I used an event-related design with three classes of acoustic stimuli which
subjects had to identify. There were 24 stimuli of each class, summing up to 72
events (plus 24 null events). Now I would like to classify stimuli according to
correct responses. Number of detected stimuli varies for the most difficult
class of stimuli between 4 and 15 (of 24). For the other two classes, the range
is between some 15 and 24 stimuli that were correctly identified. I am
interested in differential reactions between stimulus classes. My hypothesis
regarding that kind of analysis (as opposed to analysing all events) is
basically that analysing only correct responses will reduce noise and therefore
render the results much clearer.
Dominik
Zitat von Douglas Burman <[log in to unmask]>:
> Dominik,
>
> I don't have any specific advice or suggestions, but I would think that the
> appropriate analysis would depend on the minimum number of stimuli per
> class, the nature of your stimuli, and what your hypothesis is. For
> example, are you expecting differential responses to different stimuli, a
> response to some but not all stimuli, or a correlation with behavioral
> responses to one or more class of stimulus? It's hard to give suggestions
> without knowing more details about the experiment and what you are trying
> to show.
>
> Doug
>
> At 04:40 PM 11/16/2006 +0100, Dominik R. Bach wrote:
> >Hi all
> >
> >I want to analyse my fMRI data according to behavioural measures, i.e.
> >stimuli are to be classified by the subject's response. This leads to an
> >extremely unbalanced design, where the number of stimuli per class differs
> >between subjects by a factor of up to 3.
> >
> >How does this affect two-level-analysis? I read that in this case it would
> >be more appropriate to use a maximum-likelihood-approach in a one-level
> >analysis for all subjects. Is this possible within SPM?
> >
> >Thanks
> >Dominik
>
> Dept. of Communication Sciences & Disorders
> Northwestern University
> 2240 Campus Drive
> Frances Searle Building, Room 2-356
> Evanston, IL 60208
> phone 847-467-1549
> fax 847-491-4975
> email: [log in to unmask]
>
>
--
========================================
Dominik Bach, MD, MSc
Department of Psychiatric Neurophysiology
University of Berne, Switzerland
[log in to unmask]
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