ScienceBeam provides all you need to establish an electrophysiology lab.                                                                                              

You order the package, we manage the rest, from hardware and software installation to the training. We have a whole solution for following Labs:

Single unit

In vivo and in vitro brain and spinal cord single-unit recording equipments 

 

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From MULTI Devices----------- To ONE electromodule(Old) -------------To ONE eLab(new)       

 

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   electromodule eLab
   3.7 Kg                           115 gr
   366 x 116 x 350 mm 136 x 95 x 35 mm   
   24 volt DC operating voltage 12 volt DC operationg voltage
   eSpike software eProbe software
   Cable connection USB and Wireless connection
   One device with limited application                                       All in one system, one device optimized for many application

light weight, compact, low operating voltage, up to 32 channel, advanced- user friendly software, all together in the eLab device

 

more info  

 

 

eProbe Program for visualization and analysis of Extracellular Action Potentials (spikes).  p4
eSpike within program panel for analysis of Extracellular Action Potentials (spikes).   patentalize8
eSorter within program panel for visualization and classifying of action potential signals collected from single and micro-arrey electrodes                                                p4

 

micromanipulator                                                                                           

manual and digital micromanipoulator 

 

 

 

Spinal cord single unit recording

 
 

Spinal cord Stereotaxy

                

Small Animal Stereotaxic instrument                                                                                                     

eProbe Spinal cord recording and data analysis

 

 

Single unit Recording of Somatosensory Cortex of Rat ( Special equipment)

 


 

Mechanical Stimulator

A device for mechanical stimulation of animal vibrissae with controlled speed and displacement.                       

 

 

 


 

Single-unit recordings

When an action potential propagates through the cell, the electric current flows in and out of the soma and axons at excitable membrane regions. This current creates a measurable, changing voltage potential within (and outside) the cell. single-unit recordings provide the most precise recordings from single neurons. A single unit is defined as a single, firing neuron whose spike potentials are distinctly isolated by a recording microelectrode. Single-unit recordings are widely used in cognitive science, where it permits the analysis of human cognition and cortical mapping. This information can then be applied to brain machine interface (BMI) technologies for brain control of external devices.

 

Types of single-unit recordings

Intracellular single-unit recordings: occur within the neuron and measure the voltage change (with respect to time) across the membrane during action potentials. This outputs as a trace with information on membrane resting potential, postsynaptic potentials and spikes through the soma (or axon).

Extracellular single-unit recordings: When the microelectrode is close to the cell surface, it measures the voltage change (with respect to time) outside the cell, giving only spike information. 

 

Microelectrodes type

Different types of microelectrodes can be used for single-unit recordings; they are typically high-impedance, fine-tipped and conductive. Fine tips allow for easy penetration without extensive damage to the cell, but they also correlate with high impedance. Additionally, electrical and/or ionic conductivity allow for recordings from both non-polarizable and polarizable electrodes. The two primary classes of electrodes are glass micropipettes and metal electrodes. Electrolyte-filled glass micropipettes are mainly used for intracellular single-unit recordings; metal electrodes (commonly made of stainless steel, platinum, tungsten or iridium) and used for both types of recordings.

Both glass and metal are high-impedance electrodes, but glass micropipettes are highly resistive and metal electrodes have frequency-dependent impedance. Glass micropipettes are ideal for resting- and action-potential measurement, while metal electrodes are best used for extracellular spike measurements. Each type has different properties and limitations, which can be beneficial in specific applications.

Glass

Glass micropipettes are filled with an ionic solution to make them conductive; a silver-silver chloride (Ag-AgCl) electrode is dipped into the filling solution as an electrical terminal. Ideally, the ionic solutions should have ions similar to ionic species around the electrode; the concentration inside the electrode and surrounding fluid should be the same. Additionally, the diffusive characteristics of the different ions within the electrode should be similar. The ion must also be able to "provide current carrying capacity adequate for the needs of the experiment". And importantly, it must not cause biological changes in the cell it is recording from. Ag-AgCl electrodes are primarily used with a potassium chloride (KCl) solution. With Ag-AgCl electrodes, ions react with it to produce electrical gradients at the interface, creating a voltage change with respect to time. Electrically, glass microelectrode tips have high resistance and high capacitance. They have a tip size of approximately 0.5-1.5 µm with a resistance of about 10-50 MΩ. The small tips make it easy to penetrate the cell membrane with minimal damage for intracellular recordings. Micropipettes are ideal for measurement of resting membrane potentials and with some adjustments can record action potentials. There are some issues to consider when using glass micropipettes. To offset high resistance in glass micropipettes, a cathode follower must be used as the first-stage amplifier. Additionally, high capacitance develops across the glass and conducting solution which can attenuate high-frequency responses. There is also electrical interference inherent in these electrodes and amplifiers.

Metal

Metal electrodes are made of various types of metals, typically silicon, platinum, and tungsten. They "resemble a leaky electrolytic capacitor, having a very high low-frequency impedance and low high-frequency impedance". They are more suitable for measurement of extracellular action potentials, although glass micropipettes can also be used. Metal electrodes are beneficial in some cases because they have high signal-to-noise due to lower impedance for the frequency range of spike signals. They also have better mechanical stiffness for puncturing through brain tissue. Lastly, they are more easily fabricated into different tip shapes and sizes at large quantities. Platinum electrodes are platinum black plated and insulated with glass. "They normally give stable recordings, a high signal-to-noise ratio, good isolation, and they are quite rugged in the usual tip sizes". The only limitation is that the tips are very fine and fragile. Silicon electrodes are alloy electrodes doped with silicon and an insulating glass cover layer. Silicon technology provides better mechanical stiffness and is a good supporting carrier to allow for multiple recording sites on a single electrode. Tungsten electrodes are very rugged and provide very stable recordings. This allows manufacturing of tungsten electrodes with very small tips to isolate high-frequencies. Tungsten, however, is very noisy at low frequencies. In mammalian nervous system where there are fast signals, noise can be removed with a high-pass filter. Slow signals are lost if filtered so tungsten is not a good choice for recording these signals.

 

Experimental setup

The basic equipment needed to record single units is microelectrodes, amplifiers, micromanipulators and recording devices. The type of microelectrode used will depend on the application. The high resistance of these electrodes creates a problem during signal amplification. If it were connected to a conventional amplifier with low input resistance, there would be a large potential drop across the microelectrode and the amplifier would only measure a small portion of the true potential. To solve this problem, a cathode follower amplifier must be used as an impedance matching device to collect the voltage and feed it to a conventional amplifier. To record from a single neuron, micromanipulators must be used to precisely insert an electrode into the brain. This is especially important for intracellular single-unit recording. Finally, the signals must be exported to a recording device. After amplification, signals are filtered with various techniques. They can be recorded by an oscilloscope and camera, but more modern techniques convert the signal with an analog-to-digital converter and output to a computer to be saved. Data-processing techniques can allow for separation and analysis of single units.

  

 

Field potentials

In vivo and in vitro Field potentials recording equipments

  

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          3.7 Kg 115 gr
          366 x 116 x 350 mm  136 x 95 x 35 mm    
          24 V DC 12 V DC
           eSpike software                                                       eProbe software                                                               
light weight, compact, low operating voltage, up to 32 channel, advanced- user friendly software, all together in the eLab device

 

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eProbe Program for visualization and analysis of local field potentials  p2
eTrace Within program panel for analysis of local field potentials trace

 

 

 

 

   


 

In vitro Field potential recording

Extracellular field potentials are local current sinks or sources that are generated by the collective activity of many cells. Usually, a field potential is generated by the simultaneous activation of many neurons by synaptic transmission.

The mammalian brain slice preparation has become a standard tool in neuroscience for investigating the physiology and pharmacology of neurons, as well as for the analysis of neuronal circuits. This technique, which involves maintaining a slice of brain tissue in physiological saline solution has become the technique of choice for the study of synaptic mechanisms. It can be used to investigate the effect of neurotransmitters and drugs on neurons, various internal and external perturbations on the brain, the characteristics of ion channels and synaptic plasticity. The hippocampus slice is used in laboratoies to study synaptic plasticity mechanisms; long-term potentiating (LTP) and long-term depression (LTD).

 

Hippocampal trisynaptic circuitry 

Within the layers of the hippocampus, the neurons are arranged in three connecting pathways that allow information to flow in from the entorhinal cortex, through the pathways and out to either the subiculum or the fornix. These pathways are:

1. Perforant path: Which consists of axons from cells in the entorhinal cortex (which is adjacent to the hippocampus and receives inputs from neocortical association cortices) and synapseson the granule cells in the dentate gyrus.

2. Mossy fiber pathway: Which consists of axons that arise from the granule cells and project to the pyramidal cells of the CA3 region.

3. Schaffer collateral pathway: Which consists of axons that arise in pyramidal neurons in CA3 and project to CA1 region of the hippocampus. 

 

trisynaps

 

Preparation of hippocampal slices 

A slice of brain tissue can be removed from the intact brain and maintained in a physiological saline (artificial cerebrospinal fluid, ACSF) solution with appropriate temperature and oxygen conditions so that neurons remain healthy and active. The hippocampus slice is a particularly popular preparation because the hippocampus is a layered structure with a well-defined tri-synaptic pathway, where each individual synapse is easily accessible.

The hippocampus slice is most commonly used slice preparation. Attraction of this slices due to its clearly layered-out cytoarchitecture , where cell bodies lie in various clearly visible cell bands, and dendrites make contact with fibers from known origin. A lot is known about the histology, as well as the pharmacology of the different areas of the hippocampus. Even though the hippocampus is the most widely used slice preparation, many others have been established in the last twenty years. It is theoretically possible to out  any sort of slice from any region of the CNS.

to do that, rat is sacrificed by decapitation under deep anesthesia using halothane or sodium pentabarbit one (60 mg/kg). Remove the brain as quick as possible from the skull. Use plastic spatula to cut the cranial nerves and submerge brain in ice-cold (2-5ºC) oxygenated artificial cerebro-spinal fluid (ACSF) for 1 minute before dissecting the hippocampus from the brain. Hippocampus is dissected out and immediately put into ACSF chilled at 4º C. ACSF contained the following concentration of salts: NaCl (118 mM), KCl (2.5mM), NaHCO3:(2 mM), glucose (10 mM), NaH2 PO4 (1.2 mM), MgCl2 (1.25 mM) and CaCl2 (2.5 mM) is used. 400 µm thick transverse hippocampal slices is prepared using a vibratome. Slices are incubated in ACSF at room temperature for at least two hours before starting field potential recordings.

 

Evoked field potentials

Evoked field potentials are recorded post synaptically in response to an evoked stimulus in presynaptic cells. Evoked potentials are usually recorded extracellularly and are therefore made up of the response of many cells, often called a population response. The response is a complex response composed of the postsynaptic potentials (PSPs) evoked in the dendrites and the action potentials recorded from the cell body or axons. The dendritic response is referred to as a population excitatory postsynaptic potential (p-EPSP) and the action potential are called a population spike (p-spike). Both the p–EPSP and the p-spike are recorded simultaneously and are superimposed upon each other. In addition, the directionality of the evoked potentials can be reversed depending on whether the electrode is closer to the dendrites or to the cell bodies.

 

field

 

Field potential recordings procedure

Electrophysiological recordings were carried out at room temperature in a submerged recording chamber. Slices are perfused continuously with oxygenated (95% O2/ 5% CO2) ACSF at the rate of 2 ml/minute. ACSF used for incubation and for subsequent recording were of the same composition as used for slicing as mentioned above. Synaptic responses are evoked by stimulating the commissural/associational fibers in the CA3 stratum radiatum layer using a 2-conductor cluster Platinum-Iridium electrode (tip diameter 25 mm each). The extracellular recording electrodes are made of a glass micropipette filled with 2 M NaCl (tip-resistance of 2-4 MW). In case of the CA1 field potential recordings, Schaffer collateral inputs were stimulated with concentric bipolar Tungsten electrode (Outer Diameter 125 mm) .A single current pulse applied to afferent inputs to either CA1 or CA3 area (Schaffer collateral or commissural associational, respectively) evoked a short latency negative potential in the stratum radiatum. This potential is termed as the "extracellular field excitatory post synaptic potential (fEPSP). The stimulus artifact that appears before the post synaptic potential is reflection of the current stimulus applied to the field and this is followed by the fiber volley, which is an extracellular reflection of the presynaptic action potential generated by the stimulus pulse. The initial slope of the fEPSP (mV/ms) is the most widely used measure of synaptic strength in experiments on synaptic.

 

 

 

   

Electrical kindling

Electrical kindling equipments

 

 

 electromodule  rot ePulseeWave4s

   From OLD electromodule------------------------ To Powerful ePulse+eWave combination

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Kindling

Kindling is a commonly used model for the development of seizures and epilepsy in which the duration and behavioral involvement of induced seizures increases after seizures are induced repeatedly. 

seizure1

The brains of experimental animals are repeatedly stimulated, usually with electricity, to induce the seizures. The seizure that occurs after the first such electrical stimulation lasts a short time and is accompanied by a small amount of behavioral effects compared with seizures that result from repeated stimulations. With further seizures, the accompanying behavior intensifies, for example progressing from freezing in early stimulations to convulsions in later ones. The lengthening of duration and intensification of behavioral accompaniment eventually reaches a plateau after repeated stimulation. Even if animals are left unstimulated for as long as 12 weeks, the effect remains; the response to stimulation remains higher than it had been before.

 

SK protocol

RK protocol

  

 

EEG & ECoG

Electroencephalogrphy (EEG) and electrocorticography (ECoG) equipments

 

 

 

electromodule eWave 32

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   electromodule eWave
   3.7 Kg                           115 gr
   366 x 116 x 350 mm 120 x 28 x 60 mm(16D), 155 x 33 x 95 mm (32D)
   24 volt DC operating voltage 5 volt DC operationg voltage
   eSpike software eProbe software
   Cable connection USB and Wireless connection
   One device with limited application                                       All in one system, one device optimized for many application

light weight, compact, low operating voltage, up to 64 channel, advanced- user friendly software, all together in the eLab device

 

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Electroencephalography  

Electroencephalography (EEG) measures voltage fluctuations resulting from ionic current within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time, as recorded from multiple electrodes placed on the scalp.  The widely used method for electrodes placement is 10-20 system. The EEG (ECoG) differs according to sleep-state, level of arousal and mental activity. EEG (ECoG) voltage signals are relatively small (typically 50 µV peak-to-peak).

 

10-20

 

Electrocorticography 

Electrocorticography (ECoG), or intracranial electroencephalography (iEEG) uses electrodes placed directly on the exposed surface of the brain to record electrical activity from the cerebral cortex. ECoG may be performed either in the operating room during surgery (intraoperative ECoG) or outside of surgery (extraoperative ECoG). Because a craniotomy (a surgical incision into the skull) is required to implant the electrode grid, ECoG is an invasive procedure. 

ECoG signals are composed of synchronized postsynaptic potentials (local field potentials), recorded directly from the exposed surface of the cortex. The potentials occur primarily in cortical pyramidal cells. Electrical signals to reach the scalp electrodes of EEG, must also be conducted through the skull, where potentials rapidly attenuate due to the low conductivity of bone. For this reason, the spatial resolution of ECoG is much higher than EEG. ECoG offers a temporal resolution of approximately 5 ms and a spatial resolution of 1 cm.

 

brain wavez

 

Applications 

EEG is most often used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to diagnose sleep disorders, coma, encephalopathies, and brain death. Despite limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis, especially when millisecond-range temporal resolution (not possible with CT or MRI) is required.

  

Evoked potentials 

Derivatives of the EEG technique include evoked potentials (EP), which involves averaging the EEG activity time-locked to the presentation of a stimulus of some sort (visual, somatosensory, or auditory). Event-related potentials (ERPs) refer to averaged EEG responses that are time-locked to more complex processing of stimuli; this technique is used in cognitive science, cognitive psychology, and psychophysiological research.

  

Montage 

Since an EEG voltage signal represents a difference between the voltages at two electrodes, the display of the EEG for the reading encephalographer may be set up in one of several ways. The representation of the EEG channels is referred to as a montage. 

- Sequential montage: Each channel represents the difference between two adjacent electrodes. For example, the channel "Fp1-F3" represents the difference in voltage between the Fp1 electrode and the F3 electrode. 

- Referential montage: Each channel represents the difference between a certain electrode and a designated reference electrode. There is no standard position for this reference; it is, however, at a different position than the "recording" electrodes. Midline positions are often used because they do not amplify the signal in one hemisphere vs. the other. Another popular reference is "linked ears," which is a physical or mathematical average of electrodes attached to both earlobes and mastoids. 

- Average reference montage: The outputs of all of the amplifiers are summed and averaged, and this averaged signal is used as the common reference for each channel. 

- Laplacian montage: Each channel represents the difference between an electrode and a weighted average of the surrounding electrodes. 

 

 

NCS

  Nerve conduction studies

 

eWave4DS-p1 ewave

eWave Updated

 

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light weight, compact, low operating voltage, up to 32 channel, advanced- user friendly software, all together in the eWave device

 

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Nerve conduction velocity

Nerve conduction velocity is speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factors, including age, sex, and various medical conditions. Studies allow for better diagnoses of various neuropathies, especially demyelinating conditions as these conditions result in reduced or non-existent conduction velocities.

Ultimately, conduction velocities are specific to each individual and depend largely on an axon's diameter and the degree to which that axon is myelinated, but the majority of 'normal' individuals fall within defined ranges. Normal impulses in peripheral nerves of the legs travel at 40–45 m/s, and 50–65 m/s in peripheral nerves of the arms. Largely generalized, normal conduction velocities for any given nerve will be in the range of 50–60 m/s.

The purpose of nerve conduction studies is to determine whether nerve damage is present and how severe that damage may be.

 

Method

Nerve conduction studies are performed as follows:

  • Two electrodes are attached to the subject's skin over the nerve being tested.
  • Electrical impulses are sent through one electrode to stimulate the nerve.
  • The second electrode records the impulse sent through the nerve as a result of stimulation.
  • The time difference between stimulation from the first electrode and pick-up by the downstream electrode is known as the latency. Nerve conduction latencies are typically on the order of milliseconds.
  • The distance between the stimulating and receiving electrodes is divided by the impulse latency, resulting in conduction velocity.

Many times, Needle EMG is also performed on subjects at the same time as other nerve conduction procedures because they aid in detecting whether muscles are functioning properly in response to stimuli sent via their connecting nerves. 

 

 

EMG

 Electromyography (EMG) equipments

 

 

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   electromodule eLab
   3.7 Kg                           115 gr
   366 x 116 x 350 mm 136 x 95 x 35 mm  
   24 volt DC operating voltage 12 volt DC operationg voltage
   eSpike software eProbe software
   Cable connection USB and Wireless connection
   One device with limited application                                       All in one system, one device optimized for many application

light weight, compact, low operating voltage, up to 32 channel, advanced- user friendly software, all together in the eLab device

 

more info  

 

 

 


 

Electromyography  

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. An electromyograph detects the electrical potential generated by muscle cell swhen these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, recruitment order or to analyze the biomechanics of human or animal movement.

  

Skin preparation 

The first step before insertion of the needle electrode is skin preparation. This typically involves simply cleaning the skin with an alcohol pad. The actual placement of the needle electrode can be difficult and depends on a number of factors, such as specific muscle selection and the size of that muscle. Proper needle EMG placement is very important for accurate representation of the muscle of interest, although EMG is more effective on superficial muscles as it is unable to bypass the action potentials of superficial muscles and detect deeper muscles. Also, the more body fat an individual has, the weaker the EMG signal. When placing the EMG sensor, the ideal location is at the belly of the muscle: the longitudinal midline. The belly of the muscle can also be thought of as in-between the motor point (middle) of the muscle and the tendonus insertion point.

 

Types of EMG

Surface EMG assesses muscle function by recording muscle activity from the surface above the muscle on the skin. Surface electrodes are able to provide only a limited assessment of the muscle activity. Surface EMG can be recorded by a pair of electrodes or by a more complex array of multiple electrodes. More than one electrode is needed because EMG recordings display the potential difference (voltage difference) between two separate electrodes. Limitations of this approach are the fact that surface electrode recordings are restricted to superficial muscles, are influenced by the depth of the subcutaneous tissue at the site of the recording which can be highly variable depending of the weight of a patient, and cannot reliably discriminate between the discharges of adjacent muscles.

needle EMG

 

Intramuscular EMG can be performed using a variety of different types of recording electrodes. The simplest approach is a monopolar needle electrode. This can be a fine wire inserted into a muscle with a surface electrode as a reference; or two fine wires inserted into muscle referenced to each other. Most commonly fine wire recordings are for research or kinesiology studies. Diagnostic monopolar EMG electrodes are typically stiff enough to penetrate skin and insulated, with only the tip exposed using a surface electrode for reference. Needles for injecting therapeutic botulinum toxin or phenol are typically monopolar electrodes that use a surface reference, in this case, however, the metal shaft of a hypodermic needle, insulated so that only the tip is exposed, is used both to record signals and to inject. Slightly more complex in design is the concentric needle electrode. These needles have a fine wire, embedded in a layer of insulation that fills the barrel of a hypodermic needle, that has an exposed shaft, and the shaft serves as the reference electrode. The exposed tip of the fine wire serves as the active electrode. As a result of this configuration, signals tend to be smaller when recorded from a concentric electrode than when recorded from a monopolar electrode and they are more resistant to electrical artifacts from tissue and measurements tend to be somewhat more reliable. However, because the shaft is exposed throughout its length, superficial muscle activity can contaminate the recording of deeper muscles. Single fiber EMG needle electrodes are designed to have very tiny recording areas, and allow for the discharges of individual muscle fibers to be discriminated.To perform intramuscular EMG, typically either a monopolar or concentric needle electrode is inserted through the skin into the muscle tissue. The needle is then moved to multiple spots within a relaxed muscle to evaluate both insertional activity and resting activity in the muscle. 

 

Activity measurements

Normal muscles exhibit a brief burst of muscle fiber activation when stimulated by needle movement, but this rarely lasts more than 100ms. The two most common pathologic types of resting activity in muscle are fasciculation and fibrillation potentials. A fasciculation potential is an involuntary activation of a motor unit within the muscle, sometimes visible with the naked eye as a muscle twitch or by surface electrodes. Fibrillations, however, are only detected by needle EMG, and represent the isolated activation of individual muscle fibers, usually as the result of nerve or muscle disease. Often, fibrillations are triggered by needle movement (insertional activity) and persist for several seconds or more after the movement ceases. After assessing resting and insertional activity, the electromyographer assess the activity of muscle during voluntary contraction. The shape, size, and frequency of the resulting electrical signals are judged. Then the electrode is retracted a few millimeters, and again the activity is analyzed. This is repeated, sometimes until data on10–20 motor units have been collected in order to draw conclusions about motor unit function. Each electrode track gives only a very local picture of the activity of the whole muscle. Because skeletal muscles differ in the inner structure, the electrode has to be placed at various locations to obtain an accurate study.

Single fiber electromyography assessed the delay between the contractions of individual muscle fibers within a motor unit and is a sensitive test for dysfunction of the neuromuscular junction caused by drugs, poisons, or diseases such as myasthenia gravis. The technique is complicated and typically only performed by individuals with special advanced training. Surface EMG is used in a number of settings; for example, in the physiotherapy clinic, muscle activation is monitored using surface EMG and patients have an auditory or visual stimulus to help them know when they are activating the muscle (biofeedback). 

EMG

 

Electrical characteristics

The electrical source is the muscle membrane potential of about –90 mV. Measured EMG potentials range between less than 50 μV and up to 20 to 30 mV, depending on the muscle under observation. Typical repetition rate of muscle motor unit firing is about 7–20 Hz, depending on the size of the muscle (eye muscles versus seat (gluteal) muscles), previous axonal damage and other factors. Damage to motor units can be expected at ranges between 450 and 780 mV.

 Applications

There are many applications for the use of EMG. EMG is used clinically for the diagnosis of neurological and neuromuscular problems. It is used diagnostically by gait laboratories and by clinicians trained in the use of biofeedback or ergonomic assessment. EMG is also used in many types of research laboratories, including those involved in biomechanics, motor control, neuromuscular physiology, movement disorders, postural control, and physical therapy.

 

 

 

EKG

Electrocardiography (ECG/EKG) equipments

 

Untitled-1                 ECG

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light weight, compact, low operating voltage, up to 32 channel, advanced- user friendly software, all together in the eWave device

 

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Electrocardiography

Electrocardiography (ECG or EKG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin. These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle's electrophysiologic pattern of depolarizing during each heartbeat.

In a conventional 12-lead ECG, 10 electrodes are placed on the patient's limbs and on the surface of the chest. The overall magnitude of the heart's electrical potential is then measured from 12 different angles ("leads") and is recorded over a period of time (usually 10 seconds). In this way, the overall magnitude and direction of the heart's electrical depolarization is captured at each moment throughout the cardiac cycle. The graph of voltage versus time produced by this noninvasive medical procedure is referred to as an electrocardiogram.

During each heartbeat, a healthy heart has an orderly progression of depolarization that starts with pacemaker cells in the sinoatrial node, spreads out through the atrium, passes through the atrioventricular node down into the bundle of His and into the Purkinje fibers, spreading down and to the left throughout the ventricles. This orderly pattern of depolarization gives rise to the characteristic ECG tracing. To the trained clinician, an ECG conveys a large amount of information about the structure of the heart and the function of its electrical conduction system. Among other things, an ECG can be used to measure the rate and rhythm of heartbeats, the size and position of the heart chambers, the presence of any damage to the heart's muscle cells or conduction system, the effects of cardiac drugs, and the function of implanted pacemakers.

 

Limb leads of EKG Precordial leads in ECG

 

 

Electrodes and leads

On a standard 12-lead EKG there are only 10 electrodes, which are listed in the table below. The limb leads, they are "bipolar" and are the comparison between two electrodes. For the precordial leads, they are "unipolar" and compared to a common lead (commonly the Wilson's central terminal).

 

Electrode name

Electrode placement

RA

On the right arm, avoiding thick muscle.

LA

In the same location where RA was placed, but on the left arm.

RL

On the right leg, lateral calf muscle.

LL

In the same location where RL was placed, but on the left leg.

V1

In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum (breastbone).

V2

In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum.

V3

Between leads V2 and V4.

V4

In the fifth intercostal space (between ribs 5 and 6) in the mid-clavicular line.

V5

Horizontally even with V4, in the left anterior axillary line.

V6

Horizontally even with V4 and V5 in the midaxillary line.

 

Two common electrodes used are a flat paper-thin sticker and a self-adhesive circular pad. Each electrode consists of an electrically conductive electrolyte gel and a silver/silver chloride conductor. The gel typically contains potassium chloride — sometimes silver chloride as well — to permit electron conduction from the skin to the wire and to the electrocardiogram.

The common lead, Wilson's central terminal VW, is produced by averaging the measurements from the electrodes RA, LA, and LL to give an average potential across the body. The measurement of a voltage requires two contacts and so, electrically, the unipolar leads are measured from the common lead (negative) and the unipolar lead (positive).

 

3018302

 

Limb leads

Leads I, II and III are called the limb leads. The electrodes that form these signals are located on the limbs—one on each arm and one on the left leg. The limb leads form the points of what is known as Einthoven's triangle.

  • Lead I is the voltage between the (positive) left arm (LA) electrode and right arm (RA) electrode:

I=LA-RA

  • Lead II is the voltage between the (positive) left leg (LL) electrode and the right arm (RA) electrode:

II=LL-RA

  • Lead III is the voltage between the (positive) left leg (LL) electrode and the left arm (LA) electrode:

III=LL-LA

 

Augmented limb leads

Leads aVR, aVL, and aVF are the augmented limb leads. They are derived from the same three electrodes as leads I, II, and III, but they use Goldberger's central terminal as their negative pole which is a combination of inputs from other two limb electrodes.

  • Lead augmented vector right (aVR)' has the positive electrode on the right arm. The negative pole is a combination of the left arm electrode and the left leg electrode:

aVR = RA - 1/2 (LA+LL) =  3/2 (RA - VW)

  • Lead augmented vector left (aVL) has the positive electrode on the left arm. The negative pole is a combination of the right arm electrode and the left leg electrode:

aVL = LA -  1/2 (RA+LL) =  3/2 (LA - VW)

  • Lead augmented vector foot (aVF) has the positive electrode on the left leg. The negative pole is a combination of the right arm electrode and the left arm electrode:

aVF = LL -  1/2 (RA+LA) =  3/2 (LL - VW)

Together with leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of the hexaxial reference system, which is used to calculate the heart's electrical axis in the frontal plane.

 EKG leads

 

  

ERP

Event-related potential recording equipments

  

VEP ERP2

  eWave optimized for ERP recording, up to 64 channel, powerful with eProbe software

 

Design expriment, record, visualize, analysis all together with eProbe the most simple and user-friendly software

 

 

eWave 16/32/64 for ERP and EXG recording, wireless, light, powerful

 eWave 32

 eProbe software, the more you learn about it, the more powerful it will be

 ERPP

 

 

 

 


 

Event-related potential

An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, motor event or in other word, any stereotyped electrophysiological response to a stimulus. The study of the brain in this way provides a noninvasive means of evaluating brain functioning in patients with cognitive diseases. ERPs are measured by means of electroencephalography.

 

cognitive responses.png

 

ERP components

ERP waveforms consist of a series of positive and negative voltage deflections, which are related to a set of underlying components. Though some ERP components are referred to with acronyms (e.g., contingent negative variation – CNV, error-related negativity – ERN, early left anterior negativity – ELAN, closure positive shift – CPS), most components are referred to by a letter (N/P) indicating polarity (negative/positive), followed by a number indicating either the latency in milliseconds or the component's ordinal position in the waveform. For instance, a negative-going peak that is the first substantial peak in the waveform and often occurs about 100 milliseconds after a stimulus is presented is often called the N100 (indicating its latency is 100 ms after the stimulus and that it is negative) or N1 (indicating that it is the first peak and is negative); it is often followed by a positive peak, usually called the P200 or P2. The stated latencies for ERP components are often quite variable. For example, the P300 component may exhibit a peak anywhere between 250ms – 700ms.

 

ERPz

 

ComponentsofERP.svg

 Clinical ERP

Physicians and neurologists will sometimes use a flashing visual checkerboard stimulus to test for any damage or trauma in the visual system. In a healthy person, this stimulus will elicit a strong response over the primary visual cortex located in the occipital lobe, in the back of the brain.

ERP component abnormalities in clinical research have been shown in neurological conditions such as:

·       dementia

·       Parkinson's disease

·       multiple sclerosis

·       head injuries

·       stroke

·       obsessive-compulsive disorder

 

Research ERP

ERPs are used extensively in neuroscience, cognitive psychology, cognitive science, and psycho-physiological research. Experimental psychologists and neuroscientists have discovered many different stimuli that elicit reliable ERPs from participants. The timing of these responses is thought to provide a measure of the timing of the brain's communication or timing of information processing. For example, in the checkerboard paradigm described above, healthy participants' first response of the visual cortex is around 50-70 ms. This would seem to indicate that this is the amount of time it takes for the transduced visual stimulus to reach the cortex after light first enters the eye. Alternatively, the P300 response occurs at around 300ms in the oddball paradigm, for example, regardless of the type of stimulus presented: visual, tactile, auditory, olfactory, gustatory, etc. Because of this general invariance with regard to stimulus type, the P300 component is understood to reflect a higher cognitive response to unexpected and/or cognitively salient stimuli.

Due to the consistency of the P300 response to novel stimuli, a brain-computer interface can be constructed which relies on it. By arranging many signals in a grid, randomly flashing the rows of the grid as in the previous paradigm, and observing the P300 responses of a subject staring at the grid, the subject may communicate which stimulus he is looking at, and thus slowly "type" words. Other ERPs used frequently in research, especially neurolinguistics research, include the ELAN, the N400, and the P600/SPS.

 

 

 

BCI & BMI

Brain-machine interface equipments 

 

 bci

eWave optimized for Brain Computer/Machine Interface approaches

eWave8 , light, wireless and powerful device for BCI/ BMI applications

 

 

 

 

powered by eProbe software

eWave 8D

BMI


 

Brain computer/ machine interface

A brain–computer interface (BCI), sometimes called a mind-machine interface (MMI), direct neural interface (DNI), or brain–machine interface (BMI), is a direct communication pathway between an enhanced or wired brain and an external device. BMI uses brain activity to command, control, actuate and communicate with the world directly through brain integration with peripheral devices and systems. BCIs are often directed at researching, mapping, assisting, augmenting, or repairing human cognitive or sensory-motor functions. 

The field of BCI research and development has since focused primarily on neuroprosthetics applications that aim at restoring damaged hearing, sight and movement. Thanks to the remarkable cortical plasticity of the brain, signals from implanted prostheses can, after adaptation, be handled by the brain like natural sensor or effector channels. Main principle behind this interface is the bioelectrical activity of nerves and muscles (mainly by EEG).

  

Component of BMI

  • IMPLANT DEVICE: The EEG is recorded with electrodes placed on the scalp. Electrodes are small plates, which conduct electricity.

 

  • SIGNAL PROCESSING SECTION
    • Multichannel Acquisition Systems: amplification, initial filtering of EEG signal and possible artifact removal
    • Spike Detection: allow the BMI to transmit only the action potential waveforms and their respective arrival times instead of the sparse, raw signal in its entirety.
    • Signal Analysis: certain features are extracted from the preprocessed and digitized EEG signal which are input to the classifier. Classifier recognize different mental tasks ( pattern recognition)

 

  • EXTERNAL DEVICE: The classifier’s output is the input for the device control. The device control simply transforms the classification to a particular action.

                                      Examples are robotic arm.

 

  • FEEDBACK SECTION: Feedback is needed for learning and for control. Real-time feedback can dramatically improve the performance of a brain–machine interface.

                 -  In BMI based on the operant conditioning, feedback training is essential for the user to acquire the control of own EEG response. 

                 -  In BMI based on the pattern recognition and mental tasks do not definitely require feedback training.

pattern extraction

A

Applications

1. Auditory and visual prosthesis

2. Functional-neuromuscular stimulation (FNS)

3. Prosthetic limb control

 

  • CHALLENGES

               Permanent damage to brain.

              Virus attack on brain

              Thought control and prediction of future thoughts.

              Deletion or recording of memories.

 

  • LIMITATIONS

           The brain is incredibly complex.

          The signals are weak and interference can happen. 

          There are chemical processes involved as well, which electrodes can’t pick up. 

 

simultaneous LFP, EEG & spike

Simultaneously LFP, EEG and spike recording equipments

 

Electromodule(OLD) and eLab(NEW) are General purpose data acquisition systems for recording Action potential (Spikes), Field Potential, EEG signals, and signal modulation by external digital events.
eLab is combination of at least twenty-five different devices in one package. Microelectrode amplifier is a Part of the eLab.
Design of Microelectrode amplifier is optimized for low noise, high dynamic range, and low power dissipation. The novel aspect of the amplifier is its ability to record EEG, LFP and single-unit signals simultaneously from stream of one electrode by one channel Analog to Digital Converter with 24 bit resolution. Another novel aspect is noise-resistant properties of designed circuits which in the following image, you can observe by changing of filter and gain in our designed software "eProbe", researcher had been able to record LFP and EEG signal simultaneously by only one electrode.
 

 

،his software have several oscilloscope .Each scope can be optimized for defferent type of recording by adjusting  Gain ,High-pass filter, Low-pass filter, Horizontal and vertical scale,Inverter. 
in the bottom table,we see the characteristic of  EEG,LFP and single unit(spike) recording

 
 

 

Single unit

LFP

EEG

High Pass filter

300 Hz

1 Hz

1Hz

Low Pass filter

10000 Hz

3000 Hz

100Hz

Gain

10000

1000-2000

100

 

 

 

 

 

 

 

 

 

Microelectrode amplifier (U3022)


Type: Differential, Isolated, Extracellular

Number of channels: Optional, 2, 4, 8

High pass filter setting: 0.1, 1, 10, 100 and 300Hz

Low pass filter setting: 1000, 3000, and 5000Hz

Notch filter setting: 50/60Hz

Gain: 10, 100, 200, 500, 1000 and 10000

Input voltage range: ±5V

Maximum analog input voltage: ±5V

Input impedance: 1012Ω, common mode and differential

Input leakage current: 60pA (typical)

Input capacitance: 8pF

Common mode rejection ratio: 75dB @ 50/60Hz

Isolation type: Optical

Isolation voltage: 2500V

Isolation resistance: 1012

Digitizer

Coupling: DC

Analog input range: ±2.5V

ADC resolution: 24bits

Linearity error: ±7.6ppm (maximum)

Maximum sampling rates: 50 kHz, each channel