||Assistant Professor - Department of Neuroscience|
Assistant Professor - Department of Neurology
Ph.D., Harvard University, 1997
M.D., Harvard Medical School, 1997
One Baylor Plaza
Baylor College of Medicine
Houston TX, 77030
Telephone: 713-798-3972 - Fax: 713-798-2334
The goals of Dr. Smirnakis’ research program are twofold: 1) to study the rules of neural plasticity and reorganization following nervous system injury in order to develop strategies that promote neural recovery, and 2) to study the rules by which visual stimuli are encoded in the firing patterns of ensembles of neurons, with a particular focus on the influence that stimulus history (adaptation) has on neural responses.
Neural computations in the primate brain involve the concerted activity of many neuronal units both within and across multiple brain areas (distributed coding). In order to understand and eventually promote neural repair, it is necessary to both appreciate the fundamental principles of neural computation at the level of the local neuronal circuits and to examine in vivo how the brain as a whole adjusts to injury in one of its parts.
Functional magnetic resonance brain imaging (fMRI) has the capability of noninvasive, global, in vivo monitoring of cortical activity throughout a network of brain areas that work synergistically. As such, fMRI can reveal a great deal about cortical organization at the systems level, particularly in the primate model employed by Dr. Smirnakis’ laboratory where it can be combined with techniques such as selective cortical lesioning, transient inactivation, cortical microstimulation, multi-unit electrophysiology and, in the future, in vivo 2-photon imaging to obtain complementary information at the cellular level. Dr. Smirnakis’ lab applies a combination of these techniques to investigate the principles of neural organization and reorganization following injury in both macaque and human visual systems.
Yuille A, Smirnakis SM, Xu L. Bayesian Self-Organization Driven by Prior Probability Distributions. Neural Computation. 1995; 7(3):580-93.
Smirnakis SM, Berry MJ, Warland DK, Bialek W, Meister M. Adaptation of retinal processing to image contrast and spatial scale. Nature. 1997; 386(6620):69-73.
Tolias AS, Moore T, Smirnakis SM, Tehovnik EJ, Siapas AG, Schiller PH. Eye movements modulate visual receptive fields of V4 neurons. Neuron. 2001; 29(3):757-67.
Tolias AS, Smirnakis SM, Augath MA, Trinath T, Logothetis NK. Motion processing in the macaque: revisited with functional magnetic resonance imaging. J Neurosci. 2001; 21(21):8594-601.
SM Smirnakis, AS Tolias, NK Logothetis. Motion Perception. In: Encyclopedia of Neuroscience 3rd edition. Eds: G Adelman and BH Smith. Elsevier, 2003.
Tolias AS, Keliris G, Smirnakis SM, Logothetis NK. Dynamic Functional Architecture of the Visual Cortex: V4 Neurons Acquire Directional Tuning after Adaptation. Nature Neuroscience. 2005; 8(5):591-3.
Ning MM, Smirnakis S, Furie K, Sheen VL. Adult acute disseminated encephalomyelitis associated with poststreptococcal infection: a case report. Journal of Clinical Neuroscience. 2005; 12(3):298-300.
Smirnakis SM, Brewer AA, Schmid MC, Tolias AS, Schüz A, Augath M, Inhoffen W, Wandell BA, Logothetis NK. Lack of long-term cortical reorganization after macaque retinal lesions. Nature. 2005; 435(7040):300-7.
Schmid MC, Oeltermann A, Juchem C, Logothetis NK, Smirnakis SM. Simultaneous EEG and fMRI in the macaque monkey at 4.7T. Magnetic Resonance Imaging, 2006; 24(4):335-42.
Smirnakis SM, Schmid MC, Weber B, Tolias AS, Augath M, Logothetis NK. Spatial specificity of BOLD versus cerebral blood volume fMRI for mapping cortical organization. Journal of Cerebral Blood Flow and Metabolism. 2007; 27(6):
Awards, Recognition, Appointments, and Honors
2006-09 Dana Neuroimaging Award (Track A), Dana Foundation
2006-09 Early Career Award, Howard Hughes Medical Institute
2002-07 K08 Fellowship (National Eye Institute), Massachusetts General Hospital and Max Planck Institute for Biological Cybernetics
2001-02 Howard Hughes Medical Institute Physician Postdoctoral Fellowship, Max Planck Institute for Biological Cybernetics
2000-01 Chief Resident in Neurology, Massachusetts General Hospital and Brigham and Women's Hospital
Current Graduate Students
Visual modulation strength in macaque primary visual cortex following homonymous retinal lesions. A rotating checkerboard stimulus was used to map cortical activity in macaque primary visual cortex following homonymous retinal lesions induced by laser photocoagulation. To quantify the strength of the visual modulation we used the measure of coherence (bottom right). Coherence is the amplitude of the BOLD signal at the visual stimulation frequency normalized by the square root of the signal power in a range of nearby frequencies (noise). Coherence levels near 1 indicate strong visually driven modulation (red), whereas coherence levels near 0.28 correspond to noise in this example. A color coded map of coherence values is overlaid on the monkey’s central primary visual cortex (right). The light green area is devoid of significant visually driven BOLD signal modulation and corresponds to deafferented V1 cortex, i.e. to the retinal lesion projection zone (LPZ). Note, in contrast, that strong visually driven modulation (red) is present in the non-deafferented V1 cortex surrounding the LPZ (left upper panel). The left bottom panel plots the normalized modulation strength of multi-unit activity as a function of distance from the LPZ border (blue curve). This was obtained using a linear 16-electrode array placed across the LPZ border (blue line). The normalized value of the BOLD signal coherence (red) is plotted for comparison. Note the close correspondence of these curves confirming that BOLD coherence closely reflects multi-unit activity in this paradigm. The extent of cortical reorganization can be measured by monitoring how the strength and the spatial topography of the BOLD and the electrophysiology signals change as a function of time (or as a function of rehabilitative-training) near the border of the LPZ. IOS: inferior occipital sulcus. LPZ: lesion projection zone. Adapted from Smirnakis et al., Nature 435:300-7, 2005.