Ikigai Daily
Menu
WonderBrain fact

The default mode network is a set of brain regions that becomes more active when the mind turns inward, to memories, plans or other people, and quietens during many tasks that need attention on the outside world.

Neuroscience

Mind

The story behind the card

The idea that the brain stays busy at rest goes back to Hans Berger, inventor of the EEG, which records the brain's electrical activity through the scalp. In 1929 he reported that these rhythms continue when a person is doing nothing. In the 1990s PET scans, which track blood flow and energy use, showed that the same set of regions reliably became less active when volunteers started a task, and in 2001 the American neurologist Marcus Raichle named this pattern the brain's “default mode”. The network's main hubs lie along the midline of the brain, at the front and towards the back. It is involved in recalling your own past, imagining the future and thinking about what others feel. In Alzheimer's disease its regions use less energy, and amyloid plaques, clumps of a sticky protein typical of the disease, build up there even before symptoms appear.

Türkçe oku
Zihnimiz anılara, planlara ya da başka insanlara daldığında beynin “varsayılan mod ağı” denen bölgeleri daha etkin hâle gelir. Dikkatimizi dış dünyaya vermemiz gereken birçok işte ise bu ağ sakinleşir.

Beynin dinlenirken de çalıştığını ilk fark edenlerden biri, beynin elektriksel etkinliğini kafa derisinden kaydeden EEG'yi geliştiren Hans Berger'di. Berger 1929'da, kişi hiçbir şey yapmazken de bu elektriksel ritimlerin sürdüğünü bildirdi. 1990'larda PET taramaları, yani beyindeki kan akışını ve enerji kullanımını izleyen görüntüler, gönüllüler bir işe başladığında hep aynı bölgelerin sakinleştiğini gösterdi. Amerikalı nörolog Marcus Raichle 2001'de bu örüntüye beynin “varsayılan modu” adını verdi. Ağın ana merkezleri beynin orta hattında, ön ve arka bölgelerde yer alır. Ağ, insanın kendi geçmişini hatırlamasında, geleceği hayal etmesinde ve başkalarının ne hissettiğini düşünmesinde rol oynar. Alzheimer hastalığında bu bölgeler daha az enerji harcar; hastalığa özgü amiloid plakları, yani yapışkan protein kümeleri, belirtiler ortaya çıkmadan önce bile burada birikir.

Sources and further reading

Background reading: Default mode network
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderScience

Deliberately smiling can make people feel slightly happier. In 2022 a study of nearly 4,000 people in 19 countries found that posing a smile, or copying a smiling face, raised reported happiness a little; a subtler method, holding a pen between the teeth, gave less clear results.

The idea that the face can feed back into feelings, called the facial feedback hypothesis, goes back to Charles Darwin and William James. In a famous 1988 experiment, Fritz Strack and colleagues had people hold a pen in their teeth, which forces a smile, or between their lips, which prevents one, and those in the first group rated cartoons as funnier. In 2016, seventeen laboratories repeated that experiment exactly and found no effect. A 2019 review of 138 studies concluded that the effect is real but small and varies from study to study. The 2022 Many Smiles Collaboration, led by Nicholas Coles and designed jointly by supporters and sceptics of the idea, found that deliberate smiling could both strengthen and start feelings of happiness, while the pen method remained inconclusive.

Ikigai DailyRead card
WonderScience

Your gut and brain communicate through nerves, hormones, immune signals and microbes, which is why stress and digestion can affect each other.

Scientists call this link the gut–brain axis. The gut has its own network of about 500 million nerve cells, the enteric nervous system, sometimes called the “second brain”, which can run digestion largely by itself. It is connected to the brain mainly through the vagus nerve, a long nerve running from the brainstem down to the abdomen, and most of its fibres carry messages upwards, from the gut to the brain. More than 90 per cent of the body's serotonin, a chemical messenger, is found in the gut. Gut bacteria play a part too: in a 2004 Japanese study, mice raised entirely free of germs overreacted to stress. Stress can speed up or slow down the gut, one reason it often worsens irritable bowel syndrome, a common gut disorder. Most research on the microbes' role has been in animals, and human evidence is still limited.

Ikigai DailyRead card
WonderScience

A placebo is a dummy treatment, such as a sugar pill. In pain studies, placebos can reduce the pain people report and also dampen activity in the brain areas that process pain, even though they contain no active drug.

The word placebo is Latin for “I shall please”. One of the first clues that the effect is physical came in 1978, when Jon Levine and colleagues studied patients recovering from wisdom tooth removal. They gave them a placebo and naloxone, a drug that blocks the effect of endorphins, the body's own painkilling chemicals. In patients who had responded to the placebo, naloxone increased the pain, which suggested that the placebo relief came from endorphins. In 2004 Tor Wager and colleagues used brain scans to show that a placebo painkiller reduced activity in pain-processing regions during a painful stimulus. Expectation works the other way too: in the nocebo effect, from the Latin for “I shall harm”, expecting harm makes symptoms worse. None of this means the pain was imaginary, or that placebos can replace effective treatment.

Ikigai DailyRead card
WonderScience

Memory does not work like a recording. Each time we recall an event, the brain rebuilds it from stored fragments, filling gaps with what we know and what we have heard since, so a memory can change without our noticing.

Psychologists call this reconstructive memory. In his 1932 book Remembering, the British psychologist Frederic Bartlett described asking people to retell “The War of the Ghosts”, a Native American folk tale unfamiliar to them; each retelling drifted towards what felt familiar in their own culture. In 1974 Elizabeth Loftus and John Palmer showed people films of car accidents and asked how fast the cars were going when they “hit” or “smashed” into each other. Those asked with “smashed” gave higher speeds, and a week later were more likely to remember broken glass that was never there. This is known as the misinformation effect. It matters in court: according to the Innocence Project, mistaken eyewitness identification played a part in most US convictions later overturned by DNA evidence.

Ikigai DailyRead card
WonderScience

Predictive processing, an influential theory in neuroscience, says the brain does not simply wait for information from the senses. It keeps guessing what is out there and uses the incoming signals mainly to check and correct those guesses.

The idea goes back to the German physicist Hermann von Helmholtz, who argued in the 1860s that seeing involves “unconscious inference”: the brain fills in what the eyes cannot fully tell it. In 1999 the researchers Rajesh Rao and Dana Ballard turned this into a computer model of vision. Higher brain areas send predictions down, and lower areas send back only the difference between prediction and input, called the prediction error. The philosopher Andy Clark and the neuroscientist Karl Friston later helped develop it into a broad theory of the mind. A well-known illustration is the hollow-mask illusion: the inside of a mask still looks like a face bulging outwards, because the brain's expectation of a normal face outweighs the evidence. The theory is widely used but still debated, and critics ask how some of its claims could be tested.

Ikigai DailyRead card
Next card in the archiveWorking memory, the mental space where you hold information for a few seconds while using it, is smaller than the famous “seven items” suggests. When people cannot group or rehearse items, most experiments find room for only about three or four at once.Read next →