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Copy file name to clipboardExpand all lines: _posts/2020-10-19-eBIP-fr.md
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Une nouvelle batterie de tests permet grâce à differentes variables (perception, imagerie, vivacité) d'évaluer votre capacité à générer des images mentales.
**Attention, ce test fonctionne uniquement sur un ordinateur avec clavier. La version sur portable est en cours de développement.**
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Le saviez-vous? Environ 5% de la population ne peut pas imaginer dans le sens de _visualisation_ ou _création d'images mentales_. Ces individus ne sont par exemple pas capables d’imaginer le visage de leur propre petit/petite ami/amie ou bien d’imaginer une plage ou une forêt. Nous appelons cela **l'aphantasie**. Ces personnes peuvent rencontrer des difficultés dans l'imagination d'objets, des visages, des couleurs ou des lettres, etc.
Copy file name to clipboardExpand all lines: _posts/2022-01-26-vmi-laterality.md
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Visual mental imagery is the faculty whereby we can "visualize" objects that are not in our line of sight. Longstanding evidence dating back over thirty years has shown that unilateral brain lesions, especially in the left temporal lobe, can impair aspects of this ability. Yet, there is currently no attempt to identify analogies between these neuropsychological findings of hemispheric asymmetry and those from other neuroscientific approaches. Here, we present a critical review of the available literature on the hemispheric laterality of visual mental imagery, by looking at cross-method patterns of evidence in the domains of lesion neuropsychology, neuroimaging, and direct cortical stimulation. Results can be summarized under three main axes. First, frontoparietal networks in both hemispheres appear to be associated with visual mental imagery. Second, lateralization patterns emerge in the temporal lobes, with the left inferior temporal lobe being the most common finding in the literature for endogenously generated images, especially, but not exclusively, when orthographic material is used to ignite imagery. Third, an opposite pattern of hemispheric laterality emerges when visual mental images are induced by exogenous stimulation; direct cortical electrical stimulation tends to produce visual imagery experiences predominantly when applied to the right temporal lobe. These patterns of hemispheric asymmetry are difficult to reconcile with the dominant model of visual mental imagery, which emphasizes the implication of early sensory cortices. They suggest instead that visual mental imagery relies on large-scale brain networks, with a crucial participation of high-level visual regions in the temporal lobes.
Copy file name to clipboardExpand all lines: _posts/2022-04-26-attention-consciousness.md
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Competing theories of consciousness disagree on the role of frontoparietal networks. Here we recorded neural activity from 727 intracerebral contacts in 13 epileptic patients, while they detected near-threshold targets preceded by supra-threshold exogenous cues. Trajectory k-means clustering revealed three patterns: (1) Validly cued seen targets elicit sustained activity in right-hemisphere fronto-temporal regions, connected by superior longitudinal fasciculus (SLF) II/III, and late accumulation activity in bilateral dorsolateral prefrontal cortex and in right-hemisphere orbitofrontal cortex (SLF I/III). (2) Invalidly cued seen targets elicit early, sustained activity in the right-hemisphere reorienting network (SLF III). (3) Seen targets elicit late sustained left dorsolateral prefrontal activity. Task modeling with recurrent neural networks supported the causal contribution of these networks to conscious perception, and elucidated their interplay through excitatory-inhibitory mechanisms. We provide new, compelling evidence on the role of hemisphere-asymmetric frontoparietal networks associated with attentional enhancement and reorienting in conscious perception.
Copy file name to clipboardExpand all lines: _posts/2022-05-02-anatomy-fin.md
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Most of us can use our “mind’s eye” to mentally visualize things that are not in our direct line of sight, an ability known as visual mental imagery. Extensive left temporal damage can impair patients’ visual mental imagery experience, but the critical locus of lesion is unknown. Our recent meta-analysis of 27 fMRI studies of visual mental imagery highlighted a well-delimited region in the left lateral midfusiform gyrus, which was consistently activated during visual mental imagery, and which we called the Fusiform Imagery Node (FIN). Here we describe the connectional anatomy of FIN in neurotypical participants and in RDS, a right-handed patient with an extensive occipitotemporal stroke in the left hemisphere. The stroke provoked right homonymous hemianopia, alexia without agraphia, and color anomia. Despite these deficits, RDS had normal subjective experience of visual mental imagery and reasonably preserved behavioral performance on tests of visual mental imagery of object shape, object color, letters, faces, and spatial relationships. We found that the FIN was spared by the lesion. We then assessed the connectional anatomy of the FIN in the MNI space and in the patient’s native space, by visualizing the fibers of the inferior longitudinal fasciculus (ILF) and of the arcuate fasciculus (AF) passing through the FIN. In both spaces, the ILF connected the FIN with the anterior temporal lobe, and the AF linked it with frontal regions. Our evidence is consistent with the hypothesis that the FIN is a node of a brain network dedicated to voluntary visual mental imagery. The FIN could act as a bridge between visual information and semantic knowledge processed in the anterior temporal lobe and in the language circuits.
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