Novel characterization of the relationship between verbal list-learning outcomes and hippocampal subfields in healthy adults.

The relationship between hippocampal subfield volumetry and verbal list-learning test outcomes have mostly been studied in clinical and elderly populations, and remain controversial. For the first time, we characterized a relationship between verbal list-learning test outcomes and hippocampal subfield volumetry on two large separate datasets of 447 and 1,442 healthy young and middle-aged adults, and explored the processes that could explain this relationship. We observed a replicable positive linear correlation between verbal list-learning test free recall scores and CA1 volume, specific to verbal list learning as demonstrated by the hippocampal subfield volumetry independence from verbal intelligence.

Cerebral small vessel disease genomics and its implications across the lifespan.

White matter hyperintensities (WMH) are the most common brain-imaging feature of cerebral small vessel disease (SVD), hypertension being the main known risk factor. Here, we identify 27 genome-wide loci for WMH-volume in a cohort of 50,970 older individuals, accounting for modification/confounding by hypertension. Aggregated WMH risk variants were associated with altered white matter integrity (p = 2.

Development of handedness, anatomical and functional brain lateralization.

The present chapter offers a report on the recent literature on the neural bases of hemispheric specialization (HS), anatomical and functional developmental timecourse of HS, and on the available knowledge of their relationships with the development of handedness. Strong anatomical asymmetries can be seen located along the end of the sylvian fissure and the superior temporal sulcus (STS) as soon as the 23rd gestational week. They correspond to a leftward sulcal depth asymmetry of the Sylvian fissure coupled with a rightward asymmetry of STS.

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

Supraspan 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.

A population-based atlas of the human pyramidal tract in 410 healthy participants.

With the advances in diffusion MRI and tractography, numerous atlases of the human pyramidal tract (PyT) have been proposed, but the inherent limitation of tractography to resolve crossing bundles within the centrum semiovale has so far prevented the complete description of the most lateral PyT projections. Here, we combined a precise manual positioning of individual subcortical regions of interest along the descending pathway of the PyT with a new bundle-specific tractography algorithm. This later is based on anatomical priors to improve streamlines tracking in crossing areas.

What Are the Contributions of Handedness, Sighting Dominance, Hand Used to Bisect, and Visuospatial Line Processing to the Behavioral Line Bisection Bias?

In a sample of 60 French participants, we examined whether the variability in the behavioral deviation measured during the classical "paper and pencil" line bisection task was explained by individual laterality factors such as handedness and eye sighting dominance, as well as the hand used to bisect, and the spatial position of the line to bisect. The results showed the expected main effects of line position and hand used to bisect, as well as some interactions between factors. Specifically, the effect of the hand used to bisect on the deviation bias was different as a function of handedness and line position.

Predicting hemispheric dominance for language production in healthy individuals using support vector machine.

We used a Support Vector Machine (SVM) classifier to assess hemispheric pattern of language dominance of 47 individuals categorized as non-typical for language from their hemispheric functional laterality index (HFLI) measured on a sentence minus word-list production fMRI-BOLD contrast map. The SVM classifier was trained at discriminating between Dominant and Non-Dominant hemispheric language production activation pattern on a group of 250 participants previously identified as Typicals (HFLI strongly leftward). Then, SVM was applied to each hemispheric language activation pattern of 47 non-typical individuals.

Pseudoneglect in line bisection judgement is associated with a modulation of right hemispheric spatial attention dominance in right-handers.

The objective of this study was to validate a line bisection judgement (LBJ) task for use in investigating the lateralized cerebral bases of spatial attention in a sample of 51 right-handed healthy participants. Using functional magnetic resonance imaging (fMRI), the participants performed a LBJ task that was compared to a visuomotor control task during which the participants made similar saccadic and motoric responses. Cerebral lateralization was determined using a voxel-based functional asymmetry analysis and a hemispheric functional lateralization index (HFLI) computed from fMRI contrast images.

Revisiting the human uncinate fasciculus, its subcomponents and asymmetries with stem-based tractography and microdissection validation.

Despite its significant functional and clinical interest, the anatomy of the uncinate fasciculus (UF) has received little attention. It is known as a 'hook-shaped' fascicle connecting the frontal and anterior temporal lobes and is believed to consist of multiple subcomponents. However, the knowledge of its precise connectional anatomy in humans is lacking, and its subcomponent divisions are unclear.

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

We 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.

The association between hemispheric specialization for language production and for spatial attention depends on left-hand preference strength.

Cerebral lateralization for language production and spatial attention and their relationships with manual preference strength (MPS) were assessed in a sample of 293 healthy volunteers, including 151 left-handers, using fMRI during covert sentence production (PROD) and line bisection judgment (LBJ) tasks, as compared to high- and low-level reference tasks. At the group level, we found the expected complementary hemispheric specialization (HS) with leftward asymmetries for PROD within frontal and temporal regions and rightward asymmetries for LBJ within frontal and posterior occipito-parieto-temporal regions. Individual hemispheric (HLI) and regional (frontal and occipital) lateralization indices (LI) were then calculated on the activation maps for PROD and LBJ.

What Is the Role of Manual Preference in Hand-Digit Mapping During Finger Counting? A Study in a Large Sample of Right- and Left-Handers.

The goal of the present study was to test whether there is a relationship between manual preference and hand-digit mapping in 369 French adults with similar numbers of right- and left-handers. Manual laterality was evaluated with the finger tapping test to evaluate hand motor asymmetry, and the Edinburgh handedness inventory was used to assess manual preference strength (MPS) and direction. Participants were asked to spontaneously "count on their fingers from 1 to 10" without indications concerning the hand(s) to be used.

AICHA: An atlas of intrinsic connectivity of homotopic areas.

Background: Atlases of brain anatomical ROIs are widely used for functional MRI data analysis. Recently, it was proposed that an atlas of ROIs derived from a functional brain parcellation could be advantageous, in particular for understanding how different regions share information. However, functional atlases so far proposed do not account for a crucial aspect of cerebral organization, namely homotopy, i.

Strong rightward lateralization of the dorsal attentional network in left-handers with right sighting-eye: an evolutionary advantage.

Hemispheric lateralization for spatial attention and its relationships with manual preference strength and eye preference were studied in a sample of 293 healthy individuals balanced for manual preference. Functional magnetic resonance imaging was used to map this large sample while performing visually guided saccadic eye movements. This activated a bilateral distributed cortico-subcortical network in which dorsal and ventral attentional/saccadic pathways elicited rightward asymmetrical activation depending on manual preference strength and sighting eye.

Gaussian mixture modeling of hemispheric lateralization for language in a large sample of healthy individuals balanced for handedness.

Hemispheric lateralization for language production and its relationships with manual preference and manual preference strength were studied in a sample of 297 subjects, including 153 left-handers (LH). A hemispheric functional lateralization index (HFLI) for language was derived from fMRI acquired during a covert sentence generation task as compared with a covert word list recitation. The multimodal HFLI distribution was optimally modeled using a mixture of 3 and 4 Gaussian functions in right-handers (RH) and LH, respectively.

Revisiting human hemispheric specialization with neuroimaging.

Hemispheric specialization (HS) is a hemisphere-dependent relationship between a cognitive, sensory, or motor function and a set of brain structures. It includes both the hosting by a given hemisphere of specialized networks that have unique functional properties and mechanisms that enable the inter-hemispheric coordination necessary for efficient processing. Long derived from neuropsychological and behavioral observations, knowledge of HS is currently being profoundly modified by cutting-edge neuroimaging research that focuses both on the neural implementation of HS for language, visuospatial functions, and motor control/handedness across development and on the analysis of interactions between brain regions within and across hemispheres.

A novel group ICA approach based on multi-scale individual component clustering. Application to a large sample of fMRI data.

Functional connectivity-based analysis of functional magnetic resonance imaging data (fMRI) is an emerging technique for human brain mapping. One powerful method for the investigation of functional connectivity is independent component analysis (ICA) of concatenated data. However, this research field is evolving toward processing increasingly larger database taking into account inter-individual variability.

Patterns of hemodynamic low-frequency oscillations in the brain are modulated by the nature of free thought during rest.

During conscious rest, the mind switches into a state of wandering. Although this rich inner experience occupies a large portion of the time spent awake, how it relates to brain activity has not been well explored. Here, we report the results of a behavioral and functional magnetic resonance imaging (fMRI) study of the continuous resting state in 307 healthy participants.

Sex-dependent modulation of activity in the neural networks engaged during emotional speech comprehension.

Studies using event related potentials have shown that men are more likely than women to rely on semantic cues when understanding emotional speech. In a previous functional Magnetic Resonance Imaging (fMRI) study, using an affective sentence classification task, we were able to separate areas involved in semantic processing and areas involved in the processing of affective prosody (Beaucousin et al., 2007).

Brain activity at rest: a multiscale hierarchical functional organization.

Spontaneous brain activity was mapped with functional MRI (fMRI) in a sample of 180 subjects while in a conscious resting-state condition. With the use of independent component analysis (ICA) of each individual fMRI signal and classification of the ICA-defined components across subjects, a set of 23 resting-state networks (RNs) was identified. Functional connectivity between each pair of RNs was assessed using temporal correlation analyses in the 0.

A common neural system is activated in hearing non-signers to process French sign language and spoken French.

We used functional magnetic resonance imaging to investigate the areas activated by signed narratives in non-signing subjects naïve to sign language (SL) and compared it to the activation obtained when hearing speech in their mother tongue. A subset of left hemisphere (LH) language areas activated when participants watched an audio-visual narrative in their mother tongue was activated when they observed a signed narrative. The inferior frontal (IFG) and precentral (Prec) gyri, the posterior parts of the planum temporale (pPT) and of the superior temporal sulcus (pSTS), and the occipito-temporal junction (OTJ) were activated by both languages.

Left hemisphere lateralization for language in right-handers is controlled in part by familial sinistrality, manual preference strength, and head size.

We investigated the effects of familial sinistrality (FS+; presence of left-handedness in one's close relatives), manual preference strength (MPS), and head size on the hemispheric lateralization of language in right-handers. Functional magnetic resonance imaging was used to map 49 individuals while listening to a story in their mother tongue. We found that individuals who had both the FS+ trait and weak MPS had no left hemisphere dominance for this lexicosyntactic task, whereas others showed a leftward functional asymmetry.