Cell-type-specific striatal modulation of amygdalar acetylcholine in salience assignment

The salience assignment is pivotal for both natural and artificial intelligence. Pioneering studies established that basal forebrain cholinergic neurons process behaviorally relevant salient information. However, the neural circuit mechanism underlying salience assignment remains poorly understood. Here we show that the acetylcholine (ACh) level in the basolateral amygdala (BLA) dynamically represented behavioral salience. Distinct neuronal subpopulations in the nucleus accumbens (NAc), D1- and D2-expressing medium spiny neurons (MSNs), antagonistically and specifically promote and suppress ACh release in the BLA, but not the cortex and hippocampus. These striatal D1 and D2 MSNs regulate BLA ACh by disinhibiting and inhibiting cholinergic neurons in the basal forebrain subregion substantia innominata (SI), respectively. Optogenetic manipulations of the pathway from striatal D1 and D2 MSNs to the SI opposingly affect associative learning. Our findings uncover an unconventional role of striatal MSNs in salience assignment via regulating the salience-representing amygdalar ACh activity.