Littérature scientifique sur le sujet « Tickertape »

It is unclear whether synesthesia is one condition or many, and this has implications for whether theories should postulate a single cause or multiple independent causes. Study 1 analyses data from a large sample of self-referred synesthetes ( N = 2,925), who answered a questionnaire about N = 164 potential types of synesthesia. Clustering and factor analysis methods identified around seven coherent groupings of synesthesia, as well as showing that some common types of synesthesia do not fall into any grouping at all (mirror-touch, hearing-motion, tickertape). There was a residual positive correlation between clusters (they tend to associate rather than compete). Moreover, we observed a “snowball effect” whereby the chances of having a given cluster of synesthesia go up in proportion to the number of other clusters a person has (again suggesting non-independence). Clusters tended to be distinguished by shared concurrent experiences rather than shared triggering stimuli (inducers). We speculate that modulatory feedback pathways from the concurrent to inducers may play a key role in the emergence of synesthesia. Study 2 assessed the external validity of these clusters by showing that they predict performance on other measures known to be linked to synesthesia.

AbstractReading acquisition is enabled by deep changes in the brain’s visual system and language areas, and in the links subtending their collaboration. Disruption of those plastic processes commonly results in developmental dyslexia. However, atypical development of reading mechanisms may occasionally result in ticker-tape synesthesia (TTS), a condition described by Francis Galton in 1883 wherein individuals “see mentally in print every word that is uttered (…) as from a long imaginary strip of paper”. While reading is the bottom–up translation of letters into speech, TTS may be viewed as its opposite, the top–down translation of speech into internally visualized letters. In a series of functional MRI experiments, we studied MK, a man with TTS. We showed that a set of left-hemispheric areas were more active in MK than in controls during the perception of normal than reversed speech, including frontoparietal areas involved in speech processing, and the Visual Word Form Area, an occipitotemporal region subtending orthography. Those areas were identical to those involved in reading, supporting the construal of TTS as upended reading. Using dynamic causal modeling, we further showed that, parallel to reading, TTS induced by spoken words and pseudowords relied on top–down flow of information along distinct lexical and phonological routes, involving the middle temporal and supramarginal gyri, respectively. Future studies of TTS should shed new light on the neurodevelopmental mechanisms of reading acquisition, their variability and their disorders.

Abstract Stimuli that have been generated by a person's own willed motor actions generally elicit a suppressed electrophysiological, as well as phenomenological, response than identical stimuli that have been externally generated. This well-studied phenomenon, known as sensory attenuation, has mostly been studied by comparing ERPs evoked by self-initiated and externally generated sounds. However, most studies have assumed a uniform action–effect contingency, in which a motor action leads to a resulting sensation 100% of the time. In this study, we investigated the effect of manipulating the probability of action–effect contingencies on the sensory attenuation effect. In Experiment 1, participants watched a moving, marked tickertape while EEG was recorded. In the full-contingency (FC) condition, participants chose whether to press a button by a certain mark on the tickertape. If a button press had not occurred by the mark, a sound would be played a second later 100% of the time. If the button was pressed before the mark, the sound was not played. In the no-contingency (NC) condition, participants observed the same tickertape; in contrast, however, if participants did not press the button by the mark, a sound would occur only 50% of the time (NC-inaction). Furthermore, in the NC condition, if a participant pressed the button before the mark, a sound would also play 50% of the time (NC-action). In Experiment 2, the design was identical, except that a willed action (as opposed to a willed inaction) triggered the sound in the FC condition. The results were consistent across the two experiments: Although there were no differences in N1 amplitude between conditions, the amplitude of the Tb and P2 components were smaller in the FC condition compared with the NC-inaction condition, and the amplitude of the P2 component was also smaller in the FC condition compared with the NC-action condition. The results suggest that the effect of contingency on electrophysiological indices of sensory attenuation may be indexed primarily by the Tb and P2 components, rather than the N1 component which is most commonly studied.

Les réseaux cérébraux impliqués dans le langage oral et le langage écrit sont connectés et interagissent lorsque nous utilisons l’un ou l’autre. Par exemple lorsque nous entendons du langage, nous accédons aux informations concernant l’orthographe de ce que nous entendons, et inversement lorsque nous lisons, nous accédons aux informations phonologiques du contenu. L’aire de la forme visuelle des mots, située dans le gyrus fusiforme gauche, joue un rôle important dans ces interactions. Cette aire est spécialisée dans la reconnaissance des lettres et des mots, et apparaît avec l’apprentissage de la lecture. La synesthésie est définie comme une « fusion des sens » : la perception dans une modalité sensorielle est accompagnée d’une perception surajoutée, dans une autre modalité sensorielle non sollicitée. Il existe une synesthésie mettant en relation les processus de langages oral et écrit, nommée la synesthésie des sous-titres (tickertape synesthesia, TTS), et dans laquelle la personne perçoit la forme orthographique de ce qu’elle entend. Notre hypothèse était que les régions responsables de la TTS étaient les régions péri-sylviennes impliquées dans le langage, et visuelles impliquées dans le traitement de l’orthographe. Nous avions également prédit que ce phénomène était lié à une activation inverse du réseau de lecture, sous-tendue par des influences descendantes des aires du langage vers les aires de la lecture trop importantes. Nous avons fait remplir un questionnaire aux personnes ayant cette synesthésie, qui nous a permis de mieux caractériser l’expérience subjective de la TTS, notamment les aspects visuo-spatiaux des sous-titres et le type de stimulus auditif ou la situation pouvant déclencher la TTS. Nous avons aussi montré qu’il existait des différences de performance lors de tests comportementaux. Les synesthètes étaient avantagés lors des tâches impliquant la mémoire de travail orthographique sur stimulation auditive seule, mais n’étaient pas gênés lors de tâche visuelle avec interférence par le biais d’une stimulation auditive concomitante. Nous avons identifié les réseaux neuronaux activés durant la TTS, d’abord chez un seul synesthète, puis nous avons répliqué ces résultats sur tout un groupe. Ces régions correspondent aux régions péri-sylviennes impliquées dans le langage et aux régions occipito-temporales ventrales impliquées dans le traitement orthographique. Les réseaux activés dans la TTS étaient superposables à ceux activés par la lecture. Ces résultats confirmaient donc nos hypothèses de départ. Nous avons également montré qu’il existait un excès de connectivité au repos chez les synesthètes, notamment entre les régions frontales et occipitales. Il existait aussi un excès de connectivité chez les synesthètes entre les régions auditives primaires et la VWFA lors de l’écoute de langage par rapport au silence. Enfin, nous avons souligné l’importance de cette connectivité fronto-occipitale en étudiant le cas d’un patient atteint d’une cécité corticale suite à des lésions des aires associatives visuelles, avec épargne partielle du cortex visuel primaire. Malgré l’absence de conscience du patient de toute stimulation visuelle, celle-ci activait chez lui une région du cortex visuel primaire. Par rapport aux contrôles, cette région avait une connectivité au repos diminuée avec une région frontale gauche, déjà identifiée comme ayant un rôle dans la prise de conscience de stimuli visuels. Au total, nos travaux ont permis de mieux caractériser le phénomène de la TTS, et d’en préciser les substrats neuronaux. Ils ont aussi apporté des arguments pour le rôle des régions impliquées dans les modèles actuels du langage et de la lecture
The brain networks involved in speech and written language are connected and interact when we use one or the other. For example, when we hear speech, we access information about the spelling of what we hear, and conversely when we read, we access phonological information about the content. The visual word form area (VWFA), located in the left fusiform gyrus, plays an important role in these interactions. This area is specialized in letter and word recognition, and appears with the learning to read. Synesthesia is defined as a "fusion of the senses": perception in one sensory modality is accompanied by superadded perception in another, unsolicited sensory modality. There is a synesthesia that links speech and written language processes, called tickertape synesthesia (TTS), in which the person perceives the orthographic form of what he or she hears. Our hypothesis was that the regions responsible for TTS were the perisylvian regions involved in language, and the visual regions involved in spelling processing. We also predicted that this phenomenon was linked to a reverse activation of the reading network, underpinned by top-down influences from language areas to reading areas that were too strong. We explored this synesthesia through a series of complementary studies. We administered a questionnaire to people with this synaesthesia, which enabled us to better characterize the subjective experience of TTS, including the visuo-spatial aspects of subtitles and the type of auditory stimulus or situation that can trigger TTS. We also showed that there were differences in performance on behavioral tests. Synesthetes had an advantage on tasks involving orthographic working memory on auditory stimulation alone, but were not impaired on visual tasks with interference via concomitant auditory stimulation. We identified the neural networks activated during TTS, first in a single synesthete, and then replicated these results across an entire group. These regions correspond to the perisylvian regions involved in language and the ventral occipitotemporal regions involved in orthographic processing. The networks activated in TTS were overlapped with those activated by reading. These results thus confirmed our initial hypotheses. We also showed that there was an excess of connectivity at rest in synesthetes, notably between the frontal and occipital regions. There was also an excess of connectivity in synesthetes between primary auditory regions and the VWFA during language listening compared with silence. Finally, we highlighted the importance of this fronto-occipital connectivity by studying the case of a patient with cortical blindness following lesions of the visual associative areas, with partial sparing of the primary visual cortex. Despite the patient's lack of awareness of any visual stimulation, it activated a region of the primary visual cortex. Compared with controls, this region had diminished resting connectivity with a left frontal region, already identified as having a role in awareness of visual stimuli. In summary, our work has enabled us to better characterize the phenomenon of TTS, and to clarify its neural substrates. It has also provided arguments for the role of the regions involved in current models of language and reading