The complete synaptic-level connectome of a nervous system and experimental connectomics

The nervous system enables animals to sense their surroundings and respond appropriately to specific events using previous experiences and innate biases as a guide. The building blocks are neurons, which are cells that integrate input from external stimuli or other neurons and then communicate them to other neurons or to actuators such as muscles. The only complete map of neural connections was produced for a nematode with only 300 neurons.

We propose to map the pattern of connections of the far more numerically complex nervous system of the fruit fly maggot, an organism whose embryonic development and the overall architecture of its nervous system has numerous parallels with humans. Neural circuits are dynamic and changing connections between neurons is one way that memories can be stored. Building on previous work, we will train animals to like an odour and others to dislike it, and we will compare how the exact same circuit differs in its connections, revealing the ‘engram’: a persistent alteration that represents a memory. We will also study the changes to neural circuits caused by genetic mutations related to neural diseases.