RESUMO
Research on addiction suggests that emotional alterations play an essential role in the development, maintenance, relapse and treatment outcome of substance abuse disorders. Although many neuroimaging studies focussed on the neural response to conditioned stimuli, much less is known about the neural response to natural affective stimuli in this pathological population. Previous research has demonstrated an altered emotional experience and autonomic response to emotional stimuli using the International Affective Picture System (IAPS) in drug abusers. Here we aimed, using functional magnetic resonance imaging (fMRI), to study the alterations in the neural responsitivity to pleasant (erotic), unpleasant and neutral IAPS stimuli in cocaine addiction. Thirty-two cocaine-dependent subjects and 26 matched controls completed an fMRI session during the presentation of a set of IAPS pictures as background, while performing a letter discrimination task. Consistent with previous studies, emotional pictures activated an emotional network including amygdala, medial prefrontal cortex, orbitofrontal cortex and occipito-temporal areas in both groups. However, compared with controls, the cocaine group showed a significant hypoactivation of the dorsal and ventral striatum (including the nucleus accumbens), thalamus, parietal cortex and dorso-medial prefrontal cortex (dmPFC) when processing pleasant pictures. The analysis of pleasant versus unpleasant stimuli suggested that between-group differences in the dmPFC and striatal activation may be attributed to arousal processing rather than valence. These results could reflect the neural basis for the reduced ability of cocaine-dependent subjects to experience pleasure by daily natural reinforcers, suggesting that these alterations in the emotion processing may play an important role in drug dependence, treatment and relapse.
Assuntos
Comportamento Apetitivo/efeitos dos fármacos , Comportamento Apetitivo/fisiologia , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Transtornos Relacionados ao Uso de Cocaína/fisiopatologia , Cocaína/efeitos adversos , Condicionamento Operante/efeitos dos fármacos , Condicionamento Operante/fisiologia , Emoções/efeitos dos fármacos , Emoções/fisiologia , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Consumo de Oxigênio/fisiologia , Reconhecimento Visual de Modelos/efeitos dos fármacos , Reconhecimento Visual de Modelos/fisiologia , Adulto , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/fisiologia , Gânglios da Base/efeitos dos fármacos , Gânglios da Base/fisiopatologia , Mapeamento Encefálico , Transtornos Relacionados ao Uso de Cocaína/psicologia , Discriminação Psicológica/efeitos dos fármacos , Discriminação Psicológica/fisiologia , Lobo Frontal/efeitos dos fármacos , Lobo Frontal/fisiopatologia , Humanos , Masculino , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/fisiopatologia , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/fisiopatologia , Lobo Parietal/efeitos dos fármacos , Lobo Parietal/fisiopatologia , Prazer/efeitos dos fármacos , Prazer/fisiologia , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/fisiopatologia , Valores de Referência , Tálamo/efeitos dos fármacos , Tálamo/fisiopatologia , Adulto JovemRESUMO
Inferior frontal and anterior cingulate white matter integrity in 32 cocaine-dependent subjects was compared with that in 33 age-matched healthy control subjects. Diffusion tensor imaging data were acquired with a 1.5-T magnetic resonance imaging system. Cocaine-dependent subjects presented significantly lower fractional anisotropy values in inferior frontal white matter at the anterior-posterior commissure plane and higher anterior cingulate white matter values than control subjects. White matter integrity was also associated with impulsivity and motivation to change (Readiness to Change Questionnaire). These findings support the hypothesis that cocaine dependence involves a disruption of orbitofrontal connectivity and suggest that the anterior cingulate brain area might play a role in the motivation to change.
