Biology subjects

ffytche, D.

Publications and source records attributed to ffytche, D..

4 recordsLinked to original sources

bioRxiv2023

Neural patterns of conscious visual awareness in the Riddoch syndrome

The Riddoch syndrome is one in which patients blinded by lesions to their primary visual cortex can consciously perceive visual motion in their blind field, an ability that correlates with activity in motion area V5. Our assessment of the characteristics of this syndrome in patient ST, using multimodal MRI, showed that: 1. STs V5 is intact, receives direct subcortical input, and decodable neural patterns emerge in it only during the conscious perception of visual motion; 2. moving stimuli activate medial visual areas but, unless associated with decodable V5 activity, they remain unperceived; 3. STs high confidence ratings when discriminating motion at chance levels, is associated with inferior frontal gyrus activity. Finally, we report that STs Riddoch Syndrome results in hallucinatory motion with hippocampal activity as a correlate. Our results shed new light on perceptual experiences associated with this syndrome and on the neural determinants of conscious visual experience.

neuroscience↗

bioRxiv2022

Neuroanatomical substrates in Parkinson's Disease psychosis and their association with serotonergic receptor gene expression: A coordinate-based meta-regression analysis.

BackgroundCommon neural underpinning of Parkinsons Disease (PD) psychosis across different structural magnetic resonance imaging (MRI) studies remains unclear to this day with few studies and even fewer meta-analyses available. ObjectivesOur meta-analysis aimed to identify and summarise studies using MRI approach to identify PD psychosis-specific brain regions and examine the relation between cortical volume loss and dopaminergic and serotonergic receptor density. MethodsPubMed, Web of Science and Embase were searched for MRI studies of PD psychosis (PDP) compared to PD patients without psychosis (PDnP). Seed-based d Mapping with Permutation of Subject Images was applied in the meta-analysis where coordinates were available. Multiple linear regressions to examine the relationship between grey matter volume loss in PDP and receptor gene expression density (extracted from the Allen Human Brain Atlas) were conducted in R. ResultsWe observed lower grey matter volume in parietal-temporo-occipital regions from our meta-analysis (N studies =10, PDP n=211, PDnP, n=298). These results remained significant after adjusting for PD medications and for cognitive scores. Grey matter volume loss in PDP was associated with local expression of 5-HT1a (b=0.109, p=0.012) and 5-HT2a receptors (b=-0.106, p=0.002) also after adjusting for PD medications (5-HT1a, p = 0.005; 5-HT2a, p = 0.001). ConclusionsWidespread cortical volume loss in the parieto-temporo-occipital regions involved in information processing and integration, as well as attention, could result in PD psychosis symptoms. Neurobiological mechanisms implicating serotonergic receptors may also contribute to this condition.

neuroscience↗

bioRxiv2021

Neurons derived from individual early Alzheimer's disease patients reflect clinical vulnerability

Establishing preclinical models of Alzheimers disease that predict clinical outcomes remains a critically important, yet to date not fully realised, goal. Models derived from human cells offer considerable advantages over non-human models, including the potential to reflect some of the inter-individual differences that are apparent in patients. Here we report an approach using induced pluripotent stem cell-derived cortical neurons from people with early symptomatic Alzheimers disease where we sought a match between individual disease characteristics in cells with analogous characteristics in the people from whom they were derived. We show that the response to amyloid-{beta} burden in life, as measured by cognitive decline and brain activity levels, varies between individuals and this vulnerability rating correlates with the individual cellular vulnerability to extrinsic amyloid-{beta} in vitro as measured by synapse loss and function. Our findings indicate that patient induced pluripotent stem cell-derived cortical neurons not only present key aspects of Alzheimers disease pathology, but also reflect key aspects of the clinical phenotypes of the same patients. Cellular models that reflect an individuals in-life clinical vulnerability thus represent a tractable method of Alzheimers disease modelling using clinical data in combination with cellular phenotypes.

neuroscience↗

bioRxiv2021

The missing pathway in current visuospatial processing models

Visuospatial learning depends on the parahippocampal place area (PPA), a functionally heterogenous area which current visuospatial processing models place downstream from parietal cortex and only from area V4 of early visual cortex (EVC). However, evidence for anatomical connections between the PPA and other EVC areas is inconsistent, and these connections are not discussed in current models. Through a data-driven analysis based on diffusion MRI tractography, we present evidence that the PPA sits at the confluence of two white matter systems. The first conveys information from the retrosplenial complex to the anterior PPA and runs within the cingulum bundle. The second system connects all peripheral EVC areas to the posterior PPA and corresponds to the medial occipital longitudinal tract (MOLT), a novel white matter pathway distinct from the cingulum. Based on further functional connectivity analysis and meta-analytic data, we propose that the MOLT supports early stage encoding of visuospatial information by allowing direct reciprocal exchange between the PPA and EVC.

neuroscience↗