High‑Performance Flexible Microneedle Array as a Low‑Impedance Surface Biopotential Dry Electrode for Wearable Electrophysiological Recording and Polysomnography

Microneedle array(MNA)electrodes are an effective solution to achieve high-quality surface biopotential recording without the coordination of conductive gel and are thus very suitable for long-term wearable applications.Existing schemes are limited by flexibility,biosafety,and manufacturing costs,which create large barriers for wider applications.Here,we present a novel flexible MNA electrode that can simultaneously achieve flexibility of the substrate to fit a curved body surface,robustness of microneedles to penetrate the skin without fracture,and a simplified process to allow mass production.The compatibility with wearable wireless systems and the short preparation time of the electrodes significantly improves the comfort and convenience of electrophysiological recording.The normalized electrode–skin contact impedance reaches 0.98 kΩcm^(2)at 1 kHz and 1.50 kΩcm^(2)at 10 Hz,a record low value compared to previous reports and approximately 1/250 of the standard electrodes.The morphology,biosafety,and electrical/mechanical properties are fully characterized,and wearable recordings with a high signal-to-noise ratio and low motion artifacts are realized.The first reported clinical study of microneedle electrodes for surface electrophysiological monitoring was conducted in tens of healthy and sleep-disordered subjects with 44 nights of recording(over 8 h per night),providing substantial evidence that the electrodes can be leveraged to substitute for clinical standard electrodes.

Visual response characteristics of neurons in the second visual area of marmosets

The physiological characteristics of the marmoset second visual area(V2) are poorly understood compared with those of the primary visual area(V1). In this study, we observed the physiological response characteristics of V2 neurons in four healthy adult marmosets using intracortical tungsten microelectrodes. We recorded 110 neurons in area V2, with receptive fields located between 8° and 15° eccentricity. Most(88.2%) of these neurons were orientation selective, with half-bandwidths typically ranging between 10° and 30°. A significant proportion of neurons(28.2%) with direction selectivity had a direction index greater than 0.5. The vast majority of V2 neurons had separable spatial frequency and temporal frequency curves and, according to this criterion, they were not speed selective. The basic functional response characteristics of neurons in area V2 resemble those found in area V1. Our findings show that area V2 together with V1 are important in primate visual processing, especially in locating objects in space and in detecting an object's direction of motion. The methods used in this study were approved by the Monash University Animal Ethics Committee, Australia(MARP 2009-2011) in 2009.

Contralateral S1 function is involved in electroacupuncture treatment-mediated recovery after focal unilateral M1 infarction

Acupuncture at acupoints Baihui(GV20)and Dazhui(GV14)has been shown to promote functional recovery after stroke.However,the contribution of the contralateral primary sensory cortex(S1)to recovery remains unclear.In this study,unilateral local ischemic infarction of the primary motor cortex(M1)was induced by photothrombosis in a mouse model.Electroacupuncture(EA)was subsequently performed at acupoints GV20 and GV14 and neuronal activity and functional connectivity of contralateral S1 and M1 were detected using in vivo and in vitro electrophysiological recording techniques.Our results showed that blood perfusion and neuronal interaction between contralateral M1 and S1 is impaired after unilateral M1 infarction.Intrinsic neuronal excitability and activity were also disturbed,which was rescued by EA.Furthermore,the effectiveness of EA treatment was inhibited after virus-mediated neuronal ablation of the contralateral S1.We conclude that neuronal activity of the contralateral S1 is important for EA-mediated recovery after focal M1 infarction.Our study provides insight into how the S1-M1 circuit might be involved in the mechanism of EA treatment of unilateral cerebral infarction.The animal experiments were approved by the Committee for Care and Use of Research Animals of Guangzhou University of Chinese Medicine(approval No.20200407009)April 7,2020.

An injectable,self-healable,and reusable PEDOT:PSS/PVA hydrogel patch electrode for epidermal electronics

Injectability empowers conductive hydrogels to transcend traditional limitations,unlocking a realm of possibilities for innovative medical,wearable,and therapeutic applications that can significantly enhance patient care and quality of life.Here,we report an injectable,self-healable,and reusable hydrogel obtained by mixing the concentrated poly(3,4-ethylenedioxythiophene)doped with polystyrene sulfonate(PEDOT:PSS)suspension(~2 wt.%solid content),polyvinyl alcohol(PVA),and borax.Leveraging the presence of reversible borax/hydroxyl bonds and multiple hydrogen bonds,this PEDOT:PSS/PVA hydrogel exhibits notable shear-thinning behavior and self-healing capabilities,enabling it to be injected as a gel fiber from a syringe.As-prepared injectable hydrogel also demonstrates an ultra-low modulus(~2.5 MPa),reduced on-skin impedance(~45%of commercial electrodes),and high signal-to-noise ratio(SNR)(~15-22 dB)in recording of electrocardiography(ECG),electromyography(EMG),and electroencephalogram(EEG)signals.Furthermore,the injectable hydrogels can be remolded and reinjected as the reusable electrodes,maintaining nearly identical electrophysiological recording capabilities and brain-computer interface(BCI)performance compared to commercial wet electrodes.With their straightforward fabrication,excellent material properties and electronic performance,ease of cleaning,and remarkable reusability,our injectable PEDOT:PSS/PVA hydrogels hold promise for advancements in BCI based electronics and wearable bioelectronics.

Plasticity of Sniffing Pattern and Neural Activity in the Olfactory Bulb of Behaving Mice During Odor Sampling,Anticipation,and Reward

The olfactory bulb(OB) is the first relay station in the olfactory system.In the OB,mitral/tufted cells(M/Ts),which are the main output neurons,play important roles in the processing and representation of odor information.Recent studies focusing on the function of M/Ts at the single-cell level in awake behaving mice have demonstrated that odor-evoked firing of single M/Ts displays transient/long-term plasticity during learning.Here,we tested whether the neural activity of M/Ts and sniffing patterns are dependent on anticipation and reward in awake behaving mice.We used an odor discrimination task combined with in vivo electrophysiological recordings in awake,head-fixed mice,and found that,while learning induced plasticity of spikes and beta oscillations during odor sampling,we also found plasticity of spikes,beta oscillation,sniffing pattern,and coherence between sniffing and theta oscillations during the periods of anticipation and/or reward.These results indicate that the activity of M/Ts plays important roles not only in odor representation but also in salience-related events such as anticipation and reward.