The human subthalamic nucleus and globus pallidus internus differentially encode reward during action control

Area of Science:

• Neuroscience
• Human Brain Mapping
• Movement Disorders

Background:

• The subthalamic nucleus (STN) and globus pallidus internus (GPi) are implicated in motor control and have recently been suggested to encode reward information.
• Few studies have investigated this reward encoding in humans, particularly within the context of neurological disorders.

Purpose of the Study:

• To investigate the encoding of reward and loss (valence) by STN and GPi neurons in humans with Parkinson's disease.
• To test the hypothesis that STN and GPi neuronal firing rates change in response to reward- and loss-related stimuli during a behavioral task.

Main Methods:

• Recorded single-unit neuronal activity in the STN and GPi of Parkinson's disease patients.
• Utilized a behavioral task where action choices were linked to rewarding, punitive, or neutral outcomes.
• Analyzed neuronal firing rates in relation to the valence of task outcomes.

Main Results:

• STN and GPi neurons demonstrated encoding of valence-related information during action control.
• A greater proportion of valence-responsive neurons were found in the STN compared to the GPi.
• Reward-related stimuli mobilized a larger proportion of STN neurons than loss-related stimuli.
• Significant limbic overlap with sensorimotor regions was observed in both STN and GPi, exceeding previous reports.

Conclusions:

• STN and GPi neurons play a role in processing valence during action control in Parkinson's disease.
• The findings highlight a greater role for the STN in processing reward compared to loss.
• The observed limbic-sensorimotor overlap may elucidate functional alterations seen after deep brain stimulation therapy in the STN and GPi.