title: Abnormal activity in the precuneus during time perception in Parkinson's disease: an fMRI study.
abstract: BACKGROUND
  Parkinson's disease (PD) patients are deficient in time estimation. This deficit improves after dopamine (DA) treatment and it has been associated with decreased internal timekeeper speed, disruption of executive function and memory retrieval dysfunction.
  
  
  RESULTS
  The aim of the present study was to explore the neurophysiologic correlates of this deficit. We performed functional magnetic resonance imaging on twelve PD patients while they were performing a time reproduction task (TRT). The TRT consisted of an encoding phase (during which visual stimuli of durations from 5 s to 16.6 s, varied at 8 levels were presented) and a reproduction phase (during which interval durations were reproduced by a button pressing). Patients were scanned twice, once while on their DA medication (ON condition) and once after medication withdrawal (OFF condition). Differences in Blood-Oxygenation-Level-Dependent (BOLD) signal in ON and OFF conditions were evaluated. The time course of activation in the brain areas with different BOLD signal was plotted. There were no significant differences in the behavioral results, but a trend toward overestimation of intervals ≤11.9 s and underestimation of intervals ≥14.1 s in the OFF condition (p<0.088). During the reproduction phase, higher activation in the precuneus was found in the ON condition (p<0.05 corrected). Time course was plotted separately for long (≥14.1 s) and short (≤11.9 s) intervals. Results showed that there was a significant difference only in long intervals, when activity gradually decreased in the OFF, but remained stable in the ON condition. This difference in precuneus activation was not found during random button presses in a control task.
  
  
  CONCLUSIONS
  Our results show that differences in precuneus activation during retrieval of a remembered duration may underlie some aspects of time perception deficit in PD patients. We suggest that DA medication may allow compensatory activation in the precuneus, which results in a more accurate retrieval of remembered interval duration.
authors.affiliation: Department of Neurology and Center of Clinical Neuroscience, Charles University in Prague, 1st Faculty of Medicine and General University Hospital, Prague, Czech Republic. pdusek@gmail.com
authors.forename: Petr
authors.initials: P
authors.lastname: Dušek
authors.forename: Robert
authors.initials: R
authors.lastname: Jech
authors.forename: Tomáš
authors.initials: T
authors.lastname: Sieger
authors.forename: Josef
authors.initials: J
authors.lastname: Vymazal
authors.forename: Evžen
authors.initials: E
authors.lastname: Růžička
authors.forename: Jiří
authors.initials: J
authors.lastname: Wackermann
authors.forename: Karsten
authors.initials: K
authors.lastname: Mueller
mesh_terms: D000368:Aged; D001519:Behavior / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008568:Memory; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010296:Parietal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000523:psychology; D011597:Psychomotor Performance / Q000502:physiology; D011859:Radiography; D013998:Time Perception / Q000502:physiology*