The visual processing stages and their behavioural relevance in Drosophila melanogaster.
Lead Research Organisation:
University of Cambridge
Department Name: Physiology Development and Neuroscience
Abstract
The fruit fly is a key model in vision research. Its small brain and compact neural circuits can be manipulated by sophisticated genetic tools, making it possible to dissect the neuronal machinery underlying vision. Recent evidence suggests that colour and motion pathways are not completely segregated, and instead interact at early stages of visual processing (Wardill et al., 2012). Thus project will aim to quantify neural activity from the medulla, lobula and lobula plate visual processing neuropiles and identify the computations that transform colour and motion sensory inputs into visual perceptions and the output signals used to drive behaviour. To determine computational strategies, a combination of genetic, imaging, electrophysiological and behavioural methodologies is required. Head-fixed flies will be presented with custom panoramic visual stimuli of moving patterns and colour. Simultaneously their neural activity will be monitored with 2-photon imaging of fluorescently reported calcium dynamics (Chen et al. 2014). Matlab, will coordinate the testing process for specific contrasts, colours, patterns, centre-surround ratios, angles, velocities and natural scenes. Neuron labelling methods will label either diverse or specific neuron populations with fluorescent neural activity indicators. Head-fixed animals will also undertake behavioural navigational tasks by placing them in a virtual reality (VR) arena, monitoring their movements with a FicTrac camera tracking system (Moore et al., 2014) and externally modulating neural activity in visual circuits using a red-shifted channel rhodopsin (that does not distract the animal). Through this VR paradigm we will use naturalistic stimuli to closely mimic visual behaviour in the wild.
Organisations
People |
ORCID iD |
| Trevor Wardill (Primary Supervisor) | |
| Rachael Feord (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M011194/1 | 01/10/2015 | 31/03/2024 | |||
| 1643645 | Studentship | BB/M011194/1 | 01/10/2015 | 30/09/2019 | Rachael Feord |
| Description | The fruit fly, Drosophila melanogaster, has emerged as a key model for invertebrate vision research. Despite extensive characterisation of motion vision, very little is known about how flies process colour information, or how the spectral content of light affects other visual modalities. With the aim to accurately dissect the different components of the Drosophila visual system responsible for processing colour, we have developed a versatile visual stimulation setup to probe for the combinations of spatial, temporal and spectral visual response properties. Using flies that express neural activity indicators, we can track visual responses to a projected colour stimulus (i.e. narrow bands of light across the spectrum) via a two-photon imaging system. The visual stimulus is projected on a specialised screen material that scatters wavelengths of light across the spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. Using this setup, we are characterising spectral responses, intensity-response relationships, and receptive fields of neurons in the early visual system of a variety of genetically modified strains of Drosophila. Specifically, we compared visual responses in the medulla of flies expressing either a subset or all photoreceptor opsins, with differing levels of screening pigment present in the eye. Although we found no evidence for input from the colour photoreceptors in pan-neuronal medulla responses, a reduction in screening pigment shifts the general spectral response in the neuropil towards the longer wavelengths of light. We have also established receptive fields across the different layers of the medulla for the peak spectral response wavelength. Our results suggest a variety of spatial and temporal receptive field profiles, differing across the layers of the neuropil. |
| Exploitation Route | The setup we have developed provides a novel way of probing colour vision by enabling simultaneous two-photon functional imaging of neural activity indicators and precise colour visual stimulation. |
| Sectors | Aerospace, Defence and Marine,Agriculture, Food and Drink,Education |