title: Olfactory performance acts as a cognitive reserve in non-demented patients with Parkinson's disease.
abstract: OBJECTIVE
  To explore whether olfactory performance acts as a cognitive reserve in non-demented patients with Parkinson's disease (PD).
  
  
  METHODS
  Patients with non-demented PD (n = 119) underwent T1-weighted MRI and olfactory identification tests. According to their olfactory performance, PD patients were subdivided into three groups of high score (PD-H, n = 38), middle score (PD-M, n = 48), and low score (PD-L, n = 33). We investigated the pattern of gray matter (GM) density according to olfactory performance using voxel-based morphometry (VBM) and analyzed the correlation between GM density and olfactory performance.
  
  
  RESULTS
  No significant differences in demographic characteristics were observed among the groups. A neuropsychological test showed that cognitive deficits in verbal memory function were more severe in the PD-L group than in the PD-H group. However, a VBM analysis revealed that patients in the PD-H group possessed significantly decreased GM density in the bilateral temporal areas, orbitofrontal areas, mesiofrontal areas extending into the cingulate gyrus, and prefrontal areas, compared with patients in the PD-L group. No areas exhibiting a significant difference in GM density were observed between the PD-H and PD-M groups. Olfactory performance in patients with PD was negatively correlated with both the brain GM volume and intracerebral volume; in particular, GM density in the caudate nucleus and putamen exhibited a negative correlation with olfactory performance.
  
  
  CONCLUSIONS
  Our data show that a high olfactory performance may compensate GM volume loss in order to minimize the exhibition of cognitive impairment and thus may act as a cognitive reserve in non-demented patients with PD.
authors.affiliation: Department of Neurology and Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Ji E
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Neurology and Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Kyoo H
authors.initials: KH
authors.lastname: Cho
authors.affiliation: Department of Neurology and Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Jee Hyun
authors.initials: JH
authors.lastname: Ham
authors.affiliation: Department of Neurology, Jeju University College of Medicine, Jeju, South Korea.
authors.forename: Sook K
authors.initials: SK
authors.lastname: Song
authors.affiliation: Department of Neurology and Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Young H
authors.initials: YH
authors.lastname: Sohn
authors.affiliation: Department of Neurology and Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea; Severance Biomedical Science Institute, Seoul, South Korea. Electronic address: phisland@chol.net.
authors.forename: Phil Hyu
authors.initials: PH
authors.lastname: Lee
mesh_terms: D000368:Aged; D003071:Cognition / Q000502:physiology; D058245:Cognitive Reserve / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000473:pathology* / Q000503:physiopathology*; D012903:Smell / Q000502:physiology*
keywords: Cognitive reserve; Olfaction; Parkinson's disease; Voxel-based morphometry