A synaptic mechanism for encoding the learned value of action-derived safety

Area of Science:

• Neuroscience
• Behavioral Neuroscience

Background:

• Adaptive behavior relies on integrating relevant signals into action circuits.
• The thalamus's role in regulating information flow is established, but its tracking of internal goals is unclear.

Purpose of the Study:

• To investigate if the paraventricular thalamus (PVT) encodes internally generated goal signals.
• To elucidate the neural mechanisms by which learned goals access motivational circuitry.

Main Methods:

• Utilized in vivo calcium imaging and electrophysiology in mice during active avoidance learning.
• Employed chemogenetics for selective silencing of the PVT→nucleus accumbens (NAc) pathway.
• Investigated synaptic plasticity at PVT-NAc synapses using electrophysiology and molecular techniques.

Main Results:

• PVT→NAc neurons developed signals encoding the motivational value of safety, dependent on experience and outcome devaluation.
• Silencing the PVT→NAc pathway reduced the motivational value of safety without affecting action-outcome learning.
• PVT input induced synaptic potentiation at PVT-cholinergic interneuron (CIN) synapses in the NAc, regulating dopamine release.

Conclusions:

• Identified a novel thalamostriatal pathway (PVT→NAc) critical for assigning motivational value to learned safety signals.
• Demonstrated that synaptic plasticity at PVT-CIN synapses underlies the motivational impact of safety.
• This mechanism enables learned goals to gain access to neural circuits guiding motivated behavior.