This study further investigates the influence of temporarily disrupting the blood-brain barrier (BBB) on the level of manganese used in AIM fMRI other than the recognized function of allowing that substance to enter into the activated brain regions more effectively during the BBB opening. We injected manganese into Wistar rats through ICA following the disruption of BBB with mannitol in a functional MRI test of the visual cortex. Through comparing MRI signal intensity and manganese contents in the visual cortex of rats received visual stimuli of unequal degree after the restoration of BBB, we found that the signal in the visual cortex could be further enhanced on T1WI given visual stimulation after the restoration of BBB. Temporary BBB disruption has an additional advantage in allowing Mn(2+) to enter the CSF or brain for later transference to the activated brain area. So the dosage of manganese in AIM fMRI could be minimized by extending the stimulus.