Biology subjects

Evans, M. L.

Publications and source records attributed to Evans, M. L..

3 recordsLinked to original sources

bioRxiv2024

Adult oligodendrogenesis gates arcuate neuronal glucose sensing through remodelling of the blood-hypothalamus barrier via ADAMTS4

Brain glucose sensing is critical for survival during hypoglycaemia and tunes the level of defended blood glucose, which goes up in diabetes. Neuronal glucose sensing neurons and mechanisms have been identified, but how these neurons access blood concentrations of glucose to adjust their output and maintain glucose homeostasis is unclear. Here, we demonstrate that adult oligodendrogenesis in the median eminence (ME) is modulated by changes in circulating glucose levels and rapidly upregulated by hypoglycaemia. We show that genetic blockade of new OL production in adult mice impairs the regulation of glucose homeostasis, the integrity of the ME blood-hypothalamus barrier, and neuronal glucose sensing in the arcuate nucleus of the hypothalamus (ARH). Unexpectedly, functional integrity of adult-formed myelin is not required for the maintenance of glucose homeostasis. Instead, newly formed OLs exert their glucoregulatory actions via the synthesis of A disintegrin and metallopeptidase with thrombospondin motifs 4 (ADAMTS4), a metallopeptidase expressed exclusively by OLs and dependent on adult OL genesis to maintain its expression in the ME. Both lack of Adamts4 and ADAMTS4 gain-of-function are associated with impaired glucose homeostasis and remodelling of the blood-hypothalamus barrier, indicating that optimal ADAMTS4 expression is required for the integrity of vascular permeability and normal glycaemic control. Finally, we show that ME ADAMTS4 expression is regulated by changes in peripheral glycaemia and is dysregulated in diabetes, providing a mechanism by which ME OLs contribute to the regulation of glucose homeostasis.

neuroscience↗

bioRxiv2022

Exploring the potential of using simulation games for engaging with sheep farmers about lameness recognition

IntroductionComputer simulation games are increasingly being used in agriculture as a promising tool to study, support and influence real-life farming practices. We explored the potential of using simulation games to engage with sheep farmers on the ongoing challenge of reducing lameness. Working with UK stakeholders, we developed a game in which players are challenged with identifying all the lame sheep in a simulated flock. Here, we evaluate the games potential to act as a tool for to help assess, train and understand farmers ability to recognise the early signs of lameness. MethodsParticipants in the UK were invited to play the game in an online study, sharing with us their in-game scores alongside information relating to their real-life farming experience, how they played the game, and feedback on the game. Mixed methods were used to analyse this information in order to evaluate the game. Quantitative analyses consisted of linear modelling to test for statistical relationships between participants in-game recall (% of the total number of lame sheep that were marked as lame), and the additional information they provided. Qualitative analyses of participants feedback on the game consisted of thematic analysis and a Likert Scale questionnaire to contextualise the quantitative results and identify additional insights from the study. ResultsQuantitative analyses identified no relationships between participants (n = 63) recall scores and their real life farming experience, or the lameness signs they looked for when playing the game. The only relationship identified was a relationship between participants recall score and time spent playing the game. Qualitative analyses identified that participants did not find the game sufficiently realistic or engaging, though several enjoyed playing it and saw potential for future development. Qualitative analyses also identified several interesting and less-expected insights about real-life lameness recognition practices that participants shared after playing the game. DiscussionSimulation games have potential as a tool in livestock husbandry education and research, but achieving the desired levels of realism and/or engagingness may be an obstacle to realising this. Future research should explore this potential further, aided by larger budgets and closer collaboration with farmers, stockpeople and veterinarians.

scientific communication and education↗

bioRxiv2021

Dynamics of absolute and relative disparity processing in human visual cortex

Cortical processing of binocular disparity is believed to begin in V1 where cells are sensitive to absolute disparity, followed by the extraction of relative disparity in higher visual areas. While much is known about the cortical distribution and spatial tuning of disparity-selective neurons, the relationship between their spatial and temporal properties is less well understood. Here, we use steady-state Visual Evoked Potentials and dynamic random dot stereograms to characterize the temporal dynamics of spatial mechanisms in human visual cortex that are primarily sensitive to either absolute or relative disparity. Stereograms alternated between disparate and non-disparate states at 2 Hz. By varying the spatial frequency content of the disparate fields from a planar surface to corrugated ones, we biased responses towards absolute vs. relative disparities. Reliable Components Analysis was used to derive two dominant sources from the 128 channel EEG records. The first component (RC1) was maximal over the occipital pole while the second component (RC2) was maximal over right lateral occipital electrodes. In RC1, first harmonic responses were sustained, tuned for corrugation frequency, and sensitive to the presence of disparity references, consistent with prior psychophysical sensitivity measurements. By contrast, the second harmonic, associated with transient processing, was not spatially tuned and was indifferent to references, consistent with it being generated by an absolute disparity mechanism. In RC2, the sustained response component showed similar tuning and sensitivity to references. However, sensitivity for absolute disparity dropped off, and transient signals were mainly driven by the lowest corrugation frequencies. SIGNIFICANCE STATEMENTSustained and transient mechanisms have been demonstrated across sensory systems and may reflect a common coding strategy. This strategy may be useful for the analysis of the form and duration of complex events in the case of sustained signals, and the onset and location of events in the case of transient signals. Here, we provide direct neural correlates of sustained and transient disparity mechanisms in human visual cortex. Early visual cortex is sensitive to both relative and absolute disparity, with the former being processed in a sustained fashion and the latter in a more transient fashion. Outside of early visual cortex, sustained relative disparity responses are readily measurable, but transient responses and responses to absolute disparity are not.

neuroscience↗