Saville, A. | bioRxiv Science

bioRxiv2020

Global historic pandemics caused by the FAM-1 genotype of the Irish potato pathogen Phytophthora infestans

The FAM-1 genotype of Phytophthora infestans caused late blight in the 1840s in the US and Europe and was responsible for the Irish famine. We examined 140 herbarium specimens collected between 1845 and 1991 from six continents and used 12-plex microsatellite genotyping (SSR) to identify FAM-1 and the mtDNA lineage (Herb-1/ Ia) present in historic samples. FAM-1 was detected in approximately 73% of the historic specimens and was found on 6 continents. The US-1 genotype was found in only 27% of the samples and was found later on all continents except Australia/Oceania. FAM-1 was the first genotype detected in almost all the former British colonies from which samples were available. The data from historic samples suggest the FAM-1 genotype was widespread, diverse, and spread more widely than US-1. The famine lineage spread to six continents over 140 years, and likely spread during global colonization from Europe.

evolutionary biology↗

bioRxiv2020

Neural Sensitivity to Natural Image Statistics Changes during Middle Childhood

Natural images have lawful statistical properties that the adult visual system is sensitive to, both in terms of behavior and neural responses to natural images. The developmental trajectory of sensitivity to natural image statistics remains unclear, however. In behavioral tasks, children appear to slowly acquire adult-like sensitivity to natural image statistics during middle childhood (Ellemberg et al., 2012), but in other tasks, infants exhibit some sensitivity to deviations of natural image structure (Balas & Woods, 2014). Here, we used event-related potentials (ERPs) to examine how sensitivity to natural image statistics changes during childhood at distinct stages of visual processing (the P1 and N1 components). We asked children (5-10 years old) and adults to view natural texture images with either positive/negative contrast, and natural/synthetic texture appearance (Portilla & Simoncelli, 2000) to compare electrophysiological responses to images that did or did not violate natural statistics. We hypothesized that children may only acquire sensitivity to these deviations from natural texture appearance late in middle childhood. Counter to this hypothesis, we observed significant responses to unnatural contrast and texture statistics at the N1 in all age groups. At the P1, however, only young children exhibited sensitivity to contrast polarity. The latter effect suggests greater sensitivity earlier in development to some violations of natural image statistics. We discuss these results in terms of changing patterns of invariant texture processing during middle childhood and ongoing refinement of the representations supporting natural image perception.

neuroscience↗