Basal Nuclei Anatomy - Lecture Notes

The lecture provides an overview of the basal nuclei anatomy.
Includes a review of previous anatomy, particularly related to indirect and direct pathways.
Identifies key structures within the telencephalon, diencephalon, midbrain, and pons.
Highlights the cortex and brachycortex.
Outlines the arcucortex, including the subiculum, hippocampus proper, and dentate gyrus.

Dorsal Striatum:
- Includes the caudate nucleus and putamen.
- These structures are considered the same, but split due to the emergence of the internal capsule.
- Represents the neostriatum, the most recently evolved part of the striatum.
Ventral Striatum:
- Includes the nucleus accumbens and the olfactory tubercle.
- Also a recently evolved neostriatum.
Globus Pallidus:
- Referred to as paleostriatum, indicating it's older than the neostriatum.
Ventral Pallidum:
- Part of the limbic loop.
Substantia Nigra:
- Focuses on the substantia nigra pars compacta.
- Also mentions the substantia nigra pars reticulata.
Subthalamus
- All these components are crucial for basal nuclei function.

Thalamus:
- The lecture references previous discussions, which combines motor and sensory aspects.
Hypothalamus:
- Identifies the hypothalamus and the third ventricle between the hypothalamus and thalamus.
Optic Tract:
- Notes the medial positioning of the optic tract in the coronal section, typical of diencephalonic structures.
Insular Cortex
- Highlights the insular cortex's location within the lateral fissure.

Moving medially from the insular cortex, one encounters:
- The basal nuclei.
- The thalamus (core).

The next gray matter structure, ignoring the extreme capsule, is the colostrum.
Historically considered part of the basal nuclei but not functionally, so it's excluded from consideration.

Head of the Caudate Nucleus:
- Colored in the diagram.
- Also referred to as dorsal striatum, especially when discussing overall function compared to the ventral striatum.
- The dorsal striatum receives input related to direct and indirect pathways.
- The ventral striatum is more GABAergic.
Tail of the Caudate Nucleus:
- Also part of the caudate nucleus.

The putamen connects and enlarges rostrally.
Together with the caudate nucleus, it functions together as the dorsal striatum.

Globus Pallidus External (Lateral):
Globus Pallidus Internal (Medial):
- External (lateral) and internal (medial) parts differ functionally.
- Both are part of the dorsal pallidum.
- Pallidum means light green.

Lentiform Nucleus:
- The globus pallidus and putamen together resemble a triangle or pizza slice.
- Lentiform nucleus means lens-shaped nucleus.
Corpus Striatum:
- Includes the lentiform nucleus and the caudate nucleus.
- The term striatum generally refers to the lentiform nucleus and caudate nucleus.

Subthalamus:
- Colored yellowish.
Substantia Nigra:
- Located within the midbrain.
- Composed of the substantia nigra pars compacta and substantia nigra pars reticulata.
- The substantia nigra is oblique in transverse sections.
Substantia Nigra Pars Compacta:
- Contains dopaminergic neurons, giving it a dark appearance (hence the name black substance in Italian).
Substantia Nigra Pars Reticulata:
- Functions similarly to the globus pallidus.
- Evolved from a piece of the globus pallidus.

The ventral tegmental area (VTA) is not part of the basal nuclei but inputs into it.
Located in the midbrain tegmentum.

As one moves rostrally, the putamen gets closer, and the structure grows larger.
Eventually, these merge into a gray matter structure called the head of the caudate nucleus.

The olfactory tubercle is part of the ventral striatum and is neostriatum.
Located ventrally, overhanging the midbrain, capturing a piece of it in the coronal section.
Processing of information here is a recent phylogenetic development.

The nucleus accumbens, formerly called the nucleus accumbens septae, is also a ventral striatum.
Both the olfactory tubercle and nucleus accumbens are neostriatum.
Dorsal striatum (caudate nucleus and putamen) functions differently than ventral striatum.
The ventral striatum is related to the limbic system.
The nucleus accumbens connects with the amygdaloid body for limbic connections and receives input from the olfactory system.
The ventral striatum replaces the globus pallidus medial/internal and is related to motivation, reward, and emotion.

The ventral pallidum replaces globus pallidus medial/internal and is related to the limbic system (motivation, reward, emotion).
It's a ventral light-green area.

The basal nuclei are involved in motor function, higher-order functions, and reward pathways.
The right side of the diagram (anatomical orientation) relates to the limbic system.
The left side relates to motor movement.

Extreme Capsule:
- A white matter tract between the insular cortex and claustrum.
- Functions as a pathway for input and output.
External Capsule:
- Feeds information down to the Putumin from above, and some information, say, down below can come up to the Putumin.
Internal Capsule:
- The route for upper motor neurons and third-order somatosensory cortex.

Almost all regions of the cerebral cortex project to the striatum.
The caudate nucleus is generally associated with cognition pathways.
The putamen is associated with motor control.
The basal nuclei do not initiate movement, cognition, or reward but act as a card catalog to locate algorithms in the brain.

Analogy: A Gothic library where the basal nuclei act as a card catalog.
Different rooms contain information about thinking, motor, and reward processes.
The caudate nucleus directs to cognition, and the putamen directs to motor processes.
The information gets processed and sends back information to the location in the neocortex.
The ventral striatum is related to reward.

The cortex projects down fibers (cortical striddle) to the neostrata (putamen).
Information is processed and outputted.
The output from the globus pallidus is called a pleido fiber.
This output then to the thalamus (palatothalamic tract).
Two areas in the motor are the ventral anterior nucleus and the ventral lateral nucleus.
The thalamus then projects back out fibers (thalamocortical fibers), also called TC fibers.
The TC fibers leads to motor.
This leads to the primary motor cortex, and then an upper motor neuron goes down to a lower motor neuron.