So I’ve already described how much I love being able to look at live, functional neurons in real time. But there are other things I enjoy seeing everyday too, in particular my favourite part of the brain; the hippocampus.
At the start of every patch clamp experiment, when I look down the microscope at a brain slice, I need to locate a specific structure before I can focus on finding individual neurons. This structure is called the hippocampus (so called because a cross section of it looks like a seahorse) and every brain has a pair of them (one in each hemisphere). The hippocampus is very special because it has a well-defined and distinctive structure, which makes it instantly recognisable to anyone who has studied neuroanatomy.
As I’ve said before, the brain is not a homogenous blob, but contains many intricate and beautiful structures. Many of these structures look pretty much the same across the majority of species, no matter what size or shape the brain may be, and the hippocampus is no exception.
Why do I love the hippocampus? Well, for one thing I love how ‘organised’ the anatomy is (I won’t go into detail here, but I do find the Wikipedia page extremely useful). The hippocampus is a network and I love how you can stimulate a particular pathway and get other neurons to fire in response (ie. stimulate the axons of the CA3 pyramidal neurons and the CA1 pyramidal neurons will produce a response). I also love the fact that it’s involved in lots of different aspects of learning and memory.
So, going back to the point about being able to stimulate pathways in the hippocampus, I also do a lot of experiments using multi-electrode arrays (MEAs). Being able to stimulate particular pathways and measuring evoked responses can tell you a lot about the synapse involved and the neurons on either side. For my experiments, I stimulate the Schaffer collaterals (axons of CA3 pyramidal neurons) and record the responses of the CA1 pyramidal neurons. Instead of observing signals from individual neurons, I look at the combined response of a whole population of neurons, which all fire in unison when stimulated by an extracellular electrode.
I’d love to go into more detail about MEA experiments, but I’ll save it for another post 🙂