We are the brain, we are the neurons...

[Mars Man]

Both interesting bits of information. I'll later have to pull it out, but there was a paper in Science on observations of 'decisions' being made before decision was made in the aware state on human subjects. It was as though the brain was deciding which in turn led to the decision becoming recognized and other parts of the brain signaled for it. That sounds a little bit like what we see in the report on boring jobs.

Yes, Revenant san, I agree with that general conclusion. I would tend to hold back a little due to some points which seemingly need to be 'fixed' (so to speak) before moving on to the next plane. As happiness can be very correctly said to be malleable--thus flexible or in need of being forumated firstly--it more obviously is something that can be learned or unlearned.

That, it seems, at least, can give rise to the question of 'what is happiness?' which seems to rely on 'what makes the sensation of happiness.' And, in turn, the sensation of happiness can quite well be shown to be a matter of mapping as well--an acquired or learned state (due possibly in some or many cases to plasticity). This seems to make it a hard thing to put a finger on in any exact and conclusive manner--at least for now--to any absolute degree. I'd like to come back to that a bit later, however, if I may.

Picking up where I had left off, then:

So in the cochlea (that little 'snail-like' structure), we have the cilia which are the fine 'hair-like' extensions of the hair cells--both inner and outer. These, along with their support cells, rest on the basilar membrane in the organ of corti. These fine cilia stand in rows with different heights for different vibration wavelengths and are connected by super fine tip links (thread-like fibers) from the insertional plaque of one (where the ion channel is) to tip of the next lower-in-height one.

The tectorial membrane covers the cilia and even rubs (or is attached to) the outer cells, while simply covering the more-important-for-higher-quality-sound inner cells. Motion in the liquid sets the basilar membrane into 'up and down' motion, which, through a little additional process, lean the cilia. A lean towards the shorter cilia prevents the ion channels from opening, and a lean towards the taller cilia open the channels resulting in up to 100% potassium and calcium intake (K+ and Ca2+) which in turn causes potential.

I'll take it from here in the next post. . .

 

[Mars Man]

Each inner hair cell is innervated by (synapse to) around 10 auditory nerve fibers (bipolar), and each auditory nerve fiber contacts one, or at the most a few hair cells (maybe 20--which in this field is a few. Dallos, 1992) on the inner hair cells--it's a high-resolution system alikend to that of the fingertips and fovea.

The outer hair cell structures are seen as being efferent structures for a type of feed-back system. (efferent refers to information flow away from a particular structure--in this case from the superior olivary complex.)

The nerve fibers bundle and carry the conductive charges from neurotransmitter release of the hair cells along cranal nerve VIII to the ipsilateral (same side) medulla (of the Cochlear nuclei), where it synapses to Dorsal Posteroventral (horizontal localization of sound) and Anteroventral (hair cell sensitivity regulator) areas.

From here, the signal is picked up, post synaptically, and runs contralaterally (opposite side) to the superior olivary complex which also projects a smaller degree of the signal back to the ipsilateral area. Both branches run to the medial geniculate nucleus of the thalamus which sends it to auditory cortex of the temporal lobe--along with its several other associative and feedback loops. This basic 'final destination' we can kind of say, is the primary auditory cortex which lies on the superior (upper) surface of the temporal lobe ( lateral sulcus).

What we have here is that the auditory signal runs to both hemispheres--unlike that of visual and olfactory signals. However, the main bulk from the right ear runs to the left hemisphere and vice versa. There is a greater number of synapse along the route making it more complicated and putting the system at a higher malfunction risk. What happens from the primary auditory links comes next.

 

[anjusan]

I wonder why it is that most of the external stimuli from the left body gets processed in the right brain and visa versa. It seems more logical, from a biological viewpoint, that it would have developed right to right and left to left. That way if the body were damaged it could just function as a single (mono - either left or right) instead of dual (left/right) organism.

If the body can sometimes re-route stimuli from the damaged side to the undamaged side, why did it develop the initial route in the first place?

I admit to a having only a limited knowledge of biology, so perhaps this question is not valid.

Also, why is it that there are theories floating around relating to one side of the brain being more artistic and the other more pragmatic?

A quick internet search found the answer to my second question...

Left Brain, Right Brain, Whole Brain?

 

[Mars Man]

Firstly, that link was pretty good in a lot of ways. It's application was clearly directed towards a question in educating processes/models--but covered a good range of general basics. Thanks for that, anjusan chan.

Regarding the hemispheres, it's evidently a matter of hardwiring. Now why that (meaning the contralateral structure), rather than having left be left all the way, and right be right all the way, I have not idea, and have seen nothing dealing with that--it's just hardwired to build that way. It's a little, perhaps in a way, like the sex question--why heterosexual division of the gamates, when asexual (in the technical sense) is evolutionarily less costly and more effecient? Who knows?!

This also holds basically true, as far as I have learned, for the basic wiring set-up too; it's hardwired in, so the brain develops that way (in most all cases) from the get go. A lot has come and gone, as for understanding of the processing centers.

Marcello Malpighi (17th century) for example, viewed the brain as a homogeneously functioning whole--as though it were a single, large gland. Then on the other side of the spectrum we have, for example, Franz Gall (18th century) who really got the idea of 'phrenology.' Even in the late 19th century with those such as Paul Broca and Carl Wernicke (after phrenology had started to lose its appeal) there were still those that stuck with the brains inside the brain concept.

Well, to get to the present, there are general specific processing/activity centers or areas in the brain, and there is the triune build (put forth by Paul Maclean; in the 1940s and 50s) but they are not so hardlined defined, and also, on top of that, there is this thing called plasticity. This is the ability to remap (re-route) firing patterns so as to make up for loss function in one area. (We have to keep in mind that the brain is a single entity, divided firstly into two hemispheres, then further into the lobes, then systems, nuclei, gyri, and so on.

We will always find the fluff foating around, and the blurred echos of echos bouncing around. . . so it would be no surprize to hear word of any 'urban legend'-like misrepresentation of scientific findings. Regarding the hemispheric processing, that link was on the mark. The left is basically said to participate in analysis, and sequential, and the right hemisphere in synthesis and whole--as well as spatial too. (among other things) I will next continue then, with the final portions of the auditory system.

 

[anjusan]

Thank you, MM, for taking the time to look into the answer to the question I posed. I hope this isn't too off-topic. But since it seems that I have found an answer to my question, at least satisfactory enough for my present level of understanding and the amount of time and effort I wish to pursue it with, here is the link:

http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1691668&blobtype=pdf

It seems to me that this lateralization of brain processes, (AB, BA) came about as a species preservation skill to make vertebrates less predictable thus increasing the chances of survival. It seems that even though we have this dual lateralization there is still one side that is dominant. Thus providing the necessary deviance in predictability.

Anyhow, thanks for letting me drag this off on a side tangent to satisfy my question. I look forward to seeing where this thread is ultimately going. Seems to be an interesting topic.

 

[Mars Man]

That theory on the development process of lateralization may have something going for it. It's new to me. In time, I'm sure I'll come across it and any challenges against it. Again, thanks for that link. That's not really a side tangent, however, since it is within the bounds of the overall thread; so no worry.

As for where the thread is going, please do drop by and follow along, when you get the time. The basic overview is in the OP. Of course, join in whenever you wish, anjusan san. I will pick up with the auditory system information again, here.



Looking back at the earlier posts to get a refresher on the nerve routes, we come up to the primary auditory cortex (pAC). This is in a 'belt region.' There is the primary, the first level of auditory association cortex, then the second level of auditory cortex (the parabelt region). The belt regions recieve information from the primary auditory cortex and the dorsal and medial division of the medial geniculate necleus (in the thalamus).

The belt region is, in general, the secondary auditory cortex, and it deals with more complex sound than the primary cortex--in animals, species-specific calls, and humans, speech and language. This region can further be divided into a dozen or so sub-regions.



In a kind of simple explanation, the auditory cortex at large evidences two pathways to associative areas and other regions. These, somwhat like the visual pathways, appear to be the 'what' and 'where' pathways. The 'where' (spatial) runs from the pAC to the caudial (means towards the tail; sometimes simply towards the back of the head) portions of the secondary and higher-order areas then to the posterior (here more specifically equals caudal) parietal cortex (PC) then towards the dorsolateral prefrontal (dPFC) and premotor cortex--with connections running parallel from the pPC to the dPFC.

The 'what' pathway runs from the pAC to the rostral (or anterior--thus in front of) area of the upper belts to both the orbital-frontal cortex (OFC) and the ventral (stomach side--basically front) side premotor cortex (vPMC).



The ventral frontal lobe in humans is the center for the motor speech structures. We find the cytoarchitetonic areas 42 and 22 on the left temporal lobe in the human brain make important substrates for understanding and producing speech--in most cases.① These are (as the site also pointed that anjusan had provided in an above post) the Wernicke's area and teh Broca's area.

Broca's area is primarily for speech production and has close connection with some speech motor memory sheets--especially sequence memory. Wernicke's area has more to do with speech comprehension, beginning, obviously (and closer to) the belt region. It deals with recognizing complex sequences of sounds. These areas, along with retrieval and associative areas make for a large, very complex and important hard-wired set up in the (especially, but not totally only) human brain and personality.

Next, a few details of the complexity and some examples of problems that make a difference in the person--in other words, in the neuronal whole.




① As also pointed out in that site, in over 95% of right-handed people, the left is dominant for speech, and 70% in left-handed people.

 

[Mars Man]

One theory which so far has a lot going for it, is that conscious awareness is very much tied up with the language elements--be that human language or non-human 'language.' That even increases the complexity of the auditory system.

Sound waves travel out from the vibrating source at about 700 miles per hour, and those which range between aproximately 30 to 20,000 times per second, are picked up by the human system.

Changes in the air pressure transducted to the organ of corti affect the basilar membrane in different places based on frequency. This happens in a very complex manner with the peak amplitude of high frequencies affecting the basilar membrane near the base and working on down to the cochlear apex for lower frequencies. 窶｡@

This is well demonstrated by cochlear implants which restore hearing for those who have lost it due to damage to the hair cells. Elecrodes in the device stimulate the specific areas of the basilar membrane by frequency causing hearing ability which will allow many to even be able to distinguish voice patterns over the telephone.

Sounds within a frequency range that come from, say, the right, cause signals which will reach a certain point at different times. This difference in timing (interanural intensity difference), processed by the cochlear nuclei, that certain point, send signals upward to the pAC where the layout is tonotopic in nature--meaning different frequencies are projected to different areas of the cortex. In this way horizontal and vertical localization 窶｡A is 'coded' by the organ of corti and the areas of the cochlear nuclei.

With the storm of constant signaling, the auditory cortical areas are communicating with a number of other areas (as mentioned in the above post) which are all communicating with each other and others, creating what will amount to action...consciously recognizible or not.





窶｡@ Also other factors come into play as well, such as the 'tuning fork' effect of the cilia lenghts and the electrical membrane characteristics of the hair cells.
窶｡A Vertical localization is firstly differentiated by the pinna--see post #46, par. 2

 

[Mars Man]

Odorants are molecular particles that 'lock' into the receptors that they fit into--they are real objects. Sound, is not. Air consists of real objects and the compression and expansion of these make all the elements of what is taken by the brain as sound.

As I have mentioned before, with greater complexity comes greater possibility of malfunction. Along with that train of thought, it is of course most obvious that stopping up the ears, affects the brain's ability to recieve the electro-chemical input to cognize sound. Yet here are some other things that can go wrong:

Now you may recall that I had mentioned the condition of the ear being able to act as a 'speaker.' There has been one recorded case, at least, of a lady who complained of hearing wispering much of the time. No one took her seriously it seemed, but after one doctor did check it out, he did in fact hear a 'wispering' noise being produced from the ear.

One common malfuntion of a similar nature is Tinnitus. This is a disorder which can be either be physical (vascular anomalies, muscular contractions, etc.) or non-physical (abnormal physiological activity in the inner ear or central nervous system (CNS). While this is basically a symptom of a number of (or collection of) disorders, rather than a disease, and affects a fair number of people at one time or another. That ringing sound in your ear (and not after extreme noise, such as at a concert) is Tinnitus. For about 6.2% of adults in the US, for example, it can even be dibilitating.

Of course, as people ①age their hearing becomes ever more impared. That is because unlike the cilia of the olfactory system, those of the auditory system (within the cochlea) are not mitotically replaced. They lose their strength and even die out. This is also purely a mechanical function.

There are also CNS lesions, skeletal malformations ②, cranal nerve VIII tumors, Usher's Syndrome, Waardenburg's Syndrome, etc. which affect hearing and even cause hearing loss.​

① In some animals, those cilia may be replaced.
② In one example, where the middle ear bones grow over the oval window, fenestration, a surgical procedure where a hole is drilled through the bone material which has grown over the oval window, thus allowing transduction--hearing ability.

 

[Mars Man]

At some point in time, to provide an example here, an infant or child hears a clarinet. That sound is registered in short term memory (to be touched on later) and, after further exposure (within a single event, or over numerous events) and associated with (if such information is there) visual memory as well as other somasensory input for that event. 窶｡@ While the waveform is one repeating shape, the timbre is made up of a number of sine waves (overtones) and what effectively works out to be the fundamental frequency. 窶｡A

All of these will be picked up by different locations along the 'sheet' of the basilar membrane, producing an anatomically coded pattern of activity in the cochlear nerve. But we must also keep in mind that the wave of the attack of that note, and that of the decay will be yet different from the substained note--regardless of how short, actually, that hold may be. The attack wave will most evidently be some few milliseconds in length, and the other wave sections too, but they are all registered in the cortex and processed. And this can even be done while listening to the whold orchestra playing.

What happens if somewhere along the way, damage occurs to the cortical regions that have been built up to process the cognition of that sound? At first, one which comes to mind is auditory agnosias-like effect--where the sound when heard, will be 'familiar' yet cannot be identified. Lesions to the right hemisphere will more likely produce such effects where as lesions to the left hemisphere, obviously, will more likely effect linguistical matters.





窶｡@ This scenario is assuming that the clarinet is being played in the presence of the child, and visual inspection is thus assured; rather than listening to a clarinet via tape or CD, or from an unseen location.

窶｡A The sound of the average clarinet note will have up to some 20 waves, including the funamental frequency.

 

[Mars Man]

While in line with the immediate auditory system theme, this is also developing a section which will connect with a major point in the conclusion of this thread.

Comprehension of speech most obviously begins, in almost all cases, with the auditory system--working in the same process as learning that clarinet sound. The essential auditory system, however, delivers the processed sounds, and it is another connecting and co-operating system that recognizes the sounds, and yet other helpers that build the whole linguistical set up.

One of the major players is the Wernicke's area on the left temporal lobe in the auditory association cortex area. When there is damage to this area, sounds of speech can not be cognized properly, and in many cases, patients with Wernicke's aphasia show no signs at all of realizing their language errors. They will follow emotional facial cues, resting from speaking cues (from others), and do not look puzzled when listening...even though they are not understanding what is being said.

When asked to name several objects, for example, one patient gave the following:

stoktery for toothbrush, tankt for pen, nike for knife, and so on.​

On further occasions of being asked to name the same objects, new sounds came out each time, showing that it was not a matter of simply having 'renamed' the objects. In one case (and there could be others too) one object was correctly named each time, but only one.

Another aspect (or deficit) of this aphasia, among others, is pure word deafness syndrome. ① In the words of one patient with this deficit, "I can hear you talking. I just can't understand what you are saying." ② Another described it as having some sort of bypass somewhere causing the ears to not be connected to the mouth.

To make a long explanation short here, damage to the auditory input to the Wernicke's area or damage to that area itself, is disturbing the analysis of sounds of words, making speech understanding almost impossible. The patients can speak coherently on their own, and can understand written language, and identify emotion involved in the sounds but seem to not have the sequencing ability to distinguish the fine timing of sounds of speech.

I don't have any reports or information on any medical techniques, and their efficacy in overcoming this debilitating brain state. The Wernicke's area is quite specified, and plasticity may be hard to come by here--in the sense of remapping.



① It has been pointed out that the word 'pure' here should not be taken to mean 100%, because test results over a large sample space do tend to show some range of recognition.

② Physiology of Behavior by N. Carlson, 7th ed. (2001) p. 503

 

[Tsuyoiko]

A comment not directly following from the previous post, but related to the interaction of thought, speech and hearing.

I was reading yesterday about schizophrenia, in particular about different theories as to the origin, meaning and treatment of the 'voice-hearing' that is very often a symptom of the disease.

I think that cognitive psychologists have the most plausible explanation of the origin of voices. In a healthy person, slight movements of the vocal chords can be detected during silent thinking. This is known as sub-vocalisation, and shows that thinking is a kind of inner voice. Cognitive psychologists understand voice-hearing as a failure in this system. The inner voice is misinterpreted as coming from outside.

This failure to recognise self-talk has been shown experimentally, by recording individuals speaking, and then playing their voices back to them. Schizophenric patients find it much more difficult to recognise their own voice, and are much more likely to attribute their speech to another person.

Treatment of voice-hearing used to be limited to an attempt to eradicate the voices by various means, usually medication. It is now favoured by many patients and their psychiatrists to find a way to cope with the voices rather than eradicate them. Distraction can be helpful - many patients try to override the voices by listening to music or reading aloud. Some individuals prefer to listen to their voices and engage with them - which is basically what we all do when we heed our 'inner voice'.

At any rate, this organic approach is a far cry from the hearing of voices being attributed to possession by spirits. One more mental phenomenon has been reduced to a physical phenomenon and there's plenty more to come ;-)

 

[Mars Man]

Interesting information there Tsuyoiko chan; thanks ! I will go into some detail a little later down the line on schizophrenia, as well as Tourett's Syndrome, Sydenham's Chorea, Korsakoff's Syndrome, Parkinson's Disease, Huntington's Disease, Alzheimer's Disease, Autism, Bipolar Disorder, and a few others, so there is connection.

Also, regarding 'self-talk' (or the cognition of voices seemingly coming through the auditory system when they actually are not), we can find examples even in REM sleep stages, and in some bipolar patients, as well as in induced hallucinations (for example LSD). The conclusions these draw out also have bearing on the whole, big picture.

For now, however, I'll lightly go over the Vestibular System and the Somatosenses, with a short dip into cellular make-up and arrangement and activity (perhaps at several points within the above line-up), and after that I plan to go into making applications and debate mode.

Any interesting finds and comments always, of course, appreciated along the way. . . cause it will be a bit to come yet before that final movement.

 

[Tsuyoiko]

I will go into some detail a little later down the line on schizophrenia, as well as Tourett's Syndrome, Sydenham's Chorea, Korsakoff's Syndrome, Parkinson's Disease, Huntington's Disease, Alzheimer's Disease, Autism, Bipolar Disorder, and a few others, so there is connection.

I look forward to that - studying such conditions has led to many advances in the understanding of brain anatomy and chemistry. Perhaps I can recruit my Dad to give us some first-hand information on Parkinson's Disease

 

[Mars Man]

The vestibular system, as most of you all will know, is that of the detection of acceleration and head movement, as well as static position and oculomotor backup. (the oculomotor system is that for eye muscle control)

In the inner ear there are five structures--the three simicircular canals (anterior, lateral, and posterior) and the two vestibular sacs (the utricle and the saccule--also called utriculus and sacculus). This whole set-up sits adjacent to the cochela structure with the simicircular canals, which make large extended loops, approximating the three major plans of the head: sagittal, transverse, and horizontal.

The places where the canals touch onto the vestibular sacs have what are called ampullae, which are where the hair cells are. The stereocilia are enclosed in a gelatinous mass called the cupula which kind of block the ampulla and the canal. When the head moves, the endolymph (a liquid resembling intracellular fluid which has high potssium, and low sodium concentration) moves and in turn moves the cupula which then causes the stereocilia to open ion channels, causing a potential.

These cilia are responding to angular acceleration. The utricle and the saccule are a little different in build and function.

 

[Mars Man]

While the simicircular canals (SCC) especially signal angular acceleration, the utricle and saccule especially signal linear acceleration. Like the SCC, the vestibular sacs (sometimes called the otolith organs) contain cilia which are moved, thus giving potentials in the hair cells. Here, however, the hair cells are covered by fine crystals of calcium carbonate enmeshed in a fiberous web.

This system of calcium carbonate crystals (usually termed the otolithic membrane) lags behind when the head moves, and thus bend the hair bundles, causing stimulation and potentials. The otolith organs also are largely responsible for static information as well.

All of these are innervated by bipolar cells which bundle and project along in the vestibular division of cranial nerve VIII, bilaterally, to the brain stem's vestibular nuclei. Making short of the connections, one small ascending (there is also a descending line to all ipsilateral spinal levels) projects from the vestibular nuclei to the thalamocortical areas. This line is important for conscious awareness of head motion.

Again, while all the synapse connections and nerve lines are important and major lesions can breakdown the system, there are a number of things that can go wrong at the source, as well. One of them is a range of events which may fall under the description bening parozysmal positional vertigo. It can be caused due to age, or to a strong blow to the head.

In this case, some amount of calcium carbonate in one of the vestibular sacs may be disloged, and fall down against the SCC. In that position it may strike the cupula, resulting in signals that amount to a violent burst of dizziness and nausea whenever the head is moved. This condition is often easily cured by a fixed, systematic series of head movements call the Epley and Semont Maneuvers which effectively roll the dislodged crystal portion to a location where it doesn't interfere with cilia signaling.①

Some damages to this area can be very disabling, however; I'll give one example next.




① Sensory Transduction by Godan L. Fain, 2003, pp 142-146; Journal of Neurology, Neurosurgery, Psychiatry Vol 72 (2002) pp 366-372.

 

[Mars Man]

It is true that most causes of vertigo are known, and that the causes can be determined in almost all cases, yet it is more often than not, hard to diagnose. At times, symptoms of balance system dysfunction can be percieved as those stemming from anything between hypotension to epilepsy; there are a number of etiologies. It is also said that the symptoms are a bit hard to describe.

I was standing in my bedroom, brushing my hair in front of the mirror, and suddenly it was as if I had two heads--me looking in the mirror and knowing that I was, but the innerhead spinning round and everything going with it.

Everything I see bounces like a bad amateur video. . . it's as though everything I look at seems made of Jell-O, and with each step I take, everything wiggles.​

One case of a patient who lost vestibular function almost totally (due to the antibiotic gentamicin, adminstered after a post surgical infection developed) shows how bad it can be. The woman could not stand on her own, and when even using the walls or tables and such to brace herself, would jerk--as though little demons were poking her here and there with pitchforks. In darkness (like when turning out the lights at night) she would fall, if standing.

She lost a fairly good job, could no longer drive nor get around by herself, among so many other hardships--and on top of all that, the worse, perhaps, simply feeling as though she were falling...all the time!

Spending a lot of money, and with some good connections that patient was able to overcome that by focusing the neural circutry on the remaining functioning nerves of the vestibular system, and thus recovered very well. She may have trouble again, however, as she ages.

Something in the system breaks down--a lesion, tumor, or head damage, etc.--and the signaling to the cortex from the vestibular system (and often ocular [visual] system along with it) creates a very distorted reality in the concious mind. In the internal sphere (that is, in the brain alone) it is very real and the brain itself is acting on it, but in the external sphere (that is reality which is objectively outside of the brain) it is not real at all; beyond a third person's viewing the body of the patient reacting to the internal reality. ①



① The afflicted person is not actually falling through open space, is not physically spinning around--nor is the physical world around that person spinning around while that person is stationary in position.

 

[Mars Man]

One last area that I'd like to somewhat lightly touch on, since with the above expositions a fair enough understanding can be gleaned about the neuroanatonomical/physiological aspects of the sensory input systems and maps (although maps will come up again), is the somatosenses area.

The lumbar connected to the cauda, the cauda connected to the sacral, sacral connected to the lumbar, the lumbar connected to the thoracic, thoracic connected to the cervical, the cirvical connected to the hind brain. . . well, I guess it doesn't make as good a song as the old one is, but just thought I'd try...hee, hee, hee. That's the nerve flow from the tail up. (the hind brain is the brain stem (medulla, pons, and cerebellum)

The two major divisions of the nervous system are the peripheal nervous system (PNS) and the central nervous system (CNS). I'll next go into a little about primarily the CNS and the relay to the somatosensory cortex areas.

 

[Mars Man]

The peripheal system (PNS) consists basically of the nerves that are used in 'communicating' with the CNS. It again is divided into the somatic nervous system, and the autonomic nervous system. The autonomic nervous system is again divided into the sympthetic (thoracic & lumbar) system and the parasympthetic (cranial & sacral) system.窶｡@ These will come up later too.

The central nervous system (CNS) consists of seven basic divisions:

cerebral hemisphere
diencephalon
midbrain
pons
cerebellum
medulla
spinal chord​

The diencephalon consists of primarily the thalamus and hypothalamus. 窶｡A The midbrain (also called mesencephalon) consists of basically the tectum and the tegmentum. The pons (bridge) has various connection, or relay areas and also seems to be important in basic sleep and arousal states. The cerebellum (little brain) has a lot to do with motor coordination. The medulla (also called myelencephalon, also medulla oblongata) deals a lot with vital functions.

The next area of concern here, is the mapping of the body in the CNS outlay of the somatosensory cortex area.




窶｡@ There is also the entiric subdivision, but it only deals with the large intestine.

窶｡A There is also the telencephalon, which is also part of the forebrain, of which the diencephalon is a part of too, which is not mentioned in this CNS division. This is the symmetrical cerebral hemispheres (cortex), and contains the likes of the limbic system and the basal ganglia.

 

[Mars Man]

We all pretty much know the shape and appearance of the brain--the bulging and convulution, grooves and cracks, the 'walnut look,' and all. The large groove that clearly divides the right and left hemispheres is the sagittal fissure① (and it might be good to keep in mind that sagittal will always mean a plane 'cuts' through the brain from front to back). The smaller and not as deep cracks that can be seen running top to bottom of either side of the cortex, are usually called sulci (plural, which means grooves; singular is sulcus).

On the lateral side ② one will notice one major sulcus running from to bottom. This is called the central sulcus. The parallel bulging areas (convulations; called gyri (singular. gyrus)) that run along side it are the precentral gyrus (rostral) and the postcentral gyrus (caudal). The cortical area rostral to the central sulcus is part of the frontal lobe and the area caudal to it is part of the parietal lobe. The precentral gyrus is the primary motor cortex and the area just rostral to that is the premotor cortex--which consists of the cingulate motor areas③ in the ventral inside overflap of the cortex (going down into the saguttal fissure), the supplimentary motor areas in the dorsal lateral position with the primary motor cortex then extending downward from the middle frontal gyrus (which runs basically front to back up to the primary motor cortex. The area rostral to that is the motor association cortex.

The postcentral gyrus is the primary somatosensory cortex and the area just caudal to that is the somatosensory association cortex. The ventral cortex area just caudal to the upper portion of the inside overflap, and the cingulate sulcus, is the cingulate gyrus. Immediately caudal to that is the corpus callosum which is the main commissure connecting the two hemispheres.

I will then go into a little more detail of the motor and somatosensory tracts, pathways, and projections, and after that recap a little before proceeding with examples of the brain at work--'minding.'





① A fissure is usually more consistent in shape and depth than a sulcus, but sometimes both names will be found for some.

② I'll point out again, for convenience, that the upper and back direction of the brain [to a point--from where it becomes caudal] is dorsal (or superior sometimes for upper, in contrast to back), the lower direction ventral (or inferior), the forward direction is rosteral (or anterior). One difficulty is keeping in mind that unlike, say the rat, the human neuroaxes bends, therefore in relation the spinal chord which runs vertically, ventral is in front (stomach, chest), dorsal in back, and caudial or posterior in the down direction. Lateral is to the side (left and right) of a structure, and medial is to the inside of a structure. Sometimes terms will overlap a little.

③ I use plural here because it is the same on both hemipsheres.

 

[Mars Man]

From just over the tip-top of the cortex, in the area we have been looking at, down into the medial area, we will find the beginning of our homunculus --that little somatotopical organization of a weird little super-sized hands and large mouthed duplicate of ourselves. The basic mapping is fairly the same for both sensory and motor cortex, but there is some difference, and there are other maps as well.

For the sensory perceptive function, the somatosensory cortex (used here for the over all system of primary, secondary, and insular cortex) is the basic final terminal (so to speak) recieving all but olfactory sensory information through the thalamus. From the caudal medial cortex our sensory map starts out with the genitals, and goes to toes, then feet. From there, legs, then coming on over the top gyrus, hip, trunk, neck, head, shoulder, arm, elbow, forearm, wrist, hand, little (finger), ring, middle, index, and thumb. About here, we go into the secondary representations--eye, nose, face, upper lip, lower lip, teeth, gums, jaw, tongue, pharynx, and intra-abdominal (which go on into the insular cortex maps).

Sense this will be referred to again when talking about phantoms, I'll lay out an easier to follow, general format starting from the cingular map: sex organ, lower limbs, neck/hear, upper limbs, hands/fingers , face area, then others.

The information that is coming in is in the following forms, and will come up later too (thus it would be good to keep this in mind):

TOUCH (tactile).................receptor type

texture/superficial..........................mechanoreceptors
pressure/deep
vibration...................................................pacinian
​

POSITION SENSE

static...........................................mechanoreceptors
dynamic (kinesthesia)
​

TEMPORATURE SENSE

cold.............................................thermoreceptors
warmth​

PAIN

fast (pr'cking)................................nociceptors
slow (burning)​

ITCH...............................................histamine​

While the motor cortex mapping is primarily the same, the motor connections are a bit more complicated. I will lay out a fairly simple schematic of those in the next post, because that background information will be needed in the discussion that will later follow.

(ps apologies for the lack of being able to edit more correctly...I can't seem to put those letters together)

 

[Mars Man]

Alrighty. . . and from here I will go; but I'll now leave the neuroanatomy for only when it really becomes necessary. (although the terms will come up much of the time...I mean, there is simply no way to describe the routing of reading in consciousness, inner speech, and, semantic and episodic memory, while taking meaning from what visual input is being processed in the various areas, without mentioning them)

As promised above, I will go over some of the neurological disasters which disturb the self. I will continue with the hard data which overwhelmingly ascribes to brain, the entirety of individual concept--thus clinching the understanding that it is we, individually, which are the result of the synaptic connectivity of that individual organ, the brain.

 

[Mars Man]

In summary of the posts above, we have the following conclusions (of course taking in much more data and test results than what are given in this thread):

1. Sight is a physiological event which depends on input from the retinas through the lateral geniculate nuclei (LGN) through especially two different pathways towards the occipital lobe where it is processed from V1 through to V5 and the Medial temporal area. If there is top-down executive activity, or signal strength is strong enough, attention will make the brain processes conscious--then we are aware of, and can report on, seeing something in the visual field. First person (1P) report, and second and/or third person observation (2P/3P) will indicate that actual and clear vision is happening. While there are further details, the conclusion is that certain cortical brain area is a requirement for visual knowledge.

2. Smell is a physiological event which depends on molecular attachment in certain way to a proper receptor. Further, processing by the brain area which deals with the odors, and emotional attachment by areas in the limbic system cause a level of 'neuron talk.' If there is top-down 'spotlighting,' or the signal strength is strong enough, attention will make the brain processes conscious--then we know that there is an odor. This is an event which does not happen on a 1P without the proper neural processing areas, and their connectivity (feed forward, feed back, and reentry).

3. Hearing is a physiological event which depends on (especially) air movement and vibration picked up by the inner ear. Two pathways deal with signals in main, but there are surely further association tracts projecting to other locations. Again, 1P experience of hearing--meaning being aware of, and able to report on, having heard an external sound--requires certain cortical areas to be fully functioning. Without these, there can be no consciousness of externally sourced sound--although vibrations can still be sensed.
​

All these sensory experiences require not only a certain degree and build of brain (connectivity, integration, and reentry processes), but also also require consciousness to be able to be reported on. This is true in that brain is mostly active at a level which is below the threshold of consciousness, and yet it can process and do what it does--which I have temporarily termed 'conscious.' The brain which of the sleepwalker who will drive his car for a rather long distance while asleep, is of course seeing, hearing, and smelling, but none of that gets consciousness attending to it. The brain of the nude lady who climbed the tree and had to be rescued by the fire department (she seemingly got up there, but couldn't get down [like some small cats might do...hee, hee, hee]) was sensing, planning, and executing to a less, yet certain degree--but she was totally asleep; unconscious.

As we go into volitional movement and the sensory area of touch and tactile senses, we find that brain is the only thing there is doing it. As for the illusion of authorship in movement (and this is not to deny that we are the authors of our movement, but simply to more carefully distinguish the processing levels and timings) we know that 'conscious' (this is being used as a non-count noun, in the sense of the aggregate of neural activity; and is being applied as a 'place holder') does it before consciousness 'knows.' Actions are starting before consciousness of the engagement of the particular executed act is there.

After a touch on that, I'll go over some of the devastating effects of neurological breakdown--such as Parkinson's disease, and Huntington's disease. (though it may be a few days later)

 

[Mars Man]

In the area of movement, it is clear enough that there are several areas interacting in the absence of conscious awareness of such. The 'urge' to move, say to scratch a mesquito bite, happens with an increase of neural activation (a phase field, of sorts) from posterior ares of the parietal lobe to the SMA--not in a one way fashion, but with feed forward/feed back, and reentry.

In open brain surgery, stimulus can be applied in a certain degree which the patient will verbally report a sensation to move a certain body area. In a different area, the same amplitude will actually cause a movement of, say, the arm and wrist, but the patient will report in the negative when asked if he/she had moved that member (visual input is blocked out at that time). The general effect is very related to the Libbet (I think that spelling is correct, but will check it later...I have a cat in my lap, and we know how important it is not to suddenly stand up).

Then, as far as being in control of movement, among a number of other factors, there is the basal ganglion, and the DA system. Especially the DA system comes into play in Parkinson's disease. That and more coming up.

 

[Hamun]

I also think human being is not so difficult to be recreated with the today technologies.
We already have video cameras for eyes,
diktophones for ears,
for touch we can find some sensors,
about smell and taste,technology has not advanced in recreating,as far as I know,
we have memoy to store all the data,
and programs like "Photoshop" to deal with picture data,there should be something about the audio,
so don't we have almost a brain(computer),
no need to make billions of neurons.
Even I am no completely right,think big companies and universities should try to
find more about this,because it could be immortality.
I tried writing here and there,but almost no response,if you have any ideas how to tell
about this or have any connections,let's try to make it more popular.

 

[Mars Man]

Nice to hear of your interest in this area, Hamun san. I do hope you continue to look in every once in a while.

I also think human being is not so difficult to be recreated with the today technologies.

Actually, Hamun, it's not quite that easy. There are a number of thinkers in the neurosciences who have offered posititve statements when asked if they thought the the human brain could be done with AI. As for those who I have read, there is always the additional comment that it'll have to wait for some newer technology to be developed, however. Even with projects like the The Blue Brain Project (which is working from cellular minicolumns to produce celebral cluster-like silicon-based systems) we cannot say that 'we almost have a brain.'

The work in the AI industry is on-going. Some good work is coming out with neural networks applied with/interactive with biological cell cultures too. Even so, it is very far from having any whole and interconnected-with-reentry capability brain. Now the earthworm, with 305 neurons would be a much easier thing to do...and the robotic systems we have produced out do that already.

This thread is dealing most specifically with the human brain (more than anything else), so I'd hope to keep AI discussion on the side; for now. Some of the topics which Pachipro has raised on his third paragraph of this post can be touched on in due time--I reason--because that is in the nature of the theme of the brain as being the person. Please do check back from time to time !! Thanks !