scholarly journals Cortical-like dynamics in recurrent circuits optimized for sampling-based probabilistic inference

2019 ◽  
Author(s):  
Rodrigo Echeveste ◽  
Laurence Aitchison ◽  
Guillaume Hennequin ◽  
Máté Lengyel
Keyword(s):  
Neural Circuit ◽  
Probabilistic Inference ◽  
Gamma Oscillations ◽  
Biological Properties ◽  
Stimulus Onset ◽  
Cortical Dynamics ◽  
Functional Roles ◽  
Sensory Cortices ◽  
Dynamical Features ◽  
Visual Cortical

Sensory cortices display a suite of ubiquitous dynamical features, such as ongoing noise variability, transient overshoots, and oscillations, that have so far escaped a common, principled theoretical account. We developed a unifying model for these phenomena by training a recurrent excitatory–inhibitory neural circuit model of a visual cortical hypercolumn to perform sampling-based probabilistic inference. The optimized network displayed several key biological properties, including divisive normalization, as well as stimulus-modulated noise variability, inhibition-dominated transients at stimulus onset, and strong gamma oscillations. These dynamical features had distinct functional roles in speeding up inferences and made predictions that we confirmed in novel analyses of awake monkey recordings. Our results suggest that the basic motifs of cortical dynamics emerge as a consequence of the efficient implementation of the same computational function—fast sampling-based inference—and predict further properties of these motifs that can be tested in future experiments.

scholarly journals Bridging physiological and perceptual views of autism by means of sampling-based Bayesian inference

2021 ◽  
pp. 1-27
Author(s):  
Rodrigo Echeveste ◽  
Enzo Ferrante ◽  
Diego H. Milone ◽  
Inés Samengo
Keyword(s):  
Autism Spectrum Disorder ◽  
Neural Circuit ◽  
Autism Spectrum ◽  
Physiological Level ◽  
Cortical Dynamics ◽  
Significant Challenge ◽  
Characteristic Features ◽  
Neural Variability ◽  
Two Sides ◽  
Different Levels

Abstract Theories for autism spectrum disorder (ASD) have been formulated at different levels: ranging from physiological observations to perceptual and behavioral descriptions. Understanding the physiological underpinnings of perceptual traits in ASD remains a significant challenge in the field. Here we show how a recurrent neural circuit model which was optimized to perform sampling-based inference and displays characteristic features of cortical dynamics can help bridge this gap. The model was able to establish a mechanistic link between two descriptive levels for ASD: a physiological level, in terms of inhibitory dysfunction, neural variability and oscillations, and a perceptual level, in terms of hypopriors in Bayesian computations. We took two parallel paths: inducing hypopriors in the probabilistic model, and an inhibitory dysfunction in the network model, which lead to consistent results in terms of the represented posteriors, providing support for the view that both descriptions might constitute two sides of the same coin.

scholarly journals Neural contributors to trauma resilience: a review of longitudinal neuroimaging studies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alyssa R. Roeckner ◽  
Katelyn I. Oliver ◽  
Lauren A. M. Lebois ◽  
Sanne J. H. van Rooij ◽  
Jennifer S. Stevens
Keyword(s):  
Individual Differences ◽  
Neural Circuit ◽  
Major Life ◽  
Stress Resilience ◽  
Control Networks ◽  
The Face ◽  
Sensory Cortices ◽  
Life Stressor ◽  
Threat Cues ◽  
And Function

AbstractResilience in the face of major life stressors is changeable over time and with experience. Accordingly, differing sets of neurobiological factors may contribute to an adaptive stress response before, during, and after the stressor. Longitudinal studies are therefore particularly effective in answering questions about the determinants of resilience. Here we provide an overview of the rapidly-growing body of longitudinal neuroimaging research on stress resilience. Despite lingering gaps and limitations, these studies are beginning to reveal individual differences in neural circuit structure and function that appear protective against the emergence of future psychopathology following a major life stressor. Here we outline a neural circuit model of resilience to trauma. Specifically, pre-trauma biomarkers of resilience show that an ability to modulate activity within threat and salience networks predicts fewer stress-related symptoms. In contrast, early post-trauma biomarkers of subsequent resilience or recovery show a more complex pattern, spanning a number of major circuits including attention and cognitive control networks as well as primary sensory cortices. This novel synthesis suggests stress resilience may be scaffolded by stable individual differences in the processing of threat cues, and further buttressed by post-trauma adaptations to the stressor that encompass multiple mechanisms and circuits. More attention and resources supporting this work will inform the targets and timing of mechanistic resilience-boosting interventions.

scholarly journals A neural circuit for gamma-band coherence across the retinotopic map in mouse visual cortex

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Richard Hakim ◽  
Kiarash Shamardani ◽  
Hillel Adesnik
Keyword(s):  
Visual Cortex ◽  
Neural Circuit ◽  
Brain Slices ◽  
Pyramidal Cells ◽  
Gamma Oscillations ◽  
Gamma Band ◽  
Neuron Activity ◽  
Mouse Visual Cortex ◽  
Retinotopic Map

Cortical gamma oscillations have been implicated in a variety of cognitive, behavioral, and circuit-level phenomena. However, the circuit mechanisms of gamma-band generation and synchronization across cortical space remain uncertain. Using optogenetic patterned illumination in acute brain slices of mouse visual cortex, we define a circuit composed of layer 2/3 (L2/3) pyramidal cells and somatostatin (SOM) interneurons that phase-locks ensembles across the retinotopic map. The network oscillations generated here emerge from non-periodic stimuli, and are stimulus size-dependent, coherent across cortical space, narrow band (30 Hz), and depend on SOM neuron but not parvalbumin (PV) neuron activity; similar to visually induced gamma oscillations observed in vivo. Gamma oscillations generated in separate cortical locations exhibited high coherence as far apart as 850 μm, and lateral gamma entrainment depended on SOM neuron activity. These data identify a circuit that is sufficient to mediate long-range gamma-band coherence in the primary visual cortex.

Realization

Philosophy ◽  
2015 ◽  
Author(s):  
Umut Baysan
Keyword(s):  
Physical Properties ◽  
Philosophy Of Mind ◽  
Relevant Literature ◽  
Biological Properties ◽  
Dependence Relation ◽  
Functional Roles ◽  
Special Sciences ◽  
Painful Sensation ◽  
Mental Properties ◽  
The Mind

“Realization” is a technical term used by philosophers of mind, philosophers of science, and metaphysicians to denote some dependence relation that is thought to exist between higher-level properties or states and lower-level properties or states. Some philosophers of mind hold that mental properties, such as believing that it is raining, having a painful sensation, and so on, are realized by physical properties. Understood this way, the term was introduced to philosophy of mind literature with the thesis that mental properties are multiply realizable by physical properties. Since different physical properties could realize the same mental property, it is thought that the phenomenon of multiple realization shows that the identity theory, namely the view that mental properties are identical with physical properties, is false. For similar reasons, some philosophers of the special sciences think that higher-level properties, such as biological properties, are realized by properties that are invoked in lower-level sciences such as physics. Some metaphysicians suggest that determinable properties, such as color properties (e.g., being red) are realized by their determinate properties (e.g., being crimson, being scarlet). Some argue that dispositional properties, such as being fragile, are realized by non-dispositional, categorical microstructural properties. It has been customary to think that functional properties, such as being a carburetor, are realized by first-order properties that play the specified functional roles. Due to the widely different usages of “realization,” it is difficult to determine if there should be one relation or several relations that this term denotes. Any relation that is denoted by this term can be seen as a realization relation. This article is about such relations. Whereas some theories explicitly formulate realization relations, some tangential theories that concern related issues (e.g., the mind-body problem) make crucial claims as to what counts as a case of realization. This article introduces the central questions about realization and clarifies the main issues and concepts that are invoked in the relevant literature.

scholarly journals Extracellular Enzymes and Bioactive Compounds from Antarctic Terrestrial Fungi for Bioprospecting

2020 ◽  
Vol 17 (18) ◽  
pp. 6459
Author(s):  
Laura Zucconi ◽  
Fabiana Canini ◽  
Marta Elisabetta Temporiti ◽  
Solveig Tosi
Keyword(s):  
Bioactive Compounds ◽  
Extracellular Enzymes ◽  
Biological Properties ◽  
Metabolic Potential ◽  
Functional Roles ◽  
Antarctic Soils ◽  
Terrestrial Fungi ◽  
The Antarctic ◽  
Abiotic Environmental Factors

Antarctica, one of the harshest environments in the world, has been successfully colonized by extremophilic, psychrophilic, and psychrotolerant microorganisms, facing a range of extreme conditions. Fungi are the most diverse taxon in the Antarctic ecosystems, including soils. Genetic adaptation to this environment results in the synthesis of a range of metabolites, with different functional roles in relation to the biotic and abiotic environmental factors, some of which with new biological properties of potential biotechnological interest. An overview on the production of cold-adapted enzymes and other bioactive secondary metabolites from filamentous fungi and yeasts isolated from Antarctic soils is here provided and considerations on their ecological significance are reported. A great number of researches have been carried out to date, based on cultural approaches. More recently, metagenomics approaches are expected to increase our knowledge on metabolic potential of these organisms, leading to the characterization of unculturable taxa. The search on fungi in Antarctica deserves to be improved, since it may represent a useful strategy for finding new metabolic pathways and, consequently, new bioactive compounds.

scholarly journals Physiological Correlates of Sensory Consciousness: Evidence for a Generalized Awareness Negativity

2021 ◽  
Author(s):  
Cole Dembski ◽  
Christof Koch ◽  
Michael Pitts
Keyword(s):  
Experimental Studies ◽  
Neural Correlates ◽  
Stimulus Onset ◽  
Convincing Evidence ◽  
Future Research ◽  
Neural Signals ◽  
Tactile Stimuli ◽  
Neurological Patients ◽  
Sensory Cortices ◽  
Sensory Consciousness

We critically review the recent literature on six EEG and MEG markers of the neural correlates of consciousness (NCC) for visual, auditory and tactile stimuli in neurotypical volunteers and neurological patients. After ruling out four of these as candidate NCC, we focus on two prominent evoked signals: an early, modality-specific negativity, termed the visual or auditory awareness negativity (VAN and AAN, respectively) and a late, modality-independent positivity termed the P3b. More than twelve diverse experimental studies found that the P3b is absent despite consciously seeing, hearing, or feeling stimuli, ruling out the P3b as a true NCC. In contrast, no convincing evidence for a dissociation between the awareness negativities and consciousness has been reported thus far. Furthermore, there is evidence for an equivalent signal in the tactile domain, which we term the somatosensory awareness negativity (SAN). These three neural signals are usually maximal on the side of the scalp contralateral to the evoking stimulus, above the associated sensory cortices. We conclude that the data from these three modalities is consistent with a generalized awareness negativity (GAN) correlated with perceptual consciousness that arises 120-200 ms following stimulus onset and originates from the underlying sensory cortices. The identification of this GAN points towards new, promising avenues for future research and raises an array of concrete questions that can be empirically investigated.

scholarly journals Widespread shorter cortical adaptation in dyslexia

2017 ◽  
Author(s):  
Sagi Jaffe-Dax ◽  
Eva Kimel ◽  
Merav Ahissar
Keyword(s):  
General Characteristic ◽  
Frequency Discrimination ◽  
Previous Trial ◽  
Tone Frequency ◽  
Broad Distribution ◽  
Cortical Dynamics ◽  
Fast Acquisition ◽  
Sensory Cortices ◽  
Cortical Adaptation ◽  
Cortical Distribution

AbstractStudies of dyslexics’ performance on perceptual tasks suggest that their implicit inference of sound statistics is impaired. In a previous paper (Jaffe-Dax, Frenkel, & Ahissar, 2017), using 2-tone frequency discrimination, we found that the effect of previous trial frequencies on dyslexics’ judgments decayed faster than the effect on controls’ judgments, and that the adaptation of their ERP responses to tones recovered faster. Here, we show the cortical distribution of this abnormal dynamics of adaptation using fast acquisition fMRI. We find that dyslexics’ faster decay of adaptation is widespread, though the most significant effects are found in the left superior temporal lobe, including the auditory cortex. This broad distribution suggests that dyslexics’ faster decay of implicit memory is a general characteristic of their cortical dynamics, which also encompasses the sensory cortices.

The N2pc as an Electrophysiological Correlate of Attention in Change Blindness

2009 ◽  
Vol 23 (2) ◽  
pp. 43-51 ◽  
Author(s):  
Andrea Schankin ◽  
Dirk Hagemann ◽  
Edmund Wascher
Keyword(s):  
Change Blindness ◽  
Visual Awareness ◽  
Neural Correlates ◽  
Stimulus Onset ◽  
Attentional Processing ◽  
Electrophysiological Activity ◽  
Cortical Areas ◽  
Physically Identical ◽  
Visual Cortical ◽  
Electrophysiological Correlate

Changes between two successively presented pictures are hard to detect when their presentation is interrupted by a blank (change blindness). This task is well established for investigating the neural correlates of visual awareness. It allows the comparison of electrophysiological activity evoked by physically identical trials in which the change was detected versus trials in which the change remained unnoticed. One possible correlate of aware processing is the N2pc component, an increased negative activity, contralateral to a processed stimulus between 200–300 ms after stimulus onset. However, this component has been also assigned to the allocation of attention. In two experiments, an N2pc was observed for detected changes. This component was markedly reduced for undetected changes and even more if participants reported a change that was not present (imagined change). These results suggest that the N2pc rather reflects attentional processing of stimuli in visual cortical areas than the actual aware representation.

Opposite effects of lateralised transcranial alpha versus gamma stimulation on spatial attention

2017 ◽  
Author(s):  
Malte Wöstmann ◽  
Johannes Vosskuhl ◽  
Jonas Obleser ◽  
Christoph S. Herrmann
Keyword(s):  
Spatial Attention ◽  
Gamma Oscillations ◽  
Proof Of Concept ◽  
Functional Roles ◽  
Dichotic Listening Task ◽  
High Gamma ◽  
Transcranial Alternating Current Stimulation ◽  
Human Participants ◽  
Listening Task ◽  
Selection Of

AbstractSpatial attention relatively increases the power of neural 10-Hz alpha oscillations in the hemisphere ipsilateral to attention. The functional roles of lateralised oscillations for attention are unclear. Here, 20 human participants performed a dichotic listening task under continuous transcranial alternating current stimulation (tACS) at alpha (10 Hz, vs sham) or gamma (47 Hz, vs sham) frequency, targeting left temporo-parietal cortex. Participants attended to four spoken numbers presented to one ear, while ignoring numbers on the other ear. As predicted, we found that alpha-tACS contralateral to the attended ear decreased recall of attended targets. Notably, gamma-tACS reversed the effect. Results provide a proof of concept that externally amplified oscillations can enhance spatial attention and facilitate attentional selection of speech. Furthermore, opposite effects of alpha versus gamma oscillations support the view that, across modalities, states of high alpha are incommensurate with active neural processing as reflected by states of high gamma.

scholarly journals Progressive maturation of silent synapses governs the duration of a critical period

2015 ◽  
Vol 112 (24) ◽  
pp. E3131-E3140 ◽  
Author(s):  
Xiaojie Huang ◽  
Sophia K. Stodieck ◽  
Bianka Goetze ◽  
Lei Cui ◽  
Man Ho Wong ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Critical Period ◽  
Neural Circuit ◽  
Ocular Dominance ◽  
Critical Periods ◽  
Ocular Dominance Plasticity ◽  
Silent Synapses ◽  
Synapse Maturation ◽  
Silent Synapse ◽  
Visual Cortical

During critical periods, all cortical neural circuits are refined to optimize their functional properties. The prevailing notion is that the balance between excitation and inhibition determines the onset and closure of critical periods. In contrast, we show that maturation of silent glutamatergic synapses onto principal neurons was sufficient to govern the duration of the critical period for ocular dominance plasticity in the visual cortex of mice. Specifically, postsynaptic density protein-95 (PSD-95) was absolutely required for experience-dependent maturation of silent synapses, and its absence before the onset of critical periods resulted in lifelong juvenile ocular dominance plasticity. Loss of PSD-95 in the visual cortex after the closure of the critical period reinstated silent synapses, resulting in reopening of juvenile-like ocular dominance plasticity. Additionally, silent synapse-based ocular dominance plasticity was largely independent of the inhibitory tone, whose developmental maturation was independent of PSD-95. Moreover, glutamatergic synaptic transmission onto parvalbumin-positive interneurons was unaltered in PSD-95 KO mice. These findings reveal not only that PSD-95–dependent silent synapse maturation in visual cortical principal neurons terminates the critical period for ocular dominance plasticity but also indicate that, in general, once silent synapses are consolidated in any neural circuit, initial experience-dependent functional optimization and critical periods end.

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