Can I perceive the whole picture by relying on the sense of smell?In fact, you also have this skill

When we smell the floral fragrance, we may think of the flowers around the mountains during the spring tour or the scene where we play with friends in the flowers; when we stroll at the door of the tavern, we may think of the TA in our hearts and immerse themselves in the past. middle.

In these processes, in addition to memory awakening, there is another abstract concept-perception. Different from the feeling of the brain's reflection of the attributes of objective things, consciousness is the reflection of the overall attributes of objective things on the basis of the sensation.

Flower incense will remind people of the spring color (picture source: pexels)

Let's make a simple example. When you see a person you know, this is vision, but you will think of this person’s name, personality, background, interpersonal relationship, etc., and make a good or hated move to it. perception.

So, how does the brain turn sensation into consciousness?

To what extent we understand the process of turning sensation into consciousness?

Taking the sense of smell and perception as an example, people have clearly understood thousands of smells, but they have not understood how to transform the sense of smell into consciousness, and ultimately affect the behavior, and the deep -level contact information of the olfactory system.

The previous research gave a general picture: first of all, the olfactory neuron passed the information related to the smell to the olfactory ball; then, each olfactory ball and 20-50 monk caps/clustered cells (referred to as MT for short Cells) Pass to the smell cortex (brain) after processing of odor information together.

In other words, the brain is mainly divided into two steps, one is the nose to the sniff, and the other is to smell the brain. At present, the response mode from the nose to the sniff has been well studied, but the response mechanism from the sniffing ball to the brain center has not yet been clarified, especially in terms of neurons level.

On June 19, 2020, the Dmitry Rinberg research team at the Institute of Neuroscience of the Landney Medical Center of New York University published the latest research results at Science magazines. For the first time, they revealed the role of sniffing ball at the neuron level.

Science reports the neural mechanism of a perception of the sniffing ball (picture source: reference 1)

Researchers activate MT cells through optical genetic technology (the range of point stimulation is 120 square meter), and the nerve excitement time can last about 80ms. Because it is artificially produced, this stimulus is also called "synthetic odor".

What is optical genetic?

OPEOGENETICS, also known as optical control gene technology, is a cross biological engineering technology that integrates optical, software control, and gene operation technology in recent years.

It can accurately control or determine the activity of specific living cells in time and space. It has unique high -time and space resolution and cell type specificity. The time accuracy can reach millisecond levels, and the spatial resolution can reach single -cell level.

By training mice to identify the synthetic odor mode: that is, artificially stimulate the sniffing ball, and simulate the sense of olfactory perception at the space scale and time scale (picture source: reference: 1)

In classic neurological experiments, there are roughly two methods to activate a nerve cell: physical and chemical methods.

The physical method is electrical stimulation. For example, the metal electrode is placed next to the nerve cells, changing the extra -cell electric field to activate the cells. Chemical methods refer to small molecules that apply neurotransmitters or drugs that can act on cell receptors.

Traditional methods do not distinguish the cells of all access points, and cannot accurately control certain neurons discharge, but optical genetics can use light to accurately and point -to -point stimulation of cells.

Optimism can achieve precise point stimulation (picture source: Global Science)

The main principle of this is to use genetic operation technology to turn the light gene into a specific type of cells in the nerves and express the expression of special ion channels or protein receptors.

Under the light stimulation of different wavelengths, light -sensitive ion channels will affect the membrane potential on both sides of the cell membrane, and then achieve the purpose of selectively exciting or suppressing cells.

Principle of the role of optical genetic protein — uses the selectivity of ionic channels to ions to regulate the excitement of cells (picture source: Author portfolio)

Because the smell simulation signal is artificially generated, researchers can manipulate the time and order of the transmission of related neuros signals, and determine which changes are most important to accurately identify the "synthetic odor" ability.

How to transform the sense of smell into consciousness?

In order to explore how the sense of smell was transformed into consciousness, the researchers carried out a series of experimental operations and discovered the laws.

For example, in the relevant experiments conducted by mice, when the mouse conducts 6 analog smell stimulation in an orderly time (this activation mode contains space and time characteristics), the mouse pressing rod will get water as a water as a water as a water as a water as a water as a water as a water as a water as a water as a water as a water as a water as a water as a water. Reward, which is called a target mode activation (simulated a certain goal odor).

When the mice are randomly stimulated by the mouse randomly, the mouse pressing rod will not get water as a reward, which is called non -target mode activation (which simulates another different odor).

Researchers activate mice to identify specific signals and drink water in water through the target mode. In this experiment, identifying the signal represents the sense of smell, and the pressing rod drinks water after smelling a specific taste is conscious.

The artificial stimulation target mode and non -target mode of the mouse sniffing the ball (picture source: reference 1) In order to facilitate everyone to understand, we can set the target mode mentioned above to The stimulating space sequence is regarded as a variable Y.

In order to further distinguish the effects of variable X and variable Y in P respectively on the sense of smell and behavior changes of mice, researchers conducted experiments through controlling variables: First, keep X unchanged, change Y, and observe the order of signal transmission order to the behavior of mice behavior. The influence; second, keep Y constant, change X, and observe the effects of time on mouse behavior.

Through this fierce operation, the researchers found that the perception response of mice depends not only on which cells are activated (spatial characteristics), but also depend on the activation incubation period (time characteristics) of such cells, that is, all odor receptors The relative sensitivity to a given stimulus is different, and the latency of the receptor activation with strong sensitivity is relatively short.

In addition, researchers have also found that earlier -activated cells have a greater impact on behavior response. Moreover, a specific smell will form a memory signal in the brain, so that when it is stimulated again, it will respond accordingly according to the target mode.

Just like smelling osmanthus fragrance in life, you will think of osmanthus cake (this is also a consciousness, not only including fragrance, but also the overall attributes such as shape flavor). The order of cell activation is similar to the uniqueness of odor. If you don't smell the aroma of osmanthus, you will not think of osmanthus cake.

The activation period of cells is similar to the concentration of odor or the sensitivity of people to the smell. If the fragrance is not heavy or the person is not sensitive to the aroma of osmanthus, it will naturally not associate. And under the conditions of the same concentration and fragrance, the more sensitive to the smell will have a greater impact on him.

In general, this work affects the artificial smell produced by optical genetic technology to mice, and determines the minimum quantity and type of receptor required to identify specific odors. This helps people understand how the brain uses the sense of smell. Information (feeling) generates perception (regulatory behavior).

Through a series of experimental studies, people finally understood how it felt transformed into consciousness. Do you say this is important? This is of course important.

If you feel the specific grasp of specific, then consciousness is the overall control, and the path that feels perception can be scientific or philosophy. If you look at the next chat, you can not from the perspective of science. Explain what "seeing mountains is a mountain, seeing the mountains is not a mountain"!

Produced: Popular Science China

Author: Lin Feng (Anyang Institute of Technology)

Producer: China Science Popularization Expo

Edit: Wang Tingting

references:

1. Chong et al. (2020). Manipulating Synthetic Optogenetic Odors Reveals the Coding Logic of Olfaction Perception. Science. Doi: https://doi.org/10.1126/science.aba233357777777777777773572335723357233572335723357233572335723357233577777777777777777777777777777777777777777777777777777777777777777777

2. https://www.technologynetworks.com/neuroscience/news/senthetic-smlls-help-reve-the-brain-eDOR-3363334

3. https://nyulangone.org/news/scientist-design-how-rina- senses-smell

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