Increased BOLD activation with high degree spherical harmonic shimming at 7T

B₀ shimming is important for gradient echo functional MRI where T₂^* signal loss and precession occur from both physiological and non-physiological susceptibility effects. We used the high degree shim insert (3^rd, 4^th and two 5^th degree shims) to assess its effect for 2mm isotropic whole brain GE-EPI BOLD (breath-hold induced) signal at 7T. Comparing 1^st-2^nd with high degree shimming, the Δ|B₀| changes are spatially varying. For activation, the largest regions of increase are in the inferior frontal region; the largest regions of decrease are in the middle temporal lobe. Overall, there is a 4.3% increase in total activated pixels.