The nervous system is tasked with the challenge of processing a variety of sensory stimuli from the environment with limited coding space and energy consumption. Recent findings challenge the traditional view of the neuron as the elementary functional unit of the nervous system, in which dendrites mainly serve as input sites, and action potential propagation through axons generates output. Instead, individual neurites have emerged as the single functional unit capable of computing inputs and generating outputs locally.
Despite recent advances, the link between the mechanisms that facilitate local computations and their behavioural relevance remains unclear. I addressed this problem in Drosophila Melanogaster. The anatomical organisation of the mushroom body, a brain region associated with learning, has a compartmentalised architecture that forms the basis for local computations. My project studied subcellular signalling in the mushroom body and its role in memory formation, with emphasis on the non-spiking APL neuron that is involved in sparse odour coding and memory formation, to determine if it operates locally. To investigate this, I addressed the following points.
1. I investigated the nature of activity spread in the APL neuron. I found that input to the APL neuron evokes activity that attenuates as it propagates, supporting local computations.
2. I characterised the spatial nature of inhibition from the APL neuron onto mushroom body neurons. I found that the inhibition had a strong local effect that diminished with distance.
3. I sought to determine if there are spatial differences in the APL neuron’s response to electric shock, and if plasticity in the APL neuron is similarly spatially distinct. I found that electric shock responses are spatially distinct, but my data on plasticity was inconclusive.
4. I investigated the effects of local muscarine signalling on Kenyon cell odour responses. I found that muscarine signalling has spatially distinct effects.
