Hi Mark,
A task-based multivariate analysis method like fMRI-CPCA, which uses a
FIR model, displays both the peak timing of the hemodynamic response
as well as the magnitude of the peak for a given network. One or more
networks will likely involve the DLPFC (the analysis could also be
restricted to the DLPFC but then you wouldn't know which other areas
work with it). If the peak for old adults is later than that for young
adults, but not lower, and RTs were longer, this may be due to slower
RTs and/or sluggish BOLD signal. But, depending on the component, some
are linked to RT and some are not. If all HDRs are late for all
components you know it's HDR shape sluggishness. If only the
response-linked ones are slow you know it's RT. If it's lower but not
later, this would correspond to reduced coordinated activity in that
netowork, not RT differences or BOLD sluggishness. If it's both lower
and later, this could still be interpreted in a number of ways based
on what I mentioned above.
Cheers,
Todd
links:
https://www.nitrc.org/projects/fmricpca
http://www.cnoslab.com/pdfs/reduced_functional_connectivity.pdf
http://www.cnoslab.com/pdfs/functional-brain-networks.pdf
http://www.cnoslab.com/functionalconnectivity.html
http://www.cnoslab.com/cpca.html
On Fri, Oct 9, 2015 at 12:34 PM, Mark bl <[log in to unmask]> wrote:
> Hello SPM list,
> I have two group of participants: old adults ( above 60 years) and young
> adults ( 18-40 years). I am intrested on how DLPFC activity changes due to
> task A between old and young adults. I have significant DLPFC in younger
> adult compared to older during task A. Now we want to conform that the
> significant DLPFC activity in young adult is due to the cognitive demand of
> task but not due to the sluggish BOLD response in older adult compared to
> young adult (I am mainly talking about HRF convolution ). Any suggestion
> regarding this is highly appreciated.
> Thanks
> Mark
--
Todd S. Woodward, Ph.D.
Cognitive Neuroscience of Schizophrenia Lab (CNoS)
http://www.cfri.ca/our-research/researchers/results/Details/todd-woodward
http://www.cnoslab.com/donate.html
604-875-2000 x4724
*****
Associate Professor
Department of Psychiatry
University of British Columbia
BC Mental Health and Addiction Research Institute
Vancouver, Canada
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