Parametric Modulation refers to the modulation of the amplitude of a hemodynamic response based on some parameter. For example, a task might manipulate the memory load, pain intensity, or risk. One might be interested in measuring the relationship between the parameter and the hemodynamic reponse. One could imaging plotting the amplitude of the response against the parameter, then fitting a line to this scatter plot. This linear model would have two parameters: an intercept/offset and a slope. Exploring the parametric modulation is the same as asking questions about the slope (is it different than 0? more than 0? less than 0?). The following describes how this is accomplished in FSFAST.

Example: a subject is stimulated 50 times with a painful stimulus. The painfulness of the stimulus can be any of 5 different levels.

The "usual" way to analyze this would be to set up a paradigm file with 5 event types. For parametric modulation,