Objective . This study aimed to design and evaluate a high-speed online steady-state visually evoked potential (SSVEP)-based brain–computer interface (BCI) in an optical see-through (OST) augmented reality (AR) environment. Approach . An eight-class BCI was designed in an OST-AR headset which is wearable and allows users to see the user interface of the BCI and the device to be controlled in the same view field via the OST head-mounted display. The accuracies, information transfer rates (ITRs), and SSVEP signal characteristics of the AR-BCI were evaluated and compared with a computer screen-based BCI implemented with a laptop in offline and online cue-guided tasks. Then, the performance of the AR-BCI was evaluated in an online robotic arm control task. Main results . The offline results obtained during the cue-guided task performed with the AR-BCI showed maximum averaged ITRs of 65.50 ± 9.86 bits min ⁻¹ according to the extended canonical correlation analysis-based target identification method. The online cue-guided task achieved averaged ITRs of 65.03 ± 11.40 bits min ⁻¹ . The online robotic arm control task achieved averaged ITRs of 45.57 ± 7.40 bits min ⁻¹ . Compared with the screen-based BCI, some limitations of the AR environment impaired BCI performance and the quality of SSVEP signals. Significance . The results showed the potential for providing a high-performance brain–control interaction method by combining AR and BCI. This study could provide methodological guidelines for developing more wearable BCIs in OST-AR environments and will also encourage more interesting applications involving BCIs and AR techniques.

Objective. Transcranial temporally interfering stimulation (tTIS) is a noninvasive neuromodulation method, which has been reported to be able to affect the activity of small neuronal populations. To pinpoint smaller regions of the brain, a multi-channel tTIS strategy is proposed with larger numbers of electrodes and multiple sets of interfering fields. Approach. First, a computational model is adopted to prove the concept of multi-channel tTIS theoretically. Besides, animal experiments are implemented to activate motor cortex neurons in living mice and different frequencies are attempted. Finally, to better understand the envelope modulation properties of the two applied fields, tissue phantom measurement is conducted. Main results. The focality of six-channel (six electrode pairs) tTIS is increased by 46.7% and 70.2% respectively, compared with that of single-channel tTIS when maximal amplitude value drops by 3 dB and 6 dB in a numerical computation experiment. Furthermore, the focality of multi-channel tTIS is less sensitive to the electrode position. Confirmed with the myoelectricity signal, the movement frequencies of the contralateral forepaw are consistent with the corresponding difference frequencies. What is more, compared to single-channel (one electrode pair) tTIS with multi-channel (three electrode pairs) tTIS, the intensity of multi-channel tTIS stimulation is decreased by 28.5% on average in animal experiments. The c-fos-positive neurons of the target region are significantly higher than that of the non-target region. Results of the modulated envelope distribute around the whole region and its amplitude reaches a maximum at the interfering region. Significance. Both computational modeling and animal experiment validate the feasibility of the proposed multi-channel tTIS strategy and confirm that it can enhance focality and reduce scalp sensation.

Neural stem cells (NSCs) transplantation is an attractive and promising treatment strategy for spinal cord injury (SCI). Various pathological processes including the severe inflammatory cascade and difficulty in stable proliferation and differentiation of NSCs limit its application and translation. Here, a novel physico‐chemical bifunctional neural stem cells delivery system containing magnetic nanoparticles (MNPs and methylprednisolone (MP) is designed to repair SCI, the former regulates NSCs differentiation through magnetic mechanical stimulation in the chronic phase, while the latter alleviates inflammatory response in the acute phase. The delivery system releases MP to promote microglial M2 polarization, inhibit M1 polarization, and reduce neuronal apoptosis. Meanwhile, NSCs tend to differentiate into functional neurons with magnetic mechanical stimulation generated by MNPs in the static magnetic field, which is related to the activation of the PI3K/AKT/mTOR pathway. SCI mice achieve better functional recovery after receiving NSCs transplantation via physico‐chemical bifunctional delivery system, which has milder inflammation, higher number of M2 microglia, more functional neurons, and axonal regeneration. Together, this bifunctional NSCs delivery system combined physical mechanical stimulation and chemical drug therapy is demonstrated to be effective, which provides new treatment insights into clinical transformation of SCI repair.

Objective: Acoustoelectric Brain Imaging (ABI) is a potential method for mapping brain electrical activity with high spatial resolution (millimeter). To resolve the key issue for eventual realization of ABI, testing that recorded acoustoelectric (AE) signal can be used to decode intrinsic brain electrical activity, the experiment of living rat SSVEP measurement with ABI is implemented. Method: A 1-MHz ultrasound transducer is focused on the visual cortex of anesthetized rat. With visual stimulus, the electroencephalogram and AE signal are simultaneously recorded with Pt electrode. Besides, with FUS transducer scanning at the visual cortex, corresponding AE signals at different spatial positions are decoded and imaged. Results: Consistent with the directly measured SSVEP, decoded AE signal presents a clear event-related spectral perturbation (ERSP). And, decoded AE signal is of high amplitude response at the base and harmonics of the visual stimulus frequency. What's more, for timing signal, a significant positive amplitude correlation is observed between decoded AE signal and simultaneously measured SSVEP. In addition, the mean SNRs of SSVEP and decoded AE signal are both significantly higher than that of background EEG. Finally, with one fixed recording electrode, the active area with an inner diameter of 1mm is located within the 4 mm×4 mm measurement region. Conclusion: Experimental results demonstrate that the millimeter-level spatial resolution SSVEP measurement of living rat is achieved through ABI for the first time. Significance: This study confirms that ABI should shed light on high spatiotemporal resolution neuroimaging.

Transcranial focused ultrasound (tFUS) has great potential in brain imaging and therapy. However, the structural and acoustic differences of the skull will cause a large number of technical problems in the application of tFUS, such as low focus energy, focal shift, and defocusing. To have a comprehensive understanding of the skull effect on tFUS, this study investigated the effects of the structural parameters (thickness, radius of curvature, and distance from the transducer) and acoustic parameters (density, acoustic speed, and absorption coefficient) of the skull model on tFUS based on acrylic plates and two simulation methods (self-programming and COMSOL). For structural parameters, our research shows that as the three factors increase the unit distance, the attenuation caused from large to small is the thickness (0.357 dB/mm), the distance to transducer (0.048 dB/mm), and the radius of curvature (0.027 dB/mm). For acoustic parameters, the attenuation caused by density (0.024 dB/30 kg/m³) and acoustic speed (0.021 dB/30 m/s) are basically the same. Additionally, as the absorption coefficient increases, the focus acoustic pressure decays exponentially. The thickness of the structural parameters and the absorption coefficient of the acoustic parameters are the most important factors leading to the attenuation of tFUS. The experimental and simulation trends are highly consistent. This work contributes to the comprehensive and quantitative understanding of how the skull influences tFUS, which further enhances the application of tFUS in neuromodulation research and treatment.

Objective . Electroencephalography is a technique for measuring normal or abnormal neuronal activity in the human brain, but its low spatial resolution makes it difficult to locate the precise locations of neurons due to the volume conduction effect of brain tissue. Approach . The acoustoelectric (AE) effect has the advantage of detecting electrical signals with high temporal resolution and focused ultrasound with high spatial resolution. In this paper, we use dipoles to simulate real single and double neurons, and further investigate the localization and decoding of single and double dipoles based on AE effects from numerical simulations, brain tissue phantom experiments, and fresh porcine brain tissue experiments. Main results . The results show that the localization error of a single dipole is less than 0.3 mm, the decoding signal is highly correlated with the source signal, and the decoding accuracy is greater than 0.94; the location of double dipoles with an interval of 0.4 mm or more can be localized, the localization error tends to increase as the interval of dipoles decreases, and the decoding accuracy tends to decrease as the frequency of dipoles decreases. Significance . This study localizes and decodes dipole signals with high accuracy, and provides a technical method for the development of EEG.