Dear SPM experts: 

  Our group is interested in determining the extent to which results from 
  previous exploratory PET studies of hunger, satiation and taste
(n=11) is  reproducible in an independent group of 11 subjects who were studied
using  the identical image-acquisition and image-analysis procedures. 

  Before we analyze the second data set, we wanted to have clear criteria 
  for replication. We were thinking of generating SPM's in the second 
  data set, and over-lapping the results of the second study with those 
  from the first.  Those areas associated with significant activations in
both 
  data sets would be considered replicated findings.  We don't think we
can say 
  much about those regions associated with increased activity in only one 
  of the two studies other than that we failed to replicate these
findings, 
  since we probably don't have the statistical power to refute changes in
these 
  regions. 

  Does that make sense to you?  What have been the criteria used in 
  previous studies to confirm previous findings from the same
laboratory?  What 
  would be the criteria to disconfirm a previous finding given our
limiations in 
  statistical power?  Since we have replication data--a nice way to 
  address the problem of multiple comparisons, how liberal can we
logically make 
  the statistical threshold for each of the statistal maps (e.g., .05,
.01, 
  .005, etc)?  And does it make sense not to make too much of any negative 
  findings (given limitations in statistical power), or should we consider 
  additional means to say with some power that a particular finding was
disconfirmed? 

Many Thanks, 

Kewei


  References: 

  1. Tataranni PA, et al. Neuroanatomical correlates of hunger and 
  satiation in humans using positron emission tomography. PNAS
1999; 96: 4569-4574. 
  2. Gautier J-F, et al. Regions of the human brain affected during a 
  liquid-meal taste perception in the fasting state: a positron emission 
  tomography study. Am J Clin Nutr 1999; 70: 806-810. 
  3. Gautier JF, et al. Differential brain responses to satiation in obese 
  and lean men. Diabetes 2000 (in press). 




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