How the brain produces consciousness in 'time slices'

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
Journal information: PLoS Biology

Citation: How the brain produces consciousness in 'time slices' (2016, April 12) retrieved 17 October 2019 from
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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.

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.

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!

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 :)


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.

Apr 16, 2016
"stomping on your breaks"
When someone stops in front of there is no time to go dancing!

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?

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