Biology subjects

Cornelissen, F. W.

Publications and source records attributed to Cornelissen, F. W..

9 recordsLinked to original sources

bioRxiv2020

White matter alterations in glaucoma and vision-deprived brains differ outside the visual system

The degree to which glaucoma has effects beyond the eye -in the brain- is unclear. We investigated white matter microstructure (WMM) alterations in 37 tracts of patients with glaucoma, monocular blindness and controls. We used reproducible methods and the advanced cloud computing platform brainlife.io. White matter tracts were subdivided into seven categories ranging from primarily involved in vision (the visual white matter) to primarily involved in cognition and motor control. WMM in both glaucoma and monocular blind subjects was lower than controls in the visual white matter, suggesting neurodegenerative mechanisms due to reduced sensory inputs. In glaucoma participants WMM differences from controls decreased outside the visual white matter. A test-retest validation approach was used to validate these results. The pattern of results was different in monocular blind participants, where WMM properties increased outside the visual white matter as compared to controls. The pattern of results suggests that whereas in the blind loss of visual input might promote white matter reorganization outside of the early visual system, such reorganization might be reduced or absent in glaucoma. The results provide indirect evidence that in glaucoma unknown factors might limit the brain plasticity effects that in other patient groups follow visual loss.

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bioRxiv2020

Assessing uncertainty in connective field estimations from resting state fMRI activity

Connective Field (CF) modeling estimates the local spatial integration between signals in distinct cortical visual field areas. As we have shown previously using 7T data, CF can reveal the visuotopic organization of visual cortical areas even when applied to BOLD activity recorded in the absence of external stimulation. This indicates that CF modeling can be used to evaluate cortical processing in participants in which the visual input may be compromised. Furthermore, by using Bayesian CF modelling it is possible to estimate the co-variability of the parameter estimates and therefore, apply CF modeling to single cases. However, no previous studies evaluated the (Bayesian) CF model using 3T resting-state fMRI data, although this is important since 3T scanners are much more abundant and more often used in clinical research than 7T ones. In this study, we investigate whether it is possible to obtain meaningful CF estimates from 3T resting state (RS) fMRI data. To do so, we applied the standard and Bayesian CF modeling approaches on two RS scans interleaved by the acquisition of visual stimulation in 12 healthy participants. Our results show that both approaches reveal good agreement between RS- and visual field (VF)-based maps. Moreover, the 3T observations were similar to those previously reported at 7T. In addition, to quantify the uncertainty associated with each estimate in both RS and VF data, we applied our Bayesian CF framework to provide the underlying marginal distribution of the CF parameters. Finally, we show how an additional CF parameter, beta, can be used as a data-driven threshold on the RS data to further improve CF estimates. We conclude that Bayesian CF modeling can characterize local functional connectivity between visual cortical areas from RS data at 3T. In particular, we expect the ability to assess parameter uncertainty in individual participants will be important for future clinical studies. HighlightsO_LILocal functional connectivity between visual cortical areas can be estimated from RS-fMRI data at 3T using both standard CF and Bayesian CF modelling. C_LIO_LIBayesian CF modelling quantifies the model uncertainty associated with each CF parameter on RS and VF data, important in particular for future studies on clinical populations. C_LIO_LI3T observations were qualitatively similar to those previously reported at 7T. C_LI

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bioRxiv2020

Visual field reconstruction using fMRI-based techniques

PurposeTo evaluate the accuracy and reliability of functional magnetic resonance imaging (fMRI)-based techniques to assess the integrity of the visual field (VF). MethodsWe combined fMRI and neurocomputational models, i.e conventional population receptive field (pRF) mapping and a new advanced pRF framework "micro-probing" (MP), to reconstruct the visual field representations of different cortical areas. To demonstrate their scope, both approaches were applied in healthy participants with simulated scotomas (SS) and participants with glaucoma. For the latter group we compared the VFs obtained with standard automated perimetry (SAP) and via fMRI. ResultsUsing SS, we found that the fMRI-based techniques can detect absolute defects in VFs that are larger than 3 deg, in single participants, and based on 12 minutes of fMRI scan time. Moreover, we found that MP results in a less biased estimation of the preserved VF. In participants with glaucoma, we found that fMRI-based VF reconstruction detected VF defects with a correspondence to SAP that was decent, reflected by the positive correlation between fMRI-based sampling density and SAP-based contrast sensitivity loss (SAP) r2=0.44, p=0.0002.This correlation was higher for our new approach (MP) compared to that for the conventional pRF analysis. ConclusionsfMRI-based reconstruction of the VF enables the evaluation of vision loss and provides useful details on the properties of the visual cortex. Translational RelevancefMRI-based VF reconstruction provides an objective alternative to detect VF defects. It may either complement SAP, or could provide VF information in patients unable to perform SAP.

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bioRxiv2020

Functional Connectivity of the Precuneus Reflects Effectiveness of Visual Restitution Training in Chronic Hemianopia

Visual field defects in chronic hemianopia can improve through visual restitution training, yet not all patients benefit equally from this long and exhaustive process. Here, we asked if resting-state functional connectivity prior to visual restitution could predict training success. In two training sessions of eight weeks each, 20 patients with chronic hemianopia performed a visual discrimination task by directing spatial attention towards stimuli presented in either hemifield, while suppressing eye movements. We examined two effects: a sensitivity change in the attended (trained) minus the unattended (control) hemifield (i.e., a training-specific improvement), and an overall improvement (i.e., a total change in sensitivity after both sessions). We then identified five visual resting-state networks and evaluated their functional connectivity in relation to both training effects. We found that the functional connectivity strength between the anterior Precuneus and the Occipital Pole Network was positively related to the attention modulated (i.e., training-specific) improvement. No such relationship was found for the overall improvement or for the other visual networks of interest. Our finding suggests that the anterior Precuneus plays a role in training-induced visual field improvements. The resting-state functional connectivity between the anterior Precuneus and the Occipital Pole Network may thus serve as an imaging-based biomarker that quantifies a patients potential capacity to direct spatial attention. This may help to identify hemianopia patients that are most likely to benefit from visual restitution training.

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bioRxiv2020

Foveal pRF properties in the visual cortex depend on the extent of stimulated visual field

Previous studies demonstrated that alterations in functional MRI derived receptive field (pRF) properties in cortical projection zones of retinal lesions can erroneously be mistaken for cortical large-scale reorganization in response to visual system pathologies. We tested, whether such confounds are also evident in the normal cortical projection zone of the fovea for simulated peripheral visual field defects. We applied fMRI-based visual field mapping of the central visual field at 3 Tesla in eight controls to compare the pRF properties of the central visual field of a reference condition (stimulus radius: 14{degrees}) and two conditions with simulated peripheral visual field defect, i.e., with a peripheral gray mask, stimulating only the central 7{degrees} or 4{degrees} radius. We quantified, for the cortical representation of the actually stimulated visual field, the changes in the position and size of the pRFs associated with reduced peripheral stimulation using conventional and advanced pRF modeling. We found foveal pRF-positions ([≤]3{degrees}) to be significantly shifted towards the periphery (p<0.05, corrected). These pRF-shifts were largest for the 4{degrees} condition [visual area (mean eccentricity shift): V1 (0.9{degrees}), V2 (0.9{degrees}), V3 (1.0{degrees})], but also evident for the 7{degrees} condition [V1 (0.5{degrees}), V2 (0.5{degrees}), V3 (0.9{degrees})]. Further, an overall enlargement of pRF-sizes was observed. These findings indicate the dependence of foveal pRF parameters on the spatial extent of the stimulated visual field. Consequently, our results imply that, previously reported similar findings in patients with actual peripheral scotomas need to be interpreted with caution and indicate the need for adequate control conditions in investigations of visual cortex reorganization. HighlightsO_LIFoveal pRF properties change in controls with restricted peripheral stimulation C_LIO_LIpRFs shift in position and enlarge in size for reduced stimulation extent C_LIO_LIAlterations in pRF characteristics in patients should be interpreted with caution C_LIO_LIAdequate control conditions needed in investigations of visual cortex plasticity C_LI

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bioRxiv2019

Predictive masking is associated with a system-wide reconfiguration of neural populations in the human visual cortex

The human visual system masks the perceptual consequences of retinal or cortical lesion-induced scotomas by predicting what is missing from nearby regions of the visual field. To reveal the neural mechanisms underlying this remarkable capacity, known as predictive masking, we used fMRI and neural modeling to track changes in cortical population receptive fields (pRFs) and connectivity in response to the introduction of an artificial scotoma (AS). Consistent with predictive masking, we found that extrastriate areas increased their sampling of the V1 region outside the AS projection zone. Moreover, throughout the visual field and hierarchy, pRFs shifted their preferred position towards the AS border. A gain field model, centered at this border, accounted for these shifts, especially for extrastriate areas. This suggests that a system-wide reconfiguration of neural populations in response to a change in visual input is guided by extrastriate signals and underlies the predictive masking of scotomas.

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bioRxiv2019

Micro-probing enables high-resolution mapping of neuronal subpopulations using fMRI

The characterization of receptive field (RF) properties is fundamental to understanding the neural basis of sensory and cognitive behaviour. The combination of non-invasive imaging, such as fMRI, with biologically inspired neural modeling has enabled the estimation of population RFs directly in humans. However, current approaches require making numerous a priori assumptions, so these cannot reveal unpredicted properties, such as fragmented RFs or subpopulations. This is a critical limitation in studies on adaptation, pathology or reorganization. Here, we introduce micro-probing (MP), a technique for fine-grained and assumption free characterisation of subpopulation RFs. Without specific stimuli or adapted models, MP mapped the bilateral RFs characteristic of observers with a congenital pathway disorder. Moreover, in healthy observers, MP revealed voxels that capture the activity of multiple neuronal subpopulations. Thus, MP provides a versatile framework to visualize, analyze and model, without restrictions, the diverse RFs of cortical subpopulations in health and disease.

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bioRxiv2018

Configural properties underlie the perceived faceness of a stimulus

The global geometrical arrangement of face parts (eyes over nose over mouth), commonly referred to as first order configural (FOC) properties, is believed to constitute a fundamental aspect of face detection. Indeed, several brain regions in the face processing network have been shown to display increased activity in response to abstract stimuli for face-like as compared to random spatial arrangements. However, the absence of a mathematical formalization of FOC properties makes it difficult to systematically study their contribution to face perception. To fill this gap, we used analytical geometry to define a set of 19 FOC features. In two psychophysical studies, a 2-alternative forced choice task assessing difference in perceived faceness between two stimuli and a Likert test assessing measuring perceived faceness of individual stimuli, we evaluated the contribution of each feature to the perceived faceness of abstract stimuli consisting of four black rectangular shapes reflecting the two eyes, the nose and the mouth. From the two experiments two subsets of features relevant for face detection were selected, including 10 and 11 features, respectively. Interestingly, 7 features are shared between the two sets. The difference between the subsets reflects processing of individual FOC features in the first study and holistic processing in the second study. The partial superimposition, on the other hand, is reflective of a shared basic mechanism in the perception of first order configural properties.

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bioRxiv2017

Propagation of BOLD activity reveals directed interactions across human visual cortex

It has recently been shown that large-scale propagation of blood-oxygen level dependent (BOLD) activity is constrained by anatomical connections and reflects transitions between behavioral states. It remains to be seen, however, if the propagation of BOLD activity can also relate to the brain anatomical structure at a more local scale. Here, we hypothesized that BOLD propagation reflects structured neuronal activity across early visual field maps. To explore this hypothesis, we characterize the propagation of BOLD activity across V1, V2 and V3 using a modeling approach that aims to disentangle the contributions of local activity and directed interactions in shaping BOLD propagation. It does so by estimating the effective connectivity (EC) and the excitability of a noise-diffusion network to reproduce the spatiotemporal covariance structure of the data. We apply our approach to 7T fMRI recordings acquired during resting state (RS) and visual field mapping (VFM). Our results reveal different EC interactions and changes in cortical excitability in RS and VFM, and point to a reconfiguration of feedforward and feedback interactions across the visual system. We conclude that the propagation of BOLD activity has functional relevance, as it reveals directed interactions and changes in cortical excitability in a task-dependent manner.

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