Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 314)

This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1988

The automatic processing of non-verbal emotional vocalizations: an electrophysiological investigation

Dissertação de mestrado integrado em Psicologia (área de especialização em Psicologia Clínica e da Saúde)The human voice is a critical channel for the exchange of information about the emotionality of a speaker. In this sense, it is important to investigate the neural correlates of non-verbal vocalizations processing, even when listeners are not attending to these events. We developed an oddball paradigm in which emotional (happy and angry) and neutral vocalizations were presented both as standard and deviant stimuli in four conditions: Happy, Angry, Neutral 1 (neutral vocalizations with angry context), and Neutral 2 (neutral vocalizations with happy context). To unfold the time course of the auditory change detection mechanisms indexed by the Mismatch Negativity (MMN) component, the Event–Related Potentials (ERP) methodology was used. ERPs were recorded in 17 healthy subjects. The results showed that Happy and Neutral 2 conditions elicited more negative MMN amplitude relative to the Angry condition, at midline (Fz, Cz) electrodes. Overall results suggest that automatic auditory change detection is enhanced for positive and neutral (in happy context) vocalizations than for negative stimuli.A voz humana é um canal vital na troca de informação sobre a emocionalidade do outro. Neste sentido, é importante investigar quais os correlatos neuronais associados ao processamento de vocalizações não-verbais, mesmo quando não é alocada atenção a estes estímulos. Foi criado um paradigma oddball com vocalizações emocionais (alegria e raiva) e neutras, que eram apresentadas como estímulos frequentes ou infrequentes em quatro condições distintas: Alegre, Raiva, Neutro 1 (vocalizações neutras em contexto de raiva) e Neutro 2 (vocalizações neutras em contexto de alegria). Para investigar o curso temporal dos mecanismos automáticos de detecção de mudança auditiva, foi usada a técnica de Potenciais Evocados e estudado o componente Mismatch Negativity (MMN). A amostra foi constituída por 17 indivíduos saudáveis. Os resultados mostraram que as condições Alegre e Neutro 2 elicitaram uma amplitude de MMN mais negativa comparativamente com a condição Raiva, para os eléctrodos situados na linha média do escalpe (Fz, Cz). Estes resultados indicam que existe um mecanismo neuronal de deteção de mudança auditiva mais pronunciado para vocalizações positivas e neutras (em contexto de alegria) comparativamente com vocalizações negativas

Predicting future reading problems based on pre-reading auditory measures: a longitudinal study of children with a familial risk of dyslexia

Purpose: This longitudinal study examines measures of temporal auditory processing in pre-reading children with a family risk of dyslexia. Specifically, it attempts to ascertain whether pre-reading auditory processing, speech perception, and phonological awareness (PA) reliably predict later literacy achievement. Additionally, this study retrospectively examines the presence of pre-reading auditory processing, speech perception, and PA impairments in children later found to be literacy impaired. Method: Forty-four pre-reading children with and without a family risk of dyslexia were assessed at three time points (kindergarten, first, and second grade). Auditory processing measures of rise time (RT) discrimination and frequency modulation (FM) along with speech perception, PA, and various literacy tasks were assessed. Results: Kindergarten RT uniquely contributed to growth in literacy in grades one and two, even after controlling for letter knowledge and PA. Highly significant concurrent and predictive correlations were observed with kindergarten RT significantly predicting first grade PA. Retrospective analysis demonstrated atypical performance in RT and PA at all three time points in children who later developed literacy impairments. Conclusions: Although significant, kindergarten auditory processing contributions to later literacy growth lack the power to be considered as a single-cause predictor; thus results support temporal processing deficits’ contribution within a multiple deficit model of dyslexia

BACKWARD MASKING WITH SIMULTANEOUS EARLY, MIDDLE AND LATE EVOKED POTENTIALS

Auditory processing disorders (APDs) affect a diverse range of people. These types of disorders impair auditory function, despite the outer, middle and inner ear maintaining proper function and health. APD is not necessarily related to auditory thresholds. When people with APD have difficulty discriminating sounds in connected speech, it may be due in part to an effect called Backward Masking (BM). Masking occurs when one stimulus inhibits another, which can lead to a variety of impairments. The neural locus of APDs is for the most part unknown, including the specific conditions which cause BM. A better understanding of these processes would lead to a greater ability to provide an intervention and therapy for APD. Responses have been well documented in a forward-masking paradigm, but not so under a backward masking condition. The significances of these backward masking responses are yielded through electrode signal input, a large degree of amplification and summation analyses of brain wave data. In this research a latency and amplitude deviance was detected in the early and middle stages of the auditory evoked response

COMPUTER MODELLING OF NEUROTOXICITY AND AUDITORY PROCESSING DISORDER IN THE RAT AFTER CHRONIC LEAD INTOXICATION

Objective: Past research documents the ototoxicity of inorganic lead (Pb), which in children may include associated auditory processing and learning disabilities. The present investigation aims to explore in computer modelled rats, as a laboratory animal model, the persistent effects of Pb-contaminated drinking water on measures. i.e., wave latency and amplitude, of auditory brainstem function and specifically the response to a known evoked-potential assessment of Backward Masking (BM) as a marker of Auditory Processing Disorder (APD). BM refers to the disruption of an animal\u27s response to a stimulus when succeeded by a later stimulus temporally. Methods and Study Design: In order to assess the neuro-ototoxic effects and changes in auditory threshold induced from Pb, the early auditory brainstem response (ABR) is typically obtained in anesthetized rats. Unlike the ABR, the middle and late evoked auditory response is modulated by the state of the organism and is not available in anesthetized subjects. It is the middle and late evoked auditory responses that would elucidate a BM effect. For the software modelling male and female Sprague-Dawley rats will be randomized on the basis of body weight either to 0.0% (Control), 0.2% Pb acetate drinking-water exposures based on findings of an initial Pb dose range-finding trial. All response measures will be modelled with Simulink (MATLAB, Mathworks) and also with a hardware body worn unit. Assessments of ABR and middle-late responses (MID-LATE) will be obtained after 30 days of simulated chronic Pb exposure. Apparatus: A specially built apparatus has been designed to allow novel methodologies that allow for simultaneous measurement of early, middle and late Evoked Potentials (EPs). The EPs will be measured in active, un-sedated, un-restrained virtual rats. Chronically implanted dural electrodes will be used to obtain data. To accomplish this active measurement, data will be transferred wirelessly from a portable unit to a computer. Specially designed stimuli will yield a clinically applicable method to test for APDs in children. Currently, there are only subjective perceptual tests that are prone to significant error

Cortical auditory processing of informational masking effects by target-masker similarity and stimulus uncertainty

Purpose: Understanding speech in a background of other people talking is one of the most difficult listening challenges for hearing-impaired individuals, and even for those with normal hearing. Speech-on-speech masking, is known to contribute to increased perceptual difficulty over non-speech background noise because of informational masking provided over and above the energetic masking effect. While informational masking research has identified factors of similarity and uncertainty between target and masker that contribute to reduced behavioral performance in speech background noise, critical gaps in knowledge including the underlying neural-perceptual processes remain. By systematically manipulating aspects of similarity and uncertainty in the same auditory paradigm, the current study proposed to examine the time course and objectively quantify these informational masking effects at both early and late stages of auditory processing using auditory evoked potentials (AEPs) in a two-factor repeated measures paradigm. Method: Thirty participants were included in this cross sectional repeated measures design. Target-masker similarity between target and masker were manipulated by varying the linguistic/phonetic similarity (i.e. language) of the talkers in the noise maskers. Specifically, four levels representing hypothesized increasing levels of informational masking were implemented: (1) No masker (quiet), (2) Mandarin (linguistically and phonetically dissimilar), (3) Dutch (linguistically dissimilar, but phonetically similar), and (4) English (linguistically and phonetically similar). Stimulus uncertainty was manipulated by task complexity, specifically target-to-target interval (TTI) of an auditory paradigm. Participants had to discriminate between English word stimuli (/bæt/ and /pæt/) presented in an oddball paradigm in each masker condition at +3 dB SNR by pressing buttons to either the target or standard stimulus (pseudo-randomized between /bæt/ and /pæt/ for all participants). Responses were recorded simultaneously for P1-N1-P2 (standard waveform) and P3 (target waveform). This design allowed for simultaneous recording of multiple AEP peaks, including analysis of amplitude, area, and latency characteristics, as well as accuracy, reaction time, and d’ behavioral discrimination to button press responses. Finally, AEP measurers were compared to performance on a behavioral word recognition task (NU-6 25-word lists) in the proposed language maskers and at multiple signal-to-noise ratios (SNRs) to further explore if AEP components of amplitude/area and latency are correlated to behavioral outcomes across proposed maskers. Results: Several trends in AEP and behavioral outcomes were consistent with the hypothesized hierarchy of increasing linguistic/phonetic similarity from Mandarin to Dutch to English, but not all differences were significant. The most supported findings for this factor were that all babble maskers significantly affected outcomes compared to quiet, and that the native language English masker had the largest effect on outcomes in the AEP paradigm, including N1 amplitude, P3 amplitude and area, as well as decreased reaction time, accuracy, and d’ behavioral discrimination to target word responses. AEP outcomes for the Mandarin and Dutch maskers, however, were not significantly different across all measured components. Outcomes for AEP latencies for both N1 and P3 also supported an effect of stimulus uncertainty, consistent with a hypothesized increase in processing time related to increased task complexity when target stimulus timing was randomized. In addition, this effect was stronger, as evidenced by larger effect sizes, at the P3 level of auditory processing compared to the N1. An unanticipated result was the absence of the expected additive effect between linguistic/phonetic similarity and stimulus uncertainty. Finally, trends in behavioral word recognition performance were generally consistent with those observed for AEP component measures such that no differences between Dutch and Mandarin maskers were found, but the English masker yielded the lowest percent correct scores. Furthermore, correlations between behavioral word recognition and AEP component measures yielded some moderate correlations, but no common AEP components accounted for a majority of variance for behavioral word recognition. Conclusions: The results of this study add to our understanding of auditory perception in informational masking in four ways. First, observable effects of both similarity and uncertainty were evidenced at both early and late levels of auditory cortical processing. This supports the use of AEPs to better understand the informational masking deficit by providing a window into the auditory pathway. Second, stronger effects were found for P3 response, an active, top-down level of auditory processing providing some suggestion that while informational masking degradation happens at lower levels, higher level active auditory processing is more sensitive to informational masking deficits. Third, the lack of interaction of main effects leads us to a linear interpretation of the interaction of similarity and uncertainty with an equal effect across listening conditions. Fourth, even though there were few and only moderate correlations to behavioral word recognition, AEP and behavioral performance data followed the same trends as AEP measures across similarity. Through both auditory neural and behavioral testing, language maskers degraded AEPs and reduced word recognition, but particularly using a native-language masker. The behavioral and objective results from this study provide a foundation for further investigation of how the linguistic content of target and masker and task difficulty contribute to difficulty understanding speech in noise

N200 and P300 Evoked by Stimuli Straddling Category Boundary in Lexical Context

Background and Objectives: Event-related potentials (ERPs) like N200 and P300 have been reported to reflect the categorical perception of speech. The purpose of the present study is to explore whether these ERP components reflect the influence of lexical context on categorical perception. Findings may provide evidence for bottom-up or top-down processing of speech. Methods: On a seven step series of the /bi/-/pi/ continuum, a two-forced choice labeling test was administered in two conditions: /bi/ context (e.g. bee sting) and /pi/ context (e.g. pea soup). From the labeling results, Stimulus 1which is a prototypical /bi/ was selected for standard stimuli, and Stimulus 4 which showed the greatest effect of context of the between-category was selected as the deviant in an active oddball paradigm commonly used to obtain N200 and P300 ERPs. After subjects finished a two-forced choice labeling test, they participated in electrophysiological testing while simultaneously pressing a response button when they heard the deviant stimuli. A total of 450 stimuli composed of 369 standard stimuli (81%) and 81 deviant stimuli (19%) were presented in an active oddball paradigm for /bi/ and /pi/ context word conditions, respectively. ERP responses were measured using 9 electrodes from 21 normal hearing adults. Electrophysiological data (amplitude and latency of N200 and P300) and behavioral data (labeling, discrimination response accuracy, discrimination reaction time) were analyzed. Results: (1) The amplitude and latency of N200 and P300 did not represent the change in categorical perception in the presence of lexical context that was demonstrated in the labeling task, (2) N200 amplitude was the largest over the frontal region while P300 was the largest over the parietal region, (3) discrimination reaction time was faster in the /pi/ context condition than /bi/ context condition while response accuracy did not differ with context, and (4) there was no correlation between N200/P300 and behavioral data. Conclusion: N200 and P300 do not reflect the lexical effect on pre-lexical processing of categorical speech stimuli. Findings suggest that lexical context does not affect electrophysiological measures of pre-lexical speech processing (e.g., N200 or P300), supporting the autonomous (bottom-up) model that speech perception influenced by lexical context (as demonstrated behaviorally) occurs on the post-lexical level

Independent Component Analysis of Event-Related Electroencephalography During Speech and Non-Speech Discrimination: : Implications for the Sensorimotor ∆∞ Rhythm in Speech Processing

Background: The functional significance of sensorimotor integration in acoustic speech processing is unclear despite more than three decades of neuroimaging research. Constructivist theories have long speculated that listeners make predictions about articulatory goals functioning to weight sensory analysis toward expected acoustic features (e.g. analysis-by-synthesis; internal models). Direct-realist accounts posit that sensorimotor integration is achieved via a direct match between incoming acoustic cues and articulatory gestures. A method capable of favoring one account over the other requires an ongoing, high-temporal resolution measure of sensorimotor cortical activity prior to and following acoustic input. Although scalp-recorded electroencephalography (EEG) provides a measure of cortical activity on a millisecond time scale, it has low-spatial resolution due to the blurring or mixing of cortical signals on the scalp surface. Recently proposed solutions to the low-spatial resolution of EEG known as blind source separation algorithms (BSS) have made the identification of distinct cortical signals possible. The µ rhythm of the EEG is known to briefly suppress (i.e., decrease in spectral power) over the sensorimotor cortex during the performance, imagination, and observation of biological movements, suggesting that it may provide a sensitive index of sensorimotor integration during speech processing. Neuroimaging studies have traditionally investigated speech perception in two-forced choice designs in which participants discriminate between pairs of speech and nonspeech control stimuli. As such, this classical design was employed in the current dissertation work to address the following specific aims to: 1) isolate independent components with traditional EEG signatures within the dorsal sensorimotor stream network; 2) identify components with features of the sensorimotor µ rhythm and; 3) investigate changes in timefrequency activation of the µ rhythm relative to stimulus type, onset, and discriminability (i.e., perceptual performance). In light of constructivist predictions, it was hypothesized that the µ rhythm would show significant suppression for syllable stimuli prior to and following stimulus onset, with significant differences between correct discrimination trials and those discriminated at chance levels. Methods: The current study employed millisecond temporal resolution EEG to measure ongoing decreases and increases in spectral power (event-related spectral perturbations; ERSPs) prior to, during, and after the onset of acoustic speech and tone-sweep stimuli embedded in white-noise. Sixteen participants were asked to passively listen to or actively identify speech and tone signals in a two-force choice same/different discrimination task. To investigate the role of ERSPs in perceptual identification performance, high signal-to-noise ratios (SNRs) in which speech and tone identification was significantly better than chance (+4dB) and low SNRs in which performance was below chance (-6dB and -18dB) were compared to a baseline of passive noise. Independent component analysis (ICA) of the EEG was used to reduce artifact and source mixing due to volume conduction. Independent components were clustered using measure product methods and cortical source modeling, including spectra, scalp distribution, equivalent current dipole estimation (ECD), and standardized low-resolution tomography (sLORETA). Results: Data analysis revealed six component clusters consistent with a bilateral dorsal-stream sensorimotor network, including component clusters localized to the precentral and postcentral gyrus, cingulate cortex, supplemental motor area, and posterior temporal regions. Timefrequency analysis of the left and right lateralized µ component clusters revealed significant (pFDR\u3c.05) suppression in the traditional beta frequency range (13-30Hz) prior to, during, and following stimulus onset. No significant differences from baseline were found for passive listening conditions. Tone discrimination was different from passive noise in the time period following stimulus onset only. No significant differences were found for correct relative to chance tone stimuli. For both left and right lateralized clusters, early suppression (i.e., prior to stimulus onset) compared to the passive noise baseline was found for the syllable discrimination task only. Significant differences between correct trials and trials identified at chance level were found for the time period following stimulus offset for the syllable discrimination task in left lateralized cluster. Conclusions: As this is the first study to employ BSS methods to isolate components of the EEG during acoustic speech and non-speech discrimination, findings have important implications for the functional role of sensorimotor integration in speech processing. Consistent with expectations, the current study revealed component clusters associated with source models within the sensorimotor dorsal stream network. Beta suppression of the µ component clusters in both the left and right hemispheres is consistent with activity in the precentral gyrus prior to and following acoustic input. As early suppression of the µ was found prior the syllable discrimination task, the present findings favor internal model concepts of speech processing over mechanisms proposed by direct-realists. Significant differences between correct and chance syllable discrimination trials are also consistent with internal model concepts suggesting that sensorimotor integration is related to perceptual performance at the point in time when initial articulatory hypotheses are compared with acoustic input. The relatively inexpensive, noninvasive EEG methodology used in this study may have translational value in the future as a brain computer interface (BCI) approach. As deficits in sensorimotor integration are thought to underlie cognitive-communication impairments in a number of communication disorders, the development of neuromodulatory feedback approaches may provide a novel avenue for augmenting current therapeutic protocols

Neurocognitive Mechanisms of Statistical-Sequential Learning: what do Event-Related Potentials Tell Us?

Statistical-sequential learning (SL) is the ability to process patterns of environmental stimuli, such as spoken language, music, or one’s motor actions, that unfold in time. The underlying neurocognitive mechanisms of SL and the associated cognitive representations are still not well understood as reflected by the heterogeneity of the reviewed cognitive models. The purpose of this review is: (1) to provide a general overview of the primary models and theories of SL, (2) to describe the empirical research – with a focus on the event- related potential (ERP) literature – in support of these models while also highlighting the current limitations of this research, and (3) to present a set of new lines of ERP research to overcome these limitations. The review is articulated around three descriptive dimensions in relation to SL: the level of abstractness of the representations learned through SL, the effect of the level of attention and consciousness on SL, and the developmental trajectory of SL across the life-span. We conclude with a new tentative model that takes into account these three dimensions and also point to several promising new lines of SL research

Using auditory evoked brain responses to detect anxious vulnerabilities in neonates.

Anxiety disorders are prevalent in both adult and child populations, and are associated with significant economic and psychosocial costs. There are clearly familial patterns of transmission within the anxiety disorders, and the inherited risk is likely a non-specific vulnerability toward negative affect, with a biological-environmental interaction leading to specific manifestations within the anxiety disorders. Among the vulnerabilities toward anxiety may be information processing biases that predispose individuals to be more vigilant to novelty, processes that may be specifically associated with the right cerebral hemisphere. The current study utilized auditory event related potentials (ERPs) to explore the degree to which such processes may be related to risk toward anxiety disorders in a neonatal population (n=30). Findings supported the growing evidence that predispositions toward anxious patterns of responding are associated with greater activation of the right cerebral hemisphere, as neonates of more highly anxious mothers displayed more positive right hemisphere responses overall. Further, consistent with theories that attentional biases toward novelty are associated with the development and maintenance of pathological anxiety, it was found that measures of both maternal state and trait anxiety were significant predictors of the neonate\u27s brain response to a stranger\u27s voice. These findings are discussed in terms of implications for further understanding the developmental pathways associated pathological anxiety