The survival attractor in the sensory functions: the example of hearing

High noise levels may have an adverse effect on the normal cochlea function and lead to significant hearing loss. Clinically, exposure to high intensity impulse noise produces a wide range of audiometric effects which may result in long term or even irreversible symptoms. Nevertheless, there is sometimes a spontaneous rebound recovery of the auditory function. This phenomenon was previously studied in the vision, another sensory function. It was called the visual survival attractor. In view of the importance that the sensory organs have for the brain, and in particular in its function of recognising and dealing with its environment, it was interesting to know whether this survival attractor concept already described for vision occurs more generally in all the sensory functions. With this in mind we present here the results of a new study, this time on hearing. This study was carried out on guinea pigs subjected to a pulsed acoustic trauma simulating the sound of a gun going off. Auditory function was explored using electrocochleography and two types of investigation were carried out. At first the change in hearing loss was studied in relation to frequencies varying between 2 and 24 kHz by calculating the difference, at each frequency, between the compound action potential thresholds measured before and then 20 mn, 24 h and 7 days after the acoustic trauma. On the other hand, the change in compound action potential amplitude was determined by varying the stimulating sound level from the auditory threshold up to 90 dB. This change was also recorded at the same time intervals as the investigation of hearing loss. In both the analysis of changes to hearing loss and in the investigation of variations in compound action potential, the results of the electrocochleographic investigations after acoustic trauma confirm the presence of a butterfly catastrophe type reaction process, that is positive evidence of a hearing survival attractor.