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The Feinstein Institute for Medical Research

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Ashesh Mehta, MD, PhD

Assistant Investigator, Susan and Leonard Feinstein Center for Neurosciences,
The Feinstein Institute for Medical research


Director, Laboratory of Multimodal Brain Mapping, North Shore-LIJ Health System

Associate Professor of Neurosurgery, Hofstra North Shore-LIJ School of Medicine

Phone: (516) 325-7061
Email: amehta@nshs.edu

Personal Statement

The clinical circumstance of invasive electrode implantation for the purposes of mapping function and pathology in patients with intractable focal epilepsy provides an unparalleled access to human brain physiology. The comprehensive epilepsy center at the North Shore LIJ Health System performs approximately 50-75 epilepsy surgery procedures annually involving implantation of electrodes for seizure monitoring and neurostimulation, extraoperative functional electrical stimulation mapping and therapeutic removal of epileptic brain tissue by surgical resection or ablation. Our lab uses this as an opportunity to study properties of brain networks, cognitive neurophysiology, validation of noninvasive neuroimaging with invasive electrophysiology and the effects of cortical stimulation on cognition and behavior. In this capacity, our lab is uniquely situated with the access to carry out research involving some of the most direct observations of in vivo human brain physiology.

One focus of the lab involves intraindividual, multimodal comparisons of networks using noninvasive intrinsic functional connectivity analysis applied to MRI and invasive electrocorticography. We have shown consistent intraindividual correspondence of network measures. Furthermore, we have developed databases of patients who have undergone invasive electrode monitoring with multiple intraindividual measures of brain connectivity including DTI, resting fMRI, electrocorticography, and cortico-cortical evoked potentials. We have also collected and archived data with regard to localization of functional areas using electrical stimulation mapping and task-related electrocorticography/fMRI as well as clinical measures including localization of the seizure onset zones, extent of resection and surgical outcome. We believe that these datasets will not only provide a more detailed understanding of brain networks, but because epilepsy is a network disease, these studies may ultimately improve epilepsy surgery outcome.

Another area of interest involves the neurophysiological basis of perception, cognition and action. With such direct access to human electrophysiology, we have studied the neurophysiological basis of a number of cognitive phenomena including language, visual object identification, attention, memory and motor planning. Furthermore, with direct cortical stimulation, we have begun to unravel how neuromodulation may be used to improve these various aspects of cognitive function.

Please click here to view the interview of Dr. Mehta on CBS news’ up to the minute on the human brain mapping project.

Research Focus

The Laboratory for Multimodal Human Brain Mapping uses multiple methods for measuring brain structure and function to advance our understanding of human brain function and the treatment of epilepsy. The methods used include magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), electrocorticography (ECoG), and direct electrical cortical stimulation. The main goals of the lab are the following:

Improving the diagnosis of epilepsy patients

Successfully treating epilepsy requires understanding what regions of the brain are responsible for seizure activity and what regions are critical to cognitive functions such as language and memory. fMRI is a promising method for doing this since it can non-invasively measure the function of the entire brain with millimeter spatial resolution. The lab is investigating the utility of fMRI for identifying regions involved in language function and for identifying networks of areas responsible for epileptic activity.

Improving our understanding of the root causes of epilepsy

As our understanding of epilepsy has grown, it has become increasingly clear that epilepsy is often caused by abnormal interactions between different parts of the brain. In other words epilepsy is often caused by a pathological network rather than a single epileptogenic area. The lab researches the use of fMRI, DTI, ECoG, and cortical stimulation for identifying these pathological networks and is attempting to uncover how their interactions produce seizures.

Furthering our understanding of the physiological basis
of these multiple measures of brain structure and function.

Different measures of human brain function have complementary strengths and weaknesses. For example, in contrast to ECoG, fMRI provides much more complete coverage of the entire brain but has much lower temporal resolution. Consequently, understanding the function of the human brain in much detail requires combining the findings from these different measures. However, doing so is complicated by the fact that the relationship between these measures is somewhat ambiguous (e.g., activity measured by ECoG might be invisible to fMRI). By obtaining these multiple measures of brain function in the same individuals, we are able to better understand how these measures relate and what inferences can be made from each measure alone.

Understanding the physiological basis of
human cognitive and sensorimotor brain function.

The neuronal basis for visual and auditory perception, language, memory, motor function and attention are studied using invasive electrodes in patients undergoing seizure monitoring for epilepsy surgery. Results from fMRI, EEG and cortical stimulation mapping are used to define areas and networks of areas involved in physiological function.

Lab Members

Zianka Fallil, MD
Assistant Professor

David M. Groppe, PhD
Institute Scientist

Pierre Mégevand, MD, PhD
Postdoctoral Fellow

Erin Yeagle
Research Assistant

Collaborators:

Rafael Malach, PhD
Charles E. Schroeder, PhD
Michael Milham, MD, PhD
Cameron Craddock, PhD
Fred Lado, MD, PhD
Elana Zion-Golumbic, PhD
Stephan Bickel, MD, PhD
Manuel Mercier, PhD
Corey J. Keller, PhD
Lucia Melloni, PhD
Ido Davidesco, PhD
Tal Golan
Meir Meshulam
Ella Podvalny

Education

University of Rochester, Rochester, NY
Degree: BS
1988
Field of Study: Biology, Neuroscience

Albert Einstein College of Medicine, Bronx, NY
Degree: MD/PhD
1999
Field of Study: Medicine/Neuroscience

Awards & Honors

1984-1988 Regents Scholarship, University of Rochester
1988 Cum Laude, University of Rochester
1991-1999 Medical Scientist Training Program, Albert Einstein College of Medicine
1993-1999 Samuel and May Rudin Scholar, Albert Einstein College of Medicine
1996 Sue Golding Award, Albert Einstein College of Medicine
2004 Distinguished Housestaff Award, New York Presbyterian Hospital
2005 Resident Award, Stereotactic Neurosurgery, University of Pittsburgh
2010 Annual Honoree, Epilepsy Foundation of Long Island

Publications
  1. Mehta AD, Labar D, Dean A, Harden C, Hosain S, Pak J, Marks D and Schwartz TH. 2005. “Frameless Stereotactic Placement of Depth Electrodes for Epilepsy.” Journal of Neurosurgery. 102:1040-1045.
  2. Suh M, Bahar S, Mehta AD and Schwartz TH. 2005. “Temporal Dependence in Uncoupling of Blood Volume and Oxygenation during Interictal Epileptiform Events in Rat Neocortex.” Journal of Neuroscience. 5:68-77.
  3. Lakatos P, Karmos G, Mehta AD, Ulbert I and Schroeder CE.  2008.  “Entrainment of Neuronal Oscillations as a Mechanism of Attentional Selection.”  Science.  320:110-113.
  4. Mehta AD and Klein G. 2010.  “Clinical utility of functional magnetic resonance imaging for brain mapping in epilepsy surgery.” Epilepsy Research. 89: 126-132.
  5. Keller CJ, Bickel S, Entz L, Ulbert I, Kelley AM, Milham M and Mehta AD. 2011. “Intrinsic Functional Architecture Predicts Electrically Evoked Responses in the Human Brain.”  Proceedings of the National Academy of Sciences (USA). 25:10308-10313.
  6. Besle J., Schevon CA, Mehta AD, Lakatos P, Goodman RR, McKhann GM, Emerson RG and Schroeder CE. 2011. “Tuning of the human neocortex to the temporal dynamics of attended events.” J Neuroscience. 31:3176-3185.
  7. Keller CJ, Bickel S, Honey CJ, Groppe DM, Entz L, Craddock RC, Lado FA, Kelly C, Milham MP and Mehta AD.  2013.  “Neurophysiological investigation of spontaneous correlated and anticorrelated fluctuations of the BOLD signal.”  J Neuroscience.  33:6333-6342.
  8. Castellanos FX, Di Martino A, Craddock RC, Mehta AD and Milham MP. 2013.  “Clinical applications of the functional connectome.”  Neuroimage. 80:527-540.
  9. Groppe DM, Bickel S, Keller CJ, Jain SK, Hwang ST, Harden C and Mehta AD.  2013.  “Dominant frequencies of resting human brain activity as measured by the electrocorticogram.”  Neuroimage.  79:223-233
  10. Zion-Golumbic EM, Ding N, Bickel S, Lakatos, P, Schevon CA, McKhann GM, Goodman RR, Emerson R, Mehta AD, Simon JZ, Poeppel D, Schroeder CE. 2013. “Mechanisms Underlying Selective Neuronal Tracking of Attended Speech at a “Cocktail Party”.” Neuron. 77: 980-991
  11. Davidesco I, Zion-Golumbic E, Bickel S, Harel M, Groppe DM, Keller CJ, Schevon CA, McKhann GM, Goodman RR, Goelman G, Schroeder CE, Mehta AD, Malach R. 2014. “Exemplar selectivity reflects perceptual similarities in human fusiform gyrus.” Cerebral Cortex. 24:1879-1893.
  12. Megevand P, Groppe DM, Goldfinger MS, Hwang ST, Kingsley PB, Davidesco I and Mehta AD. “Seeing scenes: Topographic visual hallucinations evoked by direct electrical stimulation of the parahippocampal place area.” 2014. J Neurosci. 34:5399-5405
  13. Keller CJ, Honey CJ, Entz L, Bickel S, Groppe DM, Toth E, Ulbert I, Lado FA and Mehta AD. 2014. “Cortico-cortical evoked potentials reveal projectors and integrators in human brain networks.” J Neurosci. In press.
  14. Keller CJ, Honey CJ, Megevand P, Entz L, Ulbert I and Mehta AD. 2014. “Using cortico-cortical evoked potentials to map complex networks in the human brain.” Phil Trans Royal Soc. (Lond) Ser B. In press.
  15. Entz L, Toth E, Keller CJ, Bickel S, Groppe DJ, Fabo D, Kozak LR, Eross L, Ulbert I an Mehta AD.  2014.  “Effective Connectivity of the Human Neocortex Derived from Direct Electrocortical Stimulation.”  Human Brain Mapping.  In press.

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