Neurones as computers

So here we have another drawing of a neurone, and in this video, we’re going to explore how it is that this neurone is influenced by its inputs in order to see how a single neurone may actually produce a variety of outputs. So we’ve already met the concept of the synapse, the point of input of information onto the dendrites. Now previously, we just saw one synaptic input, and it was the process here that we focused on. But the reality is that neurones, especially in your brain, don’t have one input, they will have hundreds, if not thousands. Now, what that means is, we have to think about how these thousands of inputs will influence the functioning of this cell.

So very simplistic, we can consider that this neurone is computing all of its inputs. Now, we’ve also met the idea that neurotransmitters are actually a quite diverse bunch of chemicals, and they can work in quite different ways. And we met the large distinction of them being either excitatory or inhibitory in terms of their effect on the postsynaptic membrane. So you can imagine then that if we were to think of these inputs as coming from entirely separate other cells, then what this cell is doing is to compute the input from cell A, cell B, cell C, and cell D.

So we can imagine the scenario where cell A and B were active or a different scenario where say, cell A and cell D weren’t active. And what that means is that what this cell will do will be determined by the combination of what its inputs are doing. Now, if you imagine scaling this up so we have a thousand inputs onto this cell, we immediately begin to see how the activity of this cell can be so very different depending on all its inputs.

If we scale that further to think of the billions of neurones in the brain, it is then beginning to become an understanding of how it is that all of these neurones work together to produce the complex and amazing functions that they do.