Symposium: Cognitive processes and sleep disturbances: The disturbance of cognitive processes in narcolepsy

Neuropsychological methods have been applied by different authors to investigate cognitive processes such as attention, information processing, memory and psychomotor performance in narcoleptic patients. A review of the results strongly suggests that cognitive processes in narcoleptic patients are not impaired on a functional but only on a temporal level. Providing that short and challenging tasks were used, the performance of narcoleptic patient did not differ significantly from that of healthy subjects. Performance was impaired mainly when a low and monotonous information input had to be processed, a situation which is typical for tests of vigilance. This was supported by this study measuring critical flicker fusion (CFF) at 15-min intervals for 10 hours in 10 narcoleptic patients and matched healthy controls. While peak performance did not differ between groups, narcoleptic patients were unable to perform at a steady level through the day. Tiredness and episodes of sleepiness seem to be the main reason for cognitive impairments in narcolepsy.