doi:10.1523/JNEUROSCI.1885-21.2022engBräcklein, MarioBarsakcioglu, Deren Y.Del Vecchio, AlessandroIbáñez, JaimeFarina, DarioReading and modulating Cortical ß rursts from motor unit spiking activityART-2022-131697β Oscillations (13–30 Hz) are ubiquitous in the human motor nervous system. Yet, their origins and roles are unknown. Traditionally, β activity has been treated as a stationary signal. However, recent studies observed that cortical β occurs in “bursting events,” which are transmitted to muscles. This short-lived nature of β events makes it possible to study the main mechanism of β activity found in the muscles in relation to cortical β. Here, we assessed whether muscle β activity mainly results from cortical projections. We ran two experiments in healthy humans of both sexes (N = 15 and N = 13, respectively) to characterize β activity at the cortical and motor unit (MU) levels during isometric contractions of the tibialis anterior muscle. We found that β rhythms observed at the cortical and MU levels are indeed in bursts. These bursts appeared to be time-locked and had comparable average durations (40–80 ms) and rates (approximately three to four bursts per second). To further confirm that cortical and MU β have the same source, we used a novel operant conditioning framework to allow subjects to volitionally modulate MU β. We showed that volitional modulation of β activity at the MU level was possible with minimal subject learning and was paralleled by similar changes in cortical β activity. These results support the hypothesis that MU β mainly results from cortical projections. Moreover, they demonstrate the possibility to decode cortical β activity from MU recordings, with a potential translation to future neural interfaces that use peripheral information to identify and modulate activity in the central nervous system.2022http://zaguan.unizar.es/record/12113810.1523/JNEUROSCI.1885-21.2022http://zaguan.unizar.es/record/121138oai:zaguan.unizar.es:121138info:eu-repo/grantAgreement/EC/H2020/847648 /EU/Junior Leader la Caixa Postdoctoral Fellowship Programme: Shaping the new generation of leaders in research/JUNIOR LEADERThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 847648 -JUNIOR LEADERinfo:eu-repo/grantAgreement/EC/H2020/899626/EU/NIMA: Non-invasive Interface for Movement Augmentation/NIMAThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 899626-NIMAJOURNAL OF NEUROSCIENCE 42, 17 (2022), 3611-3621byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess