The quantification and characterisation of ramping firing rates and regional differences in the basal ganglia

The basal ganglia are part of the neural circuit involved in inhibitory control. Gradual, consistent changes in firing rate (ramps) have been found in the basal ganglia during 'hold' periods of different behavioural tasks involving inhibitory control. However, the properties of these ramps, such as startpoints, endpoints, amplitude, length and single-trial properties, have not yet been characterised in detail. In order to obtain these properties accurately, we tested and adapted various methods from the wind-ramp and changepoint literature. Specifically, we used pruned exact linear time (PELT) to detect changepoints for ramp detection. Compared to other algorithms, the PELT method was found to have the best performance. Utilising PELT, we then analysed a large data set of electrophysiological recordings in rats performing behavioural tasks to determine the properties of firing rate ramps during hold periods. First, we established that these ramps exist during the hold period in a stop-signal task. Second, we demonstrate that these ramp properties vary widely across the basal ganglia. Third, at the single-trial level, we show that neurons with detected ramps could have different underlying spiking patterns, for example, stepping or ramping. Finally, we investigated the entrainment of neurons in the basal ganglia and found that different waveforms can influence entrainment properties at gamma frequencies.