Reduced neural encoding of utility prediction errors in cocaine addiction

Area of Science:

• Neuroscience
• Addiction Research
• Computational Psychiatry

Background:

• Addiction is theorized to involve deficits in dopaminergic prediction errors (PEs), which signal discrepancies between expected and actual rewards.
• Dopamine neurons encode these signals as 'utility' PEs, influenced by individual risk preferences, but the source of PE deficits in addiction remains unclear.

Purpose of the Study:

• To investigate whether individuals with chronic cocaine addiction exhibit deficits in utility PEs.
• To identify the computational source of these potential prediction error deficits in the brain.

Main Methods:

• Utilized functional magnetic resonance imaging (fMRI) to measure brain activity during a task analogous to single-unit electrophysiology studies.
• Assessed prediction errors (PEs) reflecting subjective utility, comparing individuals with chronic cocaine addiction to control participants.

Main Results:

• Individuals with chronic cocaine addiction showed significantly reduced utility PEs in the ventral striatum compared to controls.
• Similar trends of reduced utility PEs were observed in the orbitofrontal cortex.
• The reduction in utility PEs was attributed to weaker striatal responses to received reward/utility, not altered responses to reward expectation.

Conclusions:

• Addiction may fundamentally disrupt prediction error signaling in the brain's reward circuitry.
• Perceived reward value plays a critical, underappreciated role in the neurobiological mechanisms underlying addiction.