Magnetic neuromodulation has outstanding promise for the development of novel neural interfaces without direct physical intervention with the brain. Here we tested the utility of Magneto in the adult somatosensory cortex by performing whole-cell intracellular recordings in vitro and extracellular recordings in freely moving mice. Results show that magnetic stimulation does not alter subthreshold membrane excitability or contribute to the generation of action potentials in virally transduced neurons expressing Magneto.Recently introduced Magneto (Wheeler et al., 2016) might provide the highly sought after neuromagnetic actuation in a cell-targeted manner. Some of the excitement about Magneto originates from its design which is comprised of a calcium-permeable non-selective cation channel (Transient receptor potential cation channel subfamily V member 4, TRPV4) fused to the paramagnetic protein ferritin (Wheeler et al., 2016) . This single-construct approach provides a simplified mean for magnetic intervention with neuronal activity.Here, we used lentiviral delivery of Magneto linked to mCherry (Magneto2.0-P2A-mCherry), expressed under the control of ubiquitin promoter for >2 weeks (Fig. 1a) before observing and interfering with neural activity (see Methods online), and after confirming successful cleavage of Magneto from mCherry (Suppl.Fig. 2a-3) and the subcellular analysis of the expressed protein localization (Suppl.Fig. 2b) in a neuronal cell line . Chronic extracellular recordings in freely moving mice (Allen et al., 2003; Celikel et al., 2004; Clem et al., 2008) with 15 tetrodes enabled high-density sampling of neural activity in the vicinity of transduced cells, and yielded well-isolated (Suppl.Fig. 4) , stable units (Fig. 1b) . Comparison of firing rates within cells across magnetic stimulus conditions (off vs on) showed that magnetic stimulation does not alter the rate of action potentials (APs; Fig. 1c ); neither does it modulate the inter-spike interval within cells, nor spike-timing across single units recorded from the same tetrode (Suppl.Fig. 5,6) . The lack of spiking was not because neurons could not 1

BackgroundActive sensing is crucial for navigation. It is characterized by self-generated motor action controlling the accessibility and processing of sensory information. In rodents, active sensing is commonly studied in the whisker system. As rats and mice modulate their whisking contextually, they employ frequency and amplitude modulation. Understanding the development, mechanisms, and plasticity of adaptive motor control will require precise behavioral measurements of whisker position.FindingsAdvances in high-speed videography and analytical methods now permit collection and systematic analysis of large datasets. Here, we provide 6,642 videos as freely moving juvenile (third to fourth postnatal week) and adult rodents explore a stationary object on the gap-crossing task. The dataset includes sensory exploration with single- or multi-whiskers in wild-type animals, serotonin transporter knockout rats, rats received pharmacological intervention targeting serotonergic signaling. The dataset includes varying background illumination conditions and signal-to-noise ratios (SNRs), ranging from homogenous/high contrast to non-homogenous/low contrast. A subset of videos has been whisker and nose tracked and are provided as reference for image processing algorithms.ConclusionsThe recorded behavioral data can be directly used to study development of sensorimotor computation, top-down mechanisms that control sensory navigation and whisker position, and cross-species comparison of active sensing. It could also help to address contextual modulation of active sensing during touch-induced whisking in head-fixed vs freely behaving animals. Finally, it provides the necessary data for machine learning approaches for automated analysis of sensory and motion parameters across a wide variety of signal-to-noise ratios with accompanying human observer-determined ground-truth.