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

EEG frequency PCA in EEG-ERP dynamics

Principal components analysis (PCA) has long been used to decompose the ERP into components, and these mathematical entities are increasingly accepted as meaningful and useful representatives of the electrophysiological components constituting the ERP. A similar expansion appears to be beginning in regard to decomposition of the EEG amplitude spectrum into frequency components via frequency PCA. However, to date, there has been no exploration of the brain's dynamic EEG-ERP linkages using PCA decomposition to assess components in each measure. Here, we recorded intrinsic EEG in both eyes-closed and eyes-open resting conditions, followed by an equiprobable go/no-go task. Frequency PCA of the EEG, including the nontask resting and within-task prestimulus periods, found seven frequency components within the delta to beta range. These differentially predicted PCA-derived go and no-go N1 and P3 ERP components. This demonstration suggests that it may be beneficial in future brain dynamics studies to implement PCA for the derivation of data-driven components from both the ERP and EEG

EEG differences between eyes-closed and eyes-open resting remain in healthy ageing

In young adults and children, the eyes-closed (EC) resting state is one of low EEG arousal, with the change to eyes-open (EO) primarily involving an increase in arousal. We used this arousal perspective to interpret EC/EO differences in healthy young and older adults. EEG was recorded from 20 young (Mage = 20.4 years) and 20 gender-matched older (Mage = 68.2 years) right-handed adults during two 3 min resting conditions; EC then EO. Older participants displayed less delta and theta, some reduction in alpha, and increased beta. Global activity in all bands reduced with opening the eyes, but did not differ with age, indicating that the energetics of EEG reactivity is maintained in healthy ageing. However, older adults had more focal changes than young adults, particularly in beta, suggesting the mobilisation of additional localised resources. This maintained reactivity, and heightened focal activity, may underlie preserved performance levels in healthy ageing

Prestimulus delta and theta contributions to equiprobable Go/NoGo processing in healthy ageing

Ongoing EEG activity contributes to ERP outcomes of stimulus processing, and each of these measures is known to undergo (sometimes significant) age-related change. Variation in their relationship across the life-span may thus elucidate mechanisms of normal and pathological ageing. This study assessed the relationships between low-frequency EEG prestimulus brain states, the ERP, and behavioural outcomes in a simple equiprobable auditory Go/NoGo paradigm, comparing these for 20 young (M age = 20.4 years) and 20 healthy older (M age = 68.2 years) adults. Prestimulus delta and theta amplitudes were separately assessed; these were each dominant across the midline region, and reduced in the older adults. For each band, (within-subjects) trials were sorted into ten increasing prestimulus EEG levels for which separate ERPs were derived. The set of ten ERPs for each band-sort was then quantified by PCA, independently for each group (young, older adults). Four components were primarily assessed (P1, N1-1, P2/N2b complex, and P3), with each showing age-related change. Mean RT was comparable, but intra-individual RT variability increased in older adults. Prestimulus delta and theta each generally modulated component positivity, indicating broad influence on task processing. Prestimulus delta was primarily associated with the early sensory processes, and theta more with the later stimulus-specific processes; prestimulus theta also inversely modulated intra-individual RT variability across the groups. These prestimulus EEG–ERP dynamics were consistent between the young and older adults in each band for all components except the P2/N2b, suggesting that across the lifespan, Go/NoGo categorisation is differentially affected by prestimulus delta and theta

Caffeine affects children’s ERPs and performance in an equiprobable go/no-go task: Testing a processing schema

Caffeine’s stimulant properties were used to test a proposed processing schema for children’s processing stages in the equiprobable auditory go/no-go task. Active control-related ERP components were hypothesized to be differentially enhanced by caffeine. Caffeine (80 mg) was administered in a counterbalanced, randomized, double-blind, placebo-controlled, cross-over study of 24 children, aged 8–12 years. Four blocks of an equiprobable auditory go/no-go task were completed on each of two occasions, while on or off caffeine. ERP data sets from each condition (caffeine/go, placebo/go, caffeine/no-go, placebo/no-go) were subjected to separate temporal PCAs with extraction and varimax rotation of all components. Caffeine significantly reduced reaction time and go omission errors, and enhanced go PN, N2c, and P3b, and no-go N1-1 and N2b. This selective enhancement of different go/no-go components by caffeine matched the predicted amplification of biomarkers of children’s active control processing in this task. Some unexpected findings also support further refinements in the child processing schema

Neurophysiological correlates of visuospatial attention and the social dynamics of gaze processing

The reflexive orienting response triggered by nonpredictive gaze cues is thought to be driven by a dedicated social neural network responsible for directing attention toward socially salient information. However, atypical processing of eye gaze using concomitant perceptual features has been proposed to underlie attentional orienting in groups with impairments in social cognition. Here, we examined the neurophysiological indices of visuospatial attention during a spatial cueing task, considering individual variability in social cognition in typically developing individuals, and the relative salience of social gaze and perceptual motion cues. We found enhanced neural activation to incongruent cues, wherein modulation of the N2b serves as a marker of the allocation of attention in the spatial domain. Our findings suggest the social gaze cue is less salient for those with greater autistic traits. An attentional bias toward perceptual motion cues correlated with greater social anxiety and alexithymia, and thus may reflect reduced sensitivity to social stimuli. These results provide evidence for likely neurophysiological mechanisms underlying gaze cueing and offer insight into the use of qualitatively different cognitive mechanisms used to access social information. Such paradigms provide potential insight into normative orienting responses reported in atypical groups and would benefit investigations of gaze following abilities in clinical populations

A processing schema for children in the auditory equiprobable Go/NoGo task : ERP components and behaviour

A sequential processing model for adults in the auditory equiprobable Go/NoGo task has been developed in recent years. This used temporal principal components analysis (PCA) to decompose Go/NoGo event related potential (ERP) data into components that mark stages of perceptual and cognitive processing. The model has been found useful in frameworking several studies in young and older adults, and in children. Recently, it has been demonstrated that the common PCA approach of decomposing Go and NoGo ERP data together results in misallocation of variance between the conditions, distorting the timing, topography, and amplitudes of the resultant components in each condition. The present study thus reanalyses data from a child study, conducting separate PCAs on the data from each condition. Multiple regression was then used to seek links with behavioural measures from the task. In addition to confirming the previous NoGo N2b/inhibitory processing link, novel NoGo Negative Slow Wave/error evaluation and Go N1-1/RT variability links were obtained. Based on these outcomes, the recommended separate application of PCAs to Go and NoGo data was confirmed. The present data were used to develop a child-specific sequential processing schema for this paradigm, suggesting earlier separation of the Go and NoGo processing chains, and the need to include an additional inhibition and evaluation stage. The child schema should be useful in future studies involving this and other two-choice reaction tasks

Sequential processing in young and older adults in the equiprobable auditory Go/NoGo task

Objective: We recently proposed a sequential processing schema for the equiprobable auditory Go/NoGo task, based on a principal components analysis (PCA) of event-related potentials (ERPs) from a university student sample. Here we sought to replicate the schema, and use it to explore processing in well-functioning older adults. Methods: We compared behavioural responding and ERPs of 20 independent-living older adults (Mage = 68.2 years) to data from a sex- and handedness-matched group of university students (Mage = 20.4 years). ERPs had substantial latency differences between the groups, and hence were subjected to separate group temporal PCAs. Results: Component latencies were systematically increased in the older group by some 26%, with no significant increase in RT or error rates. Despite some differences in their identified components, each group displayed differential component responsivity to Go versus NoGo; this was reduced in the older participants. Conclusion: The results support our processing schema, and provide insight into the processing stages in well-functioning older adults. Significance: Understanding the perceptual and cognitive processing stages in normal ageing is a pre-requisite for research on mild cognitive impairment and dementia. This study may also provide a simple paradigm and schema suitable for further exploration of functionality in ageing. © 2016 International Federation of Clinical Neurophysiology

Caffeine effects on ERP components and performance in an equiprobable auditory Go/NoGo task

Background: Research has reliably demonstrated that caffeine produces a general increase in physiological arousal in humans, but we previously failed to obtain the expected arousal-based changes in manually quantified event-related potential (ERP) components in response to the stimuli in a simple Go/NoGo task. Methods: A single oral dose of caffeine (250 mg) was used in a randomized double-blind placebo-controlled repeated-measures cross-over study. Adult participants (N=24) abstained from caffeine for 4 hours before each of two sessions, approximately 1 week apart. An equiprobable auditory Go/NoGo task was used, with a random mix of 75 tones at 1,000 Hz and 75 at 1,500 Hz. All tones were 50 ms duration (rise/fall time 5 ms) at 60 dB SPL, with a fixed stimulus-onset asynchrony of 1100 ms. Principal component analysis (a form of factor analysis) was used to quantify orthogonal ERP components. Results: ERP components reflected the different sequential processing of each stimulus type in this paradigm, replicating previous results. Caffeine was associated with a reduction in reaction time and fewer omission errors. The major ERP effects of caffeine were apparent as a slightly enhanced Processing Negativity and larger P3b amplitudes to Go stimuli. There were few effects on components to NoGo stimuli. Conclusions: The results confirm our previous findings that caffeine improves aspects of the differential processing related to response production and task performance, but may be interpreted as supporting the simple amplification of ERP component amplitudes predicted by the general arousal induced by caffeine

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

Some 40 years ago, Erol Başar 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