Brain oscillations reveal that our senses do not experience the world continuously

May 14, 2012

(Medical Xpress) -- It has long been suspected that humans do not experience the world continuously, but rather in rapid snapshots.

Now, researchers at the University of Glasgow have demonstrated this is indeed the case. Just as the body goes through a 24-hour sleep-wake cycle controlled by a , function undergoes such cyclic activity – albeit at a much faster rate.

Professor Gregor Thut of the Institute of Neuroscience and Psychology, said: “Rhythms are intrinsic to biological systems. The circadian rhythm, with its very slow periodicity of and wake cycles every 24 hours has an obvious, periodic effect on bodily functions.

“Brain oscillations – the recurrent neural activity that we see in the brain – also show periodicity but cycle at much faster speeds. What we wanted to know was whether brain function was affected in a cyclic manner by these rapid oscillations.”

The researchers studied a prominent brain rhythm associated with visual cortex functioning that cycles at a rate of 10 times per second (10Hz).

They used a ‘simple trick’ to affect the oscillations of this rhythm which involved presenting a brief sound to ‘reset’ the oscillation.

Testing subsequent visual perception, by using transcranial magnetic stimulation of the visual cortex, revealed a cyclic pattern at the very rapid rate of brain , in time with the underlying brainwaves.

Prof Thut said: “Rhythmicity therefore is indeed omnipresent not only in brain activity but also . For perception, this means that despite experiencing the world as a continuum, we do not sample our world continuously but in discrete snapshots determined by the cycles of brain rhythms.”

The research, ‘Sounds reset rhythms of and corresponding human visual perception’ is published in the journal Current Biology.

Explore further: Remembrance of things future: Long-term memory sets the stage for visual perception

More information: Romei et al., Sounds Reset Rhythms of Visual Cortex and Corresponding Human Visual Perception, Current Biology (2012), doi:10.1016/j.cub.2012.03.025

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not rated yet May 14, 2012
Now that IS interesting.

Explains why we roughly need 20 images per second to see movies instead of a series of stills (Nyquist-Shannon sampling theorem). I bet this could be used to further increase the efficiency of compression algorithms that are based on psychological effects (such as mp3 which is based on psychoacoustics).
not rated yet May 14, 2012
Anyone who has ever experienced "tracking" (seeing a series of fading shadows behind a moving hand, for example) already knows that the perception is not continuous. IMHO, the more important aspect of this is what is going on in the periods where no perception is taking place.
not rated yet May 14, 2012
Nice connection with the Nyquist theorem. Watching a video at less than 20 fps, we would perceive aliasing as moments in time between frames where the video doesn't change.
I heard somewhere that cinemas are upping the standard framerate from 24 to 48 fps because these 3D films are known to give people headaches, seems a bit overkill and they should consider tuning the frame rate to our visual cortex rhythm, assuming they are the same for everyone, otherwise the person viewing would need some occipital transcranial magnetic stimulation first and have algorhythms compress the video based on information gained from an individuals brain.
not rated yet May 14, 2012
The visual system of the human brain can indeed interpret frame rates up to 60 fps. As a gamer, I can tell the difference. Most of you should be able, too.

Use this site and see for yourself:
1 / 5 (1) May 14, 2012
Obviously we have to see in frames for the same reason movies are frames, as continuous reception would just blur the picture, like a long exposure photo. The frame rate is likely a result of perceiving biological activity, such as hunting moving game, or avoiding same. I suspect raptors probably have a faster rate.
not rated yet May 14, 2012
Aphexcoil, there is a fundamental difference between film and pure digital medium. I have the same experience myself as a gamer, and the difference is simple.

Film is an exposure, that captures blurring of motion. When it is filmed, it captures the scene X times a second, but motion during that will blur across each frame. In a digital medium, each frame is purely static, no motion blurring, so differences in position between frames is much easier to perceive.
1 / 5 (1) May 14, 2012
Hmmm. Discrete or continuous. We are blessed or doomed to do our best.
(To fill gaps that exist...or not.)
not rated yet May 14, 2012
Good research, but this should not come as a surprise. It should be a confirmation of conventional wisdom.

After all, computers and cameras all capture things a frame at a time.

The metaphyical reason is that it is the simplest way to preserve causality. If different parts of perception were not discretely linked and processed with a specific point of time, then it would be much more difficult to be a living human...we would have an even harder time making true connections between things in the physical world.

For example, have you ever seen a corrupted or badly coded youtube video where the motion updates while the color does not? You might see a figure walking around, yet he has the image/pattern of a ladder on a wall...
not rated yet May 14, 2012

so something or someone could be in the room with me and i would never see it?

i wonder what those black dots are that go zipping away from the corner of the room when i turn my head to look?

no, not the protein shadows floating on my corneas, the other things...
not rated yet May 16, 2012
I dunno EricB, how much had you been drinking? :-)

Seriously though, pretty much every aspect of cortical operation is cyclical. If you think about it this must be so because the different ingredients of perceptual quality and information content are mediated in different cortical areas which must mutually and reciprocally stimulate each other in order to create and maintain a networking event that properly represents/embodies the experience.

The most succinct explanation of consciousness you will come across is that C. is what it is like to be the process of updating of the model of self in the world within your brain. This model is a navigational device that allows us to locate ourselves within our physical and social environment.
1 / 5 (1) May 19, 2012
Many of the comments above do well in explaining why this result is necessary for the brain to operate. But there might be a more fundamental explanation: Planck's quantum. Energy is not continuous.
1 / 5 (1) May 20, 2012
Well stated Macksb, "energy is not continuous". Now, you people are finally getting yet another step closer to what you call "time travel". Please continue. As odd as it may seem, it's possible that your continued research may indeed add to our knowledge as well. Or, alter our existence. But, that is ok, because we scientists are searching for the ultimate truth, regardless of the implications thereof.
1 / 5 (1) May 20, 2012
I must add one more item. As of 1885, we examined the probability that some sort of alteration of what we think of as 'reality' could be possible, or not. Of course, now, we know it involves quantum processes within the brain. You can think of it as sort of an 'organized type of randomness' in a way, at the planck scale, yet, at the same time, at the macro scale. It's a difficult concept, but, that's how the mind functions, and, without an 'awareness' of this process to begin with, no such process of motivation can exist; Both as a singularity, and an infinity at the same time, and without any sort of discrete 'location'.

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