Frances M. De Blasio

Sequential processing in the equiprobable auditory Go/NoGo task: A temporal PCA study

The unwarned auditory equiprobable Go/NoGo task provides a convenient means to assess differential processing, although our interpretations remain limited by the lack of research regarding the range of elicited components and their functional significance. We examined sequential processing in this paradigm, presenting 24 participants with a total of 300 trials in two blocks. EEG was recorded from 19 channels, and the Go and NoGo event-related potentials were decomposed using temporal Principal Components Analysis. Of the 218 unrestricted Varimax-rotated factors, seven were identifiable as components based on their latency, polarity, and topography: early N1, Processing Negativity (PN), and P2 components were followed by N2, P3, the classic Slow Wave (SW), and a diffuse Late Positivity (LP). N1 was enhanced to Go, as was the defining temporal topography of PN. NoGo produced increased centroparietal P2, frontocentral N2, and P3a, in comparison to Go, which produced a more parietal N2 and P3b, and an enhanced SW. The LP was larger in NoGo. These results suggest that N1 marks the beginning of Go and NoGo differentiation. Complete Go/NoGo categorisation is marked by N2; this is followed by different processing chains leading to the NoGo non-response (marked by P3a) and Go response (marked by P3b and SW). The larger LP in NoGo marks the cortical inactivation following the earlier cessation of processing in this condition.

Prestimulus delta and theta determinants of ERP responses in the Go/NoGo task.

Ongoing low-frequency EEG activity has long been associated with ERP components and their cognitive processing interpretations, yet few studies have directly investigated the prestimulus low-frequency EEG-ERP relationships, particularly within the auditory domain. The present study assessed the delta (1-3 Hz) and theta (4-7 Hz) bands individually, and their prestimulus influence on five subsequent components (P1, N1, P2, N2, and P3) within an equiprobable auditory Go/NoGo paradigm. At the nine central sites, accepted trials were sorted according to their ascending vertex prestimulus spectral band amplitude, and ERPs were derived from the upper and lower sorted thirds. The within-subjects analyses included amplitudes and latencies for both Go and NoGo responses, and Go response speed. Only component amplitudes showed effects of high/low prestimulus EEG level. Delta globally modulated the five components - all amplitudes were more positive with high prestimulus delta, regardless of stimulus condition. Theta did not influence P1, but inversely modulated P2 and P3 regionally, and produced stimulus-specific effects in N1, N2, and P3. Low prestimulus theta produced greater NoGo N2 and Go P3, and reduced NoGo P3 responses, each of these suggesting appropriately enhanced cognitive processing. Taken together, these effect patterns differentially implicate prestimulus delta and theta band activity in the determination of ERP component amplitudes and the cognitive processing associated with them.

Can event-related potentials serve as neural markers for wins, losses, and near-wins in a gambling task? A principal components analysis.

Originally, the feedback related negativity (FRN) event-related potential (ERP) component was considered to be a robust neural correlate of non-reward/punishment processing, with greater negative deflections observed following unfavourable outcomes. More recently, it has been suggested that this component is better conceptualised as a positive deflection following rewarding outcomes. The current study sought to elucidate the nature of the FRN, as well as another component associated with incentive-value processing, the P3b, through application of a spatiotemporal principal components analysis (PCA). Seventeen healthy controls played a computer electronic gaming machine (EGM) task and received feedback on credits won or lost on each trial, and ERPs were recorded. The distribution of reward/non-reward outcomes closely matched that of a real EGM, with frequent losses, and infrequent wins and near-wins. The PCA revealed that feedback elicited both a frontally maximal negative deflection to losses, and a positive deflection to wins (which was also sensitive to reward magnitude), implying that the neural generator/s of the FRN are differentially activated following these outcomes. As expected, greater P3b amplitudes were found for wins compared to losses. Interestingly, near-wins elicited significantly smaller FRN amplitudes than losses (with no differences in P3b amplitude), and may contribute to the maintenance of gambling behaviours on EGMs. The results of the current study are integrated into a response profile of healthy controls to outcomes of varying incentive value. This may provide a foundation for the future examination of individuals who exhibit abnormalities in reward/punishment processing, such as problem gamblers.

Preferred EEG brain states at stimulus onset in a fixed interstimulus interval equiprobable auditory Go/NoGo task: A definitive study

This study examined the occurrence of preferred EEG phase states at stimulus onset in an equiprobable auditory Go/NoGo task with a fixed interstimulus interval, and their effects on the resultant event-related potentials (ERPs). We used a sliding short-time FFT decomposition of the EEG at Cz for each trial to assess prestimulus EEG activity in the delta, theta, alpha and beta bands. We determined the phase of each 2 Hz narrow-band contributing to these four broad bands at 125 ms before each stimulus onset, and for the first time, avoided contamination from poststimulus EEG activity. This phase value was extrapolated 125 ms to obtain the phase at stimulus onset, combined into the broad-band phase, and used to sort trials into four phase groups for each of the four broad bands. For each band, ERPs were derived for each phase from the raw EEG activity at 19 sites. Data sets from each band were separately decomposed using temporal Principal Components Analyses with unrestricted VARIMAX rotation to extract N1-1, PN, P2, P3, SW and LP components. Each component was analysed as a function of EEG phase at stimulus onset in the context of a simple conceptualisation of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). The predicted non-random occurrence of phase-defined brain states was confirmed. The preferred states of negativity, negative driving, and waxing were each associated with more efficient stimulus processing, as reflected in amplitude differences of the components. The present results confirm the existence of preferred brain states and their impact on the efficiency of brain dynamics in perceptual and cognitive processing.

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=68.2years) to data from a sex- and handedness-matched group of university students (Mage=20.4years). 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.

Performance and ERP components in the equiprobable go/no-go task: Inhibition in children

The equiprobable go/no-go task lacks the dominant go imperative found in the usual go/no-go task, and hence we previously regarded it as involving little inhibition. However, children have relative difficulty with this task, and demonstrate large frontal no-go N2s. We investigated whether this child N2 plays an inhibitory role, using performance measures to illuminate the link between N2 and inhibition. Forty children aged 8 to 13 were presented with four stimulus blocks each containing 75 go and 75 no-go tone stimuli in random order. A temporal PCA with unrestricted varimax rotation quantified the mean go and no-go ERP component amplitudes. Most identified components were differentially enhanced to go or no-go as in adults, supporting a previously proposed differential processing schema. Between subjects, larger frontocentral no-go N2bs were associated with fewer commission errors. Hence, the no-go N2b in this paradigm can be interpreted as an individual marker of inhibition in children.

EEG-ERP phase dynamics of children in the auditory Go/NoGo task

Using a child sample, we examined the effects of the phase of narrow-band electroencephalographic (EEG) activity at stimulus onset on the resultant event-related potentials (ERPs) in an equiprobable auditory Go/NoGo task with a fixed stimulus-onset asynchrony. We used FFT decomposition of the EEG at Cz to assess prestimulus narrow-band EEG activity (in 1 Hz bands from 1 to 13 Hz) for each trial. From the cycle at stimulus onset, trials were sorted into four phases for each of the 13 frequencies. ERPs were derived for each of these from the raw EEG activity at the midline sites. ERP responses were analysed in the context of a simple conceptualisation of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). At a number of frequencies, crossing the traditional frequency bands, the predicted non-random occurrence of phase-defined brain states was confirmed. The preferred states of negativity and negative driving were each associated with more efficient stimulus processing, as reflected in latency and amplitude differences of the N1 and P3 ERP components. The present results confirm the existence of preferred brain states and their impact on the efficiency of brain dynamics involved in perceptual and cognitive processing, and extend their occurrence from adults to children.

Brain dynamics in the auditory Go/NoGo task as a function of EEG frequency

We examined relationships between the phase of narrow-band electroencephalographic (EEG) activity at stimulus onset and the resultant event-related potentials (ERPs) in an equiprobable auditory Go/NoGo task with a fixed SOA, in the context of a novel conceptualisation of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). ERP responses to each stimulus type were analysed. Prestimulus narrow-band EEG activity (in 1Hz bands from 1 to 13Hz) at Cz was assessed for each trial using FFT decomposition of the EEG data. For each frequency, the cycle at stimulus onset was used to sort trials into four phases, for which ERPs were derived from the raw EEG activity at 9 central sites. The occurrence of preferred phase-defined brain states was confirmed at a number of frequencies, crossing the traditional frequency bands. As expected, these did not differ between Go and NoGo stimuli. These preferred states were associated with more efficient processing of the stimulus, as reflected in differences in latency and amplitude of the N1 and P3 ERP components. The present results, although derived in a different paradigm by EEG decomposition methods different from those used previously, confirm the existence of preferred brain states and their impact on the efficiency of brain dynamics involved in perceptual and cognitive processing.

Reinstating the Novelty P3

P300 (or P3) is a major positive complex in the human event-related potential, occurring some 300 ms after stimulus onset, and long thought to be the cortical correlate of the Orienting Reflex, our automatic attention-grabbing response to a novel stimulus. The Novelty P3 was the third P3 subcomponent discovered (after P3a and P3b) and appeared promising in its sensitivity to stimulus novelty, the defining characteristic of the Orienting Reflex. But some 15 years later it was claimed to be indistinguishable from the previously-discovered P3a. This led to a decline in interest in the field and confused nomenclature, with some studies using “P3a” and “Novelty P3” interchangeably. However, recent similar studies have again reported three subcomponents of the P3. Further, using single-stimulus habituation paradigms, in addition to P3a and P3b, a later decrementing P3 subcomponent has been reported, and recently labelled “HabP3” to avoid contention. We report three studies to resolve this chaotic situation, arguing for identification of the late subcomponent following the P3a and P3b as the Novelty P3. Reinstatement of the Novelty P3 as the central index of the Orienting Reflex will have widespread impact in a range of theoretical, practical, and clinical areas involving novelty processing and attention.

Sequential processing in an auditory equiprobable Go/NoGo task with variable interstimulus interval

A recent series of studies of the auditory equiprobable Go/NoGo task, using fixed interstimulus intervals (ISIs), proposed a processing schema relating observed event-related potential (ERP) components to sequential processing stages. However, it has been demonstrated that attention and ERP components can be affected by the predictable rhythmic timing of fixed ISIs. Hence the aim of the current study was to test the robustness of that processing schema with an unpredictable arrhythmic variable ISI. EEG was recorded from 30 university students at 30 scalp sites in an unwarned auditory equiprobable Go/NoGo task using a variable ISI. Following our previous studies, Go and NoGo ERP components were derived using temporal principal components analysis (PCA). Of the unrestricted Varimax-rotated factors, seven were identifiable as components based on their topography, polarity, and latency: two subcomponents of the N1 (N1-1, and processing negativity, PN), P2/N2b, N2c/P3a, P3b, and two subcomponents of the slow wave (SW-1 and SW-2). These components showed Go/NoGo effects comparable to those previously noted with fixed ISI, supporting the proposed processing schema. The Late Positivity (LP) component, previously speculated to mark cortical deactivation after processing the NoGo stimulus, was not present in the sequence of components. In its absence, activity underlying the observed sustained P300/late positive complex may be involved in processing temporally-uncertain stimuli.