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Linking the molecular organization of active zones to temporal neural coding

Subject Area Molecular Biology and Physiology of Neurons and Glial Cells
Term from 2018 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 408264519
 
Final Report Year 2024

Final Report Abstract

Information processing in the brain relies on the exact encoding of sensory stimuli to generate a consistent and reliable output. In the nervous system, neuronal activity is relayed, filtered, and integrated via chemical synapses. Therefore, temporal codes, i.e. where precise spike timing carries coding information, are expected to depend critically on the properties of neurotransmitter release from the presynaptic active zone (AZ). However, the causal relation between AZ physiology and temporal codes has not yet been studied in detail. The molecular architecture of the AZ affects the timing and stability of synaptic exocytosis. AZ proteins, such as Drosophila Bruchpilot (Brp), influence the temporal precision of excitation-secretion coupling and modulate sustained transmitter release during continuous synaptic activity. The present project aimed to investigate how the molecular organization of the AZ affects the neural temporal code - its precision and its stability at different stimulation intensities. Focusing on synapses between sensory neurons and second order neurons in the olfactory system of Drosophila melanogaster, we obtained a deeper mechanistic understanding of how synaptic function shapes neural coding in the live, behaving animal. The results show that the properties of the AZ are critical for generating a reliable neural code. Reducing neurotransmitter release probability of olfactory sensory neurons disrupts both neural coding and behavioral reliability. Strikingly, a target-specific homeostatic increase of Brp-positive AZ numbers rescues these defects within a day. These findings demonstrate an important role for synaptic plasticity in maintaining neural coding reliability and are of pathophysiological interest by uncovering an elegant mechanism through which the neural circuitry can counterbalance perturbations.

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