Unlike the heart or kidney, which have a small, defined set of cell types, we still do not have a taxonomy of neurons, and neuroscientists still argue whether specific types of neurons are unique to humans. But there is no disputing that neurons are only about 10 percent of the cells in the human brain.
Thomas R. Insel
The well-being of a neuron depends on its ability to communicate with other neurons. Studies have shown that electrical and chemical stimulation from both a neuron's inputs and its targets support vital cellular processes. Neurons unable to connect effectively with other neurons atrophy. Useless, an abandoned neuron will die.
Most of the different types of cells in our body die and are replaced every few weeks or months. However, neurons, the primary cell of the nervous system, do not multiply (for the most part) after we are born. That means that the majority of the neurons in your brain today are as old as you are. This longevity of the neurons partially accounts for why we feel pretty much the same on the inside at the age of 10 as we do at age 30 or 77.
Jill Bolte Taylor
Even then, more than a year earlier, there were neurons in her head, not far from her ears, that were being strangled to death, too quietly for her to hear them. Some would argue that things were going so insiduously wrong that the neurons themselves initiated events that would lead to their own destruction. Whether it was molecular murder or cellular suicide, they were unable to warn her of what was happening before they died.
There are two types of empathy: the positive empathy and the negative empathy. When we are fully carried away by the unaware activities of the mirror neurons, we are under the trap of negative empathy. The negative empathy generates attachments. Out of these attachments suffering follows. Negative empathy is a kind of reaction to a situation, whereas positive empathy is internal response of peace love and tranquility... In positive empathy, your deep tranquility, joy and peace activates the mirror neurons of the others, whereas in negative empathy your mirror neurons are activated by the disturbance of others.
There are 100 billion neurons in the adult human brain, and each neuron makes something like 1,000 to 10,000 contacts with other neurons in the brain. Based on this, people have calculated that the number of permutations and combinations of brain activity exceeds the number of elementary particles in the universe.
Vilayanur S. Ramachandran
Nature is the best teacher. It gives us the best direction. Nothing can exist in nature by its own. Even neurons, the stars of the nervous system, cannot exist on their own. They need glial cells, the supporting cast that keep the environment safe and clean for the activity of neurons. There are 86 billion neuron and 85 billion glial cells in the brain, that is, there is one-to-one relationship between neurons and glial cells there as the one between men and women in society. The existence of each is very, very essential, one cannot exist without another. But only one of two is a star of the nervous system, only these stars - neurons can gather information, interpret it, send signals and lead the brain and a whole body. Although the existence of another, a glial cell, is very, very important, however, it is not a star but only a supporter of the star. Both of them cannot be stars. Neither can be both men and women in society. Only one of the two can be decisive factor in making history. only one of the two should be chosen for this mission. History had already chosen men for it long, long before we were born. It used to be so, it is so, and it should be so.
Our brains contain one hundred billion nerve cells (neurons). Each neuron makes links with ten thousand other neurons to form an incredible three dimensional grid. This grid therefore contains a thousand trillion connections - that's 1, 000, 000, 000, 000, 000 (a quadrillion). It's hard to imagine this, so let's visualise each connection as a disc that's 1mm thick. Stack up the quadrillion discs on top of each other and they will reach the sun (which is ninety-three million miles from the earth) and back, three times over.
Concepts of memory tend to reflect the technology of the times. Plato and Aristotle saw memories as thoughts inscribed on wax tablets that could be erased easily and used again. These days, we tend to think of memory as a camera or a video recorder, filming, storing, and recycling the vast troves of data we accumulate throughout our lives. In practice, though, every memory we retain depends upon a chain of chemical interactions that connect millions of neurons to one another. Those neurons never touch; instead, they communicate through tiny gaps, or synapses, that surround each of them. Every neuron has branching filaments, called dendrites, that receive chemical signals from other nerve cells and send the information across the synapse to the body of the next cell. The typical human brain has trillions of these connections. When we learn something, chemicals in the brain strengthen the synapses that connect neurons. Long-term memories, built from new proteins, change those synaptic networks constantly; inevitably, some grow weaker and others, as they absorb new information, grow more powerful.
What do we mean by "knowledge" or "understanding"? And how do billions of neurons achieve them? These are complete mysteries. Admittedly, cognitive neuroscientists are still very vague about the exact meaning of words like "understand," "think," and indeed the word "meaning" itself.
Vilayanur S. Ramachandran
As information processing machines, our ability to process data about the external world begins at the level of sensory perception. Although most of us are rarely aware of it, our sensory receptors are designed to detect information at the energy level. Because everything around us - the air we breathe, even the materials we use to build with, are composed of spinning and vibrating atomic particles, you and I are literally swimming in a turbulent sea of electromagnetic fields. We are part of it. We are enveloped within in, and through our sensory apparatus we experience what is. Each of our sensory systems is made up of a complex cascade of neurons that process the incoming neural code from the level of the receptor to specific areas within the brain. Each group of neurons along the cascade alters or enhances the code, and passes it on to the next set of cells in the system, which further defines and refines the message. By the time the code reaches the outermost portion of our brain, the higher levels of the cerebral cortex, we become conscious of the stimulation. However, if any of the cells along the pathway fail in their ability to function normally, then the final perception is skewed away from normal reality.
Jill Bolte Taylor
As a bio major, I figured "free will" meant chemicals in your brain telling you what to do, the molecules bouncing around in a way that felt like choosing but was actually the dance of little gears--neurons and hormones bubbling up into decisions like clockwork. You don't use your body; it uses you.
The newborn infant is now seen to be wired with awesome precision... This marvelous robot will be launched into the world under the care of its parents... But to what extent does the wiring of the neurons, so undeniably encoded in the genes, preordain the directions that social development will follow?
E. O. Wilson
Life and consciousness are the two great mysteries. Actually, their substrates are the inanimate. And how do you get from neurons shooting around in the brain to the thought that pops up in your head and mine? There's something deeply mysterious about that. And if you're not struck by the mystery, I think you haven't thought about it.
For me, consciousness is the most interesting unsolved problem of science, and, in fact, we may never know what it is about a particular arrangement of neurons that gives rise to consciousness. Our consciousness, like the air we breathe or like the passage of time, is central to our existence as intelligent beings.
[O]ne of the most influential approaches to thinking about memory in recent years, known as connectionism, has abandoned the idea that a memory is an activated picture of a past event. Connectionist or neural network models are based on the principle that the brain stores engrams by increasing the strength of connections between different neurons that participate in encoding an experience. When we encode an experience, connections between active neurons become stronger, and this specific pattern of brain activity constitutes the engram. Later, as we try to remember the experience, a retrieval cue will induce another pattern of activity in the brain. If this pattern is similar enough to a previously encoded pattern, remembering will occur. The "memory" in a neural network model is not simply an activated engram, however. It is a unique pattern that emerges from the pooled contributions of the cue and the engram. A neural network combines information in the present environment with patterns that have been stored in the past, and the resulting mixture of the two is what the network remembers... When we remember, we complete a pattern with the best match available in memory; we do not shine a spotlight on a stored picture.
Daniel L. Schacter
Today, when we look at a brain, we see an intricate network of billions of neurons in constant, crackling communication, a chemical labyrinth that senses the world outside and within, produces love and sorrow, keeps our hearts beating and lungs breathing, composes our thoughts, and constructs our consciousness.
Everything a person is and everything he knows resides in the tangled thicket of his intertwined neurons. These fateful, tiny bridges number in the quadrillions, but they spring from just two sources: DNA and daily life. The genetic code calls some synapses into being, while experience engenders and modifies others.(148)
When the brain is working to remember something, similar patterns of neurons fire as they did during the perception of the original event. These networks are linked, and each time we revisit them, they become stronger and more associated. But they need the proper retrieval cues--words, smells, images-- for them to be brought back as memories
The brain, or cerebrum, is a material entity located inside the skull which may be inspected, touched, weighed, and measured. It is composed of chemicals, enzymes, and humors which may be analyzed. Its structure is characterized by neurons, pathways, and synapses which may be examined directly when they are properly magnified.
Jose Manuel Rodriguez Delgado
Consciousness is somehow a by-product of the simultaneous, high frequency firing of neurons in different parts of the brain. It's the meshing of these frequencies that generates consciousness, just as tones from individual instruments produce the rich, complex, & seamless sounds of a symphony orchestra
An idea: a theory or an equation, might sit around unnoticed for decades, centuries, even, before it's rediscovered and put to some use. That's how it works: it makes connections with other ideas, other knowledge, gathering momentum all the time, growing exponentially if it's strong enough. Just like it would connect and grow within the billions of neurons in a single mind.
Since the universe must contain millions of appropriate planets, consciousness in some form - but not with the paired eyes and limbs, and the brain built of neurons in the only example we know - may evolve frequently. But if only one origin of life in a million ever leads to consciousness, then Martian bacteria most emphatically do not imply Little Green Men.
Stephen Jay Gould
Cognitive neuroscience is entering an exciting era in which new technologies and ideas are making it possible to study the neural basis of cognition, perception, memory and emotion at the level of networks of interacting neurons, the level at which we believe many of the important operations of the brain take place.
But the remembering is imperfect; the instructions for which neurons need to be gathered and how exactly they need to fire are weak and degraded, leading to a representation that is only a dim and often inaccurate copy of the real experience. Memory is fiction. It may present itself to us as fact, but it is highly susceptible to distortion. Memory is not just replaying, but a rewriting.
Daniel J. Levitin
The brain is the most complicated organ in the universe. We have learned a lot about other human organs. We know how the heart pumps and how the kidney does what it does. To a certain degree, we have read the letters of the human genome. But the brain has 100 billion neurons. Each one of those has about 10,000 connections.
In my view, while the single neuron is the basic anatomical and information processing-signaling unit of the brain, it is not capable of generating behaviors and, ultimately, thinking. Instead, the true functional unit of the central nervous system is a population of neurons, or neural ensembles or cell assemblies.
When you travel, you're forced to have new thoughts. "Is this alley safe?" "Is this the right bus?" "Was this meat ever a house pet?" It doesn't even matter what the new thoughts are, it feels so good to just have some variety. And it's a reboot for your brain. I can feel the neurons making new connections again with new problems to solve, clawing their way back to their nimbler, younger days.
My mitochondria comprise a very large proportion of me. I cannot do the calculation, but I suppose there is almost as much of them in sheer dry bulk as there is the rest of me. Looked at in this way, I could be taken for a very large, motile colony of respiring bacteria, operating a complex system of nuclei, microtubules, and neurons for the pleasure and sustenance of their families, and running, at the moment, a typewriter.
Anthony watched him, dumbfounded, and then turned to Lucy. 'What have you done with Zack's brain?' Lucy stood to follow Zack. 'What brain? I don't think he has one. I think he's just one giant exposed nerve ending. I swear sometimes at night, I can hear his neurons snapping like popcorn.
All that's known is this: there is no central processor, no single computer. Nothing that simple. Millions of neurons process information simultaneously and in parallel, not linearly, but the actual chemistry and electrical properties of that integrative process are still being mapped. Even so, it seems odd that during the evolution of brain circuitry and thinking, the ability to understand itself did not get wired in. Such built-in innocence seems like a terrible oversight.
In our constant search for meaning in this baffling and temporary existence, trapped as we are within our three pounds of neurons, it is sometimes hard to tell what is real. We often invent what isn't there. Or ignore what is. We try to impose order, both in our minds and in our conceptions of external reality. We try to connect. We try to find truth. We dream and we hope. And underneath all of these strivings, we are haunted by the suspicion that what we see and understand of the world is only a tiny piece of the whole.
Destiny is no more than the fulfillment of purposive potentialities within us. The human cerebral cortex is a single sheet composed of more neurons than there are stars in the known universe folded like a paper crane to fit in a quart-sized cubbyhole; there is enough potential energy in a single person that if released would equal thirty hydrogen bombs. Destiny is nothing to sneeze at!
The emotional mind likewise transcends the facile and appealing dualism separating its psychological and biological aspects. Physical mechanisms produce one's experience of the world. Experience, in turn, remodels the neurons whose chemoelectric messages create consciousness. Selecting one strand of that eternal braid and assigning it primacy is the height of capriciousness. (168)
There is one brain organ that is optimised for understanding and articulating logical processes and that is the outer layer of the brain, called the cerebral cortex. Unlike the rest of the brain, this relatively recent evolutionary development is rather flat, only about 0.32 cm (0.12 in) thick and includes a mere 6 million neurons. This elaborately folded organ provides us with what little competence we do possess for understanding what we do and who we do it.
The brain immediately confronts us with its great complexity. The human brain weighs only three to four pounds but contains about 100 billion neurons. Although that extraordinary number is of the same order of magnitude as the number of stars in the Milky Way, it cannot account for the complexity of the brain. The liver probably contains 100 million cells, but 1,000 livers do not add up to a rich inner life.
The structure of the human brain is enormously complex. It contains about 10 billion nerve cells (neurons), which are interlinked in a vast network through 1,000 billion junctions (synapses). The whole brain can be divided into subsections, or sub-networks, which communicate with each other in a network fashion. All this results in intricate patterns of intertwined webs, networks of nesting within larger networks.