Stable modulation of neuronal oscillations produced through brain-machine equilibrium

Abstract

Brain stimulation is predominantly delivered independent of ongoing activity, whereas closed-loop systems can modify activity through interaction. They have the unrealised potential to continuously bind external stimulation to specific dynamics of a neural circuit. Such manipulations are particularly suited to rhythmic activities, where neuronal activity is organised in oscillatory cycles. Here, we developed a fast algorithm that responds on a cycle-by-cycle basis to stimulate basal ganglia nuclei at predetermined phases of successive cortical beta cycles in parkinsonian rats. Using this approach, we demonstrate a stable brain-machine interaction. An equilibrium emerged between the modified brain signal and feedback-dependent stimulation pattern, which led to sustained amplification or suppression of the oscillation. Sustained beta amplification slowed movement speed by altering the mode of locomotion. Integrating an external stimulus with network activity in this way could be used to correct maladaptive activities and to define the role of oscillations in fundamental brain functions.

Stimulating at the right time to recover network states in a model of the cortico-basal ganglia-thalamic circuit

“…Specifically, we used phase non-specific stimulation at 18 Hz, using the above gating criteria but with fixed instantaneous frequency (i.e., constant phase). As a second control, designed to identify whether spectral effects resulted from the phase tracking algorithm, we also “played back” stimulation patterns [ 101 ] but in a different model instance, where the actual phase was no longer matched to the model dynamics.…”