Heteromodal brain areas common to production, listening and reading tasks at the word Level: an fMRI study of 144 right-handers from the BIL&GIN

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Cortical Terminations of the Inferior Fronto-Occipital and Uncinate Fasciculi: Anatomical Stem-Based Virtual Dissection

International audienceWe combined the neuroanatomists' approach of defining a fascicle as all fibers passing through its compact stem with diffusion-weighted tractography to investigate the cortical terminations of two association tracts, the inferior fronto-occipital fasciculus (IFOF) and the uncinate fasciculus (UF), which have recently been implicated in the ventral language circuitry. The aim was to provide a detailed and quantitative description of their terminations in 60 healthy subjects and to do so to apply an anatomical stem-based virtual dissection, mimicking classical post-mortem dissection, to extract with minimal a priori the IFOF and UF from tractography datasets. In both tracts, we consistently observed more extensive termination territories than their conventional definitions, within the middle and superior frontal, superior parietal and angular gyri for the IFOF and the middle frontal gyrus and superior, middle and inferior temporal gyri beyond the temporal pole for the UF. We revealed new insights regarding the internal organization of these tracts by investigating for the first time the frequency, distribution and hemispheric asymmetry of their terminations. Interestingly, we observed a dissociation between the lateral right-lateralized and medial left-lateralized fronto-occipital branches of the IFOF. In the UF, we observed a rightward lateralization of the orbito-frontal and temporal branches. We revealed a more detailed map of the terminations of these fiber pathways that will enable greater specificity for correlating with diseased populations and other behavioral measures. The limitations of the diffusion tensor model in this study are also discussed. We conclude that anatomical stem-based virtual dissection with diffusion tractography is a fruitful method for studying the structural anatomy of the human white matter pathways

Evaluation of the dual route theory of reading: a metanalysis of 35 neuroimaging studies

International audienceNumerous studies concerned with cerebral structures underlying word reading have been published during the last decade. A fewcontroversies, however, together with methodological or theoretical discrepancies between laboratories, still contribute to blurring theoverall view of advances effected in neuroimaging. Carried out within the dual route of reading framework, the aim of this metanalysis wasto provide an objective picture of these advances. To achieve this, we used an automated analysis method based on the inventory ofactivation peaks issued from word or pseudoword reading contrasts of 35 published neuroimaging studies. A first result of this metanalysiswas that no cluster of activations has been found more recruited by word than pseudoword reading, implying that the first steps of wordaccess may be common to word and word-like stimuli and would take place within a left occipitotemporal region (previously referred toas the Visual Word Form Area—VWFA) situated in the ventral route, at the junction between inferior temporal and fusiform gyri. Theresults also indicated the existence of brain regions predominantly involved in one of the two routes to access word. The graphophonologicalconversion seems indeed to rely on left lateralized brain structures such as superior temporal areas, supramarginal gyrus, and the opercularpart of the inferior frontal gyrus, these last two regions reflecting a greater load in working memory during such an access. Thelexicosemantic route is thought to arise from the coactivation of the VWFA and semantic areas. These semantic areas would encompass abasal inferior temporal area, the posterior part of the middle temporal gyrus, and the triangular part of inferior frontal gyrus. These resultsconfirm the suitability of the dual route framework to account for activations observed in nonpathological subjects while they read

La lecture de textes (aspects psychologiques et anatomo-fonctionnels)

CAEN-BU Droit Lettres (141182101) / SudocSudocFranceF

Word Meaning Contributes to Free Recall Performance in Supraspan Verbal List-Learning Tests

International audienceSupraspan verbal list-learning tests, such as the Rey Auditory Verbal Learning Test (RAVLT), are classic neuropsychological tests for assessing verbal memory. In this study, we investigated the impact of the meaning of the words to be learned on three memory stages [short-term recall (STR), learning, and delayed recall (DR)] in a cohort of 447 healthy adults. First, we compared scores obtained from the RAVLT (word condition) to those of an alternative version of this test using phonologically similar but meaningless items (pseudoword condition) and observed how each score varied as a function of age and sex. Then, we collected the participants' self-reported strategies to retain the word and pseudoword lists and examined if these strategies mediated the age and sex effects on memory scores. The word condition resulted in higher memory scores than pseudoword condition at each memory stage and even canceled out, for the learning stage, the detrimental effect of age that was observed for the short-term and DR. When taking sex into account, the word advantage was observed only in women for STR. The self-reported strategies, which were similar for words and pseudowords, were based on the position of the item on the list (word: 53%, pseudoword: 37%) or the meaning of the item (word: 64%, pseudoword: 58%) and were used alone or in combination. The best memory performance was associated with the meaning strategy in the word condition and with the combination of the meaning and position strategies in the pseudoword condition. Finally, we found that the word advantage observed in women for STR was mediated by the use of the meaning strategy. The RAVLT scores were thus highly dependent on word meaning, notably because it allowed efficient semantic knowledge-based strategies. Within the framework of Tulving's declarative memory model, these results are at odds with the depiction of the RAVLT as a verbal episodic memory test as it is increasingly referred to in the literature

Norms of vocabulary, reading, and spelling tests in French university students

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A shared neural substrate for mentalizing and the affective component of sentence comprehension.

Using event-related fMRI in a sample of 42 healthy participants, we compared the cerebral activity maps obtained when classifying spoken sentences based on the mental content of the main character (belief, deception or empathy) or on the emotional tonality of the sentence (happiness, anger or sadness). To control for the effects of different syntactic constructions (such as embedded clauses in belief sentences), we subtracted from each map the BOLD activations obtained during plausibility judgments on structurally matching sentences, devoid of emotions or ToM. The obtained theory of mind (ToM) and emotional speech comprehension networks overlapped in the bilateral temporo-parietal junction, posterior cingulate cortex, right anterior temporal lobe, dorsomedial prefrontal cortex and in the left inferior frontal sulcus. These regions form a ToM network, which contributes to the emotional component of spoken sentence comprehension. Compared with the ToM task, in which the sentences were enounced on a neutral tone, the emotional sentence classification task, in which the sentences were play-acted, was associated with a greater activity in the bilateral superior temporal sulcus, in line with the presence of emotional prosody. Besides, the ventromedial prefrontal cortex was more active during emotional than ToM sentence processing. This region may link mental state representations with verbal and prosodic emotional cues. Compared with emotional sentence classification, ToM was associated with greater activity in the caudate nucleus, paracingulate cortex, and superior frontal and parietal regions, in line with behavioral data showing that ToM sentence comprehension was a more demanding task

MEG Encoding using Neural Language & Speech Models and Shared Context Semantics in Listening Stories

International audienceWe investigate if speech models outperform language models during speech-evoked brain activity, if LM and SM combine new word representation with previous context, and what are time of information is shared between them

Multi-factorial modulation of hemispheric specialization and plasticity for language in healthy and pathological conditions: A review

International audienceThis review synthesizes anatomo-functional variability of language hemispheric representation and specialization (hemispheric specialization for language, HSL) as well as its modulation by several variables (demographic, anatomical, developmental, genetic, clinical, and psycholinguistic) in physiological and pathological conditions. The left hemisphere (LH) dominance for language, observed in approximately 90% of healthy individuals and in 70% of patients, is grounded by intra-hemispheric connections mediated by associative bundles such as the arcuate fasciculus and inter-hemispheric transcallosal connections mediated by the corpus callosum that connects homotopic regions of the left and right hemispheres (RH). In typical brains, inter-hemispheric inhibition, exerted from the LH to the RH, permits the LH to maintain language dominance. In pathological conditions, inter- and intra-hemispheric inhibition is decreased, inducing modifications on the degree of HSL and of language networks. HSL evaluation is classically performed in clinical practice with the Wada test and electro-cortical stimulation, gold standard methods. The advent of functional neuroimaging has allowed a more detailed assessment of the language networks and their lateralization, consistent with the results provided by the gold standard methods. In the first part, we describe anatomo-functional support for HSL in healthy conditions, its developmental course, its relationship with cognitive skills, and the various modulatory factors acting on HSL. The second section is devoted to the assessment of HSL in patients with focal and drug-resistant epilepsy (FDRE). FDRE is considered a neurological model associated with patterns of language plasticity, both before and after surgery: FDRE patients show significant modification of language networks induced by changes mediated by transcallosal connections (explaining inter-hemispheric patterns of language reorganization) or collateral connections (explaining intra-hemispheric patterns of language reorganization). Finally, we propose several predictive and explicative models of language organization and reorganization

Response profile of Medial-network nodes (mean ± SEM).

<p>The BOLD contrast values during the EMO, GRAM, and PLAUEMO tasks (blue shades), and TOM and PLAUTOM tasks (green shades), relative to beep-detection baseline, were extracted in the 6 regions of the Medial network defined in a previous study using the EMO and GRAM tasks (dmPFC, vmPFC, pCC and Left TPJ; blue labels, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0054400#pone.0054400-Herv1" target="_blank">[5]</a>). The coloured spheres (4 mm radius) indicate the regions-of-interest. We added the two mentalizing regions of the right hemisphere (R TPJ and R MTG; green labels), uncovered by the addition of the TOM, PLAUTOM and PLAUEMO tasks.</p