Biology subjects

Briggman, K. L.

Publications and source records attributed to Briggman, K. L..

7 recordsLinked to original sources

bioRxiv2023

GAUSS-EM: Guided accumulation of ultrathin serial sections with a static magnetic field for volume electron microscopy

Serial sectioning electron microscopy of millimeter-scale 3D anatomical volumes requires the collection of thousands of ultrathin sections. Here we report a high-throughput automated approach, GAUSS-EM, utilizing a static magnetic field to collect and densely pack thousands of sections onto individual silicon wafers. The method is capable of sectioning hundreds of microns of tissue per day at section thicknesses down to 35 nm. Relative to other automated volume electron microscopy approaches, GAUSS-EM democratizes the ability to collect large 3D EM volumes because it is simple and inexpensive to implement. We present two exemplar EM volumes of a zebrafish eye and mouse olfactory bulb collected with the method.

neuroscience↗

bioRxiv2022

Intrinsically photosensitive retinal ganglion cells evade temporal filtering to encode environmental light intensity

The retina encodes environmental light intensity to drive innate physiological responses. The synaptic basis of such coding remains obscure. Intrinsically photosensitive retinal ganglion cells (ipRGCs) are the only retinal output neurons stably encoding intensity. They do so even without their melanopsin photopigment, so specializations in their synaptic drive from bipolar cells (BCs) must also contribute. Here, we shed new light on mechanisms responsible for this unique intensity-coding drive. By ultrastructural reconstruction, we show that specific BC types and unusual ribbon synapses carry photoreceptor signals to ipRGCs. By glutamate imaging and electrophysiology, we show that their light responses are unusually persistent. Still, we find that virtually all BCs encode intensity. Intensity coding becomes restricted to ipRGCs primarily because other RGCs filter out steady-state intensity signals postsynaptically. Thus, neural "pinholes" in global, persistent neural "masking" allow intensity signals to be encoded by ipRGCs and sent to specific centers of the visual brain.

neuroscience↗

bioRxiv2020

Permeabilization-free en bloc immunohistochemistry for correlative microscopy

A dense reconstruction of neuronal synaptic connectivity typically requires high-resolution 3D electron microscopy (EM) data, but EM data alone lacks functional information about neurons and synapses. One approach to augment structural EM datasets is with the fluorescent immunohistochemical (IHC) localization of functionally relevant proteins. We describe a protocol that obviates the requirement of tissue permeabilization in thick tissue sections, a major impediment for correlative pre-embedding IHC and EM. We demonstrate the permeabilization-free labeling of neuronal cell types, intracellular enzymes, and synaptic proteins in tissue sections hundreds of microns thick in multiple brain regions while simultaneously retaining the ultrastructural integrity of the tissue. Finally, we explore the utility of this protocol by performing proof-of-principle correlative experiments combining two-photon imaging of protein distributions and 3D electron microscopy.

neuroscience↗

bioRxiv2020

Connectomic analysis reveals an interneuron with an integral role in the retinal circuit for night vision

The mammalian rod bipolar (RB) cell pathway is perhaps the best-studied circuit in the vertebrate retina. Its synaptic interactions with other retinal circuits, however, remain unresolved. Here, we combined anatomical and physiological analyses of the mouse retina to discover that the majority of synaptic inhibition to the AII amacrine cell (AC), the central neuron in the RB pathway, is provided by a single interneuron type: a multistratified, axon-bearing GABAergic AC, with dendrites in both ON and OFF synaptic layers, but with a pure ON (depolarizing) response to light. We used the nNOS-CreER mouse retina to confirm the identity of this interneuron as the wide-field NOS-1 AC. Our study demonstrates generally that novel neural circuits can be identified from targeted connectomic analyses and specifically that the NOS-1 AC mediates long-range inhibition during night vision and is a major element of the RB pathway.

neuroscience↗

bioRxiv2019

Prepontine non-giant neurons drive flexible escape behavior in zebrafish

Many species execute ballistic escape reactions to avoid imminent danger. Despite fast reaction times, responses are often highly regulated, reflecting a trade-off between costly motor actions and perceived threat level. However, how sensory cues are integrated within premotor escape circuits remains poorly understood. Here we show that in zebrafish, less precipitous threats elicit a delayed escape, characterized by flexible trajectories, that are driven by a cluster of 38 prepontine neurons that are completely separate from the fast escape pathway. Whereas neurons that initiate rapid escapes receive direct auditory input and drive motor neurons, input and output pathways for delayed escapes are indirect, facilitating integration of cross-modal sensory information. Rapid decision making in the escape system is thus enabled by parallel pathways for ballistic responses and flexible delayed actions.

neuroscience↗

bioRxiv2018

Synaptic circuits for irradiance coding by intrinsically photosensitive retinal ganglion cells

We have explored the synaptic networks responsible for the unique capacity of intrinsically photosensitive retinal ganglion cells (ipRGCs) to encode overall light intensity. This luminance signal is crucial for circadian, pupillary and related reflexive responses light. By combined glutamate-sensor imaging and patch recording of postsynaptic RGCs, we show that the capacity for intensity-encoding is widespread among cone bipolar types, including OFF types.\n\nNonetheless, the bipolar cells that drive ipRGCs appear to carry the strongest luminance signal. By serial electron microscopic reconstruction, we show that Type 6 ON cone bipolar cells are the dominant source of such input, with more modest input from Types 7, 8 and 9 and virtually none from Types 5i, 5o, 5t or rod bipolar cells. In conventional RGCs, the excitatory drive from bipolar cells is high-pass temporally filtered more than it is in ipRGCs. Amacrine-to-bipolar cell feedback seems to contribute surprisingly little to this filtering, implicating mostly postsynaptic mechanisms. Most ipRGCs sample from all bipolar terminals costratifying with their dendrites, but M1 cells avoid all OFF bipolar input and accept only ectopic ribbon synapses from ON cone bipolar axonal shafts. These are remarkable monad synapses, equipped with as many as a dozen ribbons and only one postsynaptic process.

neuroscience↗

bioRxiv2017

Structural and functional diversity of a dense sample of retinal ganglion cells

To aid understanding of retinal structure and function, we present as an online resource the dendritic arbors and visual responses of ganglion cells in a single patch of mouse retina. We divide the inner plexiform layer, which contains the dendritic arbors of ganglion cells, into four sublaminae defined by a purely anatomical principle of arbor segregation. The sublaminae serve as the starting point for a hierarchical clustering of our ganglion cells. We propose and apply a quantitative criterion for validating a cluster as a ganglion cell type: the aggregate neurite density of a type should be approximately uniform (\"density conservation\"). Finally, we find that ganglion cells arborizing in the inner marginal sublamina of the inner plexi-form layer exhibit significantly more sustained visual responses on average.

neuroscience↗