Abstract:

In neurodegenerative disorders such as Parkinson’s disease (PD), deep brain stimulation (DBS) is a desirable approach when the medication is less effective for treating the symptoms. DBS incorporates transferring electrical pulses to a specific tissue of the central nervous system, obtaining therapeutic results by modulating the neuronal activity of that region. DBS has certain advantages such as reversibility and adjustability features over medication, since the neuronal firing patterns can be recorded and used to alter the parameters of the DBS signal (Benabid et al., 2009). One of the DBS indications is its ability to suppress the abnormal neuronal activity to treat symptoms like tremor, akinesia and dystonia. Although the mechanism of DBS is not fully understood, the inhibition of neurons, entrainment of bursting neurons and activation of axons has been associated with DBS therapy (Chiken and Nambu, 2016). Electric fields induced by DBS generally disrupt any abnormal information flow coming from the cortex to the basal ganglia neurons. DBS signals also increase and regularize the neuronal firing rates by direct activation of the axons of the stimulated neuron. This regularization of neuronal firing rate prohibits the oscillatory and bursting abnormalities of the basal ganglia neurons, leading to highly therapeutic results in PD. The therapeutic effects of DBS are enhanced once it is used in a closed loop paradigm. The cortical and pallidal discharge patterns of neurons are more improved by closed loop DBS rather than traditional open loop stimulations (Rosin et al., 2011). DBS is mainly targeted at subthalamic nucleus (STN) or globus pallidus externa (GPe) cells to disrupt the thalamo-cortical synchronizations seen in PD. Therefore,the local field potential (LFP) recorded from a population of the STN cells is often used as the feedback variable for DBS parametrization.Retrospective studies mainly focused on adjusting the stimulation amplitude based on the recorded LFP (Popovych et al., 2017). However, adapting the frequency of stimulation might provide superior results in desynchronizing the coupling patterns of STN-GPe. In addition, high frequency stimulation (HFS)typically used in DBS, significantly increases the device battery usage. In contrast, adapting the frequency of stimulation to a protocol where HFS is only used when high desynchronization is needed, can expand the battery lifespan and reduces the necessity of costly battery replacement surgeries (Lyons et al., 2004).