Hi Folks
One idea is that you should always fit a statistical model that matches the
experimental design (regardless of the results of correlated behavioral
measurements).
Another solution to this issue is to partner behavioral-only studies with
studies using neuroimaging techniques. Many RT studies require large
samples to have sufficient statistical power, of a size too expensive for
imaging techniques. We can instead run the same paradigm in and outside of
the scanner, and assume that the tasks are fundamentally the same in both
settings. There are examples in the literature*. So in Greig's study,
perhaps you could run a behavioral-measures-only study with a larger N.
I wonder how tenable is the assumption that the tasks are the same in both
settings. I've had situations where people's behavior in the scanner was
dramatically different from their behavior in the lab. People seem to have
better concentration and motivation in the scanner, but also may have mood
effects (e.g., anxiety from getting injections, having to remain still,
mild claustrophobia...) as well as potential problems seeing/hearing the
stimuli in the scanning environment.
Best,
David
* I was just reading
Postle, BR, Berger, JS, Goldstein, JH, Curtis, CE, & D'Esposito, M. (in
press 2001) Behavioral and neurophysiological correlates of episodic
codeing, proactive interference, and list length effects in a running span
verbal working memory task. Cognitive Affective & Behavioral Neuroscience.
and a shameless self-plug:
Robertson, D. A., Gernsbacher, M. A., Guidotti, S. J., Robertson, R. R. W.,
Irwin, W., Mock, B. J., Campana, M. E. (2000). FMRI investigation of the
cognitive process of mapping during discourse comprehension. Psychological
Science, 11, 255-260.
>Dear all,
>
>I have a thorny question motivated by a reviewer's comments on one of our
>fMRI papers.
>
>Briefly, we used a memory task with variable delay periods. However, we did
>not find significant differences in terms of either accuracy or RT across
>the delays. Therefore, we did not look for an effect of delay in the fMRI
>data. The reviewer is requesting that we revise the paper to include this
>analysis.
>
>Does anyone know of any references addressing whether it's "good form" to
>perform analyses of neuroimaging data in the absence of a significant
>behavioural effect? Any views on this issue?
>
>Any help would be appreciated.
>
>Regards,
>
>Greig
>
>
>
>
>--
>Dr Greig de Zubicaray
>Centre for Magnetic Resonance
>The University of Queensland
>Brisbane, QLD 4072
>AUSTRALIA
>
>Tel: +61 (0) 7 3365 4250 [direct]
> +61 (0) 7 3365 4100 [CMR]
>Fax: +61 (0) 7 3365 3833
_________________________________
David Robertson <[log in to unmask]>
Assistant Professor (404) 894-0963 Voice
School of Psychology (404) 894-8905 FAX
Georgia Institute of Technology(404) 431-0901 Cell
Atlanta, GA 30332-0170
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