Impaired executive functions in subjects with frequent nightmares as reflected by performance in different neuropsychological tasks.

People who frequently experience nightmares show measurable impairments in certain thinking tasks during the day, particularly those requiring suppression of irrelevant information. In two studies, nightmare subjects were slower on emotional Go/NoGo and Stroop tasks, made more perseveration errors, and generated fewer words on a verbal fluency task compared to matched controls. These deficits appeared as an overall slowing regardless of whether the stimuli were emotionally positive, negative, or neutral. Poor sleep quality and waking anxiety accounted for some but not all of the differences. The findings suggest that frequent nightmares are linked to executive function difficulties involving the control of task-irrelevant semantic information.

Study at a glance

Abstract

Nightmare disorder is a prevalent parasomnia characterized by vivid and highly unpleasant dream experiences during night time sleep. The neural background of disturbed dreaming was proposed to be associated with impaired prefrontal and fronto-limbic functioning during REM sleep. We hypothesized that the impaired prefrontal and fronto-limbic functioning in subjects with frequent nightmares would be reflected at the behavioral level during waking tasks as well. 35-35 Subjects with frequent nightmares and matched controls participated in Study 1, involving an Emotional Go/NoGo, an Emotional Stroop task, and a Verbal Fluency task. Nightmare subjects exhibited longer reaction times in the Emotional Go/NoGo and Emotional Stroop tasks. Moreover, they committed more perseveration errors and showed less fluent word generation in the Verbal Fluency task. Nightmare subjects showed an overall slowing irrespective of the valence of the stimuli. While the effects of sleep quality and waking anxiety were associated to these deficits in some cases, these factors could not solely explain the difference between the two groups. In Study 2, 17 subjects with frequent nightmares and 18 controls were compared by a Color-word and an Emotional, block design Stroop task in order to avoid the slow effects of emotional interference potentially caused by previous items. Nightmare subjects were characterized by an overall slowing in the Emotional Stroop task, irrespective of the valence of the stimuli. In the Color-word Stroop task, nightmare subjects were not significantly slower in comparison with controls. Our results suggest that individuals with frequent nightmares are impaired in executive tasks involving the suppression of task-irrelevant semantic representations.