Sensornye sistemy

Control of speech fulfilled by cooperation between feedforward control and feedback control. Feedforward control activates program of articulation, whereas feedback control carries acoustic and sensorimotor information about pronounced utterance. Their complementary speech control function described by the DIVA model, which based on adjustment of auditory and proprioceptive signals relatively to program of articulation in nerve centers. The inconsistency between the sensory information received via feedback and the presentation of the acoustic signal in the auditory nucleus causes corrective commands. Auditory feedback is necessary for the correct development of children’s articulatory skills, i.e. forming feedforward control. For this reason, prelingually deafened adults have significant articulation impairments due to immature articulatory skills. In postlingual deafness, the previously forming feedforward control allows pronounce phonemes successfully. However, in people with sensorineural hearing loss, control of phonation and articulation through the auditory feedback deteriorates, which expressed by an increase of voice intensity, changes in the speech spectral characteristics and instability in frequency and amplitude. Similar speech changes are found in speakers with normal hearing in the presence of noise that masks the speaker’s voice (Lombard effect). In noise, voice intensity increase, spectral characteristics of speech shift to the high-frequency region, and increase the amplitude and speed of articulatory movements (hyperarticulation). This speech reorganization is an adaptation of the speaker’s own voice to background noise, which purpose is to unmask the speech and restore auditory feedback control.

Cochlear implantation is a unique development in the field of prosthetics of human sensory systems. Due to the electrical stimulation of the auditory nerve, auditory sensations close to natural occur. Despite significant progress in the engineering design of cochlear implants (CI), the quality of auditory perception when used is significantly limited. CI users experience the greatest difficulties in communication tasks such as understanding speech in noise or in multi-talkers environment. There are many factors, both technical and physiological, to reduce speech intelligibility in CI users. Speech perception in CI users is limited due to low frequency resolution, perceptual distortion of pitch, and compression of dynamic range. Low frequency resolution is the reason a decrease in speech intelligibility and the ability to perceive music. To realize these ability the question about the state of central hearing mechanisms, especially for children with congenital deafness, is crucial Neuroplasticity with ages decreases and the central auditory processing deficiency develops, therefore, it is desirable to carry out cochlear implantation as early as possible after hearing loss identification. Analysis of the auditory perception features in case of the auditory nerve is electrically excited allows not only to propose innovative approaches to improve the auditory abilities of CI users, but also to study auditory processing disorders.

We studied the features of speech signals perception in conditions of vocal competition based on gender (male/female voice) in subjects of different ages and status of auditory and speech functions. Psychophysical measurements were carried out while simulating a “speech cocktail” situation by simultaneously pronounced different words by a male and female. The average fundamental voice frequency for the male speaker was 108 ± 5.92 Hz, for the female speaker – 185 ± 12.03 Hz. Both speakers were standard native speakers of the Russian language. Digital recordings of speech signals were equalized in intensity and compounded so that the total test stimulus was a synchronized mixture of words spoken by a male (M) and female (F) voice. Test speech signals were presented through headphones or through a speaker located in front of the auditor at a distance of 50 cm. The indicators of reaction time and the number of correct recognitions of words of the target speaker (M or F) were compared in 4 groups of subjects of different ages and hearing or speech status: adult subjects with normal hearing and speech (n = 35) and with hearing impaired (n = 26); schoolchildren with normotypical development (n = 26) and with speech disorders (n = 25). The results indicated a falling in the ability to segrerate target speech streams under conditions of vocal competition in the subjects with hearing and speech dysfunctions included in the comparative study. Differences in the perception of male and female voices in subjects with hearing loss and with speech problems were obtained. This result may have a biological and social basis. The data have practical significance for the development of a system of auditory and speech training and modern hearing aid technologies.

According to various authors, 20% of children with sensorineural hearing loss or deafness, anomalies in the structure of the temporal bones are determined according to the results of computed tomography. Cochlear implantation in the presence of cochleovestibular malformations is associated with a number of difficulties. These include the peculiarities of cochleostomy and placing of the electrode inside the cochlea, the risk of damage to the facial nerve due to its abnormal location, intraoperative liquorrhea, which can lead to the development of bacterial meningitis in the postoperative period, as well as the risk of penetration of the electrode into the internal auditory canal. In this research, we present our method of performing cochlear implantation in case of a malformation in the development of the inner ear (common cavity). The method expands the possibilities of cochlear implantation for e auditory perception in patients with this pathology.