When DBS high-frequency stimulation is applied to the STN, the model shows, that replaces the overwhelming beta input received by the FSIs and restores their excitability.
Reinvigorated and freed from those beta shackles, the interneurons resume producing gamma oscillations (at about half the DBS stimulation frequency, typically at 135 Hz) that then suppress the beta activity of the MSNs. With the MSNs no longer producing too much beta, the loop leading back to the STN and then to the FSIs is no longer dominated by that frequency.
“DBS stops the beta from propagating towards FSIs so that it is no longer amplified, and then, by additionally exciting FSIs, restores the ability of FSIs to produce strong gamma oscillations, that will in turn inhibit beta at its source,” Adam said.
