Outcome-Locked Cholinergic Signaling Suppresses Prefrontal Encoding of Stimulus Associations

Area of Science:

• Neuroscience
• Cognitive Science
• Neurobiology

Background:

• Acetylcholine (ACh) traditionally modulates cognition via slow, tonic signaling.
• Recent findings reveal rapid, phasic ACh release linked to specific events.
• Understanding phasic ACh's role in associative learning is crucial for cognitive enhancement strategies.

Purpose of the Study:

• To investigate the functional role of phasic cholinergic signaling in the medial prefrontal cortex (mPFC) during aversive associative learning.
• To determine how precisely timed ACh signals influence the association between a conditioned stimulus (CS) and an unconditioned stimulus (US).

Main Methods:

• Utilized optogenetics to manipulate cholinergic terminals in the mPFC of male mice during aversive associative learning tasks.
• Monitored cholinergic terminal activity using photometry during conditioned stimulus (CS) and unconditioned stimulus (US) presentations.
• Assessed associative learning strength and c-Fos expression in the mPFC.

Main Results:

• Optogenetic inhibition of ACh during the aversive outcome (US) enhanced CS-US association formation.
• Optogenetic excitation of ACh during the US blocked association formation.
• Inhibition of ACh during the cue (CS) impaired learning, while excitation had minor effects.
• Cholinergic terminals showed dynamic responses to CS and US, correlating with learning strength.

Conclusions:

• Phasic cholinergic signaling in the mPFC exerts opposing effects on aversive associative learning based on its timing relative to the cue or outcome.
• Precisely timed ACh signals are critical for refining associative memory formation.
• Findings suggest novel therapeutic targets for cognitive disorders like Alzheimer's disease by precisely controlling ACh signaling.