Response to short-term deprivation of the human adult visual cortex measured with 7T BOLD

Sensory deprivation during the post-natal 'critical period' leads to structural reorganization of the developing visual cortex. In adulthood, the visual cortex retains some flexibility and adapts to sensory deprivation. Here we show that short-term (2 hr) monocular deprivation in adult humans boosts the BOLD response to the deprived eye, changing ocular dominance of V1 vertices, consistent with homeostatic plasticity. The boost is strongest in V1, present in V2, V3 and V4 but absent in V3a and hMT+. Assessment of spatial frequency tuning in V1 by a population Receptive-Field technique shows that deprivation primarily boosts high spatial frequencies, consistent with a primary involvement of the parvocellular pathway. Crucially, the V1 deprivation effect correlates across participants with the perceptual increase of the deprived eye dominance assessed with binocular rivalry, suggesting a common origin. Our results demonstrate that visual cortex, particularly the ventral pathway, retains a high potential for homeostatic plasticity in the human adult

brainlife.io: a decentralized and open-source cloud platform to support neuroscience research

Neuroscience is advancing standardization and tool development to support rigor and transparency. Consequently, data pipeline complexity has increased, hindering FAIR (findable, accessible, interoperable and reusable) access. brainlife.io was developed to democratize neuroimaging research. The platform provides data standardization, management, visualization and processing and automatically tracks the provenance history of thousands of data objects. Here, brainlife.io is described and evaluated for validity, reliability, reproducibility, replicability and scientific utility using four data modalities and 3,200 participants

Non-neural factors influencing BOLD response magnitudes within individual subjects

To what extent is the size of the blood-oxygen-level-dependent (BOLD) response influenced by factors other than neural activity? In a re-analysis of three neuroimaging datasets (male and female human participants), we find large systematic inhomogeneities in the BOLD response magnitude in primary visual cortex (V1): stimulus-evoked BOLD responses, expressed in units of percent signal change, are up to 50% larger along the representation of the horizontal meridian than the vertical meridian. To assess whether this surprising effect can be interpreted as differences in local neural activity, we quantified several factors that potentially contribute to the size of the BOLD response. We find relationships between BOLD response magnitude and cortical thickness, curvature, depth and macrovasculature. These relationships are consistently found across subjects and datasets and suggest that variation in BOLD response magnitudes across cortical locations reflects, in part, differences in anatomy and vascularization. To compensate for these factors, we implement a regression-based correction method and show that after correction, BOLD responses become more homogeneous across V1. The correction reduces the horizontal/vertical difference by about half, indicating that some of the difference is likely not due to neural activity differences. We conclude that interpretation of variation in BOLD response magnitude across cortical locations should consider the influence of the potential confounding factors of thickness, curvature, depth and vascularization. SIGNIFICANCE STATEMENTThe magnitude of the BOLD signal is often used as a surrogate of neural activity, but the exact factors that contribute to its strength have not been studied on a voxel-wise level. Here, we examined several anatomical and measurement-related factors to assess their relationship with BOLD signal magnitude. We find that BOLD magnitude correlates with cortical anatomy, depth and macrovasculature. To remove the contribution of these factors, we propose a simple, data-driven correction method that can be used in any functional magnetic resonance imaging (fMRI) experiment. After accounting for the confounding factors, BOLD magnitude becomes more spatially homogenous. Our correction method improves the ability to make more accurate inferences about local neural activity from fMRI data

Data from: Response to short-term deprivation of the human adult visual cortex measured with 7T BOLD

Large .mat file (readable from matlab) holding all the fMRI and psychophysical data reported in the manuscript. see readme file for details on how variables are formatted and what information is stored in each of them. ---------NOTE: The original file "alldata.mat" was removed to protect the privacy of study participants in accordance with the agreement under which the data were acquired. A new version of the file is available at https://doi.org/10.5061/dryad.tp24j18.

Normal Retinotopy in Primary Visual Cortex in a Congenital Complete Unilateral Lesion of Lateral Geniculate Nucleus in Human: A Case Study

Impairment of the geniculostriate pathway results in scotomas in the corresponding part of the visual field. Here, we present a case of patient IB with left eye microphthalmia and with lesions in most of the left geniculostriate pathway, including the Lateral Geniculate Nucleus (LGN). Despite the severe lesions, the patient has a very narrow scotoma in the peripheral part of the lower-right-hemifield only (beyond 15° of eccentricity) and complete visual field representation in the primary visual cortex. Population receptive field mapping (pRF) of the patient’s visual field reveals orderly eccentricity maps together with contralateral activation in both hemispheres. With diffusion tractography, we revealed connections between superior colliculus (SC) and cortical structures in the hemisphere affected by the lesions, which could mediate the retinotopic reorganization at the cortical level. Our results indicate an astonishing case for the flexibility of the developing retinotopic maps where the contralateral thalamus receives fibers from both the nasal and temporal retinae

Data from: Response to short-term deprivation of the human adult visual cortex measured with 7T BOLD

Sensory deprivation during the post-natal "critical period" leads to structural reorganization of the developing visual cortex. In adulthood, the visual cortex retains some flexibility and adapts to sensory deprivation. Here we show that short-term (2h) monocular deprivation in adult humans boosts the BOLD response to the deprived eye, changing ocular dominance of V1 vertices, consistent with homeostatic plasticity. The boost is strongest in V1, present in V2, V3 &V4 but absent in V3a and hMT+. Assessment of spatial frequency tuning in V1 by a population Receptive-Field technique shows that deprivation primarily boosts high spatial frequencies, consistent with a primary involvement of the parvocellular pathway. Crucially, the V1 deprivation effect correlates across participants with the perceptual increase of the deprived eye dominance assessed with binocular rivalry, suggesting a common origin. Our results demonstrate that visual cortex, particularly the ventral pathway, retains a high potential for homeostatic plasticity in the human adult

Area Prostriata in the Human Brain

Area prostriata is a cortical area at the fundus of the calcarine sulcus, described anatomically in humans [1â5] and other primates [6â9]. It is lightly myelinated and lacks the clearly defined six-layer structure evident throughout the cerebral cortex, with a thinner layer 4 and thicker layer 2 [10], characteristic of limbic cortex [11]. In the marmoset and rhesus monkey, area prostriata has cortical connections with MT+ [12], the cingulate motor cortex [8], the auditory cortex [13], the orbitofrontal cortex, and the frontal polar cortices [14]. Here we use functional magnetic resonance together with a wide-field projection system to study its functional properties in humans. With population receptive field mapping [15], we show that area prostriata has a complete representation of the visual field, clearly distinct from the adjacent area V1. As in the marmoset, the caudal-dorsal border of human prostriataâabutting V1ârepresents the far peripheral visual field, with eccentricities decreasing toward its rostral boundary. Area prostriata responds strongly to very fast motion, greater than 500°/s. The functional properties of area prostriata suggest that it may serve to alert the brain quickly to fast visual events, particularly in the peripheral visual field. Mikellidou et al. describe functionally area prostriata in humans. Located at the fundus of the calcarine sulcus, it has an orderly representation of the contralateral visual field, evenly distributed receptive fields, and a preference for fast motion. Prostriata may be alerting the brain to rapidly appearing visual events, mainly in the periphery

Three dimensional MRF obtains highly repeatable and reproducible multi-parametric estimations in the healthy human brain at 1.5T and 3T.

Magnetic resonance fingerprinting (MRF) is highly promising as a quantitative MRI technique due to its accuracy, robustness, and efficiency. Previous studies have found high repeatability and reproducibility of 2D MRF acquisitions in the brain. Here, we have extended our investigations to 3D MRF acquisitions covering the whole brain using spiral projection k-space trajectories. Our travelling head study acquired test/retest data from the brains of 12 healthy volunteers and 8 MRI systems (3 systems at 3 T and 5 at 1.5 T, all from a single vendor), using a study design not requiring all subjects to be scanned at all sites. The pulse sequence and reconstruction algorithm were the same for all acquisitions. After registration of the MRF-derived PD T1 and T2 maps to an anatomical atlas, coefficients of variation (CVs) were computed to assess test/retest repeatability and inter-site reproducibility in each voxel, while a General Linear Model (GLM) was used to determine the voxel-wise variability between all confounders, which included test/retest, subject, field strength and site. Our analysis demonstrated a high repeatability (CVs 0.7-1.3% for T1, 2.0-7.8% for T2, 1.4-2.5% for normalized PD) and reproducibility (CVs of 2.0-5.8% for T1, 7.4-10.2% for T2, 5.2-9.2% for normalized PD) in gray and white matter. Both repeatability and reproducibility improved when compared to similar experiments using 2D acquisitions. Three-dimensional MRF obtains highly repeatable and reproducible estimations of T1 and T2, supporting the translation of MRF-based fast quantitative imaging into clinical applications.This research was funded by the Italian Ministry of Health and by Tuscany Region under the project ‘Ricerca Finalizzata’, grant no. GR-2016-02361693. Funding from the Tuscany Government under the project Q-MRI of the Intervention Program INFN- RT2 172800 (Bando GiovaniSi 2017 - POR FSE 2014-2020). Funding from the EMPIR Unrestricted 151 Programme (18HLT05 QUIERO Project) co-financed by the Participating States an from the European Union’s Horizon 2020 Research and Innovation Programme. TM, JDK, FAG are supported by the NIHR Cambridge BRC. The views expressed are those of authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care

Earthquake nucleation in weak subducted carbonates

Ocean-floor carbonate- and clay-rich sediments form major inputs to subduction zones, especially at low-latitude convergent plate margins. Therefore, knowledge of their frictional behaviour is fundamental for understanding plate-boundary earthquakes. Here we report results of mechanical tests performed on simulated fault gouges prepared from ocean-floor carbonates and clays, cored during IODP drilling offshore Costa Rica. Clay-rich gouges show internal friction coefficients (that is, the slope of linearized shear stress versus normal stress data) of μint = 0.44 − 0.56, irrespective of temperature and pore-fluid pressure (Pf). By contrast, μint for the carbonate gouge strongly depends on temperature and pore-fluid pressure, with μint decreasing dramatically from 0.84 at room temperature and Pf = 20 MPa to 0.27 at T = 140 °C and Pf = 120 MPa. This effect provides a fundamental mechanism of shear localization and earthquake generation in subduction zones, and makes carbonates likely nucleation sites for plate-boundary earthquakes. Our results imply that rupture nucleation is prompted by a combination of temperature-controlled frictional instability and temperature- and pore-pressure-dependent weakening of calcareous fault gouges