Browsing by Author "Ojala, Reetta"

Beta frequency (15-25 Hz) oscillations in the extracellular field potential recorded by cortical EEG and depth electrodes have been connected to stopping. Especially short increases in beta power, so called beta bursts, occur more frequently close to stopping an ongoing movement or when cancelling a planned action. However, there are discrepancies about the causal role of these beta bursts on stopping. Although some studies indicate causality, in others the bursts occur too late for being causal or their number does not increase prior to stopping. One explanation to the disagreement may lie in the behavioral task commonly used to study the neural correlates of action inhibition, the stop signal task. In this task the movement is cancelled before it starts, and actual stopping is thus hidden from the experimenter. Instead, an estimated stop signal reaction time is mathematically modelled. It is likely that this reaction time varies trial by trial, which causes inaccuracy in the results. We were able to define an exact stopping time using head fixed rats running on a treadmill. This enabled us to align brain activity precisely with stopping. With this task, we showed that the number of transient beta bursts increases just prior to stopping. Moreover, the increase correlates with the velocity. These results indicate that beta bursts are causal to stopping. Beta bursts have been noted to be disturbed in Parkinson’s disease and our results may open new doors for early diagnoses or treatments.