YKavli April Meeting (Zoom)
Please Note: This meeting will be held online via Zoom.
The Kavli Institute for Brain and Mind (KIBM) hosts meetings for early career researchers to help foster their research community at UCSD. Our goal is to bring early career researchers (non-faculty) together so they can meet, network and share research. This event is open only to EARLY CAREER RESEARCHERS (grad student/ postdoc/ project scientist).
Silvia Vincenzi - Deciphering the Role of Serotonin in Brain Circuit Formation
Bio: Silvia is about to finish her PhD in Australia and to start a post-doc position in Yimin Zou lab at UCSD. She has previously graduated from a Bachelor of Biotechnology with two internships in neuroscience in Italy and in the UK and from a Master of Molecular Medicine in Sweden. She is passionate about axon guidance and thrilled to unravel how growth cones lead their way to form functional neuronal circuits that underlie behaviour.
Abstract: The neurotransmitter serotonin has been implicated in a range of complex neurological disorders linked to alterations of neuronal circuitry. Serotonin is synthesized in the developing brain before most neuronal circuits become fully functional, suggesting that serotonin might play a distinct regulatory role in shaping circuits prior to its function as a classical neurotransmitter. In this study, we asked if serotonin acts as a guidance cue for axons during development by examining how serotonin alters the motility of sensory neuron growth cones. Using a growth cone motility assay, we found that extracellular gradients of serotonin acted as both an attractive and repulsive guidance cue through a narrow concentration range. Low concentrations of serotonin (50µM) elicited attraction, mediated by the serotonin 5-HT2a receptor whilst high concentrations (100µM) elicited repulsion mediated by the 5-HT1b receptor. Importantly, pharmacological interventions and high resolution imaging of growth cones suggested that these receptors signalled through their canonical pathways of endoplasmic reticulum-mediated calcium release and cAMP depletion respectively. This novel characterisation of growth cone motility in response to serotonin gradients provides compelling evidence that secreted serotonin acts as an axon guidance cue to shape neuronal circuit formation during development. In vitro optogenetic manipulation of Gαq signalling associated with the 5HT2a receptor, reversed growth cone attraction to repulsion from serotonin, further demonstrating the role of serotonin as a bidirectional guidance cue. To examine the function of serotonin in an intact animal, we investigated early circuit development in the zebrafish. Although previous work has suggested a non-canonical role for serotonin in early development, it remained unclear whether serotonin modulates the guidance of pioneer axons or rather plays a more instructive role in overall circuit function. We hypothesized that optogenetic manipulation of Gαq signalling is sufficient to modulate neural connectivity in early zebrafish larvae. Using a range of behavioural assays and time-lapse recordings of axon trajectories, we observed a critical developmental window during which altered Gαq signalling might lead to structural and functional abnormalities. Unravelling how serotonin functions to regulate the normal wiring of the brain will allow us to better understand how dysfunction in serotonin signalling contributes to important neurodevelopmental disorders.
Arash Fassihi - Time perception in rats and humans
Speaker: Arash Fassihi, Postdoctoral researcher, Kleinfeld Laboratory, UCSD.
Abstract: Our interactions with the world are based on perceptual decisions that frequently depend on monitoring the timing and duration of sensory events. It is unknown whether the mechanisms for perceiving stimulus duration rely on a central clock-like circuit or else are embedded within the sensory processing pathway. I will describe recent experimental findings in which optogenetic manipulation of neuronal activity in the somatosensory cortex (vS1) of rats alters perceived duration and will discuss the interaction between stimulus duration and its intensity. In these experiments, optogenetic excitation of vS1 neurons led to an overestimation of stimulus duration; optogenetic suppression led to underestimation. I will discuss our proposed model of time perception in both humans and rats. In this model, spike trains from vS1 are accumulated at the next stage by an integrator. By dilating and compressing duration judgment through direct control of vS1, these experiments identify the sensory cortex as a key component of the time perception network.
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Chairs: Marta Pratelli, Karishma Chhabria