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. Author manuscript; available in PMC: 2017 Feb 15.
Published in final edited form as: Neuroimage. 2015 Dec 5;127:23–33. doi: 10.1016/j.neuroimage.2015.11.066

Figure 3.

Figure 3

Predicted effects of the hemodynamic response function on fMRI orientation signals. A) Hypothetical tuning curve that resembles a radial-bias like signal. B) The result of convolving the tuning curve in (A) with a hemodynamic response function (dashed curves), in which the oriented grating rotates through time over a 24 second period as in Freeman et al. and our Experiments 1 and 2. C) The result of convolving the hypothetical curve in (A) with the same HRF, but with a slower rotation period of 72 seconds. D) A hypothetical tuning curve that has a more complex signal, such as might reflect uneven sampling from the cortical columnar structure. E) In the 24-second design, convolution with the HRF filters out the complex aspects of the signal. F) Slowing the rotation period to 72 seconds greatly mitigates the filtering effect.