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Cocaine addiction is characterized by alterations in motivational and cognitive processes. Recent studies have shown that some alterations present in cocaine users may be related to the activity of large functional networks. The aim of this study was to investigate how these functional networks are modulated by non-drug rewarding stimuli in cocaine-dependent individuals. Twenty abstinent cocaine-dependent and 21 healthy matched male controls viewed erotic and neutral pictures while undergoing a functional magnetic resonance imaging scan. Group independent component analysis was then performed in order to investigate how functional networks were modulated by reward in cocaine addicts. The results showed that cocaine addicts, compared with healthy controls, displayed diminished modulation of the left frontoparietal network in response to erotic pictures, specifically when they were unpredicted. Additionally, a positive correlation between the length of cocaine abstinence and the modulation of the left frontoparietal network by unpredicted erotic images was found. In agreement with current addiction models, our results suggest that cocaine addiction contributes to reduce sensitivity to rewarding stimuli and that abstinence may mitigate this effect.

The chance to achieve a reward starts up the required neurobehavioral mechanisms to adapt our thoughts and actions in order to accomplish our objective. However, reward does not equally reinforce everybody but depends on interindividual motivational dispositions. Thus, immediate reward contingencies can modulate the cognitive process required for goal achievement, while individual differences in personality can affect this modulation. We aimed to test the interaction between inhibition-related brain response and motivational processing in a stop signal task by reward anticipation and whether individual differences in sensitivity to reward (SR) modulate such interaction. We analyzed the cognitive–motivational interaction between the brain pattern activation of the regions involved in correct and incorrect response inhibition and the association between such brain activations and SR scores. We also analyzed the behavioral effects of reward on both reaction times for the “go” trials before and after correct and incorrect inhibition in order to test error prediction performance and postinhibition adjustment. Our results show enhanced activation during response inhibition under reward contingencies in frontal, parietal, and subcortical areas. Moreover, activation of the right insula and the left putamen positively correlates with the SR scores. Finally, the possibility of reward outcome affects not only response inhibition performance (e.g., reducing stop signal reaction time), but also error prediction performance and postinhibition adjustment. Therefore, reward contingencies improve behavioral performance and enhance brain activation during response inhibition, and SR is related to brain activation. Our results suggest the conditions and factors that subserve cognitive control strategies in cognitive motivational interactions during response inhibition.

Pre-clinical and clinical studies in cocaine addiction highlight alterations in the striatal dopaminergic reward system that subserve maintenance of cocaine use. Using an instrumental conditioning paradigm with monetary reinforcement, we studied striatal functional alterations in long-term abstinent cocaine-dependent patients and striatal functioning as a function of abstinence and treatment duration. Eighteen patients and 20 controls underwent functional magnetic resonance imaging during a Monetary Incentive Delay task. Region of interest analyses based on masks of the dorsal and ventral striatum were conducted to test between-group differences and the functional effects in the cocaine group of time (in months) with no more than two lapses from the first time patients visited the clinical service to seek treatment at the scanning time (duration of treatment), and the functional effects of the number of months with no lapses or relapses at the scanning session time (length of abstinence). We applied a voxel-wise and a clusterwise FWE-corrected level (pFWE) at a threshold of P < 0.05. The patient group showed lower activation in the right caudate during reward anticipation than the control group. The regression analyses in the patients group revealed a positive correlation between duration of treatment and brain activity in the left caudate during reward anticipation. Likewise, length of abstinence negatively correlated with brain activity in the bilateral nucleus accumbens during monetary outcome processing. In conclusion, caudate and nucleus accumbens showa different brain response pattern to non-drug rewards during cocaine addiction, which can be modulated by treatment success.

Setzenes Jornades de Foment de la Investigació (Any 2011) El consumo crónico de tabaco se ha asociado a reducciones en el volumen global del cerebro y a una ejecución más pobre en tareas que implican funciones ejecutivas. En estudios previos, el consumo de tabaco se ha asociado a reducciones en el volumen y la densidad de sustancia gris en regiones prefrontales y el cingulado anterior. El objetivo de este trabajo fue estudiar los cambios en el volumen cerebral regional asociados al consumo de tabaco en población normal. Se adquirieron imágenes anatómicas de resonancia magnética en 3D de todo el cerebro en una muestra de adultos jóvenes (N=63), que fue dividida en dos grupos en función del consumo de tabaco (fumadores y no fumadores). Las imágenes se analizaron mediante morfometría basada en el vóxel, comparando ambos grupos. En el grupo de fumadores, se estudió también el volumen regional de sustancia gris en relación al tiempo de consumo (años de consumo habitual de tabaco) y a la cantidad de cigarrillos consumidos por semana. El grupo de fumadores mostró un menor volumen en el córtex orbitofrontal medial y en el cingulado posterior respecto al grupo de no fumadores. Los años de consumo se asociaron con incrementos de volumen en el lóbulo temporal inferior y con decrementos en el giro frontal superior y el giro frontal medio del hemisferio izquierdo y la ínsula derecha. El número de cigarrillos fumados por semana se asoció a reducciones en el giro precentral y el lóbulo temporal inferior. Estos resultados sugieren la existencia de diferencias en la estructura cerebral entre fumadores y no fumadores en regiones asociadas al control ejecutivo y en otras regiones más directamente asociadas a la conducta adictiva, lo que puede tener implicaciones en el tratamiento del tabaquismo.