XNUMX. The concept of tinnitus
tinnitus It is a sound sensation over a certain period of time that is produced in the ear or skull of a person when there is no external sound or electrical stimulation.It is a disturbing sound experience, and there is no objective method to detect it.It is different from the auditory hallucinations in hallucinations. Auditory hallucinations refer to patients who can imagine hearing some meaningful sounds, such as speech and music.
Second, the classification of tinnitus
People divide tinnitus into subjective tinnitus and objective tinnitus according to whether the examiner can hear tinnitus.
1) Subjective tinnitus.The mechanism of subjective tinnitus is not very clear. Depending on the cause of tinnitus, the mechanism is also different, and many mechanisms are still in the inference stage.There are several theories about the mechanism of subjective tinnitus:
① Certain pathogenic causes affect the calcium-activated potassium current by changing the calcium conductivity of the membrane, causing nerve fibers and central neurons at all levels to induce abnormal firing patterns. The spontaneous firing rate of the neural unit is reduced or completely suppressed.
② Impulsive noise, abnormal activities of the perilymph, membrane labyrinth, increased direct current of hair cells, abnormal blood flow in the cochlea, etc., cause the mechanical function of the cochlea to be impaired, which destroys the electrical insulation between hair cells or nerve fiber structures , Causing the spontaneous activity of the nerve structure to be locked, similar to the neural activity evoked by the sound, the auditory center misrecognizes the sound and tinnitus occurs.
③ The outer hair cells of the cochlea can provide the swinging energy required by the basement membrane in the fine adjustment of the cochlea.In a calm state, the location of the basement membrane swing varies with the frequency of the stimulus.This mechanism helps to overcome the inertial movement of the basement membrane caused by the perception of transient sounds at very low intensity.
④ The subconscious and conscious parts of people’s perception of sound are located in the auditory pathway and some non-auditory systems.In particular, the different planes of the limbic system are the basic parts of tinnitus release, and also determine the degree of boredom with tinnitus.When the sound is in the central part of the afferent channel, that is, the subconscious part, the weak signal of the normal activity of the nerve is reinvigorated by a kind of loudness generated by the perception, that is, tinnitus.