okay now that we have talked about uh the structure of the nervous system generally we're going to delve into specific structures specifically within the brain today uh and their structure function relationships so we've got this image here and we're going to kind of move through this uh today and what you can see is that there's an organization of the brain um in sort of a stacked fashion okay and it's running from telencephalon to diencephalon De mesencephalon met encephalin myencephalon and then you get to spinal cord and uh one of the ways to memorize the order of these uh is that they're actually in alphabetical order with the exception of the uppermost layer the telencephalon and you can remember that by thinking tell encephalon T for top and then everything else is in alphabetical order diencephalon mesencephalon meth encephalon Etc so uh the brain as it evolved over time uh it evolved let me get my laser pointer out here from a sort of inside out I used I used uh the analogy earlier of like a rubber band ball that you're building uh you know you start with a couple of rubber bands and you keep adding rubber bands and adding rubber bands and it gets bigger and bigger that's exactly how the brain evolved and so what we'll see is that the deepest structures within the brain uh of the middle of the brain and and the brain stem in particular are the structures that are the most basic the most primitive and the most necessary for survival they take care of um breathing and heart rate and all sorts of automatic functions that are critical for survival everything else is kind of a stacked layer on top of that that has allowed us to enhance emotion cognition memory but technically you could really do do away with many of the upper layers of the brain and just leave the midbrain and the brain stem and technically you'd be able to survive you likely wouldn't be conscious anymore or able to have higher ordered cognition but you could survive so anyway everything evolved from inside out in that sort of fashion adding layers and the uppermost layer is what we call the cortex and that is where all of your your higher ordered thought processing is occurring Association Etc and so we're going to start at the level of the telencephalon today and we'll talk about the forebrain region and we'll work our way down from there foreign so uh when we talk about the forebrain particularly the tell encephalon you know we saw that it includes the cortex the limbic system uh Etc and these are areas again limbic system is associated with emotion we'll talk about that later but particularly the cortex and in the forebrain the cortex of the frontal lobe is really associated with personality personality decision making metacognition it's who you are and how you control your yourself right and by that I mean control your impulses and so we've got a couple of examples here this is from a case study from 2011 in Nature Neuroscience about an individual uh he's in his 30s he's graduated college uh and then he gets a job uh in you know as a comptroller he's doing really well for himself uh making good money um he's married uh you know he's he's set up the whole life that he wants for himself at age 35 he gets diagnosed with a brain tumor and what we see is that within months of that brain tumor uh he has an operation to remove it but during that time something happens and within months of this all of a sudden Elliot changes extremely quickly he quits his job uh begin he loses money gambling uh and he divorces his wife uh loses family and friends and winds up remarrying a sex worker that he'd only known for a month so uh we see this rapid change in behavior from somebody that was initially very much in control uh able to delay gratification able to um build a life to gain what he wanted and all of a sudden he becomes this impulsive uh person who you know loses everything that he had built for himself and so if we had to guess we would say that Elliot's brain tumor was probably in the frontal lobe more than likely in the prefrontal cortical area and as that is where the majority of again decision making and inhibiting of impulse behaviors occurs another classical example that follows a very similar story this is when we initially as a field the field of psychology the field of physiology Neuroscience begins to get an idea in the 1800s of the importance of the of the forebrain and particularly the prefrontal cortex uh in terms of personality so many of you I'm sure may have heard this story already this is the case of Phineas Gage Phineas Gage was a railroad worker and at this time in the United States uh people were using a lot of dynamite TNT to blast through mountains Etc while building the railroads and he just so happens to be in the wrong place at the wrong time and a railroad spike gets blown through his head particularly through the orbital socket of his skull you can see that here straight up through the orbital socket of his skull and it pierces through a large portion of prefrontal Cortex now again this portion of the brain that's damaged you know is not critical for survival so it's not going to affect Elliot's ability to breathe or or you know live necessarily but again it is critical for personality um and so we see very similar results here with Phineas Gage as to the previous story you know he becomes a very impulsive person who is unable to control his emotional impulses he becomes violent with people he begins gambling loses his money he's sexually impulsive Etc and his life just sort of unravels so the prefrontal cortex is like this sort of guardian angel over the brain it's the part of the brain that tells you when somebody cuts you off in traffic and you have that emotional impulse you think boy I'd like to go hit that guy the prefrontal cortex is what tells you hey wait stop there might be consequences for doing that right so you damage it you lose that inhibitory control and bad things tend to happen we might also Imagine then what this tells us about uh individuals who are violent recidivists in prison the prison population is just filled with individuals who are habitual violent offenders people who have difficulty controlling their uh their emotional outbursts Etc and it suggests that many of these people might be individuals with a reduced functioning of the prefrontal cortex and in fact that's proposed to underlie much of of uh what's what's called psychopathy and or sociopathy it gets a little bit more um complex than that but it's certainly a part of the puzzle let's talk more about the cortex specifically obviously the cortex is more than just in the you know the frontal frontal lobe and prefrontal cortex it's all over the brain right well the cortex has six layers so it is a layered structure much like the brain itself is a layered structure but the cortex has six distinct layers okay so the deepest layers uh layer six and then moving upward to the outside so six five four three two one and uh these layers are categorized by the presence of various cell types particularly in layers three and layers five there are these large pyramidal shaped cell bodies of neurons and they're called pyramid cells or pyramidal neurons they are large neurons with these apical dendrites which send information up and down through the cerebral cortex so they are large glutamatergic neurons that are doing this and beneath them beneath layer six we get into lots and lots of white matter tracks of information being sent to deeper brain structures so know that layers three and five contain the pyramidal neurons and what what's special about them the cortex itself um obviously it is the most recently evolved structure of the brain in humans it is much more advanced than in other animals and the cortex can be subdivided into various areas that have evolved sort of separately that subsume various functions there are primary sensory areas so this is where sensory information comes in from the periphery it gets routed through the thalamus which we'll talk about later and then up to these primary sensory areas and these are areas where you have the cognitive conscious realization of what it means that you are feeling something you are sensing something touching your hand and you have a cognitive rationalization of what that is that's occurring in the primary sensory areas there are also secondary sensory areas which overlap with the primary and they're integrated with the motor areas as well so motor areas of Cortex are what generate thoughts about planning of I'm going to go pick up my phone off the desk Etc and then signal the send those signals down to the spinal cord uh the the sensory areas particularly the secondary sensory areas are close by to the motor cortex areas and this makes sense um sensory information coming in from the periphery on you know about the skin the legs Etc that winds up getting used in terms of motor output and planning as well and then by by and large the majority of Cortex outside of the sensory and motor areas is devoted to what are called association areas association areas there are visual association areas auditory association areas olfactory association areas much of that is within the temporal lobes and this is because these are areas that have close connections to a structure called the hippocampus which is involved in storing episodic events into long-term memory and so association areas are areas of Cortex that are about recognizing uh rationalizing um sensory information what is that large object walking across my vision ah it's an elephant I know what do I know about elephants I know the following facts that's happening in visual association areas interacting with areas of memory storage as well uh let's talk about the limbic system now so still in the telencephalon the limbic system is primarily associated with emotion emotion not just fear but we'll begin with a discussion of fear I have three of my favorite horror films here and there's a particular structure in a limbic system that's associated with fear that we'll talk about but there are other emotional impulses which are derived from the limbic system as well so the amygdala the amygdala this structure is critical for fear for learning fear impulses and it's a it is a bilateral Walnut sort of shaped structure uh deep within uh the telencephalon and again it's critical for learning fear to be afraid of something if you remove the amygdala you will find the individuals display a lack of fear towards stimuli that they should be afraid of so uh there are studies showing you know damage to the limbic system bilateral damage to the temporal lobes which include the limbic system and that produces syndromes in animals Etc where you know uh they display no fear to PR to Predators Etc um but it's also critical for allowing us to diagnose fear in others you know if you don't have an amygdala or you have an improperly functioning amygdala if you can't experience fear you can't properly diagnose fear in others either and this is a great study from 1994 that demonstrates that so these are individuals with a disease called erbach wife disease uh it leads to calcification of the temporal lobes particularly the amygdala it's a very rare disease but you'll see in these individuals this disrupted capacity to experience and diagnose fear and so what they did with these individuals is they showed them a series of pictures of faces various emotions and they asked them to tell the researcher what emotion is the subject in the pictures experiencing and so what you have on this graph are the Open Circles are control subjects that do not have amygdala damage and the black triangles are the individuals with herbic white disease that have the amygdala damage let's take a look they have no trouble diagnosing the happy face okay so the amygdala is probably not involved in happiness emotions they have some difficulty diagnosing the surprised face this is uh kind of interesting and it makes sense in a way because often things that we are initially become afraid of surprise us right you think about watching certain horror movies they call them jump scares uh it's something unexpected it surprises you and then you're afraid of it surprise often precedes fear and so they are related emotions and so it's not surprising that uh individuals with amygdala damage would have issues diagnosing surprise finally take a look at our fearful face they just completely uh have have much much difficulty diagnosing that anger uh not so much issue there no issues uh discussed uh not so much of an issue there and sadness not so much there so it's primarily the surprise and fearful component so let's move on to another critical structure in the limbic system and you know not so much emotion here but as I've already alluded in this course long-term storage of memory it's kind of like the librarian you take the book in The Librarian says okay it's this subject matter it belongs in this category on this shelf over here with these other books that are about it so the hippocampus is not where memories are stored rather it's where episodic events are diagnosed for the qualities and qualia that they contain and then shipped off to appropriate areas of long-term storage in the cortex with related memories there's another function of the hippocampus that's critical as well however and that's cognitive mapping cognitive mapping the hippocampus is critical for memorizing roots in your environment so here's an interesting study of taxi drivers now today uh this study you know wouldn't work because people you know Uber drivers Etc they all have their phone set with GPS in the car and many of us uh tend to be pretty poor at navigational skills these days because we rely on GPS in our phones more than anything uh but you know before everybody had a GPS in their pocket uh somebody like a taxi driver you know you would have needed a map to find your way around but a map is Not Practical for a taxi driver they need to be able to know just intimately know the roots around cities and particularly this this study was done with London taxi drivers London has a complex Maze of one-way streets Etc and it really would behoove you to know all the roots and there's many of them if you're going to be an efficient Taxi Driver what you see is that individuals who are taxi drivers they measured the volume of their hippocampus in these individuals using um using fmri and what they find is that dependent on how long this individual has been working as a taxi driver you can see here on the on the x-axis it's number of months you've been working as a taxi driver on the y-axis it's showing volume of the hippocampus and what you see is that there is a positive linear correlation with number of months you've worked as a taxi driver and volume of the hippocampus the more time you've spent working as a taxi driver the larger your hippocampus is likely to be now you might be asking yourself well is this a chicken or egg situation do people with larger hippocampuses just naturally gravitate toward being taxi drivers the answer is no uh this is a this is an issue of neuroplasticity we know this because you can do experiments with people using fmri where you train them on various tasks say video games or something people who play a lot of first-person shooter video games like Call of Duty Etc wind up with larger hippocampal volume as well after playing the game for a certain amount of months to years because that also involves memorizing roots to be efficient in game memorizing Maps so that you can efficiently navigate around and win the game and and be better at it than somebody that doesn't know the area quite as well it's the same sort of process and you can show this over a period of months the brain can change right as you learn and if you stop playing the game over time it might imagine you lose that hippocampal volume as well so that's the telencephalon we're now going to move on to the diencephalon which contains the thalamus and the hypothalamus so I've already mentioned this in the class but we're going to go over it again here just briefly the thalamus is this deep brain structure situated right in the middle of everything okay it's it's right in the middle of everything and that's the perfect place for it to be because it interfaces with pretty much all everywhere all over the brain and all over the cortex the job of the thalamus is to receive incoming sensory information that is coming up from the brain stem in terms of touch proprioception coming in from the nose coming in from the eyes coming in from the ears and then diagnose that information for what it is whether it is tactile information gustatory information auditory Visual and Route it to the appropriate sensory Association cortices so we talked about this in the context of LSD psilocybin other psychedelic hallucinogens how they inhibit portions of the thalamus that are involved in this and this is why you can wind up with anesthesia on those drugs the thalamus from its uh position in the middle of the brain it sends information to areas of the cortex through What's called the internal capsule the internal capsule all the internal capsule is is just bundles of wires big bundles of white matter tract wires running through the inside of the brain uh from the from the middle portions from the thalamus and the basal ganglia we'll talk about the basal ganglia in a minute to the cortex and it creates a structure which is called the corona radiata Corona radiata so it's just a big bundle of wires that's the internal capsule and it spreads out and sends information all over the cortex that's called the corona radiata let's talk about the hypothalamus okay hypothalamus is technically it's still a part of the limbic system uh Thalamus we would not consider part of the limbic system but hypothalamus we do um in the sense that it is still involved in emotions and drives particularly drives would be the word that I would use we used to call it the four F's fighting feeding fleeing and sexual impulses all of those are generated uh many of them are generated at the level of the hypothalamus and here we can see um one of the key roles of the hypothalamus is in regulating feeding and satiety signals if you lesion parts of the hypothalamus you will remove satiety signals the part of your brain that tells you okay I've eaten enough I'm satiated it's time to stop eating you will remove that and so here we see obesity in rats this is a rat that's had a lesion of a particular area of the thalamus that controls satiety signals and it produces this uh obesity result so the hypothalamus controls feeding and satiety signals but it also controls aspects of the fight-or-flight response this is the beginning of the HPA axis the hypothalamic pituitary adrenal axis often again referred to as that fight or flight system stress system involves activation by norepinephrine Etc we talked about that in a couple lectures ago it also regulates uh the need to drink and again it regulates sexual impulses as well there are some key nuclei of the hypothalamus that are critical for sexual behaviors we'll talk about some of that stuff later but that's just some Basics on the hypothalamus we're now going to talk about the midbrain or the mesencephalon so the midbrain contains uh the basal ganglia the substantia ventral take mental area all of these things are associated with dopamine and the two dopamine paths that we talked about earlier we talked about the mesolimbicortical path and the mesostridal path for dopamine with regard to the basal ganglia we're talking about substantia Niagara to basal ganglia to striatum that's mesostradal path that's involved in habitual motor programs goal directed motor actions that become habitual motor programs the basal ganglia has several nuclei that are important to it the Globus pallidus the putamen the caudate and we would consider perhaps the substantia as well and all of these are interacting the substantia is located at the level of the midbrain particularly it sends dopamine up into the basal ganglia these nuclei here and that is what initially allows for control of goal directed motor programs and then it sends a signal up into the primary motor cortex which then gets sent down to the spine to Alpha motor neurons to cause excitation contraction coupling at the level of muscles uh other aspects of the midbrain that are important um we have What's called the tectum here's a slice of midbrain right here we're looking at the tectum tectum is Latin for roof and so it's sort of the upper roof portion of the midbrain and the tectum contains what are called the colliculi the colliculi there are uh the superior colliculi which are the upper portion and the inferior colliculi colliculi is Latin for Hills here are the colliculi on the midbrain right here they're these bump like hilly projections the superior colliculi are higher up than the inferior colliculi and these are areas uh where sensory information related to visual and auditory gets used to control reflexive movements so the superior colliculus receives information from the optic nerve and essentially and it uses that information for visual orienting you see something fly by your vision and you turn your head and Orient toward that stimulus similarly the inferior colliculus is doing the exact same thing but it's uh getting information about auditory information auditory information so information is coming in from the ears and it's used in the orienting response you hear a loud bang a loud sound uh is in a particular direction you automatically Orient towards it that's happening at the level of the inferior colliculus other important aspect of the midbrain the cerebral Aqueduct this is where CSF is going to flow through the midbrain onward down through the brain stem and then ultimately down through the middle of the spinal cord and uh this is important for so many different aspects of function right CSF flowing through this spinal cord flowing around the spinal cord we talked about that earlier in the course the cerebral Aqueduct uh it may it has a connection rasterly with the third ventricle other things happening here I already mentioned substantia we saw that uh in those slices of brain with that Parkinson's patient that black striping substantia Niagara running along the lower ventral portion of the midbrain here there's also something called the red nucleus which is just above substantia it's also involved in some aspects of movement too not so much as the substantia Niagara which sends information about voluntary movement up to basal ganglia and then up to primary motor cortex red nucleus is where information is descending from those areas part some of it's descending down to the spinal cord about movement one other area that's really notable in the midbrain and I've talked about this already is the VTA the ventral Tec metal area it's located just a little bit lower in slices of the midbrain than the substantia but what's key is that the VTA and the substantia are both made up of dopamine so they're dopaminergic hot spots about 75 percent of the VTA is composed of dopamine neurons another 15 to 20 percent is glutamate and then the rest is gabaergic neurons um so the VTA is critical for the reward circuitry in the brain okay uh reward learning and motivation that's where the dopamine projects anteriorly from the midbrain to uh the limbic system and to the funnel cortex is called the mesocortical limbic circuitry it's also the circuitry that can become hijacked in addiction all right uh let's move on to the met encephalon and the myencephalon so we're going to be talking about parts of the brain stem as well as the cerebellum here or also known as the hind brain let's begin with the cerebellum the little brain If you recall the Latin there the cerebellum functions sort of as its own little brain area and it receives information from the brain stem it also receives some information from the cortex as well and what it does is it's coordinating information about proprioception and position of the body to coordinate uh balance primarily balance but also automatic sequences programmatic sequences of movements I'm talking about things like casting a fishing rod swinging a golf club or baseball bat things that you initiate and you don't think about them once they begin you can think about them abstractly when you're not doing them you can think well I should put my shoulders in this position I should put my feet in that position but once you begin that sequence of movements really the cerebellum is taking over it's it's allowing you to carry out this sequence of movements uninterrupted and smoothly and that involves coordination of of motor impulses and balance it's also important for some very basic forms of associative conditioning we've found so there's some learning that goes on in the cerebellum as well for instance eye blink conditioning this is when you know you go to the optometrist's office and they do that test and they tell you they're going to send little puffs of air at your eye believe it or not it's not actually puff severe it's actually a needle which is coming out and touching your eye and sensing how how much pressure there is in the sclera of your eye either way uh you tend to reflexively Blink when you after the first time or so you get to a point where seeing the little light makes you uh expect that something's gonna happen and you blink you kind of back away that's happening at the level of the cerebellum and so the cerebellum is a really interesting structure it has its own Arrangement much like the cortex of the rest of the brain in terms of layers uh and it really does function almost like its own little brain we talk more about the cerebellum and other courses like clinical neuroanatomy and there's really a lot to get into there okay let's move on to the brain stem I've mentioned earlier in this course the brain stem is controlling a lot of autonomic functions related to things like respiration heartbeat um motoring pulses are getting sent down through this area as well information is coming up from the spine through this area as well but let's talk about um let's let's run through the brain stem as it is arranged now the first part of the brain stem is the midbrain we've already covered that the midbrain is the top of the brain stem the next portion of the mid of the of the brain stem the middle portion is called the pons the pons contains the uh respiratory centers in the brain so that's not all that's occurring in the ponds there's lots of other things happening there in terms of cranial nerve nuclei uh for for different aspects of functioning but certainly the respiratory areas are contained there and so if you lesion that area of the brain it can be very dangerous because you might not be able to breathe anymore other things that are going on here cranial nerve nuclei for facial sensation passing through this area some originating in this area sleep aspects of that is going on here parts of what are called the reticular formation run through the ponds they run through the midbrain and other parts of the brain stem too but the reticular formation is critical for Sleep functioning also arousal and wakefulness so a lot of that going on there and uh and then yes these other automatic functions the next level of the brainstem the lowest level of the brain stem before you get to the spinal cord is called the medulla the medulla the medulla also contains a number of nuclei for the cranial nerves that we discussed earlier in this course which are important for controlling movement of things like the eyes facial muscles chewing swallowing Etc lots of things originating at that level as well and so remember the brain stem is arranged in the following order midbrain pons medulla and so you can remember that is mpm midbrain ponds medulla and just above the midbrain since we're talking about it on this image you can see here just above the midbrain is the thalamus the thalamus is the most centrally located structure in the entirety of the brain because it routes information to various Association cortices and so uh brain stem midbrain ponds medulla and it is involved in many aspects of autonomic functioning it's also where many of the cranial nerve nuclei originate and it's also where the reticular formation which is involved in sleep wakefulness arousal and other functions uh originates