Publications of year 2013
  1. Lucie Charles. Consciousness, error-processing and metacognition. PhD thesis, Paris VI, 2013. [PDF] [bibtex-entry]

Book chapters
  1. Naama Friedmann, Michal Biran, and and Dror Dotan. Lexical retrieval and its breakdown in aphasia and developmental language impairment. In Handbook of Biolinguistics. Cambridge University Press, 2013. [PDF] [bibtex-entry]

  2. Manuela Piazza. Start-up neurocognitivi dell'apprendimento dei numeri e del calcolo. In Intervento logopedico nei DSA- La discalculia, pages 18-44. Biancardi A., Mariani E. and Pieretti M., 2013. [bibtex-entry]

Articles in journals
  1. Irene Altarelli, Karla Monzalvo, Stéphanie Iannuzzi, Joel Fluss, Catherine Billard, Franck Ramus, and Ghislaine Dehaene-Lambertz. A Functionally Guided Approach to the Morphometry of Occipitotemporal Regions in Developmental Dyslexia: Evidence for Differential Effects in Boys and Girls. J Neurosci, 33(27):11296--11301, July 2013. [WWW] [PDF]
    Abstract: Developmental dyslexia is a learning disability that specifically affects reading acquisition. Cortical anomalies and gray matter volume differences in various temporal regions have been reported in dyslexic subjects compared with controls. However, consistency between studies is lacking. In the present experiments, we focused our structural analyses on the ventral occipitotemporal regions, defined by their functional response to visual categories. We applied a subject-by-subject functionally guided approach on a total of 76 participants (31 dyslexic children). Cortical thickness was estimated for each participant around his/her peak of specific functional activation to visual words, faces, or places. Results from two independent datasets showed a reduction in thickness in dyslexic children compared with controls in the region responsive to words, in the left hemisphere. Additionally, a gender-by-diagnosis interaction was observed at the same location, due to differences in girls only. To avoid the potential confound of reading level, we also contrasted dyslexic and control children matched for reading performance, and we observed a similar difference, although in a smaller extent of cortex. The present study thus provides the first account of a focal cortical thickness reduction in dyslexia in the subregion of ventral occipitotemporal cortex specifically responsive to visual words, when age, gender, and reading performance are taken into account.

  2. Alfonso Barrós-Loscertales, Noelia Ventura-Campos, Maya Visser, Agnès Alsius, Christophe Pallier, César Avila Rivera, and Salvador Soto-Faraco. Neural correlates of audiovisual speech processing in a second language.. Brain Lang, 126(3):253--262, September 2013. [WWW]
    Abstract: Neuroimaging studies of audiovisual speech processing have exclusively addressed listeners' native language (L1). Yet, several behavioural studies now show that AV processing plays an important role in non-native (L2) speech perception. The current fMRI study measured brain activity during auditory, visual, audiovisual congruent and audiovisual incongruent utterances in L1 and L2. BOLD responses to congruent AV speech in the pSTS were stronger than in either unimodal condition in both L1 and L2. Yet no differences in AV processing were expressed according to the language background in this area. Instead, the regions in the bilateral occipital lobe had a stronger congruency effect on the BOLD response (congruent higher than incongruent) in L2 as compared to L1. According to these results, language background differences are predominantly expressed in these unimodal regions, whereas the pSTS is similarly involved in AV integration regardless of language dominance.

  3. Lucie Charles, Filip Van Opstal, Sébastien Marti, and Stanislas Dehaene. Distinct brain mechanisms for conscious versus subliminal error detection. Neuroimage, 73:80--94, June 2013. [WWW] [PDF]
    Abstract: Metacognition, the ability to monitor one's own cognitive processes, is frequently assumed to be univocally associated with conscious processing. However, some monitoring processes, such as those associated with the evaluation of one's own performance, may conceivably be sufficiently automatized to be deployed non-consciously. Here, we used simultaneous electro- and magneto-encephalography (EEG/MEG) to investigate how error detection is modulated by perceptual awareness of a masked target digit. The Error-Related Negativity (ERN), an EEG component occurring ~100 ms after an erroneous response, was exclusively observed on conscious trials: regardless of masking strength, the amplitude of the ERN showed a step-like increase when the stimulus became visible. Nevertheless, even in the absence of an ERN, participants still managed to detect their errors at above-chance levels under subliminal conditions. Error detection on conscious trials originated from the posterior cingulate cortex, while a small response to non-conscious errors was seen in dorsal anterior cingulate. We propose the existence of two distinct brain mechanisms for metacognitive judgements: a conscious all-or-none process of single-trial response evaluation, and a non-conscious statistical assessment of confidence.

  4. Alessandro Chinello, Veronica Cattani, Claudia Bonfiglioli, Stanislas Dehaene, and Manuela Piazza. Objects, numbers, fingers, space: clustering of ventral and dorsal functions in young children and adults. Dev Sci, 16(3):377--393, May 2013. [WWW] [PDF]
    Abstract: In the primate brain, sensory information is processed along two partially segregated cortical streams: the ventral stream, mainly coding for objects' shape and identity, and the dorsal stream, mainly coding for objects' quantitative information (including size, number, and spatial position). Neurophysiological measures indicate that such functional segregation is present early on in infancy, and that the two streams follow independent maturational trajectories during childhood. Here we collected, in a large sample of young children and adults, behavioural measures on an extensive set of functions typically associated with either the dorsal or the ventral stream. We then used a correlational approach to investigate the presence of inter-individual variability resulting in clustering of functions. Results show that dorsal- and ventral-related functions follow two uncorrelated developmental trajectories. Moreover, within each stream, some functions show age-independent correlations: finger gnosis, non-symbolic numerical abilities and spatial abilities within the dorsal stream, and object and face recognition abilities within the ventral stream. This pattern of clear within-stream cross-task correlation seems to be lost in adults, with two notable exceptions: performance in face and object recognition on one side, and in symbolic and non-symbolic comparison on the other, remain correlated, pointing to distinct shape recognition and quantity comparison systems.

  5. Dror Dotan and Stanislas Dehaene. How do we convert a number into a finger trajectory?. Cognition, 129 (3):512-29, 2013. [PDF] [bibtex-entry]

  6. Evelyn Eger, Laura Moretti, Stanislas Dehaene, and Angela Sirigu. Decoding the representation of learned social roles in the human brain. Cortex, 49(9):2484--2493, October 2013. [WWW] [PDF]
    Abstract: Humans as social beings are profoundly affected by exclusion. Short experiences with people differing in their degree of prosocial behaviour can induce reliable preferences for including partners, but the neural mechanisms of this learning remain unclear. Here, we asked participants to play a short social interaction game based on "cyber-ball" where one fictive partner included and another excluded the subject, thus defining social roles (includer - "good", excluder - "bad"). We then used multivariate pattern recognition on high-resolution functional magnetic resonance imaging (fMRI) data acquired before and after this game to test whether neural responses to the partners' and neutral control faces during a perceptual task reflect their learned social valence. Support vector classification scores revealed a learning-related increase in neural discrimination of social status in anterior insula and anterior cingulate regions, which was mainly driven by includer faces becoming distinguishable from excluder and control faces. Thus, face-evoked responses in anterior insula and anterior cingulate cortex contain fine-grained information shaped by prior social interactions that allow for categorisation of faces according to their learned social status. These lasting traces of social experience in cortical areas important for emotional and social processing could provide a substrate of how social inclusion shapes future behaviour and promotes cooperative interactions between individuals.

  7. E. Eger, P. Pinel, S. Dehaene, and A. Kleinschmidt. Spatially Invariant Coding of Numerical Information in Functionally Defined Subregions of Human Parietal Cortex. Cereb Cortex, Nov 28, November 2013. [WWW] [PDF]
    Abstract: Macaque electrophysiology has revealed neurons responsive to number in lateral (LIP) and ventral (VIP) intraparietal areas. Recently, fMRI pattern recognition revealed information discriminative of individual numbers in human parietal cortex but without precisely localizing the relevant sites or testing for subregions with different response profiles. Here, we defined the human functional equivalents of LIP (feLIP) and VIP (feVIP) using neurophysiologically motivated localizers. We applied multivariate pattern recognition to investigate whether both regions represent numerical information and whether number codes are position specific or invariant. In a delayed number comparison paradigm with laterally presented numerosities, parietal cortex discriminated between numerosities better than early visual cortex, and discrimination generalized across hemifields in parietal, but not early visual cortex. Activation patterns in the 2 parietal regions of interest did not differ in the coding of position-specific or position-independent number information, but in the expression of a numerical distance effect which was more pronounced in feLIP.Thus, the representation of number in parietal cortex is at least partially position invariant. Both feLIP and feVIP contain information about individual numerosities in humans, but feLIP hosts a coarser representation of numerosity than feVIP, compatible with either broader tuning or a summation code.

  8. Marie-Laure Grillon, Catherine Oppenheim, Gaël Varoquaux, Frédérique Charbonneau, Anne-Dominique Devauchelle, Marie-Odile Krebs, Franck Baylé, Bertrand Thirion, and Caroline Huron. Hyperfrontality and hypoconnectivity during refreshing in schizophrenia. Psychiatry Res, 211(3):226--233, March 2013. [WWW] [PDF]
    Abstract: Anomalous activations of the prefrontal cortex (PFC) and posterior cerebral areas have been reported in previous studies of working memory in schizophrenia. Several interpretations have been reported: e.g., neural inefficiency, the use of different strategies and differences in the functional organization of the cerebral cortex. To better understand these abnormal activations, we investigated the cerebral bases of a working memory component process, namely refreshing (i.e., thinking briefly of a just-activated representation). Fifteen patients with schizophrenia and 15 control subjects participated in this functional magnetic resonance imaging (fMRI) study. Participants were told that whenever they saw a word on the screen, they had to read it silently to themselves (read and repeat conditions), and when they saw a dot, they had to think of the just-previous word (refresh condition). The refresh condition (in comparison with the read condition) was associated with significantly increased activation in the left inferior frontal gyrus and significantly decreased connectivity within the prefrontal cortex and between the prefrontal and parietal cortices in patients with schizophrenia in comparison with control subjects. These results suggest that prefrontal dysfunctions in schizophrenia might be related to a defective ability to initiate (rather than to execute) specific cognitive processes.

  9. Joachim Gross, Sylvain Baillet, Gareth R. Barnes, Richard N. Henson, Arjan Hillebrand, Ole Jensen, Karim Jerbi, Vladimir Litvak, Burkhard Maess, Robert Oostenveld, Lauri Parkkonen, Jason R. Taylor, Virginie van Wassenhove, Michael Wibral, and Jan-Mathijs Schoffelen. Good practice for conducting and reporting MEG research. Neuroimage, 65:349--363, January 2013. [WWW] [PDF]
    Abstract: Magnetoencephalographic (MEG) recordings are a rich source of information about the neural dynamics underlying cognitive processes in the brain, with excellent temporal and good spatial resolution. In recent years there have been considerable advances in MEG hardware developments and methods. Sophisticated analysis techniques are now routinely applied and continuously improved, leading to fascinating insights into the intricate dynamics of neural processes. However, the rapidly increasing level of complexity of the different steps in a MEG study make it difficult for novices, and sometimes even for experts, to stay aware of possible limitations and caveats. Furthermore, the complexity of MEG data acquisition and data analysis requires special attention when describing MEG studies in publications, in order to facilitate interpretation and reproduction of the results. This manuscript aims at making recommendations for a number of important data acquisition and data analysis steps and suggests details that should be specified in manuscripts reporting MEG studies. These recommendations will hopefully serve as guidelines that help to strengthen the position of the MEG research community within the field of neuroscience, and may foster discussion in order to further enhance the quality and impact of MEG research.

  10. Carlos M. Hamamé, Marcin Szwed, Michael Sharman, Juan R. Vidal, Marcella Perrone-Bertolotti, Philippe Kahane, Olivier Bertrand, and Jean-Philippe Lachaux. Dejerine's reading area revisited with intracranial EEG: selective responses to letter strings. Neurology, 80(6):602--603, February 2013. [WWW] [PDF] [bibtex-entry]

  11. Carlos M. Hamamé, Marcin Szwed, Michael Sharman, Juan R. Vidal, Marcella Perrone-Bertolotti, Philippe Kahane, Olivier Bertrand, and Jean-Philippe Lachaux. Dejerine's reading area revisited with intracranial EEG: selective responses to letter strings. Neurology, 80(6):602--603, February 2013. [WWW] [bibtex-entry]

  12. Karina J. Kersbergen, Linda S. de Vries, Britt J M. van Kooij, Ivana Isgum, Karin J. Rademaker, Frank van Bel, Petra S. Hüppi, Jessica Dubois, Floris Groenendaal, and Manon J N L. Benders. Hydrocortisone treatment for bronchopulmonary dysplasia and brain volumes in preterm infants. J Pediatr, 163(3):666--71.e1, September 2013. [WWW] [PDF]
    Abstract: To assess whether there was an adverse effect on brain growth after hydrocortisone (HC) treatment for bronchopulmonary dysplasia (BPD) in a large cohort of infants without dexamethasone exposure.Infants who received HC for BPD between 2005 and 2011 and underwent magnetic resonance imaging at term-equivalent age were included. Control infants born in Geneva (2005-2006) and Utrecht (2007-2011) were matched to the infants treated with HC according to segmentation method, sex, and gestational age. Infants with overt parenchymal pathology were excluded. Multivariable analysis was used to determine if there was a difference in brain volumes between the 2 groups.Seventy-three infants treated with HC and 73 matched controls were included. Mean gestational age was 26.7 weeks, and mean birth weight was 906 g. After correction for gestational age, postmenstrual age at time of scanning, the presence of intraventricular hemorrhage, and birth weight z-score, no differences were found between infants treated with HC and controls in total brain tissue or cerebellar volumes.In the absence of associated parenchymal brain injury, no reduction in brain tissue or cerebellar volumes could be found at term-equivalent age between infants with or without treatment with HC for BPD.

  13. J. R. King, F. Faugeras, A. Gramfort, A. Schurger, I. El Karoui, J. D. Sitt, B. Rohaut, C. Wacongne, E. Labyt, T. Bekinschtein, L. Cohen, L. Naccache, and S. Dehaene. Single-trial decoding of auditory novelty responses facilitates the detection of residual consciousness. Neuroimage, 83:726--738, December 2013. [WWW] [PDF]
    Abstract: Detecting residual consciousness in unresponsive patients is a major clinical concern and a challenge for theoretical neuroscience. To tackle this issue, we recently designed a paradigm that dissociates two electro-encephalographic (EEG) responses to auditory novelty. Whereas a local change in pitch automatically elicits a mismatch negativity (MMN), a change in global sound sequence leads to a late P300b response. The latter component is thought to be present only when subjects consciously perceive the global novelty. Unfortunately, it can be difficult to detect because individual variability is high, especially in clinical recordings. Here, we show that multivariate pattern classifiers can extract subject-specific EEG patterns and predict single-trial local or global novelty responses. We first validate our method with 38 high-density EEG, MEG and intracranial EEG recordings. We empirically demonstrate that our approach circumvents the issues associated with multiple comparisons and individual variability while improving the statistics. Moreover, we confirm in control subjects that local responses are robust to distraction whereas global responses depend on attention. We then investigate 104 vegetative state (VS), minimally conscious state (MCS) and conscious state (CS) patients recorded with high-density EEG. For the local response, the proportion of significant decoding scores (M=60\%) does not vary with the state of consciousness. By contrast, for the global response, only 14\106725320f the VS patients' EEG recordings presented a significant effect, compared to 31\ 0n MCS patients' and 52\ 13760160n CS patients'. In conclusion, single-trial multivariate decoding of novelty responses provides valuable information in non-communicating patients and paves the way towards real-time monitoring of the state of consciousness.

  14. Jean-Rémi King, Jacobo D. Sitt, Frédéric Faugeras, Benjamin Rohaut, Imen El Karoui, Laurent Cohen, Lionel Naccache, and Stanislas Dehaene. Information sharing in the brain indexes consciousness in noncommunicative patients. Curr Biol, 23(19):1914--1919, October 2013. [WWW] [PDF]
    Abstract: Neuronal theories of conscious access tentatively relate conscious perception to the integration and global broadcasting of information across distant cortical and thalamic areas. Experiments contrasting visible and invisible stimuli support this view and suggest that global neuronal communication may be detectable using scalp electroencephalography (EEG). However, whether global information sharing across brain areas also provides a specific signature of conscious state in awake but noncommunicating patients remains an active topic of research. We designed a novel measure termed "weighted symbolic mutual information" (wSMI) and applied it to 181 high-density EEG recordings of awake patients recovering from coma and diagnosed in various states of consciousness. The results demonstrate that this measure of information sharing systematically increases with consciousness state, particularly across distant sites. This effect sharply distinguishes patients in vegetative state (VS), minimally conscious state (MCS), and conscious state (CS) and is observed regardless of etiology and delay since insult. The present findings support distributed theories of conscious processing and open up the possibility of an automatic detection of conscious states, which may be particularly important for the diagnosis of awake but noncommunicating patients.

  15. Sid Kouider, Carsten Stahlhut, Sofie V Gelskov, Leonardo S Barbosa, Michel Dutat, Vincent de Gardelle, Anne Christophe, Stanislas Dehaene, and Ghislaine Dehaene-Lambertz. A neural marker of perceptual consciousness in infants. Science, 340(6130):376--380, April 2013. [WWW] [PDF]
    Abstract: Infants have a sophisticated behavioral and cognitive repertoire suggestive of a capacity for conscious reflection. Yet, demonstrating conscious access in infants remains challenging, mainly because they cannot report their thoughts. Here, to circumvent this problem, we studied whether an electrophysiological signature of consciousness found in adults, corresponding to a late nonlinear cortical response [~300 milliseconds (ms)] to brief pictures, already exists in infants. We recorded event-related potentials while 5-, 12-, and 15-month-old infants (N = 80) viewed masked faces at various levels of visibility. In all age groups, we found a late slow wave showing a nonlinear profile at the expected perceptual thresholds. However, this late component shifted from a weak and delayed response in 5-month-olds (starting around 900 ms) to a more sustained and faster response in older infants (around 750 ms). These results reveal that the brain mechanisms underlying the threshold for conscious perception are already present in infancy but undergo a slow acceleration during development.

  16. Julien Lefèvre, Victor Intwali, Lucie Hertz-Pannier, Petra S. Hüppi, Jean-Francois Mangin, Jessica Dubois, and David Germanaud. Surface smoothing: a way back in early brain morphogenesis. Med Image Comput Comput Assist Interv, 16(Pt 1):590--597, 2013. [PDF]
    Abstract: In this article we propose to investigate the analogy between early cortical folding process and cortical smoothing by mean curvature flow. First, we introduce a one-parameter model that is able to fit a developmental trajectory as represented in a Volume-Area plot and we propose an efficient optimization strategy for parameter estimation. Second, we validate the model on forty cortical surfaces of preterm newborns by comparing global geometrical indices and trajectories of central sulcus along developmental and simulation time.

  17. Mahdi Mahmoudzadeh, Ghislaine Dehaene-Lambertz, Marc Fournier, Guy Kongolo, Sabrina Goudjil, Jessica Dubois, Reinhard Grebe, and Fabrice Wallois. Syllabic discrimination in premature human infants prior to complete formation of cortical layers. Proc Natl Acad Sci U S A, 110(12):4846--4851, March 2013. [WWW] [PDF]
    Abstract: The ontogeny of linguistic functions in the human brain remains elusive. Although some auditory capacities are described before term, whether and how such immature cortical circuits might process speech are unknown. Here we used functional optical imaging to evaluate the cerebral responses to syllables at the earliest age at which cortical responses to external stimuli can be recorded in humans (28- to 32-wk gestational age). At this age, the cortical organization in layers is not completed. Many neurons are still located in the subplate and in the process of migrating to their final location. Nevertheless, we observed several points of similarity with the adult linguistic network. First, whereas syllables elicited larger right than left responses, the posterior temporal region escaped this general pattern, showing faster and more sustained responses over the left than over the right hemisphere. Second, discrimination responses to a change of phoneme (ba vs. ga) and a change of human voice (male vs. female) were already present and involved inferior frontal areas, even in the youngest infants (29-wk gestational age). Third, whereas both types of changes elicited responses in the right frontal region, the left frontal region only reacted to a change of phoneme. These results demonstrate a sophisticated organization of perisylvian areas at the very onset of cortical circuitry, 3 mo before term. They emphasize the influence of innate factors on regions involved in linguistic processing and social communication in humans.

  18. Brice Martin, Anne Giersch, Caroline Huron, and Virginie van Wassenhove. Temporal event structure and timing in schizophrenia: Preserved binding in a longer now. Neuropsychologia, 51:358-71, 2013. [PDF] [bibtex-entry]

  19. Koleen McCrink, Elizabeth S. Spelke, Stanislas Dehaene, and and Pierre Pica. Non-symbolic halving in an Amazonian indigene group. Developmental Science, 16(3):451-62, 2013. [PDF] [bibtex-entry]

  20. Karla Monzalvo and Ghislaine Dehaene-Lambertz. How reading acquisition changes children's spoken language network. Brain Lang, 127(3):356--365, December 2013. [WWW] [PDF]
    Abstract: To examine the influence of age and reading proficiency on the development of the spoken language network, we tested 6- and 9-years-old children listening to native and foreign sentences in a slow event-related fMRI paradigm. We observed a stable organization of the peri-sylvian areas during this time period with a left dominance in the superior temporal sulcus and inferior frontal region. A year of reading instruction was nevertheless sufficient to increase activation in regions involved in phonological representations (posterior superior temporal region) and sentence integration (temporal pole and pars orbitalis). A top-down activation of the left inferior temporal cortex surrounding the visual word form area, was also observed but only in 9year-olds (3years of reading practice) listening to their native language. These results emphasize how a successful cultural practice, reading, slots in the biological constraints of the innate spoken language network.

  21. Manuela Piazza, Pierre Pica, Véronique Izard, Elizabeth S. Spelke, and Stanislas Dehaene. Education enhances the acuity of the nonverbal approximate number system. Psychol Sci, 24(6):1037--1043, June 2013. [WWW] [PDF]
    Abstract: All humans share a universal, evolutionarily ancient approximate number system (ANS) that estimates and combines the numbers of objects in sets with ratio-limited precision. Interindividual variability in the acuity of the ANS correlates with mathematical achievement, but the causes of this correlation have never been established. We acquired psychophysical measures of ANS acuity in child and adult members of an indigene group in the Amazon, the Mundurucú, who have a very restricted numerical lexicon and highly variable access to mathematics education. By comparing Mundurucú subjects with and without access to schooling, we found that education significantly enhances the acuity with which sets of concrete objects are estimated. These results indicate that culture and education have an important effect on basic number perception. We hypothesize that symbolic and nonsymbolic numerical thinking mutually enhance one another over the course of mathematics instruction.

  22. Philippe Pinel and Stanislas Dehaene. Genetic and environmental contributions to brain activation during calculation. Neuroimage, 81:306--316, November 2013. [WWW] [PDF]
    Abstract: Twin studies have long suggested a genetic influence on inter-individual variations in mathematical abilities, and candidate genes have been identified by genome-wide association studies. However, the localization of the brain regions under genetic influence during number manipulation is still unexplored. Here we investigated fMRI data from a group of 19 MZ (monozygotic) and 13 DZ (dizygotic) adult twin pairs, scanned during a mental calculation task. We examined both the activation and the degree of functional lateralization in regions of interest (ROIs) centered on the main activated peaks. Heritability was first investigated by comparing the respective MZ and DZ correlations. Then, genetic and environmental contributions were jointly estimated by fitting a ACE model classically used in twin studies. We found that a subset of the activated network was under genetic influence, encompassing the bilateral posterior superior parietal lobules (PSPL), the right intraparietal sulcus (IPS) and a left superior frontal region. An additional region of the left inferior parietal cortex (IPC), whose deactivation correlated with a behavioral calculation score, also presented higher similarity between MZ than between DZ twins, thus offering a plausible physiological basis for the observable inheritance of math scores. Finally, the main impact of the shared environment was found in the lateralization of activation within the intraparietal sulcus. These maps of genetic and environmental contributions provide precise candidate phenotypes for further genetic association analyses, and illuminate how genetics and education shape the development of number processing networks.

  23. Aaron Schurger, Sebastien Marti, and Stanislas Dehaene. Reducing multi-sensor data to a single time course that reveals experimental effects. BMC Neurosci, 14(1):122, 2013. [WWW] [PDF]
    Abstract: Multi-sensor technologies such as EEG, MEG, and ECoG result in high-dimensional data sets. Given the high temporal resolution of such techniques, scientific questions very often focus on the time-course of an experimental effect. In many studies, researchers focus on a single sensor or the average over a subset of sensors covering a "region of interest" (ROI). However, single-sensor or ROI analyses ignore the fact that the spatial focus of activity is constantly changing, and fail to make full use of the information distributed over the sensor array.We describe a technique that exploits the optimality and simplicity of matched spatial filters in order to reduce experimental effects in multivariate time series data to a single time course. Each (multi-sensor) time sample of each trial is replaced with its projection onto a spatial filter that is matched to an observed experimental effect, estimated from the remaining trials (Effect-Matched Spatial filtering, or EMS filtering). The resulting set of time courses (one per trial) can be used to reveal the temporal evolution of an experimental effect, which distinguishes this approach from techniques that reveal the temporal evolution of an anatomical source or region of interest.We illustrate the technique with data from a dual-task experiment and use it to track the temporal evolution of brain activity during the psychological refractory period. We demonstrate its effectiveness in separating the means of two experimental conditions, and in significantly improving the signal-to-noise ratio at the single-trial level. It is fast to compute and results in readily-interpretable time courses and topographies. The technique can be applied to any data-analysis question that can be posed independently at each sensor, and we provide one example, using linear regression, that highlights the versatility of the technique.The approach described here combines established techniques in a way that strikes a balance between power, simplicity, speed of processing, and interpretability. We have used it to provide a direct view of parallel and serial processes in the human brain that previously could only be measured indirectly. An implementation of the technique in MatLab is freely available via the internet.

  24. Jacobo D. Sitt, Jean-Rémi King, Lionel Naccache, and Stanislas Dehaene. Ripples of consciousness. Trends Cogn Sci, 17(11):552--554, November 2013. [WWW] [PDF]
    Abstract: Casali et al. recently showed that the complexity of the electrophysiological brain response to a transcranial magnetic stimulation pulse distinguishes conscious from unconscious humans in a variety of conditions. In addition to its theoretical implications, this novel method paves the way to a quantitative assessment of the states of consciousness.

  25. Paulo Ventura, Tânia Fernandes, Laurent Cohen, José Morais, Régine Kolinsky, and Stanislas Dehaene. Literacy acquisition reduces the influence of automatic holistic processing of faces and houses. Neurosci Lett, 554:105--109, October 2013. [WWW] [PDF]
    Abstract: Writing was invented too recently to have influenced the human genome. Consequently, reading acquisition must rely on partial recycling of pre-existing brain systems. Prior fMRI evidence showed that in literates a left-hemispheric visual region increases its activation to written strings relative to illiterates and reduces its response to faces. Increasing literacy also leads to a stronger right-hemispheric lateralization for faces. Here, we evaluated whether this reorganization of the brain's face system has behavioral consequences for the processing of non-linguistic visual stimuli. Three groups of adult illiterates, ex-illiterates and literates were tested with the sequential composite face paradigm that evaluates the automaticity with which faces are processed as wholes. Illiterates were consistently more holistic than participants with reading experience in dealing with faces. A second experiment replicated this effect with both faces and houses. Brain reorganization induced by literacy seems to reduce the influence of automatic holistic processing of faces and houses by enabling the use of a more analytic and flexible processing strategy, at least when holistic processing is detrimental to the task.

  26. Sébastien Weibel, Anne Giersch, Stanislas Dehaene, and Caroline Huron. Unconscious task set priming with phonological and semantic tasks. Conscious Cogn, 22(2):517--527, June 2013. [WWW] [PDF]
    Abstract: Whether unconscious stimuli can modulate the preparation of a cognitive task is still controversial. Using a backward masking paradigm, we investigated whether the modulation could be observed even if the prime was made unconscious in 100\116714600f the trials. In two behavioral experiments, subjects were instructed to initiate a phonological or semantic task on an upcoming word, following an explicit instruction and an unconscious prime. When the SOA between prime and instruction was sufficiently long (84ms), primes congruent with the task set instruction led to speedier responses than incongruent primes. In the other condition (36ms), no task set priming was observed. Repetition priming had the opposite tendency, suggesting the observed task set facilitation cannot be ascribed solely to perceptual repetition priming. Our results therefore confirm that unconscious information can modulate cognitive control for currently active task sets, providing sufficient time is available before the conscious decision.

  27. Ariel Zylberberg, Luciano Paz, Pieter R. Roelfsema, Stanislas Dehaene, and Mariano Sigman. A neuronal device for the control of multi-step computations. Papers in Physics, 5, 2013. [PDF] [bibtex-entry]



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