Professor Jeff Lichtman discusses temporal resolution, the ability to see changes across time, in relation to various neuroimaging technologies.

So we just talked about the spatial resolution of the brain. But there is another very important resolution question, which is related to seeing how the brain changes over time, and this could be called temporal resolution. If you think of the brain of a human baby it's very different from the brain of an adult. That brain changes over time that could be measured in years or maybe even decades, and if you look at an adult and a very old adult you still see changes in the way our brains work. And again these are changes that are going on very very slowly. There are very few techniques, but there are a few, but very few of them that actually allow us to track things over these very, very long times. Largely because over any short period you don’t see any change at all. It’s like staring at the hour hand of a clock. You watch it and watch it, it doesn’t seem to be moving but you come back a few hours later and sure enough it's moved but you never see it move, and this is the problem for us for the very long time scales. At the complete opposite end of the spectrum is the way nervous system cells function, in which they use electrical signals that pass from their cell bodies out to their processes – things called axons for example, and those processes are sending information at enormously fast speeds. A few thousandths of a second and a whole signal is over, a few milliseconds as they are called. There our problem is the same in that no techniques that we have that we can use in imaging show us those kinds of changes because our timescales are too crude to resolve those fine events. So we have a resolution problem both at the short end and at the very long end. Where microscopy is very good is for looking at resolution changes in the brain that are taking place over minutes or hours. There we can see for example the spines on dendrites. Dendrites are these processes that come off of neurons and they have these little pieces that come off of them that wiggle a little bit and change their shape sometimes with activity. Those changes are taking place over the course of minutes. Those we can see quite beautifully and of course because we can see them there’s a huge amount of interest in what we can see and we kind of leave the things that are hard to see for other times to do. For time-lapse imaging over weeks, or months, that requires taking a picture in an animal perhaps and then coming back a week later and finding the same place and taking another picture of the same area, and then coming back a week later and doing that again and again. People are just beginning to do that to see these very long lasting changes, but it is extraordinarily difficult to do that kind of work.

neuroimaging, temporal, resolution, time, timescales, brain changes, dendrites, spines, neurons, microscopy, jeff, lichtman