Acoustic Stimuli Research Articles

The Effect of Rheumatoid Arthritis on Middle and Inner Ear Functions.

To investigate the middle and inner ear functions, and efferent auditory systems in patients with rheumatoid arthritis (RA). Thirty-five RA patients and 40 control subjects participated in the study. Pure-tone audiometry, high-frequency audiometry, multifrequency tympanometry, transient evoked otoacoustic emissions, and contralateral suppression tests were administered to all participants. Pure-tone hearing thresholds of RA patients were significantly higher at all frequencies except for 2000 Hz, 14,000 Hz, and 16,000 Hz in the right ear and 16,000 Hz in the left ear (p<0.05). Resonance frequency values of RA patients were statistically significantly lower than those of the control group (p<0.001). Emission amplitudes obtained with contralateral acoustic stimulation were significantly lower at 1400 Hz frequency in both groups than without contralateral acoustic stimulation (p<0.05). While contralateral suppression was observed at all frequencies in the control group, no suppression occurred at 2800 Hz and 4000 Hz in RA patients. The results obtained in this study demonstrated the presence of hearing dysfunction in patients with RA. When a patient is diagnosed with RA, an audiological evaluation should be made, and the patient should be informed about the possibility of audiological involvement.

Acoustic Stimulation to Improve Slow-Wave Sleep in Alzheimer's Disease: A Multiple Night At-Home Intervention

ObjectivesTo investigate the efficacy of closed-loop acoustic stimulation (CLAS) during slow-wave sleep (SWS) to enhance slow-wave activity (SWA) and SWS in patients with Alzheimer's disease (AD) across multiple nights and to explore associations between stimulation, participant characteristics, and individuals’ SWS response. DesignA 2-week, open-label at-home intervention study utilizing the DREEM2 headband to record sleep data and administer CLAS during SWS. Setting and participantsFifteen older patients with AD (6 women, mean age: 76.27 [SD = 6.06], mean MOCA-score: 16.07 [SD = 6.94]), living at home with their partner, completed the trial. InterventionPatients first wore the device for two baseline nights, followed by 14 nights during which the device was programmed to randomly either deliver acoustic stimulations of 50 ms pink noise (± 40 dB) targeted to the slow-wave up-phase during SWS or only mark the wave (sham). ResultsOn a group level, stimulation significantly enhanced SWA and SWS with consistent SWS enhancement throughout the intervention. However, substantial variability existed in individual responses to stimulation. Individuals received more stimulations on nights with increased SWS compared to baseline than on nights with no change or a decrease. In individuals, having lower baseline SWS correlated with receiving fewer stimulations on average during the intervention. ConclusionCLAS during SWS is a promising nonpharmacological method to enhance SWA and SWS in AD. However, patients with lower baseline SWS received fewer stimulations during the intervention, possibly resulting in less SWS enhancement. Individual variability in response to stimulation underscores the need to address personalized stimulation parameters in future research and therapy development.

Human Olivocochlear Effects: A Statistical Detection Approach Applied to the Cochlear Microphonic Evoked by Swept Tones.

The human medial olivocochlear (MOC) reflex was assessed by observing the effects of contralateral acoustic stimulation (CAS) on the cochlear microphonic (CM) across a range of probe frequencies. A frequency-swept probe tone (125-4757Hz, 90dB SPL) was presented in two directions (up sweep and down sweep) to normal-hearing young adults. This study assessed MOC effects on the CM in individual participants using a statistical approach that calculated minimum detectable changes in magnitude and phase based on CM signal-to-noise ratio (SNR). Significant increases in CM magnitude, typically 1-2dB in size, were observed for most participants from 354 to 1414Hz, where the size and consistency of these effects depended on participant, probe frequency, sweep direction, and SNR. CAS-related phase lags were also observed, consistent with CM-based MOC studies in laboratory animals. Observed effects on CM magnitude and phase were in the opposite directions of reported effects on otoacoustic emissions (OAEs). OAEs are sensitive to changes in the motility of outer hair cells located near the peak region of the traveling wave, while the effects of CAS on the CM likely originate from MOC-related changes in the conductance of outer hair cells located in the basal tail of the traveling wave. Thus, MOC effects on the CM are complementary to those observed for OAEs.

Resonance sonomanometry for noninvasive, continuous monitoring of blood pressure.

Cardiovascular disease is the leading cause of death worldwide. Existing methods for continuous, noninvasive blood pressure (BP) monitoring suffer from poor accuracy, uncomfortable form factors, or a need for frequent calibration, limiting their adoption. We introduce a new framework for continuous BP measurement that is noninvasive and calibration-free called resonance sonomanometry. The method uses ultrasound imaging to measure both the arterial dimensions and artery wall resonances that are induced by acoustic stimulation, which offers a direct measure of BP by a fully determined physical model. The approach and model are validated in vitro using arterial mock-ups and then in multiple arteries in human subjects. This approach offers the promise of robust continuous BP measurements, providing significant benefits for early diagnosis and treatment of cardiovascular disease.

Fast Inhibition Slows and Desynchronizes Mouse Auditory Efferent Neuron Activity.

The encoding of acoustic stimuli requires precise neuron timing. Auditory neurons in the cochlear nucleus (CN) and brainstem arewell suited for accurate analysis of fast acoustic signals, given their physiological specializations of fast membrane time constants, fast axonal conduction, and reliable synaptic transmission. The medial olivocochlear (MOC) neurons that provide efferent inhibition of the cochlea reside in the ventral brainstem and participate in these fast neural circuits. However, their modulation of cochlear function occurs over time scales of a slower nature. This suggests the presence of mechanisms that reduce MOC inhibition of cochlear function. To determine how monaural excitatory and inhibitory synaptic inputs integrate to affect the timing of MOC neuron activity, we developed a novel in vitro slice preparation ("wedge-slice"). The wedge-slice maintains the ascending auditory nerve root, the entire CN and projecting axons, while preserving the ability to perform visually guided patch-clamp electrophysiology recordings from genetically identified MOC neurons. The "in vivo-like" timing of the wedge-slice demonstrates that the inhibitory pathway accelerates relative to the excitatory pathway when the ascending circuit is intact, and the CN portion of the inhibitory circuit is precise enough to compensate for reduced precision in later synapses. When combined with machine learning PSC analysis and computational modeling, we demonstrate a larger suppression of MOC neuron activity when the inhibition occurs with in vivo-like timing. This delay of MOC activity may ensure that the MOC system is only engaged by sustained background sounds, preventing a maladaptive hypersuppression of cochlear activity.

Electrophysiological auditory measures to identify potential cortical markers of tinnitus

Tinnitus, or the perception of a sound in the absence of an external acoustic stimulus, is a common condition that cannot yet be objectively diagnosed. Current diagnostic tests of tinnitus consist of case history and behavioral measures that rely on subjective responses. This study examined electrophysiological measures, specifically the auditory late response (ALR), mismatch negativity (MMN), and P300 as potential neural biomarkers of tinnitus in both a tinnitus and non-tinnitus control group while utilizing the pitch-matched tinnitus frequencies as the test stimuli. Results of this study found differences in MMN amplitudes and area under the curve, and in P300 topographic maps between tinnitus and control subjects. The differences in MMN responses across groups suggest that dysfunctional processing of acoustic stimuli located near the tinnitus frequency in individuals with tinnitus manifests as soon as 200 ms after initial onset of the stimulus. In addition, results from a global field power analysis and differences in spatial distributions on topographical maps indicate that deficits persist through higher levels of cortical processing. A secondary goal of this study was to determine if electrophysiological measures correlated with reported tinnitus severity on questionnaires. This analysis indicated that P2 latency was a significant predictor of Tinnitus Reaction Questionnaire, Tinnitus Handicap Inventory, and percent of the time participant’s tinnitus was considered bothersome, suggesting that this measure could potentially be used to assess the efficacy of treatment programs for tinnitus.

Possible mechanisms to improve sleep spindles via closed loop stimulation during slow wave sleep: A computational study.

Sleep spindles are one of the prominent EEG oscillatory rhythms of non-rapid eye movement sleep. In the memory consolidation, these oscillations have an important role in the processes of long-term potentiation and synaptic plasticity. Moreover, the activity (spindle density and/or sigma power) of spindles has a linear association with learning performance in different paradigms. According to the experimental observations, the sleep spindle activity can be improved by closed loop acoustic stimulations (CLAS) which eventually improve memory performance. To examine the effects of CLAS on spindles, we propose a biophysical thalamocortical model for slow oscillations (SOs) and sleep spindles. In addition, closed loop stimulation protocols are applied on a thalamic network. Our model results show that the power of spindles is increased when stimulation cues are applied at the commencing of an SO Down-to-Up-state transition, but that activity gradually decreases when cues are applied with an increased time delay from this SO phase. Conversely, stimulation is not effective when cues are applied during the transition of an Up-to-Down-state. Furthermore, our model suggests that a strong inhibitory input from the reticular (RE) layer to the thalamocortical (TC) layer in the thalamic network shifts leads to an emergence of spindle activity at the Up-to-Down-state transition (rather than at Down-to-Up-state transition), and the spindle frequency is also reduced (8-11 Hz) by thalamic inhibition.

On Transducing Properties of Kombucha-Proteinoid Complexes.

We investigate the information processing capacities of kombucha-proteinoid proto-brains, focusing on the transducing properties through accommodation spiking, tonic bursting spiking, and optical and acoustic stimulation. We explore self-organization, adaptability, and emergent phenomena in this unconventional proto-architecture. By constructing kombucha-proteinoid networks exposed to diverse audio stimuli, we analyze nonlinear dynamics using time series analysis. Assessing information representation in the presence of extreme noise, we examine the system's resilience. Our results illustrate intricate pathways resulting from the interplay between the synthetic biological substrate and bio-inspired stimulation. The kombucha-proteinoid proto-brains consistently map complex stimuli to distinct activation levels, showcasing their adaptability and potential for information processing without the need for external shaping circuits.

Electrocochleography-Based Tonotopic Map: II. Frequency-to-Place Mismatch Impacts Speech-Perception Outcomes in Cochlear Implant Recipients.

Modern cochlear implants (CIs) use varying-length electrode arrays inserted at varying insertion angles within variably sized cochleae. Thus, there exists an opportunity to enhance CI performance, particularly in postlinguistic adults, by optimizing the frequency-to-place allocation for electrical stimulation, thereby minimizing the need for central adaptation and plasticity. There has been interest in applying Greenwood or Stakhovskaya et al. function (describing the tonotopic map) to postoperative imaging of electrodes to improve frequency allocation and place coding. Acoustically-evoked electrocochleography (ECochG) allows for electrophysiologic best-frequency (BF) determination of CI electrodes and the potential for creating a personalized frequency allocation function. The objective of this study was to investigate the correlation between early speech-perception performance and frequency-to-place mismatch. This retrospective study included 50 patients who received a slim perimodiolar electrode array. Following electrode insertion, five acoustic pure-tone stimuli ranging from 0.25 to 2 kHz were presented, and electrophysiological measurements were collected across all 22 electrode contacts. Cochlear microphonic tuning curves were subsequently generated for each stimulus frequency to ascertain the BF electrode or the location corresponding to the maximum response amplitude. Subsequently, we calculated the difference between the stimulus frequency and the patient's CI map's actual frequency allocation at each BF electrode, reflecting the frequency-to-place mismatch. BF electrocochleography-total response (BF-ECochG-TR), a measure of cochlear health, was also evaluated for each subject to control for the known impact of this measure on performance. Our findings showed a moderate correlation (r = 0.51; 95% confidence interval: 0.23 to 0.76) between the cumulative frequency-to-place mismatch, as determined using the ECochG-derived BF map (utilizing 500, 1000, and 2000 Hz), and 3-month performance on consonant-nucleus-consonant words (N = 38). Larger positive mismatches, shifted basal from the BF map, led to enhanced speech perception. Incorporating BF-ECochG-TR, total mismatch, and their interaction in a multivariate model explained 62% of the variance in consonant-nucleus-consonant word scores at 3 months. BF-ECochG-TR as a standalone predictor tended to overestimate performance for subjects with larger negative total mismatches and underestimated the performance for those with larger positive total mismatches. Neither cochlear diameter, number of cochlear turns, nor apical insertion angle accounted for the variability in total mismatch. Comparison of ECochG-BF derived tonotopic electrode maps to the frequency allocation tables reveals substantial mismatch, explaining 26.0% of the variability in CI performance in quiet. Closer examination of the mismatch shows that basally shifted maps at high frequencies demonstrate superior performance at 3 months compared with those with apically shifted maps (toward Greenwood and Stakhovskaya et al.). The implications of these results suggest that electrophysiological-based frequency reallocation might lead to enhanced speech-perception performance, especially when compared with conventional manufacturer maps or anatomic-based mapping strategies. Future research, exploring the prospective use of ECochG-based mapping techniques for frequency allocation is underway.

The role of the Ventral Nucleus of the Trapezoid Body in the auditory prepulse inhibition of the acoustic startle reflex

Cholinergic signaling is essential to mediate the auditory prepulse inhibition (PPI), an operational measure of sensorimotor gating, that refers to the reduction of the acoustic startle reflex (ASR) when a low-intensity, non-startling acoustic stimulus (the prepulse) is presented just before the onset of the acoustic startle stimulus. The cochlear root neurons (CRNs) are the first cells of the ASR circuit to receive cholinergic inputs from non-olivocochlear neurons of the ventral nucleus of the trapezoid body (VNTB) and subsequently decrease their neuronal activity in response to auditory prepulses. Yet, the contribution of the VNTB-CRNs pathway to the mediation of PPI has not been fully elucidated. In this study, we used the immunotoxin anti-choline acetyltransferase (ChAT)-saporin as well as electrolytic lesions of the medial olivocochlear bundle to selectively eliminate cholinergic VNTB neurons, and then assessed the ASR and PPI paradigms. Retrograde track-tracing experiments were conducted to precisely determine the site of lesioning VNTB neurons projecting to the CRNs. Additionally, the effects of VNTB lesions and the integrity of the auditory pathway were evaluated via auditory brain responses tests, ChAT- and FOS-immunohistochemistry. Consequently, we established three experimental groups: 1) intact control rats (non-lesioned), 2) rats with bilateral lesions of the olivocochlear bundle (OCB-lesioned), and 3) rats with bilateral immunolesions affecting both the olivocochlear bundle and the VNTB (OCB/VNTB-lesioned). All experimental groups underwent ASR and PPI tests at several interstimulus intervals before the lesion and 7, 14, and 21 days after it. Our results show that the ASR amplitude remained unaffected both before and after the lesion across all experimental groups, suggesting that the VNTB does not contribute to the ASR. The%PPI increased across the time points of evaluation in the control and OCB-lesioned groups but not in the OCB/VNTB-lesioned group. At the ISI of 50 ms, the OCB-lesioned group exhibited a significant increase in%PPI (p < 0.01), which did not occur in the OCB/VNTB-lesioned group. Therefore, the ablation of cholinergic non-olivocochlear neurons in the OCB/VNTB-lesioned group suggests that these neurons contribute to the mediation of auditory PPI at the 50 ms ISI through their cholinergic projections to CRNs. Our study strongly reinforces the notion that auditory PPI encompasses a complex mechanism of top-down cholinergic modulation, effectively attenuating the ASR across different interstimulus intervals within multiple pathways.

Experimental recreationist noise alters behavior and space use of wildlife

Providing outdoor recreational opportunities to people and protecting wildlife are dual goals of many land managers. However, recreation is associated with negative effects on wildlife, ranging from increased stress hormones1,2 to shifts in habitat use3,4,5 to lowered reproductive success.6,7 Noise from recreational activities can be far reaching and have similar negative effects on wildlife, yet the impacts of these auditory encounters are less studied and are often unobservable. We designed a field-based experiment to both isolate and quantify the effects of recreation noise on several mammal species and test the effects of different recreation types and group sizes. Animals entering our sampling arrays triggered cameras to record video and broadcast recreation noise from speakers ∼20m away. Our design allowed us to observe and classify behaviors of wildlife as they were exposed to acoustic stimuli. We found wildlife were 3.1-4.7 times more likely to flee and were vigilant for 2.2-3.0 times longer upon hearing recreation noise compared with controls (natural sounds and no noise). Wildlife abundance at our sampling arrays was 1.5 times lower the week following recreation noise deployments. Noise from larger groups of vocal hikers and mountain bikers caused the highest probability of fleeing (6-8 times more likely to flee). Elk were the most sensitive species to recreation noise, and large carnivores were the least sensitive. Our findings indicate that recreation noise alone caused anti-predator responses in wildlife, and as outdoor recreation continues to increase in popularity and geographic extent,8,9 noise from recreation may result in degraded or indirect wildlife habitat loss.

The Effect of an Emotionalizing Sound Design on the Driver’s Choice of Headway in a Driving Simulator

This study investigates the impact of emotionalizing sound design on driving behaviour, focusing on the effect of an acoustic stimulus that varies from positive to negative/threatening based on the vehicle’s time headway (THW). Our primary goal was to explore how this sound influences driving durations within specific THW ranges and the mean THW itself. The experiment utilized a control group and a within-participant setting across simulated driving scenarios. The statistical analysis showed mixed results. While participants in the control group setup did not demonstrate significant reductions in the durations of driving in lower THW ranges, a modest but significant increase in mean THW was observed when the emotionalizing sound was active. However, within-participant comparisons showed both a significant decrease in the duration of driving at lower THWs and an increase in mean THW when the negative stimulus was active, suggesting the stimulus’ effectiveness in promoting safer driving habits. These findings highlight the potential of emotionalizing sound design to influence driver behaviour towards maintaining safer distances, although the impact appears to diminish at higher THW ranges. Future research should further investigate the characteristics of sounds that effectively modify driving behaviour, aiming for broader applications in traffic safety.

Frequency-Specific Responses: The Impact of an Acoustic Stimulus on Behavioral and Physiological Indices in Large Yellow Croaker

Frequency-Specific Responses: The Impact of an Acoustic Stimulus on Behavioral and Physiological Indices in Large Yellow Croaker

A zebrafish-based acoustic motor response (AMR) assay to evaluate chemical-induced developmental neurotoxicity

Behavioral assays using early-developing zebrafish (Danio rerio) offer a valuable supplement to the in vitro battery adopted as new approach methodologies (NAMs) for assessing risk of chemical-induced developmental neurotoxicity. However, the behavioral assays primarily adopted rely on visual stimulation to elicit behavioral responses, known as visual motor response (VMR) assays. Ocular deficits resulting from chemical exposures can, therefore, confound the behavioral responses, independent of effects on the nervous system. This highlights the need for complementary assays employing alternative forms of sensory stimulation. In this study, we investigated the efficacy of acoustic stimuli as triggers of behavioral responses in larval zebrafish, determined the most appropriate data acquisition mode, and evaluated the suitability of an acoustic motor response (AMR) assay as means to assess alterations in brain activity and risk of chemical-induced developmental neurotoxicity. We quantified the motor responses of 120 h post-fertilization (hpf) larvae to acoustic stimuli with varying patterns and frequencies, and determined the optimal time intervals for data acquisition. Following this, we examined changes in acoustic and visual motor responses resulting from exposures to pharmacological agents known to impact brain activity (pentylenetetrazole (PTZ) and tricaine-s (MS-222)). Additionally, we examined the AMR and VMR of larvae following exposure to two environmental contaminants associated with developmental neurotoxicity: arsenic (As) and cadmium (Cd). Our findings indicate that exposure to a 100 Hz sound frequency in 100 ms pulses elicits the strongest behavioral response among the acoustic stimuli tested and data acquisition in 2 s time intervals is suitable for response assessment. Exposure to PTZ exaggerated and depressed both AMR and VMR in a concentration-dependent manner, while exposure to MS-222 only depressed them. Similarly, exposure to As and Cd induced respective hyper- and hypo-activation of both motor responses. This study highlights the efficiency of the proposed zebrafish-based AMR assay in demonstrating risk of chemical-induced developmental neurotoxicity and its suitability as a complement to the widely adopted VMR assay.

A randomized controlled trial of alpha phase-locked auditory stimulation to treat symptoms of sleep onset insomnia

Sleep onset insomnia is a pervasive problem that contributes significantly to the poor health outcomes associated with insufficient sleep. Auditory stimuli phase-locked to slow-wave sleep oscillations have been shown to augment deep sleep, but it is unknown whether a similar approach can be used to accelerate sleep onset. The present randomized controlled crossover trial enrolled adults with objectively verified sleep onset latencies (SOLs) greater than 30 min to test the effect of auditory stimuli delivered at specific phases of participants’ alpha oscillations prior to sleep onset. During the intervention week, participants wore an electroencephalogram (EEG)-enabled headband that delivered acoustic pulses timed to arrive anti-phase with alpha for 30 min (Stimulation). During the Sham week, the headband silently recorded EEG. The primary outcome was SOL determined by blinded scoring of EEG records. For the 21 subjects included in the analyses, stimulation had a significant effect on SOL according to a linear mixed effects model (p = 0.0019), and weekly average SOL decreased by 10.5 ± 15.9 min (29.3 ± 44.4%). These data suggest that phase-locked acoustic stimulation can be a viable alternative to pharmaceuticals to accelerate sleep onset in individuals with prolonged sleep onset latencies. Trial Registration: This trial was first registered on clinicaltrials.gov on 24/02/2023 under the name Sounds Locked to ElectroEncephalogram Phase For the Acceleration of Sleep Onset Time (SLEEPFAST), and assigned registry number NCT05743114.

Effects of developmental exposure to arsenic species on behavioral stress responses in larval zebrafish and implications for stress-related disorders.

Arsenic (As) is globally detected in drinking water and food products at levels repeatedly surpassing regulatory thresholds. Several neurological and mental health risks linked to arsenic exposure are proposed; however, the nature of these effects and their association with the chemical forms of arsenic are not fully understood. Gaining a clear understanding of the etiologies and characteristics of these effects is crucial, particularly in association with developmental exposures where the nervous system is most vulnerable. In this study, we investigated the effects of early developmental exposure (6- to 120-h postfertilization [hpf]) of larval zebrafish to environmentally relevant concentrations of arsenic species-trivalent/pentavalent, inorganic/organic forms-on developmental, behavioral, and molecular endpoints to determine their effect on stress response and their potential association with stress-related disorders. At 120hpf, the developing larvae were assessed for a battery of endpoints including survival, developmental malformities, background activity, and behavioral responses to acute visual and acoustic stimuli. Pooled larval samples were analyzed for alterations in the transcript levels of genes associated with developmental neurotoxicity and stress-related disorders. Developmental exposures at target concentrations did not significantly alter survival, overall development, or background activity, and had minor effects on developmental morphology. Sodium arsenate and monomethylarsonic acid exaggerated the behavioral responses of larval zebrafish, whereas sodium arsenite depressed them. Sodium arsenate induced significant effects on molecular biomarkers. This study highlights the effects of developmental exposure to arsenicals on the behavioral stress response, the role chemical formulation plays in exerting toxicological effects, and the possible association with stress-related disorders.

Individualized Closed-Loop Acoustic Stimulation Suggests an Alpha Phase Dependence of Sound Evoked and Induced Brain Activity Measured with EEG Recordings.

Following repetitive visual stimulation, post hoc phase analysis finds that visually evoked response magnitudes vary with the cortical alpha oscillation phase that temporally coincides with sensory stimulus. This approach has not successfully revealed an alpha phase dependence for auditory evoked or induced responses. Here, we test the feasibility of tracking alpha with scalp electroencephalogram (EEG) recordings and play sounds phase-locked to individualized alpha phases in real-time using a novel end-point corrected Hilbert transform (ecHT) algorithm implemented on a research device. Based on prior work, we hypothesize that sound-evoked and induced responses vary with the alpha phase at sound onset and the alpha phase that coincides with the early sound-evoked response potential (ERP) measured with EEG. Thus, we use each subject's individualized alpha frequency (IAF) and individual auditory ERP latency to define target trough and peak alpha phases that allow an early component of the auditory ERP to align to the estimated poststimulus peak and trough phases, respectively. With this closed-loop and individualized approach, we find opposing alpha phase-dependent effects on the auditory ERP and alpha oscillations that follow stimulus onset. Trough and peak phase-locked sounds result in distinct evoked and induced post-stimulus alpha level and frequency modulations. Though additional studies are needed to localize the sources underlying these phase-dependent effects, these results suggest a general principle for alpha phase-dependence of sensory processing that includes the auditory system. Moreover, this study demonstrates the feasibility of using individualized neurophysiological indices to deliver automated, closed-loop, phase-locked auditory stimulation.

Frequency importance functions in simulated bimodal cochlear-implant users with spectral holes.

Frequency importance functions (FIFs) for simulated bimodal hearing were derived using sentence perception scores measured in quiet and noise. Acoustic hearing was simulated using low-pass filtering. Electric hearing was simulated using a six-channel vocoder with three input frequency ranges, resulting in overlap, meet, and gap maps, relative to the acoustic cutoff frequency. Spectral holes present in the speech spectra were created within electric stimulation by setting amplitude(s) of channels to zero. FIFs were significantly different between frequency maps. In quiet, the three FIFs were similar with gradually increasing weights with channels 5 and 6 compared to the first three channels. However, the most and least weighted channels slightly varied depending on the maps. In noise, the patterns of the three FIFs were similar to those in quiet, with steeper increasing weights with channels 5 and 6 compared to the first four channels. Thus, channels 5 and 6 contributed to speech perception the most, while channels 1 and 2 contributed the least, regardless of frequency maps. Results suggest that the contribution of cochlear implant frequency bands for bimodal speech perception depends on the degree of frequency overlap between acoustic and electric stimulation and if noise is absent or present.

The effects of auditory consequences on visuomotor adaptation and motor memory.

Sensorimotor adaptation is a form of motor learning that is essential for maintaining motor performance across the lifespan and is integral to recovery of function after neurological injury. Recent research indicates that experiencing a balance-threatening physical consequence when making a movement error during adaptation can enhance subsequent motor memory. This is perhaps not surprising, as learning to avoid injury is critical for our survival and well-being. Reward and punishment can also differentially modify aspects of motor learning. However, it remains unclear whether other forms of non-physical consequences can impact motor learning. Here we tested the hypothesis that a loud acoustic stimulus linked to a movement error during adaptation could lead to greater generalization and consolidation. Two groups of participants (n = 12 each) adapted to a new, prism-induced visuomotor mapping while performing a precision walking task. One group experienced an unexpected loud acoustic stimulus (85 dB tone) when making foot-placement errors during adaptation. This auditory consequence group adapted faster and showed greater generalization with an interlimb transfer task, but not greater generalization to an obstacle avoidance task. Both groups showed faster relearning (i.e., savings) during the second testing session one week later despite the presence of an interference block of trials following initial adaptation, indicating successful consolidation. However, we did not find significant differences between groups with relearning during session 2. Overall, our results suggest that auditory consequences may serve as a useful method to improve motor learning, though further research is required.

Chronic short sleep duration lengthens reaction time, but the deficit is not associated with motor preparation.

The purpose of this study was to investigate the association between chronic sleep duration and reaction time performance and motor preparation during a simple reaction time task with a startling acoustic stimulus in adults. This cross-sectional study included self-reported short sleepers (n = 25, ≤ 6 hr per night) and adequate sleepers (n = 25, ≥ 7.5 hr per night) who performed a simple reaction time task requiring a targeted ballistic wrist extension in response to either a control-tone (80 dB) or a startling acoustic stimulus (120 dB). Outcome measures included reaction times for each stimulus (overall and for each trial block), lapses, and proportion of startle responses. Chronic short sleepers slept on average 5.7 hr per night in the previous month, which was 2.8 hr per night less than the adequate sleepers. Results revealed an interaction between sleep duration group and stimulus type; the short sleepers had significantly slower control-tone reaction times compared with adequate sleepers, but there was no significant difference in reaction time between groups for the startling acoustic stimulus. Further investigation showed that chronic short sleepers had significantly slower control-tone reaction times after two blocks of trials lasting about 5 min, until the end of the task. Lapses were not significantly different between groups. Chronic short sleep duration was associated with poorer performance; however, these reaction time deficits cannot be attributed to motor preparation, as startling acoustic stimulus reaction times were not different between sleep duration groups. While time-on-task performance decrements were associated with chronic sleep duration, alertness was not. Sleeping less than the recommended sleep duration on a regular basis is associated with poorer cognitive performance, which becomes evident after 5 min.