Biology subjects

Grijseels, D. M.

Publications and source records attributed to Grijseels, D. M..

5 recordsLinked to original sources

bioRxiv2026

Current state of bioacoustics research of vocal repertoires

Knowledge of the unique call types produced by a species has historically been an important part of ecological research. However, the definition of a call type is not straightforward, and across species and studies different methods are employed to study call types and vocal repertories. Here, we analysed the methodology used to identify the vocal repertoires of 197 mammalian species across 220 studies. We found a large variability in the features extract from individual calls, methods to analyse spectrographic features, and methods to cluster call types. We further see a low uptake of novel methods for acoustic analysis and clustering. Lastly, we identify a lack of open data across the included studies, with less than 2% of studies providing the raw audio dataset underlying their paper. Based on these results, we call for increased standardization of methods and data transparency across the field.

animal behavior and cognition↗

bioRxiv2021

APOE4 genotype increases neuronal calcium signals and decreases pial arteriole responsivity and vasomotion in visual cortex of awake mice

Young mice possessing the e4 allele of the Apolipoprotein (APOE) gene (a risk factor for Alzheimers disease (AD)) have previously been shown to have dramatic decreases in vascular function, suggesting APOE4 may confer its risk via the vasculature. However, in human carriers, vascular and cognitive function decrease later in life. Mouse data may be confounded by an increased impact of anaesthesia and surgery in APOE4 animals, and has also focused on sensory cortices, ignoring medial lobe structures more sensitive to AD. To clarify how APOE4 expression alters neurovascular function, we studied the visual cortex and hippocampus of awake APOE3 and APOE4 targeted replacement mice, using 2-photon microscopy of neurons and blood vessels. We found milder vascular deficits than studies using anaesthetised preparations: functional hyperaemia was unaffected in APOE4 mice and neuronal or vascular function did not decrease with age. Instead, vascular responsiveness was lower at all ages, arteriole vasomotion was reduced and neuronal calcium signals during visual stimulation were increased. This suggests that, independently, APOE4 expression is not catastrophic but alters neurovascular physiology towards a state more sensitive to insults such as surgery or beta amyloid accumulation. Understanding how APOE4 expression interacts with these insults will be critical for understanding the emergence of AD in APOE4 carriers.

neuroscience↗

bioRxiv2021

Choice of method of place cell classification determines the population of cells identified.

Place cells, spatially responsive hippocampal cells, provide the neural substrate supporting navigation and spatial memory. Historically most studies of these neurons have used electrophysiological recordings from implanted electrodes but optical methods, measuring intracellular calcium, are becoming increasingly common. Several methods have been proposed as a means to identify place cells based on their calcium activity but there is no common standard and it is unclear how reliable different approaches are. Here we tested three methods that have previously been applied to two-photon hippocampal imaging or electrophysiological data, using both model datasets and real imaging data. These methods use different parameters to identify place cells, including the peak activity in the place field, compared to other locations (the Peak method); the stability of cells activity over repeated traversals of an environment (Stability method); and a combination of these parameters with the size of the place field (Combination method). The three methods performed differently from each other on both model and real data. The Peak method showed high sensitivity and specificity for detecting model place cells and was the most robust to variations in place field width, reliability and field location. In real datasets, vastly different numbers of place cells were identified using the three methods, with little overlap between the populations identified as place cells. Therefore, choice of place cell detection method dramatically affects the number and properties of identified cells. We recommend the Peak method be used in future studies to identify place cell populations, unless there is an explicit theoretical reason for detecting cells with more narrowly defined properties. Author SummaryPlace cells are hippocampal cells that have spatially constrained receptive fields, the place field. These cells have been widely studied in the context of navigation, more recently using virtual reality environments in combination with optical methods of recording neuronal activity. However, there is a lack of consensus regarding how to identify place cells in these data. In this study we tested the sensitivity and specificity of three methods of identifying place cells. By comparing these methods and quantifying the populations of place cells they identify, we aimed to increase our understanding of exactly the populations that are currently being studied under the name "place cells". Although the appropriate method may depend on the experimental design, we generally recommend a single method going forward, which will increase consensus within the field about what should be included in a place cell population, and allow us to better compare results between studies.

neuroscience↗

bioRxiv2019

Hippocampus has lower oxygenation and weaker control of brain blood flow than cortex, due to microvascular differences

The hippocampus is essential for spatial and episodic memory but is damaged early in Alzheimers disease and is very sensitive to hypoxia. Understanding how it regulates its oxygen supply is therefore key for designing interventions to preserve its function. However, studies of neurovascular function in the hippocampus in vivo have been limited by its relative inaccessibility. Here we compared hippocampal and visual cortical neurovascular function in awake mice, using two photon imaging of individual neurons and vessels and measures of regional blood flow and haemoglobin oxygenation. We show that blood flow, blood oxygenation and neurovascular coupling were decreased in the hippocampus compared to neocortex, because of differences in both the vascular network and pericyte and endothelial cell function. Modelling oxygen diffusion indicates that these features of the hippocampal vasculature could explain its sensitivity to damage during neurological conditions, including Alzheimers disease, where the brains energy supply is decreased.

neuroscience↗

bioRxiv2018

Spikeling: a low-cost hardware implementation of a spiking neuron for neuroscience teaching and outreach.

Understanding of how neurons encode and compute information is fundamental to our study of the brain, but opportunities for hands-on experience with neurophysiological techniques on live neurons are scarce in science education. Here, we present Spikeling, an open source {pound}25 in silico implementation of a spiking neuron that mimics a wide range of neuronal behaviours for classroom education and public neuroscience outreach. Spikeling is based on an Arduino microcontroller running the computationally efficient Izhikevich model of a spiking neuron. The microcontroller is connected to input ports that simulate synaptic excitation or inhibition, dials controlling current injection and noise levels, a photodiode that makes Spikeling light-sensitive and an LED and speaker that allows spikes to be seen and heard. Output ports provide access to variables such as membrane potential for recording in experiments or digital signals that can be used to excite other connected Spikelings. These features allow for the intuitive exploration of the function of neurons and networks. We also report our experience of using Spikeling as a teaching tool for undergraduate and graduate neuroscience education in Nigeria and the UK.

scientific communication and education↗