Corpus Striatum, also called striatum, is an important nucleus present in the forebrain. You must have thought which part of the brain controls cognition, reward, and coordinated movements. Well, corpus striatum is your answer. Being a part of basal ganglia, it controls many important functions.
In this educational article, we will talk about the anatomical features of striatum like its location, structure and input and output fibers. We will also talk a look at its functions and the clinical importance of striatum.
As said earlier, corpus striatum is a part of basal ganglia. It is located deep in the cerebral hemispheres. It is situated just lateral to the thalamus.
Corpus striatum is considered to be the largest structure present in basal ganglia. It is divided into two parts, dorsal striatum and ventral striatum. A brief detail of these parts is discussed below.
It is further divided by the internal capsule into two parts, caudate nucleus, and putamen.
Caudate Nucleus is a large C-shaped mass of grey matter a head, body, and tail. The head of the caudate nucleus is large and round and forms the anterior horn of the fourth ventricle.
It is also continuous with the putamen of the lentiform nucleus. The head is continuous with a linear and narrow-body which in turn tapers into a tail. The tail follows the contour of the lateral ventricle. The tail of the caudate nucleus terminates as the amygdaloid nucleus.
Putamen is a round nucleus located at the base of the forebrain. It is continuous with the head of the caudate nucleus.
It is further divided into nucleus accumbens and olfactory tubercle.
Nucleus accumbens is located in basal forebrain in the preoptic area. It has an outer shell and an inner core. The inner core is a part of the ventral striatum. Most of the neurons in nucleus accumbens are GABAergic neurons.
Olfactory tubercle is a processing center that is common to both the olfactory cortex and ventral striatum. It is also located in the basal area of the forebrain.
Corpus striatum receives a number of connections from other areas of the brain. These connections can be divided into the afferent fibers entering the striatum and the efferent fibers leaving it. A brief detail is given below.
The most important input fibers come to striatum from the cortex. It receives projection fibers arising from the pyramidal neurons located in the fifth layer of cortex. These neurons are glutaminergic neurons.
Striatum is considered to have its own microcircuit of neurons in which neurons of one part send and receive fibers from other parts of striatum.
Ventral striatum receives fibers from amygdala and hypothalamus. Nucleus accumbens in ventral striatum receives mesolimbic pathway from the ventral tegmental area.
Basal ganglia receive fibers from the ventral striatum. It also receives nigrostriatal fibers from substantia nigra located in midbrain.
Efferent fibers from the striatum project mainly to the dorsal pallidum and dorsomedial nucleus of the thalamus. It also sends fibers to globus pallidus and pars reticulata of substantia nigra. These neurons are inhibitory GABAergic neurons.
The blood supply to the striatum is mainly provided via anterior and middle cerebral arteries. Recurrent branch of anterior cerebral artery and striatal branches as well as anterior choroidal branch of middle cerebral artery provide blood to most of the parts of striatum.
There is a list of functions performed by corpus striatum. The ventral striatum performs a different set of functions as compared to dorsal striatum.
Ventral striatum is mainly concerned with cognition, reward, and reinforcement. On the other hand, dorsal striatum is mainly associated with the cognition involving motor functions.
We will take a brief look at these functions below.
Reward and Reinforcement
This function is performed by ventral striatum. Nucleus accumbens is the most important part of ventral striatum involved in reward and reinforcement. It is a part of the reward system of the brain. The dopaminergic neurons in nucleus accumbens are associated with the feelings of reward and pleasure associated with food, sex, and other such stimuli.
The olfactory tubercle is also involved in reward and reinforcement process. As it is associated with the olfactory stimuli, it is responsible for cocaine reinforcement. It is also involved in arousal.
Aversion from a negative stimulus and positive punishment response is also a function performed by ventral striatum mainly the nucleus accumbens.
Nucleus accumbens of ventral striatum is also involved in regulating the slow-wave sleep.
This is the most important function performed by dorsal striatum. The dorsal striatum controls the motor cognition via its connections with the cortex, thalamus, substantia nigra and globus pallidus.
Sensory information regarding motor control is perceived and processed by the sensory cortex which then sends signals to the striatum. The caudate and lentiform nuclei then process this information and send appropriate signals to the thalamus. Based on the information received from cortex, the signals sent to the thalamus inhibition of the voluntary, coordinated movements.
Clinical may be excitatory or inhibitory. It in turn results in stimulation or
Clinical significance of corpus striatum is mainly due to the diseases of the basal ganglia, a part of the dorsal striatum.
Nucleus accumbens of the ventral striatum also have some important clinical significance. All this is discussed in the following sections.
It is a hyperkinetic disorder due to disease of the basal ganglia. It results in a condition in which the patient exhibits involuntary, quick, jerky movements. These movements are non-repetitive in nature.
It is an inherited disease in which there is loss of GABA secreting, substance P-secreting and acetylcholine secreting neurons in the pathway of the dorsal striatum. It results in choreiform involuntary movements that are progressive in nature. It also causes progressive dementia.
It is a disease of childhood associated with rheumatic fever. The antibodies are formed that destroy the membranes of striatal neurons. It results in rapid, involuntary and irregular movements of limbs, face, and trunk.
It is due to neuronal degeneration in the substantia nigra, and to a lesser extent, in the globus pallidus, putamen, and caudate nucleus. It results in decreased dopamine in the striatal neuronal pathways. As a result, the patient exhibits signs and symptoms represented by the mnemonic TRAP. These are mentioned below:
- Tremors: The tremors seen in Parkinson’s disease are resting tremors. They occur when the limb is resting. These tremors disappear during sleep.
- Rigidity: The rigidity is present in opposing muscle groups and is different from the rigidity that occurs in upper motor neuron lesions. If tremor is absent, rigidity is called plastic rigidity. If the tremor is present, it is called cogwheel rigidity, as it is overcome by a series of jerks.
- Akinesia/Bradykinesia: It is referred to as difficulty in initiating and performing new movements by the patient. The resultant movements are slow, and the swinging of arms is absent. The face of the patient is expressionless along with slurred and unmodulated speech.
- Postural disturbances: The patient has a characteristic posture with stoop and flexed arms. He walks by taking short steps and is often to stop the movement.
Corpus striatum, the largest part of basal ganglia, is present deep in the forebrain.
It is divided into two parts; dorsal striatum and ventral striatum.
Dorsal striatum consists of two parts; caudate nucleus and putamen. Caudate nucleus is a C-shaped nucleus with a head, body, and tail. The head of the caudate nucleus is present in proximity to the putamen.
Ventral striatum consists of nucleus accumbens and olfactory tubercle. Both these parts are present in the basal area of the forebrain.
Afferent fibers are received from cerebral cortex, amygdala, hippocampus, and substantia nigra.
Efferent fibers project from corpus striatum to nuclei of dorsal pallidum and thalamus as well as globus pallidus and par reticulata of midbrain.
The blood supply is derived from anterior and middle cerebral arteries.
Corpus striatum has the most important role in reward and reinforcement circuit of the brain. This function is mainly performed by nucleus accumbens and olfactory tubercle of ventral striatum.
Ventral striatum is also important for abrasive behavior and sleep control.
The dorsal striatum is mainly involved in the cognitive control of motor functions. It helps modulate the voluntary movements according to the sensory information received from various parts of the body.
Any damage or injury to corpus striatum can result in one of the following clinical manifestations:
- Sydenham chorea
- Huntington’s disease
- Parkinson’s disease
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