Dear Justine,
I had a chat with my colleagues about your query. The balloon model is based on physiological research across species and there shouldn't be anything majorly different in monkeys. If you use DCM as it is, you'll get haemodynamic parameter estimates in DCM.Ep.transit, DCM.Ep.decay and DCM.Ep.epsilon. You can then use these as priors for your future studies - let me know if you need help doing this.
Regarding contrast agents, I have no experience in this area, but I have forwarded your email to a colleague who might.
Best,
Peter
-----Original Message-----
From: Justine Clery [mailto:[log in to unmask]]
Sent: 16 April 2015 16:20
To: Zeidman, Peter; [log in to unmask]
Subject: Re: [SPM] DCM : parameters for monkey
Dear Peter,
Thank you for your answer. From the files you directed me to, the balloon model does make additional assumptions/ a priori in addition to the default HRF defined in spm. So my next question is would any of these a priori be specific to 1) human physiology ? and 2) to using BOLD vs. a contrast agent heamodynamic response ?
If you could indeed direct me to any relevent person, that would be extremely helpful !
Justine
Le 16/04/2015 12:29, Zeidman, Peter a écrit :
> Dear Justine,
> DCM uses a different haemodynamic model than the canonical model in spm_hrf. It based on the balloon model and has parameters which are separately estimated in each region to improve model fit. See spm_fx_fmri and spm_gx_fmri.m for more details. If you'd like any more details, feel free to get in touch with me and I'll pass your query on to the relevant people.
>
> Best,
> Peter
>
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
> On Behalf Of Justine Cléry
> Sent: 15 April 2015 13:16
> To: [log in to unmask]
> Subject: [SPM] DCM : parameters for monkey
>
> Hi everyone,
>
> I want to do a DCM analysis on monkey fMRI data to analyse effective connectivity.
> The human HRF saved by default in spm8 (file "spm_hrf.m") has been replaced by a monkey HFR (that in particular takes into account the fact that we do not measure BOLD by use a contrast agent to enhance SNR). This new HRF has been renamed as the default, so all is transparent to spm8.
> My question is the following: does the DCM procedure make any assumption on the human based HRF, that I should be aware of, or does it only use the parameters defined in the spm_hfr.m file ?
>
> Anybody already tried DCM on monkey fMRI data?
>
> Thank you!
>
> Justine.and
--
Justine Cléry,
PhD Student
Équipe "Bases neurales de la cognition spatiale et de l'action"
Centre de Neuroscience Cognitive (UMR 5229)
67 boulevard Pinel
69675 BRON cedex.
Tel : 33 (0)4 37 91 12 42.
|