Evaluation of Hemodynamic Response Function in Vision and Motor Brain Regions for the Young and Elderly Adults

introduction: prior studies comparing hemodynamic response function (hrf) in the youngand elderly adults based on fmri data have reported inconsistent findings for brain vision andmotor regions in healthy aging. it is shown that the averaging method employed in all previousworks has caused this inconsistency. the averaging is so sensitive to outliers and noise. however,fmri data are obscured with a major contribution of noise particularly in the elderly case. methods: deconvolution algorithm is here proposed for hrf extraction to achieve morerobustness against noise. in spite of earlier works, proposed deconvolution algorithm yieldscompatible hrf results using either original or denoised fmri data, though a large percentageof selected active voxels change in the latter case. in the current study, event-related fmridata have been used for 18 subjects (8 young and 10 elderly adults) with a simple visual andmotor task of pressing a key with index in response to the visual presentation of the word tap.considering anatomically-defined vision and motor regions and preprocessing steps in fsl andspm, the activated voxels have been selected according to t-test for which hrf is estimatedusing deconvolution method. results: experimental results demonstrate that hrf peak amplitudes do not differ significantly(p=0.8) in the vision region for the young and the elderly. in motor region, the hrf peaksignificantly increases for the young compared to the elderly (p<0.03). repeating the procedureon the denoised fmri data using mdl algorithm, the same results have been obtained. discussion: in this study, a comparative study has been realized on the hemodynamicresponse properties associated with the young and the elderly adults on a simple visualand motor task.