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Decoding smells: How scientists figured out the secret to our ability to recognize a trillion odors.
Olfaction, or smell perception, is a special sense that allows us to perceive smells. The sense of smell has many functions, including detecting the deliciousness of food, identifying potential dangers and conveying sexual information. When odor molecules bind to olfactory receptors in the nasal cavity, the signal is transmitted through the olfactory system and sent to the olfactory bulb and further into the processing area of the brain. Scientists have further discovered that the operation of smell is not just a simple recognition process, but is also closely related to our memory and emotions.
The olfactory system is the only sensory system that is connected directly to the forebrain without going through the thalamus.
The History and Scientific Exploration of Smell
Scientific research on smell can be traced back to 1898, when scholar Eleanor Gamble explored the relationship between smell and other sensory stimulation through a doctoral dissertation. As early as the 1st century BC, the Roman philosopher Lucretius proposed that the difference in smell was related to the shape and size of atoms.
Current research was pioneered by Nobel Prize winners Linda B. Buck and Richard Axel, who cloned olfactory receptor proteins to explore the relationship between odor molecules and olfactory receptors. It is estimated that about a thousand genes in mammals are responsible for odor recognition, but humans have only a small number of genes actively involved in odor perception.
Decoding the mechanisms of odor perceptionResearch now shows that different olfactory receptors only respond to specific molecular structures. The process can be likened to a "key and lock" system: if a molecule of a certain chemical can enter the "lock", the nerve cell will be activated. In addition, there are many theories about odor encoding and perception, including shape theory, weak shape theory and vibration theory, but there is currently no theory that can fully explain the odor perception process.
In humans, the ability of the sense of smell has been estimated to be able to recognize over a trillion unique odors.
How smell relates to other senses
The contribution of smell to taste cannot be ignored. The flavor perception in many dining experiences is actually the combined result of taste and smell. During the chewing of food, the odor molecules released enter the nasal cavity through exhalation. This process is called reverse olfaction, which is particularly critical for the perception of food flavor.
The interaction between smell and hearing has also attracted the interest of scientists. Researchers have found that in some animals, the information from these two senses may be integrated to form a perceptual concept called "olfactory sound."
Human sense of smell
According to recent studies, the average person can recognize up to one trillion odors, and some researchers even say that some subjects may be able to distinguish up to a trillion odors. However, the results sparked controversy, with many scientists questioning the logic of the process.
Physiological basis and genetic factors of smell
The sensitivity to odor perception varies significantly among different organisms. For example, dogs' sense of smell is generally 100,000 to 1 million times higher than that of humans, which enables them to track scent trails for days and perform efficient searching tasks. In addition, the acquisition of bad smell is not only affected by physiological structure, but also by genetic factors. Different gene variants can affect an individual's ability to recognize odors.
Experiments show that a mother can recognize her own biological children by smell, but cannot recognize her stepchildren.
Comparison with other species
Animals other than humans have varying degrees of olfactory abilities. Many carnivores and artiodactyls have an acute sense of smell, which is essential for them to find food and recognize each other. Relatively speaking, some birds have a weak sense of smell, but studies have found that under certain circumstances, some birds also use smells to socialize or find food.
Overall, the sense of smell is not only an integral part of our daily lives, but also plays a vital role in the ecosystem. As technology and science advance, we are able to better understand our senses. How will future research change our understanding of smell?
