The topic we will be discussing in this video is basal ganglia. Under this topic we will be discussing the anatomy of the basal ganglia, the putamen circuit, some clinical abnormalities like chorea, athetosis, hemibelismus, parkinson's and lastly we will be discussing the caudate circuit. then we will be including some practice questions so that is a question and answer on pg entrance examination so starting with the anatomy of basal ganglia discussing them anatomy of the basal ganglia, if we take a complete brain structure, then it has two cerebral hemispheres. When we take the horizontal section of those two cerebral hemispheres, then we see some structure like this. In this, we see that on the periphery, this grey matter is present and under that is white matter.
In this white matter, there are many nucleuses and structures present, which we will see now. So, most importantly, we say that this structure present which is most medially present is called thalamus both the cerebral hemispheres have this structure called thalamus these thalamus are connected to each other through interthalamic adhesion through interthalamic adhesion now After the thalamus, we know that just literally there is an internal capsule present in the thalamus. This is the internal capsule.
The internal capsule has anterior limb, genus, posterior limb and retro lenticular part of the internal capsule. So, this is the internal capsule and there are four parts of internal capsule, internal limb of the internal capsule, geno of the internal capsule, posterior limb of the internal capsule and retrolenticular part of the internal capsule. Coming laterally to the internal capsule, laterally present is a structure which we call as Globus Pallidus.
Globus Pallidus also has two parts, one is the internal part of the Globus Pallidus and external part of the Globus Pallidus. This is the internal part of the Globus Pallidus and this is the external part of the Globus abilities Globus pallidus also has a structure called putamen. This is the putamen.
Globus pallidus and putamen are combined to form lentiform nucleus. Now, above putamen, there is a structure called caudate nucleus. This is the head of the caudate nucleus. This caudate nucleus is a C-shaped structure which is inside and terminates here.
so here is the head of the caudate nucleus then comes the body of the caudate nucleus which is not visible in the diagram because it is a 2D diagram so there will be the body of the caudate nucleus and after that comes the tail of the caudate nucleus so this is basically a structure which is present deep nucleus in the brain lentiform nucleus that is putamen or globus pallidus or caudate nucleus these three are called basal canglia so this globus pallidus this putamen and this caudate nucleus. By combining these three, we call it basal ganglia. So this is basically the 2D anatomy of the basal ganglia. Now if we see this basal ganglia in 3D version, so this is the diagram in which we see this is the thalamus. There are different parts of thalamus like pulvinar, medial geniculate body and lateral geniculate body.
After that, the just laterally present part of thalamus is called lentiform nucleus. In this lentiform nucleus, globus pallidus or putamine Both are included. From this lentiform nucleus, a caudate nucleus is formed.
This is the head of the caudate nucleus. This is the body of the caudate nucleus. And this is the tail of the caudate nucleus. The tail of the caudate nucleus ends in the amygdaloid body.
So, this complete is the structure known as the basal ganglia. Now, this caudate nucleus, this putamen and globus pallidus, by combining these three, we call them basal nuclei and basal ganglia. Now, the caudate nucleus and putamen, by combining these two, we call them Stratum. And putamen and globus pallidus, by combining them, we call them Lendiform Nucleus.
And by combining these three structures, we call them Basal Nuclei or you can say Basal Ganglia. Because it is the grey matter present inside the white matter of the cerebral cortex. We know that this is the whole white matter and this grey matter present inside the white matter. We know that the gray matter present inside CNS is called nuclei and the gray matter present outside CNS is called ganglia. But basal ganglia is an exception you can say.
And conventionally we call it basal ganglia even though it is present inside CNS. In other places, we say that if gray matter is present inside CNS, if there is a collection of cytomes, then we call it basal ganglia. We call it as Nuclei and outside CNS we call it as Ganglia. So this is the Basal Ganglia, this is the basic anatomy of the Basal Ganglia.
After completing this anatomy of the Basal Ganglia, we will be discussing the next part that is the Putamen circuit. So before starting putamen circuit, we have to understand which are the major circuits involved in basal ganglia. Basal ganglia performs all its functions through mainly two circuits.
the putamen circuit and the caudate circuit. These are two major circuits which are present in the basal ganglia through which the basal ganglia performs all its functions. Now what are the functions that putamen circuit performs and what are the functions that caudate circuit performs? Putamen circuit is responsible for the role of basal ganglia in executing patterns of the motor activity.
As say, those motor activity which require a specific pattern. they have a role in executing the basal ganglia. Like example, handwriting, cutting paper with scissors, hammering nails etc.
Like if you have to write something, if you have to write something, then you have to write it in a definite pattern. Like if this is written, then it is not like R is so big, then E is so small, then S is so big, then P is small. No. There should be a definite pattern of writing.
And if R is like this here, then R is like this here too. So this The putamen circuit works to execute the definite pattern of the writing. Simultaneously, if you have to cut a paper with scissors, if you have to cut it straight, then you have to cut it in a pattern. if the pattern is not maintained then the cutting will be zigzag so to maintain the pattern the role that is performed is called putamen circuit similarly if we talk about hammering nails like if you hammer a nail then you strike at a definite point The motor activity which is happening in a specific pattern, for that the putamen circuit of the basal ganglia is responsible.
Now the second function which the caudate circuit performs is that it is responsible for the role of basal ganglia for cognitive control of sequences of motor patterns. Like whatever motor sequences are there, their cognitive control. What is cognition?
Cognition is basically the sensory inputs combined with memory. When we combine our sensory inputs with stored memory and create a definite thinking process, that is called cognitive control. So, if we want to do any motor pattern sequentially, if we want to do it very fast and it should have cognitive control, then the basal ganglia's caudate circuit is responsible for that.
Example, instantaneous response to line approach. if a lion approaches, what does a person generally do? it has a very fast and instantaneous response when it sees the lion from the front it turns around first then it runs and if it sees an object at a height like a tree or something like that it climbs on it so these were the sequences of the motor patterns that the person performs and it also had the function of cognition because it had a stored memory that the lion cannot climb the tree so to avoid that it tries to climb the tree or climbs so this was the cognitive control, this cognitive control to perform the motor patterns sequentially and with the timing, there should be the specific and instantaneous responses of the caudate circuit So, instantaneously the function performed by the basal ganglia is the function of the quadrate circuit of the basal ganglia. So, these were the two circuits, the putamen circuit and the quadrate circuit.
Now, we will read the basic neural pathways of the putamen circuit. When we read the Putamen Circuit properly, we will see how It receives input from brain Which parts of the brain it receives input from Through which route it transfers And where it gets its information terminated There are some ancillary pathways as well as some additional pathways Which are different from primary pathways But they also have importance So coming to the neural pathways of the putamen circuit Firstly the inputs Inputs which the putamen circuit generally receives It does pre-motor areas from supplementary areas and somatosensory areas. We have understood these areas very well in the videos on somatosensory cortex.
So, the information is received from premotor areas, supplementary areas and somatosensory areas. It can receive some information from the primary motor area also. Then its root is, because it is a putamen circuit, so it will go to the anterior and ventral lateral nuclei of thalamus from the putamen to the internal globus pallidus.
So this was the inputs, it received these inputs. these inputs go first in putamen this is the putamen first we need to understand the structure this is the putamen this orange colour is the putamen this is the globus pallidus this is the internal globus pallidus and this is the external globus pallidus this is the caudate nucleus and this is the thalamus so firstly these inputs go first in putamen After coming to the putamen, these inputs go to the internal globus pallidus. So this information goes to the internal globus pallidus. From the internal globus pallidus, it goes to the thalamus.
In the thalamus also, it goes to the ventral anterior and ventral lateral nuclei of the thalamus. After that, Fibers are terminated in primary motor cortex. Some fibers are terminated in pre-motor and supplementary areas. So this was the main pathway of the putamen circuit. Now, there are some ancillary pathways.
Ancillary pathways are additional pathways from the main pathway. There are some additional pathways present from the main pathway and these are also important pathways. These ancillary pathways move through external globus pallidus, subthalamus and substantia nigra. So first of all, there are all inputs to the putamen.
From the putamen, it will go to the external globus pallidus. From the external globus pallidus, this information will go to the subthalamus and some will go to the substantia nigra. Mid brain has two main structures Red nucleus and laterally grey matter which we call as Substantia Nigra It is a very important structure present in mid brain which is very much asked So, what happens is that it terminates in Substantia Nigra Neurotransmitters present in Substantia Nigra are dopamine So, the synapse present here The neurotransmitters involved in the synapse will be mainly dopamine.
Then from here, the output goes from the substantia nigra and information goes from the subthalamic nuclei, once again ventro anterior and ventrolateral nucleus of the thalamus and from there they terminate once again in the primary motor cortex, mainly in the primary motor cortex. So this was the neural pathways of the putamen circuit, how the input came, how it performed the root and how the output went and some ancillary pathways which help in this. to build up the putamen circuit. So, this is the first circuit that we have studied, that is the putamen circuit. After studying the putamen circuit, we will mainly study some clinical abnormalities like chorea, athetosis, hemibolism, and Parkinson's.
Now, coming to some clinical abnormalities which are mainly present in the putamen circuit. These clinical abnormalities are very important and very frequently asked in PG entrance examination. So starting with Korea. is mainly due to the coria which is seen mainly due to the multiple lesions in the putamen in the putamen, we get to see coria due to multiple small lesions in this, there are flicking movements of the limb, face and neck like any limb will suddenly flick coria actually means dance like movement so it will actually lead to the dance like movement of the limb, face and neck You will feel that the person is dancing So due to the flicking movements Lips are affected the most In which the flicking movements of the limbs happen Suddenly they keep flicking So this is the condition of Choria And this Choria is mainly due to the lesions in the putamen Next is Aethetesis Aethetesis is mainly caused due to the lesions in the Globus Pallidus Now what happens in this athetosis? There is a spontaneous and snake-like continuous writing movements of the hand.
We get to see many more clinical features in athetosis. But the main most important feature is spontaneous and snake-like continuous writing movements. writing movement of the hands.
Like the hand movements will be like this. You will feel that it is in continuous writing movement and there will be snake like movements. Snake like continuous writing movements of the hand will be there. This is the condition of aethetisis.
And this is mainly caused due to the lesions in the globus pallidus. Now next condition is hemibelismus hemibelismus is due to mainly due to the lesions in subthalamus okay. what happens in hemibolismus there is a flaying movements of the entire limb of the one side the whole limb will be extended all of a sudden the whole limb will be extended all of a sudden so it is a very disappointing condition the whole limb of one side will be affected like right hand or right leg affected in which he will throw right leg and right hand away from him and then bring them near him so this is the flailing movement of the entire limb of the one side which is caused due to the lesions in the subthalamus and the condition is known as hemibalismus next is the Parkinson's disease see we will study Parkinson's disease later in a good way a little information like it is also due to the lesions of substantia nigra and it includes rigidity, akinesia, tremors and many more things so we will understand this more in the next videos so this was some clinical abnormalities in the putamen circuit after these clinical abnormalities we will be discussing the caudate circuit So coming to the neural pathways of the quadrate circuit We have already studied that the quadrate nucleus is responsible for the cognitive control of sequences of motor patterns Which is a function of basal ganglia which is performed through the quadrate circuit Once we will understand the neural pathways of this quadrate circuit So this is the cerebral cortex and the basal region of the cerebral cortex We took a transverse section of that this This is the transfer section where the thalamus is attached through interthalamic adhesion Laterally present of thalamus is the globus pallidus This is the internal globus pallidus and external globus pallidus Then this is the putamen And this is the caudate nucleus, the C-shaped caudate nucleus which goes from the inside and terminates here. This is the subthalamus and this is the midbrain, which is the structure present below it.
This is the midbrain, in the midbrain, this is substantia nigra, this is the red nucleus and this is the cerebral aqueduct. And around the cerebral aqueduct, a grey matter is present which is known as periaqueductal grey matter. So, in the PUTAMIN circuit, the ancillary pathways go through SUBTHALMUS and SUBSTANTIA nigra.
But in the caudate circuit, the ancillary pathways do not go through subthalamus and substantia nigra. Actually, there is no involvement of subthalamus and midbrain or substantia nigra in it. So we will read how ancillary pathways move. First of all, we will understand the main pathway. Its inputs are mainly received from the association area.
It receives inputs from the association area. By receiving inputs from association area, because it is a quadrate circuit so obviously it gives the information to the quadrate nucleus clear some more information it receives from premotor, supplementary and different areas of the brain and it gives it to the quadrate nucleus now after going to the quadrate nucleus its main root goes to the quadrate nucleus from there it goes to the internal globus pallidus and after that it goes to the ventrointerior and ventrolateral nuclei of thalamus so from the quadrate nucleus, this information will go to the internal globus pallidus and from the internal globus pallidus, this information will go to the ventral anterior and ventral lateral nuclei of the thalamus now, the information that will terminate from here will terminate mainly in the premotor areas and supplementary motor areas see if you are not understanding the areas, so for the areas, we have cleared all the areas in the somatosensory cortex the different areas that we had studied we have cleared all those areas in our previous videos so you can watch those videos to get a better understanding of the areas of these brain these cerebral cortex ok so it terminates in premotor areas and supplementary motor areas it mainly terminates see why it terminates in premotor areas and supplementary motor areas there is a main reason for it because actually what is its work we have seen that the main example of this is of cognitive control so the areas responsible for cognition are mainly responsible that's why it terminates here and after that the cognitive approach of information is then performed through descending pathway that's why there is involvement of basal ganglia so this terminate now after this here are some ancillary pathways once again what are ancillary pathways these are some additional pathways which are additional from main pathways but important pathways are there so coming to these ancillary pathways these ancillary pathways include the putamen so from the quadrate nucleus main pathway goes directly from internal globus pallidus to thalamus but ancillary pathways goes from quadrate nucleus to putamen me. Then from putamine we go to internal globus pallidus and then ventro anterior and ventrolateral nuclei of thalamus and then after that we go to premotor areas and supplementary motor areas. There is no involvement of subthalamus and midbrain in the neural pathways of the quadrate circuit. So, these were the neural pathways of the quadrate circuit.
So, a small topic is Basal Ganglia, in which we mainly study the Putamen and Quadrate circuits. Anatomy of the Basal Ganglia is important. We have discussed the Basal Ganglia which includes the Globus Fallidus, the Putamen and the Quadrate nucleus. After that, there are some other important functions of the Basal Ganglia. and some disorders related like Parkinson's disease and Huntington's scoria which we will discuss in further videos but before that we will discuss the Q&A on the PG entrance exams because this is a very important topic from the PG point of view so now we will be discussing the question and answer on PG entrance exams Now coming to the Q&A on PG entrance examination.
Question number one is lesion of the globus pallidus causes. Option A, chorea. Option B, bellissimus.
Option C, athetosis. And option D. akinesia this question was asked in NEET 2013 pgipg aipg 2015 and NEET pg 2012 coming to the answer of this question we know we have already discussed in the clinical abnormalities of the putamen circuit that a lesion of the globus pallidus causes athetosis so the answer for question number one is c athetosis now question number second the main role of the basal ganglia Thank you. Option A, temperature regulation. Option B, planning and programming of movement.
Option C, gross motor activity. And option D, equilibrium. This question was asked in AIPG 2015. And we obviously know the main role of the basal ganglia is planning and controlling of the movement. Because the temperature regulation is the function of hypothalamus, mainly the function of the hypothalamus. Gross motor activity is mainly the function of the motor cortex.
Equilibrium is mainly the property of vestibular apparatus. So planning and programming of the movement is the main role of the basal ganglia. So the answer for question number second is B.
Now coming to question number third, the globus pallidus and putamen are present in option A, pons, option B, thalamus, option C, cerebellum and option D, basal ganglia. This question was asked in AIPG 2012 and need 2013 it is a very easy question we know that these both are involved these both are combinedly known as the lentiform nucleus and these are involved in these are present in basal ganglia okay now coming to the next question that is the which thalamic nuclei can produce the basal ganglia symptoms option a Thank you. Lateral dorsal, option B, pulvinar, option C, ventral anterior and option D, intralaminar.
This question was asked in AIPG 2013 and DLPG. We know that the circuits we read through basal ganglia. all these circuits go through ventral anterior and ventral lateral nuclei of the thalamus so ultimately any thalamic nuclei which is ventral anterior thalamic nuclei will produce the symptoms of basal ganglia because basal ganglia's circuits go through ventral anterior and ventral lateral nuclei of the thalamus so the answer for question number 4 is C ventral anterior Now coming to question number 5, not included in cerebellar nuclei. Option A, dentate nuclei. Option B, emboliform nuclei.
Option C, festigial nuclei. And option D, caudate nuclei. This question was asked in PGI-PG and we know that dentate nuclei, emboliform nuclei and festigial nuclei, these three are also of cerebellum nuclei. And the caudate nuclei, these are included in, these are included in, These are included in basal ganglia. So, the one which is not involved in cerebellar nuclei, that is the caudate nuclei.
So, the answer for question number 5 is D, caudate nuclei. Now, coming to question number 6, injury to the corpus stratum leads to? Option A, chorea.
Option B, parkinsonism. Option C, hemibalismus. And option D, athetosis. This question was asked in D, 2012. MH, PGM, CET and DNB, 2012. The answer to question number 6 is A.
Chorea. We know that corpus stratum is actually the putamen plus the putamen plus the caudate nucleus which we call corpus stratum. Like we had read that the caudate nucleus is A.
Chorea. We know that Chorea which is mainly due to the lesions in the putamen. and putamen is the part of corpus stratum so putamen ke andar problem hoga that is corpus stratum ke andar problem hoga toh obviously bathe korea ko wo lead karega so the answer for question number 6 is a korea now coming to the seventh question which one of the following act as major neurotransmitter in substantia nigra this question has been asked many times but in AIM speech it was asked directly but it is a very important question this question is asked in different formats option A is Serotonin option B is Acetylcholine option C is Dopamine and option D is Noradrenaline we know that we have already told you in this video that the major neurotransmitter involved in the synapses of Substantia Negra is dopamine so answer for question number seven is c dopamine okay so this was all about the this was all about the this basal ganglia if you think that this video deserves a like then please hit the like button share with your friends and for being updated with our next videos please subscribe the channel and press the bell icon to get notifications thank you