ganglia should actually be called the basal nucleus since it is a
collection of nuclear groups which developed at the floor of the
lateral ventricle close tot the 3rd ventricle and around
the diencephalon and the lateral wall of lateral ventricle. They are
actually telencephalic structures, having developed from the
telencephalic brain vesicle which in turn comes from the
prosencephalon. They have important function in the human body. The
basal ganglia is said to be the head ganglion of proprioception in
the body. When damaged or diseased, coordination of movement is
impaired because again it is a strong center for the control of
extrapyramidal system, together with the cerebellum. When clincians
refer to the extrapyramidal system, most tend to assume it is the
basal ganglia. This is because of the common condition known as
parkinsonism or Parkinson's disease which is caused by impairment of
a part of the basal ganglia.
ganglia reaches its highest level of development in birds where it
controls the motor function of this group of animals. When a bird
(like the hen) has its cortex removed, it is able to function is if
nothing has happened to it. But once the basal ganglia is damaged
the bird is unable to perform all its intrinsic or instinctual
mechanism such as laying egg, sitting or incubating the laid eggs,
courtship, which is a complex repetitive process in birds etc.
Hence, it is recognised as a center for instinctual mechanisms,
whether motor or other wise. It is therefore not too bad to suggest
that the basal ganglia in man may also be responsible for any
instinctual mechanism in man, if present at all. The only type of
instinct which may be recognized in man are probably the rudiments
of temperaments. This shows the difference between temperaments as
inheritable traits on one hand, character as modifiable behavior due
to environmental influences and personality which are conscious
behavioral attitudes which usually do not have anything to do with
temperament or indeed character.
system described by Papez which seems to be related to human
behaviour and emotion has a generous components from the basal
ganglia consist of two parts
division of the basal ganglia recognizes the following parts
Archistratium, which is the amygdala
Paleostriatum, which is the globus pallidus
Neostriatum, which is the putamen and caudate nucleus
for neostriatum is the striatum.
for paleostriatum is pallidum for short.
mainly motor part of the basal ganglia while striatum is mainly
sensory part. Hence striatum receive many afferent projections but
gives out only a few efferent ones. On the other hand pallidum has
mainly efferent projections but receives only a few afferent fibers.
striatum is therefore made up of the pallidum and the striatum as
nucleus is further divided into
1 putamen 2 globus pallidus 3 insular cortex 4 internal capsule 5
extreme capsule 6 claustrum 7 external capsule 8 lateral ventricle
This is the
sensory part of the the basal ganglia. It receives fibers from the
striatal tract. This tract interconnects the midbrain with the
basal ganglia and it manufactures dopamine which is extensively
used in the basal ganglia. The deficiency of this amine will
Thalamostriatal tract. This tract begins from the thalamus and
ends in the striatum
Pallidostriatal tract. This tracts begins from the pallidum and
interconnects with the striatum
A few efferent
projections are recognized
tract (between the striatum and the substantia nigra)
tract. This important tract helps to keep information from the
sensory part of the basal ganglia to the motor part (pallidum). It
forms pencil like striations on the pallidum and is therefore called
is the motor part of the basal ganglia. It has numerous efferent
projections of which the most important are as follows
lenticularis. This project from the pallidum to the Forelís
field from where they enter Forelís field H2.
fasciculus. This project into Forel's field H1.
Subthalamic fasciculus. This interconnects with the subthalamus
fasciculus projects to the thalamus
Pallidotegmental fasciculus. This connects with the pontine
reticular formation called nucleus tegmenti pedunculopontinus.
is divided into the following parts
It is also
divided into two main nuclear groups
It is also
related to associated nuclei called the periamgydaloid body. The
periamygdaloid body is more related to the paleocortex than the
basal ganglia. It is part of the smell brain. But its association
with the amygdala suggest that at least in animals where the sense
of smell is important, the basal ganglia functions effectively.
the basal ganglia can lead to the following clinical conditions,
which are all essentially dyskinesias (abnormal movements).
Tremor at rest
is a slow worm like movement affecting mainly the extremities and
also the muscles of the neck and face
Chorea: This is
a graceful movement which appear to be purposeful but are
involuntary and they involve facial muscles and distal extremities.
Ballism: This is
violent involuntary movement especially involving the pelvic and
refer to ballism in only one side of the body
disease occurs as a result of depletion of dopamine at the
nigrostriatal tract. It causes extrapyramidal symptoms which include
cogwheel rigidity and early tremors.
Professional Neuroanatomy Theory