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A novel slow‐wave half‐mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) is proposed based on spoof surface plasmon polaritons (SSPPs) with loading capacitive patches (LCPs). The bandpass characteristics are achieved by etching complementary SSPPs on the metal patches of the HMSIW. SSPPs exhibit a slow‐wave effect, which effectively reduces the overall size of the filter. At the same time, using proper LCPs between the HMSIW metal via and the complementary SSPPs structure, the effective dielectric constant of the HMSIW can be changed, reducing the low cutoff frequency and further facilitating the miniaturisation of size. A prototype of the proposed filter is designed, fabricated, and measured. The measured results show that the proposed filter has the in‐band insertion loss of 1 and 3 dB passband range of 6.4–9.8 GHz. [ABSTRACT FROM AUTHOR]

Abstract A novel slow‐wave half‐mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) is proposed based on spoof surface plasmon polaritons (SSPPs) with loading capacitive patches (LCPs). The bandpass characteristics are achieved by etching complementary SSPPs on the metal patches of the HMSIW. SSPPs exhibit a slow‐wave effect, which effectively reduces the overall size of the filter. At the same time, using proper LCPs between the HMSIW metal via and the complementary SSPPs structure, the effective dielectric constant of the HMSIW can be changed, reducing the low cutoff frequency and further facilitating the miniaturisation of size. A prototype of the proposed filter is designed, fabricated, and measured. The measured results show that the proposed filter has the in‐band insertion loss of 1 and 3 dB passband range of 6.4–9.8 GHz.

Gap waveguide (GW) technology, taking advantage of contactless electromagnetic band-gap (EBG) structures, solves the contact issue of conventional rectangular waveguides and provides a reliable method for packaging with planar circuits. Herein, a slow wave GW (SW-GW) structure with bandpass filtering functionality is presented. Utilizing the low-frequency cutoff characteristic of the GW and band-stop effect of the quasi-periodic transverse corrugations inside the GW, the lower and upper stopbands of the SW-GW can be easily achieved and reconfigured for different bandwidth requirements. The relationship between the dispersion diagram and the filtering characteristics, including the pass and stop bandwidths and group delay (GD), is studied to provide a simple but effective design guideline. The presented SW-GW reduces the design and implementation difficulties of conventional filters, especially wideband filters. A prototype operating at 24–30 GHz is designed and manufactured to validate the idea, and a good agreement is achieved between the measurement and simulation results. [ABSTRACT FROM AUTHOR]

A novel slow wave (SW) substrate-integrated waveguide (SIW) with enhanced SW factor (SWF) and broadened bandwidth is proposed by simultaneously increasing the effective permeability and permittivity. The effective permittivity is increased by the enhanced capacitance between the top plane of the waveguide and the loaded patches which are shorted to the SIW bottom plane by the blind via-holes. The effective permeability is increased by lengthening the current path by adding patches on the blind via-holes. The proposed SW-SIW with simultaneous increased effective permeability and permittivity has two obvious advantages over the reported SW-SIW with only effective permeability or permittivity increased: 1) smaller longitudinal and lateral dimensions resulted from higher SWF and lower cutoff frequency, respectively, and 2) wider bandwidth due to stable wave impedance along the periodical SW structure. The lateral dimension of the proposed SW-SIW is decreased by 53% compared with the normal SIW with the same cutoff frequency. The phase velocity is decreased by 73%, which means the longitudinal length is reduced by 73% consequently. The operation band is 7.0–18.8 GHz (91.5% fractional bandwidth) covering X- and Ku-bands. A prototype of the proposed SW-SIW is manufactured and measured, and the measured results agree well with the simulations. [ABSTRACT FROM AUTHOR]

This study investigated stimulus‐response patterns of temporal principal components analysis (PCA)–derived event‐related potential (ERP) components in a classical auditory habituation paradigm with long interstimulus intervals. The skin conductance response (SCR) was included as the "gold standard" model of the Orienting Reflex. Thirty participants were presented with a single series of 10 identical 60 dB tones, followed by a change trial at a different frequency. Single‐trial, electrooculography‐corrected ERPs were submitted to temporal PCA. The main focus was on the components expected in the P300/Late Positive Complex (LPC), and their electromagnetic tomography–derived cortical sources. Nine components were identified between 90 and 470 ms poststimulus (in temporal order): three N1 subcomponents, P2, four LPC components, and a negative Slow Wave (SW). The expected order of P3a, P3b, Novelty P3 (nP3), and positive Slow Wave (+SW) in the LPC was confirmed. SCR demonstrated strong exponential decay and recovery. P3b and nP3 each showed exponential decrement over trials, but only nP3 showed recovery at the change trial. Novelty effects failed to reach significance for the other LPC components, and were not apparent in non‐LPC components. Frontal lobe activity in Brodmann areas 6, 8, and 9 was common to P3a, P3b, nP3, and +SW, consistent with the functional integration of these components in the LPC. Individual components had specific sources, although some sources overlapped between components or were reactivated later in the LPC. These data provide a fresh perspective on the components of the LPC and their cortical sources, and offer a processing model for the P300 in a habituation task, potentially generalizable to other paradigms. We explored the component structure of the P300, recording single‐trial ERPs from a classical long‐ISI single‐series habituation task, and decomposing them with temporal PCA. SCR was recorded as a model Orienting Reflex (OR) marker of novelty. We confirmed P3a, P3b, Novelty P3 (nP3), and SW within the P300 and estimated their cortical sources via eLORETA. Only nP3, the relatively forgotten member of the P3 family, was sensitive to novelty. Based on the temporal characteristics of the factor loadings, we propose an ordered sequence of Brodmann area activations for P300 in habituation tasks; this should be generalizable to other paradigms [ABSTRACT FROM AUTHOR]

Previous research has shown that as the stimulus-to-matching-stimulus interval (including the target-to-target interval, TTI, and nontarget-to-nontarget interval, NNI) increases, the amplitude of the P300 ERP component increases systematically. Here, we extended previous P300 research and explored TTI and NNI effects on the various ERP components elicited in an auditory equiprobable Go/NoGo task. We also examined whether a similar mechanism was underpinning interval effects in early ERP components (e.g., N1). Thirty participants completed a specially-designed variable-ISI equiprobable task whilst their EEG activity was recorded. Component amplitudes were extracted using temporal PCA with unrestricted Varimax rotation. As expected, N1, P2, and P3b amplitudes increased as TTI and NNI increased, however, Processing Negativity (PN) and Slow Wave (SW) did not show the same systematic change with interval increments. To determine the origin of interval effects in sequential processing, a multiple regression analysis was conducted on each ERP component including stimulus type, interval, and all preceding components as predictors. These analyses showed that matching-stimulus interval predicted N1, P3b, and weakly predicted P2, but not PN or SW; SW was determined by P3b only. These results suggest that N1, P3b, and to some extent, P2, are affected by a similar temporal mechanism. However, the dissimilar pattern of results obtained for sequential ERP components indicates that matching-stimulus intervals are not affecting all aspects of stimulus processing. This argues against a global mechanism, such as a pathway-specific refractory effect, and suggests that stimulus processing is occurring in parallel pathways, some of which are not affected by temporal manipulations of matching-stimulus interval. [ABSTRACT FROM AUTHOR]

Abstract: Increases in the target-to-target interval (TTI) systematically enhance the amplitude of the target P300 ERP component. Research examining changes in nontarget P300 related to nontarget-to-nontarget interval (NNI) or sequential probability manipulations has produced inconsistent results, with some studies reporting no enhancement in nontarget P300 and others finding response profiles analogous to TTI effects. Our aim was to clarify these differences. All participants completed a specially designed auditory equiprobable Go/NoGo task with manipulations of TTI and NNI while their EEG activity was recorded. P300 amplitudes were extracted using temporal PCA with Varimax rotation. P3b to targets and nontargets increased systematically as respective TTIs/NNIs increased, but this change did not differ between stimulus types. The Slow Wave did not show any effect of interval, but was more positive to targets than nontargets when interval was collapsed. P3b findings show that matching-stimulus interval effects are not restricted to targets, but discrepancies relative to previous research suggest that NNI effects in P3b may depend on additional processing of nontarget stimuli. [Copyright &y& Elsevier]

Abstract: It has been suggested that the P300 component of the ERP is an electrophysiological index of memory-updating processes associated with task-relevant stimuli. Component magnitude varies with the time separating target stimuli (target-to-target interval: TTI), with longer TTIs eliciting larger P300 amplitudes. According to the template-update perspective, TTI effects observable in the P300 reflect the updating of stimulus-templates in working memory (WM). The current study explored whether young adults' memory-task ability could predict TTI effects in P300. EEG activity was recorded from 50 university students (aged 18–25years) while they completed an auditory equiprobable Go/NoGo task with manipulations of TTIs. Participants also completed a CogState® battery and were sorted according to their WM score. ERPs were analysed using a temporal PCA. Two P300 components, P3b and the Slow Wave, were found to linearly increase in amplitude to longer TTIs. This TTI effect differed between groups only for the P3b component: The high WM group showed a steeper increase in P3b amplitude with TTI than the low WM group. These results suggest that TTI effects in P300 are directly related to WM processes. [Copyright &y& Elsevier]

To disentangle subprocesses of verbal working memory deficits in schizophrenia, long EEG epochs (>10 s) were recorded from 13 patients and 17 healthy adults during a visual word serial position test. ERP generator patterns were summarized by temporal PCA from reference-free current source density (CSD) waveforms to sharpen 31-channel topographies. Patients showed poorer performance and reduced left inferior parietotemporal P3 source. Build-up of mid-frontal negative slow wave (SW) in controls during item encoding, integration, and active maintenance was absent in patients, whereas a sustained mid-frontal SW sink during the retention interval was comparable across groups. Mid-frontal SW sinks (encoding and retention periods) and posterior SW sinks and sources (encoding only) were related to performance in controls only. Data suggest disturbed processes in a frontal-parietotemporal network in schizophrenia, affecting encoding and early item storage. [ABSTRACT FROM AUTHOR]

The adenosine agonist cyclohexaladenosine injected into the medial pontine reticular formation of the rat induces a long-lasting increase in rapid eye movement sleep. To investigate the adenosine receptor-subtype(s) mediating this effect, the dose-response relationships for increasing rapid eye movement sleep by two highly selective adenosine receptor agonists were compared. Rats were surgically prepared for chronic sleep recording and bilateral guide cannulae were aimed at medial sites in the caudal, oral pontine reticular formation. Injections were made unilaterally in 60 nl volumes within 1 h after lights-on. The adenosine agonists used were A1-selective cyclohexaladenosine (10−6−10−4 M) and A2a-selective CGS 21680 (10−7−10−3 M). Each animal also received a series of three, paired-consecutive injections of the muscarinic receptor antagonist atropine (4×10−3 M) followed by the lowest effective dose of each agonist or saline as control. The A2a receptor agonist, CGS 21680, was one order of magnitude more potent than the A1 receptor agonist, cyclohexaladenosine, in inducing rapid eye movement sleep increases. Preinjection of atropine at a dose that did not itself affect rapid eye movement sleep resulted in antagonism of CGS 21680, but not cyclohexaladenosine-induced rapid eye movement sleep.The differential sensitivity of these ligands to antagonism by atropine supports the conclusion that both A1 and A2a adenosine receptor subtypes in the reticular formation subserve agonist-induced rapid eye movement sleep and that they do so by independent mechanisms. The A2a mechanism requires the cholinergic system and may act through the increased release of acetylcholine. The A1 mechanism operates at a different locus possibly through an inhibition of GABA neurotransmission. [Copyright &y& Elsevier]

The effects of inter-stimulus intervals on P300 from an oddball task (target and standard stimuli) and a single-stimulus task (targets only) employing simple visual stimuli were assessed in order to determine how a relatively long ISI affects event-related brain potentials (ERPs). Young adult subjects (n=16) responded by pressing a button to a visual target stimulus of each task condition. ISI was either 2.5 or 30 s and paradigm type was either the oddball or single-stimulus task. ERPs were recorded from the midline electrodes, with amplitude, mean area, and latency of the P300 and other components assessed. The results showed that P300 morphology was dramatically affected by task and ISI such that under the 2.5 s condition, the oddball paradigm produced typical ERP components, whereas the single-stimulus condition demonstrated minimal P300 amplitude. When ISI was 30 s, both the oddball and single-stimulus tasks produced robust P300 components but also evinced strong slow wave (SW) potentials, which contributed to the ERP measurement outcomes. It is concluded that P300 from visual stimuli can be elicited with both oddball and single-stimulus tasks when ISI is relatively long. ERPs from both paradigms produced appreciable SW activity, which needs to be considered when long ISI procedures are employed. [Copyright &y& Elsevier]