Jean-Michel Hupé’s research while affiliated with Université Toulouse III - Paul Sabatier and other places

Avec Apocalypse cognitive , le sociologue Gérald Bronner entend traiter un problème grave : notre attention serait vampirisée par les moyens modernes de communication et d’échanges. Internet et les réseaux sociaux numériques, en particulier, auraient pris d’assaut notre « cerveau ancestral ». Cet univers numérique, fonctionnant selon lui à la façon d’un « marché libre » et « dérégulé », accaparerait des esprits rendus faibles par des contenus de qualité douteuse. G. Bronner entend démontrer en quoi l’activité en ligne révèle (sens premier de l’apocalypse du titre) les limites et faiblesses de notre fonctionnement cérébral et menace la démocratie et la civilisation. L’auteur a recours au registre alarmiste de l’« apocalypse » et distille, au gré d’une démonstration qui se veut rigoureuse, des recommandations pour sortir de l’ornière. Apocalypse cognitive ne s’adresse pas spécialement à un lectorat académique. Cet essai relève plutôt de l’intervention et de l’alerte. Pourtant, il prétend s’appuyer sur des connaissances scientifiques et son auteur ne cesse de faire appel à l’autorité des neurosciences pour accréditer des vues souvent très personnelles. Et c’est en cela que le bât blesse. G. Bronner enchaîne les affirmations péremptoires sur la « nature humaine », fonde ses interprétations sur des données biaisées, et déforme les résultats des neurosciences pour les ajuster à des opinions très tranchées. Nous documentons dans cette lecture critique en quoi cet usage de l’autorité scientifique est questionnable, sans épuiser l’inventaire des mésinterprétations et erreurs contenues dans le livre (une annexe, déposée sur l’archive ouverte HAL, en liste l’essentiel). Fourre-tout qui ne résiste pas à l’épreuve de l’argumentation scientifique, Apocalypse cognitive offre donc non pas un diagnostic sérieux mais une incantation moraliste, mobilisable dans le champ politique.

We tested whether the acquisition of grapheme-color synesthesia during childhood is related to difficulties in written language learning by measuring whether it is more frequent in 79 children receiving speech and language therapy for such difficulties than in the general population of children (1.3%). By using criteria as similar as possible to those used in the reference study (Simner et al., 2009), we did not identify any synesthete (Bayesian 95% credible interval [0, 4.5]% for a flat prior). The odds of the null model (no difference between 0/79 and 1.3%) over alternative models is 28 (Bayes Factor). A higher prevalence of grapheme-color synesthetes among children with learning difficulties is therefore very unlikely, questioning the hypothesis of a link between synesthesia and difficulties in language acquisition. We also describe the difficulty of diagnosing synesthesia in children and discuss the need for new approaches to do so.

Nabokov belongs to a small “family” of great artists also known as synesthetes, suggesting a link between synesthesia and creativity. Moreover, Nabokov’s report of precise synesthetic associations between letters and colors already in his early childhood suggests that synesthesia is a gift, possibly innate. Could we suppose that the brain of Nabokov was special because of synesthesia? Could synesthesia relate to his metaphoric creativity, his strong visual mental imagery and memory or even some aspects of his personality? Here we show that the synesthetic experiences described by Nabokov are similar to those of synesthetes studied by scientists for the last twenty years. We review what cognitive neuroscience has learnt so far about the possible mechanisms of synesthesia and whether synesthetes display any special characteristics beyond synesthesia. We show that little is known and that there is little support to naturalize Nabokov’s creative process on the basis of him having synesthesia.

Grapheme–colour synaesthesia is a subjective phenomenon related to perception and imagination, in which some people involuntarily but systematically associate specific, idiosyncratic colours to achromatic letters or digits. Its investigation is relevant to unravel the neural correlates of colour perception in isolation from low‐level neural processing of spectral components, as well as the neural correlates of imagination by being able to reliably trigger imaginary colour experiences. However, functional MRI studies using univariate analyses failed to provide univocal evidence of the activation of the “colour network” by synaesthesia. Applying multivariate (multivoxel) pattern analysis (MVPA) on 20 synaesthetes and 20 control participants, we tested whether the neural processing of real colours (concentric rings) and synaesthetic colours (black graphemes) shared patterns of activations. Region of interest analyses in retinotopically and anatomically defined visual areas revealed neither evidence of shared circuits for real and synaesthetic colour processing, nor processing difference between synaesthetes and controls. We also found no correlation with individual experiences, characterised by measuring the strength of synaesthetic associations. The whole brain searchlight analysis led to similar results. We conclude that revealing the neural coding of the synaesthetic experience of colours is a hard task which requires the improvement of our current methodology: for example involving more individuals and achieving higher MR signal to noise ratio and spatial resolution. So far, we have not found any evidence of the involvement of the cortical colour network in the subjective experience of synaesthetic colours.

The aim of the present study was to uncover a possible common neural organizing principle in spoken and written communication, through the coupling of perceptual and motor representations. In order to identify possible shared neural substrates for processing the basic units of spoken and written language, a sparse sampling fMRI acquisition protocol was performed on the same subjects in two experimental sessions with similar sets of letters being read and written and of phonemes being heard and orally produced. We found evidence of common premotor regions activated in spoken and written language, both in perception and in production. The location of those brain regions was confined to the left lateral and medial frontal cortices, at locations corresponding to the premotor cortex, inferior frontal cortex and supplementary motor area. Interestingly, the speaking and writing tasks also appeared to be controlled by largely overlapping networks, possibly indicating some domain general cognitive processing. Finally, the spatial distribution of individual activation peaks further showed more dorsal and more left-lateralized premotor activations in written than in spoken language.

Grapheme-colour synaesthesia is a subjective phenomenon related to perception and imagination, in which some people involuntarily but systematically associate specific, idiosyncratic colours to achromatic letters or digits. Its investigation is relevant to unravel the neural correlates of colour perception in isolation from low-level neural processing of spectral components, as well as the neural correlates of imagination by being able to reliably trigger imaginary colour experiences. However, functional MRI studies using univariate analyses failed to provide univocal evidence of the activation of the ‘colour network’ by synaesthesia. Applying Multivariate (multivoxel) Pattern Analysis (MVPA) on 20 synaesthetes and 20 control participants, we tested whether the neural processing of real colours (concentric rings) and synaesthetic colours (black graphemes) shared patterns of activations. Region of interest analyses in retinotopically and anatomically defined visual regions revealed neither evidence of shared circuits for real and synaesthetic colour processing, nor processing difference between synaesthetes and controls. We also found no correlation with individual experiences, characterised by measuring the strength of synaesthetic associations. The whole brain, searchlight, analysis led to similar results. We conclude that identifying the neural correlates of the synaesthetic experience of colours may still be beyond the reach of present technology and data analysis techniques.

Perception is sometimes bistable, switching between two possible interpretations. Levelt developed several propositions to explain bistable perception in binocular rivalry, based on a model of competing neural populations connected through reciprocal inhibition. Here we test Levelt's laws with bistable plaid motion. Plaids are typically tristable, either a coherent pattern, transparent with one component in front, or transparent with the opposite depth order. In Experiment 1, we use a large angle between component directions to prevent plaid coherence, limiting the ambiguity to alternations of grating depth order. Similar to increasing contrast in binocular rivalry, increasing component speed led to higher switch rates (analogous to Levelt's fourth proposition). In Experiment 2, we used occlusion cues to prevent one depth order and limit bistability to one transparent depth order alternating with coherence. Increasing grating speed shortened coherent motion periods but left transparent periods largely unchanged (analogous to Levelt's second proposition). Switch dynamics showed no correlation between the experiments. These data suggest that plaid component speed acts like contrast in binocular rivalry to vary switch dynamics through a mutual inhibition model. The lack of correlation between both experiments suggests reciprocal inhibition mediates bistability between a variety of neural populations across the visual system.

Several publications have reported structural changes in the brain of synesthetes compared to controls, either local differences or differences in connectivity. In the present study, we pursued this quest for structural brain differences that might support the subjective experience of synesthesia. In particular, for the first time in this field, we investigated brain folding in comparing 45 sulcal shapes in each hemisphere of control and grapheme-color synesthete populations. To overcome flaws relative to data interpretation based only on p-values, common in the synesthesia literature, we report confidence intervals of effect sizes. Moreover, our statistical maps are displayed without introducing the classical, but misleading, p-value level threshold. We adopt such a methodological procedure to facilitate appropriate data interpretation and promote the “New Statistics” approach. Based on structural or diffusion magnetic resonance imaging data, we did not find any strong cerebral anomaly, in sulci, tissue volume, tissue density or fiber organization that could support synesthetic color experience. Finally, by sharing our complete datasets, we strongly support the multi-center construction of a sufficient large dataset repository for detecting, if any, subtle brain differences that may help understanding how a subjective experience, such as synesthesia, is mentally constructed.

Individual demographic characteristics for the control population. * subject not used in sulci and surface-based morphometry analyzes. (PDF)

Surface based morphometry. Differences in 48 controls vs. 32 synesthetes for cortical thickness (mm), area (mm2) and volume (mm3) for left and right hemispheres (Cluster-forming threshold p<0.001). For each parameter, regions where differences were detected are indicated. No region survived the FWEc at the cluster level. (PDF)