EEG and Optical Imaging Lab

Seizure displayed on an EEG.

Summary

Dr. Medvedev’s basic research combines a novel technology of noninvasive near-infrared spectroscopy (NIRS)-based functional imaging of the brain with a more traditional electrophysiological analysis (high density EEG, event-related potential (ERP), evoked and induced oscillations). Hemodynamic (as measured by NIRS) and neuronal (as measured by fast optical signals and EEG) responses of the brain are studied to analyze spatiotemporal organization and hemispheric lateralization of cognitive functions such as object recognition, language, memory, as well as mechanisms of neurological diseases. Combination of different technologies to analyze dynamic processes of the brain is supported by advanced methods of signal processing (Independent Component Analysis, time-frequency decomposition, Granger causality, directed coherence). These techniques provide new insights into the integrative mechanisms of cognitive functions and how those processes and mechanisms are disturbed in neurological diseases.

Research Team

Principal Investigator: Andrei Medvedev, PhD

PhD students:

  • Frank Fishburn
  • Kelly Michaelis
  • Sylvia Rusnak

Collaborators

Rhonda Friedman, PhD
Georgetown University, Department of Neurology

Scott Turner, MD, PhD
Georgetown University, Department of Neurology

Jagmeet Kanwal, PhD
Georgetown University, Department of Neurology

Gholam Motamedi, MD
Georgetown University, Department of Neurology

John VanMeter, PhD
Georgetown University, Department of Neurology

Chandan Vaidya, PhD
Georgetown University, Department of Psychology

Rachel Barr, PhD
Georgetown University, Department of Psychology

Walter Besio, PhD
University of Rhode Island, Department of Electrical, Computer and Biomedical Engineering

Amir Gandjbakhche, PhD
National Institutes of Health, National Institute of Child Health and Human Development

Kimford Meador, MD
Emory University, Department of Neurology

Contact Information

Andrei Medvedev, PhD
Associate Professor, Department of Neurology
Georgetown University, Building D, #202A
4000 Reservoir Rd, NW
Washington, DC 20057
Phone: 202-687-5126
Fax: 202-687-7906

seizure being shown using optical imaging.

Publications

  1. Besio WG, Martínez-Juárez IE, Makeyev O, Gaitanis JN, Blum AS, Fisher RS, Medvedev AV (2014) High-frequency oscillations recorded on the scalp of patients with epilepsy using tripolar concentric ring electrodes. IEEE J Translational Eng Health Med. (J-TEHM): vol. 2, 2014 (doi: 10.1109/JTEHM.2014.2332994)
  2. Fishburn FA, Norr ME, Medvedev AV, Vaidya CJ (2014) Sensitivity of fNIRS to cognitive state and load. Front Hum Neurosci 8, Article 76 (doi: 10.3389/fnhum.2014.00076)
  3. Medvedev AV (2013) Does the resting state connectivity have hemispheric asymmetry? A near-infrared spectroscopy study. NeuroImage 85(1): 400-407 (doi: 10.1016/j.neuroimage.2013.05.092)
  4. Medvedev AV (2013) Shedding near-infrared light on brain networks. J Radiol Radiat Ther 1: 1002 (editorial)
  5. Mellem MS, Friedman RB, Medvedev AV (2013) Gamma- and theta-band synchronization during semantic priming reflect local and long-range lexical-semantic networks. Brain Lang. 127(3): 440-51 (doi: 10.3389/fpsyg.2012.00097)
  6. Besio WG, Makeyev O, Medvedev A, Gale K (2013) Effects of transcranial focal electrical stimulation via tripolar concentric ring electrodes on pentylenetetrazole-induced seizures in rats. Epilepsy Res. 105: 42-51 (doi: 10.1016/j.eplepsyres.2012.12.002)
  7. Karamzadeh N, Medvedev A, Azari A, Gandjbakhche A, Najafizadeh L (2012) Capturing dynamic patterns of task-based functional connectivity with EEG. NeuroImage 66: 311–317 (doi: 10.1016/j.neuroimage.2012.10.032)
  8. Mellem MS, Bastiaansen MC, Pilgrim LK, Medvedev AV, Friedman RB (2012) Word class and context affect alpha-band oscillatory dynamics in an older population. Front Psychol 3, Article 97
  9. Medvedev AV, Murro AM, Meador KJ (2011) Abnormal interictal gamma activity may manifest a seizure generating zone in temporal lobe epilepsy. Int J Neural Syst 21: 103-114
  10. Besio W, Liu X, Wang L, Medvedev AV, Koka K (2011) Transcutaneous electrical stimulation via concentric ring electrodes reduced pentylenetetrazole-induced synchrony in beta and gamma bands in rats. Int J Neural Syst 21: 139-149
  11. Medvedev AV, Kainerstorfer JM, Borisov SV, VanMeter J (2011) Functional connectivity in the prefrontal cortex measured by near-infrared spectroscopy during ultra-rapid object recognition. J Biomed Opt 16: 016008
  12. Medvedev AV, Kainerstorfer JM, Borisov SV, Gandjbakhche AH, VanMeter J (2010) “Seeing” EEG through the skull: imaging prefrontal cortex with fast optical signal. J Biomed Opt 15: 061702
  13. Besio WG, Gale K, Medvedev AV (2010) Possible Therapeutic Effects of Transcutaneous Electrical Stimulation via Concentric Ring Electrodes, Epilepsia 51(S3): 85-87
  14. Cao H, Besio W, Jones S, Medvedev AV. (2009) Improved separability of dipole sources by tripolar versus conventional disk electrodes: a modeling study using independent component analysis. Proc IEEE Eng Med Biol Soc. 1: 4023-6
  15. Medvedev AV, Kainerstorfer J, Borisov SV, Barbour RL, VanMeter J (2008) Event-related fast optical signal in a rapid object recognition task: improving detection by the Independent Component Analysis. Brain Res 1236:145-158
  16. Medvedev AV and Kanwal JS (2007) Communication call evoked gamma-band activity in the auditory cortex of awake bats is modified by complex acoustic features. Brain Res 1188: 76-86
  17. Medvedev AV and Kanwal JS (2004) Local field potentials and spiking activity in the primary auditory cortex in response to social calls. J Neurophysiol 92: 52-65
  18. Medvedev AV (2002) Epileptiform spikes desynchronize and diminish fast (gamma) activity of the brain. An “anti-binding” mechanism? Brain Res Bull 58: 115-128
  19. Medvedev AV (2001) Temporal binding at high (gamma) frequencies in the brain: paving the way to epilepsy? Australas Phys Eng Sci Med 24: 37-48