Introduction to Theta

Introduction to Theta Waves

Theta brain waves (4-8 Hz) are faster in frequency and lower in amplitude than Delta brain waves. Theta is the dominant frequency in lower mammals (e.g., bats, rats, dogs, and cats) and young children. For adults, cortical theta waves are prevalent in dream (REM) sleep, in the twilight state just before drifting off to sleep (Stage 1 sleep), and the first deep stage of non-REM (NREM) sleep (Stage 2 sleep). 

Theta waves are produced in the limbic system, a group of emotion-generating structures in the middle of the brain. Theta waves therefore link brain functions from the emotional limbic centers to higher brain regions like the neocortex and lower regions like the hypothalamus and brainstem. Theta is also generated in the hippocampus, which crucially depends on inputs from the medial septal area.

The Functions of the Theta Rhythm

There are three types of Theta.  Each has a distinct function and location. 

  1. Sleepy Theta is Theta that originates in the back of the brain and propagates throughout the whole cortex when falling asleep (Mitchell et al. 2008). When Theta is seen in the back and front of the brain in awake individuals, this is a strong signal of drowsiness and a need to rest. High Sleepy Theta (6-8 Hz) activity is seen during hypnosis and in dream states as well as in deeply relaxed states. Sleepy Theta acts as a gateway to the personal subconscious and therefore supports enhanced intuition, creativity, and deep psychic healing (Wise 2002). 
  1. Attention Theta, otherwise known as frontal midline Theta (FM Theta), is narrow band Theta that originates in the front and center of the brain. Attention Theta is produced by regions of the attentional network, including the anterior cingulate cortex (ACC) and prefrontal cortex (PFC). When one has a tight focus on an object of contemplation, the ACC and PFC put out Theta waves. According to EEG-fMRI combination studies, Attention Theta is inversely correlated with activity of the default mode network (DMN) (Scheeringa et al. 2008). This cluster of brain regions is active when we are engaged in mental time travel—that is, straying from the present moment and thinking about ourselves, the past, and the future. Therefore, with strong concentration on a given object, parts of the DMN deactivate and the attentional network comes online. Attention Theta is also correlated with the difficulty of the task being attended to. The harder the task (higher cognitive demand), the higher the amplitude of Attention Theta in the front of the brain (Sauseng et al. 2007). 
  1. Integration Theta is a global processing mode that ferries information around the brain in the form of Gamma bursts riding on top of Theta waves. The phase-coupling Gamma cycles superimposed on Theta oscillations support our working memory (Lisman 2010). Our memory capacity is limited by the number of Gamma cycles nested within a Theta cycle. 

Theta Waves and Meditation

Deep, profound meditative states come from Theta waves (Wise 2002). Researchers have observed enhanced Theta power correlating with positive experiences of bliss during meditation (Aftanas & Golocheikine 2001) and deep absorption states where the evaluating brain is suppressed (DeLosAngeles et al. 2016). Advanced Zen meditators show increased frontal Theta as their meditations progress and become deeper. Higher Theta activity compared to baseline in these meditators appears to reflect a heightened state of consciousness (Murata et al. 1994). 

An enduring finding across a wide array of meditation techniques is that Attention Theta power strongly correlates with the amount of training and experience in meditation (Pasquini et al. 2015, Kakumanu et al. 2018, Brandmeyer & Delorme 2016, Murata et al. 1994).

As Theta originates from limbic regions, it’s no surprise that Theta activity is closely involved in emotional processing and regulation. Loving Kindness meditators show increased Theta in the back of the brain, thus supporting the emotional role of the practice. Naturally, the largest Theta increases were seen in advanced (Levels 3 and 4) Loving Kindness meditators (Kakumanu et al. 2018).

High frontal Theta activity is a strong signal of attentional engagement. It is highest during Focus meditations where sustained attention is required, and lowest during meditations featuring open, detached awareness like Vipassana. Frontal midline Theta appears to contribute heavily to top-down attentional control, including maintaining focused attention, detecting errors (like mind wandering), and reorienting attention back to the breath. For this reason, beginning-to-intermediate meditators (Levels 1, 2, and 3) need lots of frontal Theta in order to tame their Monkey Mind. Open Monitoring (OM) meditators do not require the top-down control to support their detached, non-reactive stance to thoughts and emotions. This is particularly the case for advanced OM meditators whose meditations have taken the form of a well-ingrained bottom-up habit.

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