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Karl Friston

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https://www.readbyqxmd.com/read/29029962/answering-schr%C3%A3-dinger-s-question-a-free-energy-formulation
#1
REVIEW
Maxwell James Désormeau Ramstead, Paul Benjamin Badcock, Karl John Friston
The free-energy principle (FEP) is a formal model of neuronal processes that is widely recognised in neuroscience as a unifying theory of the brain and biobehaviour. More recently, however, it has been extended beyond the brain to explain the dynamics of living systems, and their unique capacity to avoid decay. The aim of this review is to synthesise these advances with a meta-theoretical ontology of biological systems called variational neuroethology, which integrates the FEP with Tinbergen's four research questions to explain biological systems across spatial and temporal scales...
September 20, 2017: Physics of Life Reviews
https://www.readbyqxmd.com/read/29024792/effective-connectivity-inferred-from-fmri-transition-dynamics-during-movie-viewing-points-to-a-balanced-reconfiguration-of-cortical-interactions
#2
REVIEW
Matthieu Gilson, Gustavo Deco, Karl Friston, Patric Hagmann, Dante Mantini, Viviana Betti, Gian Luca Romani, Maurizio Corbetta
Our behavior entails a flexible and context-sensitive interplay between brain areas to integrate information according to goal-directed requirements. However, the neural mechanisms governing the entrainment of functionally specialized brain areas remain poorly understood. In particular, the question arises whether observed changes in the regional activity for different cognitive conditions are explained by modifications of the inputs to the brain or its connectivity? We observe that transitions of fMRI activity between areas convey information about the tasks performed by 19 subjects, watching a movie versus a black screen (rest)...
October 9, 2017: NeuroImage
https://www.readbyqxmd.com/read/29018337/editorial-self-organization-in-the-nervous-system
#3
EDITORIAL
Yan M Yufik, Biswa Sengupta, Karl Friston
No abstract text is available yet for this article.
2017: Frontiers in Systems Neuroscience
https://www.readbyqxmd.com/read/28981514/a-unifying-bayesian-account-of-contextual-effects-in-value-based-choice
#4
Francesco Rigoli, Christoph Mathys, Karl J Friston, Raymond J Dolan
Empirical evidence suggests the incentive value of an option is affected by other options available during choice and by options presented in the past. These contextual effects are hard to reconcile with classical theories and have inspired accounts where contextual influences play a crucial role. However, each account only addresses one or the other of the empirical findings and a unifying perspective has been elusive. Here, we offer a unifying theory of context effects on incentive value attribution and choice based on normative Bayesian principles...
October 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28851996/uncovering-the-underlying-mechanisms-and-whole-brain-dynamics-of-deep-brain-stimulation-for-parkinson-s-disease
#5
Victor M Saenger, Joshua Kahan, Tom Foltynie, Karl Friston, Tipu Z Aziz, Alexander L Green, Tim J van Hartevelt, Joana Cabral, Angus B A Stevner, Henrique M Fernandes, Laura Mancini, John Thornton, Tarek Yousry, Patricia Limousin, Ludvic Zrinzo, Marwan Hariz, Paulo Marques, Nuno Sousa, Morten L Kringelbach, Gustavo Deco
Deep brain stimulation (DBS) for Parkinson's disease is a highly effective treatment in controlling otherwise debilitating symptoms. Yet the underlying brain mechanisms are currently not well understood. Whole-brain computational modeling was used to disclose the effects of DBS during resting-state functional Magnetic Resonance Imaging in ten patients with Parkinson's disease. Specifically, we explored the local and global impact that DBS has in creating asynchronous, stable or critical oscillatory conditions using a supercritical bifurcation model...
August 29, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28836726/dynamic-causal-modeling-in-ptsd-and-its-dissociative-subtype-bottom-up-versus-top-down-processing-within-fear-and-emotion-regulation-circuitry
#6
Andrew A Nicholson, Karl J Friston, Peter Zeidman, Sherain Harricharan, Margaret C McKinnon, Maria Densmore, Richard W J Neufeld, Jean Théberge, Frank Corrigan, Rakesh Jetly, David Spiegel, Ruth A Lanius
OBJECTIVE: Posttraumatic stress disorder (PTSD) is associated with decreased top-down emotion modulation from medial prefrontal cortex (mPFC) regions, a pathophysiology accompanied by hyperarousal and hyperactivation of the amygdala. By contrast, PTSD patients with the dissociative subtype (PTSD + DS) often exhibit increased mPFC top-down modulation and decreased amygdala activation associated with emotional detachment and hypoarousal. Crucially, PTSD and PTSD + DS display distinct functional connectivity within the PFC, amygdala complexes, and the periaqueductal gray (PAG), a region related to defensive responses/emotional coping...
August 24, 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/28782543/the-active-construction-of-the-visual-world
#7
REVIEW
Thomas Parr, Karl J Friston
What we see is fundamentally dependent on where we look. Despite this seemingly obvious statement, many accounts of the neurobiology underpinning visual perception fail to consider the active nature of how we sample our sensory world. This review offers an overview of the neurobiology of visual perception, which begins with the control of saccadic eye movements. Starting from here, we can follow the anatomy backwards, to try to understand the functional architecture of neuronal networks that support the interrogation of a visual scene...
September 2017: Neuropsychologia
https://www.readbyqxmd.com/read/28777724/active-inference-curiosity-and-insight
#8
Karl J Friston, Marco Lin, Christopher D Frith, Giovanni Pezzulo, J Allan Hobson, Sasha Ondobaka
This article offers a formal account of curiosity and insight in terms of active (Bayesian) inference. It deals with the dual problem of inferring states of the world and learning its statistical structure. In contrast to current trends in machine learning (e.g., deep learning), we focus on how people attain insight and understanding using just a handful of observations, which are solicited through curious behavior. We use simulations of abstract rule learning and approximate Bayesian inference to show that minimizing (expected) variational free energy leads to active sampling of novel contingencies...
October 2017: Neural Computation
https://www.readbyqxmd.com/read/28702345/hierarchical-disruption-in-the-bayesian-brain-focal-epilepsy-and-brain-networks
#9
Amir Omidvarnia, Mangor Pedersen, Richard E Rosch, Karl J Friston, Graeme D Jackson
In this opinion paper, we describe a combined view of functional and effective brain connectivity along with the free-energy principle for investigating persistent disruptions in brain networks of patients with focal epilepsy. These changes are likely reflected in effective connectivity along the cortical hierarchy and construct the basis of increased local functional connectivity in focal epilepsy. We propose a testable framework based on dynamic causal modelling and functional connectivity analysis with the capacity of explaining commonly observed connectivity changes during interictal periods...
2017: NeuroImage: Clinical
https://www.readbyqxmd.com/read/28637913/predicting-green-really-radical-plant-predictive-processing
#10
Paco Calvo, Karl Friston
In this article we account for the way plants respond to salient features of their environment under the free-energy principle for biological systems. Biological self-organization amounts to the minimization of surprise over time. We posit that any self-organizing system must embody a generative model whose predictions ensure that (expected) free energy is minimized through action. Plants respond in a fast, and yet coordinated manner, to environmental contingencies. They pro-actively sample their local environment to elicit information with an adaptive value...
June 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/28607165/the-cumulative-effects-of-predictability-on-synaptic-gain-in-the-auditory-processing-stream
#11
Ryszard Auksztulewicz, Nicolas Barascud, Gerald Cooray, Anna Christina Nobre, Maria Chait, Karl Friston
Stimulus predictability can lead to substantial modulations of brain activity, such as shifts in sustained magnetic field amplitude, measured with magnetoencephalography (MEG). Here, we provide a mechanistic explanation of these effects using MEG data acquired from healthy human volunteers (N = 13, 7 female). In a source-level analysis of induced responses, we established the effects of orthogonal predictability manipulations of rapid tone-pip sequences (namely, sequence regularity and alphabet size) along the auditory processing stream...
July 12, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28576664/uncertainty-and-stress-why-it-causes-diseases-and-how-it-is-mastered-by-the-brain
#12
REVIEW
Achim Peters, Bruce S McEwen, Karl Friston
The term 'stress' - coined in 1936 - has many definitions, but until now has lacked a theoretical foundation. Here we present an information-theoretic approach - based on the 'free energy principle' - defining the essence of stress; namely, uncertainty. We address three questions: What is uncertainty? What does it do to us? What are our resources to master it? Mathematically speaking, uncertainty is entropy or 'expected surprise'. The 'free energy principle' rests upon the fact that self-organizing biological agents resist a tendency to disorder and must therefore minimize the entropy of their sensory states...
September 2017: Progress in Neurobiology
https://www.readbyqxmd.com/read/28554611/a-mathematical-model-of-embodied-consciousness
#13
David Rudrauf, Daniel Bennequin, Isabela Granic, Gregory Landini, Karl Friston, Kenneth Williford
We introduce a mathematical model of embodied consciousness, the Projective Consciousness Model (PCM), which is based on the hypothesis that the spatial field of consciousness (FoC) is structured by a projective geometry and under the control of a process of active inference. The FoC in the PCM combines multisensory evidence with prior beliefs in memory and frames them by selecting points of view and perspectives according to preferences. The choice of projective frames governs how expectations are transformed by consciousness...
May 26, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/28506713/the-emperor-s-new-topology-comment-on-topodynamics-of-metastable-brains-by-arturo-tozzi-et-al
#14
Karl Friston
No abstract text is available yet for this article.
May 11, 2017: Physics of Life Reviews
https://www.readbyqxmd.com/read/28486504/sequential-inference-as-a-mode-of-cognition-and-its-correlates-in-fronto-parietal-and-hippocampal-brain-regions
#15
Thomas H B FitzGerald, Dorothea Hämmerer, Karl J Friston, Shu-Chen Li, Raymond J Dolan
Normative models of human cognition often appeal to Bayesian filtering, which provides optimal online estimates of unknown or hidden states of the world, based on previous observations. However, in many cases it is necessary to optimise beliefs about sequences of states rather than just the current state. Importantly, Bayesian filtering and sequential inference strategies make different predictions about beliefs and subsequent choices, rendering them behaviourally dissociable. Taking data from a probabilistic reversal task we show that subjects' choices provide strong evidence that they are representing short sequences of states...
May 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28465538/how-doctors-diagnose-diseases-and-prescribe-treatments-an-fmri-study-of-diagnostic-salience
#16
Marcio Melo, Gustavo D F Gusso, Marcelo Levites, Edson Amaro, Eduardo Massad, Paulo A Lotufo, Peter Zeidman, Cathy J Price, Karl J Friston
Understanding the brain mechanisms involved in diagnostic reasoning may contribute to the development of methods that reduce errors in medical practice. In this study we identified similar brain systems for diagnosing diseases, prescribing treatments, and naming animals and objects using written information as stimuli. Employing time resolved modeling of blood oxygen level dependent (BOLD) responses enabled time resolved (400 milliseconds epochs) analyses. With this approach it was possible to study neural processes during successive stages of decision making...
May 2, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28416414/deep-temporal-models-and-active-inference
#17
REVIEW
Karl J Friston, Richard Rosch, Thomas Parr, Cathy Price, Howard Bowman
How do we navigate a deeply structured world? Why are you reading this sentence first - and did you actually look at the fifth word? This review offers some answers by appealing to active inference based on deep temporal models. It builds on previous formulations of active inference to simulate behavioural and electrophysiological responses under hierarchical generative models of state transitions. Inverting these models corresponds to sequential inference, such that the state at any hierarchical level entails a sequence of transitions in the level below...
June 2017: Neuroscience and Biobehavioral Reviews
https://www.readbyqxmd.com/read/28408874/editorial-mapping-psychopathology-with-fmri-and-effective-connectivity-analysis
#18
EDITORIAL
Baojuan Li, Adeel Razi, Karl J Friston
No abstract text is available yet for this article.
2017: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/28382008/a-goal-directed-bayesian-framework-for-categorization
#19
Francesco Rigoli, Giovanni Pezzulo, Raymond Dolan, Karl Friston
Categorization is a fundamental ability for efficient behavioral control. It allows organisms to remember the correct responses to categorical cues and not for every stimulus encountered (hence eluding computational cost or complexity), and to generalize appropriate responses to novel stimuli dependant on category assignment. Assuming the brain performs Bayesian inference, based on a generative model of the external world and future goals, we propose a computational model of categorization in which important properties emerge...
2017: Frontiers in Psychology
https://www.readbyqxmd.com/read/28345275/abnormal-frontoparietal-synaptic-gain-mediating-the-p300-in-patients-with-psychotic-disorder-and-their-unaffected-relatives
#20
Álvaro Díez, Siri Ranlund, Dimitris Pinotsis, Stella Calafato, Madiha Shaikh, Mei-Hua Hall, Muriel Walshe, Ángel Nevado, Karl J Friston, Rick A Adams, Elvira Bramon
The "dysconnection hypothesis" of psychosis suggests that a disruption of functional integration underlies cognitive deficits and clinical symptoms. Impairments in the P300 potential are well documented in psychosis. Intrinsic (self-)connectivity in a frontoparietal cortical hierarchy during a P300 experiment was investigated. Dynamic Causal Modeling was used to estimate how evoked activity results from the dynamics of coupled neural populations and how neural coupling changes with the experimental factors...
June 2017: Human Brain Mapping
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