Monday, 3 March 2014

Bird Brained Science


It’s cliché to say science often involves boring and tedious work either in the lab and/or slaving over a computer screen.
But it does. Often.
Luckily, many of those with a passion for science also have a high tolerance for what is conventionally tedious. Fuelled by their subject, a scientist pushes through the boredom-burn like a nerd athlete.

With this romantic notion in mind, you can fully appreciate my first two days manipulating CT-scans of bird brains.

An example of CT scanning, in this case a hummingbird,
family Trochilidae.
As I mentioned in my last blog, Dr Walsh’s work looks at the indents of bird brains inside their skulls to seek out patterns that correlate with how the bird flies. Is it a flapper, a diver, or a glider? Do birds that speedily manoeuvre, like swifts, have differently shaped brains from birds that soar, like vultures?

The CT Scanner takes 3142 projections of the skull to produce an x-ray image, but mapping the interior surface involves tracing the lines in three dimensions by hand-and-mouse. 
This is where my nerdy enthusiasm comes in.

The planes of our (scanned) brains.
Once you’ve traced the outlines in several slices in the axial, sagittal and coronal planes (see pic), you press the magic button and voila! The software creates the 3D brain based on what you mapped. 

Of course things are not so simple. I was given a thick-skulled woodpecker, family Picidae, and my mouse-manipulation went well, but the computer refused to create the brain for me. I spent the next two hours going through the images a few slices at a time to check and correct it for errors. 

By the end of the day I still had no brain. 

I fled, defeated, to the refuge of my hotel and consoled myself with edamame beans and vegan puddings, washed down with fruity Kopperberg. As I ate I pondered: why does it matter if an avian brain-print relates to how it flies?

It’s not just bird-brained curiosity. These patterns in the noggin are called cerebrotypes, and they’ve already been found in mammals, amphibians and fish. Only in the last ten years have people started looking for them in birds. If there are cerebrotypes for birds linked with their flight, we could use this to look at extinct birds and flying dinosaurs and infer how they might have behaved millions of years ago. It would help build a picture of the evolution of flight. 

Scans of bird brains from the Walsh et al (2013) study on bird brain
size. The wulst is the ridge on the top of the brains.
For Dr Walsh, one of the world’s leading palaeo-neurologists, the shape of one part in particular, the eminentia sagittalis or ‘wulst’ is of special interest. This bump on the top of the brain varies among living birds, but seems to be absent in species that didn’t make it through the massive K-T extinction event at the end of the age of dinosaurs.

 Could the wulst be linked with behaviour that helped those early birds to survive where others perished?

A second day at the pixel (or voxel) grind-stone and I had more luck. I mapped an oystercatcher brain and began the process of tidying the image up, then re-mapped the woodpecker. Success! A neat little blob emerged, wulst and all.

Dr Walsh needs at least sixty skulls to start statistically analysing them for cerebrotypes, so there’s plenty for me to do. I’m back in the Highlands for two weeks of normal life, then I’ll return south again to play with bird brains at the museum, helping to expand the boundaries of avian palaeo-neurology!