Fig. 4

Comparison of REM activations in individuals with insomnia versus without insomnia. When comparing REM to wake, there is a greater increase in regional cerebral glucose metabolism (¹⁸fluoro-deoxyglucose PET) in an anterior midline region in close proximity to the region of the dACC that has been associated with fear expression (a). However, in a comparison of two different groups, the insomnia group showed lesser increase in the vmPFC, an area associated with the memory and expression of fear extinction (b)