Afonso C. Silva, Ph.D.
Cerebral Microcirculation Unit
Building 10, Room B1D106
10 Center Drive
Bethesda, MD 20892-1065
Unlike any other organ of the body, the brain is critically dependent on a continuous blood supply. Due to its high energy demands, the brain operates under a tight coupling of neuronal electrical activity to the hemodynamic regulation of energy supply and waste removal. The 'neurovascular coupling' entails a complex, highly redundant array of signaling mechanisms aimed at maintaining homeostasis of the brain parenchyma by regulating CBF on a precise spatial and temporal domain. There is increased evidence that such mechanisms result from an integrated action of neurons, glia and blood vessels, which form a 'neurovascular unit' acting at the cellular level to regulate local CBF. Disruption of these mechanisms causes brain dysfunction and disease. Our laboratory is interested in understanding the mechanisms of CBF regulation during normal and pathological brain states. The fundamental questions related to cerebral blood flow regulation are: 1. What is the smallest vascular unit that adapts independently to brain activity? 2. How is this elemental vascular unit related to the cortical architecture? 3. What are the major signaling pathways, and the key molecules, that translate a change in brain activity into a vascular response? To address the above questions, we are working on well-defined rodent and non-human primate models of localized functional brain activation, using modern neuroimaging techniques (fMRI or optical microscopy), in combination with electrophysiology recordings of cortical activity. The cerebrovascular coupling will be tested under the presence of agonists and antagonists of several different known mediators or modulators of CBF. Complimentary information on the cerebrovascular coupling will be studied under pathophysiological brain conditions, such as the ones obtained using experimental animal models of brain stroke. More detailed information about our research can be found in our laboratory's webpage: Cerebral Microcirculation Unit
Dr. Silva received his Bachelor's Degree in Electrical Engineering from Universidade Federal de Pernambuco in Recife, Brazil, and his Ph.D. in Bioengineering from Carnegie Mellon University, where he worked on non-invasive MRI measurements of cerebral blood flow using the arterial spin labeling technique. He then went on to do post-doctoral training in the Center for Magnetic Resonance Research at the University of Minnesota, where he studied the temporal and spatial characteristics of functional brain hemodynamics under the supervision of Prof. Seong-Gi Kim. Dr. Silva joined NINDS as a Staff Scientist in 1999, and became an investigator in 2004. His laboratory combines modern neuroimaging techniques (functional MRI, and optical imaging) with electrophysiological recordings aimed at understanding the mechanisms of regulation of cerebral blood flow during normal and stimulation-induced brain activity.
Bock NA, Kocharyan A, Silva AC. Manganese-enhanced MRI visualizes V1 in the non-human primate visual cortex. NMR Biomed. 2009;22(7):730-6.
Hirano Y, Stefanovic B, Silva AC. Spatiotemporal evolution of the functional magnetic resonance imaging response to ultrashort stimuli. J Neurosci. 2011;31(4):1440-7.
Liu JV, Hirano Y, Nascimento GC, Stefanovic B, Leopold DA, Silva AC. fMRI in the awake marmoset: somatosensory-evoked responses, functional connectivity, and comparison with propofol anesthesia. Neuroimage. 2013;78:186-95.
Hung CC, Yen CC, Ciuchta JL, Papoti D, Bock NA, Leopold DA, Silva AC. Functional MRI of visual responses in the awake, behaving marmoset. Neuroimage. 2015;120:1-11.
Hung CC, Yen CC, Ciuchta JL, Papoti D, Bock NA, Leopold DA, Silva AC. Functional mapping of face-selective regions in the extrastriate visual cortex of the marmoset. J Neurosci. 2015;35(3):1160-72.
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This page was last updated on August 24th, 2011