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MICHALE FEE: So today, we're going to introduce a new topic, which is related to the idea of fine-tuning curves, and that is the notion of receptive fields. So most of you have probably been, at least those of you who've taken 9.01 or 9.00 maybe, have been exposed to the idea of what a receptive field is. The idea is basically that in sensory systems neurons receive input from the sensory periphery, and neurons generally have some kind of sensory stimulus that causes them to spike. And so one of the classic examples of how to find receptive fields comes from the work of Huble and Wiesel. So I'll show you some movies made from early experiments of Huble-Wiesel where they are recording in the visual cortex of the cat. So they place a fine metal electrode into a primary visual cortex, and they present. So then they anesthetize the cat so the cat can't move. They open the eye, and the cat's now looking at a screen that looks like this, where they play a vi...

MICHALE FEE: OK, good morning. So far in class, we have been developing an equivalent circuit model of a neuron, and we have extended that model to understanding how action potentials are generated. And, more recently, we extended the model to understanding the propagation of signals in dendrites. So today we are going to consider how we can record activity, record electrical signals related to neural activity in the brain, and we're going to understand a little bit about how we can, in particular, record extracellular signals. So that will be the focus of today's lecture. So, so far in class, we have been analyzing measurements of electrical signals recorded inside of neurons. For example in the voltage clamp experiment, we imagined that we were placing electrodes inside of cells so that we could measure the voltage inside of this of cells. But it's actually quite difficult, in general, to record membrane potentials of neurons in behaving animals, although it...

MICHALE FEE: OK, so let's go ahead and get started. OK, so in the last lecture, we talked about how the inputs to neurons actually come into a cell mostly on the dendrite, which is this extended arborization of cylinders of cell membrane that give a very large surface area that allow many, many synapses to contact onto a neuron, many more than would be possible if all of those synapses were trying to connect to this neuron on its soma. Today, we are going to follow up on that general picture of how neurons receive inputs. And today, we're going to focus on the question of how synapses work. So we're going to start by looking at a simple model of synapses. And we're going to end by understanding how synapses on different parts of the neuron can actually do quite different things. So here's our list of learning objectives for today. So we're going to learn how to add a synapse to an equivalent circuit model. And we're going to describe a simple m...