This is a mentored Research Scientist Career Development Award for research and training support. The human default network (DN) is a constellation of functionally connected brain regions that is engaged during introspective thought and suppressed during sensorimotor processing. Abnormal patterns of activity within the DN have been linked to the cognitive and behavioral impairments associated with a host of neuropsychiatric disorders such as schizophrenia, depression, autism spectrum disorder, and ADHD. Remarkably little is known about the electrophysiological dynamics of the DN, which would inform a mechanistic understanding of abnormal function at a systems level. The overall goal of these experiments is to define the electrophysiological dynamics of the DN using electrocorticography (ECoG) and high frequency scalp-based electroencephalography (EEG). ECoG, the practice of using electrodes placed directly on the exposed surface of the brain to record electrical activity from the cerebral cortex, will be used to determine the rapid and dynamic timing of neural responses within the DN during an evoked event-related introspective, 'self-referential' task and during DN suppression engendered by a linguistic task. This technique will also be used to characterize the interactions between the DN and a language or task positive network. As a complementary method, EEG will be employed to localize electrical activity to the deep cortical regions of the DN. These experiments will characterize the neurophysiological dynamics of the default network in humans. They will contribute to understanding of the biological utility, relevance, and function of the default network and provide greater insight into how reported network abnormalities contribute to underlying pathology.