The superior colliculus gates dopamine responses to conditioned stimuli in visual classical conditioning

Area of Science:

• Neuroscience
• Behavioral Science
• Neurobiology

Background:

• Midbrain dopamine neurons are known to respond to conditioned stimuli (CS) predicting rewards in classical conditioning.
• The precise neural mechanisms by which dopamine neurons associate neutral CS with rewards remain largely unknown.

Purpose of the Study:

• To investigate how the brain forms associations between neutral conditioned stimuli and rewards during classical conditioning.
• To elucidate the role of the superior colliculus (SC) in mediating these associations.

Main Methods:

• Utilized classical Pavlovian conditioning paradigms in male rats and both male and female mice.
• Recorded neuronal responses in the superior colliculus (SC) to visual conditioned stimuli (CS).
• Manipulated visual, dopamine, and serotonin inputs to the SC and assessed the impact on neuronal responses and dopamine neuron activity.

Main Results:

• The superior colliculus (SC) developed potentiated neuronal responses to a visual CS during conditioning.
• These potentiated SC responses were found to drive dopamine neuron activity.
• Potentiation of visual responses in the SC required a behaviorally relevant temporal interval between the CS and reward, and the convergence of visual, dopamine, and serotonin inputs.
• Inhibiting the potentiation of SC visual responses suppressed subsequent dopamine neuron responses to the CS.

Conclusions:

• The superior colliculus (SC) plays a crucial role in associating visual cues with rewards during classical conditioning.
• A mechanism involving the potentiation of visual responses in the SC, driven by the convergence of sensory and neuromodulatory inputs, underlies CS-reward association.
• This study reveals how the brain links behaviorally relevant visual information with unconditioned stimuli.