Maladaptive dopaminergic mediation of reward processing in humans is thought to underlie multiple neuropsychiatric disorders, including addiction, Parkinson's disease, and schizophrenia. Mechanisms responsible for the development of such disorders may depend on individual differences in neural signaling within large-scale cortico-subcortical circuitry. Using a combination of functional neuroimaging and pharmacological challenges in healthy volunteers, we identified opposing dopamine agonistic and antagonistic neuromodulatory effects on distributed functional interactions between specific subcortical regions and corresponding neocortical "resting-state" networks, known to be involved in distinct aspects of cognition and reward processing. We found that, relative to a placebo, levodopa and haloperidol challenges, respectively, increased or decreased the functional connectivity between (1) the midbrain and a "default mode" network, (2) the right caudate and a right-lateralized frontoparietal network, and (3) the ventral striatum and a fronto-insular network. Further, we found drug-specific associations between brain circuitry reactivity to dopamine modulation and individual differences in trait impulsivity, revealing dissociable drug-personality interaction effects across distinct dopamine-dependent cortico-subcortical networks. Our findings identify possible systems underlying pathogenesis and treatment efficacy in disorders of dopamine deficiency.

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In this study, modulation of spinal tendinous (T) reflexes by sexual stimulation was investigated. T reflexes are augmented in states of appetitive and defensive action and modified by differences in arousal intensity. Reflexes were expected to be facilitated by both pleasant (sexual) and unpleasant (anxiety) stimuli. Subjects were exposed to a sexual, an anxiety-inducing, a sexually threatening, and a neutral film excerpt. Genital arousal, emotional experience, subjective action tendencies, and T reflexes were monitored. Self-report and genital data confirmed the affective states as intended. T reflex amplitude significantly increased during viewing of emotionally arousing film excerpts as compared with a neutral film excerpt. T reflexes were facilitated by the sex stimulus to the same extent as by the anxiety and sexual threat stimuli. The results support the view of sexual arousal as an emotional state, generating sex-specific autonomic and general somatic motor system responses, which prepare the organism for action.

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Sexual excitement can be seen as an action disposition. In this study sexual arousal was expected to generate sexual action and to increase interest and responsiveness to sexual stimuli. In two experiments, male and female participants were exposed to a neutral or a sexual film. We measured genital and subjective responses to the film, and sexual behavior following the laboratory visit. In Experiment 2, film exposure was followed by a task in which participants rated the sexual arousability of neutral and sexual pictures. Rating time of the sexual pictures served as an index for sexual interest. Responsiveness to the sexual pictures was measured by modulation of spinal tendinous (T) reflexes. Sexual activity, but not sexual desire, was higher for participants in the sexual film condition than for participants in the neutral condition. Sexual interest and responsiveness to still pictures were not higher for participants in the sexual film condition than for those in the neutral film condition. In addition, men who saw the neutral film showed a greater responsiveness to still pictures than men who saw the sexual film. The results support the view of sexual arousal as an emotional state generating action tendencies and actual sexual behavior.