This project aims to improve cortical mapping in neurosurgical patients, with a focus on speech and language function. Neurosurgical treatment of tumor and epilepsy requires careful planning to avoid post- operative deficits in the patient's ability to speak. This requires a method of identifying cortical regions critically involved in speech function (so-called """"""""eloquent cortex""""""""). Currently, this is accomplished by electrical stimulation mapping (ESM), whereby electric shocks are delivered to the cortex as the patient attempts a speech production task. However, this method is time consuming and increases the risk of seizure. Alternatively, the brain's intrinsic activity could be imaged during speech production tasks. Ideally, this method would be passive - i.e., it would not require the invasive use of electrical stimulation - and provide high spatial and temporal resolution for measuring cortical activation. Such a method can be provided by measuring the ongoing electrical activity of the cortex (electrocorticography, ECoG), in so far as a measure of """"""""activation"""""""" can be extracted. Recent ECoG work has identified the high-gamma band, consisting of rapid (>70 Hz) electrical fluctuations, as a robust indicator of cortical activation with high spatial and temporal resolution. For example, animal and human studies show that power in the high-gamma band is strongly correlated with local increases in blood flow and single-unit spiking rates. Thus, ECoG can be used to measure task-specific cortical activations. The proposed project aims to develop ECoG as a cortical mapping method, both as an alternative to ESM for neurosurgical planning and as a means of addressing fundamental questions in linguistic neuroscience. ECoG will be used to examine the roles of different cortical areas during a variety of auditory and language tasks. The long-term goal is to develop a battery of tasks to allow rapid functional mapping of individual patients for surgical planning. Relevance: Treatment of tumors and epilepsy often requires the surgical removal of significant portions of the brain. In order to avoid parts of the brain critical to the patient's ability to speak, a technique is required to rapidly and accurately map the human brain with respect to speech function.
This research aims to improve techniques of brain mapping in neurosurgical patients, and to address questions about human language of broad clinical relevance in the neurological sciences.
| Edwards, Erik; Chang, Edward F (2013) Syllabic (?2-5 Hz) and fluctuation (?1-10 Hz) ranges in speech and auditory processing. Hear Res 305:113-34 |
| Chang, Edward F; Edwards, Erik; Nagarajan, Srikantan S et al. (2011) Cortical spatio-temporal dynamics underlying phonological target detection in humans. J Cogn Neurosci 23:1437-46 |
| Edwards, Erik; Nagarajan, Srikantan S; Dalal, Sarang S et al. (2010) Spatiotemporal imaging of cortical activation during verb generation and picture naming. Neuroimage 50:291-301 |
| Edwards, Erik; Soltani, Maryam; Kim, Won et al. (2009) Comparison of time-frequency responses and the event-related potential to auditory speech stimuli in human cortex. J Neurophysiol 102:377-86 |
