Biology subjects

Parra, C.

Publications and source records attributed to Parra, C..

3 recordsLinked to original sources

bioRxiv2022

GABA decrease is associated with degraded neural specificity in the visual cortex of glaucoma patients

Glaucoma is an age-related neurodegenerative disease of the visual system, affecting both the eye and the brain. Yet its underlying metabolic mechanisms and neurobehavioral relevance remain largely unclear. Here, using proton magnetic resonance spectroscopy and functional magnetic resonance imaging, we investigated the GABAergic and glutamatergic systems in the visual cortex of glaucoma patients, as well as neural specificity, which is shaped by GABA and glutamate signals and underlies efficient sensory and cognitive functions. Our study showed that among the older adults, both GABA and glutamate levels decrease with increasing glaucoma severity regardless of age. Further, the reduction of GABA but not glutamate predicted the neural specificity. This association was independent of the impairments on the retina structure and age. Our results suggest that glaucoma-specific decline of GABA undermines neural specificity in the visual cortex and that targeting GABA could improve the neural specificity in glaucoma.

neuroscience↗

bioRxiv2022

Automatic identification of intestinal parasites in reptiles using microscopic stool images and convolutional neural networks

Captive environments trigger the propagation and multiplication of parasites among different reptile species, thus weakening their immune response and causing infections and diseases. Technological advances of convolutional neural networks have opened a new field for detecting and classifying diseases which have shown great potential to overcome the shortcomings of manual detection performed by experts. Therefore, we propose an approach to identify six captive reptiles parasitic agents (Ophionyssus natricis, Blastocystis sp, Oxiurdo egg, Rhytidoides similis, Strongyloides, Taenia) from a microscope stool images dataset. Towards this end, we first use an image segmentation stage to detect the parasite within the image, which combines the Contrast Limited Adaptive Histogram Equalization (CLAHE) technique, the OTSU binarization method, and morphological operations. Then, we carry out a classification stage through Mobilenet CNN under a transfer learning scheme. This method was validated on a stool image dataset containing 3616 images data samples and 26 videos from the six parasites mentioned above. The results obtained indicate that our transfer learning-based approach can learn a helpful representation from the dataset. We obtained an average accuracy of 98.66% across the six parasitic agent classes, which statistically outperformed, at a 95% confidence level, a custom CNN trained from scratch.

zoology↗

bioRxiv2021

Global and network functional connectivity of nucleus basalis of Meynert is strengthened in blind individuals

Plasticity in the brain is differentially affected by age of blindness onset. One possible, but not yet identified mechanism is that the cholinergic signals originating from the nucleus basalis of Meynert may underlie differential extent of plasticity in early and late blind individuals. This prospect is based on the fact that the nucleus basalis of Meynert modulates cortical processes such as plasticity and sensory encoding and that the degree of cross-modal plasticity varies depending on the age of blindness onset. However, this question yet remains largely unclear. Here, we tested whether the early and late blind individuals develop dissociable plasticity in the nucleus basalis of Meynert using multi-parametric magnetic resonance imaging. We found the relatively preserved volumetric size and cerebrovascular reactivity, but significant disruption in the white matter integrity of the nucleus basalis of Meynert in both early and late blind individuals. Critically, despite its reduction in the white matter integrity, the nucleus basalis of Meynert of early blind individuals presented greater global and network functional connectivity including visual, language, and default-mode networks. Such changes in the functional connectivity were not observed in the late-blind individuals. Further, less duration of the visual experience was associated with greater global and network functional connectivity. These results indicate that the nucleus basalis of Meynert is differentially involved in the plasticity of early and late blind individuals - a similar amount of reduction in microstructural integrity in early and late blind individuals, but stronger and more widespread functional connectivity of the NBM in the early blind individuals. Our findings suggest that the nucleus basalis of Meynert may develop greater cholinergic influence on the cortex of early blind individuals. Such change may explain why early blind individuals present stronger and more widespread cross-modal plasticity during non-visual tasks compared to late blind individuals.

neuroscience↗