Publications of year 2012

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Publications of year 2012

Elodie Cauvet. Traitement des Structures Syntaxiques dans le Langage et dans la Musique. PhD Thesis, Université Paris 6, 2012. [WWW] [PDF] [bibtex-entry]

Baptiste Gauthier. Les fluctuations periodiques de l'activite neuronale, substrat commun de l'organisation temporelle de la perception sensorielle et de la perception de la durée. PhD Thesis, Universite Paris VI, 2012. [bibtex-entry]

Stanislas Dehaene. Cuando el reciclaje neuronal prolonga la hominizacion. In Sebastian Lapina and Mariano Sigman, editors,La pizarra de Babel, pages 91--105. Libros del Zorzal, 2012. [PDF] [bibtex-entry]

Articles in journals

Stanislas Dehaene and Mariano Sigman. From a single decision to a multi-step algorithm. Curr Opin Neurobiol, 22:1--9, June 2012. [WWW] [PDF]

Abstract:

Humans can perform sequential and recursive computations, as when calculating 23x74. However, this comes at a cost: flexible computations are slow and effortful. We argue that this competence involves serial chains of successive decisions, each based on the accumulation of evidence up to a threshold and forwarding the result to the subsequent step. Such serial 'programs' require a specific neurobiological architecture, approximating the operation of a slow serial Turing machine. We review recent progress in understanding how the brain implements such multi-step decisions and briefly examine how they might be realized in models of primate cortex.

Stanislas Dehaene. The Eternal Silence of Neuronal Spaces. Science, 336:1507--8, 2012. [PDF] [bibtex-entry]

Stéphane Deparis, Vincent Mousseau, Meltem Öztürk, Christophe Pallier, and Caroline Huron. When conflict induces the expression of incomplete preferences. European Journal of Operational Research, 221:593--602, 2012. [PDF] [bibtex-entry]

Frédéric Faugeras, Benjamin Rohaut, Nicolas Weiss, Tristan Bekinschtein, Damien Galanaud, Louis Puybasset, Francis Bolgert, Claire Sergent, Laurent Cohen, Stanislas Dehaene, and Lionel Naccache. Event related potentials elicited by violations of auditory regularities in patients with impaired consciousness. Neuropsychologia, 50(3):403--418, February 2012. [WWW] [PDF]

Abstract:

Improving our ability to detect conscious processing in non communicating patients remains a major goal of clinical cognitive neurosciences. In this perspective, several functional brain imaging tools are currently under development. Bedside cognitive event-related potentials (ERPs) derived from the EEG signal are a good candidate to explore consciousness in these patients because: (1) they have an optimal time resolution within the millisecond range able to monitor the stream of consciousness, (2) they are fully non-invasive and relatively cheap, (3) they can be recorded continuously on dedicated individual systems to monitor consciousness and to communicate with patients, (4) and they can be used to enrich patients' autonomy through brain-computer interfaces. We recently designed an original auditory rule extraction ERP test that evaluates cerebral responses to violations of temporal regularities that are either local in time or global across several seconds. Local violations led to an early response in auditory cortex, independent of attention or the presence of a concurrent visual task, while global violations led to a late and spatially distributed response that was only present when subjects were attentive and aware of the violations. In the present work, we report the results of this test in 65 successive recordings obtained at bedside from 49 non-communicating patients affected with various acute or chronic neurological disorders. At the individual level, we confirm the high specificity of the 'global effect': only conscious patients presented this proposed neural signature of conscious processing. Here, we also describe in details the respective neural responses elicited by violations of local and global auditory regularities, and we report two additional ERP effects related to stimuli expectancy and to task learning, and we discuss their relations to consciousness.

Edith Le Floch, Vincent Guillemot, Vincent Frouin, Philippe Pinel, Christophe Lalanne, Laura Trinchera, Arthur Tenenhaus, Antonio Moreno, Monica Zilbovicius, Thomas Bourgeron, Stanislas Dehaene, Bertrand Thirion, Jean-Baptiste Poline, and Edouard Duchesnay. Significant correlation between a set of genetic polymorphisms and a functional brain network revealed by feature selection and sparse Partial Least Squares. NeuroImage, 63:11--24, 2012. [PDF] [bibtex-entry]

Baptiste Gauthier, Evelyn Eger, Guido Hesselmann, Anne-Lise Giraud, and Andreas Kleinschmidt. Temporal tuning properties along the human ventral visual stream. J Neurosci, 32(41):14433--14441, October 2012. [WWW] [PDF]

Abstract:

Both our environment and our behavior contain many spatiotemporal regularities. Preferential and differential tuning of neural populations to these regularities can be demonstrated by assessing rate dependence of neural responses evoked during continuous periodic stimulation. Here, we used functional magnetic resonance imaging to measure regional variations of temporal sensitivity along the human ventral visual stream. By alternating one face and one house stimulus, we combined sufficient low-level signal modulation with changes in semantic meaning and could therefore drive all tiers of visual cortex strongly enough to assess rate dependence. We found several dissociations between early visual cortex and middle- and higher-tier regions. First, there was a progressive slowing down of stimulation rates yielding peak responses along the ventral visual stream. This finding shows the width of temporal integration windows to increase at higher hierarchical levels. Next, for fixed rates, early but not higher visual cortex responses additionally depended on the length of stimulus exposure, which may indicate increased persistence of responses to short stimuli at higher hierarchical levels. Finally, attention, which was recruited by an incidental task, interacted with stimulation rate and shifted tuning peaks toward lower frequencies. Together, these findings quantify neural response properties that are likely to be operational during natural vision and that provide putative neurofunctional substrates of mechanisms that are relevant in several psychophysical phenomena as masking and the attentional blink. Moreover, they illustrate temporal constraints for translating the deployment of attention into enhanced neural responses and thereby account for lower limits of attentional dwell time.

David Germanaud, Julien Lefèvre, Roberto Toro, Clara Fischer, Jessica Dubois, Lucie Hertz-Pannier, and Jean-Francois Mangin. Larger is twistier: spectral analysis of gyrification (SPANGY) applied to adult brain size polymorphism.. Neuroimage, 63(3):1257--1272, November 2012. [WWW] [PDF]

Abstract:

The description of cortical folding pattern (CFP) is challenging because of geometric complexity and inter-subject variability. On a cortical surface mesh, curvature estimation provides a good scalar proxy of CFP. The oscillations of this function can be studied using a Fourier-like analysis to produce a power spectrum representative of the spatial frequency composition of CFP. First, we introduce an original method for the SPectral ANalysis of GYrication (Spangy), which performs a spectral decomposition of the mean curvature of the grey/white interface mesh based on the Laplace-Beltrami operator eigenfunctions. Spangy produces an ordered 7 bands power spectrum of curvature (B0-B6) and provides an anatomically relevant segmentation of CFP based on local spectral composition. A spatial frequency being associated with each eigenfunction, the bandwidth design assumes frequency doubling between consecutive spectral bands. Next, we observed that the last 3 spectral bands (B4, 5 and 6) accounted for 93\% of the analyzed spectral power and were associated with fold-related variations of curvature, whereas the lower frequency bands were related to global brain shape. The spectral segmentation of CFP revealed 1st, 2nd and 3rd order elements associated with B4, B5 and B6 respectively. These elements could be related to developmentally-defined primary, secondary and tertiary folds. Finally, we used allometric scaling of frequency bands power and segmentation to analyze the relationship between the spectral composition of CFP and brain size in a large adult dataset. Total folding power followed a positive allometric scaling which did not divide up proportionally between the bands: B4 contribution was constant, B5 increased like total folding power and B6 much faster. Besides, apparition of new elements of pattern with increasing size only concerned the 3rd order. Hence, we demonstrate that large brains are twistier than smaller ones because of an increased number of high spatial frequency folds, ramifications and kinks that accommodate the allometric increase of cortical surface.

G. Hesselmann, L. Naccache, L. Cohen, and S Dehaene. Splitting of the P3 component during dual-task processing in a patient with posterior callosal section. Cortex, Available online 27 March 2012, 2012. [WWW] [PDF] [bibtex-entry]

Katarzyna Jednorog, Irene Altarelli, Karla Monzalvo, Joel Fluss, Jessica Dubois, Catherine Billard, Ghislaine Dehaene-Lambertz, and Franck Ramus. The Influence of Socioeconomic Status on Children?s Brain Structure. PLoS One, August 3, 2012, 2012. [PDF] [bibtex-entry]

Olivier Joly, Christophe Pallier, Franck Ramus, Daniel Pressnitzer, Wim Vanduffel, and and Guy A. Orban. Processing of vocalizations in humans and monkeys: A comparative fMRI study. Neuroimage, 62:1376--89, 2012. [PDF] [bibtex-entry]

Olivier Joly, Christophe Pallier, Franck Ramus, Daniel Pressnitzer, Wim Vanduffel, and Guy A. Orban. Processing of vocalizations in humans and monkeys: a comparative fMRI study. Neuroimage, 62(3):1376--1389, September 2012. [WWW] [PDF]

Abstract:

Humans and many other animals use acoustical signals to mediate social interactions with conspecifics. The evolution of sound-based communication is still poorly understood and its neural correlates have only recently begun to be investigated. In the present study, we applied functional MRI to humans and macaque monkeys listening to identical stimuli in order to compare the cortical networks involved in the processing of vocalizations. At the first stages of auditory processing, both species showed similar fMRI activity maps within and around the lateral sulcus (the Sylvian fissure in humans). Monkeys showed remarkably similar responses to monkey calls and to human vocal sounds (speech or otherwise), mainly in the lateral sulcus and the adjacent superior temporal gyrus (STG). In contrast, a preference for human vocalizations and especially for speech was observed in the human STG and superior temporal sulcus (STS). The STS and Broca's region were especially responsive to intelligible utterances. The evolution of the language faculty in humans appears to have recruited most of the STS. It may be that in monkeys, a much simpler repertoire of vocalizations requires less involvement of this temporal territory.

Andreas Kleinschmidt, Philipp Sterzer, and Geraint Rees. Variability of perceptual multistability: from brain state to individual trait.. Philos Trans R Soc Lond B Biol Sci, 367(1591):988--1000, April 2012. [WWW] [PDF]

Abstract:

Few phenomena are as suitable as perceptual multistability to demonstrate that the brain constructively interprets sensory input. Several studies have outlined the neural circuitry involved in generating perceptual inference but only more recently has the individual variability of this inferential process been appreciated. Studies of the interaction of evoked and ongoing neural activity show that inference itself is not merely a stimulus-triggered process but is related to the context of the current brain state into which the processing of external stimulation is embedded. As brain states fluctuate, so does perception of a given sensory input. In multistability, perceptual fluctuation rates are consistent for a given individual but vary considerably between individuals. There has been some evidence for a genetic basis for these individual differences and recent morphometric studies of parietal lobe regions have identified neuroanatomical substrates for individual variability in spontaneous switching behaviour. Moreover, disrupting the function of these latter regions by transcranial magnetic stimulation yields systematic interference effects on switching behaviour, further arguing for a causal role of these regions in perceptual inference. Together, these studies have advanced our understanding of the biological mechanisms by which the brain constructs the contents of consciousness from sensory input.

Anne Kösem and Virginie van Wassenhove. Temporal structure in audiovisual sensory selection.. PLoS One, 7(7):e40936, 2012. [WWW] [PDF]

Abstract:

In natural environments, sensory information is embedded in temporally contiguous streams of events. This is typically the case when seeing and listening to a speaker or when engaged in scene analysis. In such contexts, two mechanisms are needed to single out and build a reliable representation of an event (or object): the temporal parsing of information and the selection of relevant information in the stream. It has previously been shown that rhythmic events naturally build temporal expectations that improve sensory processing at predictable points in time. Here, we asked to which extent temporal regularities can improve the detection and identification of events across sensory modalities. To do so, we used a dynamic visual conjunction search task accompanied by auditory cues synchronized or not with the color change of the target (horizontal or vertical bar). Sounds synchronized with the visual target improved search efficiency for temporal rates below 1.4 Hz but did not affect efficiency above that stimulation rate. Desynchronized auditory cues consistently impaired visual search below 3.3 Hz. Our results are interpreted in the context of the Dynamic Attending Theory: specifically, we suggest that a cognitive operation structures events in time irrespective of the sensory modality of input. Our results further support and specify recent neurophysiological findings by showing strong temporal selectivity for audiovisual integration in the auditory-driven improvement of visual search efficiency.

Sébastien Marti, Mariano Sigman, and Stanislas Dehaene. A shared cortical bottleneck underlying Attentional Blink and Psychological Refractory Period.. Neuroimage, 59(3):2883--98, October 2012. [WWW] [PDF]

Abstract:

Doing two things at once is difficult. When two tasks have to be performed within a short interval, the second is sharply delayed, an effect called the Psychological Refractory Period (PRP). Similarly, when two successive visual targets are briefly flashed, people may fail to detect the second target (Attentional Blink or AB). Although AB and PRP are typically studied in very different paradigms, a recent detailed neuromimetic model suggests that both might arise from the same serial stage during which stimuli gain access to consciousness and, as a result, can be arbitrarily routed to any other appropriate processor. Here, in agreement with this model, we demonstrate that AB and PRP can be obtained on alternate trials of the same cross-modal paradigm and result from limitations in the same brain mechanisms. We asked participants to respond as fast as possible to an auditory target T1 and then to a visual target T2 embedded in a series of distractors, while brain activity was recorded with magneto-encephalography (MEG). For identical stimuli, we observed a mixture of blinked trials, where T2 was entirely missed, and PRP trials, where T2 processing was delayed. MEG recordings showed that PRP and blinked trials underwent identical sensory processing in visual occipito-temporal cortices, even including the non-conscious separation of targets from distractors. However, late activations in frontal cortex ({\textgreater}350ms), strongly influenced by the speed of task-1 execution, were delayed in PRP trials and absent in blinked trials. Our findings suggest that PRP and AB arise from similar cortical stages, can occur with the same exact stimuli, and are merely distinguished by trial-by-trial fluctuations in task processing.

Masaki Maruyama, Christophe Pallier, Antoinette Jobert, Mariano Sigman, and Stanislas Dehaene. The cortical representation of simple mathematical expressions.. Neuroimage, 61(4):1444--1460, July 2012. [WWW] [PDF]

Abstract:

Written mathematical notation conveys, in a compact visual form, the nested functional relations among abstract concepts such as operators, numbers or sets. Is the comprehension of mathematical expressions derived from the human capacity for processing the recursive structure of language? Or does algebraic processing rely only on a language-independent network, jointly involving the visual system for parsing the string of mathematical symbols and the intraparietal system for representing numbers and operators? We tested these competing hypotheses by scanning mathematically trained adults while they viewed simple strings ranging from randomly arranged characters to mathematical expressions with up to three levels of nested parentheses. Syntactic effects were observed in behavior and in brain activation measured with functional magnetic resonance imaging (fMRI) and magneto-encephalography (MEG). Bilateral occipito-temporal cortices and right parietal and precentral cortices appeared as the primary nodes for mathematical syntax. MEG estimated that a mathematical expression could be parsed by posterior visual regions in less than 180ms. Nevertheless, a small increase in activation with increasing expression complexity was observed in linguistic regions of interest, including the left inferior frontal gyrus and the posterior superior temporal sulcus. We suggest that mathematical syntax, although arising historically from language competence, becomes "compiled" into visuo-spatial areas in well-trained mathematics students.

Karla Monzalvo, Joel Fluss, Catherine Billard, Stanislas Dehaene, and Ghislaine Dehaene-Lambertz. Cortical networks for vision and language in dyslexic and normal children of variable socio-economic status.. Neuroimage, 61(1):258--274, February 2012. [WWW] [PDF]

Abstract:

In dyslexia, anomalous activations have been described in both left temporo-parietal language cortices and in left ventral visual occipito-temporal cortex. However, the reproducibility, task-dependency, and presence of these brain anomalies in childhood rather than adulthood remain debated. We probed the large-scale organization of ventral visual and spoken language areas in dyslexic children using minimal target-detection tasks that were performed equally well by all groups. In 23 normal and 23 dyslexic 10-year-old children from two different socio-economic status (SES) backgrounds, we compared fMRI activity to visually presented houses, faces, and written strings, and to spoken sentences in the native or in a foreign language. Our results confirm a disorganization of both ventral visual and spoken language areas in dyslexic children. Visually, dyslexic children showed a normal lateral-to-medial mosaic of preferences, as well as normal responses to houses and checkerboards, but a reduced activation to words in the visual word form area (VWFA) and to faces in the right fusiform face area (FFA). Auditorily, dyslexic children exhibited reduced responses to speech in posterior temporal cortex, left insula and supplementary motor area, as well as reduced responses to maternal language in subparts of the planum temporale, left basal language area and VWFA. By correlating these two findings, we identify spoken-language predictors of VWFA activation to written words, which differ for dyslexic and normal readers. Similarities in fMRI deficits in both SES groups emphasize the existence of a core set of brain activation anomalies in dyslexia, regardless of culture, language and SES, without however resolving whether these anomalies are a cause or a consequence of impaired reading.

Kimihiro Nakamura, Wen-Jui Kuo, Felipe Pegado, Laurent Cohen, Ovid J. L. Tzeng, and Stanislas Dehaene. Universal brain systems for recognizing word shapes and handwriting gestures during reading.. Proc Natl Acad Sci U S A, 109(50):20762--20767, December 2012. [WWW] [PDF]

Abstract:

Do the neural circuits for reading vary across culture? Reading of visually complex writing systems such as Chinese has been proposed to rely on areas outside the classical left-hemisphere network for alphabetic reading. Here, however, we show that, once potential confounds in cross-cultural comparisons are controlled for by presenting handwritten stimuli to both Chinese and French readers, the underlying network for visual word recognition may be more universal than previously suspected. Using functional magnetic resonance imaging in a semantic task with words written in cursive font, we demonstrate that two universal circuits, a shape recognition system (reading by eye) and a gesture recognition system (reading by hand), are similarly activated and show identical patterns of activation and repetition priming in the two language groups. These activations cover most of the brain regions previously associated with culture-specific tuning. Our results point to an extended reading network that invariably comprises the occipitotemporal visual word-form system, which is sensitive to well-formed static letter strings, and a distinct left premotor region, Exner's area, which is sensitive to the forward or backward direction with which cursive letters are dynamically presented. These findings suggest that cultural effects in reading merely modulate a fixed set of invariant macroscopic brain circuits, depending on surface features of orthographies.

Marcela Pena, Janet F. Werker, and Ghislaine Dehaene-Lambertz. Earlier Speech Exposure Does Not Accelerate Speech Acquisition. Journal of Neuroscience, 32:11159--63, 2012. [PDF] [bibtex-entry]

Philippe Pinel, Fabien Fauchereau, Antonio Moreno, Alexis Barbot, Mark Lathrop, Diana Zelenika, Denis Le Bihan, Jean-Baptiste Poline, Thomas Bourgeron, and Stanislas Dehaene. Genetic Variants of FOXP2 and KIAA0319/TTRAP/THEM2 Locus Are Associated with Altered Brain Activation in Distinct Language-Related Regions.. J Neurosci, 32(3):817--825, January 2012. [WWW] [PDF]

Abstract:

Recent advances have been made in the genetics of two human communication skills: speaking and reading. Mutations of the FOXP2 gene cause a severe form of language impairment and orofacial dyspraxia, while single-nucleotide polymorphisms (SNPs) located within a KIAA0319/TTRAP/THEM2 gene cluster and affecting the KIAA0319 gene expression are associated with reading disability. Neuroimaging studies of clinical populations point to partially distinct cerebral bases for language and reading impairments. However, alteration of FOXP2 and KIAA0319/TTRAP/THEM2 polymorphisms on typically developed language networks has never been explored. Here, we genotyped and scanned 94 healthy subjects using fMRI during a reading task. We studied the correlation of genetic polymorphisms with interindividual variability in brain activation and functional asymmetry in frontal and temporal cortices. In FOXP2, SNPs rs6980093 and rs7799109 were associated with variations of activation in the left frontal cortex. In the KIAA0319/TTRAP/THEM2 locus, rs17243157 was associated with asymmetry in functional activation of the superior temporal sulcus (STS). Interestingly, healthy subjects bearing the KIAA0319/TTRAP/THEM2 variants previously identified as enhancing the risk of dyslexia showed a reduced left-hemispheric asymmetry of the STS. Our results confirm that both FOXP2 and KIAA0319/TTRAP/THEM2 genes play an important role in human language development, but probably through different cerebral pathways. The observed cortical effects mirror previous fMRI results in developmental language and reading disorders, and suggest that a continuum may exist between these pathologies and normal interindividual variability.

Volker Ressel, Christophe Pallier, Noelia Ventura-Campos, Begonia Diaz, Abeda Roessler, César Avila, and Nuria Sebastian-Gallés. An Effect of Bilingualism on the Auditory Cortex. Journal of Neuroscience, 32(47):16597--601, 2012. [WWW] [bibtex-entry]

Elisa Schneider, Masaki Maruyama, Stanislas Dehaene, and Mariano Sigman. Eye gaze reveals a fast, parallel extraction of the syntax of arithmetic formulas.. Cognition, 125(3):475--490, December 2012. [WWW] [PDF]

Abstract:

Mathematics shares with language an essential reliance on the human capacity for recursion, permitting the generation of an infinite range of embedded expressions from a finite set of symbols. We studied the role of syntax in arithmetic thinking, a neglected component of numerical cognition, by examining eye movement sequences during the calculation of arithmetic expressions. Specifically, we investigated whether, similar to language, an expression has to be scanned sequentially while the nested syntactic structure is being computed or, alternatively, whether this structure can be extracted quickly and in parallel. Our data provide evidence for the latter: fixations sequences were stereotypically organized in clusters that reflected a fast identification of syntactic embeddings. A syntactically relevant pattern of eye movement was observed even when syntax was defined by implicit procedural rules (precedence of multiplication over addition) rather than explicit parentheses. While the total number of fixations was determined by syntax, the duration of each fixation varied with the complexity of the arithmetic operation at each step. These findings provide strong evidence for a syntactic organization for arithmetic thinking, paving the way for further comparative analysis of differences and coincidences in the instantiation of recursion in language and mathematics.

Michel Thiebaut de Schotten, Laurent Cohen, Eduardo Amemiya, Lucia W. Braga, and Stanislas Dehaene. Learning to Read Improves the Structure of the Arcuate Fasciculus. Cereb Cortex, December 2012. [WWW] [PDF]

Abstract:

The acquisition of literacy results from an effortful learning process that leads to functional changes in several cortical regions. We explored whether learning to read also leads to anatomical changes within the left intrahemispheric white matter pathways that interconnect these regions. Using diffusion tensor imaging tractography, we compared illiterates with ex-illiterates who learned to read during adulthood and literates who learned to read during their childhood. Literacy related to an increase in fractional anisotropy and a decrease in perpendicular diffusivity in the temporo-parietal portion of the left arcuate fasciculus. The microstructure within this pathway correlated with the reading performance and the degree of functional activation within 2 dominant brain regions involved in reading: The Visual Word Form Area in response to letter strings, and the posterior superior temporal cortex in response to spoken language. Thus, the acquisition of literacy is associated with a reinforcement of left temporo-parietal connections whose microstructure predicts overall reading performance and the functional specialization of the Visual Word Form Area. This anatomical magnetic resonance imaging marker may be useful to predict developmental reading disorders.

Aaron Schurger, Jacobo Sitt, and Stanislas Dehaene. An accumulator model for spontaneous neural activity prior to self-initiated movement. PNAS, August 6, 2012, 2012. [PDF] [bibtex-entry]

Yannick Schwartz, Gaël Varoquaux, Christophe Pallier, Philippe Pinel, Jean-Baptiste Poline, and Bertrand Thirion. Improving accuracy and power with transfer learning using a meta-analytic database.. Med Image Comput Comput Assist Interv, 15(Pt 3):248--255, 2012.

Abstract:

Typical cohorts in brain imaging studies are not large enough for systematic testing of all the information contained in the images. To build testable working hypotheses, investigators thus rely on analysis of previous work, sometimes formalized in a so-called meta-analysis. In brain imaging, this approach underlies the specification of regions of interest (ROIs) that are usually selected on the basis of the coordinates of previously detected effects. In this paper, we propose to use a database of images, rather than coordinates, and frame the problem as transfer learning: learning a discriminant model on a reference task to apply it to a different but related new task. To facilitate statistical analysis of small cohorts, we use a sparse discriminant model that selects predictive voxels on the reference task and thus provides a principled procedure to define ROIs. The benefits of our approach are twofold. First it uses the reference database for prediction, i.e., to provide potential biomarkers in a clinical setting. Second it increases statistical power on the new task. We demonstrate on a set of 18 pairs of functional MRI experimental conditions that our approach gives good prediction. In addition, on a specific transfer situation involving different scanners at different locations, we show that voxel selection based on transfer learning leads to higher detection power on small cohorts.

N Sebastian-Galles, C. Soriano-Mas, C. Baus, B. Diaz, V. Ressel, Christophe Pallier, A. Costa, and J Pujol. Neuroanatomical markers of individual differences in native and non-native vowel perception. Journal of Neurolinguistics, 25:150--62, 2012. [PDF] [bibtex-entry]

Ella Striem-Amit, Laurent Cohen, Stanislas Dehaene, and Amir Amedi. Reading with sounds: sensory substitution selectively activates the visual word form area in the blind. Neuron, 76(3):640--652, November 2012. [WWW] [PDF]

Abstract:

Using a visual-to-auditory sensory-substitution algorithm, congenitally fully blind adults were taught to read and recognize complex images using "soundscapes"–sounds topographically representing images. fMRI was used to examine key questions regarding the visual word form area (VWFA): its selectivity for letters over other visual categories without visual experience, its feature tolerance for reading in a novel sensory modality, and its plasticity for scripts learned in adulthood. The blind activated the VWFA specifically and selectively during the processing of letter soundscapes relative to both textures and visually complex object categories and relative to mental imagery and semantic-content controls. Further, VWFA recruitment for reading soundscapes emerged after 2 hr of training in a blind adult on a novel script. Therefore, the VWFA shows category selectivity regardless of input sensory modality, visual experience, and long-term familiarity or expertise with the script. The VWFA may perform a flexible task-specific rather than sensory-specific computation, possibly linking letter shapes to phonology.

Marcin Szwed, Paulo Ventura, Luis Querido, Laurent Cohen, and Stanislas Dehaene. Reading acquisition enhances an early visual process of contour integration.. Dev Sci, 15(1):139--149, January 2012. [WWW] [PDF]

Abstract:

The acquisition of reading has an extensive impact on the developing brain and leads to enhanced abilities in phonological processing and visual letter perception. Could this expertise also extend to early visual abilities outside the reading domain? Here we studied the performance of illiterate, ex-illiterate and literate adults closely matched in age, socioeconomic and cultural characteristics, on a contour integration task known to depend on early visual processing. Stimuli consisted of a closed egg-shaped contour made of disconnected Gabor patches, within a background of randomly oriented Gabor stimuli. Subjects had to decide whether the egg was pointing left or right. Difficulty was varied by jittering the orientation of the Gabor patches forming the contour. Contour integration performance was lower in illiterates than in both ex-illiterate and literate controls. We argue that this difference in contour perception must reflect a genuine difference in visual function. According to this view, the intensive perceptual training that accompanies reading acquisition also improves early visual abilities, suggesting that the impact of literacy on the visual system is more widespread than originally proposed.

Marcin Szwed, Fabien Vinckier, Laurent Cohen, and Stanislas Dehaene. Towards a universal neurobiological architecture for learning to read. Behavioral and Brain Sciences, 2012. [PDF] [bibtex-entry]

Laurianne Vagharchakian, Ghislaine Dehaene-Lambertz, Christophe Pallier, and Stanislas Dehaene. A temporal bottleneck in the language comprehension network.. J Neurosci, 32(26):9089--9102, June 2012. [WWW] [PDF]

Abstract:

Humans can understand spoken or written sentences presented at extremely fast rates of ?400 wpm, far exceeding the normal speech rate (?150 wpm). How does the brain cope with speeded language? And what processing bottlenecks eventually make language incomprehensible above a certain presentation rate? We used time-resolved fMRI to probe the brain responses to spoken and written sentences presented at five compression rates, ranging from intelligible (60-100\% of the natural duration) to challenging (40\%) and unintelligible (20\%). The results show that cortical areas differ sharply in their activation speed and amplitude. In modality-specific sensory areas, activation varies linearly with stimulus duration. However, a large modality-independent left-hemispheric language network, including the inferior frontal gyrus (pars orbitalis and triangularis) and the superior temporal sulcus, shows a remarkably time-invariant response, followed by a sudden collapse for unintelligible stimuli. Finally, linear and nonlinear responses, reflecting a greater effort as compression increases, are seen at various prefrontal and parietal sites. We show that these profiles fit with a simple model according to which the higher stages of language processing operate at a fixed speed and thus impose a temporal bottleneck on sentence comprehension. At presentation rates faster than this internal processing speed, incoming words must be buffered, and intelligibility vanishes when buffer storage and retrieval operations are saturated. Based on their temporal and amplitude profiles, buffer regions can be identified with the left inferior frontal/anterior insula, precentral cortex, and mesial frontal cortex.

Virginie van Wassenhove. From the dynamic structure of the brain to the emergence of time experiences. Kronoscope, 12(2):201--218, 2012. [PDF] [bibtex-entry]

Catherine Wacongne, Jean-Pierre Changeux, and Stanislas Dehaene. A neuronal model of predictive coding accounting for the mismatch negativity.. J Neurosci, 32(11):3665--3678, March 2012. [WWW] [PDF]

Abstract:

The mismatch negativity (MMN) is thought to index the activation of specialized neural networks for active prediction and deviance detection. However, a detailed neuronal model of the neurobiological mechanisms underlying the MMN is still lacking, and its computational foundations remain debated. We propose here a detailed neuronal model of auditory cortex, based on predictive coding, that accounts for the critical features of MMN. The model is entirely composed of spiking excitatory and inhibitory neurons interconnected in a layered cortical architecture with distinct input, predictive, and prediction error units. A spike-timing dependent learning rule, relying upon NMDA receptor synaptic transmission, allows the network to adjust its internal predictions and use a memory of the recent past inputs to anticipate on future stimuli based on transition statistics. We demonstrate that this simple architecture can account for the major empirical properties of the MMN. These include a frequency-dependent response to rare deviants, a response to unexpected repeats in alternating sequences (ABABAA?), a lack of consideration of the global sequence context, a response to sound omission, and a sensitivity of the MMN to NMDA receptor antagonists. Novel predictions are presented, and a new magnetoencephalography experiment in healthy human subjects is presented that validates our key hypothesis: the MMN results from active cortical prediction rather than passive synaptic habituation.

Valentin Wyart, Stanislas Dehaene, and Catherine Tallon-Baudry. Early Dissociation between Neural Signatures of Endogenous Spatial Attention and Perceptual Awareness during Visual Masking. Frontiers in Human Neuroscience, 6:article16, 2012. [PDF] [bibtex-entry]

Stanislas Dehaene and Felipe Pegado. O impacto da aprendizagem da leitura sobre o cérebro, April 2012. [PDF] [bibtex-entry]

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