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Thread: Neurons: humans v. pigs, ants and worms...

  1. Top | #11
    Sapere aude Politesse's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by Politesse View Post
    They are certainly larger and longer physically, and there are a number of ways in which their electrical processing is different. We've got these long branching dendrites that seem to allow for much more functional compartmentalization. We also have some weird inhibitory neurons called rose hip cells. Much of the research on this question is younger than a year, I think much more detailed answers will soon be possible.
    I don't mean functional differences between brains or even part thereof, but between neurons. What you say seems to mean that we don't know yet that there are actual functional differences... Am I wrong?
    EB
    You're quite wrong. Neurons are and were the topic of discussion.

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    Mazzie Daius fromderinside's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by rousseau View Post
    https://www.ncbi.nlm.nih.gov/pubmed/16805421

    The myelin sheath, and hence the myelin-forming cells (i.e. Schwann cells in the PNS and oligodendrocytes in the CNS), have been a crucial acquisition of vertebrates.
    I'd make a guess that vertebrates / invertebrates are where things really diverged, but could be wrong about that, and I assume that's a simplification.
    This seems to me to be an adaptation of neurons to the need for increased performances in relation to a a more complex system. Neurons may be essentially the same in vertebrates and invertebrates except for the need to extend communication between neurons over longer distances, and therefore to speed up signal transmission, etc. If that's true, then the functionalities of neurons remain the same. All the functional evolution would come from the evolution of the system rather than that of the neurons themselves.
    EB
    OK. Don't read what I wrote. It just makes you repeating queries that I've already answered look more lame.

    Skin on my nose is just fine. Yours seems to be a bit sullied.

    As to mammals having neurons that are mostly the same you'll find there are changes to cells associated with memory and sense that begin to appear in more recent mammals, those that self recognize and show empathy. They're the basis for long term memory, empathy, and recognition in ascending systems. There may be important changes in human neurons in Cerebellum and language association area that lead to complex language expression and memory.

    No more just connect and decide and-or simlistics.
    Last edited by fromderinside; 10-08-2019 at 05:34 AM.

  3. Top | #13
    Contributor DBT's Avatar
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    Bird brains are more efficient and tightly packed:

    ''Some can count, many make tools, and others recognise themselves in the mirror. But how birds pull off such complex feats with so little brain matter has long had scientists scratching their heads.

    Now an answer may finally be at hand. Researchers who studied 28 bird species found that songbirds and parrots can have as many, and sometimes more, neurons packed into their brains than mammals - even monkeys and apes.

    The tiny but densely-packed neurons are thought to endow birds with cognitive abilities that far outstrip expectations and which in some cases are more than a match for primates with similar-sized brains.

    “For a long time there has been this enigma that birds have rather small brains but are actually incredibly clever,” said Pavel Němec at Charles University in Prague. “They are able to do things that we once thought only apes and humans could do. There was a mismatch between their brain size and their cognitive abilities.”

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    Mazzie Daius fromderinside's Avatar
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    The following study provides one means by which neurons functionally diverge. There are many others if you just keyword Evolution of diversity of neuron function

    Regulatory logic of neuronal diversity: Terminal selectorgenes and selector motifs https://www.pnas.org/content/pnas/105/51/20067.full.pdf

    Abstract:Individual neuronal cell types are defined by the expression of unique batteries of terminal differentiation genes. The elucidation of thecis-regulatory architecture of several distinct, single neuron type-specific gene batteries in Caenorhabditis elegans has revealed astrikingly simple cis-regulatory logic, in which small cis-regulatory motifs are activated in postmitotic neurons by autoregulatingtranscription factors (TFs). Loss of the TFs results in the loss of the identity of the individual neuron type. I propose to term these TFs‘‘terminal selector genes’’ and their cognate cis-regulatory target sites ‘‘terminal selector motifs.’’ Terminal selector genes assignindividual neuronal identities by directly controlling the expression of downstream, terminal differentiation genes and act in specificregulatory network configurations. The simplicity of the cis-regulatory logic on which the terminal selector gene concept is based maycontribute to the evolvability of neuronal diversity.
    Evolvability: Gene regulation by terminal selectorgenes provides a framework to thinkabout the evolution of neuronal diversity.The simplicity of terminal selector motifsmay mean that individual genes can berapidly recruited into or lost from a neuron type-specific gene battery through lossor gain of terminal selector motifs. Suchplasticity may provide a rich playgroundfor evolution. The small size of terminalselector motifs and their consequentabundance in genomes suggests that manyterminal selector motifs are not active;whatever regulates this dormancy, such asthe above-mentioned possible nucleosome-mediated motif accessibility,provides another regulatory layer for evolution to play on. The addition of a functional selector motif into the controlregion of a TF may also add a specific‘‘subroutine’’ to an existing neuronal class specific gene expression program. Another way to view terminal selector genesin an evolutionary context is that the recruitment of terminal selector genes into anovel cellular context, e.g., by the acquisition of a novel cis-regulatory input intothe terminal selector gene locus may generate a dramatically, rather than incrementally distinct, novel neuronal cell type,defined by the set of genes originally expressed in the cell type plus an entirelynovel gene battery; such a ‘‘hybrid’’ cell isthen subjected to Darwinian selection.Taken together, simplicity in regulatoryarchitecture may provide evolutionaryplasticity.

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    Contributor Speakpigeon's Avatar
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    Quote Originally Posted by DBT View Post
    Bird brains are more efficient and tightly packed:

    ''Some can count, many make tools, and others recognise themselves in the mirror. But how birds pull off such complex feats with so little brain matter has long had scientists scratching their heads.

    Now an answer may finally be at hand. Researchers who studied 28 bird species found that songbirds and parrots can have as many, and sometimes more, neurons packed into their brains than mammals - even monkeys and apes.

    The tiny but densely-packed neurons are thought to endow birds with cognitive abilities that far outstrip expectations and which in some cases are more than a match for primates with similar-sized brains.

    “For a long time there has been this enigma that birds have rather small brains but are actually incredibly clever,” said Pavel Němec at Charles University in Prague. “They are able to do things that we once thought only apes and humans could do. There was a mismatch between their brain size and their cognitive abilities.”
    Yes, I think this is relevant. It shows scientists know much less than some people here pretend that they do.

    Obviously, a relatively light brain will help a bird take off and fly so there is selective pressure for lighter brains, while there is also a selective pressure for more clever brains.

    For now, nobody seems to have any hard evidence of a functional difference. Some posters have provided evidence that neurons can have differential roles and even different morphologies but whether this makes the neurons functionally different from each other or whether functionally identical neurons adapt their morphology to their immediate environment and come to play different roles is unclear.
    EB
    Last edited by Speakpigeon; 10-08-2019 at 09:31 AM.

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    Contributor Speakpigeon's Avatar
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    Quote Originally Posted by Politesse View Post
    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by Politesse View Post
    They are certainly larger and longer physically, and there are a number of ways in which their electrical processing is different. We've got these long branching dendrites that seem to allow for much more functional compartmentalization. We also have some weird inhibitory neurons called rose hip cells. Much of the research on this question is younger than a year, I think much more detailed answers will soon be possible.
    I don't mean functional differences between brains or even part thereof, but between neurons. What you say seems to mean that we don't know yet that there are actual functional differences... Am I wrong?
    EB
    You're quite wrong. Neurons are and were the topic of discussion.
    You have provided evidence that neurons can have differential roles and even different morphologies but whether this makes the neurons functionally different or whether functionally identical neurons adapt themselves to their immediate environment in the brain and come to develop different morphologies and play different roles is unclear. Personally, I would be surprised if there was a difference and I am asking for hard evidence, not circumstantial evidence that can be interpreted in different ways.

    Think of this analogy. Humans are broadly all identical. Yet, there are many different roles they can have in the social body and society itself is made of many functionally different parts that are however all entirely made of the same kinds of human beings. So, differences at the level of the system and even morphological differences between neurons are not definitive evidence.
    EB

  7. Top | #17
    Sapere aude Politesse's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by Politesse View Post

    You're quite wrong. Neurons are and were the topic of discussion.
    You have provided evidence that neurons can have differential roles and even different morphologies but whether this makes the neurons functionally different or whether functionally identical neurons adapt themselves to their immediate environment in the brain and come to develop different morphologies and play different roles is unclear. Personally, I would be surprised if there was a difference and I am asking for hard evidence, not circumstantial evidence that can be interpreted in different ways.

    Think of this analogy. Humans are broadly all identical. Yet, there are many different roles they can have in the social body and society itself is made of many functionally different parts that are however all entirely made of the same kinds of human beings. So, differences at the level of the system and even morphological differences between neurons are not definitive evidence.
    EB
    So basically you decided at the beginning of the discussion what the truth was, and are ignoring everything that has been contributed? I see no point in repeating myself.

  8. Top | #18
    Contributor Speakpigeon's Avatar
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    Quote Originally Posted by Politesse View Post
    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by Politesse View Post

    You're quite wrong. Neurons are and were the topic of discussion.
    You have provided evidence that neurons can have differential roles and even different morphologies but whether this makes the neurons functionally different or whether functionally identical neurons adapt themselves to their immediate environment in the brain and come to develop different morphologies and play different roles is unclear. Personally, I would be surprised if there was a difference and I am asking for hard evidence, not circumstantial evidence that can be interpreted in different ways.

    Think of this analogy. Humans are broadly all identical. Yet, there are many different roles they can have in the social body and society itself is made of many functionally different parts that are however all entirely made of the same kinds of human beings. So, differences at the level of the system and even morphological differences between neurons are not definitive evidence.
    EB
    So basically you decided at the beginning of the discussion what the truth was, and are ignoring everything that has been contributed? I see no point in repeating myself.
    No, I clearly explained why I'm not convinced and you choose to ignore that explanation. It's you deciding that your evidence is compelling and that I should accept it as good enough. I explained why I am not convinced and there is no reason to take ombrage.
    EB

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    Contributor Speakpigeon's Avatar
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    This apparently from someone who is a research scientist, and has worked on genetics and developmental biology.

    All neurons do essentially the same thing regardless of whether it’s a worm or a human – propagate membrane potentials in order to produce a response in a connected cell(s). The connected cell(s) may be other neurons or may be effector cells (muscle, endocrine or other glands, skin, epithelial, endothelial, etc.).

    The difference between a worm and a human is not the function of neurons but rather the number of neurons, the complexity of the neuronal network, and the repertoire of genes and receptors that they have to work with.
    The difference between a worm and a human is not the function of neurons.

    The guy is making exactly my point, I think.

    I like empirical evidence very much. Always did.
    EB

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    Mazzie Daius fromderinside's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    This apparently from someone who is a research scientist, and has worked on genetics and developmental biology.

    All neurons do essentially the same thing regardless of whether it’s a worm or a human – propagate membrane potentials in order to produce a response in a connected cell(s). The connected cell(s) may be other neurons or may be effector cells (muscle, endocrine or other glands, skin, epithelial, endothelial, etc.).

    The difference between a worm and a human is not the function of neurons but rather the number of neurons, the complexity of the neuronal network, and the repertoire of genes and receptors that they have to work with.
    The difference between a worm and a human is not the function of neurons.

    The guy is making exactly my point, I think.

    I like empirical evidence very much. Always did.
    EB
    Yet in this article:
    The Evolution of Neuron Types and Cortical Histology in Apes and Human http://allmanlab.caltech.edu/McDonne...oodHof2007.pdf

    reaseachers among all their other analyses of differences in neuron morphology and function among other structural and functional differences that recent hominids have unique mechanisms for handling high levels of glutamate in neurons providing advantages to them in nervous function. Amazing how as you claim no difference there are scientific papers finding differences even among recent hominids.

    Also as I pointed out before as a general statement most sensory mechanisms evolve from neurons and they function very differently form the neurons from which they arose.

    4.21.3.4 Genomic Data Provide Insights into Cortical Specializations. Recent studies of phylogenetic variation in gene p0240 sequences and expression provide additional insights into cortical specializations among hominoids. While most of these studies have been directed at determining the genetic basis for human neural uniqueness (b0215 Enard et al., 2002a; b02202002b; b0130 Caceres et al., 2003; b0210Dorus et al., 2004; b0795Uddinet al., 2004), some molecular data point to changes that occurred at earlier times in the hominoid radiation. For instance, all hominoids have evolved a novel biochemical mechanism to support high levels of glutamate flux in neurotransmission through theretroposition of the gene GLUD1 (b0105 Burki and Kaessmann, 2004). This duplicated gene, GLUD2,which is unique to hominoids, encodes an isotype of the enzyme glutamate dehydrogenase that is expressed in astrocytes. All hominoid GLUD2 sequences contain two key amino acid substitutions that allow the GLUD2 enzyme to be activated in astrocytes during conditions of high glutamatergic neurotransmitter flux. Concordant with this evidence for alterations in the molecular machinery necessary for enhanced neuronal activity in apes, ithas been shown that the gene encoding the cytochrome c oxidase subunit 4-1 underwent rapid non synonymous evolution in the hominoid stem,followed by purifying selection in descendent lineages (b0855 Wildman et al., 2002). Because these nucleotide substitutions have functional consequences for the manner and rate at which electrons are transferred from cytochrome c to oxygen, it is likely that these modifications were selected to serve the needs of cells with high aerobic energy demands,such as neurons.p0245 Also of significance, an alternative splice variant of neuropsin (type II) has originated in recent hominoid evolution (b0485Li et al., 2004). Neuropsin is expressed in hippocampal pyramidal neurons and is involved in neuronal plasticity. The high incidence of polymorphisms in the coding region of this protein in gibbons and orangutans, however, suggests that it may not be functional in these species. In contrast,the coding region of the type II splice form of neuropsin shows relatively little variation in gorillas,chimpanzees, and humans, signifying that it is maintained by functional constraint and that it might be involved in a molecular pathway important for learning and memory in these hominoids.
    The real clinker is the strong evidence that receptor cells are actually neuron evolved cells. A Short History of Nearly Every Sense—The Evolutionary History of Vertebrate Sensory Cell Types

    https://academic.oup.com/icb/article/58/2/301/4993961

    Evolving from filter feeding chordate ancestors, vertebrates adopted a more active life style. These ecological and behavioral changes went along with an elaboration of the vertebrate head including novel complex paired sense organs such as the eyes, inner ears, and olfactory epithelia. However, the photoreceptors, mechanoreceptors, and chemoreceptors used in these sense organs have a long evolutionary history and homologous cell types can be recognized in many other bilaterians or even cnidarians. After briefly introducing some of the major sensory cell types found in vertebrates, this review summarizes the phylogenetic distribution of sensory cell types in metazoans and presents a scenario for the evolutionary history of various sensory cell types involving several cell type diversification and fusion events. It is proposed that the evolution of novel cranial sense organs in vertebrates involved the redeployment of evolutionarily ancient sensory cell types for building larger and more complex sense organs.
    Mechanoreceptors: hair cells The hair cells of the vestibular and auditory sensory areas of the inner ear or the lateral line organs are primary sensory cells, i.e., they do not have an axon (Fig. 2B). Instead they release neurotransmitters from their basal side at a ribbon synapse resembling the synapse of photoreceptors (Matthews and Fuchs 2010) to activate special somatosensory neurons. The latter originate from the same placodes and may indeed be clonally related to hair cells (Satoh and Fekete 2005). On their apical side, hair cells have a “hair bundle” comprising a single nonmotile cilium (kinocilium, with 9 + 2 microtubule doublets) adjacent to a group of microvilli (or “stereocilia”) decreasing in size with increasing distance from the kinocilium.
    Similar arrangements will be fond in smell and vision. Sense organs arouse from neural cells.

    So when you come down on the side of no change in function you immediately run into the problem of sense organs arising from neurons.

    That would be a

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