Stroke in the cerebral cortex is a major source of disability and a common cause of epilepsy in the elderly and in children. Neural plasticity after stroke that tends to compensate lost functions involves reorganization of the surviving neural circuits. However, some aspects of the reorganization might be maladaptive and lead to epileptogenesis over time. Thalamocortical circuits mediate neural network oscillations associated with epilepsy. While there is a large body of evidence supporting thalamic involvement in the generalized idiopathic epilepsies, very little is known about the role of thalamus in post-injury epileptogenesis. Cortical infarcts lead to retrograde cell death of a subset of excitatory ?but not inhibitory ?thalamic cells. My preliminary data indicate that after several weeks following focal cortical infarcts, isolated thalamic slices (that do not contain the cortex) spontaneously generate epileptiform network oscillations. This is paralleled by increases in intra-thalamic excitatory connectivity and decreases in intra-thalamic inhibition. Surprisingly, despite a major loss of excitatory afferents from the cortex, synaptic excitation is enhanced in thalamocortical cells located in the gliotic area functionally related to the region of focal cortical stroke. Altogether, these results suggest that cortical infarcts lead to robust circuit rewiring within the thalamus. Some aspects of this reorganization could support functional recovery. For example, reduced inhibition of relay nuclei could increase the output of TC cells and enhance thalamocortical excitation, which may facilitate recovery of thalamic and cortical sensory circuits. However, the presence of epileptiform network oscillations in the injured thalamus suggests that some aspects of the thalamic reorganization could be maladaptive, participating in injury-induced epilepsy. The two main goals of this research proposal are as follows: (1) To determine the mechanisms underlying the aberrant network excitability and synaptic excitation in the thalamus;(2) To determine whether this enhanced activity in the injured thalamus might amplify corticothalamic network excitability and contribute to epileptogenesis. These questions are crucial to our understanding of the mechanisms of post-stroke thalamocortical reorganization leading to epilepsy. I have designed several experiments to answer these goals. Several of them rely on techniques ?optrodes using optogenetic approaches in vivo , glutamate imaging, laser photostimulation/ glutamate uncaging, EEG recordings in freely moving animals ?that I will learn from my mentor and consultants who have agreed to train me during the mentored phase of the proposal. My long- term goal is to continue studying the mechanisms generating abnormal neural network oscillations associated with neurological disorders such as epilepsy or Parkinson's disease in an independent academic setting.

Public Health Relevance

Stroke in the cerebral cortex is a major source of disability and a common cause of epilepsy. Recovery of function after stroke involves not only surviving neural circuits but also the establishment of new neural circuits. This proposal aims to understand how neural circuits reorganize after stroke and what aspects of this reorganization can lead to epilepsy. This may lead into new insights on therapeutic approaches that promote functional recovery while limiting its health-impairing outcomes and preventing epilepsy.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Transition Award (R00)
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No Study Section (in-house review) (NSS)
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Whittemore, Vicky R
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J. David Gladstone Institutes
San Francisco
United States
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Sorokin, Jordan M; Davidson, Thomas J; Frechette, Eric et al. (2017) Bidirectional Control of Generalized Epilepsy Networks via Rapid Real-Time Switching of Firing Mode. Neuron 93:194-210
Clemente-Perez, Alexandra; Makinson, Stefanie Ritter; Higashikubo, Bryan et al. (2017) Distinct Thalamic Reticular Cell Types Differentially Modulate Normal and Pathological Cortical Rhythms. Cell Rep 19:2130-2142
Hiu, Takeshi; Farzampour, Zoya; Paz, Jeanne T et al. (2016) Enhanced phasic GABA inhibition during the repair phase of stroke: a novel therapeutic target. Brain 139:468-80
Sorokin, Jordan M; Paz, Jeanne T; Huguenard, John R (2016) Absence seizure susceptibility correlates with pre-ictal ? oscillations. J Physiol Paris 110:372-381
Lui, Hansen; Zhang, Jiasheng; Makinson, Stefanie R et al. (2016) Progranulin Deficiency Promotes Circuit-Specific Synaptic Pruning by Microglia via Complement Activation. Cell 165:921-35
Paz, Jeanne T; Huguenard, John R (2015) Optogenetics and epilepsy: past, present and future. Epilepsy Curr 15:34-8