Explicit attention interferes with selective emotion processing in human extrastriate cortex

Background  

Brain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN) for pleasant and unpleasant compared to neutral images (~150–300 ms poststimulus). The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands.     

Phonemes, intensity and attention: differential effects on the mismatch negativity (MMN)

Auditory event-related potentials (ERPs) to speech sounds were recorded in a demanding selective attention task to measure how the mismatch negativity (MMN) was affected by attention, deviant feature, and task relevance, i.e., whether the feature was target or nontarget type. With vowel-consonant-vowel (VCV) disyllables randomly presented to the right and left ears, subjects attended to the VCVs in one ear. In different conditions, the subjects responded to either intensity or phoneme deviance in the consonant. The position of the deviance within the VCV also varied, being in the first (VC), second (CV), or both (VC and CV) formant-transition regions. The MMN amplitudes were larger for deviants in the attended ear. Task relevance affected the MMNs to intensity and phoneme deviants differently. Target-type intensity deviants yielded larger MMNs than nontarget types. For phoneme deviants there was no main effect of task relevance, but there was a critical interaction with deviance position. The both position gave the largest MMN amplitudes for target-type phoneme deviants, as it did for target- and nontarget-type intensity deviants. The MMN for nontarget-type phoneme deviants, however, showed an inverse pattern such that the MMN for the both position had the smallest amplitude despite its greater spectro-temporal deviance and its greater detectability when it was the target. These data indicate that the MMN reflects differences in phonetic structure as well as differences in acoustic spectral-energy structure of the deviant stimuli. Furthermore, the task relevance effects demonstrate that top-down controls not only affect the amplitude of the MMN, but can reverse the pattern of MMN amplitudes among different stimuli.     

Effects of stimulus frequency and complexity on the mismatch negativity and other components of the cortical auditory-evoked potential

This study investigated, first, the effect of stimulus frequency on mismatch negativity (MMN), N1, and P2 components of the cortical auditory event-related potential (ERP) evoked during passive listening to an oddball sequence. The hypothesis was that these components would show frequency-related changes, reflected in their latency and magnitude. Second, the effect of stimulus complexity on those same ERPs was investigated using words and consonant-vowel tokens (CVs) discriminated on the basis of formant change. Twelve normally hearing listeners were tested with tone bursts in the speech frequency range (400/440, 1,500/1,650, and 3,000/3,300 Hz), words (/baed/ vs /daed/) and CVs (/bae/ vs /dae/). N1 amplitude and latency decreased as frequency increased. P2 amplitude, but not latency, decreased as frequency increased. Frequency-related changes in MMN were similar to those for N1, resulting in a larger MMN area to low frequency contrasts. N1 amplitude and latency for speech sounds were similar to those found for low tones but MMN had a smaller area. Overall, MMN was present in 46%-71% of tests for tone contrasts but for only 25%-32% of speech contrasts. The magnitude of N1 and MMN for tones appear to be closely related, and both reflect the tonotopicity of the auditory cortex.     

The modulation of auditory novelty processing by working memory load in school age children and adults: a combined behavioral and event-related potential study

Background  

We investigated the processing of task-irrelevant and unexpected novel sounds and its modulation by working-memory load in children aged 9-10 and in adults. Environmental sounds (novels) were embedded amongst frequently presented standard sounds in an auditory-visual distraction paradigm. Each sound was followed by a visual target. In two conditions, participants evaluated the position of a visual stimulus (0-back, low load) or compared the position of the current stimulus with the one two trials before (2-back, high load). Processing of novel sounds were measured with reaction times, hit rates and the auditory event-related brain potentials (ERPs) Mismatch Negativity (MMN), P3a, Reorienting Negativity (RON) and visual P3b.     

Mismatch Negativity and Stimulus-Preceding Negativity in Paradigms of Increasing Auditory Complexity: A Possible Role in Predictive Coding

The auditory mismatch negativity (MMN) has been considered a preattentive index of auditory processing and/or a signature of prediction error computation. This study tries to demonstrate the presence of an MMN to deviant trials included in complex auditory stimuli sequences, and its possible relationship to predictive coding. Additionally, the transfer of information between trials is expected to be represented by stimulus-preceding negativity (SPN), which would possibly fit the predictive coding framework. To accomplish these objectives, the EEG of 31 subjects was recorded during an auditory paradigm in which trials composed of stimulus sequences with increasing or decreasing frequencies were intermingled with deviant trials presenting an unexpected ending. Our results showed the presence of an MMN in response to deviant trials. An SPN appeared during the intertrial interval and its amplitude was reduced in response to deviant trials. The presence of an MMN in complex sequences of sounds and the generation of an SPN component, with different amplitudes in deviant and standard trials, would support the predictive coding framework.     

Preparation of nanoparticles of poorly water-soluble antioxidant curcumin by antisolvent precipitation methods

The objective of this study was to enhance the solubility and dissolution rate of a poorly water-soluble antioxidant, curcumin, by fabricating its nanoparticles with two methods: antisolvent precipitation with a syringe pump (APSP) and evaporative precipitation of nanosuspension (EPN). For APSP, process parameters like flow rate, stirring speed, solvent to antisolvent (SAS) ratio, and drug concentration were investigated to obtain the smallest particle size. For EPN, factors like drug concentration and the SAS ratio were examined. The effects of these process parameters on the supersaturation, nucleation, and growth rate were studied and optimized to obtain the smallest particle size of curcumin by both the methods. The average particle size of the original drug was about 10–12 μm and it was decreased to a mean diameter of 330 nm for the APSP method and to 150 nm for the EPN method. Overall, decreasing the drug concentration or increasing the flow rate, stirring rate, and antisolvent amount resulted in smaller particle sizes. Differential scanning calorimetry studies suggested lower crystallinity of curcumin particles fabricated. The solubility and dissolution rates of the prepared curcumin particles were significantly higher than those the original curcumin. The antioxidant activity, studied by the DPPH free radical-scavenging assay, was greater for the curcumin nanoparticles than the original curcumin. This study demonstrated that both the methods can successfully prepare curcumin into submicro to nanoparticles. However, drug particles prepared by EPN were smaller than those by APSP and hence, showed the slightly better solubility, dissolution rate, and antioxidant activity than the latter.     

Looking for a pattern: An MEG study on the abstract mismatch negativity in musicians and nonmusicians

Background  

The mismatch negativity (MMN) is an early component of event-related potentials/fields, which can be observed in response to violations of regularities in sound sequences. The MMN can be elicited by simple feature (e.g. pitch) deviations in standard oddball paradigms as well as by violations of more complex sequential patterns. By means of magnetoencephalography (MEG) we investigated if a pattern MMN could be elicited based on global rather than local probabilities and if the underlying ability to integrate long sequences of tones is enhanced in musicians compared to nonmusicians.     

Cortical auditory evoked potential correlates of categorical perception of voice-onset time.

The goal of this study was to examine the neural encoding of voice-onset time distinctions that indicate the phonetic categories /da/ and /ta/ for human listeners. Cortical Auditory Evoked Potentials (CAEP) were measured in conjunction with behavioral perception of a /da/-/ta/ continuum. Sixteen subjects participated in identification and discrimination experiments. A sharp category boundary was revealed between /da/ and /ta/ around the same location for all listeners. Subjects' discrimination of a VOT change of equal magnitude was significantly more accurate across the /da/-/ta/ categories than within the /ta/ category. Neurophysiologic correlates of VOT encoding were investigated using the N1 CAEP which reflects sensory encoding of stimulus features and the MMN CAEP which reflects sensory discrimination. The MMN elicited by the across-category pair was larger and more robust than the MMN which occurred in response to the within-category pair. Distinct changes in N1 morphology were related to VOT encoding. For stimuli that were behaviorally identified as /da/, a single negativity (N1) was apparent; however, for stimuli identified as /ta/, two distinct negativities (N1 and N1') were apparent. Thus the enhanced MMN responses and the morphological discontinuity in N1 morphology observed in the region of the /da/-/ta/ phonetic boundary appear to provide neurophysiologic correlates of categorical perception for VOT.     

Modulation of auditory evoked responses to spectral and temporal changes by behavioral discrimination training

Background  

Due to auditory experience, musicians have better auditory expertise than non-musicians. An increased neocortical activity during auditory oddball stimulation was observed in different studies for musicians and for non-musicians after discrimination training. This suggests a modification of synaptic strength among simultaneously active neurons due to the training. We used amplitude-modulated tones (AM) presented in an oddball sequence and manipulated their carrier or modulation frequencies. We investigated non-musicians in order to see if behavioral discrimination training could modify the neocortical activity generated by change detection of AM tone attributes (carrier or modulation frequency). Cortical evoked responses like N1 and mismatch negativity (MMN) triggered by sound changes were recorded by a whole head magnetoencephalographic system (MEG). We investigated (i) how the auditory cortex reacts to pitch difference (in carrier frequency) and changes in temporal features (modulation frequency) of AM tones and (ii) how discrimination training modulates the neuronal activity reflecting the transient auditory responses generated in the auditory cortex.     

Perception of musical and lexical tones by Taiwanese-speaking musicians

This study explored the relationship between music and speech by examining absolute pitch and lexical tone perception. Taiwanese-speaking musicians were asked to identify musical tones without a reference pitch and multispeaker Taiwanese level tones without acoustic cues typically present for speaker normalization. The results showed that a high percentage of the participants (65% with an exact match required and 81% with one-semitone errors allowed) possessed absolute pitch, as measured by the musical tone identification task. A negative correlation was found between occurrence of absolute pitch and age of onset of musical training, suggesting that the acquisition of absolute pitch resembles the acquisition of speech. The participants were able to identify multispeaker Taiwanese level tones with above-chance accuracy, even though the acoustic cues typically present for speaker normalization were not available in the stimuli. No correlations were found between the performance in musical tone identification and the performance in Taiwanese tone identification. Potential reasons for the lack of association between the two tasks are discussed.     

Steady-State and Time Resolved Fluorescence Analysis on Tyrosine–Histidine Model Compounds

Four model compounds, for a tyrosine–histidine covalent bonding, 2-(5-imidazolyl)-4-methylphenol (C–C bonding in ortho-position at the phenyl group); 2′-(1-imidazolyl)-4-methylphenol (C–N bonding in ortho′-position at the phenyl group); 2-(5-imidazolyl)-4-H-phenol and 2-(5-imidazolyl)-4-H-phenol, at physiological pH have been studied by UV-Vis absorption, steady-state and time resolved fluorescence spectroscopy. Their absorption and emission properties are presented and discussed. The photophysical properties depend on the para-substituted phenyl group as well as on C–C/C–N bonding in the Phenol–Imidazole linkage. The N position, N1–N3/N1–N4, in the imidazole group was found to be relevant. The results are discussed with relevance to the redox processes of tyrosine and to better understand the role of a tyrosine–histidine covalent linkage as found in cytochrome c oxidase.     

The role of stimulus cross-splicing in an event-related potentials study. Misleading formant transitions hinder automatic phonological processing

The mental organization of linguistic knowledge and its involvement in speech processing can be investigated using the mismatch negativity (MMN) component of the auditory event-related potential. A contradiction arises, however, between the technical need for strict control of acoustic stimulus properties and the quest for naturalness and acoustic variability of the stimuli. Here, two methods of preparing speech stimulus material were compared. Focussing on the automatic processing of a phonotactic restriction in German, two corresponding sets of various vowel-fricative syllables were used as stimuli. The former syllables were naturally spoken while the latter ones were created by means of cross-splicing. Phonetically, natural and spliced syllables differed with respect to the appropriateness of coarticulatory information about the forthcoming fricative within the vowels. Spliced syllables containing clearly misleading phonetic information were found to elicit larger N2 responses compared to their natural counterparts. Furthermore, MMN results found for the natural syllables could not be replicated with these spliced stimuli. These findings indicate that the automatic processing of the stimuli was considerably affected by the stimulus preparation method. Thus, in spite of its unquestioned benefits for MMN experiments, the splicing technique may lead to interference effects on the linguistic factors under investigation.     

The high frequency magnetic properties of self assembled Fe–Co–Si–N nanogranular thin films

The effect of a variation in Si and N concentration on the microstructure, crystal structure and high-frequency magnetic properties of Fe–Co–Si–N nanogranular thin films was investigated. The films, prepared by rf magnetron sputtering, consisted of nanosized grains of FeCo as well as a Si and N rich intergranular amorphous phase. The Si concentration had a significant effect on the crystal structure of the FeCo phase. The resistivities of the Fe–Co–Si–N films were significantly enhanced by an increase in Si concentration. The resonant frequency of the Fe–Co–Si–N films could be tuned from 0.45 GHz to 2.1 GHz by controlling Si concentration. The N concentration greatly influenced magnetic properties and the variation in resonant frequency is in agreement with Kittel’s equation.     

Properties of reactively sputtered W–B–N thin film as a diffusion barrier for Cu metallization on Si

Thin films of W–B–N (10 nm) have been evaluated as diffusion barriers for Cu interconnects. The amorphous W–B–N thin films were prepared at room temperature via reactive magnetron sputtering using a W₂B target at various N₂/(Ar + N₂) flow ratios. Cu diffusion tests were performed after in-situ deposition of 200 nm Cu. Thermal annealing of the barrier stacks was carried out in vacuum at elevated temperatures for one hour. X-ray diffraction patterns, sheet resistance measurement, cross-section transmission electron microscopy images, and energy-dispersive spectrometer scans on the samples annealed at 500°C revealed no Cu diffusion through the barrier. The results indicate that amorphous W–B–N is a promising low resistivity diffusion barrier material for copper interconnects.     

Determination and analysis of the optical constants of thin films of nickel(II) and copper(II) hydrazone complexes by spectroscopic ellipsometry

Thin films of four nickel(II) and copper(II) hydrazone complexes, which will hopefully be used as recording layers for the next-generation of high-density recordable disks, were prepared by using the spin-coating method. Absorption spectra of the thin films on K9 optical glass substrates in the 300–700 nm wavelength region were measured. Optical constants (complex refractive indices N) and thickness d of the thin films prepared on single-crystal silicon substrates in the 275–675 nm wavelength region were investigated on a rotating analyzer-polarizer scanning ellipsometer by fitting the measured ellipsometric angles (Ψ(λ) and Δ(λ)) with a 3-layer model (Si/dye film/air). The dielectric functions ε and absorption coefficients α as a function of the wavelength were then calculated. Additionally, a design to achieve high reflectivity and optimum dye film thickness with an appropriate reflective layer was performed with the Film Wizard software using a multilayered model (PC substrate/reflective layer/dye film/air) at 405 nm wavelength. PACS 81.05.L; 78.20.Ci; 78.20.-e     

New insights into nanocomposite adsorbents for water treatment: A case study of polystyrene-supported zirconium phosphate nanoparticles for lead removal

By encapsulating zirconium phosphate (ZrP) nanoparticles into three macroporous polystyrene resins with various surface groups, i.e., −CH₂Cl, −SO₃ ⁻, and −CH₂N⁺(CH₃)₃ three nanocomposite adsorbents (denoted as ZrP–Cl, ZrP–S, and ZrP–N) were fabricated, respectively for lead removal from water. Effect of the functional groups on nano-ZrP dispersion and effect of ZrP immobilization on the mechanical strength of the resulting nanocomposites were investigated. The presence of the charged functional groups (−SO₃ ⁻ and −CH₂N⁺(CH₃)₃) are more favorable than the neutral −CH₂Cl group to improve nano-ZrP dispersion (i.e., to achieve smaller ZrP nanoparticles). ZrP–N and ZrP–S had higher capacity than ZrP–Cl for lead removal. As compared to ZrP–N, ZrP–S exhibits higher preference toward lead ion at high calcium levels as a result of the potential Donnan membrane effect. On the other hand, nano-ZrP immobilization would simultaneously reinforce both the compressive strength and the wear performance of the resulting nanocomposites with the ZrP loadings up to 5 wt%. The results reported herein would shed some light on the generation of environmental nanocomposites with high capacity and excellent mechanical strength.     

Synthesis of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes

We report the observations made on the synthesis and characterization of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes. The C–N nanotube Blocks have been synthesized by pyrolyzing the mixture of silver nitrate acetonitrile solution and ferrocene benzene solution. The structural/microstructural characterization of the as-synthesized material has been done using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS) analysis has been carried out to confirm the presence of nitrogen in nanotubes. These investigations reveal the formation of blocks of bamboo-like nanotubes having the dimension 300 × 200 × 30 μm and the diameter is 20–50 nm. We also observe the formation of Y-junctions in bamboo-like nanotubes as we spray the acetonitrile ferrocene and AgNO₃ mixture. The length of the synthesized Y-junction nanotube bundles is ~2 μm. Some more complex Ψ-shaped junctions are also found to be present. The diameters of the Y-junction nanotubes is ~80 nm at the junction and 25–50 nm at the branches.     

Bottom-up driven involuntary attention modulates auditory signal in noise processing

Background  

Auditory evoked responses can be modulated by both the sequencing and the signal-to-noise ratio of auditory stimuli. Constant sequencing as well as intense masking sounds basically lead to N1m response amplitude reduction. However, the interaction between these two factors has not been investigated so far. Here, we presented subjects tone stimuli of different frequencies, which were either concatenated in blocks of constant frequency or in blocks of randomly changing frequencies. The tones were presented either in silence or together with broad-band noises of varying levels.     

Masking of short stimuli by noises with spiked spectra: II. Time summation and frequency selectivity of hearing in a narrow frequency range

The thresholds of masking of short high-frequency pulses with either different durations (1.25–25 ms) and similar central frequency or different central frequencies (3.6–4.4 kHz) but similar durations were measured to reveal manifestations of the properties of peripheral encoding in auditory perception. Noises with a spiked amplitude spectrum structure were used as maskers. The central frequency and the frequency band of a masker were 4 and 1 kHz, respectively. The central frequencies of a stimulus and a masker being equal, the noise the central frequency of which coincided with the frequency corresponding to a dip of an indented spectrum was called an off_(rip)-frequency masker. Owing to the off_(rip)-masker, stimuli-induced masking thresholds were formed taking into account excitation in a narrow region of a basila membrane and auditory nerve fibers with characteristic frequencies from a narrow range. High-frequency pulses with an envelope in the form of the Gaussian function and sinusoidal filling were used as stimuli. At masker levels of 30 dB above the auditory threshold, frequencies of off_(rip)-masker spectra spikes of 500–2000 Hz, and a central stimulus frequency of 4 kHz, the thresholds of tonal stimuli (25 ms in duration) masking in two out of three probationers were higher than the thresholds of masking of compact stimuli (1.25 ms in duration). In the third probationer, on the contrary, the thresholds of tonal stimuli masking were lower than the thresholds of compact stimuli masking. At masker levels of 50 dB, individual threshold differences disappeared. The obtained results were interpreted in the context of implementation of different methods of auditory encoding of the intensity. The methods were based on either the average frequency of auditory nerve pulsations or the number of fibers participating in the response. The interpretation was also carried out in the context of revealing manifestations of nonlinear properties of basila membrane displacements in auditory thresholds. The fact that the dependence of detection thresholds of compact stimuli on their central frequency in one of the two probationers did not reveal the minimum in case of coincidence of off_(rip)-masker and stimulus frequencies pointed to the presence of an auditory “problem zone” that was likely to be localized at the periphery of the auditory system.     

Build-up of the tendency to segregate auditory streams: resetting effects evoked by a single deviant tone

The tendency to hear a sequence of alternating low (L) and high (H) frequency tones as two streams can be increased by a preceding induction sequence, even one composed only of same-frequency tones. Four experiments used such an induction sequence (10 identical L tones) to promote segregation in a shorter test sequence comprising L and H tones. Previous studies have shown that the build-up of stream segregation is usually reduced greatly when a sudden change in acoustic properties distinguishes all of the induction tones from their test-sequence counterparts. Experiment 1 showed that a single deviant tone, created by altering the final inducer (in frequency, level, duration, or replacement with silence) reduced reported segregation, often substantially. Experiment 2 partially replicated this finding, using changes in temporal discrimination as a measure of streaming. Experiments 3 and 4 varied the size of a frequency change applied to the deviant tone; the extent of resetting varied with size only gradually. The results suggest that resetting begins to occur once the change is large enough to be noticeable. Since the prior inducers always remained unaltered in the deviant-tone conditions, it is proposed that a single change actively resets the build-up evoked by the induction sequence.