Hello.
Many thanks for taking the time to reply Linda.
To clarify for the list what I meant...
Whilst the actual sampling rate of fMRI measures is limited it is
possible to further reduce the effective sampling rate.
By staggering the timing of stimulus presentation relative to the timing
of image acquisition, reconstructed signals can be produced with a
shorter effective sampling rate than is implied by the actual TR
E.g. stimuli are presented every 5 seconds, and the signal is sampled
(TR) every 3 seconds.
The first sample is at zero seconds relative to the onset of the first
stimuli, the second sample is at three seconds, the third sample is at
one second relative to the onset of the second stimuli, etc.
Thus, over the course of an experiment signals will, in effect, be
acquired every second relative to the onset of the stimuli (Josephs et
al. 1997).
(Thank-you Donaldson & Bucker, 2000)
Thanks again everybody
Rachel
*************************************************************
Dr. Rachel L. C. Mitchell,
Lecturer in Psychology, Durham University.
Honorary Senior Research Fellow, Institute of Psychiatry, KCL.
Correspondence Address:
Dept. of Psychology,
Durham University,
Science Site,
South Road,
Durham,
Co. Durham.
DH1 3LE.
U.K.
Phone +44 (0)191 334 3272
Fax +44 (0)191 334 3241
-----Original Message-----
From: Linda Seltzer [mailto:[log in to unmask]]
Sent: 20 February 2008 19:41
To: MITCHELL R.L.C.; MITCHELL R.L.C.
Subject: RE: [SPM] effective sampling rate
Rachel,
I am not sure what you mean by effective sampling rate. The sampling
rate
is 1/TR. The stimulus presentation rate is not necessarily an integral
number of TRs (sampling periods). That is why there is upsampling.
Linda Seltzer
UC Davis
> Hello :-)
>
>
>
> Has anyone written a script or developed a tool for calculating the
> effective sampling rate given the TR and stimulus presentation rate?
>
> Easy to do by hand for whole numbers of course, but not when you're
> dealing with a couple of decimal places :-(
>
>
>
> With hopeful thanks
>
>
>
> Rachel
>
>
>
> *************************************************************
>
>
>
> Dr. Rachel L. C. Mitchell,
>
> Lecturer in Psychology, Durham University.
>
> Honorary Senior Research Fellow, Institute of Psychiatry, KCL.
>
> Correspondence Address:
>
> Dept. of Psychology,
>
> Durham University,
>
> Science Site,
>
> South Road,
>
> Durham,
>
> Co. Durham.
>
> DH1 3LE.
>
> U.K.
>
>
>
> Phone +44 (0)191 334 3272
>
> Fax +44 (0)191 334 3241
>
>
>
>
>
>
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