pscyhophysiology Archives

Getting the Bands Back Together – Components of the EEG Signal

Many notable events occurred in 1929, not all of them good. The St. Valentine’s Day massacre. The stock market crash that triggered a worldwide economic crisis. The chain saw was invented. Not much good was happening in Germany either. Rampant inflation, the decline of the Weimar Republic, and the implacable rise of Nazism. But 1929 was also the year that German physician Hans Berger made an important scientific discovery that continues to influence how we study the human brain today. Dr. Berger discovered that electrodes placed on the human scalp could detect various patterns of electrical activity. After further study confirmed that these patterns were indeed related to brain activity and not mere scalp muscle artifact, scientists began to delve into the constructs of these “brain waves.” Today, electroencephalography (EEG) is still the primary method employed for recording brain function. In medical and basic research, correlation of particular brain waves reveals valuable information about sleep phases, emotional states, psychological profiles, and other mental activities. Much of this information is derived from five simple periodic rhythms, or frequencies, recorded in the EEG signal—alpha, beta, delta, theta, and gamma waves. These frequencies are known to be associated with specific degrees of alertness, affect, emotional states, and sleep. What do these frequency bands tell us about what is going on behind the gray matter? Allow us to introduce the band members.

Alpha (8-13 Hz) – Mellow Band Member

Alpha waves are associated with relaxation and calm. In general, the alpha rhythm is the prominent EEG wave pattern of adult subjects who are awake, but relaxed with eyes closed. Each region of the brain has a characteristic alpha rhythm but alpha waves of the greatest amplitude are recorded from the occipital and parietal regions of the cerebral cortex. In general, alpha wave amplitudes diminish when subjects open their eyes and are attentive to external stimuli, although some subjects trained in relaxation techniques can maintain high alpha amplitudes even with eyes open.

Beta (13-30 Hz) – Band Manager

Beta waves are related to memory, focus, and problem-solving. beta rhythms occur in alert individuals who are attentive to external stimuli, or exerting specific mental effort. Paradoxically, beta rhythms also occur during deep REM sleep. Beta waves may also be associated with “remembering” or retrieving memories.

Delta (1-5 Hz) – Supportive Band Member and Theta Rhythm (4-8 Hz) – Creative Band Member

Delta and theta rhythms are low-frequency EEG patterns that increase during sleep in the normal adult. Delta waves are associated with rejuvenation of the body through restorative deep sleep. Theta waves are more aligned with creativity and emotional connection. As people move from lighter to deeper stages of sleep (prior to REM sleep,) the occurrence of alpha waves diminishes and is gradually replaced by the lower frequency theta and then delta rhythms.

Although theta and delta rhythms are generally most prominent during sleep, there are cases when delta and theta rhythms are recorded from individuals who are awake. For example, theta waves will occur for brief intervals during emotional responses to frustrating events or situations. Delta waves may increase during difficult mental activities requiring concentration. In general, the occurrence and amplitudes of delta and theta rhythms are highly variable within and between individuals.

Gamma (> 32 Hz) – Perceptive Band Member

Gamma waves bring to the party cognition, information processing, learning, memory, and perception. Gamma waves were largely overlooked before the development of digital electroencephalography, as analog electroencephalography is restricted to recording and measuring rhythms that are usually less than 25 Hz.

A gamma wave is considered to be the “fastest” brain activity. The prominence of this wave leads to anxiety, high arousal, and stress. In optimal conditions gamma waves help with attention, focus, binding of senses (smell, sight, and hearing), consciousness, mental processing, and perception.

Research studies reported that gamma activity is involved in attention, working memory, and long-term memory processes, although excessive Gamma activity is also involved in psychiatric disorders such as schizophrenia, hallucination, Alzheimer’s disease, and epilepsy.

So in a sense, the periodic rhythms alpha, beta, delta, theta, and gamma, like the members of a tight musical ensemble, have distinct but overlapping roles for enabling the human brain to achieve wondrous things great and small that are often taken for granted.

BIOPAC Systems, Inc offers the following solutions for recording and analyzing EEG signals for research and education applications.

MP160 System with AcqKnowledge Software
EEG100D Smart Amplifier
EEG100C Amplifier Module
EEG100C-MRI Amplifier Module
BioNomadix Wireless EEG
BioNomadix Smart Center
Mobita 32-Channel Wireless EEG System
B-Alert Wireless EEG with Cognitive States Software
EPOCH Wireless In Vivo Neural Recording Systems—longterm EEG for rats, mice, or pups
Biopac Student Lab Systems—with EEG I, EEG II, and Hemispheric EEG lessons

We also invite you to enjoy our library of free EEG webinars on our Webinars page.

The Physiology of Election Decision-Making

The psychophysiological factors of stress, the behaviors of others, and of introception can play major roles in decision-making, and BIOPAC systems provide measurements of how physiological factors such as these influence decisions.

People experienced varying stress levels because of the 2016 US presidential election. There are a variety of factors that can impact voting behaviors and decision-making. Several recent studies using BIOPAC systems investigated the psychophysiological effects of stress, the behaviors of others, and introception on decision-making.

Stress has been shown to be very influential in decision-making. In their study, Yamakawa, Ohira, and Mastunga Isowa (2016) investigated effects of acute stress and risk taking in decision-making. Participants were asked to perform a decision-making choice where they either kept or bet the money they were given. Cardiodynamic activity was measured with ECG using a BIOPAC MP system. Results suggest that with an increase in cortisol, adrenaline, heart rate, and subjective stress, participants were likely to make fewer risky choices. So, high levels of stress may be key in helping make better decisions when selecting a future president.

Perhaps it’s not stress that will influence the choice of the next POTUS (President of the United States), but rather the behaviors of others. Work by Bault, Joffily, Rustichini, and Coricelli (2011) sought to compare private and social decision-making to discover the effect of social comparison on risky choices. The objective of the study was to understand more about how individuals evaluated the outcomes of their decisions in private as opposed to in a social context. Combining data from functional MRI (FMRI) and skin conductance recordings, subjects’ reactions were measured using a BIOPAC MP150 System. Researchers found that participants took significantly longer to make a decision in a social setting than in a private one.

In the end, many feel that it is important to listen to your heart when deciding who you find qualified to be the next president. A study by Dunn et al. (2010) examined whether introception moderates the coupling of bodily responses to emotional experience and intuitive decision-making. Bodily response and heart rate were recorded using a BIOPAC Research System and electrodes to measure introception through changes in heart rate. Researchers found that introception was not related to arousal, valence ratings, or heart rate response to images.

For more information on BIOPAC’s wide range of tools for recording, displaying, and analyzing physiological measurements from human and animal subjects including respiration, heart rate variability, ECG and EDA, visit BIOPAC’s psychophysiology page 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.

Start the First Class with EDA and Emotional Responses!

By Howard Iver Thorsheim, Ph.D., St. Olaf College. I wanted to start the first day of my class with an activity that would engage students’ curiosity and enthusiasm, to set the stage for introducing the course and going over the syllabus!

By Howard Iver Thorsheim, Ph.D., St. Olaf College

Howard Iver Thorsheim is Professor of Psychology and Neuroscience at St. Olaf College, Northfield, Minnesota, USA. In these blogs he offers his first-person insights into effective teaching techniques gleaned from a combination of scholarly research and over 40 years in the classroom.

I find Electrodermal Activity (EDA) to be a great way to demonstrate psychophysiology measurement at the beginning of a course: students easily understand it. It takes little time to set up and record because it only involves two sensors on the finger tip pads. It works every time as a “window” to emotions with clear responses to a variety of stimuli (e.g., visual, auditory, gustatory, olfactory).

I show students a picture of a rock climber climbing a cliff, then ask them to jot down some notes of what they might feel when climbing like the woman pictured, and then buzz with a person sitting next to them about what they wrote. I ask for a show of hands of who has mentioned the bag hanging from the climber’s belt. Depending on the amount of time I choose to devote to the activity, I lead the entire class through a number of probing questions; for example:

“Who knows what the bag is for?” (Chalk for fingers.)

“Why does the climber use chalk?” (Reduce slipperiness from sweat.)

“Why do fingers get slippery?” (Emotion.)

“What other people encounter emotion daily?”

I then set the stage for EDA: changes in skin conductivity are due to the amount of sweat in sweat glands of the skin, which are produced by the sympathetic branch of the autonomic nervous system responding to emotion.

I explain to the class that I will be the first volunteer, and guarantee that no shock is involved using BIOPAC equipment. I connect electrodes on the volar pads of my index and middle fingers, and take a deep breath, which will generate EDA. Then I tell the class I will think of emotion-producing situations, and ask them if they can see any EDA detected by the equipment. There will be a few good chuckles because in anticipation of doing so, my response will already appear. Two of several easy classroom measurements of EDA include latency (about 1 to 3 seconds between a stimulus and beginning of the electrodermal response), and peak amplitude (the maximum size of the response). My eBook Doing Psychophysiology–Getting Started on the Apple iBooks Store has a graphic narrative and a one-minute video explanations about EDA, as well as other psychophysiology measures you can show your students. The Biopac Student Lab system also includes two lessons in which students can engage in interactive learning activities while measuring EDA; a lesson on the principles of biofeedback and one on the standard physiological measures of a polygraph.

An excellent summary of Electrodermal Activity is provided in the following chapter:

Dawson, M. E., Schell, A. M. & Fillion, D. L. (2007). The electrodermal system. In J. T. Cacioppo, L. G. Tassinary, & G. G. Berntson (Eds.). Handbook of psychophysiology (3^rd ed. pp. 159-181). New York: Cambridge University Press.

Learn more about BIOPAC’s education solutions, including complete teaching systems for psychophysiology and the life sciences. BIOPAC also provides a wide range of research systems for recording, displaying, classifying, and analyzing psychophysiological measurements.

Professor Thorsheim is a licensed Psychologist, educator, and author. He has published or presented over 125 papers, journal articles, books, book chapters or monographs, and received a patent in 1985 as a co-inventor for an educational book design with interactive elements. His work has been funded by marquee foundations across the globe. His most recent work is Doing Psychophysiology: Getting Started, available from Knowledge Growers, Inc., available as an iBook download in 51 countries.