[Music] i'm gonna kind of cover briefly the some of the major loads and um and then we'll move into a little bit of function some of the major functions in in these lobes so starting with frontal lobe so when you think about the frontal lobe imagine that you're putting your palm on the patient's forehead and you're laying your first three fingers over their frontal lobe and that's a good way to think about the anatomy of the major gyri of the frontal lobe so looking at my cartoon here you can see there's there's two sulci running in an ap direction that divide the from a lobe into a superior frontal gyrus middle frontal gyrus inferior frontal gyrus and those are going to run perpendicular to the pre central joggers so here's a superior middle and inferior frontal drivers and then the inferior frontal gyrus is just a little bit more complex so you might break it up into these three parts pars of percularis parts triangularis and pars orbitalis so i said those three run in an ap direction perpendicular to the pre-central gyrus right in front of the central sulcus which is right in front of the post central gyrus you have to think about the medial surface of the hemisphere when you're thinking about the frontal lobe as well so the medial surface is formed by the medial surface of the superior frontal gyrus anterior half of the pericentral lobule and the cingulate gyrus so here here we go on the medial hemisphere you can see this very large superior frontal gyrus the medial portion of that and that comes back and here is that paracentral lobule and the anterior half of that is the end of the frontal lobe there and just to remind you the cingulate and the superior frontal gi right wrap around the genie of the corpus callosum here and the parent terminal and parapha olfactory gyrosit below the rostrum of the corpus callosum in front of that lamina terminalis so i'm sure as you read about surgical approaches into the third ventricular space there's a well-described approach that goes through that limb and the terminology temporal lobe so same thing if you imagine laying three your first three fingers about where the temporal lobe would be that's a good way to think about the the basic anatomy of the temporal lobe here so there's two transverse sulci dividing it into a superior frontal i'm sorry superior temporal gyrus middle temporal and inferior temporal gyrus there transverse or hessel's gyrus runs interlaterally over the superior aspect of the superior temporal gyre so heschel's gyrus is kind of up here on top of the superior temporal drivers kind of tucked in the sylvian fissure a little bit more so medial you also have to think about the medial surface of the temporal lobe so that's formed by the rounded medial surface of the hippocampal gyrus and the ankus that you can see in the picture down here there are sort of three major gyroid or strips there's the para hippocampal gyrus inferiorly it didn't take gyrus more medially and then the fimbriae of the fornix the peripheral gyrus projects medially along the edge of the tentorium and forms a large part of the basal surface of that temporal lobe the ocus is immediately pointing anterior part of that para hippocampal gyrus and we'll look at that in some uh pictures down down the road here all right parietal lobe so the parietal lobe uh back here uh consists of a large transverse interparietal sulcus that divides it into a superior parietal lobule and an inferior parietal lobule and for the most part we think of the inferior parietal lobule consisting of that super marginal gyrus right here which caps that sylvian fissure and then the angular gyrus that caps that superior temporal sulcus all right occipital lobe the occipital convexity is is not as well defined and well separated by clearly defined sulci most consistent sulcus is the lateral occipital sulcus that divides the superior and inferior occipital gyri and we'll look at that from the medial surface in a second as well so immediately the occipital lobe is separated from the parietal lobe by a parietal occipital sulcus the calcium fissure extends forward and divides the occipital lobe into the cuneous and lingua on the medial surface of the hemisphere i just wanted to point out this one particular structure the marginal sulcus is a radial sulcus off of the end of the cingulate sulcus that separates the para central lobule from the precuneus so if you think about that cingulate sulcus coming back it swings up and becomes a marginal sulcus and i just point that out because a lot of times on mris when we're looking at pathology we're trying to figure out where the primary sensory cortex for leg is and the primary motor cortex and if you can find that marginal sulcus that loops up right behind that primary sensory cortex so it's a usually a pretty prominent sulcus that you can find and it can help you find this eloquent cortex all right so quick overview of some of the cortical structures of course uh there's a lot more to it than that but that's a a quick introduction to it so what about some of the functions of some of these areas we just quickly touched on primary sensory so the primary sensory cortex is here in this kind of bluish color right behind the central sulcus that primary sensory cortex located in the post-central gyrus of the parietal lobe and posterior paracentral lobule so you're going to see references to broadman areas i think these are a little bit outdated but since they crop up a lot i left them in this in this lecture so this primary sensory cortex is broadband areas one two and three the sensory cortex receives fibers largely from the vpl and vpn nuclei of the thalamus convey general sensory like touch pain temperature proprioception and vibration and also receives visual fibers from the contralateral primary sensory cortex through the corpus callosum so remember the primary sensory cortex has a sensory homunculus that represents that contralateral half of the body and so there's a good reminder of what that homunculus looks like for the somatosentry cortex you can see where hand and face are located a bit more laterally leg more medial so there's a disproportionately large representation of face lips hand thumb index finger places where you want really high discriminative touch uh pharynx tongue jaw they're more ventral leg and foot on the medial surface just above the cingulate gyrus and face and tongue are represented bilaterally so we think of this as primarily representing the contralateral side but keep in mind that face has a very strong robust bilateral input and that's why you can sometimes resect a face sensory or face motor and the patient may not have any deficits the problem though is once you get beyond that into the rest of the primary motor cortex you you start to have significant obvious deficits primary sensory cortex or ablation of this area will result in immediate loss of sensory modalities but pain and temperature sensations can return and that's thought to be primarily uh due to the thalamic input therefore you're left with complete loss of discriminative touch proprioception but you can continue to have a crude awareness of pain i'm sure you'd probably have come across the lamic pain syndromes especially for example in stroke patients so uh when we think about all these sensory cortices remember there's always um association or secondary cortices for all of these uh primary sensory courtesy so there's a very robust sensory association cortex for primary sensory i'm going to let you guys just read through some of that but just uh keep the concept in mind and and then you can read through this to kind of think a little bit more about uh the relevance of it with regards to function and what happens when you lesion those areas how about the visual sensation so primary visual cortex so we've uh introduced that a little bit back here in the occipital lobe so the calcarine gyrus on the medial surface of the lobe uh this is split by the calcan sulcus that's brodman's area 17. you probably have come across this prominent band of white matter called the band of janari this very thickened layer 4 in the cortex so remember most cortex layers have six layers receives the visual cortex receives fibers from the lateral geniculate each visual cortex receives input from the ipsilateral half of each retina representing the contralateral visual field so if you look at the color schemes here just to point out the area below the calcarine fissure that corresponds to the visual field superiorly and then as you get closer to the pole of the occipital lobe you get closer to where central vision is located and then remember that uh it represents a contralateral visual field so this is the right hemisphere and this is shown in the left visual field for those so i'm sure you all remember you know the entire visual pathway so this is important to learn very well because it's one of the longest pathways through the brain where a lot of pathology can interfere with it so if you have a good grasp of that visual pathway and you can understand the visual deficits that come from pathology along that pathway then that can really help you localize and so i'm sure you all will recognize this sort of chart where they've mapped out the visual pathways where deca states where it comes back to the lateral genetic nucleus and then you have the optic radiations that swing out into the temporal lobe and then swing up into the parietal lobe and if you have lesions at various places you're going to have a very characteristic visual field defect so this is a very important uh a bit of information to study and learn very well and so i i encourage you to spend a little bit more time on this so as a couple examples e represents those optic radiations that swing out into the temporal lobe and so if you have a temporal lobe lesion out there you get this characteristic visual field deficit or this pie in the sky deficit a superior contralateral quadrantinopsium f is meant to represent a lesion in the optic radiations as they swing up into the parietal lobe and so f gives you this sort of visual field defect where you have a inferior quadrant tenopsia on the contralateral side so anyway make sure you you know these pathways very well it can go a long ways in helping you localize lesions after examining patients so a bit more about the primary visual cortex lesions produce visual field defects in the contralateral visual field lesions inferior of the of the calcium fissure i give you a contralateral quadrantinopsia lesions of the whole visual cortex in one hemisphere result in loss of vision in the contralateral visual field if the lesion is vascular for example occlusion of a pca that patient might actually have macular staring or sparing of their central vision because that very critical eloquent cortex receives collateral blood supply also from the mca distribution so again there's secondary visual areas and i'll let you guys study that on your own time how about um auditory cortex so the primary auditory cortex is located here like i mentioned earlier that's the transverse temporal gyrus effectual broadman areas 4142 it's in the temporal lobe within the sylvian fissure so you really need to open up the sylvian fissure to access it that receives input from the medial geniculate nucleus receives input from both ears but predominantly the contralateral cortical organization is columnar based on iso frequency strips so we if you really dive into the micro anatomy uh most of the sensory quartz cortices have some sort of columnar structure from superficial to more deeper areas in the cortex you're probably most familiar with that six-layer structure that you see in the visual cortex that's very well mapped out well there's also a similar columnar structure based on frequency per audition and there's a similar theme with some of the other cortices so there are several areas that have important connections to the primary auditory cortex lesions of the auditory cortex result in impairment of sound localization um so that makes sense uh you'll have decreased hearing bilaterally but a little bit worse than the contralateral side and again there's association cortex around that primary auditory cortex there's a gustatory cortex located here for taste so that's the cortical receptive area for taste in the parietal uh curcumin near the sensory areas for tongue and pharynx so that kind of makes sense uh seizures in that area are associated with gustatory hallucinations that area receives input from the vpm of the thalamus and lesions there can affect taste as you might think olfactory cortex so this is uh often referred to as the puriform cortex located here and the peria amygdaloid area located in the medial temp tip of the temporal lobe and that receives inputs from the lateral olfactory strias so there's the olfactory bulb track coming back there's a lateral effector history as well as a medial olfactory stream it's the only sensory cortex in which fibers reach cortex without passing through the thalamus and of course you might remind yourself of the very robust connection of this sensory cortex with that very complex limbic system that you've studied hey everyone ryan rad here from neurosurgerytraining.org if you like that video subscribe and donate to keep our content available for medical students across the world