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help > gPPI with parametric modulator entered as user-specific regressor
Jun 7, 2018 02:06 PM | yogr - The University of Tokyo
gPPI with parametric modulator entered as user-specific regressor
Dear experts,
We have a trouble with applying gPPI to a model with multiple parametric modulators, which were entered to SPM as user-specific regressors (not to "parametric modulations").
As Mumford et al. (2015) points out, the SPM results change depending upon the order in which the parametric modulators are specified in the model.
http://journals.plos.org/plosone/article...
To avoid this problem, we manually created parametric modulators and specified in the model as user-specific regressors (i.e. not as "fmri_spec.sess.cond(i).pmod(n)", but as "fmri_spec.sess.regress(n)"). The methods appear below.
https://canlabweb.colorado.edu/wiki/doku...
Then the issue of the order has been solved, but gPPI does not work.
We specified PMs as below (1)-(3), but neither of them ran successfully. Although Contrasts(1) is successfully built but Contrast(2) is not, and we get an error message, "Warning: Missing conditions!!! Invalid Contrast".
(1)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail={'PM1'};
(2)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail.L={'PM1'};
(3)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail.L={'PM1'};
P.Contrasts(2).Contrail.R={'none'};
Some experts recommend us to switch orth option from 1 to 0 and use SPM parametric modulation, but it seems to weaken the effect of condition.
Is there any solution?
Thank you very much in advance,
Yukiko
We have a trouble with applying gPPI to a model with multiple parametric modulators, which were entered to SPM as user-specific regressors (not to "parametric modulations").
As Mumford et al. (2015) points out, the SPM results change depending upon the order in which the parametric modulators are specified in the model.
http://journals.plos.org/plosone/article...
To avoid this problem, we manually created parametric modulators and specified in the model as user-specific regressors (i.e. not as "fmri_spec.sess.cond(i).pmod(n)", but as "fmri_spec.sess.regress(n)"). The methods appear below.
https://canlabweb.colorado.edu/wiki/doku...
Then the issue of the order has been solved, but gPPI does not work.
We specified PMs as below (1)-(3), but neither of them ran successfully. Although Contrasts(1) is successfully built but Contrast(2) is not, and we get an error message, "Warning: Missing conditions!!! Invalid Contrast".
(1)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail={'PM1'};
(2)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail.L={'PM1'};
(3)
P.Contrasts(1).left={'Cond1'};
P.Contrasts(1).right={'none'};
...
P.Contrasts(2).left={'Cond1'};
P.Contrasts(2).right={'none'};
P.Contrasts(2).Contrail.L={'PM1'};
P.Contrasts(2).Contrail.R={'none'};
Some experts recommend us to switch orth option from 1 to 0 and use SPM parametric modulation, but it seems to weaken the effect of condition.
Is there any solution?
Thank you very much in advance,
Yukiko
Threaded View
Title | Author | Date |
---|---|---|
yogr | Jun 7, 2018 | |
Donald McLaren | Jun 7, 2018 | |
yogr | Jun 7, 2018 | |
Donald McLaren | Jun 7, 2018 | |
yogr | Jun 7, 2018 | |
Donald McLaren | Jun 7, 2018 | |
yogr | Jun 8, 2018 | |
Donald McLaren | Jun 8, 2018 | |