PhD Opportunity: Linking circuits to visually-driven behaviours
A PhD opportunity is available to start in 2024, funded by the Leverhulme Trust. Closing date for applications 26th February 2024 and more information can be obtained here. Enquiries are very welcome – drop me a line L.Lagnado@sussex.ac.uk. Formal applications through here.
The retina and brain of larval zebrafish provide an excellent context in which to study how neural circuits process visual information. We can finely control the input to the circuits while observing the activity of neurons and synapses within them and then relate circuit activity to visually-driven behaviours that they drive. We achieve this by using i) multiphoton microscopy to image fluorescent reporter proteins in neurons as we present visual stimuli, and ii) video-based analysis of motor behaviours driven by vision, such as the optomotor response.
Our general aim is to understand how the retinal output is generated and the subsequent processing of this output in downstream visual centres. Directly linked to this, we are investigating the plasticity of these circuits and the mechanisms that adjust visually-driven behaviour in response to information from other senses (especially smell) and/or changes in internal state (especially circadian control).
How much information does a synapse transmit?
We recently published a paper in Nature Communications titled “Diurnal changes in the efficiency of information transmission at a sensory synapse“. Neuromodulators adapt sensory circuits to changes in the external world or the animal’s internal state and synapses are key control sites for such plasticity. Less clear is how neuromodulation alters the amount of information transmitted through the circuit. We investigated this question in the context of the diurnal regulation of visual processing in the retina of zebrafish, focusing on ribbon synapses of bipolar cells. We demonstrate that contrast-sensitivity peaks in the afternoon accompanied by a four-fold increase in the average Shannon information transmitted from an active zone. This increase reflects higher synaptic gain, lower spontaneous “noise” and reduced variability of evoked responses. Simultaneously, an increase in the probability of multivesicular events with larger information content increases the efficiency of transmission (bits per vesicle) by factors of 1.5-2.7. This study demonstrates the multiplicity of mechanisms by which a neuromodulator can adjust the synaptic transfer of sensory information.