Biology subjects

Hendricks, M.

Publications and source records attributed to Hendricks, M..

4 recordsLinked to original sources

bioRxiv2018

Asymmetric adaptation reveals functional lateralization for graded versus discrete stimuli

Abstract 150 wordsAnimal navigation strategies depend on the nature of the environmental cues used. In the nematode Caenorhabditis elegans, navigation has been studied in the context of gradients of attractive or repellent stimuli as well is in response to acute aversive stimuli. We wanted to better understand how sensory responses to the same stimulus vary between graded and acute stimuli, and how this variation relates to behavioral responses. C. elegans has two salt-sensing neurons, ASEL and ASER, that show opposite responses to stepped changes in stimulus levels, however only ASER has been shown to play a prominent role in salt chemotaxis. We used pre-exposure to natural stimuli to manipulate the responsiveness of these neurons and tested their separate contributions to behavior. Our results suggest ASEL is specialized for responses to acute stimulus changes. We also found that ASER remains responsive to graded stimuli under conditions where it is unresponsive to large steps.

neuroscience↗

bioRxiv2018

Environmental programming of adult foraging behavior in C. elegans

Foraging strategies must be tuned to the availability and distribution of resources in the environment. This can occur over generations and lead to genetic differences in foraging behavior, or it can occur on shorter time scales within an individuals life span. Both genetic and experience-based strategies must be implemented by neural circuits that respond to environmental cues and track internal states, and the analysis of such circuits provides insight into the neural basis of complex decision making. In C. elegans, between-strain genetic differences and within-strain plasticity in foraging has been observed. Most individual changes in foraging are short-term, based on experience over several hours. Here, we tested if developmental experience could permanently alter foraging. We found that in wild strains that are normally highly exploratory, early-life starvation leads to \"cautious\" foraging behavior in which exploration is reduced. We characterize the behavioral bases for these strategies and identify changes in the dynamics of a locomotory circuit involved in navigation. Overall, we show that some C. elegans strains exhibit adaptive tuning of their foraging behavior based on early-life experience, and this is associated with changes in a core navigation circuit.

neuroscience↗

bioRxiv2018

A gate-and-switch model for head orientation behaviors in C. elegans

The nervous system seamlessly integrates perception and action. This ability is essential for stable representation of and appropriate responses to the external environment. How the sensorimotor integration underlying this ability occurs at the level of individual neurons is of keen interest. In Caenorhabditis elegans, RIA interneurons receive input from sensory pathways and have reciprocal connections with head motor neurons. Through separate physiological mechanisms, RIA simultaneously encodes both head orientation and sensory stimuli. Based on these observations, we proposed a model for how RIA may integrate these two signals to detect the spatial distribution of stimuli across head sweeps and generate directional head responses. Here, we show that blocking synaptic release from RIA disrupts head orientation behaviors in response to unilaterally presented stimuli. We found that sensory encoding in RIA is gated according to head orientation. This dependence on head orientation is independent of motor encoding in RIA, suggesting a second, posture-dependent pathway upstream of RIA. This gating mechanism may allow RIA to selectively attend to stimuli that are asymmetric across head sweeps. Attractive odor removal during head bends triggers rapid head withdrawal in the opposite direction. Unlike sensory encoding, this directional response is dependent on motor inputs to and synaptic output from RIA. Together, these results suggest that RIA is part of a sensorimotor pathway that is dynamically regulated according to head orientation at two levels: the first is a gate that filters sensory representations in RIA, and the second is a switch that routes RIA synaptic output to dorsal or ventral head motor neurons.

neuroscience↗

bioRxiv2017

Female grant applicants are equally successful when peer reviewers assess the science, but not when they assess the scientist

BackgroundPrevious research shows that men often receive more research funding than women, but does not provide empirical evidence as to why this occurs. In 2014, the Canadian Institutes of Health Research (CIHR) created a natural experiment by dividing all investigator-initiated funding into two new grant programs: one with and one without an explicit review focus on the caliber of the principal investigator.\n\nMethodsWe analyzed application success among 23,918 grant applications from 7,093 unique principal investigators in a 5-year natural experiment across all investigator-initiated CIHR grant programs in 2011-2016. We used Generalized Estimating Equations to account for multiple applications by the same applicant and an interaction term between each principal investigators self-reported sex and grant programs to compare success rates between male and female applicants under different review criteria.\n\nResultsThe overall grant success rate across all competitions was 15.8%. After adjusting for age and research domain, the predicted probability of funding success in traditional programs was 0.9 percentage points higher for male than for female principal investigators (OR 0.934, 95% CI 0.854-1.022). In the new program focused on the proposed science, the gap was 0.9 percentage points in favour of male principal investigators (OR 0.998, 95% CI 0.794-1.229). In the new program with an explicit review focus on the caliber of the principal investigator, the gap was 4.0 percentage points in favour of male principal investigators (OR 0.705, 95% CI 0.519- 0.960).\n\nInterpretationThis study suggests gender gaps in grant funding are attributable to less favourable assessments of women as principal investigators, not differences in assessments of the quality of science led by women. We propose ways for funders to avoid allowing gender bias to influence research funding.\n\nFundingThis study was unfunded.

scientific communication and education↗