Single-word auditory stimulation and regional cerebral blood flow as studied by SPECT

Single photon emission computed tomography (SPECT) examined changes in regional cerebral blood flow (rCBF) induced by passive auditory single-word stimulation. A split-dose SPECT technique was used between resting and activated states, in which a smaller amount of ligand (99m technetium hexamethyl propyleneamine oxide, HMPAO) was given with the first scan, accompanied by a prolonged scan time. A larger amount of ligand was given with the second scan, accompanied by a shorter scan time. This split-dose SPECT technique has met with previous success for other activation tasks. The brain regions of interest (ROIs) in this study were selected from ROIs previously found to be activated by passive auditory single-word stimulation and not by non-word stimuli in positron emission tomography (PET) rCBF studies. This study thus tested the sensitivity of SPECT with HMPAO to detect brain activation with a stimulus previously demonstrated to elicit changes in rCBF with PET. However, no significant difference was detected between resting and activated states in this study. Thus, SPECT was not as sensitive as PET in this activation task. Since SPECT is a less costly and more widely available modality to study brain activation than PET, it is important to delineate its potential capacities to maximize the efficiency of future research in this field.