Jocelyn, Author at BIOPAC Blog

Fundamentals for Recording Great Heart Rate Data: Subject Preparation

Electrocardiography (ECG) or EKG is one of the most commonly recorded signals as it can be used for a wide variety of heart related analysis. Acquiring good, clean data from subjects can prove difficult though. Everything from electrode options to hardware settings can influence ECG signal quality over research. The following guidelines provide a baseline for ECG recording setups to ensure accurate and quality data from participants.

The most common question when recording ECG data is where to place electrodes on the subject. Certain aspects of your research will help inform exactly where to place electrodes. The most important question to answer is what tasks are your participants performing.

For most studies, the ECG placement can be placed by following Einthoven’s Triangle. This incorporates 3 leads; one running along the top of the chest, one running from right should toward left leg, and one running from left shoulder toward right leg. Place electrodes on the clavicle, wrists, or ankles. Note that if participants are moving around, placing on the wrists and ankles can prove difficult so place them instead on the chest area.

Always make sure to prepare your subject before placing electrodes on them. Abrade the skin before placement especially if placing on the wrists or ankles. Double check that the electrode is fresh and apply gel to the electrode for optimal adhesion. About 5-10 minutes after placement, use an impedance checker to check the electrode signal quality. These simple steps can make the difference between clean and noisy data.

If participants have been prepared correctly and the hardware is dialed in, the ECG waveform should resemble the classic ECG example. There are three primary elements to the electrical signal coming from the heart: P-wave, R-wave, and T-wave. Most lead configurations will resemble this waveform example.

These simple, but key guidelines will help ensure that ECG signals recorded from subjects are clean and high quality. Attach electrodes at the right parts of the body given the tasks that the participants will perform. Always make sure electrode sites are clean and that the electrodes are fresh. For more information and further instructions on recording ECG, visit the BIOPAC ECG applications page, ECG video tutorials, or view our ECG webinars.

BIOPAC offers a variety of wired and wireless equipment that can be used in ECG studies. To find more information on solutions for recording and analyzing signals such as ECG, heart rate, and respiration using the MP160 and other platforms, you can visit the individual application pages on the BIOPAC website.

Choosing the right electrode type

Whether it’s for EEG, ECG, or ECT, electrodes have a myriad of electrophysiological techniques in the field of biomedical research. As far as electrode positioning and selection, decisions about which type to use are best made via literature and discussions with colleagues. Here are some general considerations to observe when determining preferences; most electrodes used for biopotential recording are Ag/Ag-Cl.

Electrode property preference such as gel type must also be taken into account when conducting tests. Electrodes are generally grouped between disposable and reusable types. Typically, either solid or wet gels are used to complement electrodes in gathering test data. Solid gels are easier on the skin than wet gels due to superior water content in wet gels that react aggressively on the skin. The choice between electrodes should then be determined based off of testing criteria and duration. For instance, if there are two electrodes with 4% salt, one wet gel and one solid gel, the wet gel would be more reactive. Reusable and disposable EDA/GSR electrodes both use isotonic gel, however they do not yield different results and will be almost identical during use with the exception of a few feature based discrepancies. The researcher should compare one electrode setup to the other during a measurement with a single EDA/GSR series amplifier.

When the electrodes are functional, chemical reactions at the face of the electrodes occur to permit electrical currents to flow between the subject and equipment. These reactions force the electrode surface to gradually degrade. With appropriate cleaning and storage, reusable electrodes may well last several years, however, the electrode surface deteriorates. Disposable electrodes efficiently eliminate this source of variance as each subject uses electrodes with unsullied surfaces. Inevitably, researchers will cycle through more disposable models over time and duration of use.

Silver-silver chloride (Ag-AgCl) electrodes provide accurate and clear transmission of surface biopotentials and are useful for recording all surface biopotentials on animals and human EEG. BIOPAC offers reusable Ag/AgCl electrodes for recording biopotentials with surface, snap, or post connection. BIOPAC EL250 series and EL650 series reusable electrodes incorporate a variety of features for high-stability recordings: non-polarizable, sintered to increase electrode/electrolyte contact area, reusable via resurfacing, and high stability recordings.

Post electrodes can be used for improved contact through fur or hair. BIOPAC’s EL120 posts have 12 posts in a 10 mm contact area; the posts are 2 mm deep to push through the fur/hair to provide good contact with the skin surface.

BIOPAC’s wide range of reusable electrodes and disposable electrodes provides researchers the chance to best achieve research objectives while maintaining subject comfort and budget requirments. Serving disciplines from Human, Animal, and MRI physiology to Biomedical Engineering, proper electrode selection can lead to a greater success rate at reaching targeted lab/test results.

Determining Physiological Cycles for Data Analysis and Extraction

From breathing to sleep, the human body functions through cycles. Researchers attain the most accurate physiological data when analyzing subjects through cyclic data. Wandering baselines, non-AC coupled, and varying peak amplitudes are some of the many challenges that get in the way of cyclic data analysis. Researchers can overcome these problems with careful goal planning combined with physiology analysis software.

The first step for researchers to take is to define their goals, as a clear strategy is necessary to assess accurate data. One example of a goal could be to extract the average heart rate for each thirty-second interval from BP data. The researcher would first split the problem into multiple steps and classify data between systolic and diastolic locations. Classification would differentiate the primary and intra-cycle locations of interest and the researcher would want the systolic and diastolic peaks for moving averages.

With the Find Cycle Peak Detector, researchers can do this automatically. The AcqKnowledge Find Cycle Peak Detector extracts heart rate and triggers a traceable spike train. With AcqKnowledge, researchers can separate bpm data rates to determine the diastolic and systolic patterns. Individual means, taken by AcqKnowledge, reveal various physiological cycles, including the data rates mentioned above.

The Find Cycle Peak Detector opens the door for researchers to advance their studies in a comprehensive range of fields. Although physiological signals take longer to identify and analyze, the ability to differentiate data sets helps to determine the derivatives and construct signals appropriate for the analysis of the bodily cycle of interest. Physiology technology, such as the Find Cycle Peak Detector, improves the cyclic research procedures because information processes fast and effectively.

BIOPAC’s AcqKnowledge software analyzes data cycles by rates, periodicities, and precise data analysis such as ECG or NICO. Researchers can expedite lab workflow with BIOPAC’s basic scripting to expeditiously detect complex multi-step physiological cycles. The built-in domain-specific analysis and general-purpose tools, such as epoch analysis and stimulation-response analysis, provide researchers with the data they need almost instantly. Scientists can also synchronize various data sets at once with AcqKnowledge software.

AcqKnowledge software is an extremely powerful tool, capable of automatically analyzing data for a variety of applications. To find learn more about AcqKnowledge Find Cycle Detector or view useful analysis tips and tricks, visit the BIOPAC webinar page.

Electrode Placement and Preparation for Mobile Subject Recording

Recording the clearest possible signal can prove tricky, especially from exercising or mobile subjects. We have compiled a helpful guide on electrode placement and preparation that ensures accurate and precise data from mobile subject recording.

When recording mobile subjects, it’s important to take note of the length of lead wires and choose the shortest available option. Longer lead wires have the potential for more motion which could result in moving the electrode on the skin. If there is slack on the wire use tape and wrap to secure the wire closer to the subject’s body.

With multiple options for electrodes it’s important to consider the type of electrode would best facilitate the research. Electrodes can be designed to cover awkward shaped regions of the body or experiments extending beyond 24 hours, but for mobile subjects it’s recommended to use high stress electrodes which utilize a stronger adhesive.

Placement of the electrode is crucial. With ECG acquisition its best to put electrodes across the chest, but placement can vary depending on the research. It’s recommended to place the electrode where there’s the least amount of possible obstructive artifacts; for example, the electrode may need to be adjusted higher on the chest if subjects are using their stomach muscles. When collecting ECG placing an electrode above the bone is better than over a muscle.

The overall setup of the electrodes is very important. Using fresh gel and electrodes as well as taking time to abrade the surface of the skin allows for clearer signal acquisition. Electrodes should sit on the participant’s skin 10-15 minutes and it’s recommended to use an impedance level checker to diagnose the signal before recording.

BIOPAC’s MP160 research system with BioNomadix wireless amplifiers and logger provide the best options for data acquisition of mobile subjects. The transmitter-receiver pair and logger allow for wireless connection between the subject and MP device. BioNomadix is applicable to a wide range of physiological signals including: ECG, EEG, EMG, EOG, EGG, EDA, pulse, respiration, temperature, acceleration, goniometer, heel-toe strike, and clench force.

BIOPAC offers a variety of equipment that can be used in mobile recording studies. To find more information on solutions for recording and analyzing signals such as skin conductance, ECG, heart rate, respiration, and EMG using the MP160, and other platforms, you can visit the individual application pages on the BIOPAC website.

Fundamentals of EEG Recording

In 1929, a German physician named Hans Berger discovered that electrodes placed on the scalp could detect various patterns of electrical activity. After verifying that the recordings were indeed recording from the brain, and were not artifacts of muscle or scalp, scientists began to study these “brain waves.” Today, EEG is still a medically useful recording for brain function. In medical and basic research, the correlation of particular brain waves with sleep phases, emotional states, psychological profiles, and types of mental activities is ongoing.

EEG records the electrical activity of the brain. Surface EEG electrodes provide a noninvasive way to measure brain function and regional brain activity. The EEG signal is made up of different frequency components and the amplitude of the signal varies in the different frequency bands: alpha, beta, delta, theta, gamma.

Rhythm	Typical Frequencies (Hz)
alpha beta delta theta gamma	8-13 13-30 1-5 4-8 >32

EEG can be recorded by placing electrodes on the scalp of the subject. The placement of the electrodes is important to ensure that you are recording data from the correct location when comparing and reporting results.The electrodes are placed on specific locations on the head. Each electrode location is given an alphanumeric name. Alpha is related to actual zone for electrode placement: F-Frontal, C-Central, T-Temporal, P-Parietal, O-Occipital zones. Numeric is based on the two hemispheres, odd numbers representing left side and even numbers representing right side.

These locations are over certain areas of the brain that allow us to identify different types of activity:

F7 near centers for rational activities
Fz near intentional and motivational centers
F8 close to sources of emotional impulses
C3,C4,Cz deal with sensory and motor functions
T3 and T4 emotional process
T5 and T6 certain memory functions
O1 and O2 for primary visual areas

An EEG cap can also be used to ensure proper electrode placement. The size of the EEG cap is critical in EEG recording. Having the correct cap size means that you can ensure that you are recording the correct brain location, otherwise you may think you’re recording F5 when you’re really recording F9.

Recording EEG is a bipolar recording (looking at difference between two electrodes). Electrodes are typically referenced to a physical electrode or site –

vertex (Cz)
linked-ears
linked-mastoids
ipsilateral-ear
contralateral-ear
C7 reference
bipolar references

Recording can also be done using reference-free techniques when using 20 or more channels. The system will usually automatically take an average of all the electrodes rather than a physical location. The different averages include:

Weighted average reference
Common average reference

Once you have your EEG data, utilize AcqKnowledge software to run a number of fully automated EEG analysis functions. A range of fully automated routines provide quick, easy and reproducible results and include approximate entropy, delta power analysis, derive alpha RMS, derive EEG frequency bands, and EEG frequency analysis. The EEG frequency analysis provides a fully automated, epoch driven, analysis of the EEG signal. The system uses power spectral density to report Mean Power, Median Frequency, Mean Frequency, Spectral Edge, Peak Frequency values for each epoch.

For more information on BIOPAC’s wide range of tools for recording, displaying, and analyzing EEG measurements from human and animal subjects, visit BIOPAC’s electroencephalography pages and view BIOPAC’s full line of electrodes, amplifiers, and wearable, wireless transmitters and loggers.

BIOPAC Systems, Inc. provides life science researchers and educators with data acquisition and analysis systems that inspire people and enable greater discovery about life. Visit us at www.biopac.com.

Are Virtual Reality Exercising Games Effective?

In an age of increased obesity and obsession with exercise, software companies have created exercise video games that engage users both mentally and physically. Mixed reviews about the effectiveness of such exergames stem from several components: the perceived task demands during a game, the reward given by the game, and the user’s Exercise Self-Efficacy (ESE, individuals’ confidence in performing exercise tasks). Cornick & Blascovich (2017) explore these components in their study to find exercise and physiological reactions and, in turn, effective motivations in exergames.

The experiment included 89 female undergraduate students who were first evaluated based on the ESE scale. Next, they were randomly assigned to either a high task demand condition in which their avatar weight remained constant, or a low task demand condition in which their avatar lost weight. Participants exercised on a stationary bike while absorbed in a virtual environment. Both groups were informed that their avatar would lose weight if they biked fast enough, when in reality, only half of their avatars could.

Participants’ physiological responses including heart rate, stroke volume, cardiac output, pre-ejection period, and blood pressure were all measured concurrently, continuously, and noninvasively with a BIOPAC MP System while biking. Cardiac performance was measured with an Impedance Cardiograph (ICG) and NIBP100D. AcqKnowledge software was used to distinguish participant challenge and threat states. One week following the study, participants reported how much they exercised in the last week.

The surprising results revealed that participants with high ESE had a high threat response and performed a modest amount of cardiac work, regardless of task demands. Participants with low ESE were extremely influenced by exergame task demands. When presented with a slimming avatar, they had the highest levels of a threat response, and the highest cardiac workload. When presented with a constant avatar, they had a challenge response and low levels of cardiac workload. As a result, it is conclusive that female self-perception has a significant influence on physiological response when body dissatisfaction is high. Exergames must include options that tailor to each individual based on their ESE as well as their preference of performance tracking during exercise.

Tips for implanting rodent pups with the Epoch wireless recording system

Implanting pups can be tricky, yet their value as neonatal models of human disease is key.

Tips for implanting rodent pups with the Epoch wireless recording system

The Epoch system enables recording 2 or 4 channels of EEG from neonatal rodents as young as postnatal day 10 (P10) in mice and P6 in rats using the 2-week transmitter. Implanting pups can be tricky—their skulls are very thin and the small size of the animals is difficult to work with. Yet, their value as neonatal models of human disease is key to developing new therapies or understanding neural dysfunction at such an early age.

Our experience has led to the following tips for maximizing the success of implanted pups:

Allow pups time to recover. Although recordings can commence immediately, we recommend waiting 24 hours before commencing recordings to allow a fuller recovery.

Limit recording time. Recording from rodent pups should be limited to about 2 h at a time, preferably in a temperature- and humidity-controlled incubator.

Keep pre-weened pups in their dam’s presence as often as possible. Pups rely on the dam for complete care.

Cull the litter to 4-6 pups. The dam may have issues with pups that are overly cold, not feeding often enough, or simply due to the presence of the transmitter.

Implant all pups. It may be helpful to implant all pups in a litter either with Epoch transmitters or sham transmitters (sham transmitters are available, contact us).

Use chew toys to prevent damage from the dam. Chew toys, such as nylabones, may help prevent the dam from chewing on the transmitters.

Mind the state of the dam. Ultimately, the health and disposition of the dam may affect how she tolerates pups implanted with the Epoch transmitters.

Epoch, the smallest wireless EEG transmitter system available, is provided by BIOPAC to make quality EEG recordings from an early age possible. The Epoch transmitter is simply implanted to the skull of the animal with medical cyanoacrylate, requiring no bone screws. Surgery is quick and simple, requiring a small incision on the scalp, removal of the periosteum with 1% hydrogen peroxide, drilling small holes for the electrodes using a burr-type drill, implanting the transmitter, and re-absorbable sutures.

For more information on BIOPAC’s wide range of tools for recording, displaying, and analyzing EEG signals from human and animal subjects, including automated EEG analysis, seizure detection, evoked responses and many others, visit BIOPAC’s EEG Analysis page or view BIOPAC’s full line of electrodes, amplifiers, and wearable, wireless transmitters and loggers.

BIOPAC Systems, Inc. provides life science researchers and educators with data acquisition and analysis systems that inspire people and enable greater discovery about life. Visit us at www.biopac.com.

Stressing over the effects of stress

Several studies show chronic stress is typically detrimental to health, while acute stress may be linked to positive effects in addition to the negative counterparts

With April comes National Stress Awareness Month, and it bears noting that different types of stress have varying effects. Where chronic stress is typically detrimental to health, acute stress may be linked to positive effects in addition to the negative counterparts. But is this trade-off worth it?

In a biological psychology experiment testing the effect of oxytocin on acute social stress, researchers found different results between men and women. Subjects underwent several stress tasks while their electrocardiography and impedance cardiography were recorded with a BIOPAC MP Research System and amplifiers. The researchers found that after being given oxytocin during the stressful event, men had less negative affect and women had greater math performance (compared to the control group).

A neurobiology study examined the effect stress had on an extinction memory process when a competing association was paired with a previously aversive cue. To test this, participants were presented with two images, one that was paired with a shock from a BIOPAC bar electrode, and one that was not. Extinction memory training immediately followed this stimulus, with extinction retrieval testing following a day later. Data gathered by a BIOPAC data acquisition system suggested significantly lower retrieval in the group that experienced the acute stress stimulus.

Another biopsychology experiment measured the effect of acute stress on pro-inflammatory cytokine levels in the blood. BIOPAC equipment was used to measure ECG while participants were given the Trier Social Stress Test. After reviewing the data and blood samples, the researchers determined that levels of the cytokine cell, interleukin-1β, increased significantly immediately after the stress test.

The physiological and psychological impacts of stress are clearly multifaceted with many potential results. In some situations, a heightened positive affect or greater analytical thinking may be beneficial. But is this boost in mental performance worth the increase of inflammatory cells and lower memory retention? As with many aspects of life, moderation is the safest answer, ensuring the negative effects do not become chronic problems.

For more information on BIOPAC’s wide range of tools for recording, displaying, and analyzing ECG measurements from human and animal subjects including respiration, heart rate variability, and RSA, visit BIOPAC’s electrocardiography pages and view BIOPAC’s full line of electrodes, amplifiers, and wearable, wireless transmitters and loggers.

The Trouble with Fatigue

Fatigue is a troublemaker–it can have serious impacts on data quality, even when using gold standards of measurement.

Fatigue is a known troublemaker in athletics, but can also have negative effects in physiology research. Fatigue can become a confounding variable, giving researchers data that may be less accurate or reliable.

Men and women may respond to fatigue differently, which can make obtaining good data especially difficult. In one study on fatigue by Stern et al. (2012), the researchers attempted to monitor fatigue and show different effects between men and women. This study attempted to follow a central nervous system component, as well as the peripheral nervous system. Using the BIOPAC MP160 system with AcqKnowledge software to record and analyze EMG, researchers were able to continually monitor muscle and neuron activation during the exercise tests.

The results of the study found that females had a higher rate of reduced central neural drive of the quadriceps, coupled with knee extension torque preservation. These factors, when paired together, can create a higher percentage for the possibility of knee injury for women.

With coffee being such a staple in the home (and in the lab!), researchers Smirmaul et, al (2017) wanted to see if coffee had any effect on fatigue, duration of exercise, and the perception of effort. This study used seven adult male cyclists in moderate hypoxic states to obtain their results. The experiment used a double-blind procedure, with some participants receiving no coffee. The researchers wanted to see if the coffee participant group took a longer time to reach fatigue. EMG was obtained by using BIOPAC MP160 with EMG amplifiers. The results showed that coffee has no effect on fatigue, but coffee did improve the time it took until the athletes reached exhaustion in high endurance tasks. The researchers believe that coffee lowers the perceived effort of the athlete, leading them to think they can go further.

Fatigue can also have impacts on data, even when using gold standards of measurement. A separate study done on fatigue by Neyroud et al. (2016), attempted to show that muscle fatigue has an effect on the validity of the ITT (Interpolated Twitch Technique). The ITT is used to evaluate the capacity of the central nervous system in activating skeletal muscles. This study used BIOPAC’z MP research system with EMG amplifiers to monitor muscle and neuron activation. Electrical stimulus was given to both samples to create fatigue, and a separate stimulus was given to mimic the ITT. This study found that peripheral fatigue factors do have an effect on the outcome of the ITT.

BIOPAC offers a variety of equipment that can be used in studies similar to the ones presented. To find more information on solutions for recording and analyzing signals such as EEG, EMG, respiration, skin conductance using the MP160/MP150, MP36, and other platforms, you can visit the individual application pages on the BIOPAC website. If you are interested in reading other related studies, visit the publications page on the BIOPAC website.

Holiday Happiness Part 2: Sounds, Smells, and Self-Reflection

In a previous post, we discussed the stress-reducing benefits of loving interactions with close friends and family during the holiday season. In addition to family, there are many mood-shaping habits and activities that characterize the holidays: the smell of home-cooked meals, seasonal music, and reflection on the past year, to name a few. But do these have a real impact on happiness?

In a psychophysiology study, Matsunaga, et al., tested odor effects on autobiographical memory recall. The researchers introduced several odor stimuli to participants and measured their psychological and physiological reactions. Heart rate and skin conductance were recorded throughout the experiment with a BIOPAC data acquisition system. The odor stimuli resulted in decreased heart rate, increased skin conductance level, and an increase in positive mood states.

Another article tested the effects of meditation on emotional regulation. Participants completed emotional measures before and after a meditation intervention, and had their ECG, respiration, and blood pressure recorded using a BIOPAC MP unit. The meditation correlated with greater participant emotional regulation, as suggested by lower heart rate and respiration.

In addition to meditation and smell, Harmat and Eerola have found music to also be emotionally significant. Participants listened to a musical piece, and then responded to a questionnaire about their emotional state. In addition to measuring pulse rate and facial expressions, the BIOPAC Research System and EDA Amplifier were used to record skin conductance while participants listened to the stimulus. The results found that music samples evoked several emotions, including nostalgia and happiness.

This research suggests that we can affect happiness using subtle techniques that are part of everyday living. To read more studies about psychophysiology and stress reduction, visit the BIOPAC publication page.

BIOPAC offers a variety of equipment that can be used in studies similar to the ones presented. To find more information on solutions for recording and analyzing signals such as skin conductance, ECG, heart rate, respiration, and EDA using the MP160/MP150, and other platforms, you can visit the individual application pages on the BIOPAC website.