I think, therefore I forget - using experimental simulation of dementia to understand functional cognitive disorders.

Background: Symptoms of functional neurological disorder have traditionally been thought to depend, in part, on patients' ideas about symptoms rather than on the rules of pathophysiology. The possibility that functional cognitive symptoms might similarly reflect ideas of dementia has not been explored. We aimed to assess beliefs, through performance, about symptoms of dementia in healthy non-medical adults with the intention of identifying potential markers of functional cognitive disorders.

Methods: Healthy volunteers were asked to simulate symptoms of mild dementia during testing with the Montreal Cognitive Assessment (MoCA), coin-in-hand forced-choice test, short digit span trials, Luria 3-step test and interlocking finger test. Family history of dementia was recorded.

Results: In 50 participants aged 18-27, simulating dementia, mean MoCA score was 16 (SD 5.5, range 5-26). Delayed recall was the most frequently failed item (100%) and cube drawing least frequently failed (42%). Twenty-six percent failed forward three-digit span and 36% failed reverse two-digit span. On the coin-in-hand test, 32% scored at or below chance level. Inconsistent response patterns were common.

Conclusions: Cognitively healthy young adults simulating mild dementia perform similarly to older adults with mild dementia, demonstrating beliefs that dementia is associated with significant global impairment, including attention, motor function, and letter vigilance, but preservation of cube drawing. Inconsistent response patterns were common. Contrary to expectation, family history of dementia did not influence performance. Two and three digit span showed particular promise as a bedside test for simulation. Further investigation will establish whether similar patterns of results are produced in individuals with functional cognitive symptoms.