The processing of these acoustic impressions presumably takes place in areas of the brain stem and the auditory cortex, resulting in a conscious perception ( 11, 12). For instance, if a tone with a frequency of 335 Hz is presented to one ear and a tone with 345 Hz to the other ear, a beat signal with a modulated frequency of 10 Hz is produced. Among others, there are reports that music ( 6), rhythmic tone sequences ( 7, 8), and the acoustic presentation of certain frequencies ( 9) can improve motor symptoms in PD.īinaural beat stimulation (BBS) represents a specific type of acoustic stimulation and describes acoustic impressions that occur when two sounds with slightly different frequencies are delivered separately to each ear ( 10). However, several potential non-invasive therapies have emerged in the recent literature that may be complementary to drug therapy, such as acoustic stimulation. Increasing motor fluctuations often complicate the oral therapy in later stages of the disease, so that invasive therapy options are to be considered. In PD, motor symptoms have been especially attributed to enhanced beta and reduced gamma activity in basal ganglia-cortical loops ( 4).Ĭurrently, symptomatic therapy mainly focuses on dopaminergic agents, that are associated with significant side effects such as dyskinesia and impulse control disorders ( 5). In the healthy brain, frequency bands have been traditionally segregated into delta (0.5–3 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (13–30 Hz), and gamma (>30 Hz) oscillations and play a key role for information processing ( 3). Growing evidence highlights a key role of altered neural oscillations in the pathology of patients with PD ( 2). The clinical presentation of PD is characterized by motor symptoms, such as bradykinesia in combination with rigidity and resting tremor. Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease ( 1). However, more studies are needed to fully characterize the clinical relevance of BBS and to further optimize its ameliorating effects. Moreover, the positive effects of CAS underline the general positive potential for improvement of motor function by acoustically supported therapeutic approaches. In this study, we found an improvement of resting tremor when applying BBS in the gamma frequency band OFF medication. For CAS, we did not observe an improvement in specific symptoms but rather an overall beneficial effect on motor performance (MDS-UPDRS total score OFF medication: F (2,48) = 4.17, p = 0.021 wearable scores: F (2,48) = 2.46, p = 0.097). However, BBS did not exert a general positive effect on motor symptoms as assessed via MDS-UPDRS ( F (2,48) = 1.00, p = 0.327). Repeated measures ANOVA revealed that BBS improved resting tremor on the side of the more affected limb in the OFF condition, as measured by wearables ( F (2,48) = 3.61, p = 0.035). We assessed effects on motor performance using Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) and two validated commercially available portable devices (Kinesia ONE™ and Kinesia 360™) measuring motor symptoms such as dyskinesia, bradykinesia, and tremor. For BBS, a modulated frequency of 35 Hz was used (left: 320 Hz right: 355 Hz) and for CAS 340 Hz on both sides. The acoustic stimulation phase was divided into two blocks including BBS and conventional acoustic stimulation (CAS) as a control condition. Each drug condition consisted of two phases (no stimulation and acoustic stimulation). The study was conducted with (ON) and without dopaminergic medication (OFF). In this double-blind, randomized study, 25 PD patients were recruited. Several studies suggest that oscillations in the gamma-frequency range (>30 Hz) serve a prokinetic function in PD. Scalp electroencephalography studies in healthy subjects indicate that specifically binaural beat stimulation (BBS) in the gamma frequency range is associated with synchronized cortical oscillations at 40 Hertz (Hz). 2Center for Mind, Brain and Behavior (CMBB), Philipps-University Marburg, Marburg, GermanyĪcoustic stimulation can improve motor symptoms in Parkinson’s disease (PD) and might therefore represent a potential non-invasive treatment option. 1Department of Neurology, Philipps-University Marburg, Marburg, Germany.Alexander Calvano 1 * Lars Timmermann 1,2 Philipp Alexander Loehrer 1,2 Carina Renate Oehrn 1,2 Immo Weber 1
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