Past events

Visual information is transferred at the ribbon synapse – the first synapse of the visual system – from photoreceptors to bipolar cells and horizontal cells. Whereas multiple bipolar cell types form parallel channels of vertical signal transfer to ganglion cells, the output neurons of the retina, the molecular basis of horizontal function within the retinal circuitry remains enigmatic. We have combined electrophysiology and calcium imaging with immunocytochemistry as well as single-cell RNA-sequencing and machine-learning approaches to establish a detailed map of voltage- and ligand-gated ion channels expressed by horizontal cells of the vertebrate retina. Our results provide a characteristic molecular signature of ionotropic glutamate receptors responsible for converting photoreceptor signals into postsynaptic membrane potential changes. We suggest that local information processing in horizontal cell dendrites is accompanied by cell-wide signals mediated by activation of voltage-gated calcium and sodium channels, which generate spike-like events. Comparison across different vertebrate species indicates a common theme of ion channel expression with variations based on evolutionary distance. Correlating the spatio-temporal pattern of horizontal cell activity with the biophysical properties of ion channels and neurotransmitter receptors will provide a better understanding of early signal processing in the vertebrate retina.

Brainstem nuclei in humans play a crucial role in vital functions, such as arousal, autonomic homeostasis, sensory and motor relay, nociception, and sleep and have been implicated in a vast array of brain pathologies, including disorders of consciousness, sleep disorders, autonomic disorders, pain, Parkinson’s disease and other motor disorders. Yet, an in vivo delineation of most human brainstem nuclei location and connectivity using conventional imaging has been elusive because of limited sensitivity and contrast for detecting these small regions using standard neuroimaging methods. In this talk, Dr. Bianciardi will present the probabilistic atlas and connectome of 31 brainstem nuclei of the arousal, motor, autonomic and sensory systems developed by her team in healthy living humans using structural, functional and diffusion-based MRI at 7 Tesla. She will also show the translatability of 7 Tesla connectivity results to conventional 3 Tesla imaging. Dr Bianciardi will conclude her seminar by presenting the first translational application of the brainstem nuclei atlas to investigate arousal and motor mechanisms in traumatic coma and premanifest synucleinopathy.