Search

BackgroundPrevious epidemiological studies have reported associations of pesticide exposure with poor cognitive function and behavioral problems. However, these findings have relied primarily on neuropsychological assessments. Questions remain about the neurobiological effects of pesticide exposure, specifically where in the brain pesticides exert their effects and whether compensatory mechanisms in the brain may have masked pesticide-related associations in studies that relied purely on neuropsychological measures.MethodsWe conducted a functional neuroimaging study in 48 farmworkers from Zarcero County, Costa Rica, in 2016. We measured concentrations of 13 insecticide, fungicide, or herbicide metabolites or parent compounds in urine samples collected during two study visits (approximately 3-5 weeks apart). We assessed cortical brain activation in the prefrontal cortex during tasks of working memory, attention, and cognitive flexibility using functional near-infrared spectroscopy (fNIRS). We estimated associations of pesticide exposure with cortical brain activation using multivariable linear regression models adjusted for age and education level.ResultsWe found that higher concentrations of insecticide metabolites were associated with reduced activation in the prefrontal cortex during a working memory task. For example, 3,5,6-trichloro-2-pyridinol (TCPy; a metabolite of the organophosphate chlorpyrifos) was associated with reduced activation in the left dorsolateral prefrontal cortex (β = -2.3; 95% CI: -3.9, -0.7 per two-fold increase in TCPy). Similarly, 3-phenoxybenzoic acid (3-PBA; a metabolite of pyrethroid insecticides) was associated with bilateral reduced activation in the dorsolateral prefrontal cortices (β = -3.1; 95% CI: -5.0, -1.2 and -2.3; 95% CI: -4.5, -0.2 per two-fold increase in 3-PBA for left and right cortices, respectively). These associations were similar, though weaker, for the attention and cognitive flexibility tasks. We observed null associations of fungicide and herbicide biomarker concentrations with cortical brain activation during the three tasks that were administered.ConclusionOur findings suggest that organophosphate and pyrethroid insecticides may impact cortical brain activation in the prefrontal cortex - neural dynamics that could potentially underlie previously reported associations with cognitive and behavioral function. Furthermore, our study demonstrates the feasibility and utility of fNIRS in epidemiological field studies.

An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field-aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (

Relative age effects (RAEs) are independent of specific cutoff dates that can vary from country to country. However, the consequences of changing the selection cutoff dates within a national sport organization are unknown. Further, the transition from international youth to senior representation is yet to be explored in rugby union. Thus, the aims of this article were twofold: "Study 1" compared the birth quarter (BQ) distributions of the England Rugby Football Union (RFU) under-18 representatives based on September to August and January to December selection cutoff dates. "Study 2" explored the BQ distributions within the RFU international development pathway through analyzing the under-18, under-20, and senior representatives, as well as the BQ distributions of youth players who were subsequently capped at senior level. Chi-square analysis was used to compare BQ distributions in each sample against expected distributions. Results revealed a corresponding shift of a skewed birthdate distribution favoring chronologically older players that was mediated by specific cutoff dates (p < 0.05). Moreover, whilst RAEs were present within both youth cohorts (p < 0.05), it was not apparent at the senior level (p > 0.05). Furthermore, during the transition from international youth to senior representation, more chronologically older players were successfully capped.