They are also important for learning, memory, and emotion. The occipital lobe is located at the back of the head behind the parietal and temporal lobes. The occipital lobe analyzes visual information from the retina and then processes that information. If the occipital lobe becomes damaged, a person could become blind, even if his or her eyes continue to function normally. The cerebellum is located at the back of the head underneath the occipital and temporal lobes. The cerebellum creates automatic programs so we can make complex movements without thinking.
The brain stem is located underneath the temporal lobes and extended down to the spinal cord. It is critical for survival because it connects the brain with the spinal cord. The top portion of the brainstem is called the midbrain. The midbrain is a small portion of the brain stem located at the top of the brain stem. The visual input comes in from the retina.
There is a smaller route that's more prominent in the large mammals. It was actually discovered first in the chimp. But then they looked with more sensitive methods and they realized it's even there in the rat. A pathway directly from the dorsal cochlear nucleus to the medial geniculate body. But then there's a route that we MP3) may be older, that is here in gray. I show it coming from the trapezoid body primarily. Which gets its input, many neurons in the trapezoid body region here, which contains a lot of crossing fibers related to the auditory system.
That travels through the reticular formation also to these nuclei at the lateral lemniscus. The axons continue forward through the midbrain, some of them go into the superior colliculus. They don't terminate in the main nucleus of the medial geniculus. They terminate in cells around it, including many cells that are multi-modal. There are uni-modal regions, too. This It's just called part of the posterior group of nuclei. But it includes a nucleus that's called the medial nucleus of the medial geniculate body.
I just want to say a little more about the eighth nerve. You know that axons representing different frequencies terminate in this organized way in the two nuclei. The nerve comes in from below. And then a similar thing happens in the ventral cochlear nuclei, anterior and posterior divisions, and in the dorsal cochlear nucleus.
Where axons from different parts of the basilar membrane, different parts of the cochlea, terminate at different levels. So if you penetrate this way, you'd see the representational frequency. Now if you look at one of these axons, it travels rostrocaudally through the nucleus. This would be like those rostrocaudal axons that I just showed you along here. He still comes to talks here.
I met him just the other day. He did a lot of this work on the eighth nerve. And what he's showing in this picture is different cell types in the ventral cochlear nucleus. And he investigated how these respond to a pulse of sound, graphed here. This is the tone burst. And here's how the eighth nerve axon responds. A lot of the action potential is right at the beginning. And then it sort of levels off at a lower level.
And you'll note here, if you look at the responses of these cells, there's one type that pretty much matches this. They call it a primary-like post-synaptic train of action potentials. So my question is, how can that happen? Because normally, no matter where you are in the central nervous system, cells don't fire when there's only one action potential. There's got to be a lot of summation. Either it's ready to fire because there's a lot of other excitatory input coming in.
There's also some spontaneous activity. And if it's near the point where it's going to fire anyway and it might fire a little earlier if there's input. But how does this happen reliably?
And why is reliability so important for those nerves? It's important because it's used as a cue to position in space. Because the input from the two ears is compared. And I talk about the chick system, because it's a little simpler than the mammal and it's been easier to study.
The studies are better for the chick than they are for the mammal. You've got to know what the endbulb of Held is. These are endings of eight nerve axons on some of these cells.
Cells like this, they're spherical bushy cells. In the chick they're just balled cells. During development they have a lot of dendrites. They pull them all in with development. And this terminal distributes over the cell like a cup. There's a similar ending in trapezoid body that's called the Calyx of Held.
They were both described by this anatomist Held. I used to call it the Calyx of Held and the cochlear nucleus. But then I read the history and realized that he actually described the one in the trapezoid body. He also described this one, but didn't call it calyx. So people call it the endbulb of Held. But you can see what's happening here.
It forms multiple synapses. So many different synapses in one bump, one terminal enlargement. That means with the action potential one pulse here arrives.
It causes simultaneous depolarization at many different points in that membrane. So they all summate here at the axon hillock, and you end up with one action potential coming out. That's pretty unusual in the sense of central nervous system. These are just another summary of these connections through the thalamus. And these are the summary of the thalamic projects then.
Of course, the medial geniculate body projects to the auditory cortex in the temporal lobe. You also get projections to nearby areas from those posterior nuclei that are getting auditory input. That's why when I diagram this this way, I show that these neurons outside of principle nucleus, in the medial geniculate body, I show them going to area Whereas these other cells go primarily to the other areas, especially the areas ventral to the auditory cortex.
These also get transferred connections from the auditory cortex. Just remember that cells here and the medial geniculate body send axons that go not only to neocortex, but also into the amygdala, the lateral nucleus and amygdala. And I mentioned there are some visual projections like that too, to that lateral nucleus, the amygdala. And that's proved to be pretty important in learned fear in studies primarily of the rat. This is what we've just looked at.
And I think I just answered this question, why do some of the auditory nerve axons that terminate in the ventricle of the nucleus end in a giant terminal enlargement? To answer that you have to describe that endbulb of Held. What function does it serve? Can we get enough spatial summation so so one action potential results in one output action potential? And you need to know what the trapezoid body is. In pictures like this, I just show it as down here.
But if you looked at a cross section-- I really should have a mammalian cross section here, but they're easy to find. You find that the cells here, especially in the ventral cochlear nucleus, project to both sides, into cell groups in the trapezoid body. There's a medial nucleus trapezoid body and lateral nucleus trapezoid body.
And there you have, in mammals, there is another big Calyx of Held that preserves that one-on-one response to auditory input in generating the location information. Let's look at it in the chick. Coincidence detectors is a good term for it. I created this table because some people have a terrible time if they only see the drawings. They got to have it all spelled out in words, so I created the table. All I'm doing here is putting words to those pictures that we've already gone over.
So now we'll follow the pathways involved in these two functions. We'll begin with the sound localization, which involves that precise timing we were just talking about. The pathway that is generating these differences, depending on where the sound is coming from in the azimuthal plane. One of the major outputs is to the superior colliculus, where you have a map of the auditory world. The spatial map, that is neurons respond best to sounds coming from a certain position in space.
And that position in space matches the area where the visual input is also triggering closer to the surface. MP3) auditory input is coming in to the middle layers of the colliculus.
Somatosensory inputs are coming into the deeper layers, most of them below the auditory. And there you get a spatial map, too. Think of the coverage of the field around the animal's head by those enormous whiskers, the mystacial vibrissae of rodents.
They protrude out into the visual field. So yeah, you're only dealing with the space right next to the head. But that still matches the things they see beyond that. So they can anticipate something coming at them.
They can anticipate a stimulus in the whisker that's located in the same area. And then when we deal with pattern identification, that pathway from the dorsal cochlear nucleus goes directly to the thalamus, also by way of the inferior colliculus. But some of them go directly, and then to the endbrain.
And most of the analysis of temporal patterns happens in the cortex. So for location, I have here the eighth nerve. You go to the ventral cochlear nucleus. And these are the structures of the trapezoid body. So superior olive, and that's where you get neurons projecting to a number of places, including the cerebellum.
Even though the cerebellum. And then from there you go to the nuclei, the lateral lemniscus, and inferior colliculus as we'll see, and the superior colliculus. Which itself, as we know, has projections into the lateral thalamus. So in mammals it's the medial superior olive which is sensitive to precise time of arrival. That's just representing azimuthal position.
I mean, the timing doesn't actually help the animal discriminate sounds above the horizontal plane or below. They need other ways to do that.
It's not as accurate. But by simple head movements they can generate cues. And because of the shape of the pinnae, the pinnae attenuate different sound frequencies differently, according to elevation. So the sound actually has a slightly different effect on different neurons. And that is used in localization in the vertical plane.
That's been studied in owls, where just the configuration of the feathers around the ears create those differences. I don't know as much about that. It's not been as well studied. But we do know that there is a map in the vertical dimension as well as in the azimuthal direction. So let me go through those studies in chickens. We've talked about this endbulb. That is here in this diagram of one neuron type on both sides in the cochlear nucleus of the chicken. So here's the axon coming in from the organ of Corti in the cochlea on the left side, and then on the right side.
Here's the endbulb of Held. So we know every action potential coming in here leads to one here. Most times, whenever you see photos of the brain, you are looking at the cerebral cortex. This area houses the brain's "gray matter," and is considered the "seat" of human consciousness.
Higher brain functions such as thinking, reasoning, planning, emotion, memory, the processing of sensory information and speech all happen in the cerebral cortex. In other words, the cerebral cortex is what sets humans apart from other species. The cerebral cortex is referred to as "gray matter," due to its color and is responsible for several vital functions, such as those listed above.
The cerebrum's inner core houses the brain's "white matter. The corpus callosum is a thick tract of fibrous nerves that serve as a kind of switchboard enabling the brain's hemispheres to communicate with one another.
Whereas the cerebral cortex is the cerebrum's outer layer made up of gray matter, and is responsible for thinking, motor function and information processing; the corpus callosum is the cerebrum's inner core, made up of white matter, with four parts of nerve tracts connecting to different parts of the hemispheres. Home of the white matter: corpus callosum. The corpus callosum's nerve fibers or axons are coated with myelin.
This fatty substance helps increase the transmission of information between the next part of the cerebrum: the two hemispheres. In addition to two layers, the cerebrum also has two halves, or hemispheres: the left hemisphere and the right hemisphere. Although each hemisphere is known for managing different functions, it is important to note that both handle most processes of the brain structure.
The existence of the hemispheres MP3) vital to our body's functions. The relationship between our brain and body is contralateral. This means, generally speaking, that the left side of the brain left hemisphere controls the right side of the body, and the right side of the brain right hemisphere controls the left side of the body. Because the hemispheres carry out different tasks, they need to "talk" to one another in real time to coordinate our movements, thoughts, etc.
The left hemisphere is responsible for controlling the right side of the body. It handles language, reasoning, logic and speech. If the left hemisphere were a set of classes in school, it would be your math, science, and English classes. The right hemisphere is responsible for controlling the left side of the body. It handles spatially-related tasks and visual understanding. In terms of classes, the right hemisphere would be your arts, music, and creative writing classes.
The deep groove separating the hemispheres is called the longitudinal fissure or, cerebral fissure. The longitudinal fissure is prevented from completely splitting the cerebrum in half by the corpus callosum. Thanks to the corpus callosum our brain's speedy switchboardthe left side of your brain can chat instantaneously with the right side of your brain.
Pieces Of Brain (Edit) - Andy The Core & Sei2ure - Pieces Of Brain (File red line down the center of the cerebrum is the longitudinal fissure.
The cerebrum's left and right hemispheres are each divided into four lobes: the frontal, parietal, occipital and temporal lobes. The lobes generally handle different functions, but much like the hemispheres, the lobes don't function alone. The lobes are separated from each other by depressions in the cortex known as sulcus or sulci and are protected by the skull with bones named after their corresponding lobes.
The frontal lobe is located in the front of the brain, running from your forehead to your ears. It is responsible for problem-solving and planning, thought, behavior, speech, memory and movement. The frontal lobe is separated from the parietal lobe by the central sulcus and is protected by a singular frontal skull bone. The parietal lobe picks up where the frontal lobe ends and goes until the mid-back part of the brain about where a ponytail would be.
It is responsible for processing information from the senses touch, sight, hearing, smelling and sightas well as language interpretation and spatial perception. It is separated from the other lobes on all four sides: from the frontal lobe by central sulcus; from the opposite hemisphere by the longitudinal fissure; from the occipital lobe by parieto-occipital sulcus; and from the temporal lobe below by a depression known as the lateral sulcus, or lateral fissure.
Because each hemisphere has a parietal lobe, there are two parietal skull bones—one on the external side of each hemisphere. The occipital lobe is located in the back of Pieces Of Brain (Edit) - Andy The Core & Sei2ure - Pieces Of Brain (File brain. It is considered the brain's "visual processing center" because it's where the bulk of information our eyes take in gets analyzed and sorted. It is separated from the parietal lobe by the parieto-occipital sulcus; from the temporal lobe by the lateral occipital sulcus; and from the cerebellum the second part of the brain, coming up soon by what is called the cerebellar tentorium or tentorium cerebelli.
It is protected by the skull's singular occipital bone. The temporal lobe is located in behind and below the frontal lobe and beneath the parietal lobeunder the lateral fissure. It is responsible for our memory, emotions, language and speech, and auditory and visual processing. It is separated from the parietal and frontal lobe by the lateral sulcus lateral fissure ; from the occipital lobe by the lateral occipital sulcus and occipitotemporal sulcus; and is adjacent to the corpus callosum.
Similar to its parietal neighbor, the temporal lobe is protected by two bones—one temporal bone on the external side of each hemisphere. The brain's lobes serve as a map for understanding where brain functions happen. The cerebellum stands for "little brain" in Latin. It looks like a separate mini-brain behind and underneath the cerebrum beneath the temporal and occipital lobes and above the brain stem.
The cerebellum along with the brain stem is considered evolutionarily to be the oldest part of the brain.
The cranium protects the brain from injury. Together, the cranium and bones that protect the face are called the skull. Between the skull and brain is the meninges, which consist of three layers of tissue that cover and protect the brain and spinal cord.
From the outermost layer inward they are: the dura mater, arachnoid and pia mater. Dura Mater: In the brain, the dura mater is made up of two layers of whitish, nonelastic film or membrane.
The outer layer is called the periosteum. An inner layer, the dura, lines the inside of the entire skull and creates little folds or compartments in which parts of the brain are protected and secured. The two special folds of the dura in the brain are called the falx and the tentorium. The falx separates the right and left half of the brain and the tentorium separates the upper and lower parts of the brain.
Arachnoid: The second layer of the meninges is the arachnoid. This membrane is thin and delicate and covers the entire brain. There is a space between the dura and the arachnoid membranes that is called the subdural space. The arachnoid is made up of delicate, elastic tissue and blood vessels of varying sizes. Pia Mater: The layer of meninges closest to the surface of the brain is called the pia mater. The pia mater has many blood vessels that reach deep into the surface of the brain.
The pia, which covers the entire surface of the brain, follows the folds of the brain. The major arteries supplying the brain provide the pia with its blood vessels.
The space that separates the arachnoid and the pia is called the subarachnoid space. It is within this area that cerebrospinal fluid flows. Cerebrospinal fluid CSF is found within the brain and surrounds the brain and the spinal cord. It is a clear, watery substance that helps to cushion the brain and spinal cord from injury.
This fluid circulates through channels around the spinal cord and brain, constantly being absorbed and replenished. It is within hollow channels in the brain, called ventricles, that the fluid is produced. A specialized structure within each ventricle, called the choroid plexus, is responsible for the majority of CSF production.
The brain normally maintains a balance between the amount of CSF that is absorbed and the amount that is produced. However, disruptions in this system may occur. The ventricular system is divided into four cavities called ventricles, which are connected by a series of holes, called foramen, and tubes.
Two ventricles enclosed in the cerebral hemispheres are called the lateral ventricles first and second. They each communicate with the third ventricle through a separate opening called the Foramen of Munro.
The third ventricle is in the center of the brain, and its walls are made up of the thalamus and hypothalamus. The third ventricle connects with the fourth ventricle through a long tube called the Aqueduct of Sylvius. CSF flowing through the fourth ventricle flows around the brain and spinal cord by passing through another series of openings. The brainstem is the lower extension of the brain, located Pieces Of Brain (Edit) - Andy The Core & Sei2ure - Pieces Of Brain (File front of the cerebellum and connected to the spinal cord.
It consists of three structures: the midbrain, pons and medulla oblongata. It serves as a relay station, passing messages back and forth between various parts of the body and the cerebral cortex. Many simple or primitive functions that are essential for survival are located here.
The midbrain is an important center for ocular motion while the pons is involved with coordinating eye and facial movements, facial sensation, hearing and balance. The medulla oblongata controls breathing, blood pressure, heart rhythms and swallowing. Messages from the cortex to the spinal cord and nerves that branch from the spinal cord are sent through the pons and the brainstem.
Destruction of these regions of the brain will cause "brain death.
Terror Squad presents DJ Khaled - Listennn - The Album (Clean) (CD, Album), Let Her And Let Go - Blues Traveler - 25 (CD), Tema Y Variaciones - Fusioon - Fusioon (Vinyl, LP, Album), Snake Eyes Boogie - L.A. Guns - Hollywood Vampires (Vinyl, LP, Album), Michael, Families - Lou Reed - The Bells (Vinyl, LP, Album), Dont Wanna Let You Go - Various - 3FM Megahits 2000 Nr 4 (CD), La Denigración - Bowerbirds - Hymns For A Dark Horse (CD, Album), Dominik von Werdt - Emerged EP (File, MP3), The Big Country, The Outer Skin - The Hope Blister - ...Smiles OK (CD, Album), Γράψε Λάθος, Oude Man - Mensenkinderen - Het Lied Van Schijn En Wezen (CD, Album), Madonna - Like A Virgin (Cassette, Album)