Dear Rachel and Matt,
I am also facing a similar problem, as I have tried to model time-locked
events occurring within auditorily presented sentences (of more or less
constant duration) in an event-related design with continuous fMRI sampling.
Up to now, I have tried modelling the appearance of the verb with an informed
set of hemodynamic basis functions (hrf + 2 derivatives) with very little
success.
I was now considering to use a FIR basis set time-locked to the beginning of
each sentence, in order to try to capture responses associated to the
processing of the entire sentence and/or to early or late sentence
components.
Does anybody have an idea of whether a FIR model would be appropriate for such
a purpose? Would a Fourier basis set be better/worse?
Thank you!
Marco
On Wednesday 10 May 2006 15:01, Matt Davis wrote:
> Dear Rachel,
>
> There are a few studies in which my colleagues and I have treated
> sentences as single, discrete events and analysed fMRI responses to
> sentence-level manipulations (e.g. ambiguity, acoustic distortion) in
> an event-related fashion. So far, these have all been sparse-imaging
> studies, in which a single scan measures the neural response to each
> sentence. In some respects this obliges us to use a single sentence =
> single event, analysis procedure.
>
> With the range of sentence durations that you are using in your
> study, however, it is perhaps possible that this procedure might be
> less successful. There will likely be significant differences in
> activation caused by duration differences (which you should probably
> match across your sentence conditions). You might also wish to use
> sentence duration as a parametric modulator in your analysis. It
> could also prove to be difficult to know whether the critical neural
> response to your stimulus is time-locked to the beginning, middle or
> end of your sentences. These assumptions can be critical in designing
> a sparse imaging study, or in analysing continuous imaging data.
>
> hope this is helpful,
>
> matt
>
> At 12:28 10/05/2006, you wrote:
> >Hello everybody.
> >
> >Just a simple question.
> >I wondered what people's views were on using auditory sentences in
> >event-related designs, or presenting sentences in a block, and then
> > picking out certain classes of stimuli or certain kinds of responses, to
> > analyse in an ER manner?
> >Can sentences really be thought of as an event?
> >I'm not sure, and have read arguments in the literature saying yes and no.
> >For reference, the sentences range in length from 0.981s to 5.006s, but
> > the mean length is 1.96s.
> >
> >With very best wishes
> >rachel
> >
> >--------------------------------------------------------
> >Dr Rachel L. C. Mitchell.
> >Lecturer in Cognitive Psychology, University of Reading.
> >Honorary Research Fellow, Institute of Psychiatry.
> >Research Psychologist, Berkshire Healthcare NHS Trust.
> >
> >Correspondence Address:
> >School of Psychology and Clinical Language Sciences,
> >Whiteknights Road
> >University of Reading
> >Reading
> >Berkshire
> >RG6 6AL
> >
> >Tel: +44 (0)118 378 8523
> >Direct Dial: +44 (0)118 378 7530
> >Fax: +44 (0)118 378 6715
> >-----------------------------------------------------------------------
>
> ****************************************************
> Dr Matt Davis
> MRC Cognition and Brain Sciences Unit
> 15 Chaucer Road, Cambridge, CB2 2EF
>
> email: [log in to unmask]
> tel: 01223 273 637 (direct line)
> tel: 01223 355 294 (reception)
> fax: 01223 359 062
>
> ****************************************************
--
Marco Tettamanti, Ph.D.
San Raffaele Scientific Institute
Department of Neuroscience
c/o L.I.T.A. - room 25/5
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