K Friston

..This finding substantially advances our understanding of striatal function and provides direct empirical evidence for formal learning theories that posit a central role for prediction error-dependent plasticity...

..I cannot imagine an alternative future that has the same beautiful self consistency as mine. Having dispensed with the future, we can now focus on the past, which is much more interesting:..

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..I accepted the invitation to write this review with great pleasure and hope to celebrate and critique the achievements to date, while addressing the challenges ahead...

..We use these simulations to demonstrate how a single functional role for dopamine at the synaptic level can manifest in different ways at the behavioural level...

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..Furthermore, it provides for dual and triple inferences on a system's states, parameters and hyperparameters using exactly the same principles. We refer to this approach as dynamic expectation maximisation (DEM)...

..This means the approach automatically selects either a sparse or a distributed model, depending on the data. The scheme is compared with conventional applications of Bayesian solutions to quantify the improvement in performance...

..We will look at the models entailed by the brain and how minimisation of its free energy can explain its dynamics and structure...

..Finally, we also consider, briefly, dynamic models and how these inform the regularisation of free energy ascent schemes, like EM and ReML...

..We conclude that localiser scans can be unnecessary and, in some instances, lead to a biased and inappropriately constrained characterisation of functional anatomy...

..This is the quantity that is optimized under the free-energy principle, which suggests that several global brain theories might be unified within a free-energy framework...

..The final focus of this article is on perceptual learning as measured with the MMN and the implications for empirical studies of coupling among cortical areas using evoked sensory responses...

..We illustrate MVB using simulated and real data, with a special focus on model comparison; where models can differ in the form of the mapping (i.e., neuronal representation) within one region, or in the (combination of) regions per se...

..By incorporating biophysical constraints, these basic models can be finessed and, in a dynamic setting, rendered causal. This allows us to infer how interactions among brain regions are mediated...

..psychophysiologic interactions). However, unlike previous approaches in neuroimaging, the causal model ascribes responses to designed deterministic inputs, as opposed to treating inputs as unknown and stochastic...

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..We illustrate the approach using general linear models and a more complicated nonlinear state-space model...

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..Our results affirm that a Bayes-optimal approach provides a principled framework, which accommodates current thinking about the mirror-neuron system. Furthermore, it endorses the general formulation of action as active inference...

..In short, the free-energy formulation may provide an alternative perspective on the motor control that places it in an intimate relationship with perception...

..e., hypothesis testing). We will refer to this theme, when trying to contextualise recent trends in relation to each other...

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..The ensuing proof-of-concept may be important because the free-energy formulation furnishes a unified account of both action and perception and may speak to a reappraisal of the role of dopamine in the brain...

..We then show that the brain has the necessary infrastructure to implement this inversion and present stimulations using synthetic birds that generate and recognise birdsongs...

..Furthermore, one can see easily how constructs like memory, attention, value, reinforcement and salience might disclose their simple relationships within this framework...

..We then show that the brain has the necessary infrastructure to implement this inversion and illustrate this point using synthetic birds that can recognize and categorize birdsongs...

..We then show that this inversion can be formulated as a simple neural network and may provide a useful metaphor for inference and learning in the brain...

..We then compare Bayesian and classical inference through the equivalent PPMs and SPMs testing for the same effect in the same data...

..The nonlinear nature of asynchronous coupling enables the rich, context-sensitive interactions that characterize real brain dynamics, suggesting that it plays an important role in functional integration...

..The examples considered include interactions between cognitive states and time (i.e. adaptation or plasticity in PET data) and among functionally specialized brain systems (using a fMRI study of colour and motion processing)...

..In short, the emergence of order, through selection, depends almost paradoxically on the instabilities that characterize the diversity of brain dynamics. The second perspective is provided by information theory...

..The example considers interactions among functionally specialized brain systems (using a fMRI study of colour and motion processing)...

..The conclusion of these studies points toward the prevalence of top-down influences and the plausibility of generative models of sensory brain function...

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..These results speak to the context-sensitive nature of functional integration in the brain and provide empirical evidence that attentional effects may be mediated by backwards connections, of a modulatory sort, in humans...

..g. cross-correlograms and coherence). Using neuromagnetic data it is shown that nonlinear (asynchronous) coupling is, in fact, more abundant and can be more significant than synchronous coupling...

..The advantage of the current test is that it eschews a correction for multiple comparisons even though the exact location of the expected activation may not be known...

..The conclusion, from these sorts of neuroimaging studies, points to the prevalence of top-down influences and the plausibility of generative models of sensory brain function...

..We focus on interactions among extrastriate, inferotemporal, and posterior parietal regions during visual processing, under different attentional and perceptual conditions...

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..The proposed pathophysiology would translate, in functional terms, into a disruption of the reinforcement of adaptive behaviour that is consistent with the disintegrative aspects of schizophrenic neuropsychology...

..Here we focus on the implications for cognitive neuroscience in the context of neuroimaging...

..A further benefit of the MAR approach is that connectivity maps may contain loops, yet exact inference can proceed within a linear framework. Model order selection and parameter estimation are implemented by using Bayesian methods...

..These examples show that category- or context-specific coupling among cortical regions can be assessed explicitly, within a mechanistic, biologically motivated inference framework...

..This interaction is expressed as a phase-resetting and represents a qualitatively different explanation for the ERP/ERF...

..It is remarkable that distinct changes in intrinsic and extrinsic connections could be quantified so reliably and non-invasively using EEG...

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..Our results provide empirical evidence for nonlinear coupling among distributed neuronal sources in the motor system and that these play an important role in modulating spectral responses under normal conditions...

..An experiment on a subject performing voluntary movements in the scanner yielded plausible estimates of the deformation fields and their application to "unwarp" the time series significantly reduced movement-related variance...

..This study provides in vivo evidence that experience-dependent plasticity, evident in hemodynamic changes in human auditory cortex, is modulated by acetylcholine...

..Furthermore, we show that the error variance can change with the experimental design. This highlights a problem with a priori comparison of efficiency for two or more experimental designs, which usually assumes identical error variance...

..We report preliminary results that focus on the assumed stochastic nature of the neurodynamic model and compare the method to Wiener deconvolution...

..We introduce adjusted power to complement induced power. Adjusted power is unaffected by trial-to-trial variations in input and can be attributed to structural perturbations without ambiguity...

..This paper presents a review of studies that focus on neuronal mechanisms underlying the MMN generation, discusses the two major explanatory hypotheses, and proposes predictive coding as a general framework that attempts to unify both...

..Our study confirms a prediction of theories of brain function that depend on convergence zones; the absence of one input (that is, visual) does not alter the response properties of such a convergence region...

..The advantage of the new estimator is that it is not informed of experimental design and relies only on general assumptions regarding the nature of the signal...

..For example, whether activity is driven by master-slave versus mutual entrainment mechanisms. Results are presented on synthetic data from physiological models and on MEG data from a study of visual working memory...

..Finally, we present an illustrative application using an fMRI study of visual attention...

..These results suggest that semantic decisions on auditory-visual compound stimuli might be accomplished by two overlapping degenerate neuronal systems...

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..To illustrate the method, we compared the gross morphometry of male and female subjects. We also assessed brain asymmetry, the effect of handedness, and interactions among these effects...

..This more general conjunction test is described...

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..Ilmoniemi, R.J., Levänen, S., Lin, F.H., May, P., Melcher, J., Stufflebeam, S., Tiitinen, H., Belliveau, J.W., 2004. Human posterior auditory cortex gates novel sounds to consciousness. Proc. Natl. Acad. Sci. U. S. A. 101, 6809-6814]...

..Rather, these processes seem to rely on the ventral visual stream, the ventral prefrontal cortex and the anterior part of the dorsal premotor cortex...

..We interpret our findings in terms of a left frontal system mediating the semantic analysis of study items and directly influencing a right fronto-parietal system associated with episodic memory retrieval...

..These findings confirm that the short-term adaptation to a simple motor task is a physiological process which is preserved in MS...

..These results posit a dual role for prediction-error in encoding surprise and driving associative plasticity...

..g. comparing different source reconstruction methods for EEG/MEG or selecting among competing computational models of learning and decision-making...

..In contrast, deficits in functional integration are implied when the influence of one brain region on another is stronger or weaker in patients relative to control subjects...

..The framework provides predictions about, and principled constraints on, cortical structure-function relationships, which can be tested by manipulating the time-scales of sensory input...

..Task-related, directional effects can now be incorporated into models of speech comprehension...

..Commensurate effects were observed in reaction times. We suggest that motor output is biased according to contextual probabilities that are represented dynamically in the brain...

..This pattern of responses is consistent with that predicted by mirror neurons and is evidence of mirror neurons in the human IFG...

..g. grey and white matter) are registered simultaneously with the current template estimate. In order to generalise the resulting template to a broader range of subjects, a template blurriness prior is included within the model...

..By presenting anomalous stimuli, we find that the resulting recognition dynamics disclose inference at multiple time scales and are reminiscent of neuronal dynamics seen in the real brain...

..We suggest our approach provides greater flexibility in analysing SCRs than existing methods...

..Our findings demonstrate that physiologically meaningful information can be extracted from heavily contaminated MEG signals and pave the way for further analysis of combined MEG-LFP recordings in DBS patients...

..We develop a canonical response function and show that it can be used for signals from different recording sites. We discuss the implications of these observations for model-based analysis of SCRs...

..Here, we describe the distributed spatial model and present a comparative evaluation with conventional equivalent current dipole (ECD) models of auditory processing, as measured with EEG...

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..We suggest that DCM and Bayesian model comparison provides a useful way to test hypotheses about distributed processing in the brain, using electromagnetic data...

..We demonstrate the validity of this measure in relation to finite impulse response models, and show that it is a better predictor of autonomic arousal, relative to conventional measures...

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..It is shown that this procedure offers various advantages compared to existing conventional methods for the analysis of multisubject studies, in particular it is more sensitive to underlying activations...

..This is the theoretical cornerstone of most modern theories of perceptual inference and learning...

..We demonstrate the reciprocal participation of focal thalamic and widespread cortical networks during human absence seizures and suggest reductions in cortical blood flow, in response to synchronized electroencephalogram activity...

..The present investigation is the first to identify distinct neuronal mechanisms for semantic and phonological contributions to reading...

..The coordinated variations we report are likely to be determined by both genetic and environmental factors and may be the basis for differences in individual behavior...

..A strategy for optimising the model parameters is described, along with the requisite partial derivatives of the objective function...

..This, in turn, has important implications for understanding the mechanisms that mediate recovery and the organizational principles that underlie functional architectures in the human brain...

..The discussion focuses on the implications of our findings and on further applications of the multisubject network analysis...

..We establish the validity of parametric tests using synthetic and real data and compare its performance to established nonparametric procedures...

..In short, we show that the probabilistic structure or context in which events occur is an important predictor of hippocampal activity...

..J. Neurosci. 23, 5308-5318.) by providing evidence that the pattern of acute reorganization in the motor network following rTMS depends on the direction of conditioning...

..Here, by analysing the time-frequency decompositions of single channel EEG data we show that RFT adjustments can be used in the analysis of electrophysiological data and illustrate the advantages of this method over existing approaches...

..Our model generalizes earlier work on voxel-wise estimation of GLM-AR models and inference in GLMs using Posterior Probability Maps (PPMs). Results are shown on simulated data and on data from an event-related fMRI experiment...

..Our data support an integrative architecture for decision making, revealing the neural representation of distinct subcomponents of value that may contribute to impulsivity and decisiveness...