Johnson, S. B. | Search bioRxiv

bioRxiv2024

A tale of two shrimps - Speciation and demography of two sympatric shrimp species from hydrothermal vents

Hydrothermal vents can serve as natural laboratories to study speciation processes due to their fragmented distribution often with geographic barriers between habitats. Two sympatric species of Rimicaris shrimps occur at vents on the Izu-Bonin-Mariana volcanic arc: Rimicaris loihi also occurs near Hawaii and R. cambonae is present on the Tonga Arc. These two species biogeographically co-occur and are genetically similar, raising questions about their speciation mechanism, how they maintain distinct species, and whether interbreeding occurs. Here, we use barcoding and shotgun sequencing to test their genetic isolation and investigate their speciation process. We also evaluate population demography over 10 years to assess population densities and sex ratios at vents. Our results support R. cambonae and R. loihi as two distinct species despite sympatry throughout part of their range. We also observed regional-scale genetic structure among R. loihi populations from the Izu-Bonin-Mariana volcanic arc despite their broad geographic distribution. Finally, we found concomitant variations of shrimp densities and genetic diversity following fluctuations in geological and venting activities over a decade. A combination of geological instability, ocean currents dynamics and sea-level changes might drive temporary isolation among these local populations. We suggest similar factors, with longer isolation periods, may also have promoted speciation between the two Rimicaris species whereas distinct life-history traits could strengthen and maintain reproductive barriers. Overall, our results indicate different connectivity patterns on a volcanic arc that contrast with those observed previously at vents from mid-ocean ridges or back-arc basins systems.

evolutionary biology↗

bioRxiv2024

Natural Language Processing Applied to Spontaneous Recall of Famous Faces Reveals Memory Dysfunction in Temporal Lobe Epilepsy Patients

Objective and BackgroundEpilepsy patients rank memory problems as their most significant cognitive comorbidity. Current clinical assessments are laborious to administer and score and may not always detect subtle memory decline. The Famous Faces Task (FF) has robustly demonstrated that left temporal lobe epilepsy (LTLE) patients remember fewer names and biographical details compared to right TLE (RTLE) patients and healthy controls (HCs). We adapted the FF task to capture subjects entire spontaneous spoken recall, then scored responses using manual and natural language processing (NLP) methods. We expected to replicate previous group level differences using spontaneous speech and semi-automated analysis. MethodsSeventy-three (N=73) adults (28 LTLE, 18 RTLE, and 27 HCs) were included in a case-control prospective study design. Twenty FF in politics, sports, and entertainment (active 2008-2017) were shown to subjects, who were asked if they could recognize and spontaneously recall as much biographical detail as possible. We created human-generated and automatically-generated keyword dictionaries for each celebrity, based on a randomly selected training set of half of the HC transcripts. To control for speech output, we measured the speech duration, total word count and content word count for the FF task and a Cookie Theft Control Task (CTT), in which subjects were merely asked to describe a visual scene. Subjects responses to FF and CTT tasks were recorded, transcribed, and analyzed in a blinded manner with a combination of manual and automated NLP approaches. ResultsFamous face recognition accuracy was similar between groups. LTLE patients recalled fewer biographical details compared to HCs and RTLEs using both the gold-standard human-generated dictionary (24%{+/-}12% vs. 31%{+/-}12% and 30%{+/-}12%, p=0.007) and the automated dictionary (24%{+/-}12% vs. 31%{+/-}12% and 32%{+/-}13%, p=0.007). There were no group level differences in speech duration, total word count, or content word count for either the FF and CTT to explain difference in recall performance. There was a positive, statistically significant relationship between MOCA score and FF recall performance as scored by the human-generated ({rho}= .327, p= .029) and automatically-generated dictionaries ({rho}= .422, p= .004) for TLE subjects, but not HCs, an effect that was driven by LTLE subjects. DiscussionLTLE patients remember fewer details of famous people than HCs or RTLE patients, as discovered by NLP analysis of spontaneous recall. Decreased biographical memory was not due to decreased speech output and correlated with lower MOCA scores. NLP analysis of spontaneous recall can detect memory dysfunction in clinical populations in a semi-automated, objective, and sensitive manner.

neuroscience↗