The impact of acoustic stimulation during sleep on memory and sleep architecture: A meta-analysis.

The relationship between sleep and cognition has long been recognized, with slow-wave sleep thought to play a critical role in long-term memory consolidation. Recent research has presented the possibility that non-invasive acoustic stimulation during sleep could enhance memory consolidation. Herein, we report a random-effects model meta-analysis examining the impact of this intervention on memory and sleep architecture in healthy adults. Sixteen studies were identified through a systematic search. We found a medium significant effect of acoustic stimulation on memory task performance (g = 0.68, p = .031) in young adults <35 years of age, but no statistically significant effect in adults >35 years of age (g = -0.83, p = .223). In young adults, there was a large statistically significant effect for declarative memory tasks (g = 0.87, p = .014) but no effect for non-declarative tasks (g = -0.25, p = .357). There were no statistically significant differences in polysomnography-derived sleep architecture values between sham and stimulation conditions in either young or older adults. Based on these results, it appears that acoustic stimulation during sleep may only be an effective intervention for declarative memory consolidation in young adults. However, the small number of studies in this area, their small sample sizes, the short-term nature of most investigations and the high between-studies heterogeneity highlight a need for high-powered and long-term experiments to better elucidate, and subsequently maximise, any potential benefits of this novel approach.

Face and content validity analysis of the Speech, Spatial and Qualities of Hearing Scale for Parents (SSQ-P) when used in a clinical service without interviews or week-long observation periods.

OBJECTIVES: To assess the face and content validity of the Speech, Spatial and Qualities of Hearing Scale for Parents (SSQ-P) when used in a clinical setting without the recommended interviews and observation periods. METHODS: SSQ-P responses completed by 145 parents of children with bilateral cochlear implants (aged between 5 and 16 years old) were analysed. To assess face validity, the proportion of missing/ambiguous and alternative responses was recorded for each of the 23 items. Where additional written comments were included in responses, a thematic-based analysis was used to identify reasons for the missing/ambiguous or alternative responses. Content validity was assessed using item response theory (IRT), with items having information score less than 0.5 and discrimination score less than 2.0 identified as poorly performing items. RESULTS: All items of the SSQ-P exhibited some proportion of missing/ambiguous or alternative responses, with six items having >10% missing/ambiguous or alternative responses. IRT identified thirteen items that performed poorly in terms of information and discrimination. These included four of the six items with the most missing/ambiguous or alternative responses. CONCLUSIONS: SSQ-P items that performed worse tended to describe scenarios that parents perceived as too specific, too vague or hazardous. Without the recommended administration via interviews following three week-long observation periods, parents found these items difficult to complete. The SSQ-P is therefore not recommended for use without the recommended administration method. However, several items performed well in terms of face and content validity, despite independent parent completion without formal observation periods. Thematic analysis suggested that minor re-wording might improve the face validity of items with high content validity but a high proportion of missing/ambiguous or alternative responses. Therefore, the results of the analyses form the basis on which a shortened version of the SSQ-P, more suitable for use in a clinical setting, could be developed in future studies.

Evidence for an Association Between Hearing Impairment and Disrupted Sleep: Scoping Review.

Purpose Hearing impairment (HI) is the most common sensory impairment and may negatively impact sleep through reduced auditory input. Factors associated with HI such as anxiety regarding communication in daily life may also adversely impact an individual's sleep. Here, research on the relationship between HI and sleep disruption was catalogued using scoping review methodology. Method A systematic strategy was employed to search various electronic databases. This review is reported according to the Preferred Reporting Items for Systematic Review and Meta-Analyses Scoping Review Extension. Results Sixteen records met inclusion criteria. Studies have investigated sleep in HI as a primary aim in noise-exposed workers or large surveys in older participants. Experimental and quasi-experimental studies report alterations to sleep architecture of potential neuroplastic origins. Studies reporting sleep as a secondary aim generally report poorer sleep in HI participants. Conclusions This scoping review has catalogued evidence that altered or negatively impacted sleep may be associated with HI. Potential confounding factors, mechanisms, and considerations for future research are discussed. Supplemental Material https://doi.org/10.23641/asha.9968369.

Changes in sound-source localization for children with bilateral severe to profound hearing loss following simultaneous bilateral cochlear implantation.

BACKGROUND: Sound localization is a valuable skill that children can develop to some extent via bilateral cochlear implants (biCIs). However, little is known regarding the change that can be expected in sound-source localization accuracy (SLA) pre- and post-biCI for children with bilateral, severe-to-profound hearing impairment who spent their early years listening via bilateral hearing aids (biHAs). This study therefore aimed to prospectively assess SLA in a group of children before, and at one year after, receiving simultaneous biCIs. METHODS: Ten children aged 5-18 years were tested. SLA was assessed using loudspeakers positioned at -60, -30, 0, +30, and +60 degrees azimuth. Root mean square (RMS) errors and percentage correct scores were calculated. Changes in SLA were analysed via paired t-tests and potential relationships between hearing threshold levels (HTLs) and SLA via correlation analyses. Response distributions via biHAs and biCIs were examined via scatterplots. RESULTS: The mean within-subject changes in SLA were a significant improvement in RMS error of 11.9° (p < 0.05) and in per cent correct by 21.5% (p < 0.05). Scatterplots demonstrated a trend towards better localization of sounds from 0° azimuth via biCIs compared to via biHAs. No significant associations were found between any measures of SLA and HTLs. CONCLUSIONS: The findings of the present study demonstrate that simultaneous biCIs lead to improved sound localization in children with bilateral, severe to profound sensorineural hearing loss who previously used biHAs. SLA via biHAs or biCIs could not be predicted from children's audiograms, and therefore should be measured directly.

Simultaneous suppression of tone burst-evoked otoacoustic emissions: Two and three-tone burst combinations.

Previous investigations have shown that components of a tone burst-evoked otoacoustic emission (TBOAE) evoked by a 1 kHz tone burst (TB1) can be suppressed by the simultaneous presence of a 2 kHz tone burst (TB2) or a pair of tone bursts at 2 and 3 kHz (TB2 and TB3 respectively). No previous study has measured this "simultaneous suppression of TBOAEs" for both TB2 alone and TB2 and TB3 from the same ears, so that the effect of the additional presence of TB3 on suppression caused by TB2 is not known. In simple terms, three outcomes are possible; suppression increases, suppression is reduced or suppression is not affected. Comparison of previously reported simultaneous suppression data suggests TB3 causes a reduction in suppression, though it is not clear if this is a genuine effect or simply reflects methodological and ear differences between studies. This issue has implications for previously proposed mechanisms of simultaneous suppression of TBOAEs and the interpretation of clinical data, and is clarified by the present study. Simultaneous suppression of TBOAEs was measured for TB1 and TB2 as well as TB1, TB2 and TB3 at 50, 60 and 70 dB p.e. SPL from nine normal human ears. Results showed no significant difference between mean suppression obtained for the two and three-tone burst combinations, indicating the reduction of suppression inferred from comparison of previous data is likely a result of methodological and ear differences rather than a genuine effect.

Changes in children's speech discrimination and spatial release from masking between 2 and 4 years after sequential cochlear implantation.

OBJECTIVE: To document changes in speech reception thresholds (SRTs) and spatial release from masking (SRM) for sequentially implanted children at 2 and 4 years after they received their second cochlear implant (CI2). METHODS: Participants were 17 children who consistently used two sequentially implanted and optimally programmed CIs. SRTs were measured monaurally in quiet and binaurally in noise using the adaptive McCormick toy discrimination test. Speech signals were presented from 0° azimuth and noise from 0°, +90° or  -90° azimuth. SRM was calculated from SRTs in noise. Measurements were made at 2 and 4 year post-CI2. RESULTS: There were significant improvements over time in SRTs in quiet, SRTs in noise and SRM. SRTs in quiet improved more for CI2 than for the first implant (CI1). SRTs in noise and SRM improved more when noise was presented closest to CI1 than when closest to CI2. Performance became more symmetrical over time. DISCUSSION: Despite prolonged periods of unilateral auditory deprivation sequentially implanted children exhibited continued improvement in SRT and SRM. These results are valuable in setting expectations for and counselling families of children considering sequential CIs.

Further tests of the local nonlinear interaction-based mechanism for simultaneous suppression of tone burst-evoked otoacoustic emissions.

Tone burst-evoked otoacoustic emission (TBOAE) components measured in response to a 1 kHz tone burst (TB1) are suppressed by the simultaneous presence of an additional tone burst (TB2). This "simultaneous suppression of TBOAEs" has been explained in terms of a mechanism based on local nonlinear interactions between the basilar membrane (BM) travelling waves caused by TB1 and TB2. A test of this local nonlinear interaction (LNI)-based mechanism, as a function of the frequency separation (Δf, expressed in kHz) between TB1 and TB2, has previously been reported by Killan et al. (2012) using a simple mathematical model [Killan et al., Hear. Res. 285, 58-64 (2012)]. The two experiments described in this paper add additional data on the extent to which the LNI-based mechanism can account for simultaneous suppression, by testing two further hypotheses derived from the model predictions. Experiment I tested the hypothesis that TBOAE suppression is directly linked to TBOAE amplitude nonlinearity where ears that exhibit a higher degree of amplitude nonlinearity yield greater suppression than more linear ears, and this relationship varies systematically as a function of Δf. In order to test this hypothesis simultaneous suppression at a range of values of Δf at 60 dB peak-equivalent sound pressure level (p.e. SPL) and TBOAE amplitude nonlinearity from normal human ears was measured. In Experiment II the hypothesis that suppression will also increase progressively as a function of increasing tone burst level was tested by measuring suppression for a range of Δf and tone burst levels at 40, 50, 60 and 70 dB p.e. SPL. The majority of the findings from both experiments provide support for the LNI-based mechanism being primarily responsible for simultaneous suppression. However, some data were inconsistent with this view. Specifically, a breakdown in the relationship between suppression and TBOAE amplitude nonlinearity at Δf = 1 (i.e. when TB2 was reasonably well separated from, and had a higher frequency than TB1) and unexpected level-dependence, most notably at Δf = 1, but also where Δf = -0.5, was observed. Either the LNI model is too simple or an alternative explanation, involving response components generated at basal regions of the basilar membrane, is required to account for these findings.

A mechanism for simultaneous suppression of tone burst-evoked otoacoustic emissions.

Tone burst-evoked otoacoustic emission (TBOAE) components in response to a 1 kHz tone burst are suppressed by the simultaneous presence of tone bursts at higher frequencies. To date, the underlying cause of this "simultaneous suppression" of TBOAEs is unclear. This paper describes a potential mechanism based on local nonlinear interactions between basilar membrane (BM) travelling waves, and tests the extent to which it is able to account for this specific suppression phenomenon. A simple mathematical model based on local nonlinear interactions was developed, and its predictions for a range of tone burst pairs were compared to corresponding TBOAE suppression data recorded from fourteen normally hearing human ears at a level of 60 dB p.e. SPL. Model predictions and mean TBOAE suppression data showed close agreement for all pairs of tone bursts. These results suggest that simultaneous suppression of TBOAEs can be explained solely in terms of the local nonlinear interaction-based mechanism. However, the involvement of other mechanisms, involving components generated at places basal to their characteristic place along the BM, cannot be excluded.

Simultaneous suppression of tone burst-evoked otoacoustic emissions--effect of level and presentation paradigm.

There is conflict in the literature over whether individual frequency components of a transient-evoked otoacoustic emission (TEOAE) are generated within relatively independent "channels" along the basilar membrane (BM), or whether each component may be generated by widespread areas of the BM. Two previous studies on TEOAE suppression are consistent with generation within largely independent channels, but with a degree of interaction between nearby channels. However, both these studies reported significant suppression only at high stimulus levels, at which the "nonlinear" presentation paradigm was used. The present study clarifies the separate influences of stimulus level and presentation paradigm on this type of suppression. TEOAEs were recorded using stimulus tone bursts at 1, 2 and 3 kHz and a complex stimulus consisting of a digital addition of the three tone bursts, over a range of stimulus levels and both "linear" and "nonlinear" presentation paradigms. Responses to the individual tone bursts were combined offline and compared with responses to the complex stimuli. Results clearly demonstrate that TEOAE suppression under these conditions is dependent upon stimulus level, and not upon presentation paradigm. It is further argued that the data support the "local" rather than "widespread" model of TEOAE generation, subject to nonlinear interactions between nearby generation channels.