Nelson – research tools

 We use a number of tools in my lab to study brain development in infants and human children. When children are less than five or six years of age we primarily focus on recording the brain’s electrical activity. And the way we do that is we place little sensing devices over the surface of the scalp. We can do that with a little cap or a net. And essentially what we’re doing is recording the electrical activity that occurs between each neighboring neuron or brain cell, that then moves or propagates to the scalp surface where we place these sensors.  And that tells us something about the moment by moment transactions that are going on in the brain during the time a baby or a young child is thinking. So the event related potential really is a fancy name for saying what is the brain’s response to a stimulus presented repeatedly.  

So if I flash a picture of my face or somebody’s face, or a somebody’s face, or a sound over and over again, each time you see that face or hear that sound I trigger or illicit a response from your brain, and that’s really what the event related potential is. 

In some places they often refer to this as the evoke potential, which is another name for it. And, so there what’s happening is that if you imagine the brain has background electrical activity, which everyone knows as the EEG. If this is the background electrical activity, if I present a face here and then here and then here, suddenly there’ll be a little blip in that background electrical activity and if I repeat it enough times, when I average those episodes together, I will wind up with a waveform that shows a series of positive and negative deflections, in this ongoing EEG, and that’s the event related potential. And we think that each of these deflections reflects a unique and separate psychological function and neural function as well. 

So for example, a component, we label these deflections as components, that occurs at 200 milliseconds after the stimulus has come on, probably reflects some aspect of attention. So that’s what the event related potential is. And it gives us millisecond by millisecond resolution of what’s going on in the brain. And it also gives us a crude approximation of where those events are going on. Now when children reach the age of five or six, we can also start to do magnetic resonance image scanning on them, specifically functional magnetic resonance imaging. And the reason we have to wait is simply that kids are too prone to wiggling around before they’re five or six. Even five or six is pushing it sometimes. 

So here the child lies in a tunnel. Many people have seen what these MRI scanners look like. And while they’re in this tunnel we’re presenting pictures or sounds to them and we’re asking them to do something, such as show us what they remember by pushing a button. The only constraint is that you have to lie very, very still. We can’t tolerate more than a millimetre of movement. So a younger child, even though they think they’re sitting still or lying still, in fact is probably moving a little bit. So in our experience, once kids get to be around six, they’re more likely to be able to sit still for ten or fifteen minutes at a time. Actually testing children in this is much easier than testing adults. Children as a rule are never claustrophobic, they kind of like being in that. If you go to playgrounds nowadays, you’ll notice there are lots of little narrow tunnels that the kids play in. So they’re kind of used to that.