Brain States

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What Can Dreams Tell Us About Consciousness?

893666_45846960To understand the nature of consciousness is perhaps the holy grail of neuroscience, not to mention philosophy and psychology. Although we are a long way off from that goal, current studies can give us some insight into our own awareness by examining and manipulating the brain during lucid dreaming.

In lucid dreaming, the dreamer is aware that he or she is dreaming while the dream continues. Lucid dreaming is also associated with several other dream states, including being able to control the dream or taking on a third person perspective. The dreamer may experience dream events,  but also have access to waking memories.

Scientists have reported that the brains of people who are in a state of lucid dreaming exhibit a phenomenon known as phase synchrony. This means that the neurons in the brain are synchronizing with each other and firing with a particular common frequency. Oscillations (or colloquially, waves) of certain frequencies are grouped together and named with greek letters, and different frequencies correspond with different states. For example, the characteristic frequency for a state of relaxed wakefulness is in the alpha band of about 8-13 Hz.  During lucid dreaming, there is an increase in the gamma band of frequencies, corresponding to about 40 Hz. This increase happens especially in the frontal an temporal lobes of the brain.

For many years, scientists have wondered whether these synchronized brain waves are a cause of the self-awareness in lucid dreams, or a consequence.  A new study out this week, spearheaded by neuroscientist Ursula Voss, sought to address this question by passing alternating current at a variety of frequencies between two electrodes placed on the surface of the scalp. Voss and her team waited until their human volunteers were dreaming in a state of REM sleep for at least two minutes before starting to apply the current, which they hoped would entrain the neurons in the brain to the same frequency as they used for stimulation. After stimulating for 30 seconds, they woke the dreamers up and asked them questions about their dreams.

When the scientists stimulated the brain with a 25 or a 40 Hz current, similar to what is observed in gamma waves, the subjects reported an increase in lucidity compared to other stimulation frequencies. Here is how one subject described it:

“I was dreaming about lemon cake. It looked translucent, but then again, it didn’t. It was a bit like in an animated movie, like the Simpsons. And then I started falling and the scenery changed and I was talking to Matthias Schweighöfer (a German actor) and 2 foreign exchange students. And I was wondering about the actor and they told me ‘yes, you met him before,’ so then I realized ‘oops, you are dreaming.’ I mean, while I was dreaming! So strange!”

This study represents a huge moment for neuroscience, because it is the first report that transcranial stimulation is capable of causing an alteration in conscious awareness. Moreover, this study suggest that brainwaves of the 40Hz band are not simply a feature of higher cognitive functions, but can actually cause them. Strange indeed.

Reference: Induction of self awareness in dreams through frontal low current stimulation of gamma activity. (2014) Ursula Voss, Romain Holzmann, Allan Hobson, Walter Paulus, Judith Koppehele-Gossel, Ansgar Klimke & Michael A Nitsche. Nature Neuroscience. 


When We’re In Sync, So Are Our Brains

We all know those moments. The electrifying seconds when the home team makes a goal, or bride says her vows, or the presidential favorite wins the election. The moments when an entire room full of people is feeling exactly the same way, at exactly the same time, because they share a common perspective.

The emotion runs high because everyone is riding the same roller coaster of events, each new twist and turn causing fresh reactions.   Our emotions are jerked like rag dolls.  The result looks so synchronized, it could be choreographed.

When we are all cheering for the same goal, both our bodies and our minds become synchronized.  You throw your hands up at the same time as the rest of the stadium, and your brains are also doing the same thing. In each head, the visual cortex is processing the game, the motor cortex is holding up the arms, and the attention-controlling networks are riveting us all to the events as they unfold.

And when you are rooting for the same person, the Action-Observation Network in the frontoparietal region of starts humming in synchrony with those around you.  In fact, it is this neural synchrony that allows you to share a moment with others.

That’s the implication of a study released in the Journal of Neuroscience. In it, scientists measured the blood flow to the brains of people who were watching a boxing match. In some cases, the scientists told the subjects to watch the match as they normally would. But sometimes they told the subjects to watch the match while paying close attention to a particular boxer, trying hard to simulate in their own minds the actions and emotions of that boxer.

When different subjects focused on the same boxer, their brains began to oscillate in phase with one another in the somatosensory cortex- the part of the brain that is responsible for the sense of touch. The somatosensory cortex also plays a big role in allowing you to mentally “mirror” the actions of another person, so that you can monitor them and understand their motivations.

Importantly, the brain synchrony was bigger when the subjects were paying attention to the same boxer than when the subjects were just watching the video casually. It’s the attention to the actions and feelings of another that caused the brain regions to activate – because in large part, the brain uses the same area to understand the way someone else is feeling as to feel that way itself. 

This report is one in a long line of evidence suggesting that time-locked brain activity shared by individuals is the basic process that supports interpersonal understanding.

Just think. All our moments of mutual understanding may depend on our brains being in sync with one another.


Nummenmaa L, Smirnov D, Lahnakoski JM, Glerean E, Jääskeläinen IP, Sams M, Hari R (2014) Mental action simulation synchronizes action-observation circuits across individuals. J Neurosci 34:748–757.