Mikko Juusola: Research Introduction
The compound eye of the fly is considered by many to be an ideal model system for studying the extraction of information (cf. Egelhaaf) from the environment in terms of biophysical properties of nerve cells and their synaptic interactions, because:
- Flies perform complex visual orientation tasks with virtuosity superior to most other animals including man.
- Their tiny brain consists of a small number of neurones that compute these tasks, many of which are indentified individuals.
- The neural computations in the fly’s brain can be studied in vivo with relative ease.
Over the last years we have improved both the quality of intracellular recordings in vivo Drosophila photoreceptors (Juusola & Hardie, 2001a,b), visual interneurones, LMCs (Zheng et al., 2006) and mathematical analysis of neural signals (Juusola & de Polavieja, 2003; Asyali & Juusola, 2005).
These advances have enabled us to integrate studies of visual coding with the detailed knowledge of the phototransduction cascade, membrane and synaptic properties available from in vitro studies of Drosophila photoreceptors and LMCs. Recently we have expanded our studies to network level deeper in the fly brain, at motion-sensitive neurones (LPTNs) of lobula plate.
This places us in a unique position to ask specific questions about the roles of individual transduction and synaptic proteins and ion channels during the capture and processing of visual information. In particular, our research has enabled us to study Drosophila photoreceptors and LMCs over a wide range of light intensities and temperatures that were previously impossible in the in vitro preparation.
These studies were further extended by exploiting the array of mutations already established in ion channels in Drosophila to eliminate single ion channel types (initially the Shaker channel but also the Shab and Trpl mutations) from the photoreceptor membrane (Juusola & Hardie, 2001a,b; Niven et al, 2003a,b) and analysing the role of rearing conditions, homeostatic regulation and synaptic feedbacks in the extraction of information from the environment. Number of publications about photoreceptor, LMC and LPTN coding is under preparation.