MRI- and histologically derived neuroanatomical atlas of the Ambystoma mexicanum (axolotl).

Amphibians are an important vertebrate model system to understand anatomy, genetics and physiology. Importantly, the brain and spinal cord of adult urodels (salamanders) have an incredible regeneration capacity, contrary to anurans (frogs) and the rest of adult vertebrates. Among these amphibians, the axolotl (Ambystoma mexicanum) has gained most attention because of the surge in the understanding of central nervous system (CNS) regeneration and the recent sequencing of its whole genome. However, a complete comprehension of the brain anatomy is not available. In the present study we created a magnetic resonance imaging (MRI) atlas of the in vivo neuroanatomy of the juvenile axolotl brain. This is the first MRI atlas for this species and includes three levels: (1) 82 regions of interest (ROIs) and a version with 64 ROIs; (2) a division of the brain according to the embryological origin of the neural tube, and (3) left and right hemispheres. Additionally, we localized the myelin rich regions of the juvenile brain. The atlas, the template that the atlas was derived from, and a masking file, can be found on Zenodo at https://doi.org/10.5281/zenodo.4595016 . This MRI brain atlas aims to be an important tool for future research of the axolotl brain and that of other amphibians.

Sensory and memory processing in old female and male Wistar rat brain, and its relationship with the cortical and hippocampal redox state.

The brain is one of the most sensitive organs damaged during aging due to its susceptibility to the aging-related oxidative stress. Hence, in this study, the sensory nerve pathway integrity and the memory were evaluated and related to the redox state, the antioxidant enzymes function, and the protein oxidative damage in the brain cortex (Cx) and the hippocampus (Hc) of young (4-month-old) and old (24-month-old) male and female Wistar rats. Evoked potentials (EP) were performed for the auditory, visual, and somatosensory pathways. In both males and females, the old rat groups' latencies were larger in almost all waves when compared to the young same-sex animals. The novel object test was performed to evaluate memory. The superoxide dismutase and catalase antioxidant activity, as well as the protein oxidative damage, and the redox state were evaluated. Magnetic resonance (MR) imaging was used to obtain the diffusion tensor imaging, and the brain volume, while MR spectroscopy was used to obtain the brain metabolite concentrations (glutamine, glutamate, Myo-inositol, N-acetyl-aspartate, creatine) in the Cx and the Hc of young and old females. Our data suggest that, although there are limited variations regarding memory and nerve conduction velocity by sex, the differences concerning the redox status might be important to explain the dissimilar reactions during brain aging between males and females. Moreover, the increment in Myo-inositol levels in the Hc of old rats and the brain volume decrease suggest that redox state alterations might be correlated to neuroinflammation during brain aging.

[Dissociated deviation. A strabismus of cortical origin]. / Desviación disociada. Estrabismo de origen cortical.

BACKGROUND: We undertook this study to determine the cortical alterations related to the origin of dissociated deviation. METHODS: This was a prospective, descriptive and observational study that included 10 children with diagnosis of dissociated horizontal deviation, without previous evidence of neuronal damage. Manual, cerebral and ocular dominance were determined, as well as sensorial state and visual perceptual profile. Cortical response to different stimuli was analyzed: luminous, hyperventilation, slow and saccadic movements of pursuit, gaze and stare through cerebral mapping and neurometric EEG. The biochemical composition to the visual cortex by means of magnetic resonance spectroscopy was also investigated. RESULTS: The following alterations were demonstrated: a) neuroelectric: dysynchronic, paroxysms and/or lentification; b) neurometabolic: elevation of lactate, decrease of N-acetylaspartate and loss of the creatine/choline relationship; c) sensorial: suppression and amblyopia; d) perceptual vision: under-yield in visual abilities; e) motor: horizontal and vertical dissociated deviation; f) optometric: hyperopic astigmatism. CONCLUSIONS: The study suggests that dissociated deviation has a cortical origin and is related to epileptogenic disease.