I had the chance to attend a talk from Nobel Laureate Professor Bert Sakmann. The topic was From Single Cells and Single Columns to Cortical Networks.
A normal person makes about 1000 decisions every day. How do people go about making those decisions? He showed a painting called Gletscherspalte, which is German for crevasse, and the painting depicts two mountaineers crossing a glacier. They’ve hit a gap in the glacier and are trying to decide whether they can make the jump – a pretty important decision.
It’s pretty tough to get a bunch of people in laboratory conditions to measure their ability to decide whether to jump a gletscherspalte or not, so they used rats instead. What they did was create a platform with a gap between it, and try and look at how the rat decided whether it could make the jump or not. The first thing the rat does is lean over the gap and try to touch the other side with its whiskers. If it can’t touch it at all, then it doesn’t jump. If it can reach it, it touches it 5-10 times before deciding.
They worked out that when the whiskers made contact with the other platform, it would activate an area called the somatosensory cortex S1. (If you want to sound cool, you can try putting that in an every day sentence. (Well, that really depends on your definition of cool.)) The research team spent 10 years producing a replica S1 in silico (I thought that meant in silicon, but not quite, it does mean that, but it’s a term meaning they created a computer simulation). Each whisker maps to its own part of the cortical column, but interestingly, after 20ms, the areas around the activated cortical column also begin to show signs of activation (but not as strongly). If the areas for all other whiskers are becoming activated as well, how does the rat know which whisker was triggered?
I do remember him talking about how a whisker touch lasts about 45ms. They measured action potentials (AP), but not every touch seemed to evoke an AP. However, they broke the cortical column down into the individual cells, and found that the layer 5 thick tufted cells would have high-frequency bursts during the touch, which none of the other surrounding cells seemed to have, which may explain how the rat can tell which whisker is actually touching the platform.
How the rat goes from that to knowing whether not it can make the jump is beyond me.
The lecture was part of the Kenneth B. Myer series, which are a series of lectures sponsored by the Myer family, in honour of Kenneth Myer, who was actually one of the founding members of the Florey Institute of Neuroscience and Mental Health, which was the group that ran the event. The lecture itself went a bit over my head towards the end (hey, it’s been quite a long time since I’ve done any real psych stuff), but a lot of it was quite accessible.