The processing of sound duration after left hemisphere stroke: Event-related potential and behavioral evidence

The ability of left-hemisphere stroke patients ( n = 8) and healthy control subjects ( n = 8) to process sounds preattentively and attentively was studied by recording auditory event-related potentials (ERPs) and behavioral responses. For the right-ear stimulation, the mismatch negativity (MMN) was significantly smaller in the patients than control subjects over both hemispheres. For the left-ear stimuli, the MMN was significantly smaller in the patient group than in the control group over the left hemisphere, whereas no group differences were obtained over the right hemisphere. In addition, the N1 amplitude was reduced bilaterally for the right-ear stimulation (with the reduction being larger over the left hemisphere), whereas no significant effects on the N1 amplitude were found for the left-ear stimulation. Behaviorally, the patients detected significantly fewer deviant tones than did the control subjects irrespective of the stimulated ear. The present results thus suggest that the long-latency ERPs can be used to probe such auditory processing deficits that are difficult to define with behavioral measures. Especially by recording MMN to monaural stimuli, the discrimination accuracy can be separately determined for the left and right temporal lobes.     

Effects of methylphenidate in ADHD adults on target evaluation processing reflected by event-related potentials

Attention deficit/hyperactivity disorder (ADHD) is a widely examined disease in childhood. There is evidence that the disease responds well to medication with methylphenidate (MPH). The effect of MPH in adults with ADHD is a question that is often raised, because many adults request such therapy today. As yet, there is a lack of studies on event-related potentials (ERPs) and MPH in ADHD adults. In the present study we examined 10 adults diagnosed with ADHD, with and without MPH medication (30 mg daily), by means of ERP in a visual Go/NoGo experiment to gain information about target evaluation processing in these patients and about the effects on these attentional processes during medication with MPH. Visually, there seem to be differences in the frontal electrodes for the N2 and in the parietal electrodes for the P300. But these differences do not achieve statistical significance. There are also no statistically relevant differences for the N1 or the slow wave. MPH does not seem to have an effect on target evaluation processing, when comparing the ERPs of non-medicated and medicated ADHD adults. Especially the P3 does not appear to be modulated by medication with MPH in these ADHD adults, in contrast to findings in ADHD children.     

Distraction in a continuous-stimulation detection task

Event-related potential (ERP) correlates of distraction are usually investigated in the oddball paradigm following a discrete, trial-by-trial stimulation protocol. In this design, participants perform a discrimination task while oddball stimuli deviate in a task-irrelevant stimulus feature. In our experiment, participants detected gaps in a continuous tone while infrequent frequency glides served as distracting events.Glides preceding a gap by 150 ms delayed the response to the gap and elicited the ERP sequence of N1, probably MMN, P3a, and reorienting negativity, suggesting that these responses reflect distraction-related processes which are neither task- nor stimulation-specific.When participants watched a silent movie and the auditory stimulation was task-irrelevant, glides preceding a gap by 150 ms enhanced the amplitude of the gap-elicited N1. However, when the auditory stimulation was task-relevant, the gap-elicited N1 was attenuated. These results show that the glides drew attention away from the ongoing task, both from watching the silent movie and from detecting gaps.     

The time course of psychological stress as revealed by event-related potentials

Psychological stress is common in everyday life and is believed to affect emotion, cognition and health. Previous brain imaging studies have been able to identify the brain regions involved in the stress response. However, our understanding of the temporal neurological response to psychological stress is limited. The present work aims to investigate the time course of psychological stress induced by a mental arithmetic task, utilizing event-related potentials (ERPs). The elicitation of stress was verified by self-reports of stress and increases in salivary cortisol levels. The subjective and physiological data showed that the stress-elicitation paradigm successfully induced a mild-to-moderate level of psychological stress. The electrophysiological data showed that the amplitude of occipital N1 was more negative in the control task than in the stress task, and the latency of frontal P2 was shorter in the stress task than in the control task. Our results provide electrophysiological evidence that psychological stress occurs primarily at the early stage of cognitive processing.     

Influence of acute stress on response inhibition in healthy men: An ERP study

The current study investigated the influence of acute stress and the resulting cortisol increase on response inhibition and its underlying cortical processes, using EEG. Before and after an acute stressor or a control condition, 39 healthy men performed a go/no‐go task while ERPs (N2, P3), reaction times, errors, and salivary cortisol were measured. Acute stress impaired neither accuracy nor reaction times, but differentially affected the neural correlates of response inhibition; namely, stress led to enhanced amplitudes of the N2 difference waves (N2d, no‐go minus go), indicating enhanced response inhibition and conflict monitoring. Moreover, participants responding to the stressor with an acute substantial rise in cortisol (high cortisol responders) showed reduced amplitudes of the P3 of the difference waves (P3d, no‐go minus go) after the stressor, indicating an impaired evaluation and finalization of the inhibitory process. Our findings indicate that stress leads to a reallocation of cognitive resources to the neural subprocesses of inhibitory control, strengthening premotor response inhibition and the detection of response conflict, while concurrently diminishing the subsequent finalization process within the stream of processing.     

Auditory event-related potentials reflect dedicated change detection activity for higher-order acoustic transitions

The processing of auditory changes at cortical level relies partly on dedicated change-detectors whose activity is reflected in the elicitation of the N1 and P2 event-related potentials (ERPs). In previous studies, N1 and P2 have been found only for first-order frequency transitions (i.e. constant-to-glide) but not for higher-order transitions (i.e. glide-to-constant). We tested whether this asymmetry is due to the complete lack, or the smaller number of dedicated higher-order change detectors compared to first-order change detectors by recording ERPs to constant-to-glide and glide-to-constant frequency transitions within pure and complex tones. For constant-to-glide transitions ERP amplitudes increased with the rate of frequency change and spectral complexity. Importantly, for glide-to-constant transitions, N1 was elicited, even though only for spectrally rich tones when the frequency-change rate was fastest. Thus, the asymmetry in auditory change-related N1 elicitation is attributable not to the lack of higher-order change detectors, but to their relatively low number.     

An increase in salivary interleukin-6 level following acute psychosocial stress and its biological correlates in healthy young adults

Although interleukin-6 (IL-6) has been investigated frequently in stress research, knowledge regarding the biological processes of IL-6 in association with psychosocial stress remains incomplete. This study focused on salivary IL-6 and reports its temporal variation and biological correlates following acute psychosocial stress. Fifty healthy young adults (39 male and 11 female students) were subjected to the psychosocial stress test ‘Trier Social Stress Test’ (TSST), wherein the participants were asked to deliver a speech and perform a mental arithmetic task in front of 2 audiences. Collection of saliva samples, measurement of heart rate, and assessment of negative moods by visual analogue scales were conducted before, during, and after TSST. Salivary IL-6 levels increased by approximately 50% in response to the TSST and remained elevated for 20 min after the stress tasks were completed. Cluster analyses revealed that individuals with sustained elevation of IL-6 levels following the TSST exhibited a lower cortisol response compared to individuals with lower IL-6 levels. In the correlation analyses, a greater IL-6 response was associated with a higher heart rate during the mental arithmetic task (r = .351, p < .05) and with a lower cortisol response (r = −.302, p < .05). This study demonstrates that salivary IL-6 levels are elevated for a relatively long period following acute psychosocial stress, and suggests that sympathetic activity and cortisol secretion are involved in elevation of salivary IL-6 levels.     

Dimension‐based attention modulates early visual processing

Target selection can be based on spatial or dimensional/featural mechanisms operating in a location‐independent manner. We investigated whether dimension‐based attention affects processing in early visual stages. Subjects searched for a singleton target among an 8‐item array, with the search display preceded by an identical cue array with a dimensionally non‐predictive, but spatially predictive singleton. Reaction times (RTs) were increased for changes in the target‐defining dimension but not for featural changes within a dimension. This RT effect was mirrored by modulations of the P1 and anterior transition N2 (tN2). Current density reconstructions revealed increased activity in dorsal occipital cortex and decreased activity in left frontopolar cortex owing to repeated dimensional pop‐out identities. These findings strengthen dimension‐based theories of visual attention by indicating dimension‐, rather than feature‐, specific influences within the first 110 ms of visual processing.     

Stress-buffering effects of psychosocial resources on physiological and psychological stress response in pregnant women

Sixty healthy pregnant women (aged 21-35 years), including 30 pregnant women at the beginning of second trimester and 30 women at the beginning of third trimester underwent a psychosocial stress test. Physiological (salivary free cortisol levels, salivary alpha-amylase levels) and psychological (perceived stress, mood, anxiety) responses to standardized psychosocial stress have been brought in association with psychosocial resources (self-efficacy and daily uplifts). Predictions revealed that higher resources predict lower physiological and psychological stress responses and higher mood levels. We conclude from our data that psychosocial resources appear to dampen psychological and physiological stress response during pregnancy.     

Circadian rhythm changes in heart rate variability during chronic sound stress

To study the circadian rhythm changes of the heart rate variability (HRV) during chronic sound stress, Wistar rats were implanted with telemetry transmitters and exposed to chronic ultrasound stress for 14 days. The heart rate, mean R-R intervals (mean R-R) and body temperature were monitored hourly. The spectra of five-minute heart rate variability were plotted on a log-log scale of frequency versus power spectral density, and the spectral exponent β of the regression line of this plot was calculated. The exponent β, heart rate (HR) and body temperature recorded hourly were plotted and fitted to sine curves to observe the circadian rhythm of these parameters. The correlation coefficient of the fitted sine curves in β decreased from 0.644 in the control period to 0.105 in the stress period, indicating that the rhythm of β deceased during stress. This did not occur in the other two parameters, demonstrating that the HRV exponent can assess chronic stress.     

Auditory processing that leads to conscious perception: a unique window to central auditory processing opened by the mismatch negativity and related responses

In this review, we will present a model of brain events leading to conscious perception in audition. This represents an updated version of Näätänen's previous model of automatic and attentive central auditory processing. This revised model is mainly based on the mismatch negativity (MMN) and N1 indices of automatic processing, the processing negativity (PN) index of selective attention, and their magnetoencephalographic (MEG) and functional magnetic resonance imaging (fMRI) equivalents. Special attention is paid to determining the neural processes that might underlie conscious perception and the borderline between automatic and attention‐dependent processes in audition.     

Electrophysiological indexes of option characteristic processing

Decision making is vital to human behavior and can be divided into multiple stages including option assessment, behavioral output, and feedback evaluation. Studying how people evaluate option characteristics in the option assessment stage would provide important knowledge on human decision making. Using the event‐related potential (ERP) method, the present study investigated the neural mechanism of evaluating two types of option characteristics (i.e., reward magnitude and degree of uncertainty) in the temporal dimension. Thirty‐five volunteers participated in a monetary gambling task, where they either accepted or rejected gambles. The ERP results showed a double dissociation pattern, with the early P1 component being sensitive to magnitude but insensitive to degree of uncertainty, while both the N2 and P3 components showed the opposite pattern. The results suggest that these two fundamental option features are assessed rapidly and separately in the human brain. Specifically, small magnitude elicited a larger P1 than did large magnitude, indicating that the perceptual and attentional processing of options is modulated by magnitude. Both the N2 and P3 amplitudes evoked by the risky context were larger than those evoked by the ambiguous one, reflecting that more cognitive conflicts and resources are involved in the former condition. Furthermore, the P1, but not the N2 or P3, amplitude was sensitive to decisions, suggesting that early attentional processes may contribute to human decision making. These findings may provide insight into the temporal mechanisms of option characteristic processing.     

花姜酮通过抑制氧化应激减轻MPP~+诱导的SH-SY5Y细胞损伤

目的:探讨花姜酮(zerumbone,ZER)对1-甲基-4-苯基-吡啶鎓离子(1-methyl-4-phenylpyridinium,MPP~+)诱导的人神经母细胞瘤SH-SY5Y细胞损伤的作用及其可能的分子机制。方法:采用CCK-8法检测MPP~+对SH-SY5Y细胞的毒性作用以及ZER的保护作用,采用流式细胞术检测活性氧簇(reactive oxygen species,ROS)含量和细胞凋亡情况,采用短发夹RNA(short hairpin RNA,shRNA)干扰技术抑制人帕金森病蛋白7(Parkinson disease protein 7,PARK7)基因的表达,采用Western blot法检测PARK7、核因子E2相关因子2(nuclear factor E2-related factor 2,Nrf2)和血红素氧合酶1(heme oxygenase-1,HO-1)的蛋白表达水平。结果:MPP~+可显著抑制SH-SY5Y细胞活力(P0.05),并呈剂量和时间依赖性;ZER可使经600μmol/L MPP~+处理24 h的SH-SY5Y细胞活力升高,PARK7和Nrf2蛋白表达水平显著升高(P0.05),ROS含量和细胞凋亡明显减少(P0.05),抗氧化剂N-乙酰-L-半胱氨酸(N-acetyl-L-cysteine,NAC)具有相似的作用;沉默PARK7基因后,Nrf2和HO-1蛋白的表达水平明显下降(P0.05),ROS含量和细胞凋亡显著增加(P0.05)。结论:ZER可在体外剂量依赖性地减轻MPP~+对SH-SY5Y细胞的毒性作用,这可能与ZER激活PARK7/Nrf2/HO-1通路,继而抑制MPP~+诱导的ROS生成和细胞凋亡有关。     

Effects of inter-stimulus interval (ISI) duration on the N1 and P2 components of the auditory event-related potential

The N1 and P2 components of the event-related potential are relevant markers in the processing of auditory information, indicating the presence of several acoustic phenomena, such as pure tones or speech sounds. In addition, the expression of these components seems to be sensitive to diverse experimental variations. The main purpose of the present investigation was to explore the role of inter-stimulus interval (ISI) on the N1 and P2 responses, considering two widely used experimental paradigms: a single tone task (1000 Hz sound repeated in a fixed rhythm) and an auditory oddball (80% of the stimuli were equal to the sound used in the single tone and the remaining were a 1500 Hz tone). Both tasks had four different conditions, and each one tested a fixed value of ISI (600, 1000, 3000, or 6000 ms). A sample of 22 participants performed these tasks, while an EEG was recorded, in order to examine the maximum amplitude of the N1 and P2 components. Analysis of the stimuli in the single tone task and the frequent tones in the oddball task revealed a similar outcome for both tasks and for both components: N1 and P2 amplitudes were enhanced in conditions with longer ISIs regardless of task. This response pattern emphasizes the dependence of both the N1 and P2 components on the ISI, especially in a scenario of repetitive and regular stimulation. The absence of task effects suggests that the ISI effect reported may depend on refractory mechanisms rather than being due to habituation effects.     

Neuromagnetic recordings reveal the temporal dynamics of auditory spatial processing in the human cortex

In an attempt to delineate the assumed 'what' and 'where' processing streams, we studied the processing of spatial sound in the human cortex by using magnetoencephalography in the passive and active recording conditions and two kinds of spatial stimuli: individually constructed, highly realistic spatial (3D) stimuli and stimuli containing interaural time difference (ITD) cues only. The auditory P1m, N1m, and P2m responses of the event-related field were found to be sensitive to the direction of sound source in the azimuthal plane. In general, the right-hemispheric responses to spatial sounds were more prominent than the left-hemispheric ones. The right-hemispheric P1m and N1m responses peaked earlier for sound sources in the contralateral than for sources in the ipsilateral hemifield and the peak amplitudes of all responses reached their maxima for contralateral sound sources. The amplitude of the right-hemispheric P2m response reflected the degree of spatiality of sound, being twice as large for the 3D than ITD stimuli. The results indicate that the right hemisphere is specialized in the processing of spatial cues in the passive recording condition. Minimum current estimate (MCE) localization revealed that temporal areas were activated both in the active and passive condition. This initial activation, taking place at around 100 ms, was followed by parietal and frontal activity at 180 and 200 ms, respectively. The latter activations, however, were specific to attentional engagement and motor responding. This suggests that parietal activation reflects active responding to a spatial sound rather than auditory spatial processing as such.     

Long-term exposure to noise impairs cortical sound processing and attention control

Long-term exposure to noise impairs human health, causing pathological changes in the inner ear as well as other anatomical and physiological deficits. Numerous individuals are daily exposed to excessive noise. However, there is a lack of systematic research on the effects of noise on cortical function. Here we report data showing that long-term exposure to noise has a persistent effect on central auditory processing and leads to concurrent behavioral deficits. We found that speech-sound discrimination was impaired in noise-exposed individuals, as indicated by behavioral responses and the mismatch negativity brain response. Furthermore, irrelevant sounds increased the distractibility of the noise-exposed subjects, which was shown by increased interference in task performance and aberrant brain responses. These results demonstrate that long-term exposure to noise has long-lasting detrimental effects on central auditory processing and attention control.     

Auditory streaming affects the processing of successive deviant and standard sounds

This study investigated the temporal relation between two early mechanisms of auditory information processing: the segregation of the auditory input into streams and the automatic deviance detection indicated by the mismatch negativity (MMN). To address this question the processing of successive deviant and standard tones within streaming and nonstreaming conditions was analyzed. In the streaming condition the amplitude reduction of MMN elicited by the second of two successive deviants was found to be smaller for successive deviants presented in different than in same streams. No corresponding MMN differences were obtained in a nonstreaming condition. These results demonstrate that stream segregation precedes deviance detection. Moreover, modulations of the N1 amplitudes elicited by successive standard tones in the streaming condition demonstrate that not only deviance-related processing but even initial sound processing is affected by streaming.     

Masking of a first target in the attentional blink attenuates the P3 to the first target and delays the P3 to the second target

The attentional blink (AB) refers to the decline in report accuracy of a second target (T2) when presented shortly after a first target (T1) in a rapid serial visual presentation (RSVP) of distractors. It is known that masking T1 increases the magnitude of the AB, and masking a single target (equivalent to T1) in a RSVP stream attenuates the P3 to the target in correct trials. The major purpose of the present study was to clarify how these two effects may be integrated. An intervening distractor was presented at lag 1 (T1+1), at lag 2 (T1+2), or at neither of these two lags (no distractor). T2 was always presented at lag 3, as the last item in the stream. The P3 to T1 was attenuated and the P3 to T2 delayed in the T1+1 condition compared to the two other distractor conditions. These results clearly show that masking T1 attenuates the P3 to T1 and delays the P3 to T2 in the AB. Implications for extant theories of the AB are discussed.     

The temporal locus of the interaction between working memory consolidation and the attentional blink

An increase in concurrent working memory load has been shown to amplify the attentional blink. The present study investigated the temporal locus of this phenomenon, by using a dual rapid serial visual presentation paradigm that enabled the measurement of lateralized event‐related potentials. The P3 component was shown to be affected by both working memory load and the lag between the target stimuli, consistent with current models of temporal attention and a functional explanation of the P3 in terms of memory consolidation. P3 amplitude was reduced for short target lags and high memory loads. The P2 component was affected by lag only, and not memory load. Importantly, the N2pc component was modulated also by both lag and memory load. The results showed that early attentional processing (as marked by the N2pc) was suppressed by increased involvement of working memory, a phenomenon not well predicted by many current theories of temporal attention.     

N1 response attenuation and the mismatch negativity (MMN) to within‐ and across‐category phonetic contrasts

According to the neural adaptation model of the mismatch negativity (MMN), the sensitivity of this event‐related response to both acoustic and categorical information in speech sounds can be accounted for by assuming that (a) the degree of overlapping between neural representations of two sounds depends on both the acoustic difference between them and whether or not they belong to distinct phonetic categories, and (b) a release from stimulus‐specific adaptation causes an enhanced N1 obligatory response to infrequent deviant stimuli. On the basis of this view, we tested in Experiment 1 whether the N1 response to the second sound of a pair (S₂) would be more attenuated in pairs of identical vowels compared with pairs of different vowels, and in pairs of exemplars of the same vowel category compared with pairs of exemplars of different categories. The psychoacoustic distance between S₁ and S₂ was the same for all within‐category and across‐category pairs. While N1 amplitudes decreased markedly from S₁ to S₂, responses to S₂ were quite similar across pair types, indicating that the attenuation effect in such conditions is not stimulus specific. In Experiment 2, a pronounced MMN was elicited by a deviant vowel sound in an across‐category oddball sequence, but not when the exact same deviant vowel was presented in a within‐category oddball sequence. This adds evidence that MMN reflects categorical phonetic processing. Taken together, the results suggest that different neural processes underlie the attenuation of the N1 response to S₂ and the MMN to vowels.