Absence of residual effects after physiological stimulation of the visual and motor cortex: an [15O]-H2O PET study in humans.
Cognitive experiments using positron emission tomography (PET) with [15O]-H2O require multiple scans done at 10 to 12 min intervals. Momose and colleagues reported that regional cerebral blood flow changes in response to visual stimulation do not return to baseline even 15 min after the stimulation. If confirmed, this fact would have important implications for the design and interpretation of PET cognitive studies. The purpose of this study was to determine the temporal course of residual effects following visual and motor stimulation. Six healthy volunteers undertook six scans each. Two scans were done to establish a baseline, one to observe the task induced activation, and three scans to investigate the residual effects at varying intervals after the task. The data were analysed using both statistical parametric mapping and a region of interest analysis. The visual and motor task produced robust activations bilaterally in the occipital cortex and in the contralateral primary motor cortex. There was no evidence for a statistically significant residue effect at any of the three intervals studied (30 s, 3 and 6 min). Our results refute the findings of Momose and colleagues and suggest that the 10-min interscan interval is more than adequate to re-establish a resting baseline.
Houle
S
S
PET Centre, Clarke Institute of Psychiatry, Toronto, ON, Canada.
Kapur
S
S
Rose
R
R
Hussey
D
D
Wilson
D
D
D000328:Adult; D002560:Cerebrovascular Circulation; D006801:Humans; D009044:Motor Cortex / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000502:physiology; D010104:Oxygen Radioisotopes; D010775:Photic Stimulation; D012016:Reference Values; D012039:Regional Blood Flow; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods; D014793:Visual Cortex / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000502:physiology; D014867:Water
D010104:Oxygen Radioisotopes; D014867:Water