Abnormal eye movements reflect early cortical and volumetric brain changes in apparently healthy, PM _2.5 -exposed urban youth

Background Eye movement dysfunction plays an important role in understanding the pathology of neurodegenerative disorders. Fine particulate matter (PM 2.5 ) exposures are associated with hallmark proteins diagnostic of Alzheimer's and Parkinson's diseases in Metropolitan Mexico City (MMC) ≤ 40-year-old residents. Objective To assess oculomotor function with neuroanatomical correlates using magnetic resonance imaging (MRI) region of interest analysis in young urbanites. Methods Video-based eye-tracking was used to explore oculomotor dysfunction and structural brain MRI changes in two highly exposed PM 2.5 cohorts. We assessed fixation stability, smooth pursuit, pro-saccades, and anti-saccades using the Eyelink 1000-plus eye-tracker, in 80 volunteers’ age 33 ± 11 years from MMC and Cuernavaca. Forty-five MMC subjects age 31.2 ± 14.7 years with oculomotor assessment had brain MRIs. Measurements of saccadic accuracy, latency, and smooth pursuit gain and square wave jerk frequency were collected. Results Oculomotor variables did not reach statistically significant differences in MMC versus Cuernavaca. Abnormal antisaccades, low gain pursuit, and square wave jerks were documented more often in MMC residents. Correlational analysis between oculomotor function and structural MRI data revealed statistical cortical and subcortical changes at frontal-temporal-parietal regions, hippocampus, thalamus, caudate, amygdala, habenula, nucleus accumbens, and cerebellum. Involved regions potentially reveal the location and severity of neurodegeneration processes via altered saccade parameters. Conclusions Our findings suggest that simple oculomotor test batteries may provide a useful tool to monitor and/or measure the impact of pollution on neurodevelopment and early neurodegeneration. The integration of ocular movement parameters into the Continuum model of neurodegeneration offers a promising approach for neuroprotection decision-making and rigorous emissions control in polluted settings.