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What Is Consciousness? Measuring Consciousness with EEG & fMRI

May 19, 2020

What is Consciousness?

We inherently know what it means to be conscious, yet we have a difficult time explaining it… so what exactly is consciousness?  Throughout history (and still to this day), philosophers and scientists have not fully understood human consciousness. 

Back in the 1600s, philosophers believed that the mind was completely separate from the rest of the physical body, but since then large bodies of research have proven a deep connection between the mind and body. 

According to the Canadian textbook Introduction to Psychology, consciousness is “our subjective awareness of ourselves and our environment” (1). 

Though it seems broad, essentially consciousness is a defining feature of what it is to be human and to be alive. 

 

Consciousness, guided meditation

Now, psychologists and neuroscientists like German-American neuroscientist Christof Koch believe consciousness to be a result of the firing of neurons in the brain and at different wavelengths. Koch believes that for “each conscious experience, a unique set of neurons in particular brain regions fires in a specific manner” (2). 

Koch goes on to describe consciousness as “…everything you experience. It is the tune stuck in your head, the sweetness of chocolate mousse, the throbbing pain of a toothache, the fierce love for your child and the bitter knowledge that eventually all feelings will end.”

In a very summarized way, the mind (non-physical) exists within the brain (part of the physical body) and we experience different states of consciousness depending on what the brain is doing (1).  However, what science has not been able to understand yet is precisely how consciousness actually emerges from the activity in the brain (2).

A Conscious State vs. An Unconscious State

One of the key components of consciousness is free will, or the ability to have control over our behaviours, therefore being conscious implies more than just being alive.  When we sleep, for example, we are considered unconscious as we are not aware of ourselves. 

A person can also lose consciousness temporarily, such as during sleep or anesthesia, or more permanently as is the case with certain brain injuries. Important to note is while unconsciousness behaviorally displays as a failure to respond to stimuli, this behaviour is not always the result of unconsciousness.

For example, unresponsive coma patients can display brain activity that looks similar to that of healthy, fully conscious individuals when asked to imagine performing a physical task such as playing tennis. Such a mental response in the absence of physical feedback is a condition known as cognitive-motor dissociation.

What is interesting is that we can also be awake and engage in unconscious behaviours that we have very little control over.  Take for example the endless amount of social media posts showing what their family members/friends are like after being anesthetized for dental surgery—awake but at an altered state of consciousness. 

Another example of an altered state of consciousness is sleepwalking.  Often people who sleepwalk have no recollection of what they did or what happened while they were sleepwalking during the night. 

consciousness, guided meditation

How Do You Measure Consciousness?

Measuring Consciousness Using EEG

There are four main types of brainwaves that correlate with different states of consciousness—alpha, beta, delta, and theta.  These brainwaves (or “neural oscillations”) vary depending on what level of activity we are engaged in, with the spectrum generally ranging from wakeful alertness to fully asleep.  Relaxation, excitement, focused attention, and various stages of sleep will all show differing dominant brain wave activity (3). 

Neural oscillations and states of consciousness can be affected by external stimuli such as (4):

  • Alcohol and hallucinogenic drugs
  • Hypnosis
  • Sensory deprivation
  • Meditation

When we are fully alert, the brain operates in predominantly beta brainwave patterns.  These are higher frequency, more active waves and so if you are in this mode for too long with no rest, you can feel fatigued.  During relaxed waking states such as daydreaming and light meditation, brainwave patterns typically show lower frequency alpha brainwave patterns. 

consciousness EEG, guided meditation
Sample (A) wake (blue) and (B) sedated unconsciousness (red) EEG from archival Fp1 recording. Raw EEG data are filtered via AAR2 to remove eye-blink artifacts. AAR-corrected EEG are marked in black. The power spectra show that slow-wave oscillations are dominant in the sedated unconsciousness state. Wang, Kaier & Steyn-Ross, Moira & Steyn-Ross, D & Wilson, Marcus & Sleigh, Jamie. (2014). EEG slow-wave coherence changes in propofol-induced general anesthesia: Experiment and theory. Frontiers in systems neuroscience. 8. 215. 10.3389/fnsys.2014.00215.

 

Theta waves appear in states of drowsiness, the early phases of sleep, light sleep, or during deep meditation (3).  Brain patterns during sleep are actually quite complex as your brainwaves will be in different wavelengths depending on the stage that you are in.  

There are 2 types of sleep (non-REM and REM) and in total, there are 4 stages in the sleep cycle.  Every night we cycle through each of these stages for varying lengths of time, and during each stage there are more dominant patterns of electrical and chemical activity that correlate with certain wavelengths and frequencies. These are the 4 stages of sleep:

  • Non-REM (NREM) Stage 1 
  • Non-REM (NREM) Stage 2
  • Non-REM (NREM) Stage 3
  • REM

NREM Stage 1 sleep usually only lasts for a few minutes as you gradually start to drift into sleep.  Brain waves slow down from active beta waves to the more relaxed alpha and theta waves (5).  In stage 1 NREM sleep, brainwave patterns are similar to people who are awake but very relaxed. 

The appearance of short bursts of electrical activity in the brain (called sleep spindles and K complexes) characterizes Stage 2 non-REM sleep.  Theta waves mixed with sleep spindles and K complexes are common in Stage 2.  Most of your total nocturnal sleep time is spent in stage 2, and this is where your body starts to relax more, your breath rate drops, heart rate drops, eye movements cease, and your sleep starts to get deeper (6).  

Stage 3 NREM sleep is where deep sleep occurs.  Low-frequency delta waves dominate here and it is more difficult to wake someone when they are in this stage.  Usually, when someone says that they don’t feel rested upon waking, it’s indicative that the quality of their stage 3 sleep is poor.

Brainwaves during REM sleep on the other hand more closely resemble that of a person who is awake.  Heart rate and breath rate become quicker and your eyes move rapidly while closed (REM = rapid eye movement).  Most dreaming also occurs during REM sleep and people report recalling more vivid dreams during this phase (6).  

consciousness

Measuring Consciousness Using fMRI Imaging

We often are not consciously aware of when we switch from one brainwave pattern to another, but there are measurable changes in the brain that occur that can be shown using EEG measurements and fMRI brain imaging.  Dr. Jacobo Sitt of the Institute of Brain and Spinal Cord in Paris, argues that EEG measurements do not provide good spatial information about brain activity compared to fMRI imaging. 

In February of 2019, Sitt and colleagues performed fMRI brain scans on 159 participants scanned at four independent research sites.  The participants were divided in two categories: 47 healthy individuals and 78 patients who either had unresponsive wakefulness syndrome (UWS) —a vegetative state in which the patient’s eyes open, but they never exhibit voluntary movement—or were in a minimally conscious state (MCS)—having more complex behaviours, such as the ability to follow an object with their eyes, but remaining unable to communicate thoughts or feelings.

Data from the fMRI scans, which generated roughly 400 images in approximately 20 minutes for each patient, was computationally analyzed for 4 different identifiable patterns of activity.  The patterns revealed diverse interareal coordination, from positive/negative long-range coherence (pattern 1), to predominantly occipital coherence (pattern 2), to overall high coherence (pattern 3), and overall low coherence (pattern 4).

Overall they found that healthy individuals were more likely to display pattern 1—characterized by high spatial complexity and interregional connectivity indicating brain-wide coordination. Unresponsive patients with UWS most often displayed pattern 4—characterized by low complexity and reduced interregional connectivity.

consciousness, guided meditation
Brain activity pattern 1 (left) and 4 (right) identified within fMRI data. E. TAGLIAZUCCHI & A. DEMERTZI

On Consciousness and Dreams…

Often when discussing consciousness, the question of why we dream and what dreams mean is debated. These discussions have been around for centuries—most popularly, Sigmund Freud’s and Carl Jung’s beliefs that dreams could be analyzed and interpreted to find hidden meanings or see what the “unconscious mind” consists of. 

More recently, sleep and dream research by Rosalind Cartwright has lead to conclusions that “dreams simply reflect life events important to the dreamer” (7). 

Some neuroscientists also believe that dreams play a functional role—they are similar to a state of “protoconsciousness” where we can get information that may be useful in states of wakefulness (7). 

In any case, it’s likely that as we gather more information on what consciousness is and how it correlates to what happens in the brain, our understanding of states of consciousness will shift as well.

In Conclusion:

If we haven’t lost you at this point, by now you would have gathered that consciousness and the study of consciousness is a complex and somewhat abstract arena.  Though there has been incredible research completed in the field to date, there is still a lot of room for new research in the realm of consciousness studies that can help us learn more about our amazing mind-body connection.

 

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Did you know Muse has a whole collection of meditations dedicated to sleep?

The Sleep Collection was designed to help you quiet your mind, release tension, and fall fast asleep. Wake up feeling well rested, full of energy, and ready to tackle whatever is on your schedule.

 

References: 

  • Walinga, J and Stangor, C. Introduction to Psychology 1st Canadian Edition. States of Consciousness. https://opentextbc.ca/introductiontopsychology/chapter/chapter-5-states-of-consciousness/ [Accessed 15 April 2020].
  • Koch, C and Greenfield, S. How Does Consciousness Happen? Scientific American [online] October 2007: 76-83. Available at: https://panet.andover.edu/bbcswebdav/institution/SCIE/SCIE/science%20490/Consciousness/how%20does%20consciousness%20happen.pdf
  • Yue, Carole. Khan Academy. States of Consciousness. https://www.khanacademy.org/science/health-and-medicine/executive-systems-of-the-brain/sleep-and-consciousness-lesson/v/sleep-and-consciousness [Accessed 15 April 2020]
  • Walinga, J and Stangor, C. Introduction to Psychology 1st Canadian Edition. Altering Consciousness Without Drugs. https://opentextbc.ca/introductiontopsychology/chapter/5-3-altering-consciousness-without-drugs/ [Accessed 21 April 2020]
  • Sleep.org: Understanding Sleep Cycles: What Happens While You Sleep https://www.sleep.org/articles/what-happens-during-sleep/
  • National Institute of Neurological Disorders and Stroke.  Brain Basics: Understanding Sleep https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep#2
  • Lumen Introduction to Psychology. Stages of Sleep  https://courses.lumenlearning.com/wsu-sandbox/chapter/stages-of-sleep/ [Accessed 22 April 2020]
  • A. Demertzi et al., “Human consciousness is supported by dynamic complex patterns of brain signal coordination,” Sci Adv, 5: eaat7603, 2019.

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