Subjective sensitivity to monetary gradients is associated with frontolimbic activation to reward in cocaine abusers

Drug addiction is characterized by marked disruptions in the ability to process reward. Here we evaluated in cocaine addicted and healthy control participants the subjective sensitivity to reward gradients and its association with neural responses to sustained reward. A self-report questionnaire was used to assess the former. A functional magnetic resonance imaging task that utilized monetary reward as feedback in a blocked design was used to assess the latter. Results revealed that whereas control subjects valued high money more than low money, over half of the cocaine addicted subjects valued all monetary amounts equally. This compromised subjective sensitivity to gradients in reward value was significantly correlated with higher activations to money in the lateral orbitofrontal cortex/inferior frontal gyrus (BA 47) and amygdala, and lower activations in the middle frontal gyrus (BA 6), which together explained 85% of the variability on this rating scale in the cocaine abusers only. These results provide for the first time evidence of restricted subjective sensitivity to gradients of reward in cocaine addiction and of the involvement of frontolimbic brain regions (including the orbitofrontal cortex) in this deficit.