82 research outputs found
Neural Aspects of Sentence Comprehension: Syntactic Complexity, Reversibility, and Reanalysis
Broca's area is preferentially activated by reversible sentences with complex syntax, but various linguistic factors may be responsible for this finding, including syntactic movement, working-memory demands, and post hoc reanalysis. To distinguish between these, we tested the interaction of syntactic complexity and semantic reversibility in a functional magnetic resonance imaging study of sentenceâpicture matching. During auditory comprehension, semantic reversibility induced selective activation throughout the left perisylvian language network. In contrast, syntactic complexity (object-embedded vs. subject-embedded relative clauses) within reversible sentences engaged only the left inferior frontal gyrus (LIFG) and left precentral gyrus. Within irreversible sentences, only the LIFG was sensitive to syntactic complexity, confirming a unique role for this region in syntactic processing. Nonetheless, larger effects of reversibility itself occurred in the same regions, suggesting that full syntactic parsing may be a nonautomatic process applied as needed. Complex reversible sentences also induced enhanced signals in LIFG and left precentral regions on subsequent picture selection, but with additional recruitment of the right hemisphere homolog area (right inferior frontal gyrus) as well, suggesting that post hoc reanalysis of sentence structure, compared with initial comprehension, engages an overlapping but larger network of brain regions. These dissociable effects may offer a basis for studying the reorganization of receptive language function after brain damage
A Network Analysis Approach to fMRI Condition-Specific Functional Connectivity
In this work we focus on examination and comparison of whole-brain functional
connectivity patterns measured with fMRI across experimental conditions. Direct
examination and comparison of condition-specific matrices is challenging due to
the large number of elements in a connectivity matrix. We present a framework
that uses network analysis to describe condition-specific functional
connectivity. Treating the brain as a complex system in terms of a network, we
extract the most relevant connectivity information by partitioning each network
into clusters representing functionally connected brain regions. Extracted
clusters are used as features for predicting experimental condition in a new
data set. The approach is illustrated on fMRI data examining functional
connectivity patterns during processing of abstract and concrete concepts.
Topological (brain regions) and functional (level of connectivity and
information flow) systematic differences in the ROI-based functional networks
were identified across participants for concrete and abstract concepts. These
differences were sufficient for classification of previously unseen
connectivity matrices as abstract or concrete based on training data derived
from other people
Priming Picture Naming with a Semantic Task: An fMRI Investigation
Prior semantic processing can enhance subsequent picture naming performance, yet the neurocognitive mechanisms underlying this effect and its longevity are unknown. This functional magnetic resonance imaging study examined whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from a semantic task in healthy older adults. Both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Region of interest results identified decreased activity for long-term facilitated items compared to unfacilitated and short-term facilitated items in the mid-portion of the middle temporal gyrus, indicating lexical-semantic priming. Additionally, in the whole brain results, increased activity for short-term facilitated items was identified in regions previously linked to episodic memory and object recognition, including the right lingual gyrus (extending to the precuneus region) and the left inferior occipital gyrus (extending to the left fusiform region). These findings suggest that distinct neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by a semantic task, with long-term effects driven by lexical-semantic priming and short-term effects by episodic memory and visual object recognition mechanisms
The neural correlates of picture naming facilitated by auditory repetition
Background: Overt repetition of auditorily presented words can facilitate picture naming performance in both unimpaired speakers and individuals with word retrieval difficulties, but the underlying neurocognitive mechanisms and longevity of such effects remain unclear. This study used functional magnetic resonance imaging to examine whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from an auditory repetition task in healthy older adults
6. Neuro-imagerie fonctionnelle et Ă©tude de la rĂ©cupĂ©ration du langage dans lâaphasie
Lâaphasie est observĂ©e dans environ un 1/3 des cas dâaccident vasculaire cĂ©rĂ©bral dont lâincidence en France est estimĂ©e Ă environ 150 000 par an. Lâaphasie est aussi caractĂ©risĂ©e par une tendance spontanĂ©e Ă la rĂ©cupĂ©ration plus ou moins complĂšte, faisant de lâaphasie vasculaire primo-lĂ©sionnelle une sorte de « modĂšle » pathologique chez lâHomme dans lequel le cerveau sâadapte Ă une lĂ©sion et certaines fonctions du langage doivent faire lâobjet dâune rĂ©installation ou dâun rĂ©-apprentissage. ..
[Functional neuroimaging and the treatment of aphasia: speech therapy and repetitive transcranial magnetic stimulation]
International audienceFunctional imaging has provided new evidence of the neurobiological impact of the treatment of aphasia, including speech therapy, through the alteration of the activated language neural network. In such a way, speech therapy has proved its impact. The role of each hemisphere is still very unclear. Some of the authors link the left-lateralisation of activations to the therapeutic improvement of language and the right-activated network to a maladaptative strategy, whereas others consider the latter as a useful compensatory network for speech disorders. Repetitive trans-cranial magnetic stimulation (rTMS), first used to determine cortical activity, is now used to directly interfere with cerebral activity. In the years to come, rTMS should be developed as an adjuvant therapy for aphasia
Statistical Mapping Analysis of Brain Metabolism in Patients with Subcortical Aphasia after Intracerebral Hemorrhage: A Pilot Study of F-18 FDG PET Images
Neurocognition of New Word Learning in the Native Tongue: Lessons From the Ancient Farming Equipment Paradigm
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