This thesis unveils the study we accomplished with patients suffering from nightmare disorder, a psychiatric disorder characterized by dreams with strong negative emotions occurring in rapid-eye-movement sleep. Nightmares can be conceived as dysfunctional dreams, a phenomenon deprived from efficient adaptive emotional processes. A common treatment for nightmare disorder is imagery rehearsal therapy, a cognitive-behavioral technique that consists in changing the storyline of a nightmare towards a less negative scenario. Previous work has shown that imagery rehearsal therapy is most efficient for individuals having nightmares in which distress can be monitored and further regulated. In the present clinical study, we further investigated the effects of targeted memory reactivation technique, as a new tool empowering IRT for an accelerated remission of nightmare disorder. The goal of the present clinical study is to train our patients for better emotion regulation through fear extinction, using targeted memory reactivation in rapid-eye-movement sleep to facilitate such process. In total, thirty-six patients with nightmare disorder were recruited; half of them received imagery rehearsal therapy as a main treatment (control group), while the other half benefitted from imagery rehearsal therapy associated with targeted memory reactivation (targeted memory reactivation group). Every night for two weeks, both groups practiced imagery rehearsal therapy before sleep, during which the targeted memory reactivation group received a sound, whereas the control group didn’t associate any sound to the imagery. Both groups then received the auditory stimulus during rapid-eye movement sleep over two weeks. Our results show that the targeted memory reactivation group had significantly less frequent nightmares, as well as a greater proportion of positive emotions in their dreams compared to the control group. Such improvement was sustained three months after intervention. Targeted memory reactivation potentiated nightmare disorder treatment by boosting the imagery rehearsal therapy effects. To date, no other study used imagery rehearsal therapy associated with targeted memory reactivation to treat nightmares. Our results encourage future studies to test the efficacy of this treatment on different patient populations, namely on patients suffering from post-traumatic stress disorder