Objectives: Cataplexy is the key symptom of the narcoleptic syndrome. It is usually triggered by emotions, which play an important role in the manifestation and severity of the disease. Accordingly, we compared the psychophysiologic effects on patients with narcolepsy and healthy subjects of processing visual stimuli that have established emotional valences.
Method: Eight drug-free patients with narcolepsy with severe cataplexy and 8 controls were studied. Fifty-four color pictures (pleasant, neutral, and unpleasant) selected from the International Affective Picture System were presented on a monitor to the subjects. The effects of exposure to the pictures were assessed in muscular (corrugator, zygomatic and mylohyoid electromyographic activity), autonomic (blood pressure, heart rate, and skin conductance responses) cognitive (scalp-recorded event-related potentials), and subjective (valence, arousal, and dominance by Self-Assessment Manikin) systems.
Results: The autonomic, muscular, and cognitive systems showed an attenuated reaction to visual stimuli in patients compared to controls. Furthermore, patients with narcolepsy showed the lowest responses when unpleasant pictures were presented.
Conclusions: Our data suggest that, compared to the group of healthy subjects, patients with narcolepsy suffer from a temporal disadvantage in input processing, in particular, of unpleasant stimuli. The drawback exhibited by these patients suggests reduced reactivity of the aversive motivational system responsible for negative or unpleasant emotions.