Direct cortical stimulation induces short-term modulation of neural oscillations in humans

Patterned brain stimulation is commonly employed to modulate brain circuits and treat neuropsychiatric disorders. Although widely used in clinical settings, there remains limited understanding of how stimulation alters neural oscillations and how these effects relate to baseline evoked network responses. To address this question, we applied 15 minutes of 10Hz focal electrical stimulation delivered as 5-s trains separated by 10-s rest intervals, a pattern resembling 'excitatory' transcranial magnetic stimulation, to 14 patients with epilepsy undergoing intracranial electroencephalography in premotor, parietal, and temporal cortical sites. We quantified spectral features of cortico-cortical evoked potentials (CCEPs) before and after stimulation. We hypothesized that the temporal and spectral components of the CCEP predicted the location and degree of stimulation-induced modulation. Across patients, low frequency power (alpha, beta) showed the broadest change, while the magnitude of change was stronger in high frequencies (beta, gamma). Next, we demonstrated that regions with stronger pre-stimulation evoked spectral responses were more likely to exhibit larger post-stimulation spectral changes. These findings were specific to frequency in a temporal window. Post-stimulation power changes were driven by interaction between direction of change in pre-stimulation power and temporal window. Finally, regions exhibiting early increases and late decreases in pre-stimulation power exhibited power changes after stimulation. These patterns were consistent across premotor, parietal, and temporal sites, but the magnitude and latency varied by stimulation location. Together, these findings demonstrate that time-frequency pre-stimulation features predict post-stimulation modulation of human neural oscillations and highlight temporally specific, state-dependent properties of stimulation responses in humans, thereby improving our understanding of stimulation-associated changes in human brain networks and helping inform more effective brain stimulation techniques.