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May 12, 2024 · Your brain has somewhere between 80 billion and 100 billion neurons. Neurons tend to group together to form neural tracts, which would be like the streets and highways in the city analogy. When you have a thought, neurons in your brain fire up and create electrical impulses. These impulses tend to travel along similar pathways and release tiny ...
- Overview
- 1. How big are our brains?
- 2. What makes a brain?
- 3. How ‘hungry’ are our brains?
- 4. How much of our brains do we use?
- 5. Right- or left-brained?
- 6. How do brains change with age?
- 7. Is perception ‘a controlled hallucination?’
The brain — the central “control unit” of our bodies, repository of memories and emotions. Throughout history, philosophers have believed that the brain may even house that intangible essence that makes us human: the soul. What should we know about our brains?
In a poem written around 1892, American poet Emily Dickinson described the wonder of the human brain.
Her verses express a sense of awe, considering the brain’s marvellous capacities of thought and creativity.
Musing on how this fascinating organ is able to encompass so much information about the self and the world, she wrote:
“The Brain — is wider than the Sky —
For — put them side by side —
Brain size varies widely, depending largely on age, sex, and overall body mass. However, studies have suggested that the adult male brain weighs, on average, about 1,336 grams, whereas the adult female brain weighs around 1,198 grams.
In terms of dimensions, the human brain isn’t the largest. Of all mammals, the sperm whale — an underwater denizen weighing an impressive 35–45 tons — is known to have the biggest brain.
But, of all the animals on Earth, human brains have the largest number of neurons, which are specialized cells that store and transmit information by electrical and chemical signals.
Traditionally, it has been said that the human brain contains approximately 100 billion neurons, but recent investigations have questioned the veracity of that number.
The human brain makes up, alongside the spinal chord, the central nervous system. The brain itself has three main parts:
•the brainstem, which, like a plant’s shoot, is elongated, and which connects the rest of the brain with the spinal chord
•the cerebellum, which is located at the back of the brain and which is deeply involved in regulating movement, motor learning, and maintaining equilibrium
•the cerebrum, which is the largest part of our brains and fills up most of the skull; it houses the cerebral cortex (that has a left and a right hemisphere separated by a long groove) and other, smaller structures, all of which are variously responsible for conscious thought, decision-making, memory and learning processes, communication, and perception of external and internal stimuli
Brains are made of soft tissue, which includes gray and white matter, containing the nerve cells, non-neuronal cells (which help to maintain neurons and brain health), and small blood vessels.
They have a high water content as well as a large amount (nearly 60 percent) of fat.
Despite the fact that the human brain is not a very large organ, its functioning requires a whole lot of energy.
“Although the [human] brain weighs only 2 percent of the body [mass], it alone uses 25 percent of all the energy that your body requires to run per day,” Herculano-Houzel explained in a presentation.
And why does the brain need so much “fuel?” Based on studies of rat models, some scientists have hypothesized that, while most of this energy is expended on maintaining ongoing thought and bodily processes, some of it is probably invested in the upkeep of brain cells’ health.
But, according to some researchers, at first sight, the brain, seemingly inexplicably, uses up a lot of energy during what is known as the “resting state,” when it is not involved in any specific, targeted activities.
According to James Kozloski, “Inactivity correlated networks appear even under anesthesia, and these areas have very high metabolic rates, tipping the brain’s energy budget toward a large investment in the organism’s doing nothing,” he writes.
But Kozloski’s hypothesis is that no large amount of energy is spent for no reason — so why does the brain seem to do it? In fact, he says, it doesn’t.
One long-circulating myth has it that humans typically use only 10 percent of their brain capacity, suggesting that, if only we knew how to “hack into” the other 90 percent, we might be able to unlock amazing abilities.
While it remains unclear exactly where this myth originated and how it spread so speedily, the idea that we could somehow tap into as yet unclaimed brain power is certainly a very attractive one.
Still, nothing could be farther from the truth than this piece of urban lore. Just consider what we discussed above: even in a resting state, the brain is still active and requires energy.
Brain scans have shown that we use pretty much all of our brains all of the time, even when we’re asleep — though patterns of activity, and the intensity of that activity, might differ depending on what we’re doing and what state of wakefulness or sleep we’re in.
“Even when you’re engaged in a task and some neurons are engaged in that task, the rest of your brain is occupied doing other things, which is why, for example, the solution to a problem can emerge after you haven’t been thinking about it for a while, or after a night’s sleep, and that’s because your brain’s constantly active,” said neurologist Krish Sathian, who works at Emory University in Atlanta, GA.
“If it were true that we only use 10 percent of the brain, then we could presumably sustain damage to 90 percent of our brain, with a stroke […] or something like that, and not [experience] any effects, and that’s clearly not true.”
Are you right-brained or left-brained? Any number of Internet quizzes will claim to be able to assess whether you predominantly use the right or left hemisphere of your brain.
And this has implications about your personality: allegedly, left-brained people are supposed to be more mathematically inclined and analytical, while right-brained people are more creative.
But how true is this? Once more the answer, I’m afraid, leans toward “not at all.” While it is true that each of our hemispheres has slightly different roles, individuals do not actually have a “dominant” brain side that governs their personality and abilities.
Instead, research has revealed that people use both of the brain hemispheres pretty much in equal measure.
As we age, parts of our brain begin to shrink naturally and we begin to gradually lose neurons. The frontal lobe and the hippocampus — two key brain regions in regulating cognitive processes, including memory formation and recall — start shrinking when we hit 60 or 70.
This means that we could naturally begin to find learning new things, or performing several tasks at the same time, more challenging than before.
There is some good news, as well, however. Till not too long ago, scientists used to believe that once we started to lose neurons, that would be it — we would be unable to create new brain cells and had to resign ourselves to that.
However, it turns out that this isn’t true. Researcher Sandrine Thuret, from King’s College London in the United Kingdom, has explained that the hippocampus is a crucial part in the adult brain in terms of generating new cells.
(And this makes sense if you consider that it plays an important role in processes of learning and memory.)
The process in which new nerve cells are created in the adult brain is called neurogenesis, and, according to Thuret, estimates suggest that an average adult human will produce “700 new neurons per day in the hippocampus.”
A great mystery of the human brain is linked with consciousness and our perception of reality. The workings of consciousness have fascinated scientists and philosophers alike, and though we are slowly inching closer to an understanding of this phenomenon, much more still remains to be learned.
Anil Seth, a professor of cognitive and computational neuroscience from the University of Sussex in the U.K., who specializes in the study of consciousness, has suggested that this intriguing process is based on a sort of “controlled hallucination,” which our brains generate to make sense of the world.
“Perception — figuring out what’s there — has to be a process of informed guesswork in which the brain combines these sensory signals with its prior expectations of beliefs about the way the world is to form the best guess of what caused those signals.”
Prof. Anil Seth
According to him, in delivering perceptions of things to our consciousness, our brains often make what you might call “informed guesses,” based on how it “expects” things to be.
This explains the uncanny effect of many optical illusions, including the now-notorious “blue and black, or white and gold dress,” when, depending on how we think the light in the picture is, we may see a different color combination.
Apr 21, 2022 · “We know increasingly more about the brain, but always through the prism of these tractable, well-studied parts of the brain and parts of the animal kingdom. If you look at the diversity of animals, there are obviously many more ways that brains have been selected and optimized over the course of evolution.”
Jul 17, 2024 · The brain can be divided into three basic units: the forebrain, the midbrain, and the hindbrain. The hindbrain includes the upper part of the spinal cord, the brain stem, and a wrinkled ball of tissue called the cerebellum. The hindbrain controls the body’s vital functions such as respiration and heart rate. The cerebellum coordinates ...
That’s why Harvard’s Center on the Developing Child is researching the best ways to increase brain-building games, reduce childhood stress, and promote responsive relationships and language-rich experiences. Since founding the first Neurobiology Department, Harvard has fostered researchers learning how the brain works and scientists fixing ...
Feb 8, 2021 · Whenever a key object shifts across our field of view — either because it moved or our eyes did — the brain immediately transfers a memory of it by re-encoding it among neurons in the opposite brain hemisphere. The finding, published in Neuron by neuroscientists at the Picower Institute for Learning and Memory, explains via experiments in ...
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Mar 26, 2021 · A brain activity pattern in the anterior lateral prefrontal cortex tracks this estimate of how well we are likely to do. “External chances” are the chances of things happening in the environment around us, but this new research shows that we – and our brains – also track “internal chances” – our own sense of how likely we are to do something.
