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• Examining experienced lateralization of sounds over headphones with electroencephalography

  2025. Billy Gerdfeldter, Mingaile Greiciute, Stefan Wiens. Neuropsychologia 207

  Artikel

  In the search for the neural correlates of auditory consciousness, a candidate has been found using electroencephalography: the auditory awareness negativity (AAN). Earlier studies have investigated the AAN in response to lateralized sound. With headphones, there is a clear lateralization of AAN when two auditory lateralization cues are combined: the interaural level difference (ILD) and interaural time difference (ITD). To separate the contribution of these cues to a lateralized AAN, we tested three stimulus conditions with headphones: A combination of ILD and ITD, solely ITD, and monaural stimulation. Results suggest that ILD and ITD are required in conjunction for a lateralized AAN, and neither ITD nor monaural stimulation can yield a lateralized AAN. These results suggest that event-related potentials may be limited in measuring the lateralization of the neural correlates of auditory consciousness to lateralized sounds, depending on auditory cues and acoustic environment.

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• Examining the lateralization of electrophysiological correlates of auditory awareness

  2024. Billy Gerdfeldter, Annika Andersson, Stefan Wiens. Psychophysiology 61 (11)

  Artikel

  The neurological basis for perceptual awareness remains unclear, and theories disagree as to whether sensory cortices per se generate awareness. Critically, neural activity in the sensory cortices is only a neural correlate of consciousness (NCC) if it closely matches the contents of perceptual awareness. Research in vision and touch suggest that contralateral activity in sensory cortices is an NCC. Similarly, research in hearing with two sound sources (left and right) presented over headphones also suggests that a candidate NCC called the auditory awareness negativity (AAN) matches perceived location of sound. The current study used 13 different sound sources presented over loudspeakers for natural localization cues and measured event-related potentials to a threshold stimulus in a sound localization task. Preregistered Bayesian mixed models provided moderate evidence against an overall AAN and very strong evidence against its lateralization. Because of issues regarding data quantity and quality, exploratory analyses with aggregated data from multiple loudspeakers were conducted. Results provided moderate evidence for an overall AAN and strong evidence against its lateralization. Nonetheless, the interpretations of these results remain inconclusive. Therefore, future research should reduce the number of conditions and/or test over several sessions to procure a sufficient amount of data. Taken at face value, the results may suggest issues with AAN as an NCC of auditory awareness, as it does not laterally map onto experiences in a free-field auditory environment, in contrast to the NCCs of vision and touch.

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• Neural electrophysiological correlates of detection and identification awareness

  2023. Stefan Wiens, Annika Andersson, Josef Gravenfors. Cognitive, Affective, & Behavioral Neuroscience 23, 1303-1321

  Artikel

  Humans have conscious experiences of the events in their environment. Previous research from electroencephalography (EEG) has shown visual awareness negativity (VAN) at about 200 ms to be a neural correlate of consciousness (NCC). However, when considering VAN as an NCC, it is important to explore which particular experiences are associated with VAN. Recent research proposes that VAN is an NCC of lower-level experiences (detection) rather than higher-level experiences (identification). However, previous results are mixed and have several limitations. In the present study, the stimulus was a ring with a Gabor patch tilting either left or right. On each trial, subjects rated their awareness on a three-level perceptual awareness scale that captured both detection (something vs. nothing) and identification (identification vs. something). Separate staircases were used to adjust stimulus opacity to the detection threshold and the identification threshold. Bayesian linear mixed models provided extreme evidence (BF10 = 131) that VAN was stronger at the detection threshold than at the identification threshold. Mean VAN decreased from -2.12 microV [-2.86, -1.42] at detection to -0.46 microV [-0.79, -0.11] at identification. These results strongly support the claim that VAN is an NCC of lower-level experiences of seeing something rather than of higher-level experiences of specific properties of the stimuli. Thus, results are consistent with recurrent processing theory in that phenomenal visual consciousness is reflected by VAN. Further, results emphasize that it is important to consider the level of experience when searching for NCC.

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• Effects of selective attention on the C1 ERP component: A systematic review and meta-analysis

  2022. Nan Qin (et al.). Psychophysiology 59 (12)

  Artikel

  The C1 event-related potential (ERP) captures the earliest stage of feedforward processing in the primary visual cortex (V1). An ongoing debate is whether top-down selective attention can modulate the C1. One side of the debate pointed out that null findings appear to outnumber positive findings; thus, selective attention does not seem to influence the C1. However, this suggestion is not based on a valid approach to summarizing evidence across studies. Therefore, we conducted a systematic review and meta-analysis investigating the effects of selective attention on the C1, involving 47 experiments and 794 subjects in total. Despite heterogeneity across studies, results suggested that attention has a moderate effect on the C1 (Cohen's $$ d_z= 0.33, p < .0001); that is, C1 amplitude is larger for visual stimuli that are attended than unattended. These results suggest that C1 is affected by top-down selective attention.

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• Electrophysiological correlates of in vivo and virtual reality exposure therapy in spider phobia

  2022. Stefan Wiens (et al.). Psychophysiology 59 (12)

  Artikel

  Specific phobia can be treated successfully with exposure therapy. Although exposure therapy has strong effects on self-reported ratings and behavioral avoidance, effects on measures derived from electroencephalography (EEG) are scant and unclear. To fill this gap, spider-phobic individuals received either in-vivo or virtual reality exposure treatment. Patients were tested twice (one week before and after treatment), and control subjects once. In each session, EEG was recorded to spider pictures as well as other positive, negative, and neutral pictures. During EEG recording, participants performed a simple detection task while task-irrelevant pictures were shown in the background. The task was used to reduce potential confounding effects from shifts of attention. After the task, subjects were shown the pictures again and rated each in terms of their emotional reaction (arousal and pleasantness). The results showed that before treatment, patients rated spiders as more negative than did control subjects. Patients also showed elevated early posterior negativity (EPN) and late positive potential (LPP) to spiders. After treatment, the negative emotional ratings of spiders were substantially reduced. Critically, Bayesian analyses suggested that EPN and LPP were unaffected by treatment and that the treatment groups did not differ in their responses (EPN, LPP, and ratings). These findings suggest that the effects of in vivo and virtual reality exposure therapy are similar and that the initial stages of motivated attention (EPN and LPP) are unaffected by treatment.

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• Dissociation Between Speech and Emotion Effects in Short-Term Memory

  2021. Stefan Wiens. Meta-Psychology 5

  Artikel

  Performance in visual serial recall tasks is often impaired by irrelevant auditory distracters. The duplex-mechanism account of auditory distraction states that if the distracters provide order cues, these interfere with the processing of the order cues in the serial recall task (interference by process). In contrast, the unitary account states that distracters capture only attention on a general level (attentional distraction) without interfering specifically withorder processing. Marsh et al. (2018, Journal of Experimental Psychology-Learning Memory and Cognition, 44, 882-897) reported finding a dissociation between the effects of serial recall tasks and those of a missing-item task on the disruptive effects of speech and of emotional words, as predicted by the duplex-mechanism account. Critically, the reported analyses did not test specifically for the claimed dissociation. Therefore, I reanalyzed the Marsh et al. data and conducted the appropriate analyses. I also tested the dissociation more directly and added a Bayesian hypothesis test to measure the strength of the evidence for a dissociation. Results provided strong evidence for a dissociation (i.e., crossover interaction) between effects of speech and of emotion. Because the duplex-mechanism account predicts this dissociation between speech effects (interference by process) and emotion effects (attentionaldiversion) whereas the unitary account does not, Marsh et al.’s data support the duplex-mechanism account. However, to show that this dissociation is robust, researchers are advised to replicate this dissociation in an adversarial registered report.

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• Visual load effects on the auditory steady state responses to 20-, 40-, and 80-Hz amplitude-modulated tones

  2021. Malina Szychowska, Stefan Wiens. Physiology & Behavior 228

  Artikel

  Ignoring background sounds while focusing on a visual task is a necessary ability in everyday life. If attentional resources are shared between modalities, processing of task-irrelevant auditory information should become attenuated when attentional capacity is exhausted by visual demands. According to earlyfilter theory, top-down attenuation of auditory responses is possible at various stages of the auditory pathway through multiple recurrent loops. Furthermore, the adaptive filtering model of selective attention suggests that filtering occurs early when concurrent visual tasks are demanding (e.g., high load) and late when tasks are easy (e.g., low load). This study examined effects of visual load on auditory steady state responses (ASSRs) to determine where in the auditory pathway the filtering occurs. Subjects performed a visual task with three levels of load (no, low, and high) while ignoring task-irrelevant sounds. The auditory stimuli were 500-Hz tones amplitude-modulated at 20 Hz, 40 Hz, or 80 Hz to target different processing stages of the auditory pathway. Results from bayesian analyses suggest that ASSRs are unaffected by visual load. These findings also suggest that attentional resources are modality specific and that the attentional filter of auditory processing does not vary with visual task demands.

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• The early but not the late neural correlate of auditory awareness reflects lateralized experiences

  2021. Rasmus Eklund, Billy Gerdfeldter, Stefan Wiens. Neuropsychologia 158

  Artikel

  Theories disagree as to whether it is the early or the late neural correlate of awareness that plays a critical role in phenomenal awareness. According to recurrent processing theory, early activity in primary sensory areas corresponds closely to phenomenal awareness. In support, research with electroencephalography found that in the visual and somatosensory modality, an early neural correlate of awareness is contralateral to the perceived side of stimulation. Thus, early activity is sensitive to the perceived side of visual and somatosensory stimulation. Critically, it is unresolved whether this is true also for hearing. In the present study (N = 26 students), Bayesian analyses showed that the early neural correlate of awareness (auditory awareness negativity, AAN) was stronger for contralateral than ipsilateral electrodes whereas the late correlate of auditory awareness (late positivity, LP) was not lateralized. These findings demonstrate that the early but not the late neural correlate of auditory awareness reflects lateralized experiences. Thus, these findings imply that AAN is a more suitable NCC than LP because it correlates more closely with lateralized experiences.

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• Visual load does not decrease the auditory steady‐state response to 40‐Hz amplitude‐modulated tones

  2020. Malina Szychowska, Stefan Wiens. Psychophysiology 57 (12)

  Artikel

  The auditory pathway consists of multiple recurrent loops of afferent and efferent connections that extend from the cochlea up to the prefrontal cortex. The early-filter theory proposes that these loops allow topdown filtering of early and middle latency auditory responses. Furthermore, the adaptive filtering model suggests that filtering of irrelevant auditory stimuli should start lower in the pathway during more demanding tasks. If so, the 40-Hz auditory steady state responses (ASSRs) to irrelevant sounds should be affected by top-down crossmodal attention to a visual task, and effects should vary with the load of the visual task. Because few studies have examined this possibility, we conducted two preregistered studies that manipulated visual load (Study 1: N = 43, Study 2: N = 45). Study 1 used two levels (low and high), and Study 2 used four levels (no, low, high, and very high). Subjects were asked to ignore a 500-Hz taskirrelevant tone that was amplitude-modulated to evoke 40-Hz ASSRs. Results from Bayesian analyses provided moderate to extreme support for no effect of load (or of task) on ASSRs. Results also supported no interaction with time (i.e., over blocks, over minutes, or with changes in ASSRs that were synchronized with the onset of the visual stimuli). Further, results provided moderate support for no correlation between effects of load and working memory capacity. Because the present findings support the robustness of ASSRs against manipulations of crossmodal attention, they are not consistent with the adaptive filtering model.

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• Is auditory awareness negativity confounded by performance?

  2020. Rasmus Eklund, Billy Gerdfeldter, Stefan Wiens. Consciousness and Cognition 83

  Artikel

  Research suggests that the electrophysiological correlates of consciousness are similar in hearing as in vision: the auditory awareness negativity (AAN) and the late positivity (LP). However, from a recently proposed signal-detection perspective, these correlates may be confounded by performance, as the strength of the internal responses differs between aware and unaware trials. Here, we tried to apply this signal-detection approach to correct for performance in an auditory discrimination and detection task (N = 28). A large proportion of subjects had to be excluded because even a small response bias distorted the correction. For the remaining subjects, the correction mainly increased noise in the measurement. Furthermore, the signal-detection approach is theoretically problematic because it may isolate post-perceptual processes and eliminate awareness-related activity. Therefore, we conclude that AAN and LP are not confounded by performance and that the contrastive analysis identifies both as correlates of awareness.

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• Auditory awareness negativity is an electrophysiological correlate of awareness in an auditory threshold task

  2019. Rasmus Eklund, Stefan Wiens. Consciousness and Cognition 71, 70-78

  Artikel

  One theory of visual awareness proposes that electrophysiological activity related to awareness occurs in primary visual areas approximately 200 ms after stimulus onset (visual awareness negativity: VAN) and in fronto-parietal areas about 300 ms after stimulus onset (late positivity: LP). Although similar processes might be involved in auditory awareness, only sparse evidence exists for this idea. In the present study, we recorded electrophysiological activity while subjects listened to tones that were presented at their own awareness threshold. The difference in electrophysiological activity elicited by tones that subjects reported being aware of versus unaware of showed an early negativity about 200 ms and a late positivity about 300 ms after stimulus onset. These results closely match those found in vision and provide convincing evidence for an early negativity (auditory awareness negativity: AAN), as well as an LP. These findings suggest that theories of visual awareness are also applicable to auditory awareness.

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• Effects of a Manual Response Requirement on Early and Late Correlates of Auditory Awareness

  2019. Rasmus Eklund, Billy Gerdfeldter, Stefan Wiens. Frontiers in Psychology 10

  Artikel

  In hearing, two neural correlates of awareness are the auditory awareness negativity (AAN) and the late positivity (LP). These correlates of auditory awareness are typically observed with tasks in which subjects are required to report their awareness with manual responses. Thus, the correlates may be confounded by this manual response requirement. We manipulated the response requirement in a tone detection task (N = 52). Tones were presented at each subject’s individual awareness threshold while high-density electroencephalography (EEG) activity was recorded. In one response condition, subjects pushed a button if they were aware of the tone and withheld responding if they were unaware of the tone. In the other condition, subjects pushed a button if they were unaware of the tone and withheld responding if they were aware of the tone. To capture AAN and LP, difference waves were computed between aware and unaware trials, separately for trials in which responses were required and trials in which responses were not required. Results suggest that AAN and LP are unaffected by the response requirement. These findings imply that in hearing, early and late correlates of awareness are not confounded by a manual response requirement. Furthermore, the results suggest that AAN originates from bilateral auditory cortices, supporting the view that AAN is a neural correlate of localized recurrent processing in early sensory areas.

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• Visual Perceptual Load Does Not Affect the Frequency Mismatch Negativity

  2019. Stefan Wiens (et al.). Frontiers in Psychology 10

  Artikel

  The mismatch negativity (MMN) has been of particular interest in auditory perception because of its sensitivity to auditory change. It is typically measured in an oddball task and is computed as the difference of deviant minus standard tones. Previous studies suggest that the oddball MMN can be reduced by crossmodal attention to a concurrent, difficult visual task. However, more recent studies did not replicate this effect. Because previous findings seem to be biased, we preregistered the present study and used Bayesian hypothesis testing to measure the strength of evidence for or against an effect of visual task difficulty. We manipulated visual perceptual load (high and low load). In the task, the visual stimuli were identical for both loads to avoid confounding effects from physical differences of the visual stimuli. We also measured the corrected MMN because the oddball MMN may be confounded by physical differences between deviant and standard tones. The corrected MMN is obtained with a separate control condition in which the same tone as the deviant (critical tone) is equiprobable with other tones. The corrected MMN is computed as deviant minus critical tones. Furthermore, we assessed working memory capacity to examine its moderating role. In our large sample (N = 49), the evidential strength in support of no effect of visual load was moderate for the oddball MMN (9.09 > BF01 > 3.57) and anecdotal to moderate for the corrected MMN (4.55 > BF01 > 2.17). Also, working memory capacity did not correlate with the visual load effect on the oddball MMN and the corrected MMN. The present findings support the robustness of the auditory frequency MMN to manipulations of crossmodal, visual attention and suggest that this relationship is not moderated by working memory capacity.

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• Cascade and no-repetition rules are comparable controls for the auditory frequency mismatch negativity in oddball tasks

  2019. Stefan Wiens (et al.). Psychophysiology 56 (1)

  Artikel

  The mismatch negativity (MMN) has been widely studied with oddball tasks to index processing of unexpected auditory change. The MMN is computed as the difference of deviant minus standard and is used to capture the pattern violation by the deviant. However, this oddball MMN is confounded because the deviant differs physically from the standard and is presented less often. To improve measurement, the same tone as the deviant is presented in a separate condition. This control tone is equiprobable with other tones and is used to compute a corrected MMN (deviant minus control). Typically, the tones are in random order except that consecutive tones are not identical (no-repetition rule). In contrast, a recent study on frequency MMN presented tones in a regular up-and-down sequence (cascade rule). If the cascade rule is detected more easily than the no-repetition rule, there should be a lower risk of a confounding MMN within the cascade condition. However, in previous research, the cascade and no-repetition conditions differed not only in the regularity of the tone sequence but also in number of tones, frequency range, and proportion of tones. We controlled for these differences to isolate effects of regularity in the tone sequence. Results of our preregistered analyses provided moderate evidence (BF01>6) that the corrected MMN did not differ between cascade and no-repetition conditions. These findings imply that no-repetition and cascade rules are processed similarly and that the no-repetition condition provides an adequate control in frequency MMN.

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• Visual awareness negativity is an early neural correlate of awareness

  2018. Rasmus Eklund, Stefan Wiens. Cognitive, Affective, & Behavioral Neuroscience 18 (1), 176-188

  Artikel

  Electrophysiological recordings are commonly used to study the neural correlates of consciousness in humans. Previous research is inconsistent as to whether awareness can be indexed with visual awareness negativity (VAN) at about 200 ms or if it occurs later. The present study was preregistered with two main aims: First, to provide independent evidence for or against the presence of VAN, and second, to study whether stimulus size may account for the inconsistent findings. Subjects were shown low-contrast Gaussian filtered gratings (Gabor patches) in the four visual quadrants. Gabor size (large and small) was varied in different sessions and calibrated to each subject’s threshold of visual awareness. Event-related potentials were derived from trials in which subjects localized the Gabors correctly to capture the difference between trials in which they reported awareness versus no awareness. Bayesian analyses revealed very strong evidence for the presence of VAN for both Gabor sizes. However, there was no evidence for or against an effect of stimulus size. The present findings provide evidence for VAN as an early neural correlate of awareness.

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