Norepinephrine Potentiates and Serotonin Depresses Visual Cortical Responses by Transforming Eligibility Traces

Abstract

Reinforcement allows organisms to learn which stimuli predict subsequent biological relevance. Hebbian mechanisms of synaptic plasticity are insufficient to account for reinforced learning because neuromodulators signaling biological relevance are delayed with respect to the neural activity associated with the stimulus. A theoretical solution is the concept of eligibility traces (eTraces), silent synaptic processes elicited by activity which upon arrival of a neuromodulator are converted into a lasting change in synaptic strength. Previously we demonstrated in visual cortical slices the Hebbian induction of eTraces and their conversion into LTP and LTD by the retroactive action of norepinephrine and serotonin Here we show in vivo in V1 that the induction of eTraces and their conversion to LTP/D by norepinephrine and serotonin respectively potentiates and depresses visual responses. We also show that the integrity of this process is crucial for ocular dominance plasticity, a canonical model of experience-dependent plasticity.

Two types of locus coeruleus norepinephrine neurons drive reinforcement learning

“…The mechanisms likely include multiple cell types and receptors. NE modulates synaptic plasticity across brain areas (Delaney et al, 2007; Seol et al, 2007; Carey and Regehr, 2009; Hong et al, 2022). Ex vivo electrophysiology indicates different effects of NE on different cell types in frontal cortex (Kawaguchi and Shindou, 1998; Dembrow et al, 2010; Dembrow and Johnston, 2014).…”