Publications of year 2008
  1. P Picq, L Sagart, Ghislaine Dehaene-Lambertz, and C. Lestienne. La plus belle histoire du langage. Seuil, 2008. [bibtex-entry]

  1. Anne-Dominique Devauchelle. Exploration du réseau cérébral impliqué dans les traitements syntaxiques et lexico-sémantiques des phrases. PhD thesis, Université Paris VI, 2008.
    Note: Supervised by Christophe Pallier and Stanislas Dehaene. [PDF] [bibtex-entry]

Book chapters
  1. Jean-Pierre Changeux and Stanislas Dehaene. The neuronal workspace model: conscious processing and learning. In R.Menzel, editor,Learning and Memory: A Comprehensive Reference. Elsevier, 2008. [PDF] [bibtex-entry]

  2. Laurent Cohen, Anna Wilson, Véronique Izard, and Stanislas Dehaene. Acalculia and Gerstman's syndrome. In Cognitive and Behavioral Neurology of Stroke, pages 125-147. Cambridge University Press, 2008. [PDF] [bibtex-entry]

  3. Stanislas Dehaene. Cerebral constraints in reading and arithmetic: Education as a «neuronal recycling» process.. In The educated brain, pages pp 232-248. Cambridge University Press, 2008. [PDF] [bibtex-entry]

  4. Stanislas Dehaene. Conscious and Nonconscious Processes Distinct Forms of Evidence Accumulation?. In Strüngmann Forum Report: Better Than Conscious? Decision Making, the Human Mind, and Implications For Institutions, pages 21-49. MIT Press, 2008. [PDF] [bibtex-entry]

  5. Sid Kouider and S Dehaene. Levels of processing during non-conscious perception: a critical review of visual masking. In Mental processes in the human brain, pages 155-185. Oxford University Press, 2008. [PDF] [bibtex-entry]

  6. M. Platt, P. Dayan, S. Dehaene, K. McCabe, R. Menzel, E. Phelps, H. Plassmann, R. Ratcliff, M. Shadlen, and W. Singer. Neuronal correlates of decision making. In Christoph Engel and Wolf Singer, editors,The Strüngmann Forum Report. Better than conscious? Decision making, the human mind, and implications for institutions, pages 125-154. 2008. [PDF] [bibtex-entry]

Articles in journals
  1. Jamila Andoh, Eric Artiges, Christophe Pallier, Denis Rivière, Jean-Francois Mangin, Marie-Laure Paillère-Martinot, and Jean-Luc Martinot. Priming Frequencies of Transcranial Magnetic Stimulation over Wernicke's Area Modulate Word Detection.. Cereb Cortex, 18(1):210--216, January 2008. [WWW] [PDF]
    Abstract: Priming stimulations have shown powerful effects on motor cortex behavior. However, the effects over language areas have not been explored. We assessed the effects of different priming frequencies of repetitive transcranial magnetic stimulation (rTMS), 1 Hz rTMS or 50 Hz bursts of rTMS (theta burst stimulation [TBS]), on temporoparietal language areas (i.e., Wernicke's area) localized with functional magnetic resonance imaging. Functional maps were acquired during an auditory word-detection task with native or foreign language sentences in 14 healthy men. Frameless stereotaxy was used to guide the transcranial magnetic stimulation coil position over Wernicke's area. Active and placebo randomized sessions of priming stimulations (1 Hz rTMS or TBS) were applied at rest, and response times (RTs) were recorded during the auditory word-detection task performed subsequently with 1 Hz rTMS. Individual anatomofunctional maps localized activation in Wernicke's area. Repeated-measure analysis of variance for RTs revealed that priming with 1 Hz rTMS facilitated the detection of native words, whereas priming with TBS facilitated the detection of foreign words. Consistent with motor cortex studies, these findings suggest that priming frequency plays a crucial role in word detection in the auditory stream.

  2. Marcello Buiatti and Marco Buiatti. Chance vs. Necessity in Living Systems: A False Antinomy. Biology Forum, 101:29-66, 2008. [PDF] [bibtex-entry]

  3. Marco Buiatti. The correlated nature of large scale brain activity unveiled by the resting brain. Biology Forum 101, 101:353-73, 2008. [PDF] [bibtex-entry]

  4. Laurent Cohen, Stanislas Dehaene, Fabien Vinckier, Antoinette Jobert, and Alexandra Montavont. Reading normal and degraded words: contribution of the dorsal and ventral visual pathways. Neuroimage, 40(1):353--366, March 2008. [WWW] [PDF]
    Abstract: Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipito-temporal pathway collectively known as the visual word form area. This expertise is thought to arise from perceptual learning mechanisms that extract informative features from the input strings. The perceptual expertise hypothesis leads to two predictions: (1) parallel word recognition, based on the ventral visual system, should be limited to words displayed in a familiar format (foveal horizontal words with normally spaced letters); (2) words displayed in formats outside this field of expertise should be read serially, under supervision of dorsal parietal attention systems. We presented adult readers with words that were progressively degraded in three different ways (word rotation, letter spacing, and displacement to the visual periphery). Behaviorally, we identified degradation thresholds above which reading difficulty increased non-linearly, with the concomitant emergence of a word length effect on reading latencies reflecting serial reading strategies. fMRI activations were correlated with reading difficulty in bilateral occipito-temporal and parietal regions, reflecting the strategies required to identify degraded words. A core region of the intraparietal cortex was engaged in all modes of degradation. Furthermore, in the ventral pathway, word degradation led to an amplification of activation in the posterior visual word form area, at a level thought to encode single letters. We also found an effect of word length restricted to highly degraded words in bilateral occipitoparietal regions. Those results clarify when and how the ventral parallel visual word form system needs to be supplemented by the deployment of dorsal serial reading strategies

  5. Guido Corallo, Jérôme Sackur, Stanislas Dehaene, and Mariano Sigman. Limits on introspection: distorted subjective time during the dual-task bottleneck. Psychol Sci, 19(11):1110--1117, November 2008. [WWW] [PDF]
    Abstract: Which cognitive processes are accessible to conscious report? To study the limits of conscious reportability, we designed a novel method of quantified introspection, in which subjects were asked, after each trial of a standard cognitive task, to estimate the time spent completing the task. We then applied classical mental-chronometry techniques, such as the additive-factors method, to analyze these introspective estimates of response time. We demonstrate that introspective response time can be a sensitive measure, tightly correlated with objective response time in a single-task context. In a psychological-refractory-period task, however, the objective processing delay resulting from interference by a second concurrent task is totally absent from introspective estimates. These results suggest that introspective estimates of time spent on a task tightly correlate with the period of availability of central processing resources

  6. Stanislas Dehaene, Véronique Izard, Elizabeth Spelke, and Pierre Pica. Log or linear? Distinct intuitions of the number scale in Western and Amazonian indigene cultures. Science, 320(5880):1217--1220, May 2008. [WWW] [PDF]
    Abstract: The mapping of numbers onto space is fundamental to measurement and to mathematics. Is this mapping a cultural invention or a universal intuition shared by all humans regardless of culture and education? We probed number-space mappings in the Mundurucu, an Amazonian indigene group with a reduced numerical lexicon and little or no formal education. At all ages, the Mundurucu mapped symbolic and nonsymbolic numbers onto a logarithmic scale, whereas Western adults used linear mapping with small or symbolic numbers and logarithmic mapping when numbers were presented nonsymbolically under conditions that discouraged counting. This indicates that the mapping of numbers onto space is a universal intuition and that this initial intuition of number is logarithmic. The concept of a linear number line appears to be a cultural invention that fails to develop in the absence of formal education

  7. Ghislaine Dehaene-Lambertz, Lucie Hertz-Pannier, Jessica Dubois, and Stanislas Dehaene. How Does Early Brain Organization Promote Language Acquisition in Humans?. European Review, 16(4):399--411, 2008. [PDF] [bibtex-entry]

  8. J. Dubois, M. Benders, C. Borradori-Tolsa, A. Cachia, F. Lazeyras, R. Ha-Vinh Leuchter, S. V. Sizonenko, S. K. Warfield, J. F. Mangin, and P. S. Hüppi. Primary cortical folding in the human newborn: an early marker of later functional development.. Brain, 131(Pt 8):2028--2041, August 2008. [WWW] [PDF]
    Abstract: In the human brain, the morphology of cortical gyri and sulci is complex and variable among individuals, and it may reflect pathological functioning with specific abnormalities observed in certain developmental and neuropsychiatric disorders. Since cortical folding occurs early during brain development, these structural abnormalities might be present long before the appearance of functional symptoms. So far, the precise mechanisms responsible for such alteration in the convolution pattern during intra-uterine or post-natal development are still poorly understood. Here we compared anatomical and functional brain development in vivo among 45 premature newborns who experienced different intra-uterine environments: 22 normal singletons, 12 twins and 11 newborns with intrauterine growth restriction (IUGR). Using magnetic resonance imaging (MRI) and dedicated post-processing tools, we investigated early disturbances in cortical formation at birth, over the developmental period critical for the emergence of convolutions (26-36 weeks of gestational age), and defined early 'endophenotypes' of sulcal development. We demonstrated that twins have a delayed but harmonious maturation, with reduced surface and sulcation index compared to singletons, whereas the gyrification of IUGR newborns is discordant to the normal developmental trajectory, with a more pronounced reduction of surface in relation to the sulcation index compared to normal newborns. Furthermore, we showed that these structural measurements of the brain at birth are predictors of infants' outcome at term equivalent age, for MRI-based cerebral volumes and neurobehavioural development evaluated with the assessment of preterm infant's behaviour (APIB).

  9. J. Dubois, M. Benders, A. Cachia, F. Lazeyras, R. Ha-Vinh Leuchter, S. V. Sizonenko, C. Borradori-Tolsa, J. F. Mangin, and P. S. Hüppi. Mapping the early cortical folding process in the preterm newborn brain.. Cereb Cortex, 18(6):1444--1454, June 2008. [WWW] [PDF]
    Abstract: In the developing human brain, the cortical sulci formation is a complex process starting from 14 weeks of gestation onward. The potential influence of underlying mechanisms (genetic, epigenetic, mechanical or environmental) is still poorly understood, because reliable quantification in vivo of the early folding is lacking. In this study, we investigate the sulcal emergence noninvasively in 35 preterm newborns, by applying dedicated postprocessing tools to magnetic resonance images acquired shortly after birth over a developmental period critical for the human cortex maturation (26-36 weeks of age). Through the original three-dimensional reconstruction of the interface between developing cortex and white matter and correlation with volumetric measurements, we document early sulcation in vivo, and quantify changes with age, gender, and the presence of small white matter lesions. We observe a trend towards lower cortical surface, smaller cortex, and white matter volumes, but equivalent sulcation in females compared with males. By precisely mapping the sulci, we highlight interindividual variability in time appearance and interhemispherical asymmetries, with a larger right superior temporal sulcus than the left. Thus, such an approach, included in a longitudinal follow-up, may provide early indicators on the structural basis of cortical functional specialization and abnormalities induced by genetic and environmental factors.

  10. Jessica Dubois, Ghislaine Dehaene-Lambertz, Muriel Perrin, Jean-François Mangin, Yann Cointepas, Edouard Duchesnay, Denis Le Bihan, and Lucie Hertz-Pannier. Asynchrony of the early maturation of white matter bundles in healthy infants: quantitative landmarks revealed noninvasively by diffusion tensor imaging. Hum Brain Mapp, 29(1):14--27, January 2008. [WWW] [PDF]
    Abstract: Normal cognitive development in infants follows a well-known temporal sequence, which is assumed to be correlated with the structural maturation of underlying functional networks. Postmortem studies and, more recently, structural MR imaging studies have described qualitatively the heterogeneous spatiotemporal progression of white matter myelination. However, in vivo quantification of the maturation phases of fiber bundles is still lacking. We used noninvasive diffusion tensor MR imaging and tractography in twenty-three 1-4-month-old healthy infants to quantify the early maturation of the main cerebral fascicles. A specific maturation model, based on the respective roles of different maturational processes on the diffusion phenomena, was designed to highlight asynchronous maturation across bundles by evaluating the time-course of mean diffusivity and anisotropy changes over the considered developmental period. Using an original approach, a progression of maturation in four relative stages was determined in each tract by estimating the maturation state and speed, from the diffusion indices over the infants group compared with an adults group on one hand, and in each tract compared with the average over bundles on the other hand. Results were coherent with, and extended previous findings in 8 of 11 bundles, showing the anterior limb of the internal capsule and cingulum as the most immature, followed by the optic radiations, arcuate and inferior longitudinal fascicles, then the spinothalamic tract and fornix, and finally the corticospinal tract as the most mature bundle. Thus, this approach provides new quantitative landmarks for further noninvasive research on brain-behavior relationships during normal and abnormal development

  11. Jessica Dubois, Ghislaine Dehaene-Lambertz, Catherine Soarès, Yann Cointepas, Denis Le Bihan, and Lucie Hertz-Pannier. Microstructural correlates of infant functional development: example of the visual pathways. Journal of Neuroscience, 28(8):1943--1948, February 2008. [WWW] [PDF]
    Abstract: The development of cognitive functions during childhood relies on several neuroanatomical maturation processes. Among these processes is myelination of the white matter pathways, which speeds up electrical conduction. Quantitative indices of such structural processes can be obtained in vivo with diffusion tensor imaging (DTI), but their physiological significance remains uncertain. Here, we investigated the microstructural correlates of early functional development by combining DTI and visual event-related potentials (VEPs) in 15 one- to 4-month-old healthy infants. Interindividual variations of the apparent conduction speed, computed from the latency of the first positive VEP wave (P1), were significantly correlated with the infants' age and DTI indices measured in the optic radiations. This demonstrates that fractional anisotropy and transverse diffusivity are structural markers of functionally efficient myelination. Moreover, these indices computed along the optic radiations showed an early wave of maturation in the anterior region, with the posterior region catching up later in development, which suggests two asynchronous fronts of myelination in both the geniculocortical and corticogeniculate fibers. Thus, in addition to microstructural information, DTI provides noninvasive exquisite information on the functional development of the brain in human infants

  12. J. Dubois, L. Hertz-Pannier, A. Cachia, J.-F. Mangin, D. Le Bihan, and Ghislaine Dehaene-Lambertz. Structural Asymmetries in the Infant Language and Sensori-Motor Networks. Cerebral Cortex, June 2008. [WWW] [PDF]
    Abstract: Both language capacity and strongly lateralized hand preference are among the most intriguing particularities of the human species. They are associated in the adult brain with functional and anatomical hemispheric asymmetries in the speech perception-production network and in the sensori-motor system. Only studies in early life can help us to understand how such asymmetries arise during brain development, and to which point structural left-right differences are the source or the consequence of functional lateralization. In this study, we aimed to provide new in vivo structural markers of hemispheric asymmetries in infants from 1 to 4 months of age, with diffusion tensor imaging. We used 3 complementary analysis methods based on local diffusion indices and spatial localizations of tracts. After a prospective approach over the whole brain, we demonstrated early leftward asymmetries in the arcuate fasciculus and in the cortico-spinal tract. These results suggest that the early macroscopic geometry, microscopic organization, and maturation of these white matter bundles are related to the development of later functional lateralization

  13. Evelyn Eger, Christian A Kell, and Andreas Kleinschmidt. Graded size sensitivity of object-exemplar-evoked activity patterns within human LOC subregions.. J Neurophysiol, 100(4):2038--2047, October 2008. [WWW] [PDF]
    Abstract: A central issue for understanding visual object recognition is how the cortical hierarchy represents incoming sensory information and transforms it across successive processing stages. The format of object representation in the human brain has thus far mostly been studied using adaptation paradigms because the neuronal layout of object selectivities was thought to be beyond the resolution of conventional functional MRI (fMRI). Recently, however, multivariate pattern recognition succeeded in discriminating fMRI responses of object-selective cortex to different object exemplars within a given category. Here, we use increased spatial fMRI resolution to explore size sensitivity and tolerance to size change of response patterns evoked by object exemplars across a range of three sizes. Results from Support Vector Classification on responses of the human lateral occipital complex (LOC) show that discrimination of size (for a given object) and discrimination of objects across changes in size depended on the amount of size difference. Even across the largest amount of size change, accuracy for generalization was still significant in LOC, whereas the same comparison was at chance performance in early visual (calcarine) cortex. Analyzing subregions, we further found an anterior-posterior gradient in the degree of size sensitivity and size generalization within the posterior-dorsal and anterior-ventral parts of LOC. These results speak against fully size-invariant representation of object information in human LOC and are hence congruent with findings in monkeys showing object identity and size information in population activity of inferotemporal cortex. Moreover, these results provide evidence for a fine-grained functional heterogeneity within human LOC beyond the commonly used LO/fusiform subdivision.

  14. Stéphane Epelbaum, Philippe Pinel, Raphael Gaillard, Christine Delmaire, Muriel Perrin, Sophie Dupont, Stanislas Dehaene, and Laurent Cohen. Pure alexia as a disconnection syndrome: new diffusion imaging evidence for an old concept.. Cortex, 44(8):962--974, September 2008. [WWW] [PDF]
    Abstract: Functional neuroimaging and studies of brain-damaged patients made it possible to delineate the main components of the cerebral system for word reading. However, the anatomical connections subtending the flow of information within this network are still poorly defined. Here we study the connectivity of the Visual Word Form Area (VWFA), a pivotal component of the reading network achieving the invariant identification of letter strings, and reproducibly located in the left lateral occipitotemporal sulcus. Diffusion images and functional imaging data were gathered in a patient who developed pure alexia following a small surgical lesion in the vicinity of his VWFA. We had a unique opportunity to compare images obtained before, early after, and late after surgery. Analysis of diffusion images with white matter tractography and voxel-based morphometry showed that the VWFA was mainly linked to the occipital cortex through the inferior longitudinal fasciculus (ILF), and to perisylvian language areas (supramarginal gyrus) through the arcuate fasciculus. After surgery, we observed the progressive and selective degeneration of the ILF, while the VWFA was anatomically intact. This allowed us to establish the critical causal role of this fiber tract in normal reading, and to show that its disruption is one pathophysiological mechanism of pure alexia, thus clarifying a long-standing debate on the role of disconnection in neurocognitive disorders.

  15. Ludovic Ferrand, Patrick Bonin, Alain Méot, Maria Augustinova, Boris New, Christophe Pallier, and Marc Brysbaert. Age-of-acquisition and subjective frequency estimates for all generally known monosyllabic French words and their relation with other psycholinguistic variables.. Behav Res Methods, 40(4):1049--1054, November 2008. [WWW] [PDF]
    Abstract: Ratings for age of acquisition (AoA) and subjective frequency were collected for the 1,493 monosyllabic French words that were most known to French students. AoA ratings were collected by asking participants to estimate in years the age at which they learned each word. Subjective frequency ratings were collected on a 7-point scale, ranging from never encountered to encountered several times daily. The results were analyzed to address the relationship between AoA and subjective frequency ratings with other psycholinguistic variables (objective frequency, imageability, number of letters, and number of orthographic neighbors). The results showed high reliability ratings with other databases. Supplementary materials for this study may be downloaded from the Psychonomic Society's Archive of Norms, Stimuli, and Data,

  16. Grit Hein, Arjen Alink, Andreas Kleinschmidt, and Notger G Müller. The Attentional Blink Modulates Activity in the Early Visual Cortex.. J Cogn Neurosci, May 2008. [WWW] [PDF]
    Abstract: Abstract The attentional blink (AB) documents a particularly strong case of visual attentional competition, in which subjects' ability to identify a second target (T2) is significantly impaired when it is presented with a short SOA after a first target (T1). We used functional magnetic resonance imaging to investigate the impact of the AB on visual activity in individually defined retinotopic representations of the target stimuli. Our results show reduction of neural response in V3 and marginally in V2 and V1, paralleling the behavioral AB effect. Reduction of visual activity was accompanied by reduced neural response in the inferior parietal cortex. This indicates that attentional competition modulates activity in higher-order parietal regions and the early visual cortex, providing a plausible neural basis of the behavioral AB effect.

  17. Guido Hesselmann, Christian A Kell, Evelyn Eger, and Andreas Kleinschmidt. Spontaneous local variations in ongoing neural activity bias perceptual decisions.. Proc Natl Acad Sci U S A, 105(31):10984--10989, August 2008. [WWW] [PDF]
    Abstract: Neural variability in responding to identical repeated stimuli has been related to trial-by-trial fluctuations in ongoing activity, yet the neural and perceptual consequences of these fluctuations remain poorly understood. Using functional neuroimaging, we recorded brain activity in subjects who reported perceptual decisions on an ambiguous figure, Rubin's vase-faces picture, which was briefly presented at variable intervals of > or = 20 s. Prestimulus activity in the fusiform face area, a cortical region preferentially responding to faces, was higher when subjects subsequently perceived faces instead of the vase. This finding suggests that endogenous variations in prestimulus neuronal activity biased subsequent perceptual inference. Furnishing evidence that evoked sensory responses, we then went on to show that the pre- and poststimulus activity interact in a nonlinear way and the ensuing perceptual decisions depend upon the prestimulus context in which they occur.

  18. Guido Hesselmann, Christian A Kell, and Andreas Kleinschmidt. Ongoing activity fluctuations in hMT+ bias the perception of coherent visual motion.. Journal of Neuroscience, 28(53):14481--14485, December 2008. [WWW] [PDF]
    Abstract: We have recently shown that intrinsic fluctuations of ongoing activity during baseline have an impact on perceptual decisions reported for an ambiguous visual stimulus (Hesselmann et al., 2008). To test whether this result generalizes from the visual object domain to other perceptual and neural systems, the current study investigated the effect of ongoing signal fluctuations in motion-sensitive brain regions on the perception of coherent visual motion. We determined motion coherence thresholds individually for each subject using a dynamic random dot display. During functional magnetic resonance imaging (fMRI), brief events of subliminal, supraliminal, and periliminal coherent motion were presented with long and variable interstimulus intervals between them. On each trial, subjects reported whether they had perceived "coherent" or "random" motion, and fMRI signal time courses were analyzed separately as a function of stimulus and percept type. In the right motion-sensitive occipito-temporal cortex (hMT+), coherent percepts of periliminal stimuli yielded a larger stimulus-evoked response than random percepts. Prestimulus baseline activity in this region was also significantly higher in these coherent trials than in random trials. As in our previous study, however, the relation between ongoing and evoked activity was not additive but interacted with perceptual outcome. Our data thus suggest that endogenous fluctuations in baseline activity have a generic effect on subsequent perceptual decisions. Although mainstream analytical techniques used in functional neuroimaging do not capture this nonadditive effect of baseline on evoked response, it is in accord with postulates from theoretical frameworks as, for instance, predictive coding.

  19. Véronique Izard, Stanislas Dehaene, Pierre Pica, and Elizabeth Spelke. Response to Nunez. Science, 321:1293-1294, 2008. [PDF] [bibtex-entry]

  20. Véronique Izard and Stanislas Dehaene. Calibrating the mental number line. Cognition, pp 1221-47, August 2008. [WWW] [PDF]
    Abstract: Human adults are thought to possess two dissociable systems to represent numbers: an approximate quantity system akin to a mental number line, and a verbal system capable of representing numbers exactly. Here, we study the interface between these two systems using an estimation task. Observers were asked to estimate the approximate numerosity of dot arrays. We show that, in the absence of calibration, estimates are largely inaccurate: responses increase monotonically with numerosity, but underestimate the actual numerosity. However, insertion of a few inducer trials, in which participants are explicitly (and sometimes misleadingly) told that a given display contains 30 dots, is sufficient to calibrate their estimates on the whole range of stimuli. Based on these empirical results, we develop a model of the mapping between the numerical symbols and the representations of numerosity on the number line

  21. Véronique Izard, Ghislaine Dehaene-Lambertz, and Stanislas Dehaene. Distinct cerebral pathways for object identity and number in human infants. PLoS Biology, 6(2):e11, February 2008. [WWW] [PDF]
    Abstract: All humans, regardless of their culture and education, possess an intuitive understanding of number. Behavioural evidence suggests that numerical competence may be present early on in infancy. Here, we present brain-imaging evidence for distinct cerebral coding of number and object identity in 3-mo-old infants. We compared the visual event-related potentials evoked by unforeseen changes either in the identity of objects forming a set, or in the cardinal of this set. In adults and 4-y-old children, number sense relies on a dorsal system of bilateral intraparietal areas, different from the ventral occipitotemporal system sensitive to object identity. Scalp voltage topographies and cortical source modelling revealed a similar distinction in 3-mo-olds, with changes in object identity activating ventral temporal areas, whereas changes in number involved an additional right parietoprefrontal network. These results underscore the developmental continuity of number sense by pointing to early functional biases in brain organization that may channel subsequent learning to restricted brain areas

  22. Véronique Izard, Pierre Pica, Elizabeth Spelke, and Stanislas Dehaene. Comment les nombres se répartissent dans l'espace. Médecine sciences, 24, 2008. [PDF] [bibtex-entry]

  23. Véronique Izard, Pierre Pica, Elizabeth Spelke, and Stanislas Dehaene. Exact Equality and Successor Function: Two Key Concepts on the Path towards understanding Exact Numbers. Philosophical Psychology, 21(4):491--505, 2008. [PDF] [bibtex-entry]

  24. Roi Cohen Kadosh, Jan Lammertyn, and Véronique Izard. Are numbers special? An overview of chronometric, neuroimaging, developmental and comparative studies of magnitude representation.. Prog Neurobiol, 84(2):132--147, February 2008. [WWW] [PDF]
    Abstract: There is a current debate whether the human brain possesses a shared representation for various types of magnitude such as numerical quantities, physical size, or loudness. Here, we critically review evidence from chronometric, neuroimaging, developmental and comparative fields, and supplement it with a meta-analysis of the neuroimaging data. Together, based on such an integrative overview, we discuss limitations inherent in each approach, and the possibility whether shared, or distinct magnitude representation, or both representations exist.

  25. H. Laufs, J. Daunizeau, D. W. Carmichael, and A. Kleinschmidt. Recent advances in recording electrophysiological data simultaneously with magnetic resonance imaging.. Neuroimage, 40(2):515--528, April 2008. [WWW] [PDF]
    Abstract: Simultaneous recording of brain activity by different neurophysiological modalities can yield insights that reach beyond those obtained by each technique individually, even when compared to those from the post-hoc integration of results from each technique recorded sequentially. Success in the endeavour of real-time multimodal experiments requires special hardware and software as well as purpose-tailored experimental design and analysis strategies. Here, we review the key methodological issues in recording electrophysiological data in humans simultaneously with magnetic resonance imaging (MRI), focusing on recent technical and analytical advances in the field. Examples are derived from simultaneous electroencephalography (EEG) and electromyography (EMG) during functional MRI in cognitive and systems neuroscience as well as in clinical neurology, in particular in epilepsy and movement disorders. We conclude with an outlook on current and future efforts to achieve true integration of electrical and haemodynamic measures of neuronal activity using data fusion models.

  26. Salima Makni, Jérôme Idier, Thomas Vincent, Bertrand Thirion, Ghislaine Dehaene-Lambertz, and Philippe Ciuciu. A fully Bayesian approach to the parcel-based detection-estimation of brain activity in fMRI. Neuroimage, 41(3):941--969, July 2008. [WWW] [PDF]
    Abstract: Within-subject analysis in fMRI essentially addresses two problems, i.e., the detection of activated brain regions in response to an experimental task and the estimation of the underlying dynamics, also known as the characterisation of Hemodynamic response function (HRF). So far, both issues have been treated sequentially while it is known that the HRF model has a dramatic impact on the localisation of activations and that the HRF shape may vary from one region to another. In this paper, we conciliate both issues in a region-based joint detection-estimation framework that we develop in the Bayesian formalism. Instead of considering function basis to account for spatial variability, spatially adaptive General Linear Models are built upon region-based non-parametric estimation of brain dynamics. Regions are first identified as functionally homogeneous parcels in the mask of the grey matter using a specific procedure [Thirion, B., Flandin, G., Philippe Pinel, Roche, A., Ciuciu, P., Poline, J.-B., August 2006. Dealing with the shortcomings of spatial normalization: Multi-subject parcellation of fMRI datasets. Hum. Brain Mapp. 27 (8), 678-693.]. Then, in each parcel, prior information is embedded to constrain this estimation. Detection is achieved by modelling activating, deactivating and non-activating voxels through mixture models within each parcel. From the posterior distribution, we infer upon the model parameters using Markov Chain Monte Carlo (MCMC) techniques. Bayesian model comparison allows us to emphasize on artificial datasets first that inhomogeneous gamma-Gaussian mixture models outperform Gaussian mixtures in terms of sensitivity/specificity trade-off and second that it is worthwhile modelling serial correlation through an AR(1) noise process at low signal-to-noise (SNR) ratio. Our approach is then validated on an fMRI experiment that studies habituation to auditory sentence repetition. This phenomenon is clearly recovered as well as the hierarchical temporal organisation of the superior temporal sulcus, which is directly derived from the parcel-based HRF estimates

  27. Sharon Peperkamp, Inga Vendelin, and Kimihiro Nakamura. On the perceptual origin of loanword adaptations: experimental evidence from Japanese. Phonology, 25:129-64, 2008. [PDF] [bibtex-entry]

  28. David Poeppel, William J. Idsardi, and Virginie van Wassenhove. Speech perception at the interface of neurobiology and linguistics.. Philos Trans R Soc Lond B Biol Sci, 363(1493):1071--1086, March 2008. [WWW]
    Abstract: Speech perception consists of a set of computations that take continuously varying acoustic waveforms as input and generate discrete representations that make contact with the lexical representations stored in long-term memory as output. Because the perceptual objects that are recognized by the speech perception enter into subsequent linguistic computation, the format that is used for lexical representation and processing fundamentally constrains the speech perceptual processes. Consequently, theories of speech perception must, at some level, be tightly linked to theories of lexical representation. Minimally, speech perception must yield representations that smoothly and rapidly interface with stored lexical items. Adopting the perspective of Marr, we argue and provide neurobiological and psychophysical evidence for the following research programme. First, at the implementational level, speech perception is a multi-time resolution process, with perceptual analyses occurring concurrently on at least two time scales (approx. 20-80 ms, approx. 150-300 ms), commensurate with (sub)segmental and syllabic analyses, respectively. Second, at the algorithmic level, we suggest that perception proceeds on the basis of internal forward models, or uses an 'analysis-by-synthesis' approach. Third, at the computational level (in the sense of Marr), the theory of lexical representation that we adopt is principally informed by phonological research and assumes that words are represented in the mental lexicon in terms of sequences of discrete segments composed of distinctive features. One important goal of the research programme is to develop linking hypotheses between putative neurobiological primitives (e.g. temporal primitives) and those primitives derived from linguistic inquiry, to arrive ultimately at a biologically sensible and theoretically satisfying model of representation and computation in speech.

  29. Cyril Poupon, Alexis Roche, Jessica Dubois, Jean-François Mangin, and Fabrice Poupon. Real-time MR diffusion tensor and Q-ball imaging using Kalman filtering.. Med Image Anal, 12(5):527--534, October 2008. [WWW] [PDF]
    Abstract: Diffusion magnetic resonance imaging (dMRI) has become an established research tool for the investigation of tissue structure and orientation. In this paper, we present a method for real-time processing of diffusion tensor and Q-ball imaging. The basic idea is to use Kalman filtering framework to fit either the linear tensor or Q-ball model. Because the Kalman filter is designed to be an incremental algorithm, it naturally enables updating the model estimate after the acquisition of any new diffusion-weighted volume. Processing diffusion models and maps during ongoing scans provides a new useful tool for clinicians, especially when it is not possible to predict how long a subject may remain still in the magnet. First, we introduce the general linear models corresponding to the two diffusion tensor and analytical Q-ball models of interest. Then, we present the Kalman filtering framework and we focus on the optimization of the diffusion orientation sets in order to speed up the convergence of the online processing. Last, we give some results on a healthy volunteer for the online tensor and the Q-ball model, and we make some comparisons with the conventional offline techniques used in the literature. We could achieve full real-time for diffusion tensor imaging and deferred time for Q-ball imaging, using a single workstation.

  30. Cécile Rabrait, Philippe Ciuciu, Alejandro Ribés, Cyril Poupon, Patrick Le Roux, Ghislaine Dehaene-Lambertz, D. Le Bihan, and F. Lethimonnier. High temporal resolution functional MRI using parallel echo volumar imaging. J Magn Reson Imaging, 27(4):744--753, April 2008. [WWW] [PDF]
    Abstract: PURPOSE: To combine parallel imaging with 3D single-shot acquisition (echo volumar imaging, EVI) in order to acquire high temporal resolution volumar functional MRI (fMRI) data. MATERIALS AND METHODS: An improved EVI sequence was associated with parallel acquisition and field of view reduction in order to acquire a large brain volume in 200 msec. Temporal stability and functional sensitivity were increased through optimization of all imaging parameters and Tikhonov regularization of parallel reconstruction. Two human volunteers were scanned with parallel EVI in a 1.5T whole-body MR system, while submitted to a slow event-related auditory paradigm. RESULTS: Thanks to parallel acquisition, the EVI volumes display a low level of geometric distortions and signal losses. After removal of low-frequency drifts and physiological artifacts, activations were detected in the temporal lobes of both volunteers and voxelwise hemodynamic response functions (HRF) could be computed. On these HRF different habituation behaviors in response to sentence repetition could be identified. CONCLUSION: This work demonstrates the feasibility of high temporal resolution 3D fMRI with parallel EVI. Combined with advanced estimation tools, this acquisition method should prove useful to measure neural activity timing differences or study the nonlinearities and nonstationarities of the BOLD response

  31. Susannah K Revkin, Manuela Piazza, Véronique Izard, Laurent Cohen, and Stanislas Dehaene. Does subitizing reflect numerical estimation?. Psychol Sci, 19(6):607--614, June 2008. [WWW] [PDF]
    Abstract: Subitizing is the rapid and accurate enumeration of small sets (up to 3-4 items). Although subitizing has been studied extensively since its first description about 100 years ago, its underlying mechanisms remain debated. One hypothesis proposes that subitizing results from numerical estimation mechanisms that, according to Weber's law, operate with high precision for small numbers. Alternatively, subitizing might rely on a distinct process dedicated to small numerosities. In this study, we tested the hypothesis that there is a shared estimation system for small and large quantities in human adults, using a masked forced-choice paradigm in which participants named the numerosity of displays taken from sets matched for discrimination difficulty; one set ranged from 1 through 8 items, and the other ranged from 10 through 80 items. Results showed a clear violation of Weber's law (much higher precision over numerosities 1-4 than over numerosities 10-40), thus refuting the single-estimation-system hypothesis and supporting the notion of a dedicated mechanism for apprehending small numerosities

  32. Susannah K Revkin, Manuela Piazza, Véronique Izard, Laura Zamarian, Elfriede Karner, and Margarete Delazer. Verbal numerosity estimation deficit in the context of spared semantic representation of numbers: a neuropsychological study of a patient with frontal lesions.. Neuropsychologia, 46(10):2463--2475, August 2008. [WWW] [PDF]
    Abstract: Patients with frontal lobe damage have been shown to produce implausible answers in cognitive estimation, a task requiring approximate answers to quantity-related questions of general semantic knowledge. We investigated a patient with frontal lobe damage who presented executive deficits and difficulties in cognitive estimation. The patient also showed difficulties in verbal numerosity estimation (approximately evaluating the quantity of visually presented sets of items), as he produced extreme answers well outside healthy participants' range of answers. A series of tasks evidenced intact number processing and well preserved semantic representation of numbers. Detailed investigation of estimation processes suggested a deficit at the level of translation from an intact semantic representation of numbers to output, whether verbal or non-symbolic. This case study allows disentangling different processes involved in estimation and contributes to a better understanding of the cognitive estimation deficits frequently reported for patients with frontal lesions.

  33. Jérôme Sackur, Lionel Naccache, Pascale Pradat-Diehl, Philippe Azouvi, Dominique Mazevet, Rose Katz, Laurent Cohen, and Stanislas Dehaene. Semantic processing of neglected numbers.. Cortex, 44(6):673--682, June 2008. [WWW] [PDF]
    Abstract: While neglected stimuli can still be processed, few studies have directly addressed the issue of the unconscious access to semantics. In order to clarify this issue, we engaged four patients with unilateral left spatial neglect in a number comparison task. Each target number was preceded by a lateralized number prime, either in the intact or neglected hemifield (HF). Both group analyses and the intensive study of a single patient show that left (neglected) as well as right (consciously perceived) number primes affect performance: primes representing quantities that fall on the same side of the reference as the target lead to faster categorization. This congruency effect is highly suggestive of numerical semantic processing of neglected stimuli. Absence of conscious perception of neglected primes was evaluated using a combination of subjective and objective measures of performance in forced-choice tasks.

  34. Mariano Sigman and Stanislas Dehaene. Brain mechanisms of serial and parallel processing during dual-task performance. Journal of Neuroscience, 28(30):7585--7598, July 2008. [WWW] [PDF]
    Abstract: The psychological refractory period (PRP) refers to the fact that humans typically cannot perform two tasks at once. Behavioral experiments have led to the proposal that, in fact, peripheral perceptual and motor stages continue to operate in parallel, and that only a central decision stage imposes a serial bottleneck. We tested this model using neuroimaging methods combined with innovative time-sensitive analysis tools. Subjects performed a dual-task visual-auditory paradigm in which a delay of 300 ms was injected into the auditory task either within or outside of the dual-task interference period. Event-related potentials indicated that the first approximately 250 ms of processing were insensitive to dual-task interference, and that the PRP was mainly reflected in a delayed global component. By a clustering analysis based on time-resolved functional magnetic resonance imaging, we identified networks with qualitatively different timing properties: sensory areas tracked the objective time of stimulus presentation, a bilateral parietoprefrontal network correlated with the PRP delay, and an extended bilateral network that included bilateral posterior parietal cortex, premotor cortex, supplementary motor area, anterior part of the insula, and cerebellum was shared by both tasks during the extent of dual-task performance. The results provide physiological evidence for the coexistence of serial and parallel processes within a cognitive task

  35. Mariano Sigman, Jérôme Sackur, Antoine Del Cul, and Stanislas Dehaene. Illusory displacement due to object substitution near the consciousness threshold. Journal of Vision, 8(1):1?10, 2008. [WWW] [PDF]
    Abstract: A briefly presented target shape can be made invisible by the subsequent presentation of a mask that replaces the target. While varying the target–mask interval in order to investigate perception near the consciousness threshold,we discovered a novel visual illusion. At some intervals,the target is clearly visible,but its location is misperceived. By manipulating the mask's size and target's position,we demonstrate that the perceived target location is always displaced to the boundary of a virtual surface defined by the mask contours. Thus,mutual exclusion of surfaces appears as a cause of masking

  36. Virginie van Wassenhove, Dean V. Buonomano, Shinsuke Shimojo, and Ladan Shams. Distortions of subjective time perception within and across senses.. PLoS One, 3(1):e1437, 2008. [WWW]
    Abstract: The ability to estimate the passage of time is of fundamental importance for perceptual and cognitive processes. One experience of time is the perception of duration, which is not isomorphic to physical duration and can be distorted by a number of factors. Yet, the critical features generating these perceptual shifts in subjective duration are not understood.We used prospective duration judgments within and across sensory modalities to examine the effect of stimulus predictability and feature change on the perception of duration. First, we found robust distortions of perceived duration in auditory, visual and auditory-visual presentations despite the predictability of the feature changes in the stimuli. For example, a looming disc embedded in a series of steady discs led to time dilation, whereas a steady disc embedded in a series of looming discs led to time compression. Second, we addressed whether visual (auditory) inputs could alter the perception of duration of auditory (visual) inputs. When participants were presented with incongruent audio-visual stimuli, the perceived duration of auditory events could be shortened or lengthened by the presence of conflicting visual information; however, the perceived duration of visual events was seldom distorted by the presence of auditory information and was never perceived shorter than their actual durations.These results support the existence of multisensory interactions in the perception of duration and, importantly, suggest that vision can modify auditory temporal perception in a pure timing task. Insofar as distortions in subjective duration can neither be accounted for by the unpredictability of an auditory, visual or auditory-visual event, we propose that it is the intrinsic features of the stimulus that critically affect subjective time distortions.

  37. Katharina von Kriegstein, Ozgür Dogan, Martina Grüter, Anne-Lise Giraud, Christian A Kell, Thomas Grüter, Andreas Kleinschmidt, and Stefan J Kiebel. Simulation of talking faces in the human brain improves auditory speech recognition.. Proc Natl Acad Sci U S A, 105(18):6747--6752, May 2008. [WWW] [PDF]
    Abstract: Human face-to-face communication is essentially audiovisual. Typically, people talk to us face-to-face, providing concurrent auditory and visual input. Understanding someone is easier when there is visual input, because visual cues like mouth and tongue movements provide complementary information about speech content. Here, we hypothesized that, even in the absence of visual input, the brain optimizes both auditory-only speech and speaker recognition by harvesting speaker-specific predictions and constraints from distinct visual face-processing areas. To test this hypothesis, we performed behavioral and neuroimaging experiments in two groups: subjects with a face recognition deficit (prosopagnosia) and matched controls. The results show that observing a specific person talking for 2 min improves subsequent auditory-only speech and speaker recognition for this person. In both prosopagnosics and controls, behavioral improvement in auditory-only speech recognition was based on an area typically involved in face-movement processing. Improvement in speaker recognition was only present in controls and was based on an area involved in face-identity processing. These findings challenge current unisensory models of speech processing, because they show that, in auditory-only speech, the brain exploits previously encoded audiovisual correlations to optimize communication. We suggest that this optimization is based on speaker-specific audiovisual internal models, which are used to simulate a talking face.

  1. Jim Holt. Numbers Guy. Are our brains wired for math?, 2008. [PDF] [bibtex-entry]



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