But do you really think you can trust their interpretations of the MRI data?
What about the
MRI scanning of the dead salmon?
Subject. One mature Atlantic Salmon (Salmo salar) participated in the fMRI study.
The salmon was approximately 18 inches long, weighed 3.8 lbs, and was not alive at
the time of scanning.
Task. The task administered to the salmon involved completing an open-ended
mentalizing task. The salmon was shown a series of photographs depicting human
individuals in social situations with a specified emotional valence. The salmon was
asked to determine what emotion the individual in the photo must have been
experiencing.
Can we conclude from this data that the salmon is engaging in the
perspective-taking task? Certainly not. What we can determine is that random
noise in the EPI timeseries may yield spurious results if multiple comparisons
are not controlled for. Adaptive methods for controlling the FDR and FWER
are excellent options and are widely available in all major fMRI analysis
packages. We argue that relying on standard statistical thresholds (p < 0.001)
and low minimum cluster sizes (k > 8) is an ineffective control for multiple
comparisons. We further argue that the vast majority of fMRI studies should
be utilizing multiple comparisons correction as standard practice in the
computation of their statistics.
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http://www.ncbi.nlm.nih.gov/pubmed/23967214
Sandeman EM,
Hernandez Mdel C,
Morris Z,
Bastin ME,
Murray C,
Gow AJ,
Corley J,
Henderson R,
Deary IJ,
Starr JM,
Wardlaw JM.
Source
Brain Research Imaging Centre, Division of Clinical Neurosciences, University of Edinburgh, Edinburgh, United Kingdom.
Abstract
OBJECTIVES:
Incidental
findings in neuroimaging occur in 3% of volunteers. Most data come from
young subjects. Data on their occurrence in older subjects and their
medical, lifestyle and financial consequences are lacking. We determined
the prevalence and medical consequences of incidental findings found in
community-dwelling older subjects on brain magnetic resonance imaging.
DESIGN:
Prospective cohort observational study.
SETTING:
Single centre study with input from secondary care.
PARTICIPANTS:
Lothian Birth Cohort 1936, a study of cognitive ageing.
MAIN OUTCOME MEASURES:
Incidental
findings identified by two consultant neuroradiologists on structural
brain magnetic resonance imaging at age 73 years; resulting medical
referrals and interventions.
PRIMARY AND SECONDARY OUTCOME MEASURES:
PREVALENCE
OF INCIDENTAL FINDINGS BY INDIVIDUAL CATEGORIES: neoplasms, cysts,
vascular lesions, developmental, ear, nose or throat anomalies, by
intra- and extracranial location; visual rating of white matter
hyperintensities and brain atrophy.
RESULTS:
There were
281 incidental findings in 223 (32%) of 700 subjects, including 14
intra- or extracranial neoplasms (2%), 15 intracranial vascular
anomalies (2%), and 137 infarcts or haemorrhages (20%). Additionally,
153 had moderate/severe deep white matter hyperintensities (22%) and 176
had cerebral atrophy at, or above, the upper limit of normal (25%)
compared with a normative population template. The incidental findings
were unrelated to white matter hyperintensities or atrophy; about a
third of subjects had both incidental findings and moderate or severe
WMH and a quarter had incidental findings and atrophy. The incidental
findings resulted in one urgent and nine non-urgent referrals for
further medical assessment, but ultimately in no new treatments.
CONCLUSIONS:
In
community-dwelling older subjects, incidental findings, including white
matter hyperintensities and atrophy, were common. However, many
findings were not of medical importance and, in this age group, most did
not result in further assessment and none in change of treatment.
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