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Karl Friston

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https://www.readbyqxmd.com/read/28637913/predicting-green-really-radical-plant-predictive-processing
#1
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
#2
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. 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...
June 8, 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
#3
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...
May 30, 2017: Progress in Neurobiology
https://www.readbyqxmd.com/read/28554611/a-mathematical-model-of-embodied-consciousness
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
https://www.readbyqxmd.com/read/28345153/the-functional-architectures-of-addition-and-subtraction-network-discovery-using-fmri-and-dcm
#12
Yang Yang, Ning Zhong, Karl Friston, Kazuyuki Imamura, Shengfu Lu, Mi Li, Haiyan Zhou, Haiyuan Wang, Kuncheng Li, Bin Hu
The neuronal mechanisms underlying arithmetic calculations are not well understood but the differences between mental addition and subtraction could be particularly revealing. Using fMRI and dynamic causal modeling (DCM), this study aimed to identify the distinct neuronal architectures engaged by the cognitive processes of simple addition and subtraction. Our results revealed significantly greater activation during subtraction in regions along the dorsal pathway, including the left inferior frontal gyrus (IFG), middle portion of dorsolateral prefrontal cortex (mDLPFC), and supplementary motor area (SMA), compared with addition...
June 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/28341164/expectation-violation-and-attention-to-pain-jointly-modulate-neural-gain-in-somatosensory-cortex
#13
Francesca Fardo, Ryszard Auksztulewicz, Micah Allen, Martin J Dietz, Andreas Roepstorff, Karl J Friston
The neural processing and experience of pain are influenced by both expectations and attention. For example, the amplitude of event-related pain responses is enhanced by both novel and unexpected pain, and by moving the focus of attention towards a painful stimulus. Under predictive coding, this congruence can be explained by appeal to a precision-weighting mechanism, which mediates bottom-up and top-down attentional processes by modulating the influence of feedforward and feedback signals throughout the cortical hierarchy...
June 2017: NeuroImage
https://www.readbyqxmd.com/read/28338892/embodiment-and-schizophrenia-a-review-of-implications-and-applications
#14
Wolfgang Tschacher, Anne Giersch, Karl Friston
In recent decades, embodiment has become an influential concept in psychology and cognitive neuroscience. Embodiment denotes the study of the reciprocal (causal) relationships between mind and body, with the mind not only affecting the body but also vice versa. Embodied cognition comes to the fore in sensorimotor coupling, predictive coding, and nonverbal behavior. Additionally, the embodiment of the mind constitutes the basis of social interaction and communication, as evident in research on nonverbal synchrony and mimicry...
March 3, 2017: Schizophrenia Bulletin
https://www.readbyqxmd.com/read/28334138/working-memory-modulation-of-frontoparietal-network-connectivity-in-first-episode-schizophrenia
#15
Jesper Duemose Nielsen, Kristoffer H Madsen, Zheng Wang, Zhening Liu, Karl J Friston, Yuan Zhou
Working memory (WM) impairment is regarded as a core aspect of schizophrenia. However, the neural mechanisms behind this cognitive deficit remain unclear. The connectivity of a frontoparietal network is known to be important for subserving WM. Using functional magnetic resonance imaging, the current study investigated whether WM-dependent modulation of effective connectivity in this network is affected in a group of first-episode schizophrenia (FES) patients compared with similarly performing healthy participants during a verbal n-back task...
February 25, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/28323165/on-the-importance-of-modeling-fmri-transients-when-estimating-effective-connectivity-a-dynamic-causal-modeling-study-using-asl-data
#16
Martin Havlicek, Alard Roebroeck, Karl J Friston, Anna Gardumi, Dimo Ivanov, Kamil Uludag
Effective connectivity is commonly assessed using blood oxygenation level-dependent (BOLD) signals. In (Havlicek et al., 2015), we presented a novel, physiologically informed dynamic causal model (P-DCM) that extends current generative models. We demonstrated the improvements afforded by P-DCM in terms of the ability to model commonly observed neuronal and vascular transients in single regions. Here, we assess the ability of the novel and previous DCM variants to estimate effective connectivity among a network of five ROIs driven by a visuo-motor task...
March 18, 2017: NeuroImage
https://www.readbyqxmd.com/read/28316456/functional-connectivity-of-the-pedunculopontine-nucleus-and-surrounding-region-in-parkinson-s-disease
#17
Ashwani Jha, Vladimir Litvak, Samu Taulu, Wesley Thevathasan, Jonathan A Hyam, Tom Foltynie, Patricia Limousin, Marko Bogdanovic, Ludvic Zrinzo, Alexander L Green, Tipu Z Aziz, Karl Friston, Peter Brown
Deep brain stimulation of the pedunculopontine nucleus and surrounding region (PPNR) is a novel treatment strategy for gait freezing in Parkinson's disease (PD). However, clinical results have been variable, in part because of the paucity of functional information that might help guide selection of the optimal surgical target. In this study, we use simultaneous magnetoencephalography and local field recordings from the PPNR in seven PD patients, to characterize functional connectivity with distant brain areas at rest...
January 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/28266640/corrigendum-perceptual-learning-to-discriminate-the-intensity-and-spatial-location-of-nociceptive-stimuli
#18
Flavia Mancini, Karina Dolgilevica, James Steckelmacher, Patrick Haggard, Karl Friston, Giandomenico D Iannetti
No abstract text is available yet for this article.
March 7, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28259780/regression-dcm-for-fmri
#19
Stefan Frässle, Ekaterina I Lomakina, Adeel Razi, Karl J Friston, Joachim M Buhmann, Klaas E Stephan
The development of large-scale network models that infer the effective (directed) connectivity among neuronal populations from neuroimaging data represents a key challenge for computational neuroscience. Dynamic causal models (DCMs) of neuroimaging and electrophysiological data are frequently used for inferring effective connectivity but are presently restricted to small graphs (typically up to 10 regions) in order to keep model inversion computationally feasible. Here, we present a novel variant of DCM for functional magnetic resonance imaging (fMRI) data that is suited to assess effective connectivity in large (whole-brain) networks...
March 1, 2017: NeuroImage
https://www.readbyqxmd.com/read/28240422/cerebellar-lobules-and-dentate-nuclei-mirror-cortical-force-related-bold-responses-beyond-all-linear-expectations
#20
Adnan A S Alahmadi, Matteo Pardini, Rebecca S Samson, Karl J Friston, Ahmed T Toosy, Egidio D'Angelo, Claudia A M Gandini Wheeler-Kingshott
The relationship between the BOLD response and an applied force was quantified in the cerebellum using a power grip task. To investigate whether the cerebellum responds in an on/off way to motor demands or contributes to motor responses in a parametric fashion, similarly to the cortex, five grip force levels were investigated under visual feedback. Functional MRI data were acquired in 13 healthy volunteers and their responses were analyzed using a cerebellum-optimized pipeline. This allowed us to evaluate, within the cerebellum, voxelwise linear and non-linear associations between cerebellar activations and forces...
May 2017: Human Brain Mapping
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