The Influence of Neuropathology on the fMRI Signal: A Measurement of Brain or Vein?

Abstract

There is a rapidly growing literature using fMRI technology to investigate the various forms of behavioral impairment associated with brain injury and disease. Given this, surprisingly little work has been conducted to examine the influence of neuropathophysiological processes on the fMRI signal. This paper reviews the literature examining baseline alteration in cerebrovascular parameters associated with normal aging, brain injury, and brain disease. In addition, findings from three cases of individuals with severe brain trauma will be presented to show the influence of brain trauma on baseline cerebrovascular parameters measured by fMRI. The methods used here can be implemented by other investigators to accurately isolate specific hemodynamic changes that can influence the BOLD fMRI signal.

Keywords:

• Blood flow
• CBF
• fMRI
• Functional imaging
• Lesions
• TBI

ACKNOWLEDGMENTS

This research was supported in part by NIH grant HD07522, NIDRR grant H133P970011, and a grant from the Henry H. Kessler Foundation and the Hyde & Watson Foundation, West Orange, Jersey.

Notes

The unit of measurement for t₀ is seconds, CBF is ml/sec, and OEF is percent change from baseline. Note the relatively small within-subject differences in t₀, CBF, and OEF in these healthy adults compared to the two TBI cases shown in Figure 2.