Renata
Ferranti Leoni1,2, Draulio Barros de Araujo2, Afonso
Costa Silva3
1Cerebral Microcirculation Unit ,
National Institute of Neurological Diseases and Stroke - NINDS/NIH, Bethesda,
MD, United States; 2Department of Physics and Mathematics,
University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil; 3Cerebral
Microcirculation Unit, National Institute of Neurological Diseases and Stroke
- NINDS/NIH, Bethesda, MD, United States
The
presence of sustained negative fMRI response to focal brain stimulation can
be explained either by decreased local neuronal activity (neuronal surround
inhibition) or by decreased cerebrovascular reserve (vascular steal effect).
Here we measured the CBF and BOLD responses to somatosensory stimulation in
spontaneously hypertensive rats (SHR) and normotensive controls, to test the
origin of negative fMRI responses. 20/30 SHR, but only 3/25 normotensive
rats, presented robust negative CBF and BOLD responses. We conclude that the
negative fMRI responses were largely related to a vascular steal effect and
not due to neuronal surround inhibition.