Posts Tagged ‘Electroencephalography’

Tools of Cognitive Neuroscience

September 10, 2019

The title of this post is identical to a chapter title in an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” The tools of cognitive neuroscience are highly technical. If the reader is interested in these techniques she should read Dr.Slotnick’s book, or look up the tools of interest in the Wikipedia.

One of the earliest techniques was positron emission tomography (PET). It required that a low level of radioactive material be injected into the participants bloodstream. This technique measured increased blood flow to the portions of the brain being activated. Fortunately a new technique that measured blood flow was found that did not require the injection of radioactive dye or any other type of material.

That technique was functional magnetic resonance imaging (fMRI), which also measured where in the brain the blood flow was increasing.

Event-related potentials (ERPs) can track brain activity in real time. ERPs directly measure neural activity and have a temporal resolution in milliseconds. Its spatial resolution is in centimeters, which is much lower than fMRI.

Electroencephalography (EEG) uses the identical data acquisition as ERPs, but refers to any measure of brain activity that corresponds to electric fields. This includes ERPs, but more commonly refers to brain activity that oscillates within a specific range of frequencies. EEG frequency analysis is a powerful alternative to the more commonly employed ERP analysis. Related to EEG, magnetoencephalography (MEG) refers to any measure of brain activity that corresponds to magnetic fields, and also typically refers to brain activity that oscillates within a specific frequency range. Like ERPs that are generated by averaging all the events of a given type from EEG data during a cognitive task, event-related fields (ERFs) are generated by averaging all the events of a given type from MEG data. The more general terms EEG and MEG also refer to ERPs and ERFs.

Dr. Slotnick writes, “fMRI is by far the most popular method in the field of cognitive neuroscience. However, brain activity is not a static set of blobs that represent a cognitive process. Rather, brain activity changes across different regions in milliseconds. Only techniques with excellent temporal resolution, such as ERPs, can track the functioning brain. This book highlights the temporal dimension of brain processing in addition to the spatial dimension of brain processing. One major advantage of temporal information is that one can use it to assess whether different brain regions are synchronously active, which indicates that these regions interact. This reflects how the brain is actually operating.”

Transcranial magnetic stimulation (TMS) can be used to temporarily disrupt processing in one region of the brain.

Transcranial direct current stimulation (tDCS) is similar to TMS in that it temp[orarily modulates processing in a target cortical region by stimulating with a weak direct current rather than a magnetic field.

A relatively new method called transcranial alternating current stimulation (tACS) uses the identical setup as tDCS, but the current alternatives at a specific frequency; this, tACS can stimulate the brain at a desired frequency.

Do not let yourself be discouraged or turned off by this technical stuff, but brief explanations are needed as these are the tools used in this research. The remainder of the posts will be on memory performance and on the portions of the brain contributing to this performance.


February 27, 2013

According to Costa, the author of The Watchman’s Rattle: A Radical New Theory of Collapse, what will save us all is the ability of the human mind to achieve insight. She writes of insight as it it is a new discovery. The notion of insight and an “aha” moment in solving problems goes back to the Gestalt psychologists at least. What is new is the identification cognitive structures involved in achieving insight.

Costa stresses that insight is a biological capability that we all have. She cites an article1 that describes an experiment in which the cognitive structures were identified. Nineteen experimental participants were asked to solve word problems while the activity in their brains was monitored. Three words were presented, such as pine, crab, and sauce, to each participant. The task was to think of another word that could be combined with each of these words to make three new words. For example, a solution to these words would be “apple,” to produce “pineapple,” “crabapple,” and “applesauce.” The participants did many of these problems and brain activity was tracked to identify and differences that signaled an insightful answer. When insight was used the anterior Superior Temporal Gyrus (aSTG) became highly excited producing a sudden burst of gamma oscillatory activity. This occurred 300 milliseconds in advance of solving the problem. They also discovered that the Anterior Cingulate Cortex (ACG), which is responsible for relaying signals between the left and right hemispheres of the brain, appears to suppress irrelevant thoughts prior to invoking insight. The notion is that insightful thinking is more vulnerable to external interference than is nonsightful processing necessitating greater suppression of external thoughts. When insight is achieved, the problem solver is confident of her insight. Insight is cognitively taxing. Increased electrical activity takes place in the left posterior M/STG, the anterior cingulate, the right posterior M/STG, and the amygdala. Costa argues that insight is the brain’s special weapon against complexity. A simplifying insight eliminates the complexity.

Insight and creativity are closely related. I would suggest that insight is a special type of creativity, one aimed and solving a particular problem. Insight is creative, but creativity also includes literature, fine art, music, and dance to name just a few activities.

1 Kouinios, J.K., Frymiare, J.L., Bowden, e.M., Fleck, J.I., Subramanaiam,K, Parrish, T.B., & Jung-Beeman, M. (2006). The Prepared Mind: Neural Activity Prior to Problem Presentaion Predicts Subsequent Solution by Sudden Insight. Psychological Science, 17:882, DOI:10.111/j.1467-9280.2006.01798.

© Douglas Griffith and, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Improving Nonjudgmental Awareness

May 20, 2012

If you have read the Healthymemory Blog post “Attentional Style” (and if you have not, you should read it before proceeding) you should remember that Dr. Davidson states that there are two types of attention: selective attention and nonjudgmental awareness.1 This blog post deals with nonjudgmental awareness.

Dr. Davidson recommends open-monitoring meditation, in which your attention is not focused on any particular object. Instead you cultivate an awareness of awareness itself. Before beginning this type of meditation, Dr. Davidson recommends beginning with focused-attention meditation such as breath meditation to to give you a level of basic attentional stability. This should make open-monitoring meditation.

He provides the following basics of open-minded meditation:

“1. Sit in a quiet room with a comfortable chair, with your back straight but the rest of your body relaxed. Keep your eyes open or closed whichever is more comfortable. If your eyes are open, gaze downward and keep your eyes somewhat unfocused.

      1. Maintain a clear awareness and openness to your surroundings. Keep your mind calm and relaxed, not focused on anything specific, yet totally present, clear, vivid and transparent.

      2. Lightly attend to whatever object rises to the top of your consciousness, but do not latch on to it. You want to observe the thinking process itself, perhaps saying to yourself, Oh, I notice that the first thing I think about as I sit down to meditate is…

      3. Give your full attention to the most current salient object of consciousness, focusing on it to the exclusion of anything else, but without thinking about it. That is, you are simply aware of it, observing it as disinterestedly as possible, but do not explore it intellectually.

      4. Generate a state of total openness, in which the mind is as vast as the sky, able to welcome and absorb any stray thought, feeling, or sensation like a new star that begins shining. When thoughts arise, simply let them pass through your mind without leaving any trace of it. When you perceive noises, images, tastes, or other sensations, let them be as they are without engaging with them or rejecting them. Tell yourself that they can’t affect the serene equanimity of your mind.

      5. If you notice your mind moving toward thought or feeling, let it do so, letting the newcomer slip into consciousness. Unlike in attention-strengthening forms of meditation, you do not try to shoo away the “intruding” thought, but allow your mind to turn to it. The key difference between breath-focused attention discussed previously is that in open-monitoring meditation there is no single focus to which the attention is redirected if it wanders. Rather, you simply become aware of whatever is in the center of attention at the moment.

      6. Turn to this new object of attention as you did the first.

      7. Do this for five to ten minutes.2

Dr. Davidson lists the following meditation centers that offer courses, books, and CDs on open-monitoring meditation: Insight meditation Society in Barre, MA; Spirit Rock Meditation Center in Woodcare, CA; and Tergar Meditation Group in Minneapolis, MN.

Dr. Davidson did a study in 2009 in which it was found that practitioner of open-monitoring meditation showed phase locking in their EEGs. That is, their brain waves were modulated to make them more receptive to outside stimuli. It is somewhat ironic to note that this phase locking is also an indication of selective attention as we noted in the “Attentional Style” Healthymemory Blog Post. But as it was noted in that blog post, these two types of attention complement each other.

You can also alter your environment to expand your attentional awareness. Put books and magazines around to tempt yourself to read something new. Keep your room or office open to the outside world. Place photos of loved ones on your desk so you can glance at them as you work. Set the alarm on your cell phone or computer to chirp every twenty to thirty minutes to cue you to think of something else.

1Davidson, R.J., & Begley, S. (2012). The Emotional Life of Your Brain. New York: Hudson Street Press.

2Davidson, R.J., & Begley, S. (2012). The Emotional Life of Your Brain. New York: Hudson Street Press. pp. 240-241.

Attentional Style

April 25, 2012

Attentional Style is the last of Davidson’s Six Dimensions of Emotional Style1 to be discussed. But it is certainly not the least important dimension. It is the most important dimension as regular readers of this blog should have anticipated. With respect to a healthy memory, it is the most important dimensions as memory failures are typically due to a failure to pay attention. It is also a key building block for other dimensions as it is difficult to be self-aware or to be tuned in to social cues or sensitive to social context if one is not paying attention.

Davidson notes that there are two types of attention. One is the ability to selectively attend to stimuli that are of interest and to tune out extraneous stimulus. The other type of attention is nonjudgmental awareness. These two types of attention complement each other. Without the ability to selectively attend, the amount of stimulation and information is overwhelming. However, excessive selective attention can cause you to miss important cues or information.

The prefrontal cortex is involved in selective attention. Davidson describes an experiment in which the participants were to push a button when a sound of a certain pitch (high or low) was presented to a particular ear (left or right). EEGs were taken while the participants performed this task. Analyses of the recorded brain waves indicated that participants who performed this task better (where better able to selectively attend) had electrical signals from the prefrontal cortext that exhibited “Phase locking.” That is, the signals from the prefrontal lobes became synchronized precisely with the arrival of the tones.

Specific patterns of brain activation were also found during a study of open, nonjudgmental awareness that Davidson conducted. In this study strings of digits and letter were presented and the task was to to respond whenever a digit occurred. There is a phenomenon termed the attentional blink (or psychological refractory period) in which the response to the second occurrence of a digit is either missed or delayed. EEG recordings were taken of the participants while they performed this task. The EEG data recorded an event related potential known as the P300. It refers to a positive electrical response that occurs about 300 milliseconds after the presentation of a stimulus. Too strong a P300 response indicated that too much attention was expended on the first occurrence of the target stimulus, so that second presentation was missed. Too weak a P300 response typically indicated that both target stimuli were missed. So balanced, nonjudgmental awareness is characterized by a “Goldilocks” P300, not too much and not too little, but just right.

Here is where the emotional brain and the rational, thinking overlap. Clearly the emotional brain affects rational thinking, and is important to a healthy memory.

1Davidson, R.J., & Begley, S. (2012). The Emotional Life of Your Brain. New York: Hudson Street Press.


April 15, 2012

Resilience is one of the dimensions of Davidson’s Six Dimensions of Emotional Style.1 It refers to how quickly you bounce back from adversity. Do you bounce back quickly or do you let something bad keep you down for a prolonged length of time? Resilience is another “Goldilocks” variable in that you can have either too much or too little of it. Moreover, what is “just right” regarding resilience depends on the situation. If you just failed an examination, it might be worthwhile ruminating about it for a reasonable amount of time, not too excessive, trying to understand why you failed and how you might avoid similar failures in the future. However, you often see athletes compound an initial error by stewing over it, rather than quickly getting over it and attending to the immediate needs of the game or performance.

Davidson and his colleagues have performed some interesting research regarding the brain structures underlying resilience2. They did a study in which EEGs were recorded from the research participants scalps. Recordings of brain activity were done while 51 pictures were presented on a video monitor. However, before the pictures were presented the baseline level of brain activity was assessed for eight minutes. One-third of the pictures depicted upsetting images, another third pleasant images, and the other third neutral images. Sometime during or after a picture a short burst of white noise sounding like a click was presented. This was a startle probe that tends to make people blink involuntarily. Sensors were placed under one eye to determine when the eye blinked. When people are in a negative emotional state these startle-induced blinks are stronger than in a neutral state. When in a positive emotional state these startle-induced blinks become weaker still. This allowed the researchers to gauge how quickly a research participant recovered from a negative emotional state.

People who had greater activation in the left side of the prefrontal cortex recovered more quickly than the others. The amygdala is a subcortical structure (you have one in each hemisphere of your brain) that responds to negative or unpleasant stimuli. There is communication between the prefrontal cortex and the amygdala. Activity in the left prefrontal cortex shortens the period of amygdala activation allowing the brain to bounce back from an upsetting situation.

MRI brain imaging research has shown that the more white matter (axons that connect one neuron to another) lying between the prefrontal cortex and the amygdala, the more resilient you are. The less white matter lying between the prefrontal cortex and the amygdala, the less resilient you are.

Do not conclude from this that you are stuck with a fixed level of reslience due to the amoung of white matter you have between your prefrontal cortex and your amygdala. Research has indicated that this can be changed. In a later post, I will present techniques offered by Dr. Davidson as to how to change your level of resilience.

1Davidson, R.J. & Begley, S. (2112). The Emotional Life of Your Brain. New York: Hudson Street Press.


Rewiring the Brain

February 29, 2012

Research1 has shown that the use of the internet can result in the rewiring of the brain. Four neuroscientists at UCLA recruited 24 people ranging in age from 55 to 76 who underwent brain imaging while they did internet tasks. Twelve participants were termed net naïve, meaning that they went online just once or twice a week. The remaining 12 participants were termed net savvy, meaning that they went online at least once a day. All participants performed two tasks while their brains were being scanned. In the traditional reading task they read text on the computer presented in the format of a book. In the internet task, they performed a Web search and read content displayed on a simulated web page.

Both groups exhibited basically the same brain activity performing the traditional reading task. They used areas of the brain connected to language, memory, and reading. During the internet task, the net naïve group exhibited the same pattern of brain activity. However, the net savvy group exhibited additional areas of brain activity. These were areas associated with decision making and complex reasoning. Moreover, the net savvy group exhibited more than twice as much brain activity as the net naïve group, 21,872 voxels to 8,642 voxels of brain scan.

Subsequent research indicated that after just five days of Web training after the initial experiment, naïve brains began to work as savvy ones. So this rewiring takes place fairly quickly.

Some might argue, that although this result might be impressive, what is its bearing on a healthy memory. I would refer you to the healthymemory blog post, “Computer Use and Cognition Across Adulthood,” which shows the correlation between computer use and a healthy memory.

1Jaffe, E. (2012). Rewired: Cognition in the Digital Age. Observer, 25,2, 16-20. A Publication of the Association for Psychological Science.

© Douglas Griffith and, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Brain Conversations

November 6, 2011

For most lay people, consciousness is psychology. It is how we deal with the world. These people would be surprised to learn that for many psychologists and philosophers, consciousness is an epiphenomenon, meaning that it is not real. They would argue that we do experience consciousness but that it is a byproduct of cognitive processes that have already occurred at an unconscious level. In other words, consciousness is just along for the ride. Articles1 in a recent Scientific American Mind present this view.

Although it is true that the vast majority of cognitive processing does occur below the level of consciousness, does that mean that consciousness is irrelevant? The purpose of consciousness has been and continues to be a hotly discussed topic. Baumeister has provided perhaps the most compelling explanations of the purpose of consciousness. He argues that conscious thought is for internal processing that facilitates downstream interaction with the social and cultural environment. Consciousness enables the construction of meaningful, sequential thought. These constructions are found in sentences and narratives, logical reasoning, quantification, causal understanding, and narratives. In short, it accounts for intellectual and social life. It is used for the simulation of events. (See the Healthymemory Blog Post, “Conscious Thought”)

An article2 written for a different purpose provides support for Baumeister’s ideas. This article dealt with awareness. This topic is important in the context of trying to diagnose patients in a vegetative or minimally conscious state. Misdiagnosis rates here can be as high as 40 percent. A neural correlate for consciousness is much needed. For many years theorists thought that the prefrontal cortex was key and that neural thoughts that reached this area emerged from unconscious obscurity into awareness. However, new research supports the notion that consciousness is a conversation rather than a revelation, and that no single brain structure leads the dialogue.

The neuroscientist Simon van Gaal conducts experiments in which he asks participants to push a button every time they see a certain symbol flash on a screen, except when they see a different symbol that means “stop.” On some trials the stop signal is presented below the level of conscious awareness. Although participants do not see the stop signal, they do hesitate to push the button as though some part of the brain perceived the information. Brain activity is recorded during the experiment via functional MRI and electroencephalography (EEG). The unconsciousness inhibitory signal seems to make it all the way up to parts of the prefrontal cortex despite the participants not being consciously aware of the signal.

Another study supports the claim that awareness emerges when information travels back and forth between brain areas rather than from an ascending linear chain. EEG signals were recorded in patients with brain damage as they listened to stimulating tones. All the patients were awake and alert but exhibited different levels of responsiveness. Mathematical models derived from the data suggest that feedback between the frontal cortex and lower-level sensory areas are crucial to producing conscious awareness. Similar results have been obtained with monkeys and healthy human participants.

Although these studies do not prove Baumeister’s notions regarding the role of consciousness, they do seem to provide supportive evidence.

1Nichols, S. (2011). Is Free Will an Illusion? Scientific American Mind, November/December, 18-19.


Koch, C. (2011). Probing the Unconscious Mind, Scientific American Mind, November/December,, 20-21.

2Peck, M.E. (2011). A Conversation in the Brain. Scientific American Mind, November/December, 12.

© Douglas Griffith and, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.