A selective role for right insula--basal ganglia circuits in appetitive stimulus processing

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuroimaging

Background:

• Hedonic evaluation ('liking') and incentive motivation ('wanting') are fundamental aspects of behavior.
• The basal ganglia and insula (BG-I) neural network is implicated in processing reward and emotion.
• Hemispheric lateralization of these functions within the BG-I remains incompletely understood.

Purpose of the Study:

• To investigate the hemispheric lateralization of hedonic evaluation and incentive motivation.
• To determine the role of the right versus left basal ganglia-insula (BG-I) complex in these processes.
• To examine how BG-I damage affects responses to positively and negatively valenced stimuli.

Main Methods:

• Compared patients with right or left BG-I damage to healthy controls.
• Assessed 'liking' using explicit pleasantness ratings on a Likert scale.
• Quantified 'wanting' by measuring participant effort to alter stimulus viewing time.

Main Results:

• Right-lesion patients exhibited reduced viewing times and lower liking ratings for positive images.
• Right-lesion patients actively withdrew from sexual content, unlike other groups who approached it.
• Avoidance of disliked stimuli was preserved in both right- and left-lesion groups.

Conclusions:

• The right basal ganglia-insula complex plays a dominant role in hedonic evaluation and motivational approach to positive stimuli.
• Unilateral BG-I damage may not impair general incentive motivation independent of specific stimulus preferences.
• Findings highlight the lateralized neural basis of reward processing and motivated behavior.