Electric shock causes fear-like persistent behavioral response in the nematode Caenorhabditis elegans

Electricity is widely utilized as environmental stimulus to sense the world by many animal species. Despite its importance, however, molecular and physiological mechanisms for responding to electrical stimulus have been far less understood compared to other sensory stimuli. Here we report novel behavioral responses to electrical stimulus of the nematode C. elegans. When the animals on food are stimulated by alternating current, their movement speed suddenly increases more than 2-fold, which persists for a few minutes even after the electrical stimulation is terminated. Genetic analyses reveal that voltage-gated channels are required for the response, possibly as the sensors, and neuropeptide signaling suppresses the persistent response. Additional behavioral analysis reveals that, in addition to the persistence, the animal's response to electrical shock is scalable and has a negative valence, which are recently regarded as emotion primitives, suggesting that the response may reflect a primitive form of "fear" of animals.

Comparison of Sympathetic Skin Response (SSR) between Electrical and Acoustic Stimuli in a Healthy Pediatric Population

Data in the literature report that latency and morphology in the cutaneous sympathetic skin response (SSR) do not change according to the type of stimulus delivered, unlike the amplitude which shows greater values in relation to the intensity of the physical impact caused in patient. Since the acoustic stimulus represents a method better tolerated by the pediatric patient, the aim of this study is to evaluate the presence or absence of significant differences in SSR between electrical and acoustic stimuli. The SSR was performed for each child of 18 recruited in this study, deriving from the palm of the hand and the sole of the foot and initially delivering an electrical stimulus at the level of the median nerve at the wrist. Two acoustic stimuli were subsequently delivered with the aid of audiometric headphones. Our results show no significant differences for the amplitude values obtained (p values > 0.05). For the latency there was a statistically significant difference (p-value = 0.001) for the left hand, subsequently not confirmed by the comparison performed between the two sides (p-values = 0.28 and 0.56). If these preliminary data are confirmed by a larger sample, the acoustic stimulus could be introduced in a standardized protocol for performing SSR in pediatric patients.

Electroactive Polymers Obtained by Conventional and Non-Conventional Technologies

Electroactive polymers (EAPs), materials that present size/shape alteration in response to an electrical stimulus, are currently being explored regarding advanced smart devices, namely robotics, valves, soft actuators, artificial muscles, and electromechanical sensors. They are generally prepared through conventional techniques (e.g., solvent casting and free-radical polymerization). However, non-conventional processes such as those included in additive manufacturing (AM) are emerging as a novel approach to tune and enhance the electromechanical properties of EAPs to expand the scope of areas for this class of electro-responsive material. This review aims to summarize the published work (from the last five years) in developing EAPs either by conventional or non-conventional polymer processing approaches. The technology behind each processing technique is discussed as well as the main mechanism behind the electromechanical response. The most common polymer-based materials used in the design of current EAPs are reviewed. Therefore, the main conclusions and future trends regarding EAPs obtained by conventional and non-conventional technologies are also given.

Identification of Brain Electrical Activity Related to Head Yaw Rotations

Automatizing the identification of human brain stimuli during head movements could lead towards a significant step forward for human computer interaction (HCI), with important applications for severely impaired people and for robotics. In this paper, a neural network-based identification technique is presented to recognize, by EEG signals, the participant’s head yaw rotations when they are subjected to visual stimulus. The goal is to identify an input-output function between the brain electrical activity and the head movement triggered by switching on/off a light on the participant’s left/right hand side. This identification process is based on “Levenberg–Marquardt” backpropagation algorithm. The results obtained on ten participants, spanning more than two hours of experiments, show the ability of the proposed approach in identifying the brain electrical stimulus associate with head turning. A first analysis is computed to the EEG signals associated to each experiment for each participant. The accuracy of prediction is demonstrated by a significant correlation between training and test trials of the same file, which, in the best case, reaches value r = 0.98 with MSE = 0.02. In a second analysis, the input output function trained on the EEG signals of one participant is tested on the EEG signals by other participants. In this case, the low correlation coefficient values demonstrated that the classifier performances decreases when it is trained and tested on different subjects.

A Case Study on the Use of Virtual Fencing to Intensively Graze Angus Heifers Using Moving Front and Back-Fences

Virtual fencing contains and controls grazing cattle using sensory cues rather than physical fences. The technology comprises a neckband-mounted device that delivers an audio cue when the animal nears a virtual boundary that has been set via global positioning system, followed by an electrical stimulus if it walks beyond the boundary. Virtual fencing has successfully been used to intensively graze cattle using a simple virtual front-fence, but a more complex intensive grazing system comprising moving virtual front and back-fences has not been assessed. We studied the effectiveness of virtual fencing technology to contain groups of Angus heifers within grazing cells defined by semi-permanent electric side-fences and virtual front and back-fences, compared to groups of heifers contained in cells defined only by electric fencing. Four groups of 10 Angus heifers were randomly allocated to a “control” (grazed with a conventional electric front and back-fence, n = 2 groups) or “virtual fence” treatment (grazed with a virtual front and back-fence, n = 2 groups). The groups of heifers grazed four adjacent experimental paddocks that were established using TechnoGrazing™ infrastructure. An estimated 9.5 kg pasture DM/heifer.day was offered in each of three 3 day allocations (9 day study period). Data collected include cues delivered by the neckbands, time beyond the virtual boundaries, pasture consumption for each allocation and heifer live weight changes over the study period. The virtual front and back-fences successfully contained one group of heifers in their grazing cell, but the second group of heifers spent an increasing amount of time in the exclusion zone during the second and third allocations and consequently received an increasing number of audio and electrical stimuli. There were no effects of electric or virtual-fence treatment on live weight change or pasture utilization. By grazing heifers in adjacent paddocks our experimental design may have produced a motivation for some heifers to cross the virtual boundary to regain close contact with familiar conspecifics. Despite this, valuable learnings were gained from this study. Most notably, virtual fencing should not be used to manage cattle that have close visual contact to other mobs. We conclude that the successful application of virtual fencing technology needs to accommodate the natural behaviors of cattle.

Overgeneralization of fear, but not avoidance, following acute stress

Research has demonstrated the spreading of fear from threat-related stimuli to perceptually similar, but innocuous, stimuli. Less is known, however, about the generalization of avoidance behavior. Given that stress is known to affect learning and memory, we were interested in the effect of acute stress on (over)generalization of fear and avoidance responses. On the first day, one geometrical shape was paired with a mild electrical stimulus (CS+), whereas another shape was not (CS-). One day later, after participants had been exposed to the Maastricht Acute Stress Test or a control task, generalization of avoidance responses and fear (shock expectancy and skin conductance responses) was tested to a range of perceptual generalization stimuli. Generalization gradients were observed across different outcome measures. Stress enhanced generalization of shock expectancy to the stimulus most similar to the CS+. Our findings confirm that stress can affect the generalization of fear, but further studies are warranted.

Electrically programmable adhesive hydrogels for climbing robots

Although there have been notable advances in adhesive materials, the ability to program attaching and detaching behavior in these materials remains a challenge. Here, we report a borate ester polymer hydrogel that can rapidly switch between adhesive and nonadhesive states in response to a mild electrical stimulus (voltages between 3.0 and 4.5 V). This behavior is achieved by controlling the exposure and shielding of the catechol group through water electrolysis–induced reversible cleavage and reformation of the borate ester moiety. By switching the electric field direction, the hydrogel can repeatedly attach to and detach from various surfaces with a response time as low as 1 s. This programmable attaching/detaching strategy provides an alternative approach for robot climbing. The hydrogel is simply pasted onto the moving parts of climbing robots without complicated engineering and morphological designs. Using our hydrogel as feet and wheels, the tethered walking robots and wheeled robots can climb on both vertical and inverted conductive substrates (i.e., moving upside down) such as stainless steel and copper. Our study establishes an effective route for the design of smart polymer adhesives that are applicable in intelligent devices and an electrochemical strategy to regulate the adhesion.

Investigation of Electrical Interference towards Phosphene-Based Walking Support System

A walking support system with phosphenes for blind people has been investigated. Phosphene is a phenomenon where a flash of light is recognized in the brain by giving an electrical stimulus to human’s visual pathway. Phosphenes can be perceived even if their eyes are closed or they are blind. It has been clarified that phosphenes can be induced to several directions if electrodes placements are precisely selected. When phosphenes are presented to two directions for recognizing two obstacles, two pairs of electrodes must be applied. In such a case, however, the electrical interference occurs due to the short distance between electrodes. In the practical use of the phosphene-based walking support system, the avoidance of electrical interference is significant in order to present the phosphenes precisely. Therefore, in this paper, we first practically investigate the electrical interference by considering the difference in phosphene induction generated by a single pair of electrodes and by two pairs of electrodes. Then, the solutions to avoid the electrical interference are discussed.

An FMRI-compatible System for Targeted Electrical Stimulation

BackgroundElectroceutical therapy, applied in various forms, is a rapidly growing therapeutic option to be considered across different medical disorders, particularly within psychiatry, neurology, chronic pain and rehabilitation therapy. Combining targeted electric stimuli with feedback from fMRI can provide valuable information about the mechanisms underlying the therapeutic effects. So far, however, such studies have been hampered by the lack of technology to conduct such experiments in a both accurate and safe manner. We here present a patented system, a fMRI compatible electrical stimulator, developed for fMRI data acquisition during deep brain stimulation (DBS), as well as the first proof-of-concept neuroimaging data in pigs obtained with a prototype of the device.MethodsThe system consists of two modules, placed in the control and scanner room, with corresponding optical modules and signal converters, connected by optical fiber led through wave guides and back looped for quality assurance. The system is also connected to the MRI scanner to timely initiate the stimulation sequence at start of scan. We evaluated the system in four pigs with DBS in the subthalamic nucleus (STN) where we acquired the BOLD response in the STN and neocortex, with stimulation turned on and off in a block design synchronized to the scanning sequence.ResultsWe found that the system delivered a robust electrical stimulus to the implanted electrode during the entire experimental period. The stimulus was confirmed to be in sync with the preprogrammed fMRI block design. All pigs displayed a DBS-STN induced neocortical BOLD response, but none in the site of the implanted electrode. The system solves three major problems related to electrical stimuli and fMRI examinations, namely preventing distortion of the fMRI signal, enabling communication that synchronize the experimental conditions, and surmounting the safety hazards caused by interference from the powerful magnetic field and RF emission. ConclusionsThe patented fMRI compatible electrical stimulator, based on an optic fiber solution, circumvents previous problems related to DBS electroceuticals and fMRI. The system allows flexible modifications for fMRI designs and stimulation parameters but can also be customized to electroceutical applications beyond DBS, applicable for a broad range of medical conditions.