Computing with Fruit Fly Brain Circuits
The FlyBrainLab is an ideal interactive platform for exploring the molecular architecture and, executable models of fly brain circuits and local processing units. Briefly, we describe below some of the main ongoing projects with a focus on investigating the underlying model of computation of fruit fly brain circuits and local processing units. Building the functional map of the fruit fly brain is one of our major research goals.
A key functionality of olfactory sensory neurons (OSNs) in the Drosophila antennae is to jointly encode both odorant identity and odorant concentration. The identity of an odorant is combinatorially encoded by the set of responding OSN groups expressing the same receptor type, and the size of OSN set varies as the concentration changes. The temporal response of an OSN simultaneously represents the information of odorant concentration and concentration gradient. We advanced a comprehensive model of fruit fly OSNs as a cascade consisting of an odorant transduction process and a biophysical spike generator.
The Drosophila Retina has been extensively characterized in the literature in terms of structure, connectivity and function. Our investigations provide a detailed description of the algorithms required for a full-scale parallel emulation of the fruit fly Retina including (i) the mapping of the visual field onto the photoreceptors, (ii) the phototransduction process, and (iii) the parallel processing of the visual field by the entire Retina. We also provided detailed algorithms, their implementation and their visual evaluation with moving images on GPUs.
The central complex (CX) is a set of neuropils in the center of the fly brain that have been implicated as playing an important role in vision-mediated behavior and integration of spatial information with locomotor control. We have created a web application that enables simultaneous graphical querying and construction of executable models of the CX neural circuitry based upon currently available information regarding the geometry and polarity of the arborizations of identified local and projection neurons in the CX. The application's novel functionality is made currently possible by the FlyBrainLab.
The brain functional map consists of the canonical fruit fly brain circuits and their I/O behavior at different levels of abstraction
Methodology for the Biological Validation of Fruit Fly Brain Circuits
Efforts at reverse engineering the brain must ultimately confront the need to validate hypotheses regarding neural information processing against actual biological systems. To achieve biological validation, the computational modeling of the fly brain circuits must be tightly integrated with increasingly precise electrophysiological techniques and the recorded data evaluated with novel functional identification methods. This will enable direct comparison of the output of circuit models interactively executed on the FlyBrainLab platform to that of corresponding circuits in the brain regions of interest.
The methodology for the biological validation of fruit fly brain circuits is schematically depicted below.
Neural responses to sensory stimuli are recorded from live fly brain circuits in real time and compared to the computed responses of the corresponding components in a fly brain circuit model executed on the same time scale. Discrepancies between these responses and new connectome data may be used to improve the model's accuracy.