Local 5-HT signals bi-directionally modulate the coincidence time window of associative learning
Authors: Xuelin Li; Jianzhi Zeng; Zimo Zhangren; Yulong Li
Affiliation: Peking University, School of Life Sciences
Keywords: f. learning/memory; b. live imaging
Temporal coincidence between a conditioned stimulus (CS) and an unconditioned stimulus (US) is an essential component in Pavlovian associative learning. Despite its ubiquitous presence, it remains unknown whether the coincidence time-window can be regulated. Here we assign this function in Drosophila to the dorsal paired medial (DPM) neuron, which innervates the mushroom body (MB) and releases 5-HT compartmentally in response to both an odorant (the CS) and electric shock (the US). The DPM neuron is activated by local acetylcholine (ACh) release from MB Kenyon cells through nicotinic ACh receptors, meanwhile releases 5-HT to reduce ACh release via the 5-HT1a receptor. Suppressing or promoting the 5-HT release from DPMs bi-directionally regulates the coincidence time-window for odor-shock pairing, which gates olfactory learning and synaptic plasticity changes in the MB. This mechanism provides a model for studying how an organism times the temporal continuity of environmental events and learns the underlying causal relationship.