Publications of year 2011
  1. Stanislas DEHAENE. The number sense (2nd edition).. New York: Oxford University Press, 2011. [bibtex-entry]

  2. Stanislas Dehaene. Apprendre à lire. Des sciences cognitives à la salle de classe. Odile Jacob, 2011. [WWW] [bibtex-entry]

  3. Caroline Huron. L'enfant dyspraxique: Mieux l'aider à la maison et à l'école. Odile Jacob, 2011. [WWW] [bibtex-entry]

  4. Stanislas Dehaene and Christen Y., editors. Characterizing Consciousness: From Cognition to the Clinic?. Springer-Verlag, 2011. [bibtex-entry]

  5. Stanislas Dehaene and Elizabeth Brannon, editors. Space, Time and Number in the Brain. Searching for the Foundations of Mathematical Thought. Academic Press, 2011. [WWW] [bibtex-entry]

  1. Francois Leroy. Etude Méthodologique et Structurale du Développement Cérébral en IRM : Application aux Aires du Langage dans une Population de Nourrissons. PhD thesis, 2011. [WWW] [bibtex-entry]

  2. Karla Monzalvo. Etude chez l'enfant normal et dyslexique de l'impact sur les réseaux corticaux visuel et linguistique d'une activité culturelle : la lecture. PhD thesis, 2011. [bibtex-entry]

  3. Felipe Pegado. Impact de l'alphabétisation sur l'organisation cérébrale et la cognition: aspects de la perception visuelle et du langage parlé chez les adultes alphabétisés et non-alphabétisés.. PhD thesis, UPMC, 2011. [bibtex-entry]

Book chapters
  1. Mariano Sigman and Stanislas Dehaene. Why does it take time to make a decision? The role of a global workspace in simple decision making, chapter one, pages 11-44. Psychology Press, 2011. [PDF] [bibtex-entry]

  2. A Bénézit, L Hertz-Pannier, G Dehaene-Lambertz, and J Dubois. Le corps calleux : sa vie précoce, son ?uvre tardive. In Les malformations congénitales. Diagnostic anténatal et devenir. Tome 6. Sauramps Médical. Suite au 5ème Congrès de Médecine F?tale : Diagnostic Anténatal et Devenir. 2011. [PDF] [bibtex-entry]

  3. Stanislas Dehaene, Changeux JP, and Naccache L. The Global Neuronal Workspace Model of Conscious Access: From Neuronal Architectures to Clinical Applications.. In Characterizing Consciousness: From Cognition to the Clinic?. Springer-Verlag, 2011. [bibtex-entry]

  4. Stanislas Dehaene. Reading as Neuronal Recycling. In Dyslexia Across Languages, pages 102-16. P. McCardle, B. Miller, J.R. Lee, O. J.L. Tzeng (Eds), Paul H. Brookes Publishing, 2011. [bibtex-entry]

  5. Veronique Izard, Pierre Pica, Stanislas Dehaene, Danielle Hinchey, and Elizabeth Spelke. Geometry as a Universal Mental Construction. In Space, Time and Number in the Brain,. Stanislas Dehaene; Elizabeth Brannon (Ed.) (2011) 319-332, 2011. [bibtex-entry]

  6. Manuela Piazza. Neurocognitive Start-Up Tools for Symbolic Number Representations. In Space, Time and Number in the Brain. Searching for the Foundations of Mathematical Thought. Academic Press, 2011. [bibtex-entry]

Articles in journals
  1. Jessica F Cantlon, Philippe Pinel, Stanislas Dehaene, and Kevin A Pelphrey. Cortical representations of symbols, objects, and faces are pruned back during early childhood.. Cereb Cortex, 21(1):191--199, January 2011. [WWW]
    Abstract: Regions of human ventral extrastriate visual cortex develop specializations for natural categories (e.g., faces) and cultural artifacts (e.g., words). In adults, category-based specializations manifest as greater neural responses in visual regions of the brain (e.g., fusiform gyrus) to some categories over others. However, few studies have examined how these specializations originate in the brains of children. Moreover, it is as yet unknown whether the development of visual specializations hinges on "increases" in the response to the preferred categories, "decreases" in the responses to nonpreferred categories, or "both." This question is relevant to a long-standing debate concerning whether neural development is driven by building up or pruning back representations. To explore these questions, we measured patterns of visual activity in 4-year-old children for 4 categories (faces, letters, numbers, and shoes) using functional magnetic resonance imaging. We report 2 key findings regarding the development of visual categories in the brain: 1) the categories "faces" and "symbols" doubly dissociate in the fusiform gyrus before children can read and 2) the development of category-specific responses in young children depends on cortical responses to nonpreferred categories that decrease as preferred category knowledge is acquired.

  2. Clio P Coste, Sepideh Sadaghiani, Karl J Friston, and Andreas Kleinschmidt. Ongoing brain activity fluctuations directly account for intertrial and indirectly for intersubject variability in Stroop task performance.. Cereb Cortex, 21(11):2612--2619, November 2011. [WWW]
    Abstract: Recent studies have established a relation between ongoing brain activity fluctuations and intertrial variability in evoked neural responses, perception, and motor performance. Here, we extended these investigations into the domain of cognitive control. Using functional neuroimaging and a sparse event-related design (with long and unpredictable intervals), we measured ongoing activity fluctuations and evoked responses in volunteers performing a Stroop task with color-word interference. Across trials, prestimulus activity of several regions predicted subsequent response speed and across subjects this effect scaled with the Stroop effect size, being significant only in subjects manifesting behavioral interference. These effects occurred only in task relevant as the dorsal anterior cingulate and dorsolateral prefrontal cortex as well as ventral visual areas sensitive to color and visual words. Crucially, in subjects showing a Stroop effect, reaction times were faster when prestimulus activity was higher in task-relevant (color) regions and slower when activity was higher in irrelevant (word form) regions. These findings suggest that intrinsic brain activity fluctuations modulate neural mechanisms underpinning selective voluntary attention and cognitive control. Rephrased in terms of predictive coding models, ongoing activity can hence be considered a proxy of the precision (gain) with which prediction error signals are transmitted upon sensory stimulation.

  3. Floris P de Lange, Simon van Gaal, Victor A F Lamme, and Stanislas Dehaene. How awareness changes the relative weights of evidence during human decision-making.. PLoS Biol, 9(11):e1001203, November 2011. [WWW] [PDF]
    Abstract: Human decisions are based on accumulating evidence over time for different options. Here we ask a simple question: How is the accumulation of evidence affected by the level of awareness of the information? We examined the influence of awareness on decision-making using combined behavioral methods and magneto-encephalography (MEG). Participants were required to make decisions by accumulating evidence over a series of visually presented arrow stimuli whose visibility was modulated by masking. Behavioral results showed that participants could accumulate evidence under both high and low visibility. However, a top-down strategic modulation of the flow of incoming evidence was only present for stimuli with high visibility: once enough evidence had been accrued, participants strategically reduced the impact of new incoming stimuli. Also, decision-making speed and confidence were strongly modulated by the strength of the evidence for high-visible but not low-visible evidence, even though direct priming effects were identical for both types of stimuli. Neural recordings revealed that, while initial perceptual processing was independent of visibility, there was stronger top-down amplification for stimuli with high visibility than low visibility. Furthermore, neural markers of evidence accumulation over occipito-parietal cortex showed a strategic bias only for highly visible sensory information, speeding up processing and reducing neural computations related to the decision process. Our results indicate that the level of awareness of information changes decision-making: while accumulation of evidence already exists under low visibility conditions, high visibility allows evidence to be accumulated up to a higher level, leading to important strategical top-down changes in decision-making. Our results therefore suggest a potential role of awareness in deploying flexible strategies for biasing information acquisition in line with one's expectations and goals.

  4. Stanislas Dehaene and Jean-Pierre Changeux. Experimental and theoretical approaches to conscious processing.. Neuron, 70(2):200--227, April 2011. [WWW] [PDF]
    Abstract: Recent experimental studies and theoretical models have begun to address the challenge of establishing a causal link between subjective conscious experience and measurable neuronal activity. The present review focuses on the well-delimited issue of how an external or internal piece of information goes beyond nonconscious processing and gains access to conscious processing, a transition characterized by the existence of a reportable subjective experience. Converging neuroimaging and neurophysiological data, acquired during minimal experimental contrasts between conscious and nonconscious processing, point to objective neural measures of conscious access: late amplification of relevant sensory activity, long-distance cortico-cortical synchronization at beta and gamma frequencies, and "ignition" of a large-scale prefronto-parietal network. We compare these findings to current theoretical models of conscious processing, including the Global Neuronal Workspace (GNW) model according to which conscious access occurs when incoming information is made globally available to multiple brain systems through a network of neurons with long-range axons densely distributed in prefrontal, parieto-temporal, and cingulate cortices. The clinical implications of these results for general anesthesia, coma, vegetative state, and schizophrenia are discussed.

  5. Stanislas Dehaene and Laurent Cohen. The unique role of the visual word form area in reading.. Trends Cogn Sci, May 2011, 17 May. [WWW]
    Abstract: Reading systematically activates the left lateral occipitotemporal sulcus, at a site known as the visual word form area (VWFA). This site is reproducible across individuals/scripts, attuned to reading-specific processes, and partially selective for written strings relative to other categories such as line drawings. Lesions affecting the VWFA cause pure alexia, a selective deficit in word recognition. These findings must be reconciled with the fact that human genome evolution cannot have been influenced by such a recent and culturally variable activity as reading. Capitalizing on recent functional magnetic resonance imaging experiments, we provide strong corroborating evidence for the hypothesis that reading acquisition partially recycles a cortical territory evolved for object and face recognition, the prior properties of which influenced the form of writing systems.

  6. Jessica Dubois, G Dehaene-Lambertz, JF Mangin, D. Le Bihan, PS Hüppi, and L Hertz-Pannier. Développement cérébral du nourrisson et Imagerie par Résonance Magnétique. Neurophysiologie Clinique / Clinical Neurophysiology, 2011. [PDF] [bibtex-entry]

  7. Zhao Fan, Krish Singh, Suresh Muthukumaraswamy, Mariano Sigman, Stanislas Dehaene, and Kimron Shapiro. The cost of serially chaining two cognitive operations.. Psychol Res, August 2011. [WWW]
    Abstract: As Turing (1936, Proceedings of the London Mathematical Society) noted, a fundamental process in human cognition is to effect chained sequential operations in which the second operation requires an input from the preceding one. Although a great deal is known about the costs associated with 'independent' (unrelated) operations, e.g., from the classic psychological refractory period paradigm, far less is known about those operations to which Turing referred. We present the results of two behavioural experiments, where participants were required to perform two speeded sequential tasks that were either chained or independent. Both experiments reveal the reaction time cost of chaining, over and above classical dual-task serial costs. Moreover, the chaining operation significantly altered the distribution of reaction times relative to the Independent condition in terms of an increased mean and variance. These results are discussed in terms of the cognitive architecture underlying the serial chaining of cognitive operations.

  8. Frédéric Faugeras, Benjamin Rohaut, Nicolas Weiss, Tristan A Bekinschtein, Damien Galanaud, Louis Puybasset, Francis Bolgert, Claire Sergent, Laurent Cohen, Stanislas Dehaene, and Lionel Naccache. Probing consciousness with event-related potentials in patients who meet clinical criteria for vegetative state. Neurology, 2011, May 18. [bibtex-entry]

  9. Ludovic Ferrand, Marc Brysbaert, Emmanuel Keuleers, Boris New, Patrick Bonin, Alain Meot, Maria Augustinova, and Christophe Pallier. Comparing word processing times in naming, lexical decision, and progressive demasking: evidence from chronolex.. Front Psychol, 2:306, 2011. [WWW] [PDF]
    Abstract: We report performance measures for lexical decision (LD), word naming (NMG), and progressive demasking (PDM) for a large sample of monosyllabic monomorphemic French words (N?=?1,482). We compare the tasks and also examine the impact of word length, word frequency, initial phoneme, orthographic and phonological distance to neighbors, age-of-acquisition, and subjective frequency. Our results show that objective word frequency is by far the most important variable to predict reaction times in LD. For word naming, it is the first phoneme. PDM was more influenced by a semantic variable (word imageability) than LD, but was also affected to a much greater extent by perceptual variables (word length, first phoneme/letters). This may reduce its usefulness as a psycholinguistic word recognition task.

  10. H. Glasel, F. Leroy, J. Dubois, L. Hertz-Pannier, J. F. Mangin, and G. Dehaene-Lambertz. A robust cerebral asymmetry in the infant brain: The rightward superior temporal sulcus.. Neuroimage, 58(3):716--723, October 2011. [WWW] [PDF]
    Abstract: In order to understand how genetic mutations might have favored language development in our species, we need a better description of the human brain at the beginning of life. As the linguistic network mainly involves the left perisylvian regions in adults, we used anatomical MRI to study the structural asymmetries of these regions in 14 preverbal infants. Our results show four significant asymmetries. First and foremost, they stress an important but little-known asymmetry: the larger depth of the right superior temporal sulcus (STS) at the base of Heschl's gyrus. Then, we characterized the early forward and upward shift of the posterior end of the right Sylvian fissure, the elongation of the left planum temporale as well as the thickening of the left Heschl's gyrus. The rightward bias of the STS is robust and large, and is not correlated with the leftward asymmetries of the planum and Heschl's gyrus, suggesting that different morphogenetic factors drive these asymmetries. As this sulcus is engaged in multiple high-level functions (e.g. language and theory of mind), and has been spotted as abnormal in several developmental disorders (e.g. schizophrenia, autism), this early rightward asymmetry should be further explored as a target for a genetic evolutionary pressure.

  11. G. Hesselmann, G. Flandin, and S. Dehaene. Probing the cortical network underlying the psychological refractory period: A combined EEG-fMRI study.. Neuroimage, March 2011. [WWW]
    Abstract: Human performance exhibits strong multi-tasking limitations in simple response time tasks. In the psychological refractory period (PRP) paradigm, where two tasks have to be performed in brief succession, central processing of the second task is delayed when the two tasks are performed at short time intervals. Here, we aimed to probe the cortical network underlying this postponement of central processing by simultaneously recording electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data while 12 subjects performed two simple number-comparison tasks. Behavioral data showed a significant slowing of response times to the second target stimulus at short stimulus-onset asynchronies, together with significant correlations between response times to the first and second target stimulus, i.e., the hallmarks of the PRP effect. The analysis of EEG data showed a significant delay of the post-perceptual P3 component evoked by the second target, which was of similar magnitude as the effect on response times. fMRI data revealed an involvement of parietal and prefrontal regions in dual-task processing. The combined analysis of fMRI and EEG data-based on the trial-by-trial variability of the P3-revealed that BOLD signals in two bilateral regions in the inferior parietal lobe and precentral gyrus significantly covaried with P3 related activity. Our results show that combining neuroimaging methods of high spatial and temporal resolutions can help to identify cortical regions underlying the central bottleneck of information processing, and strengthen the conclusion that fronto-parietal cortical regions participate in a distributed "global neuronal workspace" system that underlies the generation of the P3 component and may be one of the key cerebral underpinnings of the PRP bottleneck.

  12. Véronique Izard, Pierre Pica, Elizabeth S Spelke, and Stanislas Dehaenee. Flexible intuitions of Euclidean geometry in an Amazonian indigene group.. Proc Natl Acad Sci U S A, May 2011. [WWW] [PDF]
    Abstract: Kant argued that Euclidean geometry is synthesized on the basis of an a priori intuition of space. This proposal inspired much behavioral research probing whether spatial navigation in humans and animals conforms to the predictions of Euclidean geometry. However, Euclidean geometry also includes concepts that transcend the perceptible, such as objects that are infinitely small or infinitely large, or statements of necessity and impossibility. We tested the hypothesis that certain aspects of nonperceptible Euclidian geometry map onto intuitions of space that are present in all humans, even in the absence of formal mathematical education. Our tests probed intuitions of points, lines, and surfaces in participants from an indigene group in the Amazon, the Mundurucu, as well as adults and age-matched children controls from the United States and France and younger US children without education in geometry. The responses of Mundurucu adults and children converged with that of mathematically educated adults and children and revealed an intuitive understanding of essential properties of Euclidean geometry. For instance, on a surface described to them as perfectly planar, the Mundurucu's estimations of the internal angles of triangles added up to ?180 degrees, and when asked explicitly, they stated that there exists one single parallel line to any given line through a given point. These intuitions were also partially in place in the group of younger US participants. We conclude that, during childhood, humans develop geometrical intuitions that spontaneously accord with the principles of Euclidean geometry, even in the absence of training in mathematics.

  13. Juan E Kamienkowski, Harold Pashler, Stanislas Dehaene, and Mariano Sigman. Effects of practice on task architecture: Combined evidence from interference experiments and random-walk models of decision making.. Cognition, February 2011. [WWW]
    Abstract: Does extensive practice reduce or eliminate central interference in dual-task processing? We explored the reorganization of task architecture with practice by combining interference analysis (delays in dual-task experiment) and random-walk models of decision making (measuring the decision and non-decision contributions to RT). The main delay observed in the Psychologically Refractory Period at short stimulus onset asynchronies (SOA) values was largely unaffected by training. However, the range of SOAs over which this interference regime held diminished with learning. This was consistent with an overall shift observed in single-task performance from a highly variable decision time to a reliable (non-decision time) contribution to response time. Executive components involved in coordinating dual-task performance decreased (and became more stable) after extensive practice. The results suggest that extensive practice reduces the duration of central decision stages, but that the qualitative property of central seriality remains a structural invariant.

  14. Jean-Rémi King, Tristan Bekinschtein, and Stanislas Dehaene. Comment on preserved feedforward but impaired top-down processes in the vegetative state.. Science, 334(6060):1203, December 2011. [WWW] [PDF]
    Abstract: Boly et al. (Reports, 13 May 2011, p. 858) investigated cortical connectivity patterns in patients suffering from a disorder of consciousness, using electroencephalography in an auditory oddball paradigm. We point to several inconsistencies in their data, including a failure to replicate the classical mismatch negativity. Data quality, source reconstruction, and statistics would need to be improved to support their conclusions.

  15. Andreas Kleinschmidt. [Recovering the contents of consciousness in the noise of neuroimaging.]. Med Sci (Paris), 27(2):199--203, February 2011. [WWW] [PDF]
    Abstract: A classical approach in the neurosciences is to study neural activity modulations induced by a stimulus, a task, etc. This approach is anchored in a behaviourist culture and has proven informative within certain limits. The present paper shows that this approach nonetheless neglects aspects of neural activity that can also contribute important information about brain function. Over the last years, the contributions with the strongest impact on progress in cognitive neuroscience have used other approaches that exploit a spatial or temporal variability of neural activity that standard analyses consider as noise and hence do not take into account. By applying multi-variate analyses, spatial variability of evoked responses has permitted decoding sensory and cognitive representations in the brain. Temporal variability of ongoing neural activity influences how stimuli are perceived trial by trial as well as the associated evoked responses which points out the importance of spontaneous brain activity for cognition. We describe these two kind of approaches based on experiments using functional neuroimaging but the conclusions generalize to other techniques applied in the neurosciences.

  16. Andreas Kleinschmidt and Elena Rusconi. Gerstmann Meets Geschwind: A Crossing (or Kissing) Variant of a Subcortical Disconnection Syndrome?. Neuroscientist, June 2011, June 13. [WWW]
    Abstract: That disconnection causes clinical symptoms is a very influential concept in behavioral neurology. Criteria for subcortical disconnection usually are symptoms that are distinct from those following cortical lesions and damage to a single, long-range fiber tract. Yet, a recent study combining functional magnetic resonance imaging and fiber tracking concluded that a focal lesion in left parietal white matter provides the only tenable explanation for pure Gerstmann's syndrome, an enigmatic tetrad of acalculia, agraphia, finger agnosia, and left-right disorientation. Such a lesion would affect not only a single fiber tract but crossing or "kissing" of different fiber tracts and hence disconnect separate cortical networks. As fiber crossing is prominent in the cerebral white matter, the authors propose an extension to the subcortical disconnection framework that opens the door to ascribing a more diversified clinical phenomenology to white matter damage and ensuing disconnection than has been the case so far.

  17. François Leroy, Hervé Glasel, Jessica Dubois, Lucie Hertz-Pannier, Bertrand Thirion, Jean-François Mangin, and Ghislaine Dehaene-Lambertz. Early Maturation of the Linguistic Dorsal Pathway in Human Infants.. J Neurosci, 31(4):1500--1506, January 2011. [WWW] [PDF]
    Abstract: Human infants, unlike even closely related primates, exhibit a remarkable capacity for language learning. Yet how the underlying anatomical network matures remains largely unknown. The classical view is that of a largely immature brain comprising only a few islands of maturity in primary cortices. This view has favored a description of learning based on bottom-up algorithms and has tended to discard the role of frontal regions, which were assumed to be barely functional early on. Here, using an index based on the normalized T2-weighted magnetic resonance signal, we have quantified maturation within the linguistic network in fourteen 1- to 4-month-old infants. Our results show first that the ventral superior temporal sulcus (STS), and not the inferior frontal area, is the less mature perisylvian region. A significant difference of maturation in the STS favoring the right side is an early testimony of the distinctive left-right development of this structure observed during the whole life. Second, asymmetries of maturation in Broca's area were correlated with asymmetries in the posterior STS and in the parietal segment of the arcuate fasciculus, suggesting that an efficient frontotemporal dorsal pathway might provide infants with a phonological loop circuitry much earlier than expected.

  18. Francois Leroy, JF Mangin, François Rousseau, Hervé Glasel, L. Hertz-Pannier, Jessica Dubois, and Ghislaine Dehaene-Lambertz. Atlas-Free Surface Reconstruction of the Cortical Grey-White Interface in Infants. PLoS One, 6, 2011. [bibtex-entry]

  19. Henry MARKRAM, Karlheinz MEIER, Thomas LIPPERT, Sten GRILLNER, Richard FRACKOWIAK, Stanislas DEHAENE, Alois KNOLL, Haim SOMPOLINSKY, Kris VERSTREKEN, Javier DEFELIPE, Seth GRANT, Jean-Pierre CHANGEUX., and Alois SARIAM. Introducing the Human Brain Project.. Procedia Computer Science, 2011. [PDF] [bibtex-entry]

  20. Clara D. Martin, Jean-Yves Baudouin, Nicolas Franck, Fabrice Guillaume, François Guillem, Caroline Huron, and Guy Tiberghien. Comparison of RK and Confidence Judgment ROCs in Recognition Memory. European Journal of Cognitive Psychology, 23:171-84, 2011. [bibtex-entry]

  21. Clara D Martin, Jean-Yves Baudouin, Nicolas Franck, Fabrice Guillaume, François Guillem, Guy Tiberghien, and Caroline Huron. Impairment not only in remembering but also in knowing previously seen faces and words in schizophrenia.. Psychiatry Res, January 2011. [WWW]
    Abstract: Patients with schizophrenia have pronounced deficits in face recognition memory that severely hamper their social skills. The functional mechanisms of these impairments remain unknown. According to the dual-process theory, recognition memory comprises two distinct components: recollection and familiarity. Studies using the Remember/Know procedure in patients with schizophrenia showed impairments in conscious recollection as measured by remember responses, but not in familiarity as measured by know responses. Unfortunately, none of these studies used face material. We investigated both recognition memory components using words and faces and the 'Remember/Know' procedure in 25 patients with schizophrenia and 24 control participants. In the same task, size congruency of stimuli was manipulated between the study and test phases to have a selective impact on know responses for faces. Patients reported fewer remember responses than controls. Size changes between the study and the test affected know responses in controls but not in patients. These results reveal that patients with schizophrenia are impaired in terms of their ability to recollect details about previously seen faces as they are for words.

  22. David Melcher and Manuela Piazza. The role of attentional priority and saliency in determining capacity limits in enumeration and visual working memory.. PLoS One, 6(12):e29296, 2011. [WWW]
    Abstract: Many common tasks require us to individuate in parallel two or more objects out of a complex scene. Although the mechanisms underlying our abilities to count the number of items, remember the visual properties of objects and to make saccadic eye movements towards targets have been studied separately, each of these tasks require selection of individual objects and shows a capacity limit. Here we show that a common factor-salience-determines the capacity limit in the various tasks. We manipulated bottom-up salience (visual contrast) and top-down salience (task relevance) in enumeration and visual memory tasks. As one item became increasingly salient, the subitizing range was reduced and memory performance for all other less-salient items was decreased. Overall, the pattern of results suggests that our abilities to enumerate and remember small groups of stimuli are grounded in an attentional priority or salience map which represents the location of important items.

  23. Vincent Michel, Evelyn Eger, Christine Keribin, and Bertrand Thirion. Multiclass Sparse Bayesian Regression for fMRI-Based Prediction.. Int J Biomed Imaging, 2011:350838, 2011. [WWW]
    Abstract: Inverse inference has recently become a popular approach for analyzing neuroimaging data, by quantifying the amount of information contained in brain images on perceptual, cognitive, and behavioral parameters. As it outlines brain regions that convey information for an accurate prediction of the parameter of interest, it allows to understand how the corresponding information is encoded in the brain. However, it relies on a prediction function that is plagued by the curse of dimensionality, as there are far more features (voxels) than samples (images), and dimension reduction is thus a mandatory step. We introduce in this paper a new model, called Multiclass Sparse Bayesian Regression (MCBR), that, unlike classical alternatives, automatically adapts the amount of regularization to the available data. MCBR consists in grouping features into several classes and then regularizing each class differently in order to apply an adaptive and efficient regularization. We detail these framework and validate our algorithm on simulated and real neuroimaging data sets, showing that it performs better than reference methods while yielding interpretable clusters of features.

  24. Vincent Michel, Alexandre Gramfort, Gaël Varoquaux, Evelyn Eger, and Bertrand Thirion. Total variation regularization for fMRI-based prediction of behavior.. IEEE Trans Med Imaging, 30(7):1328--1340, July 2011. [WWW]
    Abstract: While medical imaging typically provides massive amounts of data, the extraction of relevant information for predictive diagnosis remains a difficult challenge. Functional magnetic resonance imaging (fMRI) data, that provide an indirect measure of task-related or spontaneous neuronal activity, are classically analyzed in a mass-univariate procedure yielding statistical parametric maps. This analysis framework disregards some important principles of brain organization: population coding, distributed and overlapping representations. Multivariate pattern analysis, i.e., the prediction of behavioral variables from brain activation patterns better captures this structure. To cope with the high dimensionality of the data, the learning method has to be regularized. However, the spatial structure of the image is not taken into account in standard regularization methods, so that the extracted features are often hard to interpret. More informative and interpretable results can be obtained with the l(1) norm of the image gradient, also known as its total variation (TV), as regularization. We apply for the first time this method to fMRI data, and show that TV regularization is well suited to the purpose of brain mapping while being a powerful tool for brain decoding. Moreover, this article presents the first use of TV regularization for classification.

  25. Andrea Mognon, Lorenzo Bruzzone, Jorge Jovicich, and Marco Buiatti. ADJUST: An Automatic EEG artifact Detector based on the Joint Use of Spatial and Temporal features. Psychophysiology, 48:229-40, 2011. [bibtex-entry]

  26. Christophe Pallier, Anne-Dominique Devauchelle, and Stanislas Dehaene. Cortical representation of the constituent structure of sentences.. Proc Natl Acad Sci U S A, 108(6):2522--2527, February 2011. [WWW] [PDF]
    Abstract: Linguistic analyses suggest that sentences are not mere strings of words but possess a hierarchical structure with constituents nested inside each other. We used functional magnetic resonance imaging (fMRI) to search for the cerebral mechanisms of this theoretical construct. We hypothesized that the neural assembly that encodes a constituent grows with its size, which can be approximately indexed by the number of words it encompasses. We therefore searched for brain regions where activation increased parametrically with the size of linguistic constituents, in response to a visual stream always comprising 12 written words or pseudowords. The results isolated a network of left-hemispheric regions that could be dissociated into two major subsets. Inferior frontal and posterior temporal regions showed constituent size effects regardless of whether actual content words were present or were replaced by pseudowords (jabberwocky stimuli). This observation suggests that these areas operate autonomously of other language areas and can extract abstract syntactic frames based on function words and morphological information alone. On the other hand, regions in the temporal pole, anterior superior temporal sulcus and temporo-parietal junction showed constituent size effect only in the presence of lexico-semantic information, suggesting that they may encode semantic constituents. In several inferior frontal and superior temporal regions, activation was delayed in response to the largest constituent structures, suggesting that nested linguistic structures take increasingly longer time to be computed and that these delays can be measured with fMRI.

  27. Felipe Pegado, Kimihiro Nakamura, Laurent Cohen, and Stanislas Dehaene. Breaking the Symmetry: Mirror discrimination for single letters but not for pictures in the Visual Word Form Area. NeuroImage, 55:742-9, 2011. [bibtex-entry]

  28. Manuela Piazza, Antonia Fumarola, Alessandro Chinello, and David Melcher.. Subitizing Reflects Visuo-spatial Object Individuation Capacity.. Cognition, 121(1):147-153, 2011. [PDF] [bibtex-entry]

  29. Lior Reich, Marcin Szwed, Laurent Cohen, and Amir Amedi. A ventral visual stream reading center independent of visual experience.. Curr Biol, 21(5):363--368, March 2011. [WWW] [PDF]
    Abstract: The visual word form area (VWFA) is a ventral stream visual area that develops expertise for visual reading [1-3]. It is activated across writing systems and scripts [4, 5] and encodes letter strings irrespective of case, font, or location in the visual field [1] with striking anatomical reproducibility across individuals [6]. In the blind, comparable reading expertise can be achieved using Braille. This study investigated which area plays the role of the VWFA in the blind. One would expect this area to be at either parietal or bilateral occipital cortex, reflecting the tactile nature of the task and crossmodal plasticity, respectively [7, 8]. However, according to the metamodal theory [9], which suggests that brain areas are responsive to a specific representation or computation regardless of their input sensory modality, we predicted recruitment of the left-hemispheric VWFA, identically to the sighted. Using functional magnetic resonance imaging, we show that activation during Braille reading in blind individuals peaks in the VWFA, with striking anatomical consistency within and between blind and sighted. Furthermore, the VWFA is reading selective when contrasted to high-level language and low-level sensory controls. Thus, we propose that the VWFA is a metamodal reading area that develops specialization for reading regardless of visual experience.

  30. René Scheeringa, Ali Mazaheri, Ingo Bojak, David G Norris, and Andreas Kleinschmidt. Modulation of visually evoked cortical FMRI responses by phase of ongoing occipital alpha oscillations.. J Neurosci, 31(10):3813--3820, March 2011. [WWW] [PDF]
    Abstract: Using simultaneous electroencephalography as a measure of ongoing activity and functional magnetic resonance imaging (fMRI) as a measure of the stimulus-driven neural response, we examined whether the amplitude and phase of occipital alpha oscillations at the onset of a brief visual stimulus affects the amplitude of the visually evoked fMRI response. When accounting for intrinsic coupling of alpha amplitude and occipital fMRI signal by modeling and subtracting pseudo-trials, no significant effect of prestimulus alpha amplitude on the evoked fMRI response could be demonstrated. Regarding the effect of alpha phase, we found that stimuli arriving at the peak of the alpha cycle yielded a lower blood oxygenation level-dependent (BOLD) fMRI response in early visual cortex (V1/V2) than stimuli presented at the trough of the cycle. Our results therefore show that phase of occipital alpha oscillations impacts the overall strength of a visually evoked response, as indexed by the BOLD signal. This observation complements existing evidence that alpha oscillations reflect periodic variations in cortical excitability and suggests that the phase of oscillations in postsynaptic potentials can serve as a mechanism of gain control for incoming neural activity. Finally, our findings provide a putative neural basis for observations of alpha phase dependence of visual perceptual performance.

  31. Marcin Szwed, Stanislas Dehaene, Andreas Kleinschmidt, Evelyn Eger, Romain Valabrègue, Alexis Amadon, and Laurent Cohen. Specialization for written words over objects in the visual cortex.. Neuroimage, 56(1):330--344, May 2011. [WWW] [PDF]
    Abstract: The Visual Word Form Area (VWFA) is part of the left ventral visual stream that underlies the invariant identification of visual words. It remains debated whether this region is truly selective for words relative to common objects; why this particular part of the visual system is reproducibly engaged in reading; and whether reading expertise also relies on perceptual learning within earlier visual areas. In this fMRI study we matched written words and line-drawings of objects in luminance, contour length and number of features. We then compared them to control images made by scrambling procedures that kept local features intact. Greater responses to written words than to objects were found not only in the VWFA, but also in areas V1/V2 and V3v/V4. Furthermore, by contrasting stimuli reduced either to line junctions (vertices) or to line midsegments, we showed that the VWFA partially overlaps with regions of ventral visual cortex particularly sensitive to the presence of line junctions that are useful for object recognition. Our results indicate that preferential processing of written words can be observed at multiple levels of the visual system. It is possible that responses in early visual areas might be due to some remaining differences between words and controls not eliminated in the present stimuli. However, our results concur with recent comparisons of literates and illiterates and suggest that these early visual activations reflect the effects of perceptual learning under pressure for fast, parallel processing that is more prominent in reading than other visual cognitive processes.

  32. Filip Van Opstal, Floris P de Lange, and Stanislas Dehaene. Rapid parallel semantic processing of numbers without awareness.. Cognition, 120(1):136--147, July 2011. [WWW]
    Abstract: In this study, we investigate whether multiple digits can be processed at a semantic level without awareness, either serially or in parallel. In two experiments, we presented participants with two successive sets of four simultaneous Arabic digits. The first set was masked and served as a subliminal prime for the second, visible target set. According to the instructions, participants had to extract from the target set either the mean or the sum of the digits, and to compare it with a reference value. Results showed that participants applied the requested instruction to the entire set of digits that was presented below the threshold of conscious perception, because their magnitudes jointly affected the participant's decision. Indeed, response decision could be accurately modeled as a sigmoid logistic function that pooled together the evidence provided by the four targets and, with lower weights, the four primes. In less than 800ms, participants successfully approximated the addition and mean tasks, although they tended to overweight the large numbers, particularly in the sum task. These findings extend previous observations on ensemble coding by showing that set statistics can be extracted from abstract symbolic stimuli rather than low-level perceptual stimuli, and that an ensemble code can be represented without awareness.

  33. Virginie van Wassenhove, Marc Wittmann, A D Bud Craig, and Martin P. Paulus. Psychological and neural mechanisms of subjective time dilation.. Front Neurosci, 5:56, 2011. [WWW]
    Abstract: For a given physical duration, certain events can be experienced as subjectively longer in duration than others. Try this for yourself: take a quick glance at the second hand of a clock. Immediately, the tick will pause momentarily and appear to be longer than the subsequent ticks. Yet, they all last exactly 1?s. By and large, a deviant or an unexpected stimulus in a series of similar events (same duration, same features) can elicit a relative overestimation of subjective time (or "time dilation") but, as is shown here, this is not always the case. We conducted an event-related functional magnetic neuroimaging study on the time dilation effect. Participants were presented with a series of five visual discs, all static and of equal duration (standards) except for the fourth one, a looming or a receding target. The duration of the target was systematically varied and participants judged whether it was shorter or longer than all other standards in the sequence. Subjective time dilation was observed for the looming stimulus but not for the receding one, which was estimated to be of equal duration to the standards. The neural activation for targets (looming and receding) contrasted with the standards revealed an increased activation of the anterior insula and of the anterior cingulate cortex. Contrasting the looming with the receding targets (i.e., capturing the time dilation effect proper) revealed a specific activation of cortical midline structures. The implication of midline structures in the time dilation illusion is here interpreted in the context of self-referential processes.

  34. F. VINCKIER, E. QIAO, C. PALLIER, S. DEHAENE, and L. COHEN. The impact of letter spacing on reading: a test of the bigram coding hypothesis. Journal of vision, 11(6):8:1-21, 2011. [bibtex-entry]

  35. Catherine Wacongne, Etienne Labyt, Virginie van Wassenhove, Tristan Bekinschtein, Lionel Naccache, and Stanislas Dehaene. Evidence for a hierarchy of predictions and prediction errors in human cortex.. Proc Natl Acad Sci U S A, 108(51):20754--20759, December 2011. [WWW] [PDF]
    Abstract: According to hierarchical predictive coding models, the cortex constantly generates predictions of incoming stimuli at multiple levels of processing. Responses to auditory mismatches and omissions are interpreted as reflecting the prediction error when these predictions are violated. An alternative interpretation, however, is that neurons passively adapt to repeated stimuli. We separated these alternative interpretations by designing a hierarchical auditory novelty paradigm and recording human EEG and magnetoencephalographic (MEG) responses to mismatching or omitted stimuli. In the crucial condition, participants listened to frequent series of four identical tones followed by a fifth different tone, which generates a mismatch response. Because this response itself is frequent and expected, the hierarchical predictive coding hypothesis suggests that it should be cancelled out by a higher-order prediction. Three consequences ensue. First, the mismatch response should be larger when it is unexpected than when it is expected. Second, a perfectly monotonic sequence of five identical tones should now elicit a higher-order novelty response. Third, omitting the fifth tone should reveal the brain's hierarchical predictions. The rationale here is that, when a deviant tone is expected, its omission represents a violation of two expectations: a local prediction of a tone plus a hierarchically higher expectation of its deviancy. Thus, such an omission should induce a greater prediction error than when a standard tone is expected. Simultaneous EEE- magnetoencephalographic recordings verify those predictions and thus strongly support the predictive coding hypothesis. Higher-order predictions appear to be generated in multiple areas of frontal and associative cortices.

  36. Ariel Zylberberg, Stanislas Dehaene, Pieter R Roelfsema, and Mariano Sigman. The human Turing machine: a neural framework for mental programs.. Trends Cogn Sci, 15(7):293--300, July 2011. [WWW] [PDF]
    Abstract: In recent years much has been learned about how a single computational processing step is implemented in the brain. By contrast, we still have surprisingly little knowledge of the neuronal mechanisms by which multiple such operations are sequentially assembled into mental algorithms. We outline a theory of how individual neural processing steps might be combined into serial programs. We propose a hybrid neuronal device: each step involves massively parallel computation that feeds a slow and serial production system. Production selection is mediated by a system of competing accumulator neurons that extends the role of these neurons beyond the selection of a motor action. Productions change the state of sensory and mnemonic neurons and iteration of such cycles provides a basis for mental programs.



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