Supporting electrophysiological data for: Reward contingency gates selective cholinergic suppression of amygdala neurons

Basal forebrain cholinergic neurons modulate how organisms process and
respond to environmental stimuli through impacts on arousal, attention,
and memory. It is unknown, however, whether basal forebrain cholinergic
neurons are directly involved in conditioned behavior, independent of
secondary roles in the processing of external stimuli. Using fluorescent
imaging, we found that cholinergic neurons are active during behavioral
responding for a reward – even in prior to reward delivery and in the
absence of discrete stimuli. Photostimulation of basal forebrain
cholinergic neurons, or their terminals in the basolateral amygdala (BLA),
selectively promoted conditioned responding (licking), but not
unconditioned behavior nor innate motor outputs. In vivo
electrophysiological recordings during cholinergic photostimulation
revealed reward-contingency-dependent suppression of BLA neural activity,
but not prefrontal cortex (PFC). Finally, ex vivo experiments demonstrated
that photostimulation of cholinergic terminals suppressed BLA projection
neuron activity via monosynaptic muscarinic-receptor-signaling, while also
facilitating firing in GABAergic interneurons. Taken together, we show
that the neural and behavioral effects of basal forebrain cholinergic
activation are modulated by reward contingency in a target-specific
manner.