Whole-brain deactivations precede uninduced mind-blanking reports

tMind-blanking (MB) is termed as the experience of inability to report mental contents. In contrast to other mental states, such as mind-wandering or sensory perceptions, the neural correlates of MB started getting elucidated only recently. A notable particularity that pertains to MB studies is the way MB is instructed for reports, like by deliberately asking participants to “empty their minds”. Such instructions were shown to induce fMRI activations in frontal brain regions, typically associated with metacognition and self-evaluative processes, suggesting that MB may be a result of intentional mental content suppression. Here, we aim at examining this hypothesis by determining the neural correlates of MB without induction. Using fMRI combined with experience-sampling, univariate analysis of MB reports revealed deactivations in occipital, frontal, somatosensory, and thalamic areas, but no activations in prefrontal regions. In fact, a Bayesian region-of-interest analysis on areas previously shown to be implicated in MB provided evidence for frontal deactivations during MB reports in comparison to other mental states. Further contrast analysis between reports of MB and content-oriented mental states also revealed deactivations in the L angular gyrus. We propose that these effects characterize a cortical profile of MB, where key cortical nodes are unable to communicate and formulate reportable content. Collectively, our results show that study instructions for MB may lead to cortical differences which provide different insights as to the underlying mechanisms leading to the phenomenology of MB.Significance StatementAn emergent research paradigm in the study of mental states has focused on periods of complete thought absence, where people report an inability to report mental content, termed mind blanking. The neural correlates supporting mind blanking are still debated and might vary depending on thought-report instructions. By reanalyzing an fMRI dataset utilizing an unguided, free-thinking paradigm, the present study provides critical insights into the neuronal events that preceded mind-blanking reports. Our findings demonstrate that spontaneous mind-blanking occurrences are associated with large-scale cortical deactivations in frontal, occipital, parietal and thalamical sites, with the frontal evaluative sites and the angular gyrus especially differentiating mind-blanking from other mental states associated with the presence of content

Fluctuations of attention network activation during the resting state reflect fluctuations in subjective attentional state.

peer reviewe

Neural patterns in linguistic cortices discriminate the content of verbal working memory

Verbal working memory (WM) is characterized by the presence of psycholinguistic effects, whereby items associated with richer linguistic representations are usually better recalled, such as words vs. nonwords (lexicality effect). This effect is accounted for by language-based models, assuming a direct and obligatory involvement of lexical linguistic knowledge at all stages of WM processing or by redintegration models considering that lexical linguistic knowledge only intervenes during post-memory trace reconstructive processes. We contrasted these two accounts in functional neuroimaging experiment by assessing to what extent and at what WM stage word and nonword memoranda can be distinguished based on their multivariate neural patterns in linguistic cortices. fMRI scans were obtained from 28 healthy young adult participants. The participants were invited to encode lists composed of word or nonword items presented at a very fast rate (2 items/s) and to maintain the items over a 6-second delay or not, followed by a probe recognition phase. Multivariate voxel pattern analyses successfully decoded word and nonword stimuli during the encoding phase in all conditions, as well as during the maintenance phase but only during the active maintenance condition. This study supports language-based WM models assuming continuous support of linguistic knowledge during all WM stages

Cross-Modal Decoding of Neural Patterns Associated with Working Memory:Evidence for Attention-Based Accounts of Working Memory

Recent studies suggest common neural substrates involved in verbal and visual working memory (WM), interpreted as reflecting shared attention-based, short-term retention mechanisms. We used a machine-learning approach to determine more directly the extent to which common neural patterns characterize retention in verbal WM and visual WM. Verbal WM was assessed via a standard delayed probe recognition task for letter sequences of variable length. Visual WM was assessed via a visual array WM task involving the maintenance of variable amounts of visual information in the focus of attention. We trained a classifier to distinguish neural activation patterns associated with high- and low-visual WM load and tested the ability of this classifier to predict verbal WM load (high–low) from their associated neural activation patterns, and vice versa. We observed significant between-task prediction of load effects during WM maintenance, in posterior parietal and superior frontal regions of the dorsal attention network; in contrast, between-task prediction in sensory processing cortices was restricted to the encoding stage. Furthermore, between-task prediction of load effects was strongest in those participants presenting the highest capacity for the visual WM task. This study provides novel evidence for common, attention-based neural patterns supporting verbal and visual WM

Cortico-Cerebellar Pathways for Understanding Language Coordination

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Mon cerveau, un ordinateur ?!

Dôter les ordinateur d'un cerveau ou faire assister nos cerveaux par des ordinateurs ? Trois chercheurs abordaient ces thématiques lors d'un Doc'Café mi-homme, mi-machine