A Comprehensive View of Electrosleep: The History, Finite Element Models and Future Directions

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. This is concluded with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES. Despite this history, questions regarding the efficacy of ES remain including optimal dose (electrode placement and waveform). An investigation into brain electric field and current density produced by various montages that are historically relevant to ES was done to evaluate how these montages effect the brain. MRI-derived head models that were segmented using an automated segmentation algorithm and manual corrections were solved for four different electrode montages. The montages that were used are as follows: Sponge electrode on left and right eyes (active), Sponge electrodes over left and right mastoids (return); Sponge electrodes above left and right eyes (active), Sponge electrodes over left and right mastoids (return); High-Definition (HD) electrodes on AF3 and AF4 (active), 5x7 cm sponge on neck (return); HD electrodes on AF3 and AF4 (active), 5x7 sponge electrode on Iz (return). A high concentration of electric field was found on the optic nerve, with levels lowered as the electrodes moved further away from the eyes. There was also a moderate current density on the amygdala, a center involved with anxiety, as well as high electric fields on the brain stem which are centers for sleep. Using the models that were run for the electrosleep inspired montages the montage that was selected for the proposed experiment was to use anodes on AF3 and AF4 with the cathode on Iz. The anodes will be HD electrodes while the cathode will be a 5x7 cm sponge. Subjects will be split into 4 groups of 8 people each and will receive two legs of stimulation spaced one week apart. One leg will have current of 2 mA, 1 mA, 0.5 mA or sham while the other leg is all sham and the order in which they receive it will be randomized. Subjects will be stimulated for 20 minutes at 100 Hz and will spend a total of 40 minutes during the experiment where they will have their eyes recorded with an IR sensitive camera and they will be required to perform an odd-tone response task. Subjects are expected to fall asleep faster with higher levels of current and there is no added effect from baseline expected for subjects who receive sham stimulatio

Reduced discomfort during high-definition transcutaneous stimulation using 6% benzocaine

Background: High-Definition transcranial Direct Current Stimulation (HD-tDCS) allows for non-invasive neuromodulation using an array of compact (approximately 1 cm2 contact area) “High-Definition” (HD) electrodes, as compared to conventional tDCS (which uses two large pads that are approximately 35 cm2). In a previous transcutaneous study, we developed and validated designs for HD electrodes that reduce discomfort over \u3e20 min session with 2 mA electrode current. Objective: The purpose of this study was to investigate the use of a chemical pretreatment with 6% benzocaine (topical numbing agent) to further reduce subjective discomfort during transcutaneous stimulation and to allow for better sham controlled studies. Methods: Pre-treatment with 6% benzocaine was compared with control (no pretreatment) for 22 min 2 mA of stimulation, with either CCNY-4 or Lectron II electroconductive gel, for both cathodal and anodal transcutaneous (forearm) stimulation (eight different combinations). Results: Results show that for all conditions and polarities tested, stimulation with HD electrodes is safe and well tolerated and that pretreatment further reduced subjective discomfort. Conclusion: Pretreatment with a mild analgesic reduces discomfort during HD-tDCS

Clinical effectiveness and cost minimisation model of Alpha-Stim cranial electrotherapy stimulation in treatment seeking patients with moderate to severe generalised anxiety disorder

Background: Cranial electrotherapy stimulation (CES) is a well-tolerated neuromodulation treatment with demonstrated trial efficacy in anxiety disorders. The aim of the current study was to demonstrate its clinical and cost effectiveness during and after CES in people with generalised anxiety disorder (GAD) who had not responded to low intensity psychological treatment in a routine health service. Methods: Consecutive sample of eligible patients with GAD waiting for individual cognitive behaviour therapy (CBT) selected from two publicly funded services in England. They received 60 minutes per day Alpha-Stim CES for 6-12 weeks. Primary outcome was remission on the GAD-7 scale at 12 and 24 weeks. Cost effectiveness was examined using a cost minimisation model of direct health costs. Results: Of 161 patients recruited, 72 (44.7%) and 77 (47.8%) achieved remission on the GAD-7 at 12 and 24 weeks respectively with 122 (75.8%) receiving at least 6 weeks CES. Mean (sd) GAD-7 score at baseline significantly improved from 15.77 (3.21) to 8.92 (5.42) and 8.99 (6.18) at 12 and 24 weeks respectively (p<0.001). 80 (49.7%) participants required further individual CBT. CES provided a saving of £540.88 per patient (95% CI -£327.12, £648.69).  Limitations: Participants were not randomised and there was no control group. Only 48 (29.9%) participants completed every assessment. Conclusion: In patients with generalised anxiety disorder not responding to low intensity psychological treatment, 6-12 weeks daily Alpha Stim CES may be effective after treatment and 3 months later, thereby reducing the need for individual CBT and saving health costs

The effect of precrash velocity reduction on occupant response using a human body finite element model

<p><b>Objective</b>: The objective of this study is to use a validated finite element model of the human body and a certified model of an anthropomorphic test dummy (ATD) to evaluate the effect of simulated precrash braking on driver kinematics, restraint loads, body loads, and computed injury criteria in 4 commonly injured body regions.</p> <p><b>Methods</b>: The Global Human Body Models Consortium (GHBMC) 50th percentile male occupant (M50-O) and the Humanetics Hybrid III 50th percentile models were gravity settled in the driver position of a generic interior equipped with an advanced 3-point belt and driver airbag. Fifteen simulations per model (30 total) were conducted, including 4 scenarios at 3 severity levels: median, severe, and the U.S. New Car Assessment Program (U.S.-NCAP) and 3 extra per model with high-intensity braking. The 4 scenarios were no precollision system (no PCS), forward collision warning (FCW), FCW with prebraking assist (FCW+PBA), and FCW and PBA with autonomous precrash braking (FCW + PBA + PB). The baseline ΔV was 17, 34, and 56.4 kph for median, severe, and U.S.-NCAP scenarios, respectively, and were based on crash reconstructions from NASS/CDS. Pulses were then developed based on the assumed precrash systems equipped. Restraint properties and the generic pulse used were based on literature.</p> <p><b>Results</b>: In median crash severity cases, little to no risk (<10% risk for Abbreviated injury Scale [AIS] 3+) was found for all injury measures for both models. In the severe set of cases, little to no risk for AIS 3+ injury was also found for all injury measures. In NCAP cases, highest risk was typically found with No PCS and lowest with FCW + PBA + PB. In the higher intensity braking cases (1.0–1.4 g), head injury criterion (HIC), brain injury criterion (BrIC), and chest deflection injury measures increased with increased braking intensity. All other measures for these cases tended to decrease. The ATD also predicted and trended similar to the human body models predictions for both the median, severe, and NCAP cases. Forward excursion for both models decreased across median, severe, and NCAP cases and diverged from each other in cases above 1.0 g of braking intensity.</p> <p><b>Conclusions</b>: The addition of precrash systems simulated through reduced precrash speeds caused reductions in some injury criteria, whereas others (chest deflection, HIC, and BrIC) increased due to a modified occupant position. The human model and ATD models trended similarly in nearly all cases with greater risk indicated in the human model. These results suggest the need for integrated safety systems that have restraints that optimize the occupant's position during precrash braking and prior to impact.</p

Failed rib region prediction in a human body model during crash events with precrash braking

<p><b>Objective</b>: The objective of this study is 2-fold. We used a validated human body finite element model to study the predicted chest injury (focusing on rib fracture as a function of element strain) based on varying levels of simulated precrash braking. Furthermore, we compare deterministic and probabilistic methods of rib injury prediction in the computational model.</p> <p><b>Methods</b>: The Global Human Body Models Consortium (GHBMC) M50-O model was gravity settled in the driver position of a generic interior equipped with an advanced 3-point belt and airbag. Twelve cases were investigated with permutations for failure, precrash braking system, and crash severity. The severities used were median (17 kph), severe (34 kph), and New Car Assessment Program (NCAP; 56.4 kph). Cases with failure enabled removed rib cortical bone elements once 1.8% effective plastic strain was exceeded. Alternatively, a probabilistic framework found in the literature was used to predict rib failure. Both the probabilistic and deterministic methods take into consideration location (anterior, lateral, and posterior). The deterministic method is based on a rubric that defines failed rib regions dependent on a threshold for contiguous failed elements. The probabilistic method depends on age-based strain and failure functions.</p> <p><b>Results</b>: Kinematics between both methods were similar (peak max deviation: Δ<i>X</i>_head = 17 mm; Δ<i>Z</i>_head = 4 mm; Δ<i>X</i>_thorax = 5 mm; Δ<i>Z</i>_thorax = 1 mm). Seat belt forces at the time of probabilistic failed region initiation were lower than those at deterministic failed region initiation. The probabilistic method for rib fracture predicted more failed regions in the rib (an analog for fracture) than the deterministic method in all but 1 case where they were equal. The failed region patterns between models are similar; however, there are differences that arise due to stress reduced from element elimination that cause probabilistic failed regions to continue to rise after no deterministic failed region would be predicted.</p> <p><b>Conclusions</b>: Both the probabilistic and deterministic methods indicate similar trends with regards to the effect of precrash braking; however, there are tradeoffs. The deterministic failed region method is more spatially sensitive to failure and is more sensitive to belt loads. The probabilistic failed region method allows for increased capability in postprocessing with respect to age. The probabilistic failed region method predicted more failed regions than the deterministic failed region method due to force distribution differences.</p