hello guys in this video I shall discuss thalamas now Thalamus is a little bit difficult Topic in the CNS and I have tried my level best to make it simple and easy for the sake of your exams so watch this video completely till the end and those people are watching this video and haven't subscribed to my channel do hit the Subscribe button so the learning objectives for this session are first let's try and understand the anatomical classification of the thalamic nuclei then we will look into the functional classification of the thalamic nuclei then we will understand the connections of the thalamus and the functions of the thalamas at last we will briefly look into one of the applied aspects of the thalamus which is called as the thalamic syndrome so let's first start with the anatomical classification of the thalamic nuclei as here we can see in the diagram a y-shaped internal medullary lamina is going to divide the entire gray matter of the thalamus into three masses of nuclei now within the limbs of the Y is what is called as the anterior group of nuclei and this side is the medial side of the thalamus and this side is the lateral side of the thalamus now medial to the internal medullary lamina we have what is called as the medial group of nuclei and obviously lateral to the internal medullary lamina we have what is called as the lateral group of nuclear now the anterior group has only one nucleus which is called as the anterior nucleus the medial group is having two nucleus one is called as the dorsomedial nucleus and the second one is called as the midline nucleus now the lateral group of nucleus is again divided into two groups okay one is called as the dorsal group another one is called as the ventral group now the dorsal group is having three nucleus one is lateral dorsal the second one is lateral posterior and the third one is called as the pulvinar whereas the ventral group is having ventral anterior ventral lateral ventral posterior medial and ventral posterior lateral the medial geniculate body and the lateral geniculate body the ventral posterior medial and ventral posterior lateral sometimes together are just referred as ventral posterior nucleus apart from this there is one more group of nucleus which is present within the internal medullary lamina and one such prominent nuclei which is present within the internal medullary lamina is what is called as centromedian nucleus apart from that there are so many other small discrete group of nuclei which are just called as intra-laminar nuclei so this is the anatomical classification of thalamic nuclei now let's try and understand the physiological classification of the thalamic nuclei so the first group is what is called as a non-specific nuclei so what is the function of this non-specific nuclei is that it receives impulses diffusely and then it also projects diffusely to The Wider areas of the CNS okay that means it is receiving the impulses from non-specific inputs and it is also projecting to the non-specific areas of the CNS so under the non-specific nuclei we have the intra laminar nuclei we have the central median nucleus and we also have the midline nucleus next comes what is called as a specific nuclei as the name itself is suggesting these are a group of nuclei which are receiving specific inputs and they are projecting to the specific portions of the neocortex unlike the non-specific nucleus okay so this specific nuclei is further divided into two categories the first one is what is called as the sensory relay nuclei okay under this category we have the ventral posterolateral nucleus the ventral posteromerial nucleus the lateral geniculate body and the medial geniculate body now coming to the motor control nucleus this is the second subgroup of the specific nucleus in this we have the ventral anterior and the ventral lateral nucleus the third group the third functional group is what is called as the association nuclei or these are also called as the integrative nuclei now as the name suggests these are the nuclei which are going to integrate two or more than two inputs like there should be an integration between audition and vision so there are nuclei which are going to integrate these two inputs so under the association nuclei we have palvinar we have the lateral dorsal nucleus and we also have the lateral posterior nucleus and the last group is what is called as the limbic system nuclei these are the nuclei which are having connections with the limbic system under this we have the anterior nucleus and we also have the dorsal medial nucleus so this was the anatomical and the physiological classification of the nuclear now let's try and understand the connections so first let's try and understand the connections of the non-specific nuclei so the non-specific nuclei as I have already discussed they are going to receive impulses non-specifically and also they are going to project to non-specific areas of the CNS so which are all the parts of the CNS from which they are going to receive the impulses so all these are afferent inputs which are going to the non-specific nuclei so the non-specific nuclei are going to receive the inputs from reticular activating system they receive the inputs from the paleospinothalamic tract they also receive the inputs from the striatum and also some areas of the hypothalamus so this input is going to these three non-specific nuclei which I have told you in the functional classification the Centro median nucleus the intra laminar nuclei and the midline nucleus and where do the project to they are going to project diffusely to different areas of the neocortex as well as the limbic system so these will be the reference to which this nuclei is going to project next let's try and understand the connections of the specific sensory nuclei so the first specific sensory nuclei is the medial geniculate body now as soon as I say medial geniculate body it should strike to your brain that medial geniculate body is a part and parcel of the auditory pathway that means the medial geniculate body is going to receive the information from the lateral laminiscus as well as the inferior collicoli again these are the part and parcel of the auditory pathway go and read your auditory pathway you will understand that lateral Le meniscus and the inferior collicolia are projecting to the medial geniculate body and the neurons which are arising from the medial geniculate body are ultimately projecting to the auditory cortex area number 41 and 42 so everything is interrelated now the next thing is regarding the lateral geniculate body and suddenly I think for so many people it has already striked that lateral geniculate body is a part and parcel of the visual pathway so lateral geniculate body is going to receive the occurrence from where it is going to receive the occurrence from the the optic track and where does the lateral geniculate body project to the lateral geniculate body is going to project to the visual cortex area number 17 18 and 19. okay the the tract which arises from the lateral geniculate body and projects to the visual cortex is also called is also called as what it is also called as Janai culo calcarine fibers or the janiacological so this is easy MGB a part of auditory pathway LGB is a part of the visual part visual pathway so these are the afferents and these are the connections which are going to the reference fine next we have what is called as the ventral posterior nucleus here for the sake of simplification I am not dividing the ventral posterior nucleus again into ventral posterior medial and ventral posterior lateral so the ventral posterior nucleus is going to receive the inputs from the dorsal column if you have read the ascending tracks then you will understand this from the spinothalamic tract and also from the trigeminal Le meniscus so we all know that the spinothalamic tract is carrying the sensation of the pain temperature and the crude touch dorsal column is carrying so many Sensations like vibration sensation pressure sensation tactile localization tactile discrimination stereognosis and trigeminal Le meniscus is the one which is carrying the sensations from the areas of the face so all these things are going to go and they are going to project to the ventral postage area nucleus of the thalamus now from here where do you think the efferents are going to go the afferents are going to go to the somatosensory cortex that is somatosensory area 1 and 2 which is located in the post Central gyrus see guys if we break it down break down the individual nuclei and study it is going to become very easy so three things are there here one is our medial geniculate body which is a part and parcel of the auditory pathway if I know the auditory pathway I can write the prior connection and the after connection of the medial genocide body next is the lateral geniculate body which is a part and parcel of the visual pathway if I know the visual pathway I can I can write which is the afferent and which is the afferent of the lateral geniculate body even if I don't remember the apparent and if I know that the medial geniculate body is a part and parcel of the auditory pathway that means the the fibers arising from the medial geniculate body are going and they are going through the visual they are going to according to record X similarly lateral geniculator body is going to the visual cortex and similarly the ventral posterior nucleus which is receiving all the somatic Sensations from the different areas of the body it is projecting to the somatosensory cortex as easy as this so this is the sensory nuclei so next let's try and understand the connections of the motor control nucleus the first motor control nuclei is the ventral lateral nucleus and it is receiving the information from the dentate nucleus and the Globus pallidus dentate and the Globus pallidus dentate nucleus is a part of the cerebellum and Globus pallidus is a part of the uh basal ganglia and if you if you remember uh my classes on the basal ganglia on the cerebellum I have told you that the neocerebellum is going to project outside to the dentite nucleus and dentate nucleus is going to project to the thalamus and from the thalamus the information is again going back to the cerebral hemisphere that is why it is called as cerebral cerebellum and even the Globus pallidus so from here the information or the efferents are going to the primary motor cortex so which is the afferent here afferent will be the fibers coming from the dentate nucleus and the Globus pallidus and efferents are going to the primary motor cortex then we have the ventral anterior nucleus which is again receiving the information from the Globus pallidus and the substantia Niagara we all know what these are parts of and these are projecting the ventral anterior nucleus of the thalamus is projecting to the pre-motor cortex okay ah Globus pallidus and substantia Niagara are part of what yes they are part of the basal ganglia and we all know in the basal ganglia there are two types of circuits one is called as the direct and indirect circuit ultimately these are going to the thalamus and from the thalamus they are again projecting to the cortex so which area of the cortex that is to the primota cortex so the efferents are going to the primota cortex next we have the connections of the limbic system nuclei so one nuclei which I had told you was this what is this nucleus this is the anterior nucleus as we are seeing here in the diagram the anterior nucleus is forming a part and parcel of what is called as the famous papers circuit and the anterior nucleus is receiving information from this body which is called as the mammillary body so anterior nucleus is receiving the afferent fibers from the mammillary body via the mammilothalamic tract and the anterior nucleus of the thalamus is projecting to the singulate gyrus via the thylomocortical projections so the afferents are the thalamo chord thalamo mamelothalamic tract sorry for that and the reference are the thalamo cortical projections which are projecting to the singulate gyrus and we all know that the singulate gyrus again projects to the hippocampal formation and from the hippocampal form formation the fibers are again coming back to the uh mammalary body as well as to the hypothalamus and this forms a circuit which is called as the pepper circuit so if we just remember the anterior nucleus of the thalamus is a part and parcel of the Pepe circuit things will become very easy okay so these are the things and what is this anterior nucleus of the thalamus concerned with it is concerned with emotions as well as recent memory then we have one more nucleus in the limbic system which is called as a dorsal medial nucleus remember that dorsal medial nucleus has got reciprocal Innovations reciprocal means to and fro on both the side sufferance as well as afferents with prefrontal cortex and what is its function it functions in thinking memory judgment as well as emotional Behavior so these are the connections of the limbic system nuclei now let's try and understand the connections of the integrative nuclei and the first nucleus here is pulbinar now pulmonar is going to receive the information from the superior colliculi inferior collically lateral geniculate body as well as the medial geniculator body so all these Superior collicoli inferior collically LGB and MGB are part and parcel of both the auditory Pathways as well as the visual pathways so that means what palvinar is doing palvinar is integrating two Sensations that is the auditory Sensations as well as the visual Sensations and to where it is projecting it is projecting to parietal cortex occipital cortex as well as the superior temporal cortex the next nucleus is the lateral posterior and it is receiving information from the superior colicles and the information is being projected efferent fibers are being projected to the superior parietal cortex next we have the lateral dorsal nucleus which is receiving also information from the superior collicules and the information is being projected to the singulate gyrus as well as to the para hippocampal guys so these are the connections of the integrative nuclei next let's try and understand the functions of the thalamus the first and foremost function of the thalamus is that Thalamus is the final sensory relay station of almost all the sensations except for the olfactory sensation second function is that it is also a center for integration and modification of peripheral sensory impulses it is not just a relay station it also helps in integration and modification it integrates and modifies these Sensations and from there it is going to project two different areas of the cortex third is that it is not just a sensory relay station or an integrator or a modifier it also helps in processing of the sensory information next is let's say from the thalamus all the fibers are projecting to the neocortex let's say those fibers are cut off still the person can perceive the sensations so that's why the thalamus is acting like a crude Center for perception of sensors he will he will perceive the sensors but the perception of sensors will not be having a finer touch he can just tell that as some sensation I am able to feel but maybe he will be not be able to discriminate the intensity or find Nui answers of the sensation so it is acting like a crude Center for perception of senses it is also acting as a center for integration of the motor functions not just the sensory functions s we also have the specific motor nuclei here and it also acts as a center for so many reflex activities coming to the next function it has got a function in arousal and alertness why because it is having connection with what is called as reticular activating system next it has got a role in emotional behavior of the person why because of its connections with the limbic system and we have dedicated nuclei which are forming a part and parcel in connections of the limbic system it has also got a role in language it has got a role also in very important Genesis and synchronization of the EEG okay and it is also a center for integration of somatic and the visceral functions okay so these are all the functions of the thalamus coming to the last subtopic that is the thalamic syndrome the thalamic syndrome occurs because of blockage of this artery which is called as thalamo geniculate branch of the posterior cerebral artery okay so what happens when this branch is blocked is there is going to be a damage to posterior ventral as well as the posterolateral nucleus basically so that causes loss or reduction of the sensations that is very much understood because almost all the sensations are relaying to the thalamus so there is going to be a loss or reduction of Sensations there is also going to be asteriognosis I will not tell you what is this by this time you will know what is asteriognosis and stereognosis and there is also going to be one very peculiar feature which is called as thalamic Phantom limb so what is the meaning of this thalamic Phantom limb like if I close my eyes I can lock it where my limb is but if the person who is having this thalamic syndrome if he closes his eyes he says I don't have limbs because he is unable to locate the limbs why because the sensations which are coming from the limbs are not processed in the thalamus because of the blockage of these arteries next there is going to be also one more peculiar feature of the thalamic syndrome which is called as thalamic overreaction now till this point of time I am telling you that there will be a loss of sensation or a reduction of the sensation and the person is unable to know where his limb is that is called as the Phantom limb and all that now on the other side there could be also thalamic over reaction that means the threshold for pain is increased the threshold for temperature is increased and the threshold for touch is also exaggerated that means if I just touch the person the person says it is painful if I inflict some kind of a pain he is going to just shout out and say ma this is very very very painful so this is called as thalamic overreaction okay there is also going to be Ataxia which can occur because of the loss of motor functions there will be so many involuntary movements so all these features are occurring because of the loss of the motor functions and there is also going to be a peculiar feature which is called as thalamic hand wherein there is going to be a flexion of the wrist and Hyper extension of the fingers so it looks something like that and this is the corresponding MRI showing the damage to the artery which is going to supply those parts of the thalamus so thalamic hand with the corresponding MRI so in this video we have learned the anatomical classification of the thalamus the functional classification of the thalamic nuclei the connections of the thalamus the functions of the thalamus and at last the thalamic syndrome if you have any doubt leave your doubts in the comment section and if you think this video was helpful for you for the sake of your exams and as well understanding do hit the like button share this video as much as possible and do do subscribe to my channel thank you