Biology subjects

Wildenberg, G. A.

Publications and source records attributed to Wildenberg, G. A..

5 recordsLinked to original sources

bioRxiv2023

Synchrotron-source micro-x-ray computed tomography for examining butterfly eyes

1. Comparative anatomy is an important tool for investigating evolutionary relationships amongst species, but the lack of scalable imaging tools and stains for rapidly mapping the microscale anatomies of related species poses a major impediment to using comparative anatomy approaches for identifying evolutionary adaptations. 2. We describe a method using synchrotron source micro-x-ray computed tomography (syn-{micro}XCT) combined with machine learning algorithms for high-throughput imaging of Lepidoptera (i.e., butterfly and moth) eyes. Our pipeline allows for imaging at rates of [~] 15 min/mm3 at 600 nm3 resolution. Image contrast is generated using standard electron microscopy labeling approaches (e.g., osmium tetroxide) that unbiasedly labels all cellular membranes in a species independent manner thus removing any barrier to imaging any species of interest. 3. To demonstrate the power of the method, we analyzed the 3D morphologies of butterfly crystalline cones, a part of the visual system associated with acuity and sensitivity and found significant variation within six butterfly individuals. Despite this variation, a classic measure of optimization, the ratio of interommatidial angle to resolving power of ommatidia, largely agrees with early work on eye geometry across species. 4. We show that this method can successfully be used to determine compound eye organization and crystalline cone morphology. Our novel pipeline provides for fast, scalable visualization and analysis of eye anatomies that can be applied to any arthropod species, enabling new questions about evolutionary adaptations of compound eyes and beyond.

ecology↗

bioRxiv2023

A Pipeline for a Primate Projectome: mapping every individual myelinated axon across the whole brain

1We developed a pipeline to detail the morphology and complete trajectory of every long distance projecting neuron in large volumes of the non-human primate brain - a projectome. A projectome would organize how the hundreds of brain regions in a primate brain communicate with each other and provide a comprehensive classification of long distance neurons. The reason such projectomes do not exist already is that there is no single imaging technique with the resolution and sampling depth capable of producing one in primates. Here we address that gap by combining new ways to cut brains with minimal tissue loss, nanoscale x-ray microscopy imaging that reveals every individual myelinated axon (MA) and the location, size, and morphology of every neuron, and algorithms for tracing individual myelinated axons for millimeters to centimeters, across tissue gaps.

neuroscience↗

bioRxiv2023

The Development of Synapses in Mouse and Macaque Primary Sensory Cortices

We report that the rate of synapse development in primary sensory cortices of mice and macaques is unrelated to lifespan, as was previously thought. We analyzed 28,084 synapses over multiple developmental time points in both species and find, instead, that net excitatory synapse development of mouse and macaque neurons primarily increased at similar rates in the first few postnatal months, and then decreased over a span of 1-1.5 years of age. The development of inhibitory synapses differed qualitatively across species. In macaques, net inhibitory synapses first increase and then decrease on excitatory soma at similar ages as excitatory synapses. In mice, however, such synapses are added throughout life. These findings contradict the long-held belief that the cycle of synapse formation and pruning occurs earlier in shorter-lived animals. Instead, our results suggest more nuanced rules, with the development of different types of synapses following different timing rules or different trajectories across species.

neuroscience↗

bioRxiv2020

Cocaine causes rapid remodeling of dopaminergic axons, synapses, and mitochondria

Dopaminergic (DA) neurons exert profound influences on behavior including addiction. However, how DA axons communicate with target neurons and how those communications change, for example, with drug exposure, remains poorly understood. We combine recent advances in cell type specific labeling for electron microscopy with large volume three-dimensional serial electron microscopy - connectomics- to detail DA connections in the Nucleus Accumbens (NAc) across multiple animals and after exposure to cocaine. We find that DA axonal varicosities are of four general types: 38% are empty, 25% contain few small ([~]50 nm diameter) vesicles, 19% contain few large ([~]133 nm diameter) vesicles, and 18% have mixed small and large vesicles, suggesting that DA axons may use multiple types of neurotransmitters. Individual DA axons were significantly more likely to contain multiple varicosities of the same type relative to chance, suggesting a new method of DA axon classification. Across all categories, we find only rare examples (<2%, 6/410) of varicosities making specific synapses with any neighboring neuron with the few examples being made exclusively on the shafts and soma of resident NAc neurons. Instead, we find much more frequently (15%) that DA varicosities form spinule-like structures: physical membrane interdigitations with nearby dendrites or excitatory and inhibitory axons. Days after a brief exposure to cocaine, DA axons were extensively branched relative to controls but with similar densities of varicosities and spinules. Additionally, cocaine exposure results in the formation of blind-ended "bulbs" in DA axons, filled with mitochondria, and reminiscent of axonal retraction in the developing and damaged brain. Every bulb was surrounded by elaborated glia further suggestive of active remodeling. Finally, mitochondrial lengths increased by [~]2.2 times relative to control throughout DA axons and NAc spiny dendrites after cocaine exposure but not in DA soma or DA dendrites. We conclude that DA axonal transmission is unlikely to be mediated via classical synapses in the NAc and that the major locus of anatomical plasticity of DA circuits after exposure to cocaine are large scale axonal rearrangements with correlated changes in mitochondria.

neuroscience↗

bioRxiv2020

Primate neuronal connections are sparse as compared to mouse

The mouse and macaque primary visual cortices are foundational models of cortical functioning, particularly at the level of single neurons. Therefore, detailing differences in how individual neurons connect across these species would inform models of cortical functioning and of how brains evolve. However, existing comparisons are limited, measuring synapse density without regard to where synapses are made or on what types of neurons. We use large volume electron microscopy to address this gap, reconstructing a total of 7735 synapses across 160 total neurons (146 excitatory, 14 inhibitory) from adult Rhesus macaque and mouse Layer 2/3 of primary visual cortex (V1). We find that primate connections are broadly sparse: primate excitatory and inhibitory neurons received 3-5 times fewer spine and somatic synapses with lower ratios of excitatory to inhibitory synapses than mouse equivalents. However, despite reductions in absolute synapse number, patterns of axonal innervation were preserved: inhibitory axons sparsely innervated neighboring excitatory neurons in macaque and mouse at similar rates and proportions. On the output side, most excitatory axons in mice myelinated close to the soma (81%) while most primate axons (68%) did not. Interestingly, primate axons, but not mouse axons, that myelinated had 3.3 fold more axon initial segment synapses than axons that did not myelinate, suggesting differential inhibitory control of long distance output in primate brains. Finally, we discover that when artificial recurrent neural networks (RNNs) are constrained by the metabolic cost of creating and maintaining synapses, increasing the number of nodes (e.g. neurons) as networks optimize for a cognitive task, reduces the number of connections per node, similar to primate neurons as compared to mice. One Sentence SummaryUsing large volume serial electron microscopy, we show that primate cortical neural networks are sparser than mouse and using recursive neural nets, we show that energetic costs of synaptic maintenance could underlie this difference.

neuroscience↗