Figure 1 – Simulations show that the temporal properties of the hemodynamic response function affect the frequency spectrum of the BOLD signal.

A) We generated a simulated BOLD response to determine the response amplitude of each HRF to each neural frequency. By convolving a given HRF with an oscillating stimulus, and sweeping across a range of frequencies, we generated a frequency spectrum of the simulated BOLD responses. This simulation was repeated using HRFs with varying temporal properties, to compare the frequency spectrum of simulated BOLD responses with faster or slower hemodynamic responses. B) We generated a range of HRFs with physiologically plausible timings and amplitudes (11). C) We found that temporal properties of the HRF had noticeable effects on the simulated spectra, particularly under 0.2 Hz.