Welcome to this presentation on the basal ganglia. The first thing that I would like you to make note
of is what are the major structures that constitute the basal ganglia. First, we have two structures
that collectively constitute the striatum. One of those members is the caudate nucleus that we see
here in the lateral aspect of the lateral ventricle. Then the second member of the striatum is
the putamen that you see labeled next on this image. Another member of the basal ganglia
would be the globus pallidus. It has two segments, an internal segment shown in through here
as well as an external segment or division shown here. I will now take you to another image to show
you yet another member of the basal ganglia. This is the substantia nigra, the black substance
that resides in the midbrain. You can see the substantia nigra right in through here as well as
over in through here on the opposite side. The last member of the basal ganglia is the subthalamic
nucleus. However, that is not shown. This is a great three dimensional image showing the
topographic relationships of the basal ganglia. The first thing to point out here is not a member
of the basal ganglia but the lateral ventricle. Here’s your lateral ventricle in through here,
coming down in through here and into the temporal area in through here. The basal ganglia that are
shown in this representation include the caudate nucleus. We can see its relationship then
to the putamen. And then lastly, we can see the relationship of these two structures to the
globus pallidus. Now, this takes us to a more complicated aspect of the basal ganglia.
This would be the intrinsic connections or the circuitry that exists between the components of
the basal ganglia as well as the thalamus and the cerebral cortex. So you see various brain
structures identified over in through here. So now, I will guide you through these connections.
First is the striatopallidal connection that we have between the members of the striatum
with the globus pallidus. These fibers are inhibitory as they are GABAergic. We also have a
pathway between the striatum and the substantia nigra. This is the striatonigral pathway.
We see that pathway extending from the striatum to the substantia nigra. That is also inhibitory
and is GABAergic. The globus pallidus, its external segment connects with the subthalamus.
So we see that connection right in through here. This is also inhibitory and that it’s GABAergic.
Subthalamic output to the substantia nigra is shown here in this connection.
This is an excitatory pathway in that it is glutamatergic. Then the last consideration
is the connection that exists between the substantia nigra and the striatum. We see that
connection here. This is going to be dopaminergic, so dopamine is the neurotransmitter.