The Corpus Callosum

The title of this post is taken from the title of a USC press
about a topic in neuroscience.  A guy at
USC named is studying the role of opioid ()
activity in visual perception.

Actually, the title of this post is misleading.  His research
is not about beauty.  Rather, it is about recognition,
salience and learning.  

In order to understand his theory, it helps to be able to see the brain
regions and pathways involved.  Fortunately, there is a nice
diagram here.
(Open the page, then click on the link by the little diagram in order
to see the enlarged diagram.  Ignore the warning about not
having access; the diagram will still open.)  

In a nutshell, what he found is that the areas of the brain that
process visual information contain mu-opioid receptors.  The
most posterior occipital regions have a relatively low density.
 That is where the visual information is first processed.

After the initial processing, the information is shuttled to successive
areas, moving anteriorly.  As the processing becomes more
sophisticated, the density of opioid receptors increases.  

The first areas take the information from the retina and figure out
simple things, such as shape and color.  There’s not very much
opioid activity there.  The next step in processing, is to
take the shape/color information and decipher that, to recognize
objects and places.  There is more opioid activity there.

Once the brain figures out what it is seeing, the next step is to
associate the images with memories.  That is where the brain
figures out what the images mean.  

Biederman’s hypothesis is that the release of these endogenous opioids
is somewhat pleasurable, and that we get more pleasure from looking at
things that we are able to place in some kind of meaningful context.

He extends this hypothesis, going on to speculate that the involvement
of opioid activity can explain why novel stimuli are more interesting
than overly-familiar ones.  

Biederman said this theory also explains our taste
for novelty and why conversely, familiarity breeds contempt. It rests
on an additional principle of brain organization called “competitive
learning” – the fact that as the cortex gets more familiar with
something, it uses fewer cells to “encode,” or represent it.

Something novel activates large swaths of the cortex, firing lots of
pleasure cells and making a strong bid for our awareness. But as we
experience the thing more, fewer cells are devoted to representing it.
This results in fewer pleasure cells firing and a consequent lessening
of its tug on our conscious attention.

Biederman’s theory has a number of other interesting ramifications,
such as why we find fast-cutting sequences on MTV and Sesame Street
pleasurable: So long as they aren’t incoherent, they up the rate at
which the association areas are getting stimulated.

So Beiderman’s hypothesis explains why some things look more
interesting than others.  Now, what I want to know is this:
why is neuroscience research more interesting than all other areas of


  1. #1 sftr
    June 22, 2006

    A few days ago, my bus had a sign on it that said, “If hepatitis C was attacking your face instead of your liver, you’d do something about it”. I think science is more interesting when it involves our concept of “who we are” as opposed to what is in us/around us. I know so many women over the age of 35 who can tell you all about their shrink and their depression/anxiety/etc. medications, but who can not tell you what their blood pressure or cholesterol levels are. I don’t know where I was going with this.

  2. #2 colleen
    June 22, 2006

    It’s quite interesting to be able to point to a mechanism responsible for the pleasure of novel sights. I’ve noticed seeing familiar objects in new locations, without design or aesthetic improvement, is refreshing. Novelty appears to be something we’re hardwired to enjoy… I wonder why that is?

    I’d venture neuroscience is exceedingly interesting because we realize that everything we know about the world is arrived at through our senses; to understand the rest of the world, and our limits on knowing, it helps to understand how human perception occurs. Plus, it seems the best way to understand our basic, irrational human nature; we have no access to what’s really going on behind the curtains, what drives us to react, feel, want, etc., so finding out thorough neuroscience has all the appeal of sneaking a verboten peek at what lies behind a mysterious curtain.

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