> Dear SPMers,
>
> I am new at doing efMRI. I am doing an efMRI study using synthetic speech
> syllables as auditory stimuli. The phonetic cues are sufficiently subtle
> that I need to interleave the stimuli and image acquisition. I should
> mention that the subjects are aphasic patients with speech perception
> problems so we don't want acoustic masking by the scanner noise. There
> are two kinds of stimuli along with silent trials. So 3 stimulus
> conditions randomly but deterministically presented including: 1) paired
> syllables, 2) paired notes, 3) silence. Stimuli last two seconds for the
> pair. Stimuli are triggered by the scanner. I ran a subject using this
> setup:
>
> 2 seconds to acquire 27 slices
> 2 second of "gap" or delay (to separate the HRFs of the epi and stimulus)
> 2 seconds of stimulus
> 2 seconds of gap (so as to catch the peak of the HRF to the stimulus)
>
> Task is to decide same or different and press corresponding keypress.
> Accuracy to be used as a factor for the syllables.
>
> Questions are:
>
> 1. Is this is the optimal (most efficient) design given the
> interleaving constraint? My concern is that I am not doing a good job of
> sampling the HRF with a single phase. This may not be important, however.
> I'm also concerned that it's not efficient, given that we are sampling at
> only 1/8 Hz. The quickest we could sample would be 1/4 Hz with our
> constraint of interleaving stimulus and imaging.
>
> 2. How best to statistically analyze the data. The goal is to identify
> regions which not only activate for for the syllables than the notes but
> to look at correct and error trials to find the region which is associated
> with correct performance. If I am sparsely imaging the HRF but am doing
> so at the peak does this mean a t-test is as good as anything? I don't
> know what the F-test is in the context of the efMRI analysis. Is it just
> looking at differences in variance or is it a converted wilkes-lambda or
> some such regression analysis?
>
> 3. Is it true that for efMRI the soa files are expressed as V/TR + 1
> because it expects t=0 to be (V/TR) to be =1?
>
> Appreciate any help!
>
> Randy Benson
>
>
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