In this Direct Pathway and Indirect Pathway. If components of that is being damaged, we have diseases and you can imagine we have movement disorders. The two typical ones are simply, Parkinson's Disease and Huntington's Disease. In Huntington's disease, the neurons in the striata, they die. Those neurons are called the medium spiny neurons, and those are GABAergic projection neurons. By the way the GABAergic neurons I'm discussing here, they are not local interneurons, they are not. Local interneurons are GABAergic, but we are talking about here, they are the GABAergic long distance, projection neurons. Okay, so there is a big difference. Now, somehow, for a reason we still don't quite understand, in Huntingdon's Disease, not everybody in striatum dies at the same time. To begin with, it's the subgroup of GABAergic neurons that are positive. Those types of neurons dysfunction first and then they die first. Therefore, whereas the direct pathway is affected in a minor way, indirect pathway has a major, major dysfunction in cell death. So the imbalance goes this way. When I draw the straight line down from striatum to GPE, you can see that I changed the arrow to a dashed line arrow, meaning it's weakened. It's weak. So the reduction of innovation to GPE, makes GPE less inhibited, right? So the GPE now works much, much more efficiently. It sends our signal to STN. To illustrate that change, see, I put three red arrows instead of one, because it sends a lot more signals, right? When GP acts so much more on STN. But interestingly, GP is an inhibitory neuron. So it inhibits STN a lot more. As a result, STN firing, which goes to GPI, is going to be reduced. Therefore, I drew in a way that STN goes to GPI. It's now no longer a solid arrow. Instead, it's a dashed arrow, because it's weaker. When you have weaker sort of excitation to GPI and a net output to the other side what will be strong, right? So, I'm sorry. So there will be less inhibition from GPi to thalamus. Therefore, if you are a neuron in thalamus, you receive much less inhibition. As a result, you are much easier to get excited. So thalamus neurons, now the output becomes three solid, straight white arrows. And then, you have this recurring, recurring, easy to excite, hard to diminish. And you can see, I will show you the HD patients movie in a minute, that the net result is those patients, they cannot inhibit their actions.