Remembering the future: Our brain saves energy by predicting what it will see

March 24, 2010, University of Glasgow

Modern human brain
Modern human brain. Credit: Univ. of Wisconsin-Madison Brain Collection.
(PhysOrg.com) -- Researchers have discovered that the brain saves energy by predicting what it is likely to see. According to scientists in the Department of Psychology at the University of Glasgow in collaboration with the Max-Planck Institute for Brain Research, Frankfurt, Germany, the visual cortex does not simply react to visual stimuli but proactively predicts what it is likely to see in any given context - for example, within familiar environments such as your house or office.

By doing so it uses less energy to process images, but if something unexpected were to appear in that familiar environment, the becomes more active in order to process this information.

“Imagine your desk in your office,” said lead researcher Dr Lars Muckli. ”You’ve seen it a million times so your knows what it looks like so it doesn’t need to spend lots of time processing the scene. It already has a mental image of it and so the brain predicts that this is what it will see before you walk into the room.

“However, if you were to walk in to your office one day and see someone totally unexpected sitting in your chair - the Prime Minister, for example, your brain would have to work harder to process the same scene.”

The findings build on a fairly new hypothesis developed by University College London neuroscientist Karl Friston called predictive coding - or free energy principle - which suggests the brain is actively predicting what input it will receive, rather than just passively processing information as it arrives.

Dr Muckli said: “By predictive coding we refer to the idea that the brain generates predictions that estimate the visual input it will most likely receive given the contextual information from the recent past. For the brain it’s really about surprise reduction.”

To test the predictive coding hypothesis, the Glasgow researchers conducted an experiment where 12 volunteer subjects were asked to view a visual stimulus while undergoing and fMRI brain scan.

The subjects had to look at a fixed point on a computer screen above and below which two dots would flash alternatively creating an illusion of motion.

For predictable/unpredictable trials, the researchers briefly presented a third dot on the screen. To test predictable stimulus the dot would appear at a point between the two other dots, timed to correlate to the illusion of smooth movement. For the unpredictable stimulus it would appear out of synch with the motion illusion.

The primary visual cortex (V1) of each subject was monitored while the tests were undertaken and the results showed that the predictable patterns resulted in less activity in V1, compared to the unpredictable stimulus.

Dr Muckli said: “The brain expects to see things and really just wants confirm it now and again - it’s almost like remembering the future.

“It might explain why sometimes you don’t notice something different in a familiar environment because your brain is seeing what it expects to see, rather than what is actually there.

“What we need to do now is extend this research to consider predictive coding in more natural environments and other aspects of sensory perception.”

The paper, ‘Stimulus Predictability Reduces Responses in Primary Visual Cortex’, was published in the Journal of Neuroscience.

More information: Stimulus Predictability Reduces Responses in Primary Visual Cortex, The Journal of Neuroscience, February 24, 2010, 30(8):2960-2966; doi:10.1523/JNEUROSCI.3730-10.2010

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10 comments

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ArtflDgr
not rated yet Mar 24, 2010
Given that there is a lag between perception,cognition, and result... the brain has to think ahead just to function as close to now as possible or else we would always be behind things reacting (its called instinct)
GlenM
5 / 5 (3) Mar 24, 2010
The real goal of this predicting is to establish a novelty gradient. Thereby only the differences between prediction and actuality get encoded. The energy savings comes from not having to encode and then reconciled through neighbourhood reduction.
cakmn
5 / 5 (4) Mar 24, 2010
I wonder if it is this energy saving 'laziness' of the brain that sometimes keeps us from seeing something we are looking for, even if it is right in front of us, because the brain thinks it 'knows' it's not there because it usually isn't? Young kids seem especially prone to this sort of seeming 'blindness'.
kasen
5 / 5 (1) Mar 24, 2010
Would it be wrong, then, to suggest that most feelings of deja vu should be the result of these previews exceeding some cognitive threshold? Maybe if the prediction is too lengthy, or processed too slowly, it leads to a sort of buffer overflow, which activates long term memory.
NonRational
not rated yet Mar 24, 2010
Are schizophrenics, who hallucinate often to seemingly "predict" what the present is like instead of actually sensing what it really is, victims of a lazy brain?
freydawg56
5 / 5 (1) Mar 24, 2010
I think this could contribute to why we become better readers. Our brains slowly memorize words as we see them over and over and instead of reading for words, our brains use energy on picturing what we are reading and processing the main idea, not the individual words. Anyone agree/disagree ??
Aliensarethere
not rated yet Mar 24, 2010
This is Jeff Hawkins theory, called memory-prediction framework. He wrote a book "On intelligence" in 2004.
blento
1 / 5 (1) Mar 24, 2010
I think this could contribute to why we become better readers. Our brains slowly memorize words as we see them over and over and instead of reading for words, our brains use energy on picturing what we are reading and processing the main idea, not the individual words. Anyone agree/disagree ??

Totally agree! I've seen it time and time when my employees read a text and assume the point without ever finishing the sentence. After I asked them to read it again slower, they all get it slowly, aaaaaaaa!! This article makes a point we all new for quite some time. Nothing new.
dferrantino
4 / 5 (1) Mar 25, 2010
I think this could contribute to why we become better readers. Our brains slowly memorize words as we see them over and over and instead of reading for words, our brains use energy on picturing what we are reading and processing the main idea, not the individual words. Anyone agree/disagree ??

I'm not sure, but I think this has already been proven. For language especially, our brains anticipate what we expect to see or hear before we actually do, and will often skip typos entirely. However, once you notice it, it sticks out like a sore thumb.
visvivalaw
not rated yet Mar 26, 2010
This is nothing new. Jeff Hawkins talked about this idea in great detail in "On Intelligence" years ago.

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