Cerebral cortex is divided into [several parts]: primary motor cortex, supplementary motor cortex, premotor cortex, prefrontal cortex, primary somatosensory cortex. And these cortical areas involved in motor movement, actually needed help from other brain circuits in order to orchestrate the movement.One of these circuit involved group of structure known as basal nuclei

Basal Nuclei

important role in posture, voluntary movements, learning and memory Not responsible for the execution of movement, only for initiation facilitation modulation of

movement Without the information from the basal nuclei, the cortex is unable to properly direct motor control,

(e.g Parkinson’s disease) Previously referred to as Basal ganglia(‘ganglia’ - outside the nervous system) ‘Basal’ to denote the position of nuclei at the base of the brain

Neurologic Structure

Basal Nucleus (Nuclei)

Caudate nucleus

Caudate nucleus

Lentiform nucleus

Globus pallidus plus putamen

Claustrum Claustrum Corpus striatum

Caudate nucleus plus lentiform nucleus

Neostriatum (or striatum)

Caudate nucleus plus putamen

Amygdaloid body

Amygdaloid nucleus

Anatomy of Basal Nuclei

Collection of masses of gray matter situated deep within each hemisphere.

a. Corpus striatum

o Caudate nucleuso Lentiform nucleus

i. Putamen ii. Globus Pallidus

b. Amygdaloid nucleusc. Claustrum

Corpus striatum

Lateral to the thalamus Internal capsule – band of nerve fibers which divide it into the caudate nucleus and the lentiform

nucleus Striated appearance due to strands of gray matter passing through internal capsule and connecting

caudate nucleus to putamen

PartsA. Caudate Nucleus

Large , C-shaped mass of gray matter closely related to lateral ventricles Head of the caudate nucleus

- continuous inferiorly with putamen of lentiform nucleus (neostriatum); just superior to this union, strands of gray matter pass through the internal capsule large and rounded

forms lateral wall of anterior horn of lateral ventricle Body of caudate nucleus

- long and narrow - continuous with the head in the region of the interventricular foramen

Tail of caudate nucleus - long and slender - enters the temporal lobe and terminates anteriorly in the amygdala/amygdaloid nucleus

Note: Functionally and histologically, Caudate and Putamen are similar. Anatomically, Putamen and Globus Pallidus lie close together and are shaped like a lens

B. Lentiform Nucleus Wedge shaped mass of gray matter which is divided into the putamen and globus pallidus. Separated from Caudate nucleus by the internal capsule Broad convex base directed laterally Blade directed medially Medial to internal capsule, which separates it from the caudate nucleus and the thalamus Lateral to a thin sheet of white matter (the external capsule) which separates it from a thin

sheet of gray matter (the claustrum) Divided into putamen & globus pallidus Putamen

o Larger, darker, lateral o Inferiorly at its anterior end, it is continuous with the head of caudate nucleus

Globus Palliduso Inner, lighter o Paleness due to presence of high concentration of myelinated nerve fibers

Globus pallidus and Putamen are separated by lateral medullary lamina Globus lies medial to putamen and is divided by two parts

o Lateral and external segmento Medial and internal segment

Note: Putamen, Caudate nucleus, Globus Phallidus consist of medium spiny neurons

Claustrum

thin sheet of gray matter separated from the lateral surface of the lentiform nucleus by the external capsule Function unknown

Amygdaloid nucleus

situated in temporal lobe close to uncus anatomically related to the basal nuclei functionally part of limbic system Can influence the body's response to environmental changes For example, in the sense of fear, it can change the heart rate, blood pressure, skin color, and rate of

respiration

Subthalmic nuclei and Substantia Nigra

Functionally related to but not anatomically part of Basal Nuclei Subthalamic nuclei – part of diencephalon of subthalamus Substansia Nigra – part of midbrain, two group of neuron pars compacta, and pars reticulate

Connections of the Corpus Striatum and Globus Pallidus Caudate nucleus and putamen (striatum)– main sites for receiving input to the basal nuclei

o Parts of Striatum

Dorsal part – caudate nuclei and putamen Ventral – nucleus accumbens (of limbic system)

Globus Phallidus- major site from which output leaves basal nuclei Receive no direct input from or output to the spinal cord

Afferent and efferent connections

Input/Afferent (to the Caudate Nucleus-Putamen) Output/Efferent (going to substantia nigra)

cerebral cortex (main) Thalamus Substansia nigra Brainstem

thalamus (main) subthalamus Midbrain

Cortical areas

Project to putamen Project to Caudate nuclei The primary motor area (area4) premotor area (lateral area6) supplementary motor (medial area

6) somatosensory (area 3,1, 2 )

frontal eye field (area 8) association areas of frontal and

parietal

Caudate nucleus/putamen (Afferent and efferent connections)

A. Afferent Fibers 1. Corticostriate Fibers

Each part of cerebral cortex projects axons to specific parts of the caudate-putamen complex

Most projections are from the cortex of the same side Largest input is from sensory-motor cortex Neurotransmitter is glutamate

2. Thalamostriate Fibers Intralaminar nuclei of the thalamus send large numbers of axons to caudate nucleus and

putamen

3. Nigrostriate Fibers Neurons in substantia nigra send axons to caudate nucleus and putamen Liberate dopamine at their terminals as neurotransmitter

o Based on the type of receptor, this input may be either excitatory (D1) or inhibitory (D2)

4. Brainstem Striatal Fibers Ascending fibers from the brainstem end in the caudate nucleus and putamen Liberate serotonin at their terminals as neurotransmitter Thought to be inhibitory

B. Efferent Fibers1. Striatopallidal Fibers

Striatopallidal fibers pass from the caudate nucleus and putamen to the globus pallidus Gamma-aminobutyric acid (GABA) as neurotransmitter

2. Striatonigral Fibers Striatonigral fibers pass from the caudate nucleus and putamen to the substantia nigra Some fibers use GABA or acetylcholine as neurotransmitter, others use substance P

Connections of the globus phallidus (afferent and efferent connections)

A. Afferent Fibers 1. Striatopallidal Fibers

Pass from the caudate nucleus and putamen to the globus pallidus GABA neurotransmitters

B. Efferent Fibers 1. Pallidofugal Fibers

Complicated and can be divided into groups: ansa lenticularis - pass to the thalamic nuclei fasciculus lenticularis - pass to the subthalamus pallidotegmental fibers - terminate in the caudal tegmentum of the midbrain pallidosubthalamic fibers - pass to the subthalamic nuclei