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Publications of year 2006
Books
  1. Stanislas Dehaene. Vers une science de la vie mentale. Fayard, 2006. [bibtex-entry]


Thesis
  1. Véronique Izard. Interactions entre les représentations numériques verbales et non-verbales: étude théorique et expérimentale. Thesis/Dissertation, Université Paris 6, 2006.
    Note: Supervised by Stanislas Dehaene. [PDF]
    Abstract: L'homme manipule les nombres en utilisant les mots de sa langue. De plus, tout un ensemble de données convergent pour indiquer qu'il dispose aussi d'un système non-verbal pour représenter la numérosité des ensembles, système hérité du monde animal. Nous avons abordé la question des interactions entre représentations numériques verbales et non-verbales, en étudiant trois populations différentes : des adultes occidentaux, des bébés de trois mois, ainsi que des Indiens d'Amazonie, les Mundu! rucus, peuple dont la langue possède un lexique numérique très restreint. Nos recherches s'articulent autour des trois axes suivants : 1. Tout d'abord nous avons cherché à donner une caractérisation fine des représentations non-verbales de la numérosité, à l'aide d'un modèle mathématique, qui postule que les numérosités sont représentées sur un continuum interne, la ligne numérique interne. Les prédictions! du modèle s'accordent avec un ensemble de mesures expérimentales, sur des tâches de comparaison, d'addition et de soustraction de numérosités. Enfin, en confrontant les prédictions du modèle aux résultats d'une tâche d'estimation de numérosité que nous avons développée, nous avons pu conclure que la ligne numérique interne est compressive. 2. Par ailleurs, nos travaux sur l'estimation abordent la question des liens entre les représentations de numérosités et les numéraux de la langue. De manière spontanée, les sujets ont une tendance marquée à sous-estimer la numérosité des stimuli, mais la donnée d'un indice suffit à modifier radicalement la manière dont ils sont calibrés. De plus, le processus de calibration agit de manière globale sur toute la ligne numérique. 3. Enfin, que se passe-t-il en l'absence de représentations verbales pour les nombres ? A l'aide de la technique des potentiels évoqués (ERPs), nous avons montré que les bébés âgés de trois mois sont déjà sensibles à la numérosité. Par ailleurs, nos expériences chez les Indiens Mundurucus montrent qu'en l'absence d'un lexique pour les grands nombres, ceux-ci déploient les mêmes compétences que des occidentaux dans des tâches d'arithmétique sur la numérosité, tant qu'on n'exige qu'une réponse approximative. De plus, les Mundurucus possèdent un concept d'égalité exacte, transcendant leurs représentations non-verbales approximatives de numérosité, mais se trouvent limités dans la plupart des tâches d'arithmétique exacte, de fait qu'il leur manque un outil cognitif (analogue à notre procédure de comptage) pour évaluer! la numérosité exacte d'un ensemble. Ces résultats nous éclairent sur les influences respectives de notre bagage biologique et de la culture dans le développement de la cognition numérique
    [bibtex-entry]


Book chapters
  1. Christophe Pallier. Imagerie cérébrale du cerveau bilingue. In Catherine Liégeois-Chauvel, Bernard Guéguen, Patrick Chauvel, and Philippe Kahane, editors,Neurophysiologie du langage. Elsevier, 2006. [bibtex-entry]


Articles in journals
  1. F-Xavier Alario, Hanna Chainay, Stéphane Lehericy, and Laurent Cohen. The role of the supplementary motor area SMA in word production. Brain Research, 1076(1):129--143, March 2006. [WWW] [PDF]
    Abstract: The supplementary motor area (SMA) is a key structure for behavioral planning and execution. Recent research on motor control conducted with monkeys and humans has put to light an anatomical and functional distinction between pre-SMA and SMA-proper. According to this view, the pre-SMA would be involved in higher level processes while the SMA-proper would be more closely tied to motor output. We extended this general framework to the verbal domain, in order to investigate the role of the SMA in speech production. We conducted two speech production experiments with fMRI where we manipulated parameters such as familiarity, complexity or constraints on word selection. The results reveal a parcellation of the SMA into three distinct regions, according to their involvement in different aspects of word production. More specifically, following a rostrocaudal gradient, we observed differential activations related to lexical selection, linear sequence encoding and control of motor output. A parallel organization was observed in the dorsolateral frontal cortex. By refining its anatomical and functional parcellation, these results clarify the roles of the SMA in speech production
    [bibtex-entry]


  2. Jamila Andoh, Eric Artiges, Christophe Pallier, Denis Rivière, Jean-François Mangin, Arnaud Cachia, Marion Plaze, Maris-Laure Paillère-Martinot, and Jean-Luc Martinot. Modulation of language areas with functional MR image-guided magnetic stimulation. Neuroimage, 29(2):619--627, January 2006. [WWW] [PDF]
    Abstract: Repetitive transcranial magnetic stimulation (rTMS) can interfere with linguistic performance when delivered over language areas. At low frequency (1 Hz), rTMS is assumed to decrease cortical excitability; however, the degree of TMS effect on cortical language areas may depend on the localization of the stimulation coil with respect to the inter-individual anatomo-functional variations. Hence, we aimed at investigating individual brain areas involved in semantic and phonological auditory processes. We hypothesized that active rTMS targeted over Wernicke's area might modify the performance during a language-fragment-detection task. Sentences in native or foreign languages were presented to 12 right-handed male healthy volunteers during functional magnetic resonance imaging (fMRI). 3D-functional maps localized the posterior temporal activation (Wernicke) in each subject and MRI anatomical cortical landmarks were used to define Broca's pars opercularis (F3Op). A frameless stereotaxy system was used to guide the TMS coil position over Wernicke's and F3Op areas in each subject. Active and placebo randomized rTMS sessions were applied at 1 Hz, 110\% of motor threshold, during the same language-fragment-detection task. Accuracy and response time (RT) were recorded. RT was significantly decreased by active rTMS compared to placebo over Wernicke's area, and was more decreased for native than for foreign languages. No significant RT change was observed for F3Op area. rTMS conditions did not impair participants' accuracy. Thus, low-frequency rTMS over Wernicke's area can speed-up the response to a task tapping on native language perception in healthy volunteers. This individually-guided stimulation study confirms that facilitatory effects are not confined to high-frequency rTMS
    [bibtex-entry]


  3. Eric Artiges, Catherine Martelli, Lionel Naccache, David Bartrés-Faz, Jean-Bernard Leprovost, Armelle Viard, Marie-Laure Paillère-Martinot, Stanislas Dehaene, and Jean-Luc Martinot. Paracingulate sulcus morphology and fMRI activation detection in schizophrenia patients. Schizophr Res, 82(2-3):143--151, February 2006. [WWW] [PDF]
    Abstract: OBJECTIVE: Altered anterior cingulate cortex activity has been consistently detected by functional imaging in schizophrenia patients. In the present study, we hypothesized that the detection of such local hypoactivity varies when the subjects' local gyrification is monitored. Using a group-statistical approach, we investigated whether the presence or absence of a paracingulate sulcus (PCS) does influence the detection of the activation patterns in the cognitive division of the anterior cingulate cortex (ACcd). METHOD: fMRI data were acquired using an event-related paradigm during a task involving both priming and interference between stimuli. In the fMRI dataset collected from 13 schizophrenia patients and 16 healthy subjects, subgroups were defined according to the presence or absence of a PCS. Regional activations during interference between stimuli were examined in the ACcd of each hemisphere, using for each region of interest both voxel-based random-effects and non-parametric analyses. RESULTS: ACcd activation was left-sided in healthy subjects with a PCS, and right-sided in healthy subjects devoid of a PCS. ACcd activations were detected bilaterally in schizophrenia patients with a PCS, whereas left ACcd was deactivated in patients without a PCS. Subgroup comparisons revealed no difference between healthy subjects with a PCS and patients with a PCS, whereas in the subgroups devoid of PCS, the patients exhibited a bilateral ACcd hypoactivation relative to healthy subjects. CONCLUSIONS: PCS presence or absence influences the detection of ACcd activations in group-analysis of schizophrenia patients
    [bibtex-entry]


  4. Bernhard Baier, Andreas Kleinschmidt, and Notger G. Müller. Cross-modal processing in early visual and auditory cortices depends on expected statistical relationship of multisensory information. Journal of Neuroscience, 26(47):12260--12265, November 2006.
    Note: IMPORTANT Correction: In Figure 2B of the article, the colors for the associated and non-associated conditions were switched by mistake. [WWW] [PDF]
    Abstract: Previous studies have shown that processing information in one sensory modality can either be enhanced or attenuated by concurrent stimulation of another modality. Here, we reconcile these apparently contradictory results by showing that the sign of cross-modal interactions depends on whether the content of two modalities is associated or not. When concurrently presented auditory and visual stimuli are paired by chance, cue-induced preparatory neural activity is strongly enhanced in the task-relevant sensory system and suppressed in the irrelevant system. Conversely, when information in the two modalities is reliably associated, activity is enhanced in both systems regardless of which modality is task relevant. Our findings illustrate an ecologically optimal flexibility of the neural mechanisms that govern multisensory processing: facilitation occurs when integration is expected, and suppression occurs when distraction is expected. Because thalamic structures were more active when the senses needed to operate separately, we propose them to serve gatekeeper functions in early cross-modal interactions
    [bibtex-entry]


  5. Hilary Barth, Kristen La Mont, Jennifer Lipton, Stanislas Dehaene, Nancy Kanwisher, and Elizabeth Spelke. Non-symbolic arithmetic in adults and young children. Cognition, 98:199-222, March 2006. [WWW] [PDF]
    Abstract: Five experiments investigated whether adults and preschool children can perform simple arithmetic calculations on non-symbolic numerosities. Previous research has demonstrated that human adults, human infants, and non-human animals can process numerical quantities through approximate representations of their magnitudes. Here we consider whether these non-symbolic numerical representations might serve as a building block of uniquely human, learned mathematics. Both adults and children with no training in arithmetic successfully performed approximate arithmetic on large sets of elements. Success at these tasks did not depend on non-numerical continuous quantities, modality-specific quantity information, the adoption of alternative non-arithmetic strategies, or learned symbolic arithmetic knowledge. Abstract numerical quantity representations therefore are computationally functional and may provide a foundation for formal mathematics
    [bibtex-entry]


  6. Stanislas Dehaene, Jean-Pierre Changeux, Lionel Naccache, Jérôme Sackur, and Claire Sergent. Cnscious, preconscious, and subliminal processing: a testable taxonomy. Trends Cogn Sci, 10:204-11, 2006. [WWW] [PDF]
    Abstract: Of the many brain events evoked by a visual stimulus, which are specifically associated with conscious perception, and which merely reflect non-conscious processing? Several recent neuroimaging studies have contrasted conscious and non-conscious visual processing, but their results appear inconsistent. Some support a correlation of conscious perception with early occipital events, others with late parieto-frontal activity. Here we attempt to make sense of these dissenting results. On the basis of the global neuronal workspace hypothesis, we propose a taxonomy that distinguishes between vigilance and access to conscious report, as well as between subliminal, preconscious and conscious processing. We suggest that these distinctions map onto different neural mechanisms, and that conscious perception is systematically associated with surges of parieto-frontal activity causing top-down amplification
    [bibtex-entry]


  7. Stanislas Dehaene, Veronique Izard, Pierre Pica, and Elizabeth Spelke. Examining Knowledge of Geometry: Response to Wulff and Delson. Science, 312:1310, 2006. [PDF] [bibtex-entry]


  8. Stanislas Dehaene, Véronique Izard, Pierre Pica, and Elizabeth Spelke. Core knowledge of geometry in an Amazonian indigene group. Science, 311(5759):381--384, January 2006. [WWW] [PDF]
    Abstract: Does geometry constitute a core set of intuitions present in all humans, regardless of their language or schooling? We used two nonverbal tests to probe the conceptual primitives of geometry in the Munduruku, an isolated Amazonian indigene group. Munduruku children and adults spontaneously made use of basic geometric concepts such as points, lines, parallelism, or right angles to detect intruders in simple pictures, and they used distance, angle, and sense relationships in geometrical maps to locate hidden objects. Our results provide evidence for geometrical intuitions in the absence of schooling, experience with graphic symbols or maps, or a rich language of geometrical terms
    [bibtex-entry]


  9. Stanislas Dehaene and Lionel Naccache. Can one suppress subliminal words?. Neuron, 52(3):397--399, November 2006. [WWW] [PDF]
    Abstract: Subliminal words cause behavioral priming, yet the depth of their processing remains debated. Using transcranial magnetic stimulation (TMS), Nakamura et al. demonstrate in this issue of Neuron that this subliminal priming effect can be selectively disrupted. Distinct TMS sites disrupt priming in lexical decision and pronunciation tasks, suggesting that task set influences subliminal processing
    [bibtex-entry]


  10. Ghislaine Dehaene-Lambertz, Stanislas Dehaene, Jean-Luc Anton, Aurelie Campagne, Philippe Ciuciu, Guillaume P Dehaene, Isabelle Denghien, Antoinette Jobert, Denis Lebihan, Mariano Sigman, Christophe Pallier, and Jean-Baptiste Poline. Functional segregation of cortical language areas by sentence repetition. Hum Brain Mapp, 27(5):360--371, May 2006. [WWW] [PDF]
    Abstract: The functional organization of the perisylvian language network was examined using a functional MRI (fMRI) adaptation paradigm with spoken sentences. In Experiment 1, a given sentence was presented every 14.4 s and repeated two, three, or four times in a row. The study of the temporal properties of the BOLD response revealed a temporal gradient along the dorsal-ventral and rostral-caudal directions: From Heschl's gyrus, where the fastest responses were recorded, responses became increasingly slower toward the posterior part of the superior temporal gyrus and toward the temporal poles and the left inferior frontal gyrus, where the slowest responses were observed. Repetition induced a decrease in amplitude and a speeding up of the BOLD response in the superior temporal sulcus (STS), while the most superior temporal regions were not affected. In Experiment 2, small blocks of six sentences were presented in which either the speaker voice or the linguistic content of the sentence, or both, were repeated. Data analyses revealed a clear asymmetry: While two clusters in the left superior temporal sulcus showed identical repetition suppression whether the sentences were produced by the same speaker or different speakers, the homologous right regions were sensitive to sentence repetition only when the speaker voice remained constant. Thus, hemispheric left regions encode linguistic content while homologous right regions encode more details about extralinguistic features like speaker voice. The results demonstrate the feasibility of using sentence-level adaptation to probe the functional organization of cortical language areas. Hum Brain Mapp, 2006. (c) 2006 Wiley-Liss, Inc
    [bibtex-entry]


  11. Ghislaine Dehaene-Lambertz, L. Hertz-Pannier, Jessica Dubois, S. Mériaux, A. Roche, M. Sigman, and Stanislas Dehaene. Functional organization of perisylvian activation during presentation of sentences in preverbal infants. pnas, 103:14240-14245, 2006. [PDF] [bibtex-entry]


  12. Ghislaine Dehaene-Lambertz, Lucie Hertz-Pannier, and Jessica Dubois. Nature and nurture in language acquisition: Anatomical and functional brain-imaging studies in infants. Trends in Neuroscience, 29(7):367--373, 2006. [PDF] [bibtex-entry]


  13. Antoine Del Cul, Stanislas Dehaene, and Marion Leboyer. Preserved subliminal processing and impaired conscious access in schizophrenia. Arch Gen Psychiatry, 63(12):1313--1323, December 2006. [WWW] [PDF]
    Abstract: BACKGROUND: Studies of visual backward masking have frequently revealed an elevated masking threshold in schizophrenia. This finding has frequently been interpreted as indicating a low-level visual deficit. However, more recent models suggest that masking may also involve late and higher-level integrative processes, while leaving intact early bottom-up visual processing. OBJECTIVE: To test the hypothesis that the backward-masking deficit in schizophrenia corresponds to a deficit in the late stages of conscious perception, whereas the subliminal processing of masked stimuli is fully preserved. DESIGN: Twenty-eight patients with schizophrenia and 28 normal control subjects performed 2 backward-masking experiments. We used Arabic digits as stimuli and varied quasi-continuously the interval with a subsequent mask, thus allowing us to progressively unmask the stimuli. We finely quantified their degree of visibility using objective and subjective measures to evaluate the threshold duration for access to consciousness. We also studied the priming effect caused by the variably masked numbers in a comparison task performed on a subsequently presented and highly visible target number. RESULTS: The threshold delay between the digit and mask necessary for the conscious perception of the masked stimulus was longer in patients compared with controls. This higher consciousness threshold in patients was confirmed by an objective and a subjective measure, and both measures were highly correlated for the patients and controls. However, subliminal priming of masked numbers was effective and identical in patients and controls. CONCLUSIONS: Access to conscious report of masked stimuli is impaired in schizophrenia, whereas fast bottom-up processing of the same stimuli, as assessed by subliminal priming, is preserved. These findings suggest a high-level origin of the masking deficit in schizophrenia, although they leave open for further research its exact relation to previously identified bottom-up visual processing abnormalities
    [bibtex-entry]


  14. Dori Derdikman, Marcin Szwed, Knarik Bagdasarian, Per Magne Knutsen, Maciej Pietr, Chunxiu Yu, Amos Arieli, and Ehud Ahissar. Active construction of percepts about object location.. Novartis Found Symp, 270:4--14; discussion 14-7, 51-8, 2006.
    Abstract: Mammals acquire much of their sensory information by actively moving their sensory organs. Rats, in particular, scan their surrounding environment with their whiskers. This form of active sensing induces specific patterns of temporal encoding of sensory information, which are based on a conversion of space into time via sensor movement. We investigate the ways in which object location is encoded by the whiskers and decoded by the brain. We recorded from first-order neurons located in the trigeminal ganglion (TG) of anaesthetized rats during epochs of artificial whisking induced by electrical stimulation of the facial motor nerve. We found that TG neurons encode the three positional coordinates with different codes. The horizontal coordinate (along the backward-forward axis) is encoded by two encoding schemes, both relying on the firing times of one type of TG neuron, the 'contact cell'. The radial coordinate (from face outward) is encoded primarily by the firing magnitude of another type of TG neurons, the 'pressure cell'. The vertical coordinate (from ground up) is encoded by the identity of activated neurons. The decoding schemes of at least some of these sensory cues, our data suggest, are also active: cortical representations are generated by a thalamic comparison of cortical expectations with incoming sensory data.
    [bibtex-entry]


  15. J. Dubois, L. Hertz-Pannier, Ghislaine Dehaene-Lambertz, Y. Cointepas, and D. Le Bihan. Assessment of the early organization and maturation of infants' cerebral white matter fiber bundles: a feasibility study using quantitative diffusion tensor imaging and tractography. Neuroimage, 30(4):1121--1132, May 2006. [WWW] [PDF]
    Abstract: The human infant is particularly immature at birth and brain maturation, with the myelination of white matter fibers, is protracted until adulthood. Diffusion tensor imaging offers the possibility to describe non invasively the fascicles spatial organization at an early stage and to follow the cerebral maturation with quantitative parameters that might be correlated with behavioral development. Here, we assessed the feasibility to study the organization and maturation of major white matter bundles in eighteen 1- to 4-month-old healthy infants, using a specific acquisition protocol customized to the immature brain (with 15 orientations of the diffusion gradients and a 700 s mm(-2)b factor). We were able to track most of the main fascicles described at later ages despite the low anisotropy of the infant white matter, using the FACT algorithm. This mapping allows us to propose a new method of quantification based on reconstructed tracts, split between specific regions, which should be more sensitive to specific changes in a bundle than the conventional approach, based on regions-of-interest. We observed variations in fractional anisotropy and mean diffusivity over the considered developmental period in most bundles (corpus callosum, cerebellar peduncles, cortico-spinal tract, spino-thalamic tract, capsules, radiations, longitudinal and uncinate fascicles, cingulum). The results are in good agreement with the known stages of white matter maturation and myelination, and the proposed approach might provide important insights on brain development
    [bibtex-entry]


  16. J. Dubois, C. Poupon, F. Lethimonnier, and D. Le Bihan. Optimized diffusion gradient orientation schemes for corrupted clinical DTI data sets.. MAGMA, 19(3):134--143, August 2006. [WWW] [PDF]
    Abstract: OBJECT: A method is proposed for generating schemes of diffusion gradient orientations which allow the diffusion tensor to be reconstructed from partial data sets in clinical DT-MRI, should the acquisition be corrupted or terminated before completion because of patient motion. MATERIALS AND METHODS: A general energy-minimization electrostatic model was developed in which the interactions between orientations are weighted according to their temporal order during acquisition. In this report, two corruption scenarios were specifically considered for generating relatively uniform schemes of 18 and 60 orientations, with useful subsets of 6 and 15 orientations. The sets and subsets were compared to conventional sets through their energy, condition number and rotational invariance. Schemes of 18 orientations were tested on a volunteer. RESULTS: The optimized sets were similar to uniform sets in terms of energy, condition number and rotational invariance, whether the complete set or only a subset was considered. Diffusion maps obtained in vivo were close to those for uniform sets whatever the acquisition time was. This was not the case with conventional schemes, whose subset uniformity was insufficient. CONCLUSION: With the proposed approach, sets of orientations responding to several corruption scenarios can be generated, which is potentially useful for imaging uncooperative patients or infants.
    [bibtex-entry]


  17. Raphaël Gaillard, Antoine Del Cul, Lionel Naccache, Fabien Vinckier, Laurent Cohen, and Stanislas Dehaene. Nonconscious semantic processing of emotional words modulates conscious access. Proc Natl Acad Sci U S A, April 2006. [WWW] [PDF]
    Abstract: Whether masked words can be processed at a semantic level remains a controversial issue in cognitive psychology. Although recent behavioral studies have demonstrated masked semantic priming for number words, attempts to generalize this finding to other categories of words have failed. Here, as an alternative to subliminal priming, we introduce a sensitive behavioral method to detect nonconscious semantic processing of words. The logic of this method consists of presenting words close to the threshold for conscious perception and examining whether their semantic content modulates performance in objective and subjective tasks. Our results disclose two independent sources of modulation of the threshold for access to consciousness. First, prior conscious perception of words increases the detection rate of the same words when they are subsequently presented with stronger masking. Second, the threshold for conscious access is lower for emotional words than for neutral ones, even for words that have not been previously consciously perceived, thus implying that written words can receive nonconscious semantic processing
    [bibtex-entry]


  18. Raphaël Gaillard, Lionel Naccache, Philippe Pinel, Stéphane Clémenceau, Emmanuelle Volle, Dominique Hasboun, Sophie Dupont, Michel Baulac, Stanislas Dehaene, Claude Adam, and Laurent Cohen. Direct intracranial, FMRI, and lesion evidence for the causal role of left inferotemporal cortex in reading. Neuron, 50(2):191--204, April 2006. [WWW] [PDF]
    Abstract: Models of the "visual word form system" postulate that a left occipitotemporal region implements the automatic visual word recognition required for efficient reading. This theory was assessed in a patient in whom reading was explored with behavioral measures, fMRI, and intracranial local field potentials. Prior to surgery, when reading was normal, fMRI revealed a normal mosaic of ventral visual selectivity for words, faces, houses, and tools. Intracranial recordings demonstrated that the left occipitotemporal cortex responded with a short latency to conscious but also to subliminal words. Surgery removed a small portion of word-responsive occipitotemporal cortex overlapping with the word-specific fMRI activation. The patient developed a marked reading deficit, while recognition of other visual categories remained intact. Furthermore, in the post-surgery fMRI map of visual cortex, only word-specific activations disappeared. Altogether, these results provide direct evidence for the causal role of the left occipitotemporal cortex in the recognition of visual words
    [bibtex-entry]


  19. Teodora Gliga and Ghislaine Dehaene-Lambertz. Development of a view-invariant representation of the human head. Cognition, February 2006. [WWW] [PDF]
    Abstract: Do infants perceive visual cues as diverse as frontal-view faces, profiles or bodies as being different aspects of the same object, a fellow human? If that is the case, visual exposure to one such cue should facilitate the subsequent processing of the others. To verify this hypothesis, we recorded event-related responses in 4-month-old infants and in adults. Pictures of eyes were interleaved amongst images belonging to three human contexts (frontal-view faces, profiles or bodies) or non-human contexts (houses, cars or pliers). In adults, both profile and frontal-face contexts elicited suppression of the N170 response to eye pictures, indicating an access to a view-invariant representation of faces. In infants, a response suppression of the N290 component was recorded only in the context of frontal faces, while profile context induces a different effect (i.e., a P400 enhancement) on eye processing. This dissociation suggests that the view-invariant representation of faces is learned, as it is for other 3-D objects and needs more than 4 months of exposure to be established. In a follow-up study, where infants were exposed to a short movie showing people rotating their heads, the profile-induced P400 effect was speeded up, indicating that exposure to successive views of the same object is probably a way to build up adult-like face representations
    [bibtex-entry]


  20. Narly Golestani, F-Xavier Alario, Sébastien Meriaux, Denis Le Bihan, Stanislas Dehaene, and Christophe Pallier. Syntax production in bilinguals. Neuropsychologia, 44(7):1029--1040, 2006. [WWW] [PDF]
    Abstract: We used fMRI to examine the functional correlates of syntactical processing in the first (L1) and second (L2) languages of non-proficient, late bilinguals. Subjects either covertly read words or produced sentences from them. Syntactical production during sentence production activated regions including left inferior frontal (LIFG) gyrus and the supplementary motor area in both languages. Analyses performed on the LIFG activation identified on a subject-by-subject basis revealed greater activation in L2 compared to L1 during sentence production and during word reading, consistent with previous work suggesting that greater cognitive effort may be subserved by less well-tuned neural representations that require greater neuronal activity. Remarkably, there was a greater separation in the LIFG activations in L1 versus L2 in less compared to more proficient bilinguals during syntax production, suggesting a functional reorganisation of regions involved in syntactical production as a function of syntactical proficiency
    [bibtex-entry]


  21. Boris S Gutkin, Stanislas Dehaene, and Jean-Pierre Changeux. A neurocomputational hypothesis for nicotine addiction. Proc Natl Acad Sci U S A, 103(4):1106--1111, January 2006. [WWW] [PDF]
    Abstract: We present a hypothetical neurocomputational model that combines a set of neural circuits at the molecular, cellular, and system levels and accounts for several neurobiological and behavioral processes leading to nicotine addiction. We propose that combining changes in the nicotinic receptor response, expressed by mesolimbic dopaminergic neurons, with dopamine-gated learning in action-selection circuits, suffices to capture the acquisition of nicotine addiction. We show that an opponent process enhanced by persistent nicotine-taking renders self-administration rigid and habitual by inhibiting the learning process, resulting in long-term impairments in the absence of the drug. The model implies distinct thresholds on the dosage and duration for the acquisition and persistence of nicotine addiction. Our hypothesis unites a number of prevalent ideas on nicotine action into a coherent formal network for further understanding of compulsive drug addiction
    [bibtex-entry]


  22. P. Huppi and J Dubois. Diffusion tensor imaging of brain development. Semin Fetal Neonatal, 11:489-497, 2006. [PDF] [bibtex-entry]


  23. Andreas Kleinschmidt. Cognitive control signals in visual cortex: flashes meet spotlights. Neuron, 51(1):9--11, July 2006. [WWW] [PDF]
    Abstract: At the intersection of two intensely belabored fields, primary visual cortex (V1) function and neural mechanisms of cognitive control, Jack et al. (in this issue of Neuron) report a neural signal that is neither related to stimulus representation nor spatial attention. Instead, this endogenous signal correlates with task structure and raises new questions
    [bibtex-entry]


  24. Andreas Kleinschmidt and Laurent Cohen. The neural bases of prosopagnosia and pure alexia: recent insights from functional neuroimaging. Curr Opin Neurol, 19(4):386--391, August 2006. [WWW] [PDF]
    Abstract: PURPOSE OF REVIEW: To discuss whether recent functional neuroimaging results can account for clinical phenomenology in visual associative agnosias. RECENT FINDINGS: Functional neuroimaging studies in healthy human subjects have identified only two regions of ventral occipitotemporal cortex that invariantly respond to individual faces and visual words, respectively. The signature of face identity coding in the fusiform neural response was shown to be missing in a patient with prosopagnosia. Another case study established that a surgical lesion close to the region sensitive to visual words can result in pure alexia. SUMMARY: Evidence is increasing that functional specialization for processing face identity and visual word forms is restricted to two specialized sensory modules in the occipitotemporal cortex. A structural or functional lesion to face-sensitive and word-sensitive regions in the ventral occipitotemporal cortex can provide the most parsimonious account for the clinical syndromes of prosopagnosia and agnosic alexia. This review suggests that functional specialization should be considered in terms of whether exclusively one brain region (instead of many) underpins a defined function and not as whether this brain region underpins exclusively one cognitive function. Such functional specialization seems to exist for at least two higher-order visual perceptual functions, face and word identification
    [bibtex-entry]


  25. H. Laufs, John L Holt, Robert Elfont, Michael Krams, Joseph S Paul, K. Krakow, and A. Kleinschmidt. Where the BOLD signal goes when alpha EEG leaves. Neuroimage, 31(4):1408--1418, July 2006. [WWW] [PDF]
    Abstract: Previous studies using simultaneous EEG and fMRI recordings have yielded discrepant results regarding the topography of brain activity in relation to spontaneous power fluctuations in the alpha band of the EEG during eyes-closed rest. Here, we explore several possible explanations for this discrepancy by re-analyzing in detail our previously reported data. Using single subject analyses as a starting point, we found that alpha power decreases are associated with fMRI signal increases that mostly follow two distinct patterns: either 'visual' areas in the occipital lobe or 'attentional' areas in the frontal and parietal lobe. On examination of the EEG spectra corresponding to these two fMRI patterns, we found greater relative theta power in sessions yielding the 'visual' fMRI pattern during alpha desynchronization and greater relative beta power in sessions yielding the 'attentional' fMRI pattern. The few sessions that fell into neither pattern featured the overall lowest theta and highest beta power. We conclude that the pattern of brain activation observed during spontaneous power reduction in the alpha band depends on the general level of brain activity as indexed over a broader spectral range in the EEG. Finally, we relate these findings to the concepts of 'resting state' and 'default mode' and discuss how - as for sleep - EEG-based criteria might be used for staging brain activity during wakefulness
    [bibtex-entry]


  26. Sébastien Mériaux, Alexis Roche, Ghislaine Dehaene-Lambertz, Bertrand Thirion, and Jean-Baptiste Poline. Combined permutation test and mixed-effect model for group average analysis in fMRI.. Hum Brain Mapp, 27(5):402--410, May 2006. [WWW] [PDF]
    Abstract: In group average analyses, we generalize the classical one-sample t test to account for heterogeneous within-subject uncertainties associated with the estimated effects. Our test statistic is defined as the maximum likelihood ratio corresponding to a Gaussian mixed-effect model. The test's significance level is calibrated using the same sign permutation framework as in Holmes et al., allowing for exact specificity control under a mild symmetry assumption about the subjects' distribution. Because our likelihood ratio test does not rely on homoscedasticity, it is potentially more sensitive than both the standard t test and its permutation-based version. We present results from the Functional Imaging Analysis Contest 2005 dataset to support this claim. Hum Brain Mapp 27:402-410, 2006. (c) 2006 Wiley-Liss, Inc
    [bibtex-entry]


  27. Kimihiro Nakamura, Nobuko Hara, Sid Kouider, Yoshihiro Takayama, Ritsuko Hanajima, Katsuyuki Sakai, and Yoshikazu Ugawa. Task-guided selection of the dual neural pathways for reading. Neuron, 52(3):557--564, November 2006. [WWW] [PDF]
    Abstract: The visual perception of words is known to activate the auditory representation of their spoken forms automatically. We examined the neural mechanism for this phonological activation using transcranial magnetic stimulation (TMS) with a masked priming paradigm. The stimulation sites (left superior temporal gyrus [L-STG] and inferior parietal lobe [L-IPL]), modality of targets (visual and auditory), and task (pronunciation and lexical decision) were manipulated independently. For both within- and cross-modal conditions, the repetition priming during pronunciation was eliminated when TMS was applied to the L-IPL, but not when applied to the L-STG, whereas the priming during lexical decision was eliminated when the L-STG, but not the L-IPL, was stimulated. The observed double dissociation suggests that the conscious task instruction modulates the stimulus-driven activation of the lateral temporal cortex for lexico-phonological activation and the inferior parietal cortex for spoken word production, and thereby engages a different neural network for generating the appropriate behavioral response.
    [bibtex-entry]


  28. Boris New, Ludovic Ferrand, Christophe Pallier, and Marc Brysbaert. Reexamining the word length effect in visual word recognition: new evidence from the English Lexicon Project. Psychon Bull Rev, 13(1):45--52, February 2006. [PDF]
    Abstract: In the present study, we reexamined the effect of word length (number of letters in a word) on lexical decision. Using the English Lexicon Project, which is based on a large data set of over 40,481 words (Balota et al., 2002), we performed simultaneous multiple regression analyses on a selection of 33,006 English words (ranging from 3 to 13 letters in length). Our analyses revealed an unexpected pattern of results taking the form of a U-shaped curve. The effect of number of letters was facilitatory for words of 3-5 letters, null for words of 5-8 letters, and inhibitory for words of 8-13 letters. We also showed that printed frequency, number of syllables, and number of orthographic neighbors all made independent contributions. The length effects were replicated in a new analysis of a subset of 3,833 monomorphemic nouns (ranging from 3 to 10 letters), and also in another analysis based on 12,987 bisyllabic items (ranging from 3 to 9 letters). These effects were independent of printed frequency, number of syllables, and number of orthographic neighbors. Furthermore, we also observed robust linear inhibitory effects of number of syllables. Implications for models of visual word recognition are discussed
    [bibtex-entry]


  29. Manuela Piazza, Andrea Mechelli, Cathy J Price, and Brian Butterworth. Exact and approximate judgements of visual and auditory numerosity: an fMRI study. Brain Res, 1106(1):177--188, August 2006. [WWW] [PDF]
    Abstract: Human adults can assess the number of objects in a set (numerosity) by approximate estimation or by exact counting. There is evidence suggesting that numerosity estimation depends on a dedicated mechanism that is a-modal and non-verbal. By contrast, counting requires the coordination between the pre-existing numerosity estimation abilities with language and one-to-one correspondence principles. In this paper we investigate with fMRI the neural correlates of numerosity estimation and counting in human adults, using both visual and auditory stimuli. Results show that attending to approximate numerosity correlates with increased activity of a right lateralized fronto-parietal cortical network, and that this activity is independent of the stimuli presentation's modality. Counting activates additional left prefrontal, parietal, and bilateral premotor areas, again independently from stimulus modality. These results dissociate two neuronal systems that underlie different numerosity judgements
    [bibtex-entry]


  30. Manuela Piazza, Philippe Pinel, and Stanislas Dehaene. Objective correlates of an unusual subjective experience: A single-case study of number?form synaesthesia. Cognitive Neuropsychology, 23(8):1162--1173, 2006. [PDF]
    Abstract: There is a universal and often unconscious tendency to mentally associate the number sequence with a spatial continuum (the mental number line). Here we study one individual who reports a strong and vivid sense of space when processing numbers. For him, the number sequence has a precise spatial form: a curvilinear right-to-left oriented line. We used various tasks to demonstrate that this numerical - spatial association is not a mere figment of his imagination, but a constrained experiential phenomenon consistent across sessions and automatically triggered by the visual presentation of numbers. We also show that this idiosyncratic representation can coexist with another implicit association, the SNARC effect (Spatial?Numerical Association of Response Codes, where small numbers are associated with the left side of space). This effect is present in individuals without explicit number forms and is not affected in the present subject in spite of his reversed subjective representation
    [bibtex-entry]


  31. Marion Plaze, David Bartrés-Faz, Jean-Luc Martinot, Dominique Januel, Franck Bellivier, Renaud De Beaurepaire, Sandra Chanraud, Jamila Andoh, Jean-Pascal Lefaucheur, Eric Artiges, Christophe Pallier, and Marie-Laure Paillère-Martinot. Left superior temporal gyrus activation during sentence perception negatively correlates with auditory hallucination severity in schizophrenia patients. Schizophr Res, July 2006. [WWW] [PDF]
    Abstract: The left superior temporal cortex, which supports linguistic functions, has consistently been reported to activate during auditory-verbal hallucinations in schizophrenia patients. It has been suggested that auditory hallucinations and the processing of normal external speech compete for common neurophysiological resources. We tested the hypothesis of a negative relationship between the clinical severity of hallucinations and local brain activity in posterior linguistic regions while patients were listening to external speech. Fifteen right-handed patients with schizophrenia and daily auditory hallucinations for at least 3 months were studied with event-related fMRI while listening to sentences in French or to silence. Severity of hallucinations, assessed using the auditory hallucination subscales of the Psychotic Symptom Rating Scales (PSYRATS) and of the Scale for the Assessment of Positive Symptoms (SAPS-AH), negatively correlated with activation in the left temporal superior region in the French minus silence condition. This finding supports the hypothesis that auditory hallucinations compete with normal external speech for processing sites within the temporal cortex in schizophrenia
    [bibtex-entry]


  32. Jean-Baptiste Poline, Stephen C Strother, Ghislaine Dehaene-Lambertz, Gary F Egan, and Jack L Lancaster. Motivation and synthesis of the FIAC experiment: Reproducibility of fMRI results across expert analyses. Hum Brain Mapp, 27(5):351--359, May 2006. [WWW]
    Abstract: The Functional Imaging Analysis Contest (FIAC) culminated in the FIAC Workshop held at the 11th Annual Meeting of the Organization for Human Brain Mapping in Toronto in 2005. This special issue summarizes various analyses used by contestants with a single functional magnetic resonance imaging (fMRI) study, a cortical-language study using sentence repetition. The results from the cognitive neuroscientists who developed the test-base language study, and report their data analysis, are complemented by expert analyses of the same test-base data by most of the major groups actively developing fMRI software packages. Analyses include many variants of the general linear model (GLM), cutting-edge spatial- and temporal-wavelets, permutation-based, and ICA approaches. A number of authors also include surface-based approaches. Several articles describe the important emerging areas of diagnostics for GLM analysis, multivariate predictive modeling, and functional connectivity analysis. While the FIAC did not achieve all of its goals, it helped identify new activation regions in the test-base data, and more important, through this special issue it illustrates the significant methods-driven variability that potentially exists in the literature. Variable results from different methods reported here should provide a cautionary note and motivate the Human Brain Mapping community to explore more thoroughly the methodologies they use for analyzing fMRI data. Hum Brain Mapp 27:351-359, 2006. (c) 2006 Wiley-Liss, Inc
    [bibtex-entry]


  33. Mariano Sigman and S Dehaene. Dynamics of the central bottleneck: dual-task and task uncertainty. PLoS Biol, 4, 2006. [PDF] [bibtex-entry]


  34. Marcin Szwed and Ehud Ahissar. Mapping the gates. Focus on Relationship between physiological response type (RA and SA) and vibrissal receptive field of neurons within the rat trigeminal ganglion.. J Neurophysiol, 95(5):2729--2730, May 2006. [WWW] [bibtex-entry]


  35. Marcin Szwed, Knarik Bagdasarian, Barak Blumenfeld, Omri Barak, Dori Derdikman, and Ehud Ahissar. Responses of trigeminal ganglion neurons to the radial distance of contact during active vibrissal touch.. J Neurophysiol, 95(2):791--802, February 2006. [WWW]
    Abstract: Rats explore their environment by actively moving their whiskers. Recently, we described how object location in the horizontal (front-back) axis is encoded by first-order neurons in the trigeminal ganglion (TG) by spike timing. Here we show how TG neurons encode object location along the radial coordinate, i.e., from the snout outward. Using extracellular recordings from urethane-anesthetized rats and electrically induced whisking, we found that TG neurons encode radial distance primarily by the number of spikes fired. When an object was positioned closer to the whisker root, all touch-selective neurons recorded fired more spikes. Some of these cells responded exclusively to objects located near the base of whiskers, signaling proximal touch by an identity (labeled-line) code. A number of tonic touch-selective neurons also decreased delays from touch to the first spike and decreased interspike intervals for closer object positions. Information theory analysis revealed that near-certainty discrimination between two objects separated by 30\% of the length of whiskers was possible for some single cells. However, encoding reliability was usually lower as a result of large trial-by-trial response variability. Our current findings, together with the identity coding suggested by anatomy for the vertical dimension and the temporal coding of the horizontal dimension, suggest that object location is encoded by separate neuronal variables along the three spatial dimensions: temporal for the horizontal, spatial for the vertical, and spike rate for the radial dimension.
    [bibtex-entry]


  36. Bertrand Thirion, Edouard Duchesnay, Edward Hubbard, Jessica Dubois, Jean-Baptiste Poline, Denis Lebihan, and Stanislas Dehaene. Inverse retinotopy: inferring the visual content of images from brain activation patterns. Neuroimage, 33(4):1104--1116, December 2006. [WWW] [PDF]
    Abstract: Traditional inference in neuroimaging consists in describing brain activations elicited and modulated by different kinds of stimuli. Recently, however, paradigms have been studied in which the converse operation is performed, thus inferring behavioral or mental states associated with activation images. Here, we use the well-known retinotopy of the visual cortex to infer the visual content of real or imaginary scenes from the brain activation patterns that they elicit. We present two decoding algorithms: an explicit technique, based on the current knowledge of the retinotopic structure of the visual areas, and an implicit technique, based on supervised classifiers. Both algorithms predicted the stimulus identity with significant accuracy. Furthermore, we extend this principle to mental imagery data: in five data sets, our algorithms could reconstruct and predict with significant accuracy a pattern imagined by the subjects
    [bibtex-entry]


  37. Fabien Vinckier, Lionel Naccache, Caroline Papeix, Joaquim Forget, Valerie Hahn-Barma, Stanislas Dehaene, and Laurent Cohen. What and where in word reading: ventral coding of written words revealed by parietal atrophy. J Cogn Neurosci, 18(12):1998--2012, December 2006. [WWW] [PDF]
    Abstract: The visual system of literate adults develops a remarkable perceptual expertise for printed words. To delineate the aspects of this competence intrinsic to the occipitotemporal "what" pathway, we studied a patient with bilateral lesions of the occipitoparietal "where" pathway. Depending on critical geometric features of the display (rotation angle, letter spacing, mirror reversal, etc.), she switched from a good performance, when her intact ventral pathway was sufficient to encode words, to severely impaired reading, when her parietal lesions prevented the use of alternative reading strategies as a result of spatial and attentional impairments. In particular, reading was disrupted (a) by rotating word by more than 50 degrees , providing an approximation of the invariance range for words encoding in the ventral pathway; (b) by separating letters with double spaces, revealing the limits of letter grouping into perceptual wholes; (c) by mirror-reversing words, showing that words escape the default mirror-invariant representation of visual objects in the ventral pathway. Moreover, because of her parietal lesions, she was unable to discriminate mirror images of common objects, although she was excellent with reversible pseudowords, confirming that the breaking of mirror symmetry was intrinsic to the occipitotemporal cortex. Thus, charting the display conditions associated with preserved or impaired performance allowed us to infer properties of word coding in the normal ventral pathway and to delineate the roles of the parietal lobes in single-word recognition
    [bibtex-entry]


  38. Anna Juliet Wilson, Stanislas Dehaene, Philippe Pinel, Susannah Revkin, Laurent Cohen, and David Cohen. Principles underlying the design of The Number Race, an adaptive computer game for remediation of dyscalculia. Behav Brain Funct, 2(1):19, 2006. [WWW] [PDF]
    Abstract: ABSTRACT: BACKGROUND: Adaptive game software has been successful in remediation of dyslexia. Here we describe the cognitive and algorithmic principles underlying the development of similar software for dyscalculia. Our software is based on current understanding of the cerebral representation of number and the hypotheses that dyscalculia is due to a "core deficit" in number sense or in the link between number sense and symbolic number representations. METHODS: "The Number Race" software trains children on an entertaining numerical comparison task, by presenting problems adapted to the performance level of the individual child. We report full mathematical specifications of the algorithm used, which relies on an internal model of the child's knowledge in a multidimensional "learning space" consisting of three difficulty dimensions: numerical distance, response deadline, and conceptual complexity (from non-symbolic numerosity processing to increasingly complex symbolic operations). RESULTS: The performance of the software was evaluated both by mathematical simulations and by five weeks of use by nine children with mathematical learning difficulties. The results indicate that the software adapts well to varying levels of initial knowledge and learning speeds. Feedback from children, parents and teachers was positive. A companion article 1 describes the evolution of number sense and arithmetic scores before and after training. CONCLUSION: The software, open-source and freely available online, is designed for learning disabled children aged 5-8, and may also be useful for general instruction of normal preschool children. The learning algorithm reported is highly general, and may be applied in other domains
    [bibtex-entry]


  39. Anna Juliet Wilson, Susannah Revkin, David Cohen, Laurent Cohen, and Stanislas Dehaene. An open trial assessment of The Number Race, an adaptive computer game for remediation of dyscalculia. Behav Brain Funct, 2(1):20, 2006. [WWW] [PDF]
    Abstract: ABSTRACT: BACKGROUND: In a companion article 1, we described the development and evaluation of software designed to remediate dyscalculia. This software is based on the hypothesis that dyscalculia is due to a "core deficit" in number sense or in its access via symbolic information. Here we review the evidence for this hypothesis, and present results from an initial open-trial test of the software in a sample of nine 7-9 year old children with mathematical difficulties. METHODS: Children completed adaptive training on numerical comparison for half an hour a day, four days a week over a period of five-weeks. They were tested before and after intervention on their performance in core numerical tasks: counting, transcoding, base-10 comprehension, enumeration, addition, subtraction, and symbolic and non-symbolic numerical comparison. RESULTS: Children showed specific increases in performance on core number sense tasks. Speed of subitizing and numerical comparison increased by several hundred msec. Subtraction accuracy increased by an average of 23\%. Performance on addition and base-10 comprehension tasks did not improve over the period of the study. CONCLUSION: Initial open-trial testing showed promising results, and suggested that the software was successful in increasing number sense over the short period of the study. However these results need to be followed up with larger, controlled studies. The issues of transfer to higher-level tasks, and of the best developmental time window for intervention also need to be addressed
    [bibtex-entry]


Conference proceedings
  1. Christophe Pallier. Imagerie cérébrale du bilinguisme et de l'apprentissage des langues. In Frédéric Bimbot, editor, Actes des XXVIe journées d'études sur la parole (JEP), pages 555--556, 2006.
    Note: Dinard. [PDF] [bibtex-entry]


  2. Bertrand Thirion, Edouard Duchesnay, Edward Hubbard, Jessica Dubois, J-B Poline, and Stanislas Dehaene. Reading the brain visual system as an inverse problem. In 3rd IEEE International Symposium on Biomedical Imaging: Nano to Macro, 2006., pages 1060--1063, 2006. IEEE. [bibtex-entry]



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