Category Archives: neuroscience

Tongues ‘taste’ water by sensing sour

All we know about water is that water is an odorless, tasteless, slightly compressible liquid when it’s pure. However, when we drink water, we can know that it’s water. It might be unsurprising to notice that we’re drinking something liquid. But how do we know that it’s water, not syrup? Then, does it mean that water has a taste? – actually not. According to the new study, we can recognize the water not by tasting the water itself, but by sensing acid which is produced when we drink water.

All mammals need water to sustain their life. When we drink water, we have to drink the water through our mouth.According to Yuki Oka who studies the brain at the California Institute of Technology in Pasadena, our tongue has evolved to detect some necessary materials for survival like salt and sugar. This, in other words, means that the sense of detecting water would have evolved.

It is already found that a brain area called the hypothalamus controls thirstiness of mammals. But a brain cannot decide the taste of something alone because, in order to taste something, the brain should cooperate with a mouth and receive a signal from it to know what the person’s eating or drinking. Oka says, “There has to be a sensor that senses water, so we choose the right fluid.” If we cannot distinguish the water from others, we might make a fatal decision, such as drinking poison instead of water.

To prove the water sensor, Oka and his group used mice. They dripped different flavors of liquid onto mice’s tongues. They observed a signal from the nerve cells attached to the taste buds when they were drinking, and mice showed a great nerve response to all tastes. However, the main point is that they reacted to water similarly. Somehow, the scientists discovered that taste buds are able to detect water.

Our mouth is filled with a lot of saliva— a mixture of enzymes and other molecules. Also, the mouth includes bicarbonate ions (HCO3-), which make saliva more basic. The pure water has lower pH than basic saliva. When we pour the water into the mouth, it washes out the basic saliva and enzymes in our mouth instantly starts to replace the ions. It combines carbon dioxide and water to produce bicarbonate. As a side effect, it also produces protons. The bicarbonate is basic, but the protons are acid. Then, the receptors on our tongue detect acid that we usually call ‘sour flavor’ and sends a signal to the brain.

To confirm this, Oka and his group used a technique called optogenetics. In this method, scientists insert light-sensitive molecules, which trigger an electrical impulse when shone with light, inside cells. With this principle, Oka’s team added a light-sensitive molecule to the sour-sensing taste bud cells of mice. As they shone the light to their tongues, they started to lick the light as if they lick the water. By stimulating acid sensor, they misunderstood it as water.

To the other group of mice, Oka’s team removed the sour-sensing molecule by blocking the genetic instructions that make this molecule. As a result, they weren’t able to know whether what they’re drinking is water or not. They even drank thin oil instead. Oka and his group published their results on May 29 in the journal Nature Neuroscience.

Scott Sternson, who studies brain’s mechanism for controlling animal behavior at a Howard Hughes Medical Institute research center in Ashburn, VA, says it’s crucial to learn how we sense simple but vital things, such as water. “It’s important for the basic understanding of how our bodies work,” he says.

Some people might think it’s a weird concept that the water has a sour ‘taste’. Flavor is a complex interaction between taste and smell. So, detecting water is quite different with tasting. Water may still taste like nothing, but to our tongues, it’s definitely something.



What is “Phantom Pain?”

Phantom pain sensation refers to a person’s feeling related to limbs or organs that are physically not a part of their body. For example, let’s say that a part of a person’s body, such as an arm, was amputated because of an accident. If the person has a phantom pain sensation, then he would feel pain in the position where his arm supposed to exist, even though he doesn’t have an arm (this particular phantom pain related to the limbs are called phantom limb pain).

Then why do these kinds of phenomenon occur? According to the scientists, when a part of a body is amputated, then the region of the brain that was needed for the control of that part of the body is no longer needed, and the neuronal system in the part of the brain falls into disarray. To fill the empty spots in the brain, those parts of the brain take over the tasks of the neighboring neurons and become rearranged to do different things. However, when the brain tries to adapt to the new situation, in some cases this process goes wrong, which eventually causes the phantom pain.

As you can see, there are no apparent causes of the phantom pain discovered by scientists because there might be other reasons other than the cerebral shifts such as inherited nerve damages. However, using fMRI, a method to distinguish the active parts of the brain while it’s working, scientists have discovered that degree of the shifts related to the functions in our brain caused by amputation (and many other factors) is directly proportional to the intensity of pain the patient receives through the phantom pain. Also, researchers found out that a person with a functional artificial limb has felt less phantom limb pain than the patients that do not have it.

Even though it might take some time, a cure for phantom pain keeps on developing as the researches related to phantom pain proceed. I hope that later, the patients would not suffer from their phantom pain, or, in my own words, “false pain.”



12 July, 2017 – Episode 627 – This Week in Science Podcast (TWIS)

10% of Brain??

‘So how much percentage of brain did Einstein took advantage of?’


This is a question we ask ourselves after being mesmerized by the catchy internet phrase; people use only 10% of their brain.

However, this is an error made by two Harvard psychologists William James and Boris Sidis while they were studying a very high IQ child named Willian Sidis(adulthood IQ between 250-300). They claimed that people only attained a fraction of their mental potential. This statement has been misinterpreted my times resulting in the myth.

In fact, it has been proved that humans use all parts of their brains for different tasks throughout their life.

The human brain is very perplexing. Along with some mundane acts-just some millions-, brain carries out manifestos and comes up with neat solutions to equations. It also analyzes human emotions, experiences as well as the repository of memory and self-awareness.

So basically, this mistake made by some psychologists is so wrong that it is even laughable. What is correct, however, is that at certain moments in anyone’s life, such as when we are simply at rest and thinking, we may be using only 10 percent of our brains.

Although it is ironic, people can use 100% of their brain when they don’t even understand half of this soft tissue.


Why do we SLEEP?

We feel the urge to sleep when waves of tiredness fall upon us that has been accumulated along the day. After a good rest, we can feel the burden of physical and mental fatigue removed from our  body.

Through this, we can emit a question, “Do people sleep to relieve stress?”.

Although this is the significant answer to the question, there are other reasons why sleeping is crucial to our body.

1 Necessary Energy source; Sleep

One way to think about the function of sleep is to compare it to another of our life-sustaining activities: eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow, repair tissues, and function properly.

2 Sleep is crucial for LEARNING

Studying mice, scientists at Johns Hopkins have fortified evidence that a key purpose of sleep is to recalibrate the brain cells responsible for learning and memory so the animals can “solidify” lessons learned and use them when they awaken. Without at least 4~6 hours of sleep, more than 40% of the content one studied are not solid in the recollective systems in one’s brain. For young infants 11~13 hours of sleep is required for this ability to function correctly.

But still, the answer to the question cannot be satisfied with the pre-suggestions, for the question is asking for the fundamental reason why animals started the action, “sleeping”.There are several theories to clarify the reason to this action that existed to all living organisms from birth .

Inactivity Theory

Mimicking the Activies of Our barin

A mathematical model that successfully imitate the brain sequence related to memory consolidation during sleeping was built according to the study published in PLOS Computational Biology.

Recent studies have proposed that certain brain activities during sleeping might play important roles in memory consolidation. However, researches on those neuronal activity was hard to perform. Michael Schellenberger Costa, Arne Weigenand and their colleagues of the University of Lübeck, Germany, have successively mimicked the pattern of the neuronal activities.

There were some studies that modeled the activities of sleeping cortex. However, the activities related to memory consolidation occurs between cortex and the central brain system, thalamus. Distinct from the previous models, this new model have mimicked this thalamocortial coupling, which is related to the memory consolidation during sleeping.

The new model produces the sequence by predicting the activities of lager mass of neurons after looking at the activities of small groups of neurons, which is different from the past models that looks at the activities of individual neurons.

The researchers confirmed that the model was correct by comparing the neuronal activities recorded by electroencephalography (EEG) during the second and first level of N-REM sleeping with the sequence produced by the new model.

This new model, using the new algorithm for brain activity modeling, is relatively simple compared to the previous models and will be useful for the future studies on memory consolidation during sleeping and the diseases related to memory consolidation.