Linear Array Electrode Research Articles

Local field potential responses associated with perceptual filling-in at blind spot in macaque primary visual cortex.

To understand the neural mechanisms of perceptual filling-in at the blind spot (BS), we analyzed neural activity in the region representing the visual field corresponding to the BS (BS region) in the primary visual cortex (V1) of the macaque monkey. We inserted a linear array electrode into the BS region or surrounding region and recorded the multiunit activities (MUAs) and local field potential (LFP). We examined the responses of MUAs and LFP to a large visual stimulus that entirely covered the BS (surface stimuli) while the monkey performed a visual fixation task in either the monocular condition without receiving direct retinal input or the binocular condition receiving retinal information. We observed clear MUA responses in the deep layers within the BS region under monocular conditions, confirming previous reports that V1 neurons in the BS region are activated when perceptual filling-in occurs. Current source density analysis using LFP showed that MUA responses were mainly observed in layer 5. Although LFP responses were generally stronger in the binocular condition than in the monocular condition, a notable exception was observed in the BS region. LFP responses in the low-beta band in the superficial layers were stronger in the monocular condition than in the binocular condition. These results suggest that low-beta activity in the superficial layer is related to the occurrence of perceptual filling-in in the BS. The origin of this activity is considered to be feedback signals from the extrastriate areas to the V1.NEW & NOTEWORTHY Two characteristic activities were induced in the blind spot (BS) region in response to the stimulus, causing perceptual filling-in: 1) beta-band LFP responses in the superficial layers and 2) neuronal responses in the deep layers, mainly in layer 5. These data suggest that the feedback signal from the extrastriate areas to the BS region in V1 is involved in perceptual filling-in.

DS12 Experience of electrochemotherapy in cutaneous tumours and skin metastases within a UK specialist tertiary centre

Abstract Electrochemotherapy (ECT) has gained recognition as an effective treatment that uses electrical pulses to permeabilize cell membranes in tumours, enhancing the cytotoxicity of anticancer agents. The National Institute for Health and Care Excellence suggests use of ECT for the management of primary basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) in selected patients after discussion within a specialist skin cancer multidisciplinary team. It also supports ECT as a palliative treatment for metastases in the skin from tumours of nonskin origin and malignant melanoma (MM). The objective of the study was to evaluate the outcomes and complications of ECT with bleomycin when used for palliative and curative intent. A retrospective cohort study of all patients who underwent ECT in a UK tertiary centre was performed between June 2016 and December 2022. Seventy-one patients (28 men and 43 women) with a total of 89 tumours were included in the study (mean age 69 years; range 29–99). Prior treatments included surgery (n = 9; 13%), immunotherapy (n = 14; 20%), radiotherapy (n = 26; 37%) and chemotherapy (n = 18; 25%). The linear array electrode was used in most cases with median sequence of 47 (range 1–500). Electrochemotherapy was used for palliative intent in 73% (n = 52) and for curative intent in 27% (n = 19). For palliation, ECT was used to treat patients with MM (n = 18/52; 35%), SCC (n = 17/52; 33%) and breast cancer metastases (n = 11/52; 21%), often in patients who had progressed despite conventional management. The most common site treated was the lower limb (n = 16/52; 31%). Twenty-two patients in this group had a good or partial response, with reduction in tumour size, and 52% had improvement in their symptoms (n = 27/52). The crude 1-year survival in this group was 83% (n = 43/52). Complications of ECT when used for palliation included pain, ulceration, tonic–clonic seizure and pneumothorax. In those where ECT was used for curative intent, the majority had ECT for BCCs (n = 12/19; 63%). The most common site treated was the head and neck. Resolution was reported in 58% (n = 11/19) and partial response in 11% (n = 2/19), while two patients underwent excision following recurrence. Complications when used for curative intent included ectropion, indented scarring, nerve palsy, ulceration, pain and webbing. In our opinion, ECT may represent a robust and efficacious treatment option particularly for smaller, lower-risk tumours which may produce improved outcomes. Electrochemotherapy may serve as an alternative to surgical intervention, particularly in patients with multiple comorbidities, and can be used for primary tumour management.

Calcium Electroporation for Keloids: A First-in-Man Phase I Study

Background: Keloid scarring is a pathologic proliferation of scar tissue that often causes pruritus, pain, and disfigurement. Keloids can be difficult to treat and have a high risk of recurrence. Recent studies have shown promising results in the treatment of cutaneous metastases with intralesional calcium combined with electroporation (calcium electroporation). As calcium electroporation has shown limited side effects it has advantages when treating benign keloid lesions, and on this indication we performed a phase I study. Methods: Patients with keloids were treated with at least 1 session of calcium electroporation and followed up for 2 years. Calcium was administered intralesionally (220 mM) followed by the application of eight 100-µs pulses (400 V) using linear-array electrodes and Cliniporator (IGEA, Italy). Treatment efficacy was evaluated clinically (size, shape, erythema), by patient self-assessment (pruritus, pain, other) and assessed histologically. Results: Six patients were included in this small proof of concept study. Treatment was well tolerated, with all patients requesting further treatment. Two out of 6 patients experienced a decrease in keloid thickness over 30%. A mean reduction of 11% was observed in volume size, and a mean flattening of 22% was observed (not statistically significant). Five out of 6 patients reported decreased pain and pruritus. No serious adverse effects or recurrences were observed over a mean follow-up period of 338 days. Conclusion: In this first phase I clinical study on calcium electroporation for keloids, treatment was found to be safe with minor side effects. Overall, patients experienced symptom relief, and in some patients keloid thickness was reduced.

Electrochemotherapy in the treatment of cutaneous malignancy: Outcomes and subgroup analysis from the cumulative results from the pan-European International Network for Sharing Practice in Electrochemotherapy database for 2482 lesions in 987 patients (2008–2019)

BackgroundElectrochemotherapy (ECT) is a treatment for both primary and secondary cutaneous tumours. The international Network for sharing practices on ECT group investigates treatment outcomes after ECT using a common database with defined parameters. MethodsTwenty-eight centres across Europe prospectively uploaded data over an 11-year period. Response rates were investigated in relation to primary diagnosis, tumour size, choice of electrode type, route of bleomycin administration, electrical parameters recorded and previous irradiation in the treated field. ResultsNine hundred eighty-seven patients, with 2482 tumour lesions were included in analysis. The overall response (OR) rate was 85% (complete response [CR]: 70%, partial response rate: 15%, stable disease: 11%, and progressive disease: 2%). For different histologies, OR and CR rates for metastases of malignant melanoma were 82% and 64%, basal cell carcinoma were 96% and 85%, breast cancer metastases were 77% and 62%, squamous cell carcinoma were 80% and 63% as well as Kaposi's sarcoma were 98% and 91%, respectively. Variance was demonstrated across histotypes (p < 0.0001) and in accordance with size of lesion treated (dichotomised at diameter of 3 cm (p < 0.0001). Hexagonal electrodes were generally used for larger tumours, but for tumours up to 3 cm, linear array electrodes provided better tumour control than hexagonal electrodes (80%:74%, p < 0.003). For tumours more than 2 cm, intravenous administration was superior to intratumoural (IT) administration (p < 0.05). Current recorded varied across tumour histologies and size but did not influence response rate. In previously irradiated areas, responses were selectively lower for IT administration. ConclusionsThese cumulative data endorse efficiency of ECT across a broad range of histotypes. Analysis of 2482 lesions details subgroup analysis on treatment response informing future treatment choices.

Multi-Channel Surface Electromyography Electrodes: A Review

This paper is a review of multi-channel surface electromyography (sEMG) electrode used in the research for investigating the properties of muscles. Over 300 papers from five recognized journals were examined from the year 2000 to 2013 with only 64 stating the use of multi-channel electrodes in their research. The review determined that multi-channel electrodes can be classified as linear array or 2D array electrodes. The 2D array is the basis for developing the high-spatial-resolution sEMG (HSR-sEMG) or high density sEMG (HD-sEMG). The important factors considered in this review of the electrodes are: 1) the material used; 2) the inter-electrode distance; and 3) the configuration for the collection of the electromyography signals. The basic configurations of the sEMG electrodes are monopolar, bipolar, and double differential. It was found that the majority of the linear array electrodes were used to collect either bipolar or double differential signals. The 2D array electrodes were used to collect monopolar signals. The HSR-sEMG electrodes used a normal double differentiating filter, referred to as Laplacian configuration. The HD-sEMG has versatility being able to collect all types of signals, such as monopolar, bipolar, double differential, or signals filtered by Laplacian configuration.

Functional columns in superior temporal sulcus areas of the common marmoset.

Cortical areas in the superior temporal sulcus (STS) of primates have been recognized as a part of the 'social brain'. In particular, biological motion stimuli elicit neuronal responses in the STS, indicating their roles in the ability to understand others' actions. However, the spatial organization of functionally identified STS cells is not well understood because it is difficult to identify the precise locations of cells in sulcal regions. Here, using a small New World monkey, the common marmoset (Callithrix jacchus) that has a lissencephalic brain, we investigated the spatial organization of the cells responsive to other's actions in STS. The neural responses to movies showing several types of other's actions were recorded with multicontact linear-array electrodes that had four shanks (0.4 mm spacing), with eight electrode contacts (0.2 mm spacing) for each shank. The four shanks were penetrated perpendicular to the cortical surface. We found that STS cells significantly responded to other's goal-directed actions, such as when an actor marmoset was reaching for and grasping a piece of food. The response profiles to the movies were more similar between the vertically positioned electrodes than horizontally positioned electrodes when the distances between electrodes were matched. This indicates that there are functional columns in the higher-order visual areas in STS of the common marmoset.

Acute Testosterone Deficiency Affects Electrical Properties Of Elbow Flexors And Extensors During Voluntary Contractions

Testosterone (T) is a powerful androgenic anabolic steroid (AAS) capable to induce diverse biological modifications both in the nervous system and in the skeletal muscle. Nevertheless, no previous study investigated the effect of T on the neuromuscular control in intact human muscles. PURPOSE: This study aims at assessing the acute effects of reduced T serum concentration on the neuromuscular control in intact human muscle. METHODS: Off-therapy hypogonadal (HY= 9) and eugonadal (EU = 15) volunteers were asked to perform isokinetic elbow flexion-extension at different angular velocities (AV: 0-30-60-120-180- 240°/s). For any considered AV, three cycles were performed. Between each attempt (AV), 5-minute rest were granted. Surface electromyograms (sEMG) of Biceps Brachii (BB) and Triceps Brachii (TB) were recorded in differential mode with two four linear array electrodes. sEMG and torque data were recorded synchronously at a sampling frequency of 2048 Hz. For any AV, during flexion and extension, the maximal torque among the three cycles was detected and used to compare group means. For both BB and TB and for all the considered AV, agonist (AGBB; AGTB) and antagonist (ANBB; ANTB) activation was expressed as a ratio of the agonist activation observed at 0°/s. Furthermore, the median frequency (MDF) of the sEMG power spectrum was computed for both the BB and the TB (MDFBB; MDFTB) at any AV considered. Muscle fiber conduction velocity of the BB (CVBB) was estimated as well. RM-ANOVA was performed to compare group means in mechanical and electromyographic parameters. RESULTS: No main effect of group was observed for peak torque, during flexion (p = .38) and extension (p = .74) and for AGBB (p = .44), AGTB (p = .93), ANBB (p = .99) and ANTB (p = .96). A significant effect of group was observed for MDFTB (p = .02; group mean ± SD. EU: 97.1 ± 14.0; HY: 83.5 ± 9.4) and a trend (p = .05) towards lower MDFBB in the HY group (group mean ± SD. EU: 88.1±15.0; HY: 77.1±13.9). The HY group showed a trend towards lower CVBB (p = .06; EU: 4.5 ± 0.6; HY: 4.1 ± 0.2) CONCLUSION: Since MDF and CV have been associated with motor unit recruitment strategies, the lower MDF and CVBB observed in the HY group seem to reflect a decreased ability to recruit motoneuron pools, which might lead to the well documented force loss following chronic exposure to a reduced T concentrations.

Multichannel EMG-based estimation of fiber conduction velocity during isometric contraction of patients with different stages of diabetic neuropathy

This study compares muscle fiber conduction velocities estimated using surface electromyography during isometric maximal voluntary contraction in different stages of diabetic neuropathy. Eighty-five adults were studied: 16 non-diabetic individuals and 69 diabetic patients classified into four neuropathy stages, defined by a fuzzy expert system: absent (n=26), mild (n=21), moderate (n=11) and severe (n=11). Average muscle fiber conduction velocities of gastrocnemius medialis, tibialis anterior, vastus lateralis and biceps femoris were assessed using linear array electrodes, and were compared by ANOVA. Conduction velocities were significantly decreased in the moderate neuropathy group for the vastus lateralis compared to other groups (from 18% to 21% decrease), and were also decreased in all diabetic groups for the tibialis anterior (from 15% to 20% from control group). Not only the distal anatomical localization of the muscle affects the conduction velocity, but also the proportion of muscle fiber type, where the tibialis anterior with greater type I fiber proportion is affected earlier while the vastus lateralis with greater type II fiber proportion is affected in later stages of the disease. Generally, the muscles of the lower limb have different responsiveness to the effects of diabetes mellitus and show a reduction in the conduction velocity as neuropathy progresses.

Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays

High-frequency ultrasound is needed for medical imaging with high spatial resolution. A key issue in the development of ultrasound imaging arrays to operate at high frequencies (≥30 MHz) is the need for photolithographic patterning of array electrodes. To achieve this directly on 1-3 piezocomposite, the material requires not only planar, parallel, and smooth surfaces, but also an epoxy composite filler that is resistant to chemicals, heat, and vacuum. This paper reports, first, on the surface finishing of 1-3 piezocomposite materials by lapping and polishing. Excellent surface flatness has been obtained, with an average surface roughness of materials as low as 3 nm and step heights between ceramic/polymer of ∼80 nm. Subsequently, high-frequency array elements were patterned directly on top of these surfaces using a photolithography process. A 30-MHz linear array electrode pattern with 50-μm element pitch has been patterned on the lapped and polished surface of a high-frequency 1-3 piezocomposite. Excellent electrode edge definition and electrical contact to the composite were obtained. The composite has been lapped to a final thickness of ∼55 μm. Good adhesion of electrodes on the piezocomposite has been achieved and electrical impedance measurements have demonstrated their basic functionality. The array was then packaged, and acoustic pulse-echo measurements were performed. These results demonstrate that direct patterning of electrodes by photolithography on 1-3 piezocomposite is feasible for fabrication of high-frequency ultrasound arrays. Furthermore, this method is more conducive to mass production than other reported array fabrication techniques.

Real-time volume imaging using a crossed electrode array

This paper describes a unique crossed electrode array for real-time volume ultrasound imaging. By placing orthogonal linear array electrode patterns on the opposite sides of a hemispherically shaped composite transducer substrate, a 2-D array can be fabricated using a small fraction of the elements required for a traditional 2-D array. The performance of the array is investigated using a computer simulation of the radiation pattern. We show that by using a 288-element crossed electrode pattern it is possible to collect large field of view volume images (60 degrees x 60 degrees sector) at real-time frame rates (>20 volume images/s), with image contrast and resolution comparable to what can be obtained using a conventional 128-element linear phased array.

Using two-dimensional spatial information in decomposition of surface EMG signals

Recently, high-density surface EMG electrode grids and multi-channel amplifiers became available for non-invasive recording of human motor units (MUs). We present a way to decompose surface EMG signals into MU firing patterns, whereby we concentrate on the importance of two-dimensional spatial differences between the MU action potentials (MUAPs). Our method is exemplified with high-density EMG data from the vastus lateralis muscle of a single subject. Bipolar and Laplacian spatial filtering was applied to the monopolar raw signals. From the single recording in this subject six different simultaneously active MUs could be distinguished using the spatial differences between MUAPs in the direction perpendicular to the muscle fiber direction. After spike-triggered averaging, 125-channel two-dimensional MUAP templates were obtained. Template-matching allowed tracking of all MU firings. The impact of spatial information was measured by using subsets of the MUAP templates, either in parallel or perpendicular to the muscle fiber direction. The use of one-dimensional spatial information perpendicular to the muscle fiber direction was superior to the use of a linear array electrode in the longitudinal direction. However, to detect the firing events of the MUs with a high accuracy, as needed for instance for estimation of firing synchrony, two-dimensional information from the complete grid electrode appears essential.

Distribution of innervation zones in the human biceps brachii

Two types of multicontact surface electrodes were used to define the distribution of innervation zones (motor end-plate regions) in human skeletal muscles: a linear array electrode and a two-dimensional grid electrode. These electrodes detected motor unit action potentials (MUAPs) propagating along the muscle fibers during a voluntary contraction and marked the source of the propagation, which was assumed to indicate the position of the innervation zones. The linear array electrode defined the absolute position of the innervation zones in the muscle, but it could not clarify the detailed distribution, within the innervation zones. On the other hand, the grid electrode clarified the detailed configuration of innervation zones under the pickup area of the electrode, but the absolute position of the sources was inaccurate. The records obtained with these two electrodes were combined to draw a detailed map of the innervation zones over the entire surface of the muscle. In seven healthy normal adults, the biceps brachii was studied. The innervation zones were positioned at the middle length of the muscle in a band 30–60 mm wide. The detailed configuration of the innervation zones varied between the subjects.

Technique for detecting MUAP propagation from high-threshold motor units

A technique was developed to identify the propagation pattern of high-threshold motor unit action potentials (MUAPs) in human skeletal muscles. A linear surface array and a selective needle electrode were used simultaneously for detection of myoelectric signals during a constant-force isometric voluntary contraction. The needle signals were decomposed into trains of single MUAPs and were used to trigger-average the surface signals. After averaging 16 channels of surface signals derived with the linear array electrode, we obtained the propagation of single MUAPs along the muscle fibers. The special quadrifilar needle electrode and the algorithm for decomposing the needle signals made it possible to detect high-threshold MUs recruited at ≤57.5% of the maximal voluntary contraction (MVC) during 75% MVC sustained contractions and consequently the propagation pattern of APs from those MUs. The position of the innervation zones within single MUs was estimated from the location of the conduction reversals in the surface myoelectric signals. With this technique, we were able to study the configuration of innervation zones of high-threshold MUs in conjunction with their recruitment threshold.

Fabrication and characterization of glassy carbon linear array electrodes

Fabrication and characterization of glassy carbon linear array electrodes