What happens once a brain is full?

What happens once a brain is full?

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I just read the answer to this question, and it got me thinking…

If the human brain (or any other brain) has a finite amount of storage, what would happen once the brain has taken in its maximum amount of information?

This is, or course, assuming that the individual can live long enough to acquire that much information.

I would take a guess that just like how we forget things all the time, the new memories would "override" some older ones.

Has there been any research or hypotheses on a brain's behavior once the its storage has maxed out?

It's very likely that memory is "lossy" and holographic, such that you can keep adding more information indefinitely, but retain it with less and less accuracy.

Memory isn't a digital storage system with X gigabytes of capacity, and the inputs to memory aren't neat little packets. What we remember are a web of associations and patterns. Vastly oversimplified, we group similar memories together into a baseline, and remember the deviations from that.

If you walk the same route to work every day, you take in a huge amount of information the first few days: stretches of residential buildings, cars parked on the street, portions of curb painted red, trash in the gutters. In successive days different cars will come and go, front yards will get overgrown and trimmed, etc, but these details get mixed in with what you saw the first few days into a blurrier and blurrier sort of average. Trillions of impressions from hundreds of days take up very little more capacity than the first day did, and still tell you what you need to know about the route.

Imagine that there's a particular green car of common make and model, that was parked in front of a certain house about 3/4 of the time for the first hundred days you walked the route. Your memory reduces this to something like "green car usually along here somewhere". If the green car stops parking there, you'll probably notice "green car not there today" because that's a contrast to the common case that you've memorized. But if a week goes by with no sightings of the green car, it's very hard to remember which day you last saw it, because you don't remember individual sightings. (I actually had this happen to me with my own car; I discovered it stolen on a Wednesday and could not for the life of me recall whether I'd seen it on Monday or Tuesday even though I'd walked past the spot it should have been parked both days.)

As you remember more things, you remember them in less and less detail; you can't remember if you've been to New Orleans once or twice; you can't remember which memories were from your first trip to Las Vegas or your second, etc. So the brain never becomes full, it just becomes fuzzy.

Three possible mechanisms are mentioned in the first referenced article [1]:

  1. Attentional blink - the failure to detect a (visual) stimulus [2].
  2. Visual short-term memory - non-permanent storage of visual information over an extended period of time [3].
  3. Psychological refractory period - the period of time during which the response to a second stimulus is significantly slowed because a first stimulus is still being processed [4, 5].


  1. Marois R, Ivanoff J. Capacity limits of information processing in the brain. Trends Cogn. Sci. (Regul. Ed.). 2005 Jun;9(6):296-305. doi: 10.1016/j.tics.2005.04.010. PubMed PMID: 15925809. Full text available on
  2. Wikipedia contributors, "Attentional blink," Wikipedia, The Free Encyclopedia, (accessed July 12, 2014).
  3. Wikipedia contributors, "Visual short-term memory," Wikipedia, The Free Encyclopedia, (accessed July 12, 2014).
  4. Pashler H. Dual-task interference in simple tasks: data and theory. Psychol Bull. 1994 Sep;116(2):220-44. PubMed PMID: 7972591.
  5. Wikipedia contributors, "Psychological refractory period," Wikipedia, The Free Encyclopedia, (accessed July 12, 2014).

What Happens to the Brain During Spiritual Experiences?

The field of neurotheology uses science to try to understand religion, and vice versa.

“Everyone philosophizes,” writes neuroscientist Dr. Andrew Newberg in his latest book, The Metaphysical Mind: Probing the Biology of Philosophical Thought. We all speculate about the meaning of all kinds of things, from everyday concerns about dealing with a co-worker to our ultimate beliefs about the purpose of existence. Accompanying solutions we find to these problems, there’s a range of satisfied feelings, from “ah-ha” or light-bulb moments upon solving an everyday problem to ecstatic feelings during mystical experiences.

Since everyday and spiritual concerns are variations of the same thinking processes, Newberg thinks it’s essential to examine how people experience spirituality in order to fully understand how their brains work. Looking at the bigger questions has already provided practical applications for improving mental and physical health.

Newberg is a pioneer in the field of neurotheology, the neurological study of religious and spiritual experiences. In the 1990s, he began his work in the field by scanning what happens in people’s brains when they meditate, because it is a spiritual practice that is relatively easy to monitor.

Since then, he’s looked at around 150 brain scans, including those of Buddhists, nuns, atheists, Pentecostals speaking in tongues, and Brazilian mediums practicing psychography—the channeling of messages from the dead through handwriting.

Scientists discover why the human brain is so big

It is one of the defining attributes of being human: when compared with our closest primate relatives, we have incredibly large brains.

Now scientists have shed light on the reasons for the difference, by collecting cells from humans, chimps and gorillas and turning them into lumps of brain in the laboratory.

Tests on the tiny “brain organoids” reveal a hitherto unknown molecular switch that controls brain growth and makes the human organ three times larger than brains in the great apes.

Tinker with the switch and the human brain loses its growth advantage, while the great ape brain can be made to grow more like a human’s.

“What we see is a difference in cellular behaviour very, very early on that allows the human brain to grow larger,” said Dr Madeleine Lancaster, a developmental biologist at the Medical Research Council’s Laboratory of Molecular Biology in Cambridge. “We are able to account for almost all of the size difference.”

The healthy human brain typically reaches about 1,500cm 3 in adulthood, roughly three times the size of the 500cm 3 gorilla brain or the 400cm 3 chimp brain. But working out why has been fraught with difficulty, not least because developing human and great ape brains cannot easily be studied.

In an effort to understand the process, Lancaster and her colleagues collected cells, often left over from medical tests or operations, from humans, gorillas and chimps, and reprogrammed them into stem cells. They then grew these cells in such a way that encouraged them to turn into brain organoids – little lumps of brain tissue a few millimetres wide.

After several weeks, the human brain organoids were by far the largest of the lot, and close examination revealed why. In human brain tissue, so-called neural progenitor cells – which go on to make all of the cells in the brain – divided more than those in great ape brain tissue.

Lancaster, whose study is published in Cell, added: “You have an increase in the number of those cells, so once they switch to making the different brain cells, including neurons, you have more to start with, so you get an increase in the whole population of brain cells across the entire cortex.”

Mathematical modelling of the process showed that the difference in cell proliferation happens so early in brain development, that it ultimately leads to a near doubling in the number of neurons in the adult human cerebral cortex compared with that in the great apes.

The researchers went on to identify a gene that is crucial to the process. Known as Zeb2, it switches on later in human tissue, allowing the cells to divide more before they mature. Tests showed that delaying the effects of Zeb2 made gorilla brain tissue grow larger, while turning it on sooner in human brain organoids made them grow more like the ape ones.

John Mason, professor of molecular neural development at the University of Edinburgh, who was not involved in the research, said it highlighted the power of organoids for the study of brain development.

“It’s important to understand how the brain develops normally, partly because it helps us understand what makes humans unique and partly because it can give us important insights into how neurodevelopmental disorders can arise,” he said.

“Brain size can be affected in some neurodevelopment disorders, for example macrocephaly is a feature of some autism spectrum disorders, so understanding these very fundamental processes of embryonic brain development could lead to better understanding of such disorders,” he added.

The first few years of a child's life are a time of rapid brain growth. At birth, every neuron in the cerebral cortex has an estimated 2,500 synapses by the age of three, this number has grown to a whopping 15,000 synapses per neuron.

The average adult, however, has about half that number of synapses. Why? Because as we gain new experiences, some connections are strengthened while others are eliminated. This process is known as synaptic pruning.

Neurons that are used frequently develop stronger connections and those that are rarely or never used eventually die.

By developing new connections and pruning away weak ones, the brain is able to adapt to the changing environment.

5 Amazing Things Your Brain Does While You Sleep

We spend a third of our lives sleeping, an activity as crucial to our health and well-being as eating. But exactly why we need sleep hasn't always been clear. We know that sleep makes us feel more energized and improves our mood, but what's really happening in the brain and body when we're at rest?

Research has identified a number of reasons that sleep is critical to our health. When we're sleeping, the brain is anything but inactive. In fact, during sleep, neurons in the brain fire nearly as much as they do during waking hours -- so it should come as no surprise that what happens during our resting hours is extremely important to a number brain and cognitive functions.

Here are five incredible things your brain does while you're asleep -- and good reason to get some shuteye tonight:

Makes decisions.

The brain can process information and prepare for actions during sleep, effectively making decisions while unconscious, new research has found.

A recent study published in the journal Current Biology found that the brain processes complex stimuli during sleep, and uses this information to make decisions while awake. The researchers asked participants to categorize spoken words that were separated into different categories -- words referring to animals or objects and real words vs. fake words -- and asked to indicate the category of the word they heard by pressing right or left buttons. When the task become automatic, the subjects were asked to continue but also told that they could fall asleep (they were lying in a dark room). When the subjects were asleep, the researchers began introducing new words from the same categories. Brain monitoring devices showed that even when the subjects were sleeping, their brains continued to prepare the motor function to create right and left responses based on the meaning of the words they heard.

When the participants woke up, however, they had no recollection of the words they heard.

"Not only did they process complex information while being completely asleep, but they did it unconsciously," researchers Thomas Andrillon and Sid Kouider write in the Washington Post. "Our work sheds new light about the brain’s ability to process information while asleep but also while being unconscious."

Creates and consolidates memories.

While you're asleep, the brain is busy forming new memories, consolidating older ones, and linking more recent with earlier memories, during both REM and non-REM sleep. Lack of rest could have a significant affect the hippocampus, an area of the brain involved in memory creation and consolidation.

For this reason, sleep plays a very important role in learning -- it helps us to cement the new information we're taking in for better later recall.

“We’ve learned that sleep before learning helps prepare your brain for initial formation of memories,” Dr. Matthew Walker, a University of California, Berkeley sleep researcher, tells the National Institutes of Health. “And then, sleep after learning is essential to help save and cement that new information into the architecture of the brain, meaning that you’re less likely to forget it.”

Think twice before pulling an all-nighter to study for your next exam: If you don't sleep, your ability to learn new information could drop by up to 40 percent, Walker estimates.

Makes creative connections.

Sleep can be a powerful creativity-booster, as the mind in an unconscious resting state can make surprising new connections that it perhaps wouldn't have made in a waking state.

A 2007 University of California at Berkeley study found that sleep can foster "remote associates," or unusual connections, in the brain -- which could lead to a major "a-ha" moment upon waking. Upon waking from sleep, people are 33 percent more likely to make connections between seemingly distantly related ideas.

Clears out toxins.

A series of 2013 studies found that an important function of sleep may be to give the brain a chance to do a little housekeeping.

Researchers at the University of Rochester found that during sleep, the brains of mice clear out damaging molecules associated with neurodegeneration. The space between brain cells actually increased while the mice were unconscious, allowing the brain to flush out the toxic molecules that built up during waking hours.

If we're not getting enough sleep, our brains don't have adequate time to clear out toxins, which could potentially have the effect of accelerating neurodegenerative diseases like Parkinson's and Alzheimer's.

Learns and remembers how to perform physical tasks.

The brain stores information into long-term memory through something known as sleep spindles, short bursts of brain waves at strong frequencies that occur during REM sleep.

This process can be particularly helpful for storing information related to motor tasks, like driving, swinging a tennis racquet or practicing a new dance move, so that these tasks become automatic. What happens during REM sleep is that the brain transfers short-term memories stored in the motor cortex to the temporal lobe, where they become long-term memories.

"Practice during sleep is essential for later performance," James B. Maas, a sleep scientist at Cornell University, told the American Psychological Association. "If you want to improve your golf game, sleep longer."

The Brain as a Muse

In the brain, neurons are connected in pathways. One neuron, if it receives enough input, will fire a signal to the next one down the line. As more signals get passed between these neurons, that connection is strengthened. Neuroscientists explain this process using the pneumonic, “fire together, wire together,” and it’s essentially how learning happens.

As early as the 1940s, key thinkers have developed computer models based on the biology of the human brain. To create neural networks in computers, scientists create links between different processing elements in the system, modeled after the transfer of signal between synapses in the brain. Each of these connections has a so-called weight, which indicates how strong the connection between an input and output is. Much like in the biological brain, these weights can be strengthened or weakened based on how the computer system is trained.

Artificial neural networks are a clunky approximation of the biological brain’s true processing power, though. In many versions of ANNs, layers of neurons are stacked atop each other. In each layer, these neurons receive signals from the previous layer before setting off all the neurons in the next. Triggering each input and output in one direction like this can bog down the system’s processing power and require much more energy. In the era of deep learning, the resources needed for a best-in-class AI model has doubled every 3.4 months , on average. And as artificial intelligence systems become bigger and more complex, efficiency is becoming increasingly important.

“As its design becomes more and more sophisticated, you require more and more computational resources — you require much more power,” says Wenzhe Guo , a student of electrical and computer engineering at King Abdullah University of Science and Technology.

To mediate this problem, scientists look back to the brain for clues. In recent years, researchers have made great advancements in the development of spiking neural networks (SNN), a class of ANN based more closely on biology. Under the SNN model, individual neurons trigger other neurons only when they are needed. This emulates the “spike” that triggers the passage of signals through biological neurons. This asynchronous approach ensures the system is only powering an interaction when it’s needed for a certain action.

Guo is the lead researcher on a team from which programmed a low-cost microchip to use SNN technology. His team showed that their chip was 20 times faster and 200 times more energy-efficient than other neural network platforms. Moving away from ANNs, which are simplistic approximations of the brain, he says, opens new opportunities for speed and efficiency.

Major companies have begun to harness the power of the SNN model to create and train complex neuromorphic chips, an algorithmic-based AI that more closely mirrors how the human brain interacts with the world. IBM’s TrueNorth , unveiled in 2019, contains one million neurons and 256 million synapses on a 28-nanometer chip. Intel’s Loihi chip contains 130,000 neurons in 14 nanometers and is capable of continuous and autonomous learning.

What Happens When an Amoeba “Eats” Your Brain?

Last week, nine-year-old Hally Yust died after contracting a rare brain-eating amoeba infection while swimming near her family&rsquos home in Kansas.

The organism responsible, Naegleria fowleri, dwells in warm freshwater lakes and rivers and usually targets children and young adults. Once in the brain it causes a swelling called primary meningoencephalitis. The infection is almost universally fatal: it kills more than 97 percent of its victims within days.

Although deadly, infections are exceedingly uncommon&mdashthere were only 34 reported in the U.S. during the past 10 years&mdashbut evidence suggests they may be increasing. Prior to 2010 more than half of cases came from Florida, Texas and other southern states. Since then, however, infections have popped up as far north as Minnesota.

&ldquoWe&rsquore seeing it in states where we hadn&rsquot seen cases before,&rdquo says Jennifer Cope, an epidemiologist and expert in amoeba infections at the U.S. Centers for Disease Control and Prevention. The expanding range of Naegleria infections could potentially be related to climate change, she adds, as the organism thrives in warmer temperatures. &ldquoIt&rsquos something we&rsquore definitely keeping an eye on.&rdquo

Still, &ldquowhen it comes to Naegleria there&rsquos a lot we don&rsquot know,&rdquo Cope says&mdashincluding why it chooses its victims. The amoeba has strategies to evade the immune system, and treatment options are meager partly because of how fast the infection progresses.

But research suggests that the infectioncan be stopped if it is caught soon enough. So what happens during an N. fowleri infection?

The microscopic amoebae, which can be suspended in water or nestled in soil, enter the body when water goes up the nose. After attaching to the mucous membranes in the nasal cavity, N. fowleri burrows into the olfactory nerve, the structure that enables our sense of smell and leads directly to the brain. It probably takes more than a drop of liquid to trigger a Naegleria infection infections usually occur in people who have been engaging in water sports or other activities that may forcefully suffuse the nose with lots of water&mdashdiving, waterskiing, wakeboarding, and in one case a baptism dunking.

It turns out that "brain eating" is actually a pretty accurate description for what the amoeba does. After reaching the olfactory bulbs, N. fowleri feasts on the tissue there using suction-cup-like structures on its surface. This destruction leads to the first symptoms&mdashloss of smell and taste&mdashabout five days after the infection sets in.

From there the organisms move to the rest of the brain, first gobbling up the protective covering that surrounds the central nervous system. When the body notices that something is wrong, it sends immune cells to combat the infection, causing the surrounding area to become inflamed. It is this inflammation, rather than the loss of brain tissue, that contributes most to the early symptoms of headache, nausea, vomiting and stiff neck. Neck stiffness in particular is attributable to the inflammation, as the swelling around the spinal cord makes it impossible to flex the muscles.

As N. fowleri consumes more tissue and penetrates deeper into the brain, the secondary symptoms set in. They include delirium, hallucinations, confusion and seizures. The frontal lobes of the brain, which are associated with planning and emotional control, tend to be affected most because of the path the olfactory nerve takes. &ldquoBut after that there&rsquos kind of no rhyme or reason&mdashall of the brain can be affected as the infection progresses,&rdquo Cope says.

Ultimately what causes death is not the loss of grey matter but the extreme pressure in the skull from the inflammation and swelling related to the body&rsquos fight against the infection. Increasing pressure forces the brain down into where the brain stem meets the spinal cord, eventually severing the connection between the two. Most patients die from the resulting respiratory failure less than two weeks after symptoms begin.

The threat of contracting an N. fowleri infection is remote (vastly more people die every year from drowning), but you can take some measures to lower your risk even further. Cope recommends using nose plugs and not immersing your head fully under water when swimming. She also counsels against kicking up sediment, which can shake the amoeba loose.

More effective treatments may be on the horizon. Last year, the U.S. Food and Drug Administration approved Miltefosine, originally intended as an anti-cancer treatment. In 2013, two people in the U.S. survived N. fowleri when they took the drug (and others) soon after being infected.

And last month, scientists sequenced the amoeba&rsquos genome for the first time. Their insights may help us understand what makes it so virulent and point the way to better treatments.

Toward a Policy-Relevant Neuroscientific Research Agenda

Public policy is struggling to keep up with burgeoning interest in cognitive neuroscience and neuroimaging [51]. In a rush to assign biological explanations for behavior, adolescents may be caught in the middle. Policy scholar Robert Blank comments, “We have not kept up in terms of policy mechanisms that anticipate the implications beyond the technologies. We have little evidence that there is any anticipatory policy. Most policies tend to be reactive” [51]. There is a need to situate research from the brain sciences in the broader context of adolescent developmental science, and to find ways to communicate the complex relationships among biology, behavior, and context in ways that resonate with policymakers and research consumers.

Furthermore, the time is right to advance collaborative, multidisciplinary research agendas that are explicit in the desire to link brain structure to function as well as adolescent behavior and implications for policy [52].

Ultimately, the goal is to be able to articulate the conditions under which adolescents’ competence, or demonstrated maturity, is most vulnerable and most resilient. Resilience, it seems, is often overlooked in contemporary discussions of adolescent maturity and brain development. Indeed, the focus on pathologic conditions, deficits, reduced capacity, and age-based risks overshadows the enormous opportunity for brain science to illuminate the unique strengths and potentialities of the adolescent brain. So, too, can this information inform policies that help to reinforce and perpetuate opportunities for adolescents to thrive in this stage of development, not just survive.

Q: Some patients with COVID-19 in their 30s and 40s are having strokes. Why is that happening?

A: While we haven&rsquot had any of these young stroke patients at Johns Hopkins, I have seen reports of these incidents from colleagues in New York and China.

It may have something to do with the hyperactive blood-clotting system in these patients. Another system that is hyperactivated in patients with COVID-19 is the endothelial system, which consists of the cells that form the barrier between blood vessels and body tissue. This system is more biologically active in younger patients, and the combination of hyperactive endothelial and blood-clotting systems puts these patients at a major risk for developing blood clots.

That said, it would be premature to conclude from available data that COVID-19 preferentially causes strokes in younger patients. It is also plausible that there&rsquos an increase in stroke in COVID-19 patients of all ages.

Urges and appetites

Beneath the forebrain lie more primitive brain regions. The limbic system, common to all mammals, deals with urges and appetites. Emotions are most closely linked with structures called the amygdala, caudate nucleus and putamen. Also in the limbic brain are the hippocampus – vital for forming new memories the thalamus – a kind of sensory relay station and the hypothalamus, which regulates bodily functions via hormone release from the pituitary gland.

The back of the brain has a highly convoluted and folded swelling called the cerebellum, which stores patterns of movement, habits and repeated tasks – things we can do without thinking about them.

The most primitive parts, the midbrain and brain stem, control the bodily functions we have no conscious control of, such as breathing, heart rate, blood pressure, sleep patterns, and so on. They also control signals that pass between the brain and the rest of the body, through the spinal cord.

Though we have discovered an enormous amount about the brain, huge and crucial mysteries remain. One of the most important is how does the brain produces our conscious experiences?

The vast majority of the brain’s activity is subconscious. But our conscious thoughts, sensations and perceptions – what define us as humans – cannot yet be explained in terms of brain activity.