Asked 18th Nov, 2014
Is the thalamus REALY the CPU of the Brain?
In a recent article, Yingxu Wang asserted that in a previous article he had determined that the thalamus was the CPU of the brain. I have heard in other articles and books that no CPU can be found for the brain, and have personally adopted the assumption that instead we should be looking for a distributed processing system, with outputs at certain locations such as the prefrontal lobes and the inferior parietal lobule. But I am certainly not an expert, what does the experts have to say?
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I agree with Renzo. Sensory information (except the sense of smell) relay through the thalamus, but it's not clear that the thalamus adds or modifies any information; this is in contrast to a CPU in a computer, which performs calculations on incoming information. I think you are correct to look for a distributed processing system, because processing happens in multiple areas of the brain and we are still looking for what combines that processing to make a whole consciousness or sensory experience (which may not be in one lone place).
Yeah Renzo, my understanding is that the thalamus is a linking area with the ability to block the links. As someone with a computer background, this does not sound at all like a CPU. It sounds more like a BUS.
Thank you John and Ralph I agree completely, Dr. Wang has made a mistake by trying to stretch the computer metaphor too far, in calling the thalamus a CPU. I think it points out how dangerous it is to use self-citations to back up a theory.
I second Ralf's remark in that although metaphores can sometimes promote initial insight, real understanding of a complex subject such as neurophysiology demands studying the subject in it self rather than continuing to think in analogies about the matter.
Of course not. This is a dangerous simplification. This kind of simplification is unfortunately increasingly present in Neurosciences. Stay awake.
There are indeed some parallels between symbolic
information processing and a computer. The basic
datatype in the brain is the symbol. Data structures
are tuples of symbols. Tuples comprised of up
to about 7+-2 symbols. One tuple fits in
working memory (can be compared with the
registers of a CPU, accumulator and the like).
Working memory can also be compared to a
shift register: there is one input for
one symbol, and upon storing older symbols
fall out (get forgotten).
The content of working memory is occasionally
written as a whole into long term memory
with a low transfer rate. The long term
memory of a brain can be compared to a PROM
or a CD.
Obviously seventuples of symbols is also the
basic data structure of long term memory.
This because upon retrieval more than
seven symbols would not fit into working memory.
Bigger data structures in the brain are built
via association: two tuples are joined by
having at least one symbol in common.
A metaphor more fitting than a CPU is
a Turing machine. Turing machines calculate
by taking the pair input character and
old state as key in a table to retrieve
a character to write on the tape, a new
state, and a tape movement.
The brain takes the working memory as
input key for associative retrieval
of an action. Associative can mean
LTM memory recall or doing pattern
matching (parsing) of the input.
An action can mean anything the brain
is capable of.
I'm uncertain how this conclusion can possibly be reached - namely that he "determined that the thalamus was the CPU of the brain". We are all still at the stage of uncovering what brain structures do as an interconnected whole and have not yet even made the kind of measurements that are needed to reach such a conclusion. Analogies with computer science may be very useful in understanding how the brain does what it does, but calling the thalamus the CPU is incredibly premature and quite a stretch.
National Vice President Bhartiya Agro Economic Research Center New Delhi EX Head ICAR-Indian Institute of Soil and Water Conservation (Earlier known as CSWCRTI)
Dear Graeme Smith, I think so. Thanks I mean it Thalamus works as CPU of brain. Dear, Am I wrong Dr Graeme Smith?
In most simple terms the Thalamus can be related to switch or filtering/dampening/amplifying relay point. While a lot of computing must clearly take place in thalamus a better analogy for CPU would be the cortex, Here for example patterns in vision are detected such as edges, contrasting areas, slopes and so on. Another part of cortex analyzes the sound coming to our ears in various frequency bands, so some kind of frequency analysis has to be computed...
Rather then looking for a focal computation point within the brain one might compare the brain to an interconnected farm of computers specialized in various functions (sound analysis, vision with sub processing of contrast, slopes, color, movement etc)
Thankyou Konrad, I agree, the cortex is more processor than the thalamus, and it acts like a network rather than a CPU.
I know, People are keen to find parallels between Computers and the brain. I as a Neurologist and neuroscientist would have been on the careful side. The only thing I am acknowledging is BCI Brain Coputer Interface, because there is some success and advance in this field. Also the Bereitschaftspotential discovered by HH Kornhuber and L. Deecke in 1964 is important in this field, letting patients with handicapped limbs try to move them 'by thinking' so to say. But isn't it a Little naive to say the Thalamus is the CPU (the central processing unit) of the brain? Maybe, a Computer needs an CPU and also a bus to connect it with the disk. Do you think the brain needs a CPU? If is does, it has to be found somewhere in the cerebral Cortex, but the Thalamus is not a good candidate. The Thalamus has many nuclei, and they are relay nuclei fromthe senses to the Cortex. I worked myself in the Thalamus finding the vestibular relay nucleus (the VPI) the ventro-posterior-inferior relay nucleus. The Thalamus has relay nuclei for all the Enses except perhaps taste (gustation) and perhaps olfaction going directly drom the olfactory bulb to Cortex. It is also important to realize what happens if the Thalamus is destroyed in diseases. Then you get the Thalamus-syndromes, one of which is a Kind of very torturing burning pain. The Thalamus is also important for the wake-sleep cycle. For instance we had patients with a prion disease in our clinic where the Orions destroy thalamic tissue leading to a fatal 'familial' insomnia, in the end the Patient looses entirely the ability to sleep, and the outcome is fatal. I could continue bringing more Details, but the Thalamus has so many functions it is not just a CPU but much much more. So this 'interpretation' is much too superficial. I realise that my 'previous speaker' is of the same opinion, so the Thalamus has magnitudes of complexity more that a central processing unit in a Computer. Cannot be compared. Are completely different world. To see a parallel in them is more than superficial to the extent that there is no parallel or analog, different worlds. Best wishes fom Vienna Yours L. Deecke
Thankyou Mehran and Luder. I had not heard that the thalamus was more complicated than a CPU. Perhaps a bridge is a better metaphor than a bus. I don't think the brain needs a CPU like you say Luder, it has a need for central control, but not for central processing because every neuron can do some processing. Besides the thalamus comes late in the process, for the CPU.
Early brains didn't have the thalamus but they still had central control.
Thank you for your reply, Graeme. Earlier brains didn't have the thalamus . . . Very much earlier brains! The vertebrate brain has the Thalamus. Yes, central control is important but it is not the thalamus that exerts central control. It is true that the thalamic nuclei have the relay function to channel sensory Information up to the cortex. And only what has made its way to the cortex has the chance to become conscious. Conscious perception.This bright, alert, and awake awareness of what is going on . . . So the highest level of central control is our consciousness. On this platform we are also busy in decision making, for instance whether the sensory Input that has climbed up into consciousness needs or deserves a reaction. This is the situation of 'the responsive brain'. You might know that Kornhuber and myself with our Bereitschaftspotential have found brain activity that occurs prior to an action, i.e. it occurs with the readiness for action. The action is prepared already preconsciously but consciousness is switched on about 200 msec prior to the action. We know this from Libet. My mentor Hans Helmut Kornhuber (1928-2009) and I are of the opinion that we do, indeed, have free will, although the Bereitschaftspotential starts earlier than the feeling, the urge, the wish 'now I am going to make a movement or action' (Libet). Kornhuber and I believe that freedom is in us - Daniel Dennett thinks the same: Freedom evolves. Although we are not completely free, because this would mean to be free from nature and this is impossible - nobody can escape nature - we have relative freedom, freedom in degrees,and we can do something for our freedom. So we have free will but we should not exploit it! Our credo is 'reasoned free will'. Excuse, please, Graeme, I pulled the discussion far away from the initial CPU-thalamus argumentation, but the red thread was central control. This is on the highest level in the neocortex and our subjective sensation of that level is consciousness. We are equipped with what we call reasoned free will. If I may end with recommending further reading: A book: Kornhuber HH, Deecke L (2012) The Will and ist Brain. An Appraisal of Reasoned Free Will. University Press of America Lanham, Boulder, New York, Toronto, Plymouth UK. ISBN 978-0-7618-5862-1. Best wishes! Yours Lüder Deecke. P.S. I hope you do not stone me for going ahead on my own . . .
No stones here Luder, but I would caution you that it depends on your definition of consciousness how involved the cortex is. Domassio's work links consciousness to the roof of the midbrain, and my own work suggests that in fact there isn't just one state of consciousness, it accretes in many stages to the core consciousness in the Optic Tectum. Only some of which are linked to cortex development. By the time we get to humans, we have cortical stages of consciousness, I agree, but earlier brains were active, and awake without much cortical involvement.
As for freedom, I do not doubt we have it, my own personal question is about the nature of Will. I maintain that the assumption of a causal force, is caused by an illusion created to simplify control.
But we digress, and it is not fair to the other monitors of this thread to spread the focus away from Dr. Wang's assumptions of the thalamus as CPU. Perhaps we could discuss this in another forum.
Yes, Graeme, it would be fine to discuss this in another forum., tectal vision is not conscious, all attempts to work with it in rehabilitation failed so far. - One final thing though, very short: I am not a believer in a subcortical site of consciousness, Damasio. If one says consciousness needs the whole awake brain, this comes close but is not quite true. We know from epileptic patients that a focal seizure is still compatible with consciousness. The seizure activity can even occupy the whole sensorimotor cortex of one hemisphere, we call this a 'hemi grand mal', and the patient is still conscious. However, as soon as the seizure generalizes which means as you know the seizure activity travels across the corpus callosum to the other hemisphere - then the patient loses consciousness. (It is also interesting that according to Sperry and Gazzaniga that the split brain patient does not feel 'split' but he feels himself a unity). So what we learn from epileptology is that consciousness needs at least one hemisphere. Best Yours Lüder.
I have opened a new discussion for us if you are interrested in dealing with the question of free will. We can open another discussion about the placement of the consciousness if you wish.
This is wonderful. I think consciousness and the freedom of will can go together. The start was what I wrote before. If I remember correctly there was already a discussion of free will previously in Research gate. Most of the discussants were in favour of a concept of free will. best Yours Lüder
Corticofugal axons from the barrel field leave the cortex and traverse the striatum in small bundles, which split off in two main streams as they approach the thalamus. A dorsal stream consists of the axons of layer 6 cells, which head directly toward the dorsal thalamus and distribute arrays of small terminations in RT and the ventral posterior medial (VPM) and Po nuclei. A ventral stream comprises the axons of layer 5 cells, which continue their course downward through the pallidum and join the internal capsule. At the exit from the pallidum, some fibers give off branches that enter the thalamus through the ventral part of RT. Most collaterals ascend through the superior thalamic radiation, then head rostrally toward Po. Only two fibers forming club-like endings were seen to enter the thalamus dorsally with the contingent of layer 6 axons and, interestingly, these two fibers did not stem from any of the axons projecting below thalamic level
The barrel field is in rodent brains isn't it Krishnan?
could you explain what this interesting information has to do with the assertion that the thalamus is the CPU of the brain? It's not immediately obvious to me whether you are thinking it is, or isn't.
Yes Luder, there have been at least two discussions of free will, I had hoped that my formulation of the question was enough different not to overlap. There have also been many discussions on consciousness some of which are still ongoing.
Dear Graeme, yes I forgot your texting. I think it is good, and as you wrote "enough different". You suggested: 'Is will free or does freedom exist without the presence of a force of will?' O.K. lets discuss on this basis, this will be fun! Do you do the necessary steps? I like it, it is kind of sneeking out from the original discussion but this emanation may be fruitful and may fall on fertile grounds Best wishes Lüder
To Krishnan: Thank you for this precise hodology, but I am joining Graeme in the question: 'what has it to do with the CPU discussion? Best Yours Lüder
A more provokative question to Krishnan is: What have the whiskers of rodents to do with the CPU discussion? This is mean,isn't it? Yours Lüder
Luder, the forum is already started and has a few entries in it, from other interested parties, Let me try to put a link to it. for you again.
Luder here is the link for the new forum on placement of consciousness:
As in a CPU, During the study of spatio-temporal dynamics of cellular interactions in the somatosensory thalamocortical system underlying the natural medium-voltage oscillation gives rise to Spike and Wave discharge (SWD) -research on rats
- In GAERS, generalized spike-and-wave discharges were correlated with synchronous rhythmic firings in related thalamic relay and reticular neurones.
- Usually, corticothalamic discharges phase-led related relay and reticular firings.
- A depolarizing wave emerging from a barrage of EPSPs was the cause of both relay and reticular discharges.
- In some relay cells, which had a relatively high membrane input resistance, the depolarizing wave had the shape of a ramp, which could trigger a low-threshold Ca2+ spike.
- The epilepsy-related thalamic, relay and reticular, intracellular activities were similar to the normal-related thalamic activities. Overall, these findings strongly suggest that, during absence seizures, corticothalamic neurones
, which are always accompanied by whisker twitching.
This natural rhythm does not give rise to SWD in control NE rats, meaning that it is not itself sufficient for generating absence-related epileptic activity
Thank you both. First to Otto: It is clear that consciousness is not possible without a functioning reticular formation (the arousal System of the brain). The reticular Nucleus in the Thalamus is different from that. You cannot say that consciousness resides in the reticular thalamic nucleus. I stated already that the Cortex is necessary for consciousness. Without cortex there is no consciousness. I think from this that consciousness cannot reside in subcortical areas or nuclei.. Of course there circuits and Loops. Even the important Motor Loop (the cortico-basal ganglia-thalamo-cortical Loop) which is so essential for movement and action has a Station in the Thalamus. This is important to always realize. This also increases the complexity of the Thalamus enormously and for sure far beyond a CPU. Best Lüder
Thank you very much. Yes, the brain is a very big machine, and so far, the octopus brain is much less investigated - and that of the most highly developed mantis shrimps - to inductively understand the essence.
Those reticular nuclei I had been told about came from the opinion of an Australian anesthesiologist whose name I do not have who allegedly found that unconsciousness in anesthesia could be read-off reliably only there. But how he came to this result I do not know.
To date we know more due to the work of the recent nobelists about the flight simulator in the mammalian brain.
I hesitate to mention the brain equation in this context which I invented in 1973. It is part of a top-down deductive, Darwinian-analogous, approach. There was a fleeting attempt to take it up in Japan, I was told. A recent book by Bill Seaman of which I am the coauthor talks lightly about it (Neosentience - The Benevolence Engine). The connection between bottom-up and top-down has not yet been made.
Forgive me the many words I made, take care, Otto
It's a very interesting question, but the analogy between the brain and a computer is absurd. the brain is a distributed system and the "CPU" does not exist.
Dear Otto, Dear José! I cannot agree more with you, José. The Computer is a man-made product, the brain - and so far the human brain is top, also much more complex than the one of dolphins and whales - is the 'product' of evolution, which is the best optimizing system we can think of and this product made by nature was forged over millions of years. Thus, the 'Computer Approach' to the brain is not expedient or effective nor is it helpful . . . You know that the brain works with many many elements (synapses) 28 Milliards of Neurons alone in the cortex making connections with let's say 100 on the average with other Neurons - which still is a very low estimate - will make 2.8 Billion Connections (These are mathematical billions not american billions). So as I use to say: The human brain are the most complex 1.5 Kilograms in the universe. A number almost unimaginable. The Computer People would call this redundance, which is a negative formulation, but typical for the 'computer approach.' For nature this high number makes full sense. It implies security. Without this redundance, which should be called 'the good redundance', Neurology or especially Neurorehabilitation would have no Chance! What is probably not known so much to non neurologists is that the brain has self-repair. This is our biological basis of our freedom, which we share with animals and which so far computers do not have, this is the spontaneous self-repair of defects in the brain. In older age we all have little vascular infarctions in the brain which we are not aware of and which are compensated by repair programs. This is the spontaneous quick repair, there is more repair, long time repair that needs exercise and an active individual. The brain tries in every lesion to compensate for the handicap as much as it can, if a lesion is in one hemisphere, the other tries to help in the compensation. The brain's self-repair goes to the extent that blind people who lost their eye-sight early in life jointly use their visual cortex, in order to read the Braille script, which they feel for by touch (Uhl et al. 1993). If we were hard-wired like a computer, all this would not be possible. In nature, redundancy is a good thing! You mentioned a book, may I also mention one for further reading: Kornhuber HH, Deecke L. The Will and its Brain: An Appraisal of Reasoned Free Will. University Press of America, Lanham, Boulder, New York, Toronto, Plymouth UK (2012) ISBN: 978-0-7618 5862-1. Best wishes from Vienna Yours Lüder
Many regions of the brain are essential (to life, consciousness, vision etc) but there's no cpu, processing data/instructions stored in memory. Instead each neuron (with its synapses) computes a function of its synaptic input, with the synapses both storing information (generated by previous computations) and processing information. Much more efficient! Thus each neuron acts as a computer, and the cortex as ten billion yoked parallel computers (each melding cpu+memory). The one drawback of this scheme is that the neuron-computers are, inevitably, partly analog and subject to drift, noise, crosstalk etc. We have argued (syndar.org) that reducing intersynaptic crosstalk is the central problem the brain faces and that the cortex has achieved a uniquely powerful solution, comparable to the way that molecular proofreading underpins life.
Processing function does appear to be distributed throughout the brain but even more so the brain has the ability to dynamically modify its function in response to both healthy and disease related internal and external input or activation. In contrast to a CPU, the brain can often compensate for a lesion in one area by modifying the function of an other area or network of areas. Therapeutic interventions such as deep brain stimulation rely on such mechanisms to correct for tremor or other motor and psychosomatic disease symptoms.
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