Basal Ganglia

signals that are balanced so as to help improve motor learning each time an attempt is made to learn something new.

Anatomically, there are three lobes to the cerebellum. These are called the anterior lobe, the posterior lobe, and a very small flocculonodular lobe. There is a primary fissure between the anterior and posterior lobes as well as a posterolateral fissure that separates the flocculonodular lobe from the posterior lobe.

The cerebellum is also another way to divide the cerebellum. Centrally, there is a vermis with an intermediate zone on either side of it. Outside of this zone are the lateral hemispheres. These zones are not anatomic differences visible by looking at the cerebellum itself but are still structurally separate from one another.

A third way to divide the cerebellum is by the different functions of this structure. These have long names, called the cerebrocerebellum, the spinocerebellum, and the vestibulocerebellum. The cerebrocerebellum is large and is made by the lateral hemispheres. This area helps to plan movements and to help you learn new movements accurately. It also helps to guide movements that depend on visual guidance.

The spinocerebellum is midline and made from the vermis and intermediate zone. It is involved with the regulation of body movements because it helps you correct errors made during movement and received proprioceptive data. Proprioception involves the ability to recognize where the body parts are in space so you can stand upright and walk, even when your eyes are closed.

The tiny flocculonodular node is where the vestibulocerebellum functional unit is located. It helps improve balance and coordinate the reflexes received from the eyes and vestibular or ear-related balancing system. It helps the eyes and ears work together in order to allow for proper balance.

BASAL GANGLIA

The basal ganglia is a structure made from a number of nuclei deep to the cortex of the brain. Nuclei that make up the basal ganglia are not physically connected to one another but are instead functionally related to one another. The basal ganglia is a large feedback

unit that takes information from all parts of the brain and elsewhere, feeding it all back through the thalamus and back into the thinking or cortical parts of the brain. The thalamus, as you will find out, is one of the main structures for combining and relaying information from outside the brain to the cortex.

You should know that, despite the name “basal ganglia”, these are not ganglia we are talking about because ganglia exist only outside the brain. Instead the basal ganglia consists of nuclei rather than ganglia.

The basal ganglia is actually spread throughout the forebrain and consists of three types of nuclei. There are input nuclei, intrinsic nuclei, and output nuclei. The input nuclei receive input from outside the basal ganglia, including the thalamus, the cortex, and the substantia nigra. The three input nuclei are the putamen, the caudate nucleus, and the accumbens nucleus.

The output nuclei are those that send information mainly to the thalamus. These include the internal part of the globus pallidus and a structure that goes by the long name of substantia nigra pars reticulata. The intrinsic nuclei are the external part of the globus pallidus, the substantia nigra pars compacta, and the subthalamic nucleus. These function between the input and output nuclei. The whole thing forms a sort of circle from the cortex and thalamus, through the different nuclei in the basal ganglia, and finally back to the thalamus. The thalamus then sends signals back up to the cortex. Figure 11 shows the structures of the basal ganglia:

Figure 11.

Anatomically, you will see the globus pallidus and the putamen together, in which they are called the lentiform nucleus. It looks like a single grouping of gray matter in the deepest part of the brain below the hemispheres. There is a capsule lateral to these structures and a thinner structure just lateral to that, called the claustrum. The claustrum is not a part of the basal ganglia, even though it is structurally close to it.

In the most medial part of this structure are the substantia nigra and the subthalamic nucleus. The substantia nigra is dark in color because the cells contain a dark colored pigment called neuromelanin. Above the substantia nigra is the subthalamic nucleus.

All of these structures are involved in refining and modulating the activity of the cortex, mostly as it relates to motor activities. It helps you move in ways that keep any