title: Necker cube copying may not be appropriate as an examination of dementia: reanalysis from the Tajiri Project.
abstract: BACKGROUND
  The Necker cube is usually used for evaluating the visuoconstructional ability of patients with mild cognitive impairment (MCI) and dementia. However, the Necker cube is often considered a drawing with a visual illusionary perspective. The purpose of this study was to investigate whether Necker cube copying could detect participants with MCI due to dementia.
  
  
  METHODS
  We retrospectively analyzed the database of the 1998 prevalence study that was part of the Tajiri Project (n = 599). Pencil drawings of the Necker cube on A4-sized white paper by non-demented people (Clinical Dementia Rating (CDR) 0 and 0.5, n = 256) were classified into two patterns: non-three-dimension (3-D) and 3-D. Two neuropsychologists assessed Necker cube copying according to the criteria of the classification. After the classification, the database of the 2003 incidence study was used according to the subjects' conversion to dementia.
  
  
  RESULTS
  In the prevalence study, among those who made a non-3-D drawing of the Necker cube, there were significantly fewer people in the CDR 0 group than in the CDR 0.5 and CDR 1+ groups; similarly, there were significantly fewer people in the CDR 0.5 group than in the CDR 1 + group (χ(2) = 32.6, P < 0.001; post-hoc tests using χ(2) tests, CDR 0 > CDR 0.5 > CDR 1+, P < 0.001). In the incidence study, among those who made a non-3-D drawing of the Necker cube, there were significantly fewer people in the non-converter group than in the converter group (χ(2) = 19.9, P < 0.001). However, there was no significant difference between the non-converter group (n = 21) and the converter group (n = 21) when age, sex, educational levels, and Mini-Mental State Examination scores were controlled (χ(2) = 0.0, P = 1.000).
  
  
  CONCLUSIONS
  Our results suggested that Necker cube copying may evaluate visual illusion as well as visuoconstructional ability. The Necker cube may not be an appropriate test to detect participants with MCI due to dementia.
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Oonuma
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Kasai
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan.
authors.forename: Mitsue
authors.initials: M
authors.lastname: Meguro
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Akanuma
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Division of Geriatric Behavioral Neurology, CYRIC, Tohoku University, Sendai, Japan. k-meg@umin.ac.jp.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Meguro
mesh_terms: D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis*; D060825:Cognitive Dysfunction / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D003430:Cross-Sectional Studies; D003704:Dementia / Q000150:complications / Q000453:epidemiology / Q000523:psychology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D015995:Prevalence; D011569:Psychiatric Status Rating Scales; D012189:Retrospective Studies; D012720:Severity of Illness Index
keywords: Necker cube; copying; dementia; mild cognitive impairment; visuoconstructional