Can Inexperienced Listeners Hear Who Is Singing? The Role of Motivation in Singer Discrimination Across Pitch.

OBJECTIVE: Previous research has shown that in a task identifying singers across pitch, inexperienced listeners perform very poorly compared to their experienced counterparts. This poor performance may partially be due to lower motivation and reduced attention on the part of inexperienced listeners. The current experiment is designed to examine the role of motivation in difficult perceptual tasks through use of an established methodology that uses singing voice stimuli. METHODS: This study used an ABX paradigm. Listeners heard two different singers, singing /ɑ/ at the same pitch and had to identify which of the two singers produced a third /ɑ/ at a different pitch. Pitches varied across 1.5 octaves. Inexperienced listeners were randomly assigned to 1 of 3 conditions: (1) no feedback, (2) percent correct feedback, and (3) percentile feedback. Prior to the experiment, listeners rated their motivation using the Situational Intrinsic Motivation Scale (SIMS). Data were collected from 99 inexperienced listeners. RESULTS: There were no significant differences between the three feedback conditions, No Feedback, Percent Correct, and Percentile, for any SIMS subscale. Likewise, there were no significant differences in musical experience between the three feedback conditions. A repeated measures ANOVA designed to test the effect of feedback group on mean percent correct responses revealed no significant main or interaction effects of feedback. However, amotivation was a significant predictor of mean percent correct scores. CONCLUSIONS: Motivation is a complex construct that, while not being a primary factor in the current audio-perceptual task, could still be an important confounding factor in perceptual research. In the case of the current study, the two feedback conditions utilized in this study, Percent Correct and Percentile, may not have provided sufficiently robust external motivation to elicit differences in performance. Perceptual and behavioral researchers should be vigilant. More research is necessary.

Assessing Trial-by-Trial Electrophysiological and Behavioral Markers of Attentional Control and Sensory Precision in Psychotic and Mood Disorders.

BACKGROUND AND HYPOTHESIS: The current study investigated the extent to which changes in attentional control contribute to performance on a visual perceptual discrimination task, on a trial-by-trial basis in a transdiagnostic clinical sample. STUDY DESIGN: Participants with schizophrenia (SZ; N = 58), bipolar disorder (N = 42), major depression disorder (N = 51), and psychiatrically healthy controls (N = 92) completed a visual perception task in which stimuli appeared briefly. The design allowed us to estimate the lapse rate and the precision of perceptual representations of the stimuli. Electroencephalograms (EEG) were recorded to examine pre-stimulus activity in the alpha band (8-13 Hz), overall and in relation to behavior performance on the task. STUDY RESULTS: We found that the attention lapse rate was elevated in the SZ group compared with all other groups. We also observed group differences in pre-stimulus alpha activity, with control participants showing the highest levels of pre-stimulus alpha when averaging across trials. However, trial-by-trial analyses showed within-participant fluctuations in pre-stimulus alpha activity significantly predicted the likelihood of making an error, in all groups. Interestingly, our analysis demonstrated that aperiodic contributions to the EEG signal (which affect power estimates across frequency bands) serve as a significant predictor of behavior as well. CONCLUSIONS: These results confirm the elevated attention lapse rate that has been observed in SZ, validate pre-stimulus EEG markers of attentional control and their use as a predictor of behavior on a trial-by-trial basis, and suggest that aperiodic contributions to the EEG signal are an important target for further research in this area, in addition to alpha-band activity.

Experienced and Inexperienced Listeners' Perception of Vocal Strain.

OBJECTIVE: The ability to perceive strain or tension in a voice is critical for both speech-language pathologists and singing teachers. Research on voice quality has focused primarily on the perception of breathiness or roughness. The perception of vocal strain has not been extensively researched and is poorly understood. METHODS/DESIGN: This study employs a group and a within-subject design. Synthetic female sung stimuli were created that varied in source slope and vocal tract transfer function. Two groups of listeners, inexperienced listeners and experienced vocal pedagogues, listened to the stimuli and rated the perceived strain using a visual analog scale Synthetic female stimuli were constructed on the vowel /ɑ/ at 2 pitches, A3 and F5, using glottal source slopes that drop in amplitude at constant rates varying from - 6 dB/octave to - 18 dB/octave. All stimuli were filtered using three vocal tract transfer functions, one derived from a lyric/coloratura soprano, one derived from a mezzo-soprano, and a third that has resonance frequencies mid-way between the two. Listeners heard the stimuli over headphones and rated them on a scale from "no strain" to "very strained" using a visual-analog scale. RESULTS: Spectral source slope was strongly related to the perception of strain in both groups of listeners. Experienced listeners' perception of strain was also related to formant pattern, while inexperienced listeners' perception of strain was also related to pitch. CONCLUSION: This study has shown that spectral source slope can be a powerful cue to the perception of strain. However, inexperienced and experienced listeners also differ from each other in how strain is perceived across speaking and singing pitches. These differences may be based on both experience and the goals of the listener.

A Transdiagnostic Study of Effort-Cost Decision-Making in Psychotic and Mood Disorders.

BACKGROUND: Research suggests that effort-cost decision-making (ECDM), the estimation of work required to obtain reward, may be a relevant framework for understanding motivational impairment in psychotic and mood pathology. Specifically, research has suggested that people with psychotic and mood pathology experience effort as more costly than controls, and thus pursue effortful goals less frequently. This study examined ECDM across psychotic and mood pathology. HYPOTHESIS: We hypothesized that patient groups would show reduced willingness to expend effort compared to controls. STUDY DESIGN: People with schizophrenia (N = 33), schizoaffective disorder (N = 28), bipolar disorder (N = 39), major depressive disorder (N = 40), and controls (N = 70) completed a physical ECDM task. Participants decided between completing a low-effort or high-effort option for small or larger rewards, respectively. Reward magnitude, reward probability, and effort magnitude varied trial-by-trial. Data were analyzed using standard and hierarchical logistic regression analyses to assess the subject-specific contribution of various factors to choice. Negative symptoms were measured with a clinician-rated interview. STUDY RESULTS: There was a significant effect of group, driven by reduced choice of high-effort options in schizophrenia. Hierarchical logistic regression revealed that reduced choice of high-effort options in schizophrenia was driven by weaker contributions of probability information. Use of reward information was inversely associated with motivational impairment in schizophrenia. Surprisingly, individuals with major depressive disorder and bipolar disorder did not differ from controls. CONCLUSIONS: Our results provide support for ECDM deficits in schizophrenia. Additionally, differences between groups in ECDM suggest a seemingly similar behavioral phenotype, reduced motivation, could arise from disparate mechanisms.

Experienced Listeners' Perception of Timbre Dissimilarity Within and Between Voice Categories.

OBJECTIVE/HYPOTHESES: The terms "soprano" and "mezzo-soprano" are frequently used by vocal pedagogues to describe a main category of singing timbre categorization, while the terms "lyric" and "dramatic" are often used to describe sub-categories of "soprano" and "mezzo-soprano". A handful of studies have reported on the perceptual dissimilarity of main voice categories, but few, if any, have focused on within voice category perceptual distinctions such as dramatic and lyric vocal timbre. Using stimuli collected from cisgender female singers of varying voice categories and voice weights across the pitches C4, G4, and F5, this study sought (1) to visualize an experienced listener's perception of vocal timbre dissimilarity within and between voice categories using the statistical technique of multidimensional scaling (MDS), (2) to identify salient acoustic predictors of voice category and voice weight, and (3) to determine any dependencies on pitch for the perception of vocal timbre. METHOD/DESIGN: For the pitches C4, G4, and F5, experienced listeners (N=18) rated the dissimilarity of pairs of sung vowels produced by classically trained singers classified as follows: six mezzo-sopranos (three lighter and three heavier) and six sopranos (three lighter and three heavier). The resulting dissimilarity data were analyzed using MDS. Backward linear regression was used to see if one or more of the following variables predicted MDS dimensions: spectral centroid from 0 to 5 kHz, spectral centroid from 0 to 2 kHz, spectral centroid from 2 to 5 kHz, frequency vibrato rate, and frequency vibrato extent. Listeners also completed a categorization task where they rated each individual stimulus on two dimensions: voice category and voice weight. RESULTS: Visual analysis of the MDS solutions appears to show that both voice category and voice weight emerged as dimensions at pitches C4 and G4. Discriminant analysis, on the other hand, statistically confirmed both these dimensions at G4, but only voice weight at C4. At pitch F5, only voice weight emerged as a dimension, both visually and statistically. Acoustic predictors of MDS dimensions were highly variable across pitches. At the pitch C4, no MDS dimension was predicted by the acoustic variables. At pitch G4, the dimension associated with voice weight was predicted by spectral centroid from 0 to 2 kHz. At pitch F5, the dimension associated with voice weight was predicted by spectral centroid from 2 to 5 kHz and frequency vibrato rate. In the categorization task, voice category and voice weight were highly correlated at the pitches C4, G4, and when all pitches were presented together, but weakly correlated at the pitch F5. CONCLUSION: While voice category and sub-category distinctions are commonly used by singing voice professionals to describe the overall timbre of voices, these distinctions may not be able to consistently predict the perceptual difference between any given pair of vocal stimuli, particularly across pitch. Nonetheless, these dimensions do emerge in some fashion when listeners are presented with paired vocal stimuli. On the other hand, when asked to rate stimuli according to the specific labels of mezzo-soprano/soprano and dramatic/lyric, experienced listeners have a very difficult time disentangling voice category from voice weight when presented with a single-note stimulus or even a 3-note stimulus consisting of the pitches C3, G4, and F5.

Managing EEG studies: How to prepare and what to do once data collection has begun.

In this paper, we provide guidance for the organization and implementation of EEG studies. This work was inspired by our experience conducting a large-scale, multi-site study, but many elements could be applied to any EEG project. Section 1 focuses on study activities that take place before data collection begins. Topics covered include: establishing and training study teams, considerations for task design and piloting, setting up equipment and software, development of formal protocol documents, and planning communication strategy with all study team members. Section 2 focuses on what to do once data collection has already begun. Topics covered include: (1) how to effectively monitor and maintain EEG data quality, (2) how to ensure consistent implementation of experimental protocols, and (3) how to develop rigorous preprocessing procedures that are feasible for use in a large-scale study. Links to resources are also provided, including sample protocols, sample equipment and software tracking forms, sample code, and tutorial videos (to access resources, please visit: https://osf.io/wdrj3/).

Phenomenological and Cognitive Features Associated With Auditory Hallucinations in Clinical and Nonclinical Voice Hearers.

BACKGROUND AND HYPOTHESES: Auditory verbal hallucinations (AVH) are central features of schizophrenia (SZ). However, AVH also occur in a small percentage of the general population who do not have a need for care, termed nonclinical voice hearers (NCVH). We sought to determine the degree to which the experience of AVH was similar in NCVH and in people with schizophrenia (PSZ) and evaluate the degree to which NCVH shared other features of SZ such as delusional beliefs, cognitive impairment, and negative symptoms. STUDY DESIGN: We recruited 76 people with a DSM-V diagnosis of SZ/schizoaffective disorder (PSZ; 49 with current AVH, 27 without), 48 NCVH, and 51 healthy controls. Participants received a broad battery of clinician-administered and self-report symptom assessments and a focused cognitive assessment. STUDY RESULTS: The AVH of NCVH and PSZ shared very similar sensory features. NCVH experienced less distress, had greater control over their AVH, and, unlike PSZ, rarely heard 2 voices speaking to each other. NCVH demonstrated a wide range of deeply held unusual beliefs, but reported less paranoia, and fewer first-rank symptoms such as passivity and alterations in self-experience. NCVH showed no evidence of cognitive deficits or negative symptoms. CONCLUSIONS: The AVH in NCVH and PSZ demonstrate important similarities as well as clear differences. Specific features, rather than the presence, of AVH appear to determine the need for care. NCVH do not share the cognitive and motivational deficits seen in PSZ. These results suggest that AVH and unusual beliefs can be separated from the broader phenotype of SZ.

Cognitive [Computational] Neuroscience Test Reliability and Clinical Applications for Serious Mental Illness (CNTRaCS) Consortium: Progress and Future Directions.

The development of treatments for impaired cognition in schizophrenia has been characterized as the most important challenge facing psychiatry at the beginning of the twenty-first century. The Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) project was designed to build on the potential benefits of using tasks and tools from cognitive neuroscience to better understanding and treat cognitive impairments in psychosis. These benefits include: (1) the use of fine-grained tasks that measure discrete cognitive processes; (2) the ability to design tasks that distinguish between specific cognitive domain deficits and poor performance due to generalized deficits resulting from sedation, low motivation, poor test taking skills, etc.; and (3) the ability to link cognitive deficits to specific neural systems, using animal models, neuropsychology, and functional imaging. CNTRICS convened a series of meetings to identify paradigms from cognitive neuroscience that maximize these benefits and identified the steps need for translation into use in clinical populations. The Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia (CNTRaCS) Consortium was developed to help carry out these steps. CNTRaCS consists of investigators at five different sites across the country with diverse expertise relevant to a wide range of the cognitive systems identified as critical as part of CNTRICs. This work reports on the progress and current directions in the evaluation and optimization carried out by CNTRaCS of the tasks identified as part of the original CNTRICs process, as well as subsequent extensions into the Positive Valence systems domain of Research Domain Criteria (RDoC). We also describe the current focus of CNTRaCS, which involves taking a computational psychiatry approach to measuring cognitive and motivational function across the spectrum of psychosis. Specifically, the current iteration of CNTRaCS is using computational modeling to isolate parameters reflecting potentially more specific cognitive and visual processes that may provide greater interpretability in understanding shared and distinct impairments across psychiatric disorders.

Gamma-band entrainment abnormalities in schizophrenia: Modality-specific or cortex-wide impairment?

A growing body of literature suggests that cognitive impairment in people with schizophrenia (PSZ) results from disrupted cortical excitatory/inhibitory (E-I) balance, which may be linked to gamma entrainment and can be measured noninvasively using electroencephalography (EEG). However, it is not yet known the degree to which these entrainment abnormalities covary within subjects across sensory modalities. Furthermore, the degree to which cross-modal gamma entrainment reflects variation in biological processes associated with cognitive performance remains unclear. We used EEG to measure entrainment to repetitive auditory and visual stimulation at beta (20 Hz) and gamma (30 and 40 Hz) frequencies in PSZ (n = 78) and healthy control subjects (HCS; n = 80). Three indices were measured for each frequency and modality: event-related spectral perturbation (ERSP), intertrial coherence (ITC), and phase-lag angle (PLA). Cognition and symptom severity were also assessed. We found little evidence that gamma entrainment covaried across sensory modalities. PSZ exhibited a modest correlation between modalities at 40 Hz for ERSP and ITC measures (r = 0.23-0.24); however, no other significant correlations between modalities emerged for either HCS or PSZ. Both univariate and multivariate analyses revealed that (a) the pattern of entrainment abnormalities in PSZ differed across modalities, and (b) modality rather than frequency band was the main source of variance. Finally, we observed a significant association between cognition and gamma entrainment in the auditory domain only in HCS. Gamma-band EEG entrainment does not reflect a unitary transcortical mechanism but is instead modality specific. To the extent that entrainment reflects the integrity of cortical E-I balance, the deficits observed in PSZ appear to be modality specific and not consistently associated with cognitive impairment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Is Cortical Theta-Gamma Phase-Amplitude Coupling Memory-Specific?

One of the proposed neural mechanisms involved in working memory is coupling between the theta phase and gamma amplitude. For example, evidence from intracranial recordings shows that coupling between hippocampal theta and cortical gamma oscillations increases selectively during working memory tasks. Theta-gamma phase-amplitude coupling can also be measured non-invasively through scalp EEG; however, EEG can only assess coupling within cortical areas, and it is not yet clear if this cortical-only coupling is truly memory-specific, or a more general phenomenon. We tested this directly by measuring cortical coupling during three different conditions: a working memory task, an attention task, and a passive perception condition. We find similar levels of theta-gamma coupling in all three conditions, suggesting that cortical theta-gamma phase-amplitude coupling is not a memory-specific signal, but instead reflects some other attentional or perceptual processes. Implications for understanding the brain dynamics of visual working memory are discussed.

Relating Glutamate, Conditioned, and Clinical Hallucinations via 1H-MR Spectroscopy.

BACKGROUND AND HYPOTHESIS: Hallucinations may be driven by an excessive influence of prior expectations on current experience. Initial work has supported that contention and implicated the anterior insula in the weighting of prior beliefs. STUDY DESIGN: Here we induce hallucinated tones by associating tones with the presentation of a visual cue. We find that people with schizophrenia who hear voices are more prone to the effect and using computational modeling we show they overweight their prior beliefs. In the same participants, we also measured glutamate levels in anterior insula, anterior cingulate, dorsolateral prefrontal, and auditory cortices, using magnetic resonance spectroscopy. STUDY RESULTS: We found a negative relationship between prior-overweighting and glutamate levels in the insula that was not present for any of the other voxels or parameters. CONCLUSIONS: Through computational psychiatry, we bridge a pathophysiological theory of psychosis (glutamate hypofunction) with a cognitive model of hallucinations (prior-overweighting) with implications for the development of new treatments for hallucinations.

Association Between Failures in Perceptual Updating and the Severity of Psychosis in Schizophrenia.

Importance: Recent accounts suggest that delusions and hallucinations may result from alterations in how prior knowledge is integrated with new information, but experimental evidence supporting this idea has been complex and inconsistent. Evidence from a simpler perceptual task would make clear whether psychotic symptoms are associated with overreliance on prior information and impaired updating. Objective: To investigate whether individuals with schizophrenia or schizoaffective disorder (PSZ) and healthy control individuals (HCs) differ in the ability to update their beliefs based on evidence in a relatively simple perceptual paradigm. Design, Setting, and Participants: This case-control study included individuals who met DSM-IV criteria for PSZ and matched HC participants in 2 independent samples. The PSZ group was recruited from the Maryland Psychiatric Research Center, Yale University, and community clinics, and the HC group was recruited from the community. To test perceptual updating, a random dot kinematogram paradigm was implemented in which dots moving coherently in a single direction were mixed with randomly moving dots. On 50% of trials, the direction of coherent motion changed by 90° midway through the trial. Participants were asked to report the direction perceived at the end of the trial. The Peters Delusions Inventory and Brief Psychiatric Rating Scale (BPRS) were used to quantify the severity of positive symptoms. Data were collected from September 2018 to March 2020 and were analyzed from approximately March 2020 to March 2021. Main Outcomes and Measures: Critical measures included the proportion of responses centered around the initial direction vs the subsequent changed direction and the overall precision of motion perception and reaction times. Results: A total of 48 participants were included in the PSZ group (31 [65%] male; mean [SD] age, 36.56 [9.76] years) and 36 in the HC group (22 [61%] male; mean [SD] age, 35.67 [10.74] years) in the original sample. An independent replication sample included 42 participants in the PSZ group (29 [69%] male; mean [SD] age, 33.98 [11.03] years) and 34 in the HC group (20 [59%] male; mean [SD] age, 34.29 [10.44] years). In line with previous research, patients with PSZ were less precise and had slower reaction times overall. The key finding was that patients with PSZ were significantly more likely (original sample: mean, 27.88 [95% CI, 24.19-31.57]; replication sample: mean, 26.70 [95% CI, 23.53-29.87]) than HC participants (original sample: mean, 18.86 [95% CI, 16.56-21.16]; replication sample: mean, 15.67 [95% CI, 12.61-18.73]) to report the initial motion direction rather than the final one. Moreover, the tendency to report the direction of initial motion correlated with the degree of conviction on the Peters Delusions Inventory (original sample: r = 0.32 [P = .05]; replication sample: r = 0.30 [P = .05]) and the Brief Psychiatric Rating Scale Reality Distortion score (original sample: r = 0.55 [P = .001]; replication sample: r = 0.35 [P = .03]) and severity of hallucinations (original sample: r = 0.39 [P = .02]; replication sample: r = 0.30 [P = .05]). Conclusions and Relevance: The findings of this case-control study suggest that the severity of psychotic symptoms is associated with a tendency to overweight initial information over incoming sensory evidence. These results are consistent with predictive coding accounts of the origins of positive symptoms and suggest that deficits in very elementary perceptual updating may be a critical mechanism in psychosis.

Neural basis of the visual working memory deficit in schizophrenia: Merging evidence from fMRI and EEG.

Although people with schizophrenia (PSZ) exhibit robust and reliable deficits in working memory (WM) capacity, the neural processes that give rise to this impairment remain poorly understood. One reason for this lack of clarity is that most studies employ a single neural recording modality-each with strengths and weaknesses-with few examples of integrating results across modalities. To address this gap, we conducted a secondary analysis that combined data from an overlapping set of subjects in previously published electroencephalographic and functional magnetic resonance imaging studies that used nearly identical working memory tasks (visual change detection). The prior studies found similar patterns of results for both posterior parietal BOLD activation and suppression of the alpha frequency band within the EEG. Specifically, both signals exhibited abnormally shallow modulation as a function of the amount of information being stored in WM in PSZ. In the present study, both alpha suppression and posterior parietal BOLD activity increased as the number of items stored in WM increased. The magnitude of alpha suppression modulation was correlated with the magnitude of BOLD signal modulation in PSZ, but not in HCS. This finding suggests that the same illness-related biological processes constrain both alpha suppression and BOLD signal modulation as a function of WM storage in PSZ. The complementary strengths of these two techniques may thus combine to advance the identification of the processes underlying WM deficits in PSZ.

Absence of Excess Intra-Individual Variability in Retinal Function in People With Schizophrenia.

People with schizophrenia exhibit increased intra-individual variability in both behavioral and neural signatures of cognition. Examination of intra-individual variability may uncover a unique functionally relevant aspect of impairment that is not captured by typical between-group comparisons of mean or median values. We and others have observed that retinal activity measured using electroretinography (ERG) is significantly reduced in people with schizophrenia; however, it is currently unclear whether greater intra-individual variability in the retinal response can also be observed. To investigate this, we examined intra-individual variability from 25 individuals with schizophrenia and 24 healthy controls under two fERG conditions: (1) a light-adapted condition in which schizophrenia patients demonstrated reduced amplitudes; and (2) a dark-adapted condition in which the groups did not differ in amplitudes. Intraclass correlation coefficients (ICC) were generated to measure intra-individual variability for each subject, reflecting the consistency of activation values (in µv) across all sampling points (at a 2 kHz sampling rate) within all trials within a condition. Contrary to our predictions, results indicated that the schizophrenia and healthy control groups did not differ in intra-individual variability in fERG responses in either the light- or dark-adapted conditions. This finding remained consistent when variability was calculated as the standard deviation (SD) and coefficient of variation (CV) of maximum positive and negative microvolt values within the a- and b-wave time windows. This suggests that although elevated variability in schizophrenia may be observed at perceptual and cognitive levels of processing, it is not present in the earliest stages of sensory processing in vision.

Multidimensional Timbre Spaces of Cochlear Implant Vocoded and Non-vocoded Synthetic Female Singing Voices.

Many post-lingually deafened cochlear implant (CI) users report that they no longer enjoy listening to music, which could possibly contribute to a perceived reduction in quality of life. One aspect of music perception, vocal timbre perception, may be difficult for CI users because they may not be able to use the same timbral cues available to normal hearing listeners. Vocal tract resonance frequencies have been shown to provide perceptual cues to voice categories such as baritone, tenor, mezzo-soprano, and soprano, while changes in glottal source spectral slope are believed to be related to perception of vocal quality dimensions such as fluty vs. brassy. As a first step toward understanding vocal timbre perception in CI users, we employed an 8-channel noise-band vocoder to test how vocoding can alter the timbral perception of female synthetic sung vowels across pitches. Non-vocoded and vocoded stimuli were synthesized with vibrato using 3 excitation source spectral slopes and 3 vocal tract transfer functions (mezzo-soprano, intermediate, soprano) at the pitches C4, B4, and F5. Six multi-dimensional scaling experiments were conducted: C4 not vocoded, C4 vocoded, B4 not vocoded, B4 vocoded, F5 not vocoded, and F5 vocoded. At the pitch C4, for both non-vocoded and vocoded conditions, dimension 1 grouped stimuli according to voice category and was most strongly predicted by spectral centroid from 0 to 2 kHz. While dimension 2 grouped stimuli according to excitation source spectral slope, it was organized slightly differently and predicted by different acoustic parameters in the non-vocoded and vocoded conditions. For pitches B4 and F5 spectral centroid from 0 to 2 kHz most strongly predicted dimension 1. However, while dimension 1 separated all 3 voice categories in the vocoded condition, dimension 1 only separated the soprano stimuli from the intermediate and mezzo-soprano stimuli in the non-vocoded condition. While it is unclear how these results predict timbre perception in CI listeners, in general, these results suggest that perhaps some aspects of vocal timbre may remain.

Can Listeners Hear Who Is Singing? The Role of Listener Experience in Singer Discrimination Across Pitch.

OBJECTIVE/HYPOTHESIS: Previous research has shown that listeners are unable to identify who is singing across pitch when the voices are unfamiliar to them. Implementing a very short training period, however, greatly improves this ability, but only when the voices being compared are of different voice category. The objective of this study was to determine whether experienced listeners with highly developed knowledge of voice categories can more easily discriminate between singers across pitch. METHODS/DESIGN: This study used an ABX paradigm where listeners heard two different singers singing "ah" at the same pitch. Listeners identified which of the two singers produced a third "ah" at a different pitch. Stimuli were recorded from two baritones, two tenors, two mezzo-sopranos, and two sopranos across a 1.5 octave range. Data were collected from 42 inexperienced listeners and 27 experienced listeners. RESULTS: Experienced listeners were better at singer discrimination across pitch than were inexperienced listeners for all conditions except same-category comparisons at the interval of the third. Experienced listeners were better at singer discrimination across pitch than were slightly trained listeners for all conditions except same-category female singers at all pitch intervals. CONCLUSIONS: The ability to discriminate singers across pitch is the greatest for experienced listeners, followed by slightly trained inexperienced listeners, followed by inexperienced listeners.

Inexperienced Listeners' Perception of Timbre Dissimilarity Within and Between Voice Categories.

OBJECTIVE/HYPOTHESIS: Using stimuli produced by classically trained female singers, this study sought to examine how inexperienced listeners' ratings of timbre dissimilarity relate to singer categorization, both between and within voice category. METHOD/DESIGN: Stimuli were produced by six mezzo-sopranos and six sopranos classically trained female voice students at three pitches, C4, G4, and F5. Within each category, mezzo-soprano and soprano, three singers were classified as lighter in timbre and three were classified as heavier in timbre. At each pitch, the 12 sung stimuli were combined in all possible pairs and presented to 56 inexperienced listeners who judged each pair for the degree of timbre dissimilarity using a visual analog scale. All stimuli also were rated by expert voice professionals in two dimensions: (1) voice category and (2) vocal weight. RESULTS: Multidimensional scaling (MDS) dimensions agreed with teacher-determined voice category at C4 and teacher-determined vocal weight at G4 and F5. MDS dimensions also correlated with single-note ratings of voice category and vocal weight provided by expert listeners who were unfamiliar with the singing voices used in this study. With limited exceptions, no single acoustic variable predicted the MDS dimensions that resulted from the inexperienced listeners ratings of timbre dissimilarity; however, weighted linear combinations of acoustic variables were highly predictive of numerous MDS dimensions. CONCLUSION: In spite of a lack of both range and tessitura information, timbre dissimilarity ratings provided by inexperienced listeners yielded MDS dimensions that accurately predicted voice categories and vocal weight and that highly correlated to expert listeners ratings of these two parameters.

FRONTAL ALPHA ASYMMETRY IN YOUTH AT CLINICAL HIGH-RISK FOR PSYCHOSIS.

PURPOSE OF THE REVIEW: Negative symptoms are highly predictive of whether individuals at clinical high-risk (CHR) develop a psychotic disorder. However, little is known about pathophysiological mechanisms underlying negative symptoms during this period. The current study examined neurophysiological mechanisms underlying negative symptoms in CHR individuals using electroencephalography frontal alpha asymmetry power, a biomarker of approach and avoidance motivation. RECENT FINDINGS: People with schizophrenia display abnormal patterns of frontal alpha asymmetry indicative of reduced approach motivation. However, It is unknown whether similar abnormalities occur in CHR youth that predict negative symptoms. SUMMARY: Results indicated that CHR and healthy controls did not differ in frontal alpha asymmetry scores. However, in CHR youth, frontal alpha asymmetry was inversely correlated with the motivation and pleasure dimension of negative symptoms, which was accounted for by mood symptoms. Findings suggest that depression contributes to reduced approach motivation in CHR youth that manifests clinically as negative symptoms.

Alpha-band desynchronization reflects memory-specific processes during visual change detection.

Recent work investigating physiological mechanisms of working memory (WM) has revealed that modulation of alpha and beta frequency bands within the EEG plays a key role in WM storage. However, the nature of that role is unclear. In the present study, we examined event-related desynchronization of alpha and beta (α/ß-ERD) elicited by visual tasks with and without a memory component to measure the impact of a WM demand on this electrophysiological marker. We recorded EEG from 60 healthy participants while they completed three variants on a typical change detection task: one in which participants passively viewed the sample array, passive (WM-); one in which participants viewed and attended the sample array in search of a target color but did not memorize the colors, active (WM-); and one in which participants encoded, attended to, and memorized the sample array, active (WM+). Replicating previous findings, we found that active (WM+) elicited robust α/ß-ERD in frontal and posterior electrode clusters and that α-ERD was significantly associated with WM capacity. By contrast, α/ß-ERD was significantly smaller in the passive (WM-) and active (WM-) tasks, which did not consistently differ from one another. Furthermore, no such relationship was observed between WM capacity and desynchronization in the passive (WM-) or active (WM-) tasks. Taken together, these results suggest that α-ERD during memory formation reflects a memory-specific process such as consolidation or maintenance, rather than serving a generalized role in perceptual gating or engagement of attention.

Time and frequency dependent changes in resting state EEG functional connectivity following lipopolysaccharide challenge in rats.

Research has shown that inflammatory processes affect brain function and behavior through several neuroimmune pathways. However, high order brain functions affected by inflammation largely remain to be defined. Resting state functional connectivity of synchronized oscillatory activity is a valid approach to understand network processing and high order brain function under different experimental conditions. In the present study multi-electrode EEG recording in awake, freely moving rats was used to study resting state connectivity after administration of lipopolysaccharides (LPS). Male Wistar rats were implanted with 10 cortical surface electrodes and administered with LPS (2 mg/kg) and monitored for symptoms of sickness at 3, 6 and 24 h. Resting state connectivity and power were computed at baseline, 6 and 24 h. Three prominent connectivity bands were identified using a method resistant to spurious correlation: alpha (5-15 Hz), beta-gamma (20-80 Hz), and high frequency oscillation (150-200 Hz). The most prominent connectivity band, alpha, was strongly reduced 6 h after LPS administration, and returned to baseline at 24 h. Beta-gamma connectivity was also reduced at 6 h and remained reduced at 24 h. Interestingly, high frequency oscillation connectivity remained unchanged at 6 h and was impaired 24 h after LPS challenge. Expected elevations in delta and theta power were observed at 6 h after LPS administration, when behavioral symptoms of sickness were maximal. Notably, gamma and high frequency power were reduced 6 h after LPS and returned to baseline by 24 h, when the effects on connectivity were more evident. Finally, increases in cross-frequency coupling elicited by LPS were detected at 6 h for theta-gamma and at 24 h for theta-high frequency oscillations. These studies show that LPS challenge profoundly affects EEG connectivity across all identified bands in a time-dependent manner indicating that inflammatory processes disrupt both bottom-up and top-down communication across the cortex during the peak and resolution of inflammation.