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> Auditory cells and associated neurons in the course of individual development, advance "imagine" itself sounds, preparing for the time when ears will start to hear really.

As you know, a sound wave hitting the eardrum, and is transmitted through auditory bones of the middle ear (hammer, anvil, and stirrup) to the inner ear, filled with fluid. The vibration of sound through the fluid to reach the organ of Corti and located in it hair cells that are auditory receptors: they convert mechanical signals into electric neural impulse.

Some time ago, researchers noticed a strange phenomenon: in the first days of life, mice in the absence of any sound auditory hair cells from time to time demonstrate the activity by exciting the corresponding neurons and sending signals to different parts of the sound analyzer of the brain. It was also known that simultaneously with the auditory "all" utility special cells, called a cell support, and that is not without its molecules of adenosine triphosphate (ATP), which, in addition, that are used for storing energy, can also operate with transmitters of biochemical signals.

In detail to decipher the mechanism of the self-activity of the auditory receptors tried Bells Dwight (Dwight Bergles) and his colleagues from the Medical Institute at Johns Hopkins University. The mechanism described in the article in Cell, was quite complicated. It all starts with the cells of the support who throws a lot of ATP acting on receptors on these same cells, support – it turns out that they stimulate themselves. Excited ATP-switch receptor calcium ion channels to enter: in other words, the membrane proteins responsible for transport of calcium, begin to carry out it from the external environment into the cell cytoplasm. Increase the level of calcium in the cell makes is other chloride ion channels to open on the way out, and the chlorine ions travel from the cytoplasm to the outside. After them go outside and potassium ions, which stimulate hair cells – from which the signal is transmitted to the neurons.

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That is, all of the mess with ATP and various ions occurs on the cell support, and all this is necessary in order to increase the level of potassium close to the actual receptor cells. Spontaneous activity of hair cells that transmit the "sound" signals to the brain, is observed in rodents during the first two weeks of life, when their ears have not yet heard (middle ear with auditory ossicles filled with fluid and the sound is not perceived).

Why such a "rehearsal"? For the same reason, do we need any training, that is, to prepare for this work, in this case is to prepare for the perception of real sounds. Such spontaneous signals that "imagining" his auditory receptors, strengthen the relationship between the neurons and the corresponding areas of the brain. In particular, cells can learn not to confuse the sounds of different heights: it is known that high and low frequencies are perceived different voloskovye cells, and it is important that the signals were on the correct neurons and have come to the right area of the brain "sound Department".

Although the experiments are performed on animals, like "audiotreasure" mechanism is likely to have in humans. Moreover, the authors suggest that some auditory processing disorder can be associated with insufficiently active a "rehearsal" of the auditory cells during brain development, and with a sudden revival of such signals are already in adulthood – for example, after injury. For example, it is easy to imagine that the obsessive ringing in the ears, or tinnitus, is just due to Autonomous activation of the auditory receptors, so further study of this system has not only observantine, but also practical value.