How the brain produces consciousness in 'time slices'

April 12, 2016, Ecole Polytechnique Federale de Lausanne
Credit: Human Brain Project

EPFL scientists propose a new way of understanding of how the brain processes unconscious information into our consciousness. According to the model, consciousness arises only in time intervals of up to 400 milliseconds, with gaps of unconsciousness in between.

The driver ahead suddenly stops, and you find yourself stomping on your breaks before you even realize what is going on. We would call this a reflex, but the underlying reality is much more complex, forming a debate that goes back centuries: Is consciousness a constant, uninterrupted stream or a series of discrete bits - like the 24 frames-per-second of a movie reel? Scientists from EPFL and the universities of Ulm and Zurich, now put forward a of how the unconscious information, suggesting that consciousness arises only in intervals up to 400 milliseconds, with no consciousness in between. The work is published in PLOS Biology.

Continuous or discrete?

Consciousness seems to work as continuous stream: one image or sound or smell or touch smoothly follows the other, providing us with a continuous image of the world around us. As far as we are concerned, it seems that is continuously translated into conscious perception: we see objects move smoothly, we hear sounds continuously, and we smell and feel without interruption. However, another school of thought argues that our brain collects sensory information only at discrete time-points, like a camera taking snapshots. Even though there is a growing body of evidence against "continuous" consciousness, it also looks like that the "discrete" theory of snapshots is too simple to be true.

A two-stage model

Michael Herzog at EPFL, working with Frank Scharnowski at the University of Zurich, have now developed a new paradigm, or "conceptual framework", of how consciousness might actually work. They did this by reviewing data from previously published psychological and behavioral experiments that aim to determine if consciousness is continuous or discrete. Such experiments can involve showing a person two images in rapid succession and asking them to distinguish between them while monitoring their brain activity.

The new model proposes a two-stage processing of information. First comes the unconscious stage: The brain processes specific features of objects, e.g. color or shape, and analyzes them quasi-continuously and unconsciously with a very high time-resolution. However, the model suggests that there is no perception of time during this unconscious processing. Even time features, such as duration or color change, are not perceived during this period. Instead, the brain represents its duration as a kind of "number", just as it does for color and shape.

Then comes the conscious stage: Unconscious processing is completed, and the brain simultaneously renders all the features conscious. This produces the final "picture", which the brain finally presents to our consciousness, making us aware of the stimulus.

The whole process, from stimulus to , can last up to 400 milliseconds, which is a considerable delay from a physiological point of view. "The reason is that the brain wants to give you the best, clearest information it can, and this demands a substantial amount of time," explains Michael Herzog. "There is no advantage in making you aware of its unconscious processing, because that would be immensely confusing." This model focuses on visual perception, but the time delay might be different for other sensory information, e.g. auditory or olfactory.

This is the first two-stage model of how consciousness arises, and it provides a more complete picture of how the brain manages than the "continuous versus discrete" debate envisages. But it especially provides useful insights about the way the processes time and relates it to our perception of the world.

Explore further: Brain study suggests consciousness a matter of optimal degree of connectedness in neural network

More information: Michael H. Herzog et al. Time Slices: What Is the Duration of a Percept?, PLOS Biology (2016). DOI: 10.1371/journal.pbio.1002433

Related Stories

Brain study suggests consciousness a matter of optimal degree of connectedness in neural network

January 27, 2016
(Medical Xpress)—A team of European researchers has found evidence that suggests that human consciousness is a state where the neural network that makes up the brain operates at an optimal degree of connectedness. In their ...

What makes us conscious?

March 16, 2016
Do you think that the machine you are reading this story on, right now, has a feeling of "what it is like" to be in its state?

Neural activity in the brain is harder to disrupt when we are aware of it

October 22, 2013
We consciously perceive just a small part of the information processed in the brain – but which information in the brain remains unconscious and which reaches our consciousness remains a mystery. However, neuroscientists ...

Researchers advocate for more scientific research on consciousness

July 10, 2014
Why does a relentless stream of subjective experiences normally fill your mind? Maybe that's just one of those mysteries that will always elude us.

At least two regions of the brain decide what we perceive

September 25, 2014
People have never been exposed to as many sensory stimuli as they are today. We do not, however, consciously perceive the majority of the sensory impressions that bombard us. Our brain processes these impressions without ...

Consciousness has less control than believed, according to new theory

June 23, 2015
Consciousness—the internal dialogue that seems to govern one's thoughts and actions—is far less powerful than people believe, serving as a passive conduit rather than an active force that exerts control, according to ...

Recommended for you

Perinatal hypoxia associated with long-term cerebellar learning deficits and Purkinje cell misfiring

August 18, 2018
Oxygen deprivation associated with preterm birth leaves telltale signs on the brains of newborns in the form of alterations to cerebellar white matter at the cellular and the physiological levels. Now, an experimental model ...

CRISPR technology targets mood-boosting receptors in brain

August 17, 2018
An estimated 13 percent of Americans take antidepressant drugs for depression, anxiety, chronic pain or sleep problems. For the 14 million Americans who have clinical depression, roughly one third don't find relief with antidepressants.

People are more honest when using a foreign tongue, research finds

August 17, 2018
New UChicago-led research suggests that someone who speaks in a foreign language is probably more credible than the average native speaker.

Critical role of DHA on foetal brain development revealed

August 17, 2018
Duke-NUS researchers have found evidence that a natural form of Docosahexaenoic Acid (DHA) made by the liver called Lyso-Phosphatidyl-Choline (LPC-DHA), is critical for normal foetal and infant brain development, and that ...

Automated detection of focal epileptic seizures in a sentinel area of the human brain

August 17, 2018
Patients with focal epilepsy that does not respond to medications badly need alternative treatments.

Men and women show surprising differences in seeing motion

August 16, 2018
Researchers reporting in the journal Current Biology on August 16 have found an unexpected difference between men and women. On average, their studies show, men pick up on visual motion significantly faster than women do.


Adjust slider to filter visible comments by rank

Display comments: newest first

Apr 12, 2016
This comment has been removed by a moderator.
not rated yet Apr 12, 2016
This produces the final "picture", which the brain finally presents to our consciousness

This is called the homunculus argument or 'infinite regress'. It assumes that consciousness is a separate entity of function in the brain and that perception is presented to consciousness in what is called the 'Cartesian Theatre'.

In reality the 'theatre' is the world we sense. there is no reason whatsoever to repeat the theatre at successive stages as if there is a viewer deeper in the brain.

The earliest visual processing area receives around 10 times as many synapses from higher brain areas than from the retina indicating that integration, not separation, is the theme of brain function.
not rated yet Apr 13, 2016
this title is showing complete misunderstanding of he subject

How the brain produces consciousness in 'time slices'

1. Universe is NOW
2. Fundamental time in the universe has only mathematical existence.
3. Emergent time as duration has origin in the measurement of the observer. No measurement no duration.
4. Observer has origin in consciousness.
not rated yet Apr 13, 2016
This has been known for some time concerning visual stimulus. The retina is said to record about 40 images per second. The brain needs constant change or it will ignore whatever is continuous. Eyesight would just go black if it were continuous.

The brain is what's real. It creates consciousness, which is a fantasy, for its own purposes, namely survival and reproduction. The brain can't go to the grocery store or chat up the opposite sex!
not rated yet Apr 14, 2016
Discussion on issues of consciousness with a more academic flavour (though everyone is allowed to contribute) at the 'Consciousness Studies' group. It also includes links to relevant news items, like this one :)

not rated yet Apr 14, 2016
It would be interesting to see if the delay in perception is constant during duress. It would be a logical conclusion that stressful situations would decrease the duration. This would explain the perceived slowing of time people say they experience during certain stressful events that include fast paced stimulus. It would also be logical that the memory detail of such events are very focused or narrow as the brains storage has trouble keeping up, thus blocking out unnecessary details.
5 / 5 (1) Apr 16, 2016
"stomping on your breaks"
When someone stops in front of there is no time to go dancing!
not rated yet Apr 18, 2016
yeah, some semantic issues in article. Better when they said 'conscious perception'.
It doesn't seem that sensory input is needed for consciousness (though it helps confirm it for us lol). And the article itself admits that different senses have different time delays. It seems a clumsy attempt to oversimplify a much more complex and interesting thing. We certainly seems to perceive things continuously and the article did a poor job of explaining how we may not do that. A delay time doesn't necessarily imply or deny discreet units. I wish article actual gave me a clue what it is trying to say. We sense many things continuously. If there is the tiniest gap in many continuous things we can detect it. (much tinier than 400ms). So I guess that's not what they are talking about. See how clear they are?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.