Lino Becerra1,2, Gary Brenner2,3, James Bishop1, Pei-Ching Chang1, Hae-Sook Shin3, Aimei Yang4, Michael Baratta4, Patrick Monahan4, Edward Boyden4,5, David Borsook1,2
1A. Martinos Center, Massachusetts General Hospital, Boston, MA, USA; 2Harvard Medical School, Boston, MA, USA; 3Anesthesiology & Critical Care, Massachusetts General Hospital, Boston, MA, USA; 4Media Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA; 5Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
In fMRI studies, positive activation is associated with increased neuronal firing. Negative (deactivation) fMRI BOLD signals have been indirectly associated with inhibition. Using opto-genetic techniques neurons in rat cingulate and somatosensory cortices were trasfected to be photosensitive. Specifically, cingulate neurons were inhibited upon optical stimulation while somatosensory neurons were excited when illuminated. Positive BOLD signal changes were observed in somatosensory cortex while negative ones were observed in cingulate cortex upon illumination. Furthermore, inhibition of cingulate resulted in fMRI activation of other structures. This work confirms that neuronal excitation results in positive BOLD signals and neuronal inhibition produces negative BOLD signals.