Size does matter: Larger brains can hold more!

Size-mattersA long time ago in a galaxy far, far away, people didn’t have mobile phones to store their phone numbers in. People actually had to use their own memory to store these long numbers. But getting these numbers into long-term memory could be a real pain. People had to write the number down, say it over and over again to themselves and with each verbal iteration, something annoying would happen – the number would fade out of memory. To get the number into long-term memory you had to keep repeating the number, over and over again, fast enough to beat the fade away.

This short-term, fast fading memory is called working memory. It’s like the RAM in a computer: it holds everything in your mind ready for action, simulation or a decision. Working memory is related to our IQ and even to some mental disorders, but we don’t know why some people can fit a lot more information into their working memory than others. Yes, it’s very unfair. As I mentioned before in the post on extending your mind, some people can hold huge amounts of information in their mind and even manipulate it, trying out different ideas etc, while other brains or minds can only hold small amounts.

Why do you have the particular capacity you have? How can we investigate these differences between people? It turns out the key to answering these questions is to get people to remember information in only one of their 5 senses, such as vision. By doing this we narrow down the field of things to investigate and can look at the precise brain anatomy related to just that one sense in different people and figure out which parts of your brain allow greater information capacity.

14618772953_45f8cbf809_zThis is exactly what we did in a recent paper from my lab. We found that people with larger brains could hold more temporary information in their mind. Specifically, people with larger visual parts of their brains were the ones who could hold more visual information in their minds. This is interesting for a number of reasons. One reason is it suggests that the physical parameters of our brains set the limits to what we can do with non-physical things like the contents of our mind. In other words, the visual cortex is like a bucket: the larger the bucket the more water it can hold. The larger your visual cortex the more visual information you can hold in mind. With more information in mind, you can do… well, a lot more.

Visual working memory capacity is predicted by anatomical properties of V1.

Visual working memory capacity is predicted by anatomical properties of primary visual cortex.

But all this doesn’t make it any fairer for those that can’t hold much ‘in mind’. The next logical question is: Why do I have a large or small brain? Well, when it comes to visual cortex, data suggests that our genes play a role. The cortex, the outer layer of the brain, is a like a gooey grey sheet that is all wrinkled up on itself. In fact, there are two different components to the size or volume of the primary visual cortex: thickness and surface area. These two different measures seem unrelated to each other, but both have a heritable component. In other words, it seems that your parents or ancestors might have passed your visual cortex down to you, or at least it’s size.

So does all this come down to luck? Well, as with most things, yes and no. There is now some promising research looking at how training or practice can literally change the architecture of your brain.

The now famous book, The brain that changes itself is a great general read on the topic. However, there are many more specific research papers, investigating how practicing visual tasks can change not only your vision, but parts of your brain as well.


Here is the reference and link to our original paper:

Bergmann, J., Genç, E., Kohler, A., Singer, W.A. & Pearson, J. (2014). Neural anatomy of primary visual cortex limits visual working memory. Cerebral Cortex.

Want to know more about all of this? How to measure visual working memory or brain size? Let us know in the comments.


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