Stimulus Frequency Research Articles

Contribution of remote Pacinian corpuscles to flutter-range frequency discrimination in humans.

Among the various classes of fast-adapting (FA) tactile afferents found in hairy and glabrous skin, FA2 afferents, associated with Pacinian corpuscles (PC), preferentially signal high-frequency sinusoidal events corresponding with vibration percepts, in contrast to other classes associated with lower frequency flutter percepts. The FA2-PC complex is also uniquely sensitive to distant sources of vibration mechanically transmitted through anatomical structures. In the present study, we used a pulsatile waveform to assess the contribution of FA2 afferents to the perception of flutter-range frequency stimuli (~ 20Hz) in combination with two methods to abolish local FA inputs and force a dependence on FA2 via transmission from adjacent structures. Firstly, we examined frequency discrimination and perception of vibration applied to the hairy skin overlying the ulnar styloid before and during the blockade of intradermal receptors by local anaesthesia. Secondly, we tested frequency discrimination on the digital glabrous skin before and during the blockade of myelinated fibres by ulnar nerve compression. Despite reliance on vibration transmission to activate remote PCs, we found that flutter-range frequency discrimination was unimpeded across both skin types. Comparisons with stimuli applied to the contralateral side also indicated that perceived frequency was unaffected. This confirms that flutter-range frequency perception can be encoded by the FA2-PC system. Our results demonstrate that input from receptors specialised for low-frequency signalling is not mandatory for flutter-range frequency perception. This explains how the constancy of frequency perception might be achieved across different skin regions, irrespective of the afferent type activated for transmitting these signals.

A subjective and objective fusion visual fatigue assessment system for different hardware and software parameters in SSVEP-based BCI applications.

With the development of brain-computer interface industry, large amounts of related applications have entered people's vision. BCI applications based on steady-state visual evoked potentials (SSVEP) are widely used because they do not require pre-training and have high information transmission rates. However, in the actual use of SSVEP stimulus paradigm, the subjects will produce visual fatigue with the use, and fatigue will affect the transmission efficiency. In this experiment, an experimental environment consisting of two paradigm stimulus frequencies (7.5Hz, 15Hz), three resolutions (800 × 600, 1280 × 720, 1920 × 1080) and three refresh rates (120Hz, 240Hz, 360Hz) is set up. The Likert scale is used to collect subjective fatigue and preference scores, and the EEG acquisition system and eye tracker are used to collect objective data. Using the proposed information entropy-CRITIC algorithm to combine subjective and objective indicators, a fatigue assessment system (display screen fitness-DSF) is innovated to score different experimental environments. The higher the DSF score, the better the visual experience. The results show that when using the 7.5Hz SSVEP paradigm, the combination of 360Hz and 1920 × 1080 can bring the best visual experience. When using the 15Hz SSVEP paradigm, the combination of 240Hz and 1280 × 720 is the best. DSF provides powerful help for hardware and software selection guidance and vision protection when using SSVEP-based BCI applications.

Evaluating the Correlation Between Stimulus Frequency Otoacoustic Emission Group Delays and Tuning Sharpness in a Cochlear Model.

A theoretical framework based on coherent reflection and filter theory predicts that the phase-gradient delays of stimulus frequency otoacoustic emissions (SFOAEs) are correlated with tuning sharpness in the mammalian cochlea. In this paper, we use a computational model of the cochlea to test this theory and to evaluate how SFOAE phase-gradient delays may be used to estimate the sharpness of cochlear tuning. This study is based on a physiologically motivated model which has been previously shown to predict key aspects of cochlear micromechanics. Cochlear roughness is introduced to model the reflection mechanism which underlies SFOAE generation. We then examine how varying the values of key model parameters or of the sound pressure level of the stimulus affects the relation between cochlear tuning and SFOAE delays. Finally, we quantify the ability of model simulations of SFOAE phase-gradient delays to provide reliable estimates of the tuning sharpness of the model. We find that variations of model parameters that cause significant broadening of basilar membrane (BM) tuning typically give rise to a sizeable reduction in SFOAE phase-gradient delays. However, some changes in model parameters may cause a significant broadening of BM tuning with only a moderate decrease in SFOAE delays. SFOAE delays can be used to estimate the tuning sharpness of the model with reasonable accuracy only in cases where broadening of cochlear tuning is associated with a significant reduction in SFOAE delays. The numerical results provide key insights about the correlations between cochlear tuning and SFOAE delays.

Application of Sound Waves During the Curing of an Acrylic Resin and Its Composites Based on Short Carbon Fibers and Carbon Nanofibers.

Research into particulate polymer composites is of significant interest due to their potential for enhancing material properties, such as strength, thermal stability, and conductivity while maintaining low weight and cost. Among the various techniques for preparing particle-based composites, ultrasonic wave stimulation is one of the principal laboratory-scale methods for enhancing the dispersion of the discontinuous phase. Nevertheless, there is a scarcity of empirical evidence to substantiate the impact of stimulating materials with natural sound frequencies within the acoustic spectrum, ranging from 20 Hz to 20 kHz, during their formation process. The present work investigates the effect of acoustic stimuli with frequencies of 56, 111, and 180 Hz on the properties of an acrylic-based polymer and its discontinuous carbon-based composites. The results indicated that the stimulus frequency affects the cure time of the studied systems, with a notable reduction of 31% and 21% in the cure times of the neat polymer and carbon-nanofiber-based composites, respectively, after applying a frequency of 180 Hz. Additionally, the higher stimulation frequencies reduced porosity in the samples, increased the degree of dispersion of the discontinuous phase, and altered the composite materials' thermal, optical, and electrical behavior.

Alpha-2 nicotinic acetylcholine receptors regulate spectral integration in auditory cortex

IntroductionIn primary auditory cortex (A1), nicotinic acetylcholine receptors (nAChRs) containing α2 subunits are expressed in layer 5 Martinotti cells (MCs)—inhibitory interneurons that send a main axon to superficial layers to inhibit distal apical dendrites of pyramidal cells (PCs). MCs also contact interneurons in supragranular layers that, in turn, inhibit PCs. Thus, MCs may regulate PCs via inhibition and disinhibition, respectively, of distal and proximal apical dendrites. Auditory inputs to PCs include thalamocortical inputs to middle layers relaying information about characteristic frequency (CF) and near-CF stimuli, and intracortical long-distance (“horizontal”) projections to multiple layers carrying information about spectrally distant (“nonCF”) stimuli. CF and nonCF inputs integrate to create broad frequency receptive fields (RFs). Systemic administration of nicotine activates nAChRs to “sharpen” RFs—to increase gain within a narrowed RF—resulting in enhanced responses to CF stimuli and reduced responses to nonCF stimuli. While nicotinic mechanisms to increase gain have been identified, the mechanism underlying RF narrowing is unknown.MethodsHere, we examine the role of α2 nAChRs in mice with α2 nAChR-expressing neurons labeled fluorescently, and in mice with α2 nAChRs genetically deleted.ResultsThe distribution of fluorescent neurons in auditory cortex was consistent with previous studies demonstrating α2 nAChRs in layer 5 MCs, including nonpyramidal somata in layer 5 and dense processes in layer 1. We also observed label in subcortical auditory regions, including processes, but no somata, in the medial geniculate body, and both fibers and somata in the inferior colliculus. Using electrophysiological (current-source density) recordings in α2 nAChR knock-out mice, we found that systemic nicotine failed to enhance CF-evoked inputs to layer 4, suggesting a role for subcortical α2 nAChRs, and failed to reduce nonCF-evoked responses, suggesting that α2 nAChRs regulate horizontal projections to produce RF narrowing.DiscussionThe results support the hypothesis that α2 nAChRs function to simultaneously enhance RF gain and narrow RF breadth in A1. Notably, a similar neural circuit may recur throughout cortex and hippocampus, suggesting widespread conserved functions regulated by α2 nAChRs.

A Variable-Stimulus Distortion Product Otoacoustic Emission Screening Method to Match Cochlear Place-Specific Properties.

Distortion product otoacoustic emissions (DPOAEs) are a popular screening tool for hearing loss in specific populations (e.g., newborns). Current screening protocols use stimulus conditions that are agnostic to local mechanical properties of the cochlea and are also limited to a narrow frequency range. We have recently reported locally optimized stimulus frequency ratio and level combinations for recording DPOAEs up to stimulus frequencies of 19 kHz. In normally functioning cochlea, optimized stimuli improved the signal to noise ratios and allowed the registration of higher DPOAE levels, especially at higher frequencies. The purpose of this study was to evaluate the clinical performance of these physiologically motivated, locally appropriate, stimulus parameters for a screening application to identify the presence of hearing loss. Subjects were 24 adults with sensorineural hearing loss and 31 adults with normal hearing. The cubic DPOAE was measured and analyzed up to frequencies of 16 kHz using a range of stimulus conditions. Receiver operating characteristic curves were used to identify stimulus combinations most sensitive to screening for hearing loss. Receiver operating characteristic curves demonstrated improved test efficacy for hearing loss detection when using stimulus frequency ratios and levels that are frequency-dependent and consistent with known mechanical properties of the cochlea. We propose a new DPOAE recording paradigm (variable-stimuli DP) using stimuli aligned to local cochlear properties which may improve early and accurate detection of decline in cochlear function.

Enhanced neural phase locking through audio-tactile stimulation.

Numerous studies have underscored the close relationship between the auditory and vibrotactile modality. For instance, in the peripheral structures of both modalities, afferent nerve fibers synchronize their activity to the external sensory stimulus, thereby providing a temporal code linked to pitch processing. The Frequency Following Response is a neurological measure that captures this phase locking activity in response to auditory stimuli. In our study, we investigated whether this neural signal is influenced by the simultaneous presentation of a vibrotactile stimulus. Accordingly, our findings revealed a significant increase in phase locking to the fundamental frequency of a speech stimulus, while no such effects were observed at harmonic frequencies. Since phase locking to the fundamental frequency has been associated with pitch perceptual capabilities, our results suggests that audio-tactile stimulation might improve pitch perception in human subjects.

A Comparison of Ocular Vestibular Evoked Myogenic Potentials via Audiometric and Nonaudiometric Bone Vibrators.

There is limited evidence demonstrating the ability of audiometric bone vibrators to elicit ocular vestibular evoked myogenic potentials (oVEMPs). The RadioEar B71 bone vibrator has insufficient power output to reliably evoke oVEMPs, which has previously left nonaudiometric and nonmedically approved devices such as the Brüel & Kjær Mini-shaker 4810 as the only feasible alternative. The newer RadioEar B81 model has a higher power output than its predecessor, but evidence for its suitability for eliciting oVEMPs has so far been mixed. This variability may be due to factors other than simply the power output, such as whether sufficient static force is applied to hold the transducer in place and transfer vibratory energy into the bone. This study aimed to test the hypothesis that bone-conducted oVEMPs can be obtained with the B81 that are equivalent to those from the Mini-shaker, the de facto gold-standard transducer for this response, when the outputs of the two transducers are matched and they are coupled with sufficient static force. oVEMPs elicited by both transducers were recorded in a counterbalanced within-groups design. Sixteen healthy adults (12 female; 22-47 years) with no history of hearing, balance, or neurological disorders were included in the study. One-cycle alternating tone-burst stimuli at 500 Hz were delivered to the mastoid from each transducer. The vibratory force levels were matched at 127 dB peak-to-peak equivalent force levels, and both were held in place with a static force around 10 N. oVEMP waveforms were gathered from the contralateral eye using the belly-tendon montage and were assessed for statistical equivalence. There was an absence of any statistically significant difference in N10 and N10-P15 amplitudes in oVEMPs from each transducer. Our results indicate that B81 can elicit oVEMPs with no meaningful differences to those from the Mini-shaker, provided effective stimulus levels are matched and static force is sufficient. Although further work is necessary to investigate equivalence at other stimulus frequencies and stimulation sites, the results support the use of the B81 to elicit 500Hz oVEMPs at the mastoid in a clinical setting.

The influence of spatial frequency information on temporal synchrony perception on audiovisual stimuli.

Previous studies have shown that the spatial frequency (SF) of visual stimuli alters the perceived timing of subjective simultaneity. However, these studies have been limited to the effects of a single SF component. In this study, I measured and compared the points of subjective simultaneity (PSS) for audiovisual stimuli among low, high, and composited SF components. This experiment comprised a dual-presentation timing task and a ternary response format to eliminate response bias. The results indicated that the PSS value of the composition-SF stimuli was more toward visual-lead timing than the low-SF stimuli and did not differ significantly from that of the high-SF stimuli. The correlation coefficients showed that the PSS in composition-SF stimuli marginally approximated that of high-SF stimuli higher than that of low-SF stimuli. Future studies are needed to confirm these findings using visual stimuli with a wider range of SF components and with a modulated contrast.

Beyond self-report: Measuring visual, auditory, and tactile mental imagery using a mental comparison task

Finding a reliable and objective measure of individual differences in mental imagery across sensory modalities is difficult, with measures relying on self-report scales or focusing on one modality alone. Based on the idea that mental imagery involves multimodal sensorimotor simulations, a mental comparison task (MCT) was developed across three studies and tested on adults (n = 96, 345, and 448). Analyses examined: (a) the internal consistency of the MCT, (b) whether lexical features of the MCT stimuli (word length and frequency) predicted performance, (c) whether the MCT related to two widely used self-report scales, (d) response latencies and accuracies across the visual, auditory, and tactile modalities, and (e) whether MCT performance was independent of processing speed. The MCT showed evidence of reliability and validity. Responses were fastest and most accurate for the visual modality, followed by the auditory and tactile. However, consistent with the idea that self-report questionnaires index a different aspect of mental imagery, the MCT showed minimal correlations with self-report imagery. Finally, relations between MCT scales remained strong after controlling for processing speed. Findings are discussed in relation to current understanding and measurement of mental imagery.

Audiogram Estimation Performance Using Auditory Evoked Potentials and Gaussian Processes.

Auditory evoked potentials (AEPs) play an important role in evaluating hearing in infants and others who are unable to participate reliably in behavioral testing. Discriminating the AEP from the much larger background activity, however, can be challenging and time-consuming, especially when several AEP measurements are needed, as is the case for audiogram estimation. This task is usually entrusted to clinicians, who visually inspect the AEP waveforms to determine if a response is present or absent. The drawback is that this introduces a subjective element to the test, compromising quality control of the examination. Various objective methods have therefore been developed to aid clinicians with response detection. In recent work, the authors introduced Gaussian processes (GPs) with active learning for hearing threshold estimation using auditory brainstem responses (ABRs). The GP is attractive for this task, as it can exploit the correlation structure underlying AEP waveforms across different stimulus levels and frequencies, which is often overlooked by conventional detection methods. GPs with active learning previously proved effective for ABR hearing threshold estimation in simulations, but have not yet been evaluated for audiogram estimation in subject data. The present work evaluates GPs with active learning for ABR audiogram estimation in a sample of normal-hearing and hearing-impaired adults. This involves introducing an additional dimension to the GP (i.e., stimulus frequency) along with real-time implementations and active learning rules for automated stimulus selection. The GP's accuracy was evaluated using the "hearing threshold estimation error," defined as the difference between the GP-estimated hearing threshold and the behavioral hearing threshold to the same stimuli. Test time was evaluated using the number of preprocessed and artifact-free epochs (i.e., the sample size) required for locating hearing threshold at each frequency. Comparisons were drawn with visual inspection by examiners who followed strict guidelines provided by the British Society of Audiology. Twenty-two normal hearing and nine hearing-impaired adults were tested (one ear per subject). For each subject, the audiogram was estimated three times: once using the GP approach, once using visual inspection by examiners, and once using a standard behavioral hearing test. The GP's median estimation error was approximately 0 dB hearing level (dB HL), demonstrating an unbiased test performance relative to the behavioral hearing thresholds. The GP additionally reduced test time by approximately 50% relative to the examiners. The hearing thresholds estimated by the examiners were 5 to 15 dB HL higher than the behavioral thresholds, which was consistent with the literature. Further testing is still needed to determine the extent to which these results generalize to the clinic. GPs with active learning enable automatic, real-time ABR audiogram estimation with relatively low test time and high accuracy. The GP could be used to automate ABR audiogram estimation or to guide clinicians with this task, who may choose to override the GP's decisions if deemed necessary. Results suggest that GPs hold potential for next-generation ABR hearing threshold and audiogram-seeking devices.

Suppression of the Excitability of Nociceptive Secondary Sensory Neurons Following Systemic Administration of Astaxanthin in Rats

Although astaxanthin (AST) has demonstrated a modulatory effect on voltage-gated Ca2+ (Cav) channels and excitatory glutamate neuronal transmission in vitro, particularly on the excitability of nociceptive sensory neurons, its action in vivo remains to be determined. This research sought to determine if an acute intravenous administration of AST in rats reduces the excitability of wide-dynamic range (WDR) spinal trigeminal nucleus caudalis (SpVc) neurons in response to nociceptive and non-nociceptive mechanical stimulation in vivo. In anesthetized rats, extracellular single-unit recordings were carried out on SpVc neurons following mechanical stimulation of the orofacial area. The average firing rate of SpVc WDR neurons in response to both gentle and painful mechanical stimuli significantly and dose-dependently decreased after the application of AST (1–5 mM, i.v.), and maximum suppression of discharge frequency for both non-noxious and nociceptive mechanical stimuli occurred within 10 min. These suppressive effects persisted for about 20 min. These results suggest that acute intravenous AST administration suppresses the SpVc nociceptive transmission, possibly by inhibiting Cav channels and excitatory glutamate neuronal transmission, implicating AST as a potential therapeutic agent for the treatment of trigeminal nociceptive pain without side effects.

Electro-Optically Configurable Synaptic Transistors With Cluster-Induced Photoactive Dielectric Layer for Visual Simulation and Biomotor Stimuli.

The integration of visual simulation and biorehabilitation devices promises great applications for sustainable electronics, on-demand integration and neuroscience. However, achieving a multifunctional synergistic biomimetic system with tunable optoelectronic properties at the individual device level remains a challenge. Here, an electro-optically configurable transistor employing conjugated-polymer as semiconductor layer and an insulating polymer (poly(1,8-octanediol-co-citrate) (POC)) with clusterization-triggered photoactive properties as dielectric layer is shown. These devices realize adeptly transition from electrical to optical synapses, featuring multiwavelength and multilevel optical synaptic memory properties exceeding 3 bits. Utilizing enhanced optical memory, the images learning and memory function for visual simulation are achieved. Benefiting from rapid electrical response akin to biological muscle activation, increased actuation occurs under increased stimulus frequency of gate voltage. Additionally, the transistor on POC substrate can be effectively degraded in NaOH solution due to degradation of POC. Pioneeringly, the electro-optically configurability stems from light absorption and photoluminescence of the aggregation cluster in POC layer after 200°C annealing. The enhancement of optical synaptic plasticity and integration of motion-activation functions within a single device opens new avenues at the intersection of optoelectronics, synaptic computing, and bioengineering.

Fluidity of social identities: implications for applying intersectionality

PurposeIntersectionality addresses complex avenues of oppression that emanate at the intersections of one’s identities. However, the intersectional framework assumes static identities, which are increasingly being acknowledged for their fluidity. This research explored the extent of the fluidity of social identities to draw implications for the application of the framework in research.Design/methodology/approach27 participants from a post-graduate elective course on diversity and inclusion identified their significant social identities, and submitted a write-up using hermeneutic phenomenology in which the participants shared their lived experiences of the fluidity of their social identities in different spaces they occupy or find themselves in.FindingsFluidity-triggering stimuli in different environments and their associations with identity-related motives were uncovered using thematic analysis. Stimuli operating at micro-, meso- and macro-levels rationally explained identity fluidity. However, in addition to types, intensity and frequency of stimuli, psychological factors, such as identity status, were decisive in determining the degree of generalization of stimuli across individuals and spaces that significantly influenced identity fluidity.Originality/valueThis research explored the extent of the fluidity of social identities to draw implications for the application of the intersectional framework in research. The findings contribute to future research by identifying limitations of the intersectional framework based on the fluidity of social identities arising from environmental stimuli that operate at micro-, meso- and macro-levels, and the extent of psychological generalization of these stimuli across spaces.

Enhanced Place Specificity of the Parallel Auditory Brainstem Response: An Electrophysiological Study

PurposeThis study investigates the effect of parallel stimulus presentation on the place specificity of the auditory brainstem response (ABR) in human listeners. Frequency-specific stimuli do not guarantee a response from the place on the cochlea corresponding only to that characteristic frequency — especially for brief and high-level stimuli. Adding masking noise yields responses that are more place specific, and our prior modeling study has suggested similar effects when multiple frequency-specific stimuli are presented in parallel. We tested this hypothesis experimentally here, comparing the place specificity of responses to serial and parallel stimuli at two stimulus frequencies and three stimulus rates.MethodsParallel ABR (pABR) stimuli were presented alongside high-pass filtered noise with a varied cutoff frequency. Serial presentation was also tested by isolating and presenting single-frequency stimulus trains from the pABR ensemble. Latencies of the ABRs were examined to assess place specificity of responses. Response bands were derived by subtracting responses from different high-pass noise conditions. The response amplitude from each derived response band was then used to determine how much individual frequency regions of the auditory system were contributing to the overall response.ResultsWe found that parallel presentation improves place specificity of ABRs for the lower stimulus frequency and at higher stimulus rates. At a higher stimulus frequency, serial and parallel presentations were equally place specific.ConclusionParallel presentation can provide more place-specific responses than serial for lower stimulus frequencies. The improvement increases with higher stimulus rates and is in addition to the pABR’s primary benefit of faster test times.

The impact of virtual reality and distractors on attentional processes: insights from EEG.

Virtual reality (VR) allows to create controlled scenarios in which the quantity of stimuli can be modulated, as happen in real-life, where humans are subjected to various multisensory-often overlapping-stimuli. The present research aimed to study changes in attentional processes within an auditory oddball paradigm during a virtual exploration, while varying the amount of distractors. Twenty healthy volunteers underwent electroencephalography (EEG) during three different experimental conditions: an auditory oddball without VR (No-VR condition), an auditory oddball during VR exploration without distractors (VR-Empty condition), and an auditory oddball during VR exploration with a high level of distractors (VR-Full condition). Event-related potentials (ERPs) were computed averaging epochs of EEGs and analyzing peaks at 100ms (N100) and 300ms (P300) latencies. Results showed modulation of N100 amplitude in Fz and of P300 amplitude in Pz. Statistically significant differences in latency were observed only for P300 where the latency results delayed from the No-VR to VR-Full. The scalp topography revealed for P100 no significant differences between frequent and rare stimuli in either the No-VR and VR-Empty conditions. However, significant results were found in N100 in VR-Full condition. For P300, results showed differences between frequent and rare stimuli, in every condition. However, this difference is gradually less widespread from No-VR condition to the VR-Full. The emerging integration of VR with EEG may have important implications for studying brain attentional processing.

Frequency synaptic behavior of ZnO/HfZrO memristor with pulsed stimuli

The synaptic response of ZnO/HfZrO memristor devices to electrical stimuli was studied. It was found that the frequency of the stimuli affects the rate of current increase, which can be explained by the cluster state of oxygen vacancies at the interface of ZnO/HfZrO. This variation in the synaptic response due to stimulus frequency was consistent with the dynamic adjustment of tolerance thresholds observed in the human brain's response to environmental stimuli. The rate of change in current, representing the sensitivity to stimuli, mirrors the biological nervous system's reaction to environmental changes, such as Ebbinghaus forgetting behavior. Additionally, frequent irregular changes in stimuli lead to a reduced lifespan of the devices, highly resembling the biological lifetime-injure on frequent environmental fluctuations. These findings highlight the memristors' significant similarity to biological nerves in response to stimuli, confirming their tremendous potential in bionic synaptic simulation applications.

Effect of Electrode Montage on Frequency Tuning Properties of Air-Conducted Ocular Vestibular-Evoked Myogenic Potential.

The use of a 500 Hz tone burst over other frequencies was adopted for the clinical recording of ocular vestibular-evoked myogenic potential (oVEMP) on the basis that this stimulus frequency produces larger response amplitudes (frequency tuning) than the other frequencies. However, the possibility of reflex contamination due to a spatially displaced reference electrode from the muscle of the response origin raises questions about using an infraorbital (IO) montage. Nonetheless, the belly-tendon (BT) montage, which places both the recording electrodes over the inferior oblique muscle, increases the chances of obtaining a response with greater contribution from the inferior oblique muscle. However, whether this response continues to show the frequency tuning to 500 Hz is not known. Therefore, the present study aimed to examine the frequency tuning of oVEMP using various electrode montages. Thirty-eight young adults underwent simultaneous oVEMP recording from IO, BT, chin-referenced, and sternum-referenced electrode montages in response to 250, 500, 750, 1000, 1500, 2000, 3000, and 4000 Hz tone bursts. The frequency tuning most often coincided with a 750-Hz tone burst irrespective of the montage, with the BT montage exhibiting significantly higher response rates and larger peak to peak amplitudes than other montages (p < 0.008). Further, there was a "substantial" agreement on frequency tuning between BT and IO montages. With better response rates and response amplitudes yet similar frequency tuning to the IO montage, the BT montage can be a better option for the clinical recording of oVEMP across frequencies.

Exploration of stress reactivity and fear conditioning on intrusive memory frequency in a conditioned-intrusion paradigm

Background and objectivesThe conditioned-intrusion paradigm was designed to provide insight into the relationship between fear conditioning and intrusive memory formation, which is relevant to understanding posttraumatic stress disorder symptoms and treatment. However, boundary conditions of this new paradigm have not been explored and it is currently not known whether findings from this work are valid in a clinical context. MethodsIn the current study, we explored the relationship between stress reactivity to trauma film clips, usual exposure to violent media, renewal of fear conditioning using skin conductance as well as subjective ratings, and the effect of shock versus film clip during conditioning on the frequency of intrusive memories. An adapted fear conditioning paradigm using trauma clips as unconditional stimuli was used, and participants subsequently reported intrusive memories of the trauma clips. ResultsSkin conductance responses to conditioned stimuli paired with shocks and film clips were significantly higher than conditioned stimuli paired with film clips alone. Subjective stress reactivity, previous exposure to violent media, and film valence rating were associated with the frequency of intrusive memories. No aspects of fear conditioning were associated with intrusive memories, and factor analysis suggested the fear conditioning and stress related to film clip viewing were mostly separate constructs. Similarly, content and triggers of intrusive memories were usually film-clip related rather than conditional stimulus related. LimitationsWe did not observe strong conditioning effects of the unconditional stimuli to conditional stimuli, which were shapes rather than high frequency stimuli such as faces. ConclusionsThese findings provide potential boundary conditions for this paradigm and suggest multiple ways in which the validity of the paradigm can be tested in the future.

Peripheral hearing sensitivity is similar between the sexes in a benthic turtle species despite the larger body size of males.

Sexually dimorphic hearing sensitivity has evolved in many vertebrate species, and the sex with a larger body size typically shows more sensitive hearing. However, generalizing this association is controversial. Research on sexually dimorphic hearing sensitivity contributes to an understanding of auditory sense functions, adaptations, and evolution among species. Therefore, the hypothesized association between body size and hearing needs further validation, especially in specific animal groups. In this study, we assessed hearing sensitivity by measuring auditory brainstem responses (ABRs) in both sexes of 3-year-old Chinese softshell turtles (Pelodiscus sinensis). In this species, male bodies are larger than those of female, and individuals spend most of their lives in the mud at the bottom of freshwater habitats. We found that for both sexes, the hearing sensitivity bandwidth was 0.2-0.9 kHz. Although males were significantly larger than females, no significant differences in ABR thresholds or latencies were found between males and females at the same stimulus frequency. These results indicate that P. sinensis hearing is only sensitive to low-frequency (typically <0.9 kHz) sound signals and that sexually dimorphic hearing sensitivity is not a trait that has evolved in P. sinensis. Physiological and environmental reasons may account for P. sinensis acoustic communication via low-frequency sound signals and the lack of sexually dimorphic hearing sensitivity in these benthic turtles. The results of this study refine our understanding of the adaptation and evolution of the vertebrate auditory system.