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. Author manuscript; available in PMC: 2018 Oct 17.
Published in final edited form as: J Pain. 2018 Mar 30;19(9):961.e1–961.e21. doi: 10.1016/j.jpain.2018.03.011

Figure 2.

Figure 2.

Stimulus convolution. Here, a hypothetical pattern of stimuli is convolved with the HRF. In the upper panel, an eventrelated design is convolved to a double-gamma function to model the HRF. In the lower panel, the convolution of a block design study is shown. A prolonged stimulus would, in theory, elicit repeated HRFs. These are summated to produce a regressor to produce an idealized model of brain activity correlated to the stimulus. Note that the peak of the HRF is delayed with respect to the onset of the stimulus, and the offshoot is delayed with respect to the offset of the stimulus.