**4. Brain cortex volume in somnambulists**

Compared to age and gender-matched control group, in 14 drug-free polysomnographically confirmed adult somnambulists (age range 21–39 years), an MRI study reported by Heidbreder et al. [58] showed significant decreases of gray matter in the left dorsal posterior cingulate cortex and posterior midcingulate cortex. The mean disease duration of adult somnambulists was reported as 19.2 **±** 7.7 years (range 6–33 years). Though this finding is of interest, it remains to be replicated [59] in other sleep laboratories with children somnambulists as well. Whether children somnambulists also show similar significant gray matter decrease in the cingulate cortex areas deserves clarification. This is because, while the prevalence of somnambulism peaks in childhood, its percentage decreases in adulthood.
