Electrodermal and central measures of the tonic orienting reflex (OR).

Sokolov described both phasic and tonic aspects of the Orienting Reflex (OR), but subsequent research and theory development has focussed primarily on the phasic OR at the expense of the tonic OR. The present study used prestimulus skin conductance level (SCL) during a dishabituation paradigm to model the tonic OR, examining its amplitude patterning over repeated standard stimulus presentations and a change stimulus. We expected sensitisation (increased amplitude) following the initial and change trials, and habituation (decrement) over the intervening trials. Prestimulus EEG alpha level was explored as a potential central measure of the tonic OR (as an inverse correlate), examining its pattern over stimulus repetition and change in relation to the SCL model. We presented a habituation series of innocuous auditory stimuli to two groups (each N = 20) at different ISIs (Long 13-15 s and Short 5-7 s) and recorded electrodermal and EEG data during two counterbalanced conditions; Indifferent: no task requirements; Significant: silent counting. Across groups and conditions, prestimulus SCLs and alpha amplitudes generally showed the expected trials patterns, confirming our main hypotheses. Findings have important implications for including the assessment of Sokolov's tonic OR in modelling central and autonomic nervous system interactions of fundamental attention and learning processes.

A randomized, double-blind, placebo-controlled, parallel-group 12-week pilot phase II trial of SaiLuoTong (SLT) for cognitive function in older adults with mild cognitive impairment.

INTRODUCTION: This study primarily aimed to evaluate the efficacy and safety of SaiLuoTong (SLT) on cognition in mild cognitive impairment (MCI). METHODS: Community-dwelling people with MCI aged ≥60 years were randomly assigned to 180 mg/day SLT or placebo for 12 weeks. RESULTS: Thirty-nine participants were randomized to each group (N = 78); 65 were included in the final analysis. After 12 weeks, the between-groups difference in Logical Memory delayed recall scores was 1.40 (95% confidence interval [CI]: 0.22 to 2.58; P = 0.010); Delis-Kaplan Executive Function System Trail Making Test Condition 4 switching and contrast scaled scores were 1.42 (95% CI: -0.15 to 2.99; P = 0.038) and 1.56 (95% CI: -0.09 to 3.20; P = 0.032), respectively; Rey Auditory Verbal Learning Test delayed recall was 1.37 (95% CI: -0.10 to 2.84; P = 0.034); and Functional Activities Questionnaire was 1.21 (95% CI: -0.21 to 2.63; P = 0.047; P < 0.001 after controlling for baseline scores). DISCUSSION: SLT is well tolerated and may be useful in supporting aspects of memory retrieval and executive function in people with MCI. Highlights: SaiLuoTong (SLT) improves delayed memory retrieval and executive function in people with mild cognitive impairment (MCI).SLT is well tolerated in people ≥ 60 years.The sample of community dwellers with MCI was well characterized and homogeneous.

Effects of interstimulus interval and significance on electrodermal and central measures of the phasic orienting reflex (OR) in a dishabituation task.

Although the P300 event-related potential (ERP) is the most likely central measure of Sokolov's Orienting Reflex (OR), there are few systematic comparisons with the skin conductance response (SCR), the "gold standard" electrodermal OR measure. We examine habituation, stimulus significance, and inter-stimulus interval (ISI) effects in SCRs and components of the P300 from single-trial ERPs in an auditory dishabituation paradigm. Single trial ERP components were separated by temporal principal components analysis, and five components of the P300 were examined as potential phasic OR measures: P3a, P3b, Novelty P3, and two Slow Waves (SW1, SW2). Across the factors of ISI and significance, SCRs showed decrement over trials, recovery at a deviant, and dishabituation at the subsequent standard. This general pattern was not present in any of the components of the P300. SCRs were also larger to significant stimuli and at the long ISI; effects differed between P300 components. The electrodermal SCR showed the complete profile over trials expected of the phasic OR, and was enhanced by stimulus significance, confirming it as the model measure of Sokolov's phasic OR. Components of the P300 failed to match this profile, but instead appear to reflect different aspects of the stimulus processing involved in OR elicitation.

Frontocentral delta-beta amplitude coupling in endometriosis-related chronic pelvic pain.

OBJECTIVE: Endometriosis is associated with neuroplastic changes in cognitive control and pain processing networks. This was the first study to assess eyes-closed resting electroencephalogram (EEG) oscillatory amplitudes in women with endometriosis compared to healthy controls, and explore the relationship with chronic pelvic pain. METHODS: Women with endometriosis-related chronic pelvic pain and individually age-matched pain-free controls (N = 20 per group) documented pelvic pain for 28 days before having continuous EEG recorded during a 2 min eyes closed resting state. Natural frequency components were extracted for each group using frequency principal components analysis. Corresponding components were assessed for group differences and correlated with pain scores. RESULTS: Relative to controls, the endometriosis group had greater component amplitudes in delta (0.5 Hz) and beta (∼28 Hz), and reduced alpha (∼10 Hz). Delta and beta amplitudes were positively associated with pain severity, but only beta maintained this association after delta-beta amplitude coupling was controlled. CONCLUSIONS: Enhanced resting delta and beta amplitudes were seen in women with endometriosis experiencing chronic pelvic pain. This delta-beta coupling varied with pelvic pain severity, perhaps reflecting altered cholinergic tone and/or stress reactivity. SIGNIFICANCE: Endometriosis-related changes in central pain processing demonstrate a distinct neuronal oscillatory signature detectable at rest.

The Effects of Concentrative Meditation on the Electroencephalogram in Novice Meditators.

Following investigations into the benefits of meditation on psychological health and well-being, research is now seeking to understand the mechanisms underlying these outcomes. This study aimed to identify natural alpha and theta frequency components during eyes-closed resting and concentrative meditation states and examined their differences within and between two testing sessions. Novice meditators had their EEG recorded during eyes-closed resting and concentrative meditation conditions, before and after engaging in a brief daily concentrative meditation practice for approximately one-month. Separate frequency Principal Components Analyses (f-PCA) yielded four spectral components of interest, congruent between both conditions and sessions: Delta-Theta-Alpha, Low Alpha, High Alpha, and Alpha-Beta. While all four components showed some increase in the meditation condition at the second session, only Low Alpha (∼9.5-10.0 Hz) showed similar increases while resting. These findings support the use of f-PCA as a novel method of data analysis in the investigation of psychophysiological states in meditation.

The effect of tDCS electrode montage on attention and working memory.

The effects of transcranial direct current stimulation (tDCS) for improving attention and working memory have been generally mixed and small, potentially due to variability between studies with montages, stimulus parameters and outcome measures. The tDCS montage is an important parameter which determines the degree and intensity of stimulation in targeted brain regions. This study aimed to examine the effects of using three different montages for modulating attention and working memory performance: Bi-frontal, Broad-frontal and Broad-parietal. Ninety-three healthy adults participated in a counterbalanced cross-over study. Participants received both active and sham tDCS with either the Bi-frontal, Broad-frontal or Broad-parietal montage during performance of both a 1- and 2-back task. TDCS montage moderated 2-back working memory reaction time performance, though not accuracy, with faster reaction times observed for active compared to sham tDCS with the Broad-frontal montage only (F (1,90) = 5.26, p = .024, η2 = 0.06). TDCS montage did not significantly moderate performance on the 1-back task. The cognitive effects of tDCS varied according to montage, task, and outcome measure. TDCS administered with the cathode placed extracephalically in a Broad-frontal montage may be beneficial for improving working memory.

Data-Driven EEG Theta and Alpha Components Are Associated with Subjective Experience during Resting State.

The resting-state paradigm is frequently applied to study spontaneous activity of the brain in normal and clinical conditions. However, the relationship between the ongoing experience of mind wandering and the individual biological signal is still unclear. We aim to estimate associations between subjective experiences measured with the Amsterdam Resting-State Questionnaire and data-driven components of an electroencephalogram extracted by frequency principal component analysis (f-PCA). Five minutes of resting multichannel EEG was recorded in 226 participants and six EEG data-driven components were extracted-three components in the alpha range (peaking at 9, 10.5, and 11.5 Hz) and one each in the delta (peaking at 0.5 Hz), theta (peaking at 5.5 Hz) and beta (peaking at 17 Hz) ranges. Bayesian Pearson's correlation revealed a positive association between the individual loadings of the theta component and ratings for Sleepiness (r = 0.200, BF10 = 7.676), while the individual loadings on one of the alpha components correlated positively with scores for Comfort (r = 0.198, BF10 = 7.115). Our study indicates the relevance of assessments of spontaneous thought occurring during the resting-state for the understanding of the individual intrinsic electrical brain activity.

Child sex differences in the auditory equiprobable Go/NoGo task.

Our previous studies of the equiprobable auditory Go/NoGo task have been used to substantiate a perceptual/cognitive Processing Schema in young and older adults, and in children. The processes in the Schema are linked to PCA components derived separately from Go and NoGo ERPs. Here we investigated sex differences in the child Schema. Two groups of fourteen children (aged 8 to 13 years) were individually matched on age and presented with four stimulus blocks of the equiprobable Go/NoGo task, each containing 75 NoGo and 75 Go tones in random order. Separate NoGo and Go ERPs were obtained from each child and submitted to temporal Principal Components Analyses (PCAs). Each ERP was analysed in two epochs (-100-400 ms and 300-800 ms) to improve the cases:variables ratio. Four pairs of temporal PCAs, each with unrestricted VARIMAX rotation, separately quantified the NoGo and Go ERPs of each epoch in each group. After these pairs were combined in temporal order, four sets of similar components were extracted. Many identified components were differentially enhanced to either NoGo or Go, as in previous work with children. The Female group had NoGo component latencies that were systematically some 3.5% greater than in Males, but there were no sex differences in Go latencies. Females also displayed fewer NoGo commission and Go omission errors, and faster Go RT than Males. Females had larger NoGo N2b, and larger Go components from N2b through to the late positivity. These results, including their ERP component/behaviour correlations, can be integrated as a task-specific behavioural and ERP processing enhancement in girls that suggests their developmental advantage over boys in this age range.

Stimulus intensity effects and sequential processing in the passive auditory ERP.

Auditory stimulus intensity of innocuous tones is generally thought to have a direct effect on the amplitude of ERP components, but these effects have rarely been explored across a wide component range, or in multiple paradigms. Here we investigate component sensitivity to stimulus intensity differences in two studies. Study 1 (N = 36) employed a between-participants paradigm in which repeated trains of standard stimuli were presented as 50 or 80 dB SPL 1000 Hz tones. Study 2 (N = 18) used a within-participant presentation of alternating 60 and 80 dB SPL 1000 Hz tones. Electrode caps with 19 channels (referred to linked ears) generated ERPs covering the first 600 ms of each participant's EEG responses; these were submitted to separate temporal PCAs in each study. A similar series of components was obtained in each study: P1, N1a, N1b, N1c, P2, P3a, P3b, nP3, SW1, and SW2; an N2 was found in Study 2 only. Loud tones in Study 1 produced greater amplitudes in all components except SW1. In Study 2, Loud cf. Soft tones produced smaller P1 and nP3, larger N1 components, P2, and P3a, with no effect on N2, P3b, SW1 or SW2. These results indicate similar sequential processes underlying sensory processing in one- and two-stimulus paradigms, with the later stimulus intensity effects varying with paradigm.

Development of children's performance and ERP components in the equiprobable Go/NoGo task.

Since the equiprobable Go/NoGo task lacks the dominant Go imperative of the usual Go/NoGo (with more Go than NoGo stimuli), it is generally regarded as involving little inhibition. However, children have relative difficulty with this task, and have a large frontal NoGo N2. We previously found that this 'child N2' does play an inhibitory role, with larger frontal N2b associated with fewer commission errors. Here we investigated age-related developmental differences in the N2b and other components in the equiprobable Go/NoGo task. Two groups of eighteen Younger children (aged 8.0 to 10.3 years) and eighteen Older children (aged 10.4 to 12.8 years), matched on sex, were presented with three stimulus blocks each containing 100 Go and 100 NoGo tone stimuli in random order. Four temporal PCAs, each with unrestricted VARIMAX rotation, separately quantified the Go and NoGo ERPs of each group, and similar components were extracted from each set. Most identified components were differentially enhanced to either Go or NoGo, as in adults, supporting a previously-proposed differential sequential processing schema. The Older group had Go component latencies that were systematically reduced by some 7.4% from the Younger group, and they displayed faster RT and fewer omission and commission errors. Between subjects in the Older group, larger frontocentral NoGo N2b was associated with fewer commission errors. Hence the NoGo N2b in this paradigm can be interpreted as an individual marker of inhibition in older, but not young, children.

Characterizing pink and white noise in the human electroencephalogram.

Objective.The power spectrum of the human electroencephalogram (EEG) as a function of frequency is a mix of brain oscillations (Osc) (e.g. alpha activity around 10 Hz) and non-Osc or noise of uncertain origin. 'White noise' is uniformly distributed over frequency, while 'pink noise' has an inverse power-frequency relation (power ∝ 1/f). Interest in EEG pink noise has been growing, but previous human estimates appear methodologically flawed. We propose a new approach to extract separate valid estimates of pink and white noise from an EEG power spectrum.Approach.We use simulated data to demonstrate its effectiveness compared with established procedures, and provide an illustrative example from a new resting eyes-open (EO) and eyes-closed (EC) dataset. The topographic characteristics of the obtained pink and white noise estimates are examined, as is the alpha power in this sample.Main results.Valid pink and white noise estimates were successfully obtained for each of our 5400 individual spectra (60 participants × 30 electrodes × 3 conditions/blocks [EO1, EC, EO2]). The 1/fnoise had a distinct central scalp topography, and white noise was occipital in distribution, both differing from the parietal topography of the alpha Osc. These differences point to their separate neural origins. EC pink and white noise powers were globally greater than in EO.Significance. This valid estimation of pink and white noise in the human EEG holds promise for more accurate assessment of oscillatory neural activity in both typical and clinical groups, such as those with attention deficits. Further, outside the human EEG, the new methodology can be generalized to remove noise from spectra in many fields of science and technology.

tDCS effects on task-related activation and working memory performance in traumatic brain injury: A within group randomized controlled trial.

Non-invasive transcranial direct current stimulation (tDCS) has been reported to facilitate working memory in normal adults. There is some evidence in people with Traumatic Brain Injury (TBI) but overall evidence is mixed. This study aimed to address shortcomings of prior study designs in TBI to examine whether a single dose of tDCS would lead to benefits in working memory. Thirty people with severe, chronic TBI were administered a single session of either anodal tDCS (2 mA for 20 min) or sham tDCS (2 mA for 30 s), in a counterbalanced order, over the left parietal cortex while performing 1-back and 2-back working memory tasks. Skin conductance levels were examined as a measure of task activated arousal, a possible functional analogue of cortical excitability. We found that tDCS led to no improvements in accuracy on the working memory tasks. A slight increase in variability and reaction time with tDCS was related to decreased task activated arousal. Overall, this study yielded no evidence that a single session of tDCS can facilitate working memory for people with TBI.

Caffeine as a Tool to Explore Active Cognitive Processing Stages in Two-Choice Tasks.

Background: We used caffeine as a tool to explore the active cognitive-processing stages in a simple Go/NoGo task, in terms of the event-related potential (ERP) components elicited by the Go and NoGo stimuli. Methods: Two hundred and fifty milligrams of caffeine was administered to adult participants (N = 24) in a randomized double-blind placebo-controlled repeated-measures crossover study. Two blocks of an equiprobable auditory Go/NoGo task were completed, each with a random mix of 75 tones at 1000 Hz and 75 at 1500 Hz, all 60 dB sound pressure level (SPL). Results: Major ERP effects of caffeine were apparent in enhancements of the Go N1-1, P3b, and Slow Wave (SW), and the NoGo Processing Negativity, SW, and NoGo Late Positivity. Conclusions: Novel differential findings indicate the potential of our caffeine as a tool approach to elucidate the functional nature of ERP markers of active cognitive processing in a range of developmental and clinical populations.

Prestimulus alpha and beta contributions to equiprobable Go/NoGo processing in healthy ageing.

The immediately-prestimulus electroencephalographic (EEG) brain state influences subsequent event-related processing, dynamically impacting event-related potential (ERP) and behavioural outcomes. Both EEG and ERPs are known to undergo age-related change, yet few have investigated the consistency in their dynamic interrelations in the context of ageing. The present investigation assessed the impact of prestimulus alpha and beta brain states in 20 young (18-26 years) and 20 gender-matched healthy older (59-75 years) adults who completed an equiprobable auditory Go/NoGo paradigm. Prestimulus alpha and beta band amplitudes in their prominent band topographies were separately used to derive Go and NoGo ERPs at 10 ascending levels of prestimulus activity, and ERP components were derived for these levels using Principal Components Analysis. Prestimulus alpha directly modulated Go/NoGo P3a amplitudes across the groups, while beta inversely modulated the young (cf. older) adult NoGo N1-1, each supporting and extending limited prior research. Several novel effects were also uncovered, most notably an inverse relationship between prestimulus alpha and reaction time. Prestimulus alpha and beta were confirmed as significant determinants of the processing outcomes in this task, and the complex pattern of results provides a normative map in healthy ageing.

Preferred EEG brain states at stimulus onset in normal ageing: Explorations in a fixed interstimulus interval Go/NoGo task.

Some 40 years ago, Erol Basar began an interesting line of brain dynamics research on the phase of oscillatory EEG activity. Stimuli presented at a fixed interstimulus interval (ISI) were reported to produce a "preferred phase angle" at stimulus onset in the ongoing EEG oscillations, so that cortical negativity occurred more often than expected. Our previous work has confirmed this phenomenon in young adults, and linked it to enhancements in stimulus-elicited ERP components and behaviour. The present study sought evidence for this phenomenon in older adults. Twenty healthy independent-living participants (5 males) aged 59.8 to 74.8 years (M = 68.2) completed a fixed ISI equiprobable auditory oddball task. EEG phases in four traditional bands were computed separately for each artefact-free Go and NoGo trial. These were used to group accepted trials according to the phase quartile at stimulus onset in each band, forming 16 mean ERPs for each participant at each phase quartile/band combination, separately for Go and NoGo. The 32 mean ERPs were decomposed by separate Principal Component Analyses, and the N1 and P3 components were examined as a function of EEG phase at stimulus onset in each band. Differential preferential occurrence of phase states was found in all bands, generally confirming prior results in young adults despite important age differences in both EEG spectra and ERP morphology. Substantial effects on N1 and P3 components, as well as prestimulus CNVs, are discussed. The stability of this phenomenon across age indicates its important role in perception and cognition.

Components in the P300: Don't forget the Novelty P3!

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.

Neuronal Correlates of Cognitive Control Are Altered in Women With Endometriosis and Chronic Pelvic Pain.

Endometriosis is a debilitating women's health condition and is the most common cause of chronic pelvic pain. Impaired cognitive control is common in chronic pain conditions, however, it has not yet been investigated in endometriosis. The aim of this study was to explore the neuronal correlates of cognitive control in women with endometriosis. Using a cross-sectional study design with data collected at a single time-point, event-related potentials were elicited during a cued continuous performance test from 20 women with endometriosis (mean age = 28.5 ± 5.2 years) and 20 age- and gender-matched controls (mean age = 28.5 ± 5.2 years). Event-related potential components were extracted and P3 component amplitudes were derived with temporal principal components analysis. Behavioral and ERP outcomes were compared between groups and subjective pain severity was correlated with ERP component amplitudes. No significant behavioral differences were seen in task performance between the groups (all p > 0.094). Target P3b (all p < 0.034) and SW (all p < 0.040), and non-target early P3a (eP3a; all p < 0.023) and late P3a (lP3a; all p < 0.035) amplitudes were smaller for the endometriosis compared to the healthy control group. Lower non-target eP3a (p < 0.001), lP3a (p = 0.013), and SW (p = 0.019) amplitudes were correlated with higher pain severity scores. Findings suggest that endometriosis-associated chronic pelvic pain is linked to alterations in stimulus-response processing and inhibitory control networks, but not impaired behavioral performance, due to compensatory neuroplastic changes in overlapping cognitive control and pain networks.

Natural alpha frequency components in resting EEG and their relation to arousal.

OBJECTIVE: Global EEG alpha activity is negatively correlated with skin conductance level (SCL), supporting alpha as an inverse marker of arousal. Frequency Principal Components Analysis (f-PCA) of resting EEG amplitude spectra has demonstrated natural components in the alpha band of healthy persons. This is a preliminary exploration of whether such components differ with arousal, possibly underpinning the anomalous ADHD hypoarousal link to reduced alpha. METHOD: Twenty-seven right-handed undergraduate students participated in three 2 minute blocks of resting eyes-open/closed EEG and SCL: EO1, EC, EO2. For each condition, mean EEG spectra were submitted to separate f-PCAs. RESULTS: The inverse alpha/SCL relationship was confirmed for band amplitudes. EO had two alpha components; both correlated negatively with SCL. EC alpha contained four components, but only one had a substantial negative correlation with SCL; two had no relationship, suggesting natural alpha components with different non-arousal functionality in EC. CONCLUSION: Some alpha components in both EC and EO reflect arousal, with other non-arousal components in EC. Our f-PCA approach offers insight into previously-noted alpha anomalies in disorders such as ADHD. SIGNIFICANCE: This proof of concept demonstration in typical participants may provide the basis for a new research effort in clinical disorders involving atypical arousal patterns.

EEG-ERP dynamics in a visual Continuous Performance Test.

Brain dynamics research has highlighted the contributions of the ongoing EEG to ERP and behavioural responses. This study examined the effects of state-related EEG changes, from rest to the task and within the task, on stimulus-response efforts in a visual Continuous Performance Test (CPT). EEG was recorded from fifty-six adults at rest with eyes-closed (EC) then eyes-open (EO), and during the CPT. Principal Components Analyses decomposed the EEG obtained from EC, EO and the task-based periods immediately pre-cue (PC) and pre-imperative (PI), and the ERPs to the cued Go/NoGo imperatives. EC amplitudes were correlated with Go/NoGo ERP amplitudes and behavioural outcomes. EEG amplitude changes from EO to PC, and from PC to PI, were assessed as predictors of these response measures. Longer mean reaction time (RT) was associated with greater RT variability (RTV) and reduced Go P2. The two EC alpha components correlated positively with RTV, and NoGo P1 and P2 positivity. Delta/theta amplitude reductions from PC to PI predicted Go N1-1 and NoGo N2b enhancements. Alpha-1 decreases from PC to PI predicted larger P2 and poorer NoGo accuracy rates, while alpha-3 decrements positively predicted NoGo P1. These findings highlight the ongoing alpha arousal effects on stimulus-response efforts, and the low frequency shifts in the cue to imperative interval associated with stimulus anticipation and response preparation. These relationships offer novel insights into the effects of pretask EEG activity, and within-task EEG changes, on attention and cognitive control processes.