and nonolfactory areas are also critical in shaping the olfactory percept and resulting behavioral responses. In this brief review, we will describe the key role of the piriform cortex in the larger olfactory perceptual network, some of the many actors of this network, and the importance of the dynamic interactions among the piriform-trans-thalamic and limbic pathways.

scholarly journals Investigating the role of dendrites in pattern separation: A computational approach

2015 ◽  
Author(s):  
Spyridon Chavlis ◽  
Panagiotis C. Petrantonakis ◽  
Panayiota Poirazi
Keyword(s):  
Granule Cells ◽  
Separation Efficiency ◽  
Hamming Distance ◽  
Morphological Characteristics ◽  
Pattern Separation ◽  
Biologically Relevant ◽  
Preliminary Results ◽  
Neuronal Types ◽  
The Brain

Objectives: In order to distinguish similar memories, it is experimentally confirmed that the hippocampus forms distinct representations of them. The ability of the brain to disambiguate memories is known as pattern separation. It has been proposed that dentate gyrus (DG) accomplishes this task, specifically through its principal cells, called granule cells (GCs). In this project we investigate the role of GC dendrites in pattern separation by modifying their biophysical and morphological characteristics. Methods & Results: We have implemented a morphologically simple, yet biologically relevant, computational model of the DG that implements pattern separation. The network consists of four well-studied neuronal types: granule, mossy, basket, and HIPP cells. The GC model consists of an integrate-and-fire somatic compartment connected to a variable numbers of active dendritic compartments. For simplicity reasons, without sacrificing detail, we used point neurons to simulate the remaining neuronal types. GCs major input from the Entorhinal Cortex (EC) is simulated as independent poisson spike trains at realistic firing frequencies. The output of the network corresponds to the spiking activity of GCs and is estimated on two highly overlapping input patterns. Pattern separation is accomplished when the similarity between these input patterns is greater than the similarity between the respective output patterns, as assessed by the Hamming Distance (HD) metric. Preliminary results show that there is a positive correlation between the separation efficiency and the number of GC dendrites. Conclusions: Our preliminary results suggest that dendrites of GC cells facilitate the pattern separation capabilities of the DG.

scholarly journals Pathophysiological mechanisms underlying antipsychotic-induced tardive dyskinesia

2020 ◽  
Vol 18 (4) ◽  
pp. 169-184
Author(s):  
E. E. Vayman ◽  
N. A. Shnayder ◽  
N. G. Neznanov ◽  
R. F. Nasyrova
Keyword(s):  
Tardive Dyskinesia ◽  
Dopaminergic Neurons ◽  
Neurological Complication ◽  
Carbonyl Stress ◽  
Endogenous Opioid System ◽  
Endogenous Opioid ◽  
Drug Induced ◽  
Pathophysiological Mechanisms ◽  
The Brain

Purpose. To analyze the results of classical and modern studies reflecting the pathophysiological mechanisms of antipsychotic-induced tardive dyskinesia.Materials and methods. We searched for full-text publications in Russian and English in the databases of E-Library, PubMed, Web of Science and Springer published over the past decade, using keywords (tardive dyskinesia (TD), drug-induced tardive dyskinesia, antipsychotics (AP), neuroleptics, typical antipsychotics, atypical antipsychotics, pathophysiology, etiology and combinations of these words). In addition, the review included earlier publications of historical interest.Results. The lecture proposed theories of development of AP-induced TD, examining its effect on dopaminergic receptors, dopaminergic neurons, neurons of the basal ganglia, and other theories: activation of estrogen receptors, disorders of melatonin metabolism, disorders of the endogenous opioid system, oxidative stress with predominant oxidation processes, blockade of 5-HT2-receptors, a decrease in the pyridoxine level, genetic predisposition, interaction of AP with the brain trace element – iron, carbonyl stress and immune inflammation and the role of the neurotrophic factor.Conclusion. The disclosure of the mechanisms of AP-induced TD will allow the development of a strategy for personalized prevention and therapy of the considered neurological complication of the AP-therapy for schizophrenia in real clinical practice. 

scholarly journals Pattern separation is the key driver of expectation-modulated memory

2019 ◽  
Author(s):  
Darya Frank ◽  
Daniela Montaldi
Keyword(s):  
Memory Performance ◽  
Recognition Task ◽  
Discrimination Performance ◽  
Pattern Separation ◽  
Cognitive Factors ◽  
Previous Trial ◽  
Pattern Completion ◽  
Logical Deduction ◽  
Key Driver

AbstractThe hippocampus uses pattern separation and pattern completion in a continuous manner to successfully encode and retrieve memories1,2. However, whether and how cognitive factors might modulate the dynamics between these types of computation is not well understood. Here we examine the role of expectation in shifting the hippocampus to perform pattern separation. Expectation can be built up through multiple contextual exposures leading to prediction (as in a learnt contingency) or through logical deduction based on a previous mnemonic response. Participants first learned a contingency between a cue and an object’s category (man-made or natural). Then, at encoding, one third of the cues that preceded the to-be-memorised objects violated the studied rule. At test, participants performed an old/new recognition task with old items (targets) and a set of parametrically manipulated (very similar to dissimilar) new foils for each object. We explored the effects of both contextual expectation, manipulated at initial encoding, and mnemonic-attribution expectation, driven by the mnemonic decisions taken on previous retrieval trials. For example, a target would be unexpected if in a previous trial a similar foil had been erroneously accepted as old. Memory was found to be better for foils of high and mid similarity to contextually unexpected targets at encoding, compared to expected ones. Additionally, violations of mnemonic-attribution expectation also yielded improved memory performance when the level of foil similarity was high. These results suggest that violations of both contextual expectation and mnemonic-attribution expectation engage pattern separation, resulting in better discrimination performance for these items. Importantly, this mechanism is engaged when input differentiation is required in order to make a correct recognition decision.

scholarly journals TREM2 deficiency attenuates neuroinflammation and protects against neurodegeneration in a mouse model of tauopathy

2017 ◽  
Vol 114 (43) ◽  
pp. 11524-11529 ◽  
Author(s):  
Cheryl E. G. Leyns ◽  
Jason D. Ulrich ◽  
Mary B. Finn ◽  
Floy R. Stewart ◽  
Lauren J. Koscal ◽  
...  
Keyword(s):  
Microglial Activation ◽  
Potential Role ◽  
Piriform Cortex ◽  
Tau Pathology ◽  
Gene Encoding ◽  
Gene Expression Analyses ◽  
Unexpected Findings ◽  
Microglial Response ◽  
The Brain

Variants in the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) were recently found to increase the risk for developing Alzheimer’s disease (AD). In the brain, TREM2 is predominately expressed on microglia, and its association with AD adds to increasing evidence implicating a role for the innate immune system in AD initiation and progression. Thus far, studies have found TREM2 is protective in the response to amyloid pathology while variants leading to a loss of TREM2 function impair microglial signaling and are deleterious. However, the potential role of TREM2 in the context of tau pathology has not yet been characterized. In this study, we crossed Trem2+/+ (T2+/+) and Trem2−/− (T2−/−) mice to the PS19 human tau transgenic line (PS) to investigate whether loss of TREM2 function affected tau pathology, the microglial response to tau pathology, or neurodegeneration. Strikingly, by 9 mo of age, T2−/−PS mice exhibited significantly less brain atrophy as quantified by ventricular enlargement and preserved cortical volume in the entorhinal and piriform regions compared with T2+/+PS mice. However, no TREM2-dependent differences were observed for phosphorylated tau staining or insoluble tau levels. Rather, T2−/−PS mice exhibited significantly reduced microgliosis in the hippocampus and piriform cortex compared with T2+/+PS mice. Gene expression analyses and immunostaining revealed microglial activation was significantly attenuated in T2−/−PS mice, and there were lower levels of inflammatory cytokines and astrogliosis. These unexpected findings suggest that impairing microglial TREM2 signaling reduces neuroinflammation and is protective against neurodegeneration in the setting of pure tauopathy.

scholarly journals Pattern separation and tuning shift in human sensory cortex underlie fear memory

2021 ◽  
Author(s):  
Yuqi You ◽  
Lucas R. Novak ◽  
Kevin Clancy ◽  
Wen Li
Keyword(s):  
Late Onset ◽  
Piriform Cortex ◽  
Fear Memory ◽  
Pattern Separation ◽  
Sensory Cortex ◽  
Evolutionarily Conserved ◽  
Sensory Encoding ◽  
Underlying Mechanisms ◽  
Cortical System

ABSTRACTAnimal research has recognized the role of the sensory cortex in fear memory and two key underlying mechanisms—pattern separation and tuning shift. We interrogated these mechanisms in the human sensory cortex in an olfactory differential conditioning study with a delayed (9-day) retention test. Combining affective appraisal and olfactory psychophysics with functional magnetic resonance imaging (fMRI) multivoxel pattern analysis and voxel-based tuning analysis over a linear odor-morphing continuum, we confirmed affective and perceptual learning and memory and demonstrated associative plasticity in the human olfactory (piriform) cortex. Specifically, the piriform cortex exhibited immediate and lasting enhancement in pattern separation (between the conditioned stimuli/CS and neighboring non-CS) and late-onset yet lasting tuning shift towards the CS, especially in anxious individuals. These findings highlight an evolutionarily conserved sensory cortical system of fear memory, which can underpin sensory encoding of fear/threat and confer a sensory mechanism to the neuropathophysiology of anxiety.

Running the Female Power Grid Across Lifespan Through Brain Estrogen Signaling

2021 ◽  
Vol 84 (1) ◽  
Author(s):  
Holly A. Ingraham ◽  
Candice B. Herber ◽  
William C. Krause
Keyword(s):  
Brain Regions ◽  
Estrogen Signaling ◽  
Annual Review ◽  
Publication Date ◽  
Drug Induced ◽  
Peripheral Tissues ◽  
Hormone Sensitive ◽  
The Brain ◽  
Female Power

The role of central estrogen in cognitive, metabolic, and reproductive health has long fascinated the lay public and scientists alike. In the last two decades, insight into estrogen signaling in the brain and its impact on female physiology is beginning to catch up with the vast information already established for its actions on peripheral tissues. Using newer methods to manipulate estrogen signaling in hormone-sensitive brain regions, neuroscientists are now identifying the molecular pathways and neuronal subtypes required to establish crucial sex differences in energy allocation. However, the immense cellular complexity of these hormone-sensitive brain regions makes it clear that more research is needed to fully appreciate how estrogen modulates neural circuits to regulate physiological and behavioral end points. Such insight is essential for understanding how natural or drug-induced hormone fluctuations across lifespan affect women's health. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals The incentive sensitization theory of addiction: some current issues

2008 ◽  
Vol 363 (1507) ◽  
pp. 3137-3146 ◽  
Author(s):  
Terry E Robinson ◽  
Kent C Berridge
Keyword(s):  
Animal Models ◽  
Incentive Motivation ◽  
Incentive Salience ◽  
Drug Induced ◽  
Incentive Sensitization ◽  
The Brain

We present a brief overview of the incentive sensitization theory of addiction. This posits that addiction is caused primarily by drug-induced sensitization in the brain mesocorticolimbic systems that attribute incentive salience to reward-associated stimuli. If rendered hypersensitive, these systems cause pathological incentive motivation (‘wanting’) for drugs. We address some current questions including: what is the role of learning in incentive sensitization and addiction? Does incentive sensitization occur in human addicts? Is the development of addiction-like behaviour in animals associated with sensitization? What is the best way to model addiction symptoms using animal models? And, finally, what are the roles of affective pleasure or withdrawal in addiction?

scholarly journals Adult hippocampal neurogenesis shapes adaptation and improves stress response: a mechanistic and integrative perspective

2021 ◽  
Author(s):  
A. Surget ◽  
C. Belzung
Keyword(s):  
Stress Response ◽  
Hippocampal Neurogenesis ◽  
Adult Hippocampal Neurogenesis ◽  
Pattern Separation ◽  
Brain Areas ◽  
Functional Involvement ◽  
Different Dimensions ◽  
Stressful Experiences ◽  
The Brain

AbstractAdult hippocampal neurogenesis (AHN) represents a remarkable form of neuroplasticity that has increasingly been linked to the stress response in recent years. However, the hippocampus does not itself support the expression of the different dimensions of the stress response. Moreover, the main hippocampal functions are essentially preserved under AHN depletion and adult-born immature neurons (abGNs) have no extrahippocampal projections, which questions the mechanisms by which abGNs influence functions supported by brain areas far from the hippocampus. Within this framework, we propose that through its computational influences AHN is pivotal in shaping adaption to environmental demands, underlying its role in stress response. The hippocampus with its high input convergence and output divergence represents a computational hub, ideally positioned in the brain (1) to detect cues and contexts linked to past, current and predicted stressful experiences, and (2) to supervise the expression of the stress response at the cognitive, affective, behavioral, and physiological levels. AHN appears to bias hippocampal computations toward enhanced conjunctive encoding and pattern separation, promoting contextual discrimination and cognitive flexibility, reducing proactive interference and generalization of stressful experiences to safe contexts. These effects result in gating downstream brain areas with more accurate and contextualized information, enabling the different dimensions of the stress response to be more appropriately set with specific contexts. Here, we first provide an integrative perspective of the functional involvement of AHN in the hippocampus and a phenomenological overview of the stress response. We then examine the mechanistic underpinning of the role of AHN in the stress response and describe its potential implications in the different dimensions accompanying this response.

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