Elevated perseveration errors on a verbal fluency task in frequent nightmare recallers: a replication

Summary A recent study reported that individuals recalling frequent idiopathic nightmares ( NM ) produced more perseveration errors on a verbal fluency task than did control participants ( CTL ), while not differing in overall verbal fluency. Elevated scores on perseveration errors, an index of executive dysfunction, suggest a cognitive inhibitory control deficit in NM participants. The present study sought to replicate these results using a French‐speaking cohort and French language verbal fluency tasks. A phonetic verbal fluency task using three stimulus letters (P, R, V) and a semantic verbal fluency task using two stimulus categories (female and male French first names) were administered to 23 participants with frequent recall of NM (≥2 NM per week, mean age = 24.4 ± 4.0 years), and to 16 CTL participants with few recalled NM (≤ 1 NM per month, mean age = 24.5 ± 3.8 years). All participants were French‐speaking since birth and self‐declared to be in good mental and physical health apart from their NM . As expected, groups did not differ in overall verbal fluency, i.e. total number of correct words produced in response to stimulus letters or categories ( P  = 0.97). Furthermore, groups exhibited a difference in fluency perseveration errors, with the NM group having higher perseveration than the CTL group ( P  = 0.03, Cohen's d  = 0.745). This replication suggests that frequent NM recallers have executive inhibitory dysfunction during a cognitive association task and supports a neurocognitive model which posits fronto‐limbic impairment as a neural correlate of disturbed dreaming.