Biology subjects

Morgan, J. L.

Publications and source records attributed to Morgan, J. L..

3 recordsLinked to original sources

bioRxiv2023

Subcellular pathways through VG3 amacrine cells provide regionally tuned object-motion-selective signals in mouse retina.

We combined subcellular calcium imaging and connectomic reconstruction to understand the flow of information through a plexus of excitatory VGluT3-expressing mouse retinal amacrine cells (VG3s). We found that VG3s received inputs from all nearby bipolar cell types but exhibited a strong preference for the fast type 3a bipolar cells. We used our connectivity map and physiological recordings to predict the influence of these bipolar cells on different types of RGCs innervated by VG3s and found that the depth of retinal ganglion cell (RGC) dendritic arbor stratification determined the RGCs view of bipolar cells through the VG3 plexus. We also found that both VG3s and their RGC targets were often innervated by the same bipolar cells. RGCs that extend processes into the middle layers of the inner plexiform layer, therefore, encounter a plexus of small object motion selective glutamatergic excitation that is complementary to the local bipolar cell input.

neuroscience↗

bioRxiv2021

The organization of the gravity-sensing system in zebrafish

Motor circuits develop in sequence from those governing fast movements to those governing slow. Here we examine whether upstream sensory circuits are organized by similar principles. Using serial-section electron microscopy in larval zebrafish, we generated a complete map of the gravity-sensing (utricular) system spanning from the inner ear to the brainstem. We find that both sensory tuning and developmental sequence are organizing principles of vestibular topography. Patterned rostrocaudal innervation from hair cells to afferents creates an anatomically inferred directional tuning map in the utricular ganglion, forming segregated pathways for rostral and caudal tilt. Furthermore, the mediolateral axis of the ganglion is linked to both developmental sequence and neuronal temporal dynamics. Early-born pathways carrying phasic information preferentially excite fast escape circuits, whereas later-born pathways carrying tonic signals excite slower postural and oculomotor circuits. These results demonstrate that vestibular circuits are organized by tuning direction and dynamics, aligning them with downstream motor circuits and behaviors.

neuroscience↗

bioRxiv2019

An individual interneuron participates in many kinds of inhibition and spans much of the mouse visual thalamus

One way to assess a neurons function is to describe all its inputs and outputs. With this goal in mind, we used serial section electron microscopy to map 899 synaptic inputs and 623 outputs in one inhibitory interneuron in a large volume of the mouse visual thalamus. This neuron innervated 256 thalamocortical cells spread across functionally distinct subregions of the visual thalamus. All but one of its neurites were bifunctional, innervating thalamocortical and local interneurons while also receiving synapses from the retina. We observed a wide variety of local synaptic motifs. While this neuron innervated many cells weakly, with single en passant synapses, it also deployed specialized branches that climbed along other dendrites to form strong multi-synaptic connections with a subset of partners. This neurons diverse range of synaptic relationships allows it to participate in a mix of global and local processing but defies assigning it a single circuit function.

neuroscience↗