26 research outputs found
Example babyAFQ BIDS subject
No full textExample subject in BIDS for use with babyAFQ. Includes tractography and other derivatives generated by MRtrix. </p
A preference for mathematical processing outweighs the selectivity for Arabic numbers in the inferior temporal gyrus
No full textEstablishing the functional relevancy of white matter connections in the visual system and beyond
No full textFor over a century, researchers have examined the functional relevancy of white matter bundles. Consequently, many large-scale bundles spanning several centimeters have been associated in their entirety with specific brain functions, such as language or attention. However, these coarse structural–functional relationships are at odds with modern understanding of the fine-grained functional organization of human cortex, such as the mosaic of category-selective regions in ventral temporal cortex. Here, we review a multimodal approach that combines fMRI to define functional regions of interest within individual’s brains with dMRI tractography to identify the white matter bundles of the same individual. Combining these data allows to determine which subsets of streamlines within a white matter bundle connect to specific functional regions in each individual. That is, this approach identifies the functionally defined white matter sub-bundles of the brain. We argue that this approach not only enhances the accuracy of interpreting the functional relevancy of white matter bundles, but also enables segmentation of these large-scale bundles into meaningful functional units, which can then be linked to behavior with enhanced precision. Importantly, this approach has the potential for making new discoveries of the fine-grained functional relevancy of white matter connections in the visual system and the brain more broadly, akin to the flurry of research that has identified functional regions in cortex
Separate lanes for adding and reading in the white matter highways of the human brain
No full textPublished: 15 August 2019
Es OAMath and reading involve distributed brain networks and have both shared (e.g. encoding of
visual stimuli) and dissociated (e.g. quantity processing) cognitive components. Yet, to date,
the shared vs. dissociated gray and white matter substrates of the math and reading networks
are unknown. Here, we define these networks and evaluate the structural properties of
their fascicles using functional MRI, diffusion MRI, and quantitative MRI. Our results reveal
that there are distinct gray matter regions which are preferentially engaged in either math
(adding) or reading, and that the superior longitudinal and arcuate fascicles are shared across
the math and reading networks. Strikingly, within these fascicles, reading- and math-related
tracts are segregated into parallel sub-bundles and show structural differences related to
myelination. These findings open a new avenue of research that examines the contribution of
sub-bundles within fascicles to specific behaviors.This research was supported by the National Institute of Health (NIH; 1R01EY023915), by the Deutsche Forschungsgemeinschaft (DFG; GR 4850/1–1) and by an Innovation Grant from the Stanford Center for Cognitive and Neurobiological Imaging (CNI)
Repetition probability effects for inverted faces
No full textIt has been shown, that the repetition related reduction of the blood-oxygen level dependent (BOLD) signal is modulated by the probability of repetitions (P(rep)) for faces (Summerfield et al., 2008), providing support for the predictive coding (PC) model of visual perception (Rao and Ballard, 1999). However, the stage of face processing where repetition suppression (RS) is modulated by P(rep) is still unclear. Face inversion is known to interrupt higher level configural/holistic face processing steps and if modulation of RS by P(rep) takes place at these stages of face processing, P(rep) effects are expected to be reduced for inverted when compared to upright faces. Therefore, here we aimed at investigating whether P(rep) effects on RS observed for face stimuli originate at the higher-level configural/holistic stages of face processing by comparing these effects for upright and inverted faces. Similarly to previous studies, we manipulated P(rep) for pairs of stimuli in individual blocks of fMRI recordings. This manipulation significantly influenced repetition suppression in the posterior FFA, the OFA and the LO, independently of stimulus orientation. Our results thus reveal that RS in the ventral visual stream is modulated by P(rep) even in the case of face inversion and hence strongly compromised configural/holistic face processing. An additional whole-brain analysis could not identify any areas where the modulatory effect of probability was orientation specific either. These findings imply that P(rep) effects on RS might originate from the earlier stages of face processing. © 2014 Elsevier Inc
Small brains but big challenges: white matter tractography in early life samples
No full textInternational audienceIn the human brain, white matter development is a complex and long-lasting process involving intermingling micro-and macrostructural mechanisms, such as fiber growth, pruning and myelination. Did you know that all these neurodevelopmental changes strongly affect MRI signals, with consequences on tractography performances and reliability? This communication aims to elaborate on these aspects, highlighting the importance of tracking and studying the developing connections with dedicated approaches
