.txt format

contrast definitions file

A first-level contrast definition file (contrast_*.txt) lists one or multiple contrast definitions.

Each line defines a separate contrast as a linear combination of effects estimated during the model estimation stage. Each contrast is defined using the format:

contrastname effectname1 effectweight1 effectname2 effectweight2 ...

and field names cannot contain spaces (as all fields are separated simply by one or more whitespaces). For example, the following line defines a new "S-N" contrast as a linear combination of the task effects "S" and "N":

S-N S 1 N -1


Valid task effects may be:

1) simple task effects

names matching those defined in the #names field of the .para files associated with this experimental design

2) temporal modulation effects (for temporal modulation analyses)

names matching the format [taskname]xtime, where [taskname] is a valid task effect name (as specified in (1) above)

3) modulatory interaction effects (for parametric modulations which do model condition-by-covariate interactions)

names matching the format [taskname]x[covariatename], where [taskname] is a valid task effect name (as specified in (1) above) and [covariatename] is a parametric covariate name (matching those defined in #pmod_names field of this experimental design .para files)

4) main covariate effects (for parametric modulations which do not model condition-by-covariate interactions)

names matching the format [covariatename], where [covariatename] is a parametric covariate name (in #pmod_names field of this experimental design .para files)

5) individual-event effects (for non-parametric modulations)

names matching the format [taskname]_EVENT## where [taskname] is a valid task effect name (as specified in (1) above) and ## is the event number (starting in 1 within each run/session)

example contrast definition file

contrasts_tasksAB.txt

Speech-Baseline Speech 1

NonSpeech-Baseline NonSpeech 1

Speech-NonSpeech Speech NonSpeech 1 -1

NonSpeech-Speech Speech NonSpeech -1 1

AverageTasks Speech NonSpeech 0.5 0.5