Cortical visual processing evokes short-latency reward-predicting cue responses in primate midbrain dopamine neurons

Area of Science:

• Neuroscience
• Visual Processing
• Dopamine Signaling

Background:

• Dopamine (DA) neurons respond rapidly to reward-predicting visual cues after classical conditioning.
• Both cortical and subcortical visual pathways are potential routes for these cue-elicited DA responses.
• Previous work demonstrated the subcortical superior colliculus (SC) pathway's role in mediating these responses after V1 lesions.

Purpose of the Study:

• To investigate whether the cortical visual pathway can also mediate short-latency cue responses in DA neurons.
• To examine the role of the cortical pathway in DA neuron activation when the subcortical pathway is compromised.

Main Methods:

• Utilized macaques with prior unilateral V1 lesions.
• Recorded DA neuronal activity during a classical conditioning task with visual stimuli presented to the intact visual field.
• Inactivated the ipsilateral superior colliculus (SC) using muscimol injections.

Main Results:

• Inactivation of the SC did not affect conditioned behavioral responding.
• Reward-predicting, short-latency (~100 ms) cue-elicited DA neuronal responses remained unaffected after SC inactivation.
• These findings persisted in the presence of a V1 lesion.

Conclusions:

• The intact cortical visual pathway is capable of mediating short-latency cue-elicited responses in DA neurons.
• This occurs independently of a functioning subcortical visual system.
• Suggests a parallel and potentially redundant role for cortical and subcortical pathways in visual-driven dopamine signaling.