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      Electro-Haptic Enhancement of Spatial Hearing in Cochlear Implant Users

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      , ,
      Scientific Reports
      Nature Publishing Group UK
      Auditory system, Translational research

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          Abstract

          Cochlear implants (CIs) have enabled hundreds of thousands of profoundly hearing-impaired people to perceive sounds by electrically stimulating the auditory nerve. However, CI users are often very poor at locating sounds, which leads to impaired sound segregation and threat detection. We provided missing spatial hearing cues through haptic stimulation to augment the electrical CI signal. We found that this “electro-haptic” stimulation dramatically improved sound localisation. Furthermore, participants were able to effectively integrate spatial information transmitted through these two senses, performing better with combined audio and haptic stimulation than with either alone. Our haptic signal was presented to the wrists and could readily be delivered by a low-cost wearable device. This approach could provide a non-invasive means of improving outcomes for the vast majority of CI users who have only one implant, without the expense and risk of a second implantation.

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          Most cited references57

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          Derivation of auditory filter shapes from notched-noise data.

          A well established method for estimating the shape of the auditory filter is based on the measurement of the threshold of a sinusoidal signal in a notched-noise masker, as a function of notch width. To measure the asymmetry of the filter, the notch has to be placed both symmetrically and asymmetrically about the signal frequency. In previous work several simplifying assumptions and approximations were made in deriving auditory filter shapes from the data. In this paper we describe modifications to the fitting procedure which allow more accurate derivations. These include: 1) taking into account changes in filter bandwidth with centre frequency when allowing for the effects of off-frequency listening; 2) correcting for the non-flat frequency response of the earphone; 3) correcting for the transmission characteristics of the outer and middle ear; 4) limiting the amount by which the centre frequency of the filter can shift in order to maximise the signal-to-masker ratio. In many cases, these modifications result in only small changes to the derived filter shape. However, at very high and very low centre frequencies and for hearing-impaired subjects the differences can be substantial. It is also shown that filter shapes derived from data where the notch is always placed symmetrically about the signal frequency can be seriously in error when the underlying filter is markedly asymmetric. New formulae are suggested describing the variation of the auditory filter with frequency and level. The implication of the results for the calculation of excitation patterns are discussed and a modified procedure is proposed. The appendix list FORTRAN computer programs for deriving auditory filter shapes from notched-noise data and for calculating excitation patterns. The first program can readily be modified so as to derive auditory filter shapes from data obtained with other types of maskers, such as rippled noise.
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            Effect of temporal envelope smearing on speech reception.

            The effect of smearing the temporal envelope on the speech-reception threshold (SRT) for sentences in noise and on phoneme identification was investigated for normal-hearing listeners. For this purpose, the speech signal was split up into a series of frequency bands (width of 1/4, 1/2, or 1 oct) and the amplitude envelope for each band was low-pass filtered at cutoff frequencies of 0, 1/2, 1, 2, 4, 8, 16, 32, or 64 Hz. Results for 36 subjects show (1) a severe reduction in sentence intelligibility for narrow processing bands at low cutoff frequencies (0-2 Hz); and (2) a marginal contribution of modulation frequencies above 16 Hz to the intelligibility of sentences (provided that lower modulation frequencies are completely present). For cutoff frequencies above 4 Hz, the SRT appears to be independent of the frequency bandwidth upon which envelope filtering takes place. Vowel and consonant identification with nonsense syllables were studied for cutoff frequencies of 0, 2, 4, 8, or 16 Hz in 1/4-oct bands. Results for 24 subjects indicate that consonants are more affected than vowels. Errors in vowel identification mainly consist of reduced recognition of diphthongs and of confusions between long and short vowels. In case of consonant recognition, stops appear to suffer most, with confusion patterns depending on the position in the syllable (initial, medial, or final).
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              Multisensory auditory-somatosensory interactions in early cortical processing revealed by high-density electrical mapping.

              We investigated the time-course and scalp topography of multisensory interactions between simultaneous auditory and somatosensory stimulation in humans. Event-related potentials (ERPs) were recorded from 64 scalp electrodes while subjects were presented with auditory-alone stimulation (1000-Hz tones), somatosensory-alone stimulation (median nerve electrical pulses), and simultaneous auditory-somatosensory (AS) combined stimulation. Interaction effects were assessed by comparing the responses to combined stimulation with the algebraic sum of responses to the constituent auditory and somatosensory stimuli when they were presented alone. Spatiotemporal analysis of ERPs and scalp current density (SCD) topographies revealed AS interaction over the central/postcentral scalp which onset at approximately 50 ms post-stimulus presentation. Both the topography and timing of these interactions are consistent with multisensory integration early in the cortical processing hierarchy, in brain regions traditionally held to be unisensory.
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                Author and article information

                Contributors
                M.D.Fletcher@soton.ac.uk
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                31 January 2020
                31 January 2020
                2020
                : 10
                : 1621
                Affiliations
                ISNI 0000 0004 1936 9297, GRID grid.5491.9, Faculty of Engineering and Physical Sciences, , University of Southampton, ; University Road, Southampton, SO17 1BJ United Kingdom
                Author information
                http://orcid.org/0000-0001-7866-7225
                Article
                58503
                10.1038/s41598-020-58503-8
                6994470
                32005889
                bc571ff8-1f64-400c-899a-a0201a00352f
                © The Author(s) 2020

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 15 August 2019
                : 15 January 2020
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                © The Author(s) 2020

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                auditory system,translational research
                Uncategorized
                auditory system, translational research

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