Cholinergic modulation of olfactory bulb circuits during odor exposure and discriminative learning. Top left: Schematic of basal forebrain cholinergic projections from the HDB to the OB. In the right panel, major cell types are labeled. Within the glomerular layer, excitatory OSN axons innervate the MTCs, as well as inhibitory SACs and granule cells. Cholinergic input (ChAT-positive; maroon) innervates multiple cell types. Cholinergic input to the SACs is highlighted. Top right: Circuit diagram showing SAC-mediated inhibition of OSN input. SACs express tyrosine hydroxylase (TH), glutamate decarboxylase 1 (GAD1), and muscarinic receptor CHRM2. Cholinergic input from the HDB acts on SACs to regulate inhibition of sensory input. Bottom: Cholinergic–SAC interactions under different learning conditions. (i) Passive exposure: Cholinergic input modestly recruits SAC activity, with increased TH expression, broadly modulating OSN input. (ii) Discriminative learning: In the naïve state, SAC connectivity and cholinergic modulation are uniform across glomeruli. After training (CS+ vs. CS− discrimination), SAC molecular markers (TH, CHRM2) are upregulated selectively in CS+ associated glomeruli, enhancing cholinergic modulation and reciprocal inhibition to the OSNs. For rewarded odor, cholinergic input strongly inhibits SACs and disinhibits OSN–MTC pathways, amplifying CS+ responses. In the punished condition, SAC-mediated inhibition is maintained for CS− glomeruli, suppressing responses.
#DiscriminativeLearning enhances #sensory contrast for rapid, accurate decisions, but how? This study describes a sensory- #forebrain circuit centered on #dopaminergic short axon cells in the mouse #olfactory bulb, which refines sensory input during learning @plosbiology.org 🧪 plos.io/4pvost3