Neuronal and Network Mechanisms of Electrocortical Stimulation

Electrocortical stimulation (ECS) mapping is a procedure used during brain surgeries, for example when treating diseases like epilepsy or when removing brain tumors. ECS mapping helps surgeons locate areas of the cerebral cortex (the outer part of the brain) that are important for everyday tasks like movement and speech. ECS mapping has been used for decades, and is considered the "gold-standard" tool for locating important areas of cortex. Despite this long history, there is still no clear understanding of exactly how ECS works. The goal of this study is to learn details about the effects ECS has on the brain. The main questions the study aims to answer are: 1) how ECS affects the neurons of the cortex at the stimulation site; and 2) how ECS impacts brain regions that are critically important for human speech and language. These so-called "critical sites" can be physically distant from one another on the brain's surface, requiring extensive ECS mapping and long surgeries. Critical sites are thought to be part of a speech/language network of brain areas, and so the study's goal is to learn about how they are connected. In some participants, the brain's surface will also be slightly cooled. This is a painless procedure that does not harm the brain's function, but could provide insight as to which parts of the brain (the surface, or deeper parts) are responsible for the effects of ECS. By improving the understanding of how ECS affects the brain and improving the ability to identify critical sites, this study could potentially lead to shorter surgeries and better outcomes for future individuals who need this care. Participants will be recruited from among individuals who are undergoing brain surgery for epilepsy treatment or tumor removal. Participants will complete simple tasks like reading words or naming pictures, similar to standard testing that is already performed during their hospital stay.

Sex

All

Minimum age

18 Years

Maximum age

80 Years

Inclusion Criteria:

* Requiring awake, cortical mapping for brain tumor resection or implantation of intracranial electrodes for extraoperative monitoring for epilepsy
* For extraoperative patients: Planned electrode coverage including at least parts of frontal and temporal or parietal lobes, preferably both anterior (inferior frontal gyrus) and posterior language areas (superior temporal gyrus) in the language dominant hemisphere
* For intraoperative patients: Planned craniotomy including parts of both frontal and temporal anterior and posterior language areas in the language dominant hemisphere.

Exclusion Criteria:

* Significant language or speech impairment, including but not limited to aphasia, dysarthria, and apraxia of speech, consistently preventing patient from speaking words
* Non English-speaking (because this is a study of language networks, and second language could be encoded differently)
* Impaired cognitive function, as determined by neurological testing, such that the patient cannot follow test instructions or provide written informed consent
* Tumor infiltrating, or within 1 cm of, multiple of the cortical or subcortical areas studied in this proposal (inferior frontal gyrus, precentral gyrus, superior temporal gyrus)
* Ferromagnetic implants that are MRI incompatible or other contraindications to MRI
* Pregnancy