The effect of psychological stress and expectation on auditory perception: A signal detection analysis

Stressful life events and tinnitus : Reflections and speculations

The role of life events has not been extensively studied in the context of tinnitus. There is, however, evidence about the psychological impact of tinnitus and about the influence of psychological processes as mediators of the tinnitus experience. On the basis of this evidence, the possibility that stressful life events can act as a trigger for tinnitus is discussed; although the evidence is fragmentary and indirect, the possibility cannot be discounted. It is argued that the onset of tinnitus and the associated clinical encounters can constitute an acute stressful life event, and the ongoing experience of tinnitus can be regarded as a chronic stressful life event. Interactions between ongoing tinnitus and other life events are discussed. Possible mechanisms in terms of stress influencing predictive processing and signal detection judgments are considered.

Neural correlates of flexible sound perception in the auditory midbrain and thalamus

Hearing is an active process in which listeners must detect and identify sounds, segregate and discriminate stimulus features, and extract their behavioral relevance. Adaptive changes in sound detection can emerge rapidly, during sudden shifts in acoustic or environmental context, or more slowly as a result of practice. Although we know that context- and learning-dependent changes in the spectral and temporal sensitivity of auditory cortical neurons support many aspects of flexible listening, the contribution of subcortical auditory regions to this process is less understood. Here, we recorded single- and multi-unit activity from the central nucleus of the inferior colliculus (ICC) and the ventral subdivision of the medial geniculate nucleus (MGV) of Mongolian gerbils under two different behavioral contexts: as animals performed an amplitude modulation (AM) detection task and as they were passively exposed to AM sounds. Using a signal detection framework to estimate neurometric sensitivity, we found that neural thresholds in both regions improved during task performance, and this improvement was driven by changes in firing rate rather than phase locking. We also found that ICC and MGV neurometric thresholds improved and correlated with behavioral performance as animals learn to detect small AM depths during a multi-day perceptual training paradigm. Finally, we reveal that in the MGV, but not the ICC, context-dependent enhancements in AM sensitivity grow stronger during perceptual training, mirroring prior observations in the auditory cortex. Together, our results suggest that the auditory midbrain and thalamus contribute to flexible sound processing and perception over rapid and slow timescales.

Advances and challenges in the detection of academic stress and anxiety in the classroom: A literature review and recommendations

In recent years, stress and anxiety have been identified as two of the leading causes of academic underachievement and dropout. However, there is little work on the detection of stress and anxiety in academic settings and/or its impact on the performance of undergraduate students. Moreover, there is a gap in the literature in terms of identifying any computing, information technologies, or technological platforms that help educational institutions to identify students with mental health problems. This paper aims to systematically review the literature to identify the advances, limitations, challenges, and possible lines of research for detecting academic stress and anxiety in the classroom. Forty-four recent articles on the topic of detecting stress and anxiety in academic settings were analyzed. The results show that the main tools used for detecting anxiety and stress are psychological instruments such as self-questionnaires. The second most used method is acquiring and analyzing biological signals and biomarkers using commercial measurement instruments. Data analysis is mainly performed using descriptive statistical tools and pattern recognition techniques. Specifically, physiological signals are combined with classification algorithms. The results of this method for detecting anxiety and academic stress in students are encouraging. Using physiological signals reduces some of the limitations of psychological instruments, such as response time and self-report bias. Finally, the main challenge in the detection of academic anxiety and stress is to bring detection systems into the classroom. Doing so, requires the use of non-invasive sensors and wearable systems to reduce the intrinsic stress caused by instrumentation.

Eliciting false auditory perceptions using speech frequencies and semantic priming: a signal detection approach

INTRODUCTION

Individuals experiencing auditory hallucinations (AH) tend to perceive voices when exposed to random noise. However, the factors driving this tendency remain unclear. The present study examined the interaction of a top-down (expectations) and bottom-up (type of noise) process to better understand the mechanisms that underlie AH.

METHODS

Fifty-two healthy individuals (29 with high proneness and 23 with low proneness to AH) completed a signal detection task, in which they listened to pre-recorded sentences. The last word was either masked by noise or only noise was presented without the word. Two types of noise existed (speech-related versus speech-unrelated frequencies) and words were characterised by either high or low levels of semantic expectation.

RESULTS

Participants with high proneness to AH showed a more liberal decision bias (i.e., they were more likely to report having heard a word) and poorer discrimination ability as compared to participants with low proneness to AH - but only when the word was masked by speech-related noises and the level of expectation was high. Further, the more liberal decision bias correlated negatively with the tendency to experience AH.

CONCLUSION

This novel paradigm demonstrated an interaction between top-down (level of expectation) and bottom-up (type of noise) processes, supporting current theoretical models of AH.

The perceived salience of vocal emotions is dampened in non-clinical auditory verbal hallucinations

Introduction: Auditory verbal hallucinations (AVH) are a cardinal symptom of schizophrenia but are also reported in the general population without need for psychiatric care. Previous evidence suggests that AVH may reflect an imbalance of prior expectation and sensory information, and that altered salience processing is characteristic of both psychotic and non-clinical voice hearers. However, it remains to be shown how such an imbalance affects the categorisation of vocal emotions in perceptual ambiguity.Methods: Neutral and emotional nonverbal vocalisations were morphed along two continua differing in valence (anger; pleasure), each including 11 morphing steps at intervals of 10%. College students (N = 234) differing in AVH proneness (measured with the Launay-Slade Hallucination Scale) evaluated the emotional quality of the vocalisations.Results: Increased AVH proneness was associated with more frequent categorisation of ambiguous vocalisations as 'neutral', irrespective of valence. Similarly, the perceptual boundary for emotional classification was shifted by AVH proneness: participants needed more emotional information to categorise a voice as emotional.Conclusions: These findings suggest that emotional salience in vocalisations is dampened as a function of increased AVH proneness. This could be related to changes in the acoustic representations of emotions or reflect top-down expectations of less salient information in the social environment.

Neuropsychological correlates of evocative multimodal speech: The combined roles of fearful prosody, visuospatial attention, cortisol response, and anxiety

Past research reveals left-hemisphere dominance for linguistic processing and right-hemisphere dominance for emotional prosody processing during auditory language comprehension, a pattern also found in visuospatial attention studies where listeners are presented with a view of the talker's face. Is this lateralization pattern for visuospatial attention and language processing upheld when listeners are experiencing a stress response? To investigate this question, participants completed the Trier Social Stress Test (TSST) between administrations of a visuospatial attention and language comprehension dual-task paradigm. Subjective anxiety, cardiovascular, and saliva cortisol measures were taken before and after the TSST. Higher language comprehension scores in the post-TSST neutral prosody condition were associated with lower cortisol responses, differences in blood pressure, and less subjective anxiety. In this challenging task, visuospatial attention was most focused at the mouth region, both prior to and after stress induction. Greater visuospatial attention on the left side of the face image, compared to the right side, indicated greater right hemisphere activation. In the Fear, but not the Neutral, prosody condition, greater cortisol response was associated with greater visuospatial attention to the left side of the face image. Results are placed into theoretical context, and can be applied to situations where stressed listeners must interpret emotionally evocative language.

Expression Patterns of the Neuropeptide Urocortin 3 and Its Receptor CRFR2 in the Mouse Central Auditory System

Sensory systems have to be malleable to context-dependent modulations occurring over different time scales, in order to serve their evolutionary function of informing about the external world while also eliciting survival-promoting behaviors. Stress is a major context-dependent signal that can have fast and delayed effects on sensory systems, especially on the auditory system. Urocortin 3 (UCN3) is a member of the corticotropin-releasing factor family. As a neuropeptide, UCN3 regulates synaptic activity much faster than the classic steroid hormones of the hypothalamic-pituitary-adrenal axis. Moreover, due to the lack of synaptic re-uptake mechanisms, UCN3 can have more long-lasting and far-reaching effects. To date, a modest number of studies have reported the presence of UCN3 or its receptor CRFR2 in the auditory system, particularly in the cochlea and the superior olivary complex, and have highlighted the importance of this stress neuropeptide for protecting auditory function. However, a comprehensive map of all neurons synthesizing UCN3 or CRFR2 within the auditory pathway is lacking. Here, we utilize two reporter mouse lines to elucidate the expression patterns of UCN3 and CRFR2 in the auditory system. Additional immunolabelling enables further characterization of the neurons that synthesize UCN3 or CRFR2. Surprisingly, our results indicate that within the auditory system, UCN3 is expressed predominantly in principal cells, whereas CRFR2 expression is strongest in non-principal, presumably multisensory, cell types. Based on the presence or absence of overlap between UCN3 and CRFR2 labeling, our data suggest unusual modes of neuromodulation by UCN3, involving volume transmission and autocrine signaling.

A Systematic Review of the experimental induction of auditory perceptual experiences

BACKGROUND AND OBJECTIVES

Voice-hearing exists on a continuum and research studies have utilised experimental paradigms in an attempt to induce unusual auditory experiences in clinical and non-clinical samples. The aim of the current review was to systematically identify, review and appraise voice-hearing induction paradigms in order to guide researchers.

METHODS

Five databases were searched for studies in which an experimental manipulation was used with the aim of inducing an auditory experience akin to voice-hearing. Papers were assessed for quality and the voice-hearing paradigms critically appraised.

RESULTS

Forty-nine studies, included in 41 papers, were reviewed. Studies were organised into five groups based on the type of voice-hearing paradigm used: sensory deprivation/limitation; hallucination suggestion; combined suggestion and ambiguous stimulus; signal detection and voice detection tasks; and auditory discrimination/transformation. Signal and voice detection tasks were found to be the most robust paradigms. The quality of paradigms was assessed, and their strengths and limitations evaluated, including evidence in relation to their utility, ecological validity and usability.

LIMITATIONS

The current review excluded case studies, grey literature and studies which were not written in the English language, and as such voice-hearing paradigms may have been missed.

CONCLUSIONS

Voice-hearing paradigms vary in their ecological validity and experimental robustness. A challenge for future research is to develop a paradigm in which internally generated material can be attributed externally in a way that more closely represents inner speech and the experience of voice-hearing.

Psychosis proneness, loneliness, and hallucinations in nonclinical individuals

Hallucinations occur along a continuum of normal functioning. Investigating the factors related to this experience in nonclinical individuals may offer important information for understanding the etiology of hallucinations in psychiatric populations. In this study we test the relationship between psychosis proneness, loneliness, and auditory hallucinations in a nonclinical sample using the White Christmas paradigm. Seventy-six undergraduate students participated in this study. We found that slightly more than half of our participants endorsed a hallucinatory experience during the White Christmas paradigm. However, we did not observe a relationship between the number of hallucinatory experiences and schizotypy, propensity to hallucinate, or loneliness. Moreover, there were no differences on these measures between individuals who reported hearing a hallucination during the White Christmas paradigm relative to those who did not. Thus, there may be other contextual factors not investigated in this study that might clarify the mechanism by which auditory hallucinations are experienced in a nonclinical population.

Similar EEG Activity Patterns During Experimentally-Induced Auditory Illusions and Veridical Perceptions

Hallucinations and illusions are two instances of perceptual experiences illustrating how perception might diverge from external sensory stimulations and be generated or altered based on internal brain states. The occurrence of these phenomena is not constrained to patient populations. Similar experiences can be elicited in healthy subjects by means of suitable experimental procedures. Studying the neural mechanisms underlying these experiences not only has the potential to expand our understanding of the brain's perceptual machinery but also of how it might get impaired. In the current study, we employed an auditory signal detection task to induce auditory illusions by presenting speech snippets at near detection threshold intensity embedded in noise. We investigated the neural correlates of auditory false perceptions by examining the EEG activity preceding the responses in speech absent (false alarm, FA) trials and comparing them to speech present (hit) trials. The results of the comparison of event-related potentials (ERPs) in the activation period vs. baseline revealed the presence of an early negativity (EN) and a late positivity (LP) similar in both hits and FAs, which were absent in misses, correct rejections (CR) and control button presses (BPs). We postulate that the EN and the LP might represent the auditory awareness negativity (AAN) and centro-parietal positivity (CPP) or P300, respectively. The event-related spectral perturbations (ERSPs) exhibited a common power enhancement in low frequencies (<4 Hz) in hits and FAs. The low-frequency power enhancement has been frequently shown to be accompanied with P300 as well as separately being a marker of perceptual awareness, referred to as slow cortical potentials (SCP). Furthermore, the comparison of hits vs. FAs showed a significantly higher LP amplitude and low frequency power in hits compared to FAs. Generally, the observed patterns in the present results resembled some of the major neural correlates associated with perceptual awareness in previous studies. Our findings provide evidence that the neural correlates associated with conscious perception, can be elicited in similar ways in both presence and absence of externally presented sensory stimuli. The present findings did not reveal any pre-stimulus alpha and beta modulations distinguishing conscious vs. unconscious perceptions.

Hallucinations: diagnosis, neurobiology and clinical management

Hallucinations are important diagnostic symptoms in schizophrenia, but also occur in other medical and neuropsychiatric conditions. Not all patients with hallucinations are psychotic. There has been a surge of interest in the topic of hallucinations, as new research data have begun to reveal their neurobiology. Hallucinogenic molecules may also serve as new scaffolds for the development of new psychotropic drugs. We searched and reviewed recent literature, focusing on the refinement of clinical management, which was inspired by new data regarding the neurobiology of hallucination subtypes. We concluded that the successful management of hallucinations depends on accurate differential diagnosis to identify subtypes, which would then determine the most appropriate treatment.

Testing a model of auditory hallucinations: the role of negative emotions and cognitive resources

Introduction: Models of auditory hallucinations (AH) state that AH arise through an interaction between negative emotions and limited available cognitive resources. However, this hypothesis has never been directly tested. Methods: A two-by-two factorial design was used to examine the effect of emotions (neutral VS negative) and available cognitive resources (high VS low) on the elicitation of false alarms in an auditory signal detection paradigm. One hundred and seventy four healthy participants were assigned to one of the four experimental conditions. While participants were listening to white noise, their emotional state was manipulated using affective pictures and the level of available cognitive resources was manipulated using a visual N-back task. Results: Results revealed significant interaction effects between emotions and cognitive resources on the number of false alarms. In particular, participants with fewer available cognitive resources and at the same time who were in a negative emotional state, tended to hear significantly more false alarms. In addition, the degree of certitude was significantly correlated with a higher degree of hallucination proneness. Conclusions: Such results are in agreement with models of AH and they provide new data for the understanding of the emotional and cognitive mechanisms that underpin AH.

Optimising the Structure-Function Relationship at the Locus of Deficit in Retinal Disease

Technologies such as optical coherence tomography have facilitated the visualization of anatomical tissues such as that of the retina. The availability of in vivo retinal anatomical data has led to the hypothesis that it may be able to accurately predict visual function from anatomical information. However, accurate determination of the structure-function relationship has remained elusive in part due to contributions of non-retinal sources of variability, thus imposing potential limitations in the fidelity of the relationship. Furthermore, differences in manifestation of functional loss due to different retinal loci of change (inner retina or outer retinal elements) have also been the subject of debate. Here, we assessed the application of a novel, more objective psychophysical paradigm to better characterize the relationship between functional and structural characteristics in the eye. Using ocular diseases with known loci of anatomical change (glaucoma, inner retinal loss; and retinitis pigmentosa, outer retinal loss), we compared conventional more subjective psychophysical techniques that may be contaminated by the presence of non-retinal sources of variability with our more objective approach. We show that stronger correlations between underlying retinal structure and visual function can be achieved across a breadth of anatomical change by using a more objective psychophysical paradigm. This was independent of the locus of structural loss (at the ganglion cells for glaucoma or photoreceptors for retinitis pigmentosa), highlighting the role of downstream retinal elements to serve as anatomical limiting factors for studying the structure-function relationship. By reducing the contribution of non-retinal sources of variability in psychophysical measurements, we herein provide a structure-function model with higher fidelity. This reinforces the need to carefully consider the psychophysical protocol when examining the structure-function relationship in sensory systems.

Differences in Stress-Induced Modulation of the Auditory System Between Wistar and Lewis Rats

Many aspects of stress-induced physiological and psychological effects have been characterized in people and animals. However, stress effects on the auditory system are less explored and their mechanisms are not well-understood, in spite of its relevance for a variety of diseases, including tinnitus. To expedite further research of stress-induced changes in the auditory system, here we compare the reactions to stress among Wistar and Lewis rats. The animals were stressed for 24 h, and subsequently we tested the functionality of the outer hair cells (OHCs) using distortion product otoacoustic emissions (DPOAEs) and auditory neurons using evoked auditory brainstem responses (ABR). Lastly, using Western blot, we analyzed the levels of plasticity-related proteins in the inferior colliculus, confirming that the inferior colliculus is involved in the adaptive changes that occur in the auditory system upon stress exposure. Surprisingly, the two strains reacted to stress quite differently: Lewis rats displayed a lowering of their auditory threshold, whereas it was increased in Wistar rats. These functional differences were seen in OHCs of the apical region (low frequencies) and in the auditory neurons (across several frequencies) from day 1 until 2 weeks after the experimental stress ended. Wistar and Lewis rats may thus provide models for auditory threshold increase and decrease, respectively, which can both be observed in different patients in response to stress.

Evidence of a Right Ear Advantage in the absence of auditory targets

The Right Ear Advantage effect (REA) was explored in a white noise speech illusion paradigm: binaural white noise (WN) could be presented i) in isolation (WN condition), ii) overlapped to a voice pronouncing the vowel /a/ presented in the left ear (LE condition), iii) overlapped to a voice pronouncing the vowel /a/ presented in the right ear (RE condition). Participants were asked to report in which ear the voice has been perceived. The voice could be female or male, and it could be presented at 4 different intensities. Participants carried out the task correctly both in LE and in RE conditions. Importantly, in the WN condition the “right ear” responses were more frequent with respect to both the chance level and the “left ear” responses. A perceptual REA was confirmed both in LE and RE conditions. Moreover, when the voice was presented at low intensities (masked by WN), it was more frequently reported in the right than in the left ear (“illusory” REA). A positive correlation emerged between perceptual and illusory REA. Potential links of the REA effects with auditory hallucinations are discussed.

Is this my voice or yours? The role of emotion and acoustic quality in self-other voice discrimination in schizophrenia

INTRODUCTION

Impairments in self-other voice discrimination have been consistently reported in schizophrenia, and associated with the severity of auditory verbal hallucinations (AVHs). This study probed the interactions between voice identity, voice acoustic quality, and semantic valence in a self-other voice discrimination task in schizophrenia patients compared with healthy subjects. The relationship between voice identity discrimination and AVH severity was also explored.

METHODS

Seventeen chronic schizophrenia patients and 19 healthy controls were asked to read aloud a list of adjectives characterised by emotional or neutral content. Participants' voice was recorded in the first session. In the behavioural task, 840 spoken words differing in identity (self/non-self), acoustic quality (undistorted/distorted), and semantic valence (negative/positive/neutral) were presented. Participants indicated if the words were spoken in their own voice, another person's voice, or were unsure.

RESULTS

Patients were less accurate than controls in the recognition of self-generated speech with negative content only. Impaired recognition of negative self-generated speech was associated with AVH severity ("voices conversing").

CONCLUSIONS

These results suggest that abnormalities in higher order processes (evaluation of the salience of a speech stimulus) modulate impaired self-other voice discrimination in schizophrenia. Abnormal processing of negative self-generated speech may play a role in the experience of AVH.

Event-related potentials elicited by the Deutsch "high-low" word illusion in the patients with first-episode schizophrenia with auditory hallucinations

BACKGROUND

The exact cerebral structural and functional mechanisms under the auditory verbal hallucinations (AVHs) in schizophrenia are still unclear. The Deutsch "high-low" word illusion might trigger attentional responses mimicking those under AVHs.

METHODS

We therefore have invited 16 patients with first-episode, paranoid schizophrenia, and 16 age- and gender-matched healthy volunteers to undergo the "oddball" event-related potentials elicited by the illusion. The clinical characteristics of patients were measured with the positive and negative symptom scale.

RESULTS

Besides the longer reaction time to the illusion, the standard P2 latency was shortened, the N2 latency was prolonged, and both N1 and P3 amplitudes were reduced in patients. The P3 source analyses showed the activated bilateral temporal lobes, parietal lobe and cingulate cortex in both groups, left inferior temporal gyrus in controls, and left postcentral gyrus in schizophrenia. Moreover, the N1 amplitude was positively correlated with the paranoid score in patients.

CONCLUSIONS

Our results were in line with previous neurophysiological and neuroimaging reports of hallucination or auditory processing in schizophrenia, and illustrated a whole process of cerebral information processing from N1 to P3, indicating this illusion had triggered a dynamic cerebral response similar to that of the AVHs had engaged.

Effect of Frustration on Brain Activation Pattern in Subjects with Different Temperament

In spite of the prevalence of frustration in everyday life, very few neuroimaging studies were focused on this emotional state. In the current study we aimed to examine effects of frustration on brain activity while performing a well-learned task in participants with low and high tolerance for arousal. Prior to the functional magnetic resonance imaging session, the subjects underwent 2 weeks of Braille reading training. Frustration induction was obtained by using a novel highly difficult tactile task based on discrimination of Braille-like raised dots patterns and negative feedback. Effectiveness of this procedure has been confirmed in a pilot study using galvanic skin response and questionnaires. Brain activation pattern during tactile discrimination task before and after frustration were compared directly. Results revealed changes in brain activity in structures mostly reported in acute stress studies: striatum, cingulate cortex, insula, middle frontal gyrus and precuneus and in structures engaged in tactile Braille discrimination: SI and SII. Temperament type affected activation pattern. Subjects with low tolerance for arousal showed higher activation in the posterior cingulate gyrus, precuneus, and inferior parietal lobule than high reactivity group. Even though performance in the discrimination trials following frustration was unaltered, we observed increased activity of primary and secondary somatosensory cortex processing the tactile information. We interpret this effect as an indicator of additional involvement required to counteract the effects of frustration.

Tailoring Cognitive Behavioral Therapy to Subtypes of Voice-Hearing

Cognitive behavioral therapy (CBT) for voice-hearing (i.e., auditory verbal hallucinations; AVH) has, at best, small to moderate effects. One possible reason for this limited efficacy is that current CBT approaches tend to conceptualize voice-hearing as a homogenous experience in terms of the cognitive processes involved in AVH. However, the highly heterogeneous nature of voice-hearing suggests that many different cognitive processes may be involved in the etiology of AVH. These heterogeneous voice-hearing experiences do, however, appear to cluster into a set of subtypes, opening up the possibility of tailoring treatment to the subtype of AVH that a voice-hearer reports. In this paper, we (a) outline our rationale for tailoring CBT to subtypes of voice-hearing, (b) describe CBT for three putative subtypes of AVH (inner speech-based AVH, memory-based AVH, and hypervigilance AVH), and (c) discuss potential limitations and problems with such an approach. We conclude by arguing that tailoring CBT to subtypes of voice-hearing could prove to be a valuable therapeutic development, which may be especially effective when used in early intervention in psychosis services.

The effect of auditory verbal imagery on signal detection in hallucination-prone individuals

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Investigated relation between hallucinations, mental imagery and signal detection.

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Individuals prone to hallucinations showed a lower SDT response bias with imagery.

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Finding held for both instructed and self-reported use of auditory verbal imagery.

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Atypical auditory imagery may lead to the generation of auditory hallucinations.

Cognitive models have suggested that auditory hallucinations occur when internal mental events, such as inner speech or auditory verbal imagery (AVI), are misattributed to an external source. This has been supported by numerous studies indicating that individuals who experience hallucinations tend to perform in a biased manner on tasks that require them to distinguish self-generated from non-self-generated perceptions. However, these tasks have typically been of limited relevance to inner speech models of hallucinations, because they have not manipulated the AVI that participants used during the task. Here, a new paradigm was employed to investigate the interaction between imagery and perception, in which a healthy, non-clinical sample of participants were instructed to use AVI whilst completing an auditory signal detection task. It was hypothesized that AVI-usage would cause participants to perform in a biased manner, therefore falsely detecting more voices in bursts of noise. In Experiment 1, when cued to generate AVI, highly hallucination-prone participants showed a lower response bias than when performing a standard signal detection task, being more willing to report the presence of a voice in the noise. Participants not prone to hallucinations performed no differently between the two conditions. In Experiment 2, participants were not specifically instructed to use AVI, but retrospectively reported how often they engaged in AVI during the task. Highly hallucination-prone participants who retrospectively reported using imagery showed a lower response bias than did participants with lower proneness who also reported using AVI. Results are discussed in relation to prominent inner speech models of hallucinations.

Stress improves selective attention towards emotionally neutral left ear stimuli

Research concerning the impact of psychological stress on visual selective attention has produced mixed results. The current paper describes two experiments which utilise a novel auditory oddball paradigm to test the impact of psychological stress on auditory selective attention. Participants had to report the location of emotionally-neutral auditory stimuli, while ignoring task-irrelevant changes in their content. The results of the first experiment, in which speech stimuli were presented, suggested that stress improves the ability to selectively attend to left, but not right ear stimuli. When this experiment was repeated using tonal stimuli the same result was evident, but only for female participants. Females were also found to experience greater levels of distraction in general across the two experiments. These findings support the goal-shielding theory which suggests that stress improves selective attention by reducing the attentional resources available to process task-irrelevant information. The study also demonstrates, for the first time, that this goal-shielding effect extends to auditory perception.