The general theme of our research is to study the dynamics of neural activity within and between functional brain networks by simultaneous electrophysiological recordings across the human brain. We use electrical stimulation to probe causality and fMRI to define distinct functional networks of the brain.
INTRACRANIAL ELECTROPHYSIOLOGY OF THE HUMAN DEFAULT MODE NETWORK
Since studies of the default mode network, almost entirely, rely on functional imaging methods, our recent work has tried to fill the gap of knowledge about the fast temporal dynamics of activity within this network by direct recording from the population of neurons in the main main hubs of this network, e.g., posteromedial cortex (PMC), angular gyrus (AG), medial prefrontal cortex (mPFC) and medial temporal lobe (MTL). Our intracranial work in the default mode network is rooted in the PI's earlier anatomical tracing studies of the PMC in the macaque brain that provided a comprehensive map of anatomical circuitry connecting the PMC with the rest of the brain including the regions of the brain that we currently record from.
Dastjerdi M., et al (2011): Differential electrophysiological response during rest, self-referential and non-self-referential tasks in human posteromedial cortex. PNAS 108(7): 3023-3028
Foster B.L., et al (2012): Neural populations in human posteromedial cortex display opposing responses during memory and numerical processing. PNAS 109(38): 15514-15519.
Foster B.L., and Parvizi J. Resting oscillations and cross-frequency coupling in the human posteromedial cortex. Neuroimage. 2012 Mar;60(1):384-91.
Foster B.L., et al (2013) Human Retrosplenial Cortex Displays Transient Theta Phase Locking with Medial Temporal Cortex Prior to Activation during Autobiographical Memory Retrieval. Journal of Neuroscience 33:10439-10446.
Foster B.L., et al (2015). Intrinsic and Task-Dependent Coupling of Neuronal Population Activity in Human Parietal Cortex. Neuron 86(2): 578-590.
INTRACRANIAL ELECTROPHYSIOLOGY OF THE MATH NETWORK IN THE HUMAN BRAIN
With our intracranial EEG recordings in the default mode network, we have consistently seen a significant deactivation of neuronal populations in this network when subjects are engaged in solving mathematical equations. By contrast, a new set of regions (e.g., intraparietal sulcus region, IPS) have a strong activation during numerical cognition tasks.
One of the current projects in the lab is to explore the dynamics of neuronal population activity in the human brain during experimental and real-life numerical cognition tasks and understand the antagonistic relationship between the default mode network and the regions involved in mathematical reasoning.
One of the main contributions of our lab was the discovery of a cortical area (the Visual Numeral Area) within the ventral temporal cortex that responds selectively to numerals. We are now probing the dynamics of activity between this region and the IPS when human subjects are engaged in numerical tasks.
Shum J., Hermes D., Foster B.L., Dastjerdi M., Rangarajan V., Winawer J., Miller K.J., Parvizi J.(2013) A human brain area for visual numerals. Journal of Neuroscience 33:6709-6715.
Dastjerdi M., Ozker M., Foster B.L., Rangarajan V., Parvizi J (2013): Numerical Processing in the Human Parietal Cortex During Experimental and Natural Conditions. Nature Communications 4:2528 doi:10.1038/ncomms3528
ELECTRICAL BRAIN STIMULATION
Direct electrical stimulation of the cerebral cortex provides unique insight about the causal importance of a given cortical site and its anatomical network in a specific set of functions. In a series of experiments, we have probed the causal importance of the brain areas involved in face recognition. We have also probed the subjective correlates of electrical stimulation in the anterior cingulate region of the salience network.
Selimbeyoglu A., and Parvizi, J. (2010): Electrical Stimulation of the Human Brain: Perceptual and Behavioral Phenomena Reported in the Old and New Literature. Frontiers in Human Neuroscience 4(191) doi: 10.3389/fnhum.2010.00046
Rauschecker A., Dastjerdi M., Selimbeyoglu A., Witthoft N., Weiner, K.S., Chen, J, Parvizi, J. (2011): Illusion of Visual Motion Elicited by Electrical Stimulation of Human Area MT+. PLoS ONE (6 (7): e21798. doi:10.1371/journal.pone.0021798
Parvizi J., Jacques C., Foster BL., Withoft N., Rangarajan V., Weiner KS., Grill-Spector K (2012) Electrical stimulation of human fusiform face-selective regions distorts face perception. Journal of Neuroscience 32:14915-14920.
Parvizi J., Rangarajan V., Shirer W., Desai N., and Greicius M. (2013): The will to persevere induced by electrical stimulation of the human cingulate gyrus. Neuron 80(6): 1359-1367.
Rangarajan V., Hermes D., Foster BL., Weiner KS., Jacques C., Grill-Spector K., Parvizi J. (2014): Electrical stimulation of the left and right human fusiform gyrus causes different effects in conscious face perception. Journal of Neuroscience. 34(38):12828-36
Rangarajan V, Hermes D, Foster BL, Weiner KS, Jacques C, Grill-Spector K, Parvizi J. (2014): Electrical stimulation of the left and right human fusiform gyrus causes different effects in conscious face perception. J Neurosci 34(38):12828-36. doi: 10.1523/JNEUROSCI.0527-14.2014
Rangarajan V, Parvizi (2015): Functional asymmetry between the left and right Human fusiform gyrus explored through electrical brain stimulation. J.Neuropsychologia. NSYD1500237. doi: 10.1016/j.neuropsychologia.2015.08.003. [Epub ahead of print]
Given the PI’s training in clinical neurology and functional neuroanatomy, our lab has been involved in studies that aim to understand the functional anatomical correlates of clinical phenotypes that are seen in patients with various neurobehavioral problems.
Parvizi, J., Van Hoesen, G.W., and Damasio, A.R. (2000): Selective pathological changes in the periaqueductal gray in Alzheimer’s disease. Annals of Neurology, 48(3): 334-353.
Parvizi, J., Van Hoesen, G.W., and Damasio, A.R. (2001): The selective vulnerability of the brainstem nuclei to Alzheimer’s disease. Annals of Neurology, 49(1): 53-66.
Parvizi J., Anderson SW., Martin CO., Damasio H., Damasio AR. Pathological laughter and crying: a link to the cerebellum. Brain. 2001 Sep;124(Pt 9):1708-19.
Parvizi J., Damasio AR. Neuroanatomical correlates of brainstem coma. Brain. 2003 Jul;126(Pt 7):1524-36.
Parvizi J., Le S., Foster B.L., Bourgeois B., Riviello JJ., Prenger E., Saper C., Kerrigan JF. Gelastic epilepsy and hypothalamic hamartomas: neuroanatomical analysis of brain lesions in 100 patients. Brain. 2011 Oct;134(Pt 10):2960-8.