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 (M=20.4years) and 20 gender-matched older (M=68.2years) right-handed adults during two 3min 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.

Background: In resting-state EEG, the ratio between frontal power in the slow theta frequency band and the fast beta frequency band (the theta/beta ratio, TBR) has previously been negatively related to attentional control. Also, increased theta and reduced beta power were observed during mind wandering (MW) compared to episodes of focused attention. Thus, increased resting-state frontal TBR could be related to MW, suggesting that previously observed relationships between TBR and attentional control could reflect MW episodes increasing the average resting state TBR in people with low attentional control. Goals: To replicate and extend the previous theta and beta MW effects for frontal TBR recordings and test if MW related changes in frontal TBR are related to attentional control. Methods: Twenty-six healthy participants performed a 40-minute breath-counting task, after a baseline EEG recording, while EEG was measured and participants indicated MW episodes with button presses. Results: Frontal TBR was significantly higher during MW episodes than during on-task periods. However, no relation between frontal TBR and attentional control was found. Conclusions: This confirms that frontal TBR varies with MW episodes and that previous frontal TBRattentional control relations might be related to MW, though no direct evidence was found for this hypothesis.

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.

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.

Objective To compare sequential processing in the unwarned auditory equiprobable Go/NoGo task in children and adults, in the context of a recently developed adult schema. Methods Adult and child samples completed an equiprobable auditory Go/NoGo task while EEG was recorded from 19 channels. Go and NoGo ERPs were decomposed using unrestricted Varimax-rotated PCAs for the groups separately, and in combination. The separate adult and child components were compared using the Congruence Coefficient. Brain sources of each assessed component were examined using eLORETA. Results Corresponding adult/ child components were tentatively identified: two N1 subcomponents (N1-1, PN) and P2, followed by N2, P3 (separate P3a/P3b in children), the classic Slow Wave (SW), and a diffuse Late Positivity (LP). While early and late components showed similarities, the intermediate P2 and N2 differed substantially in their stimulus effects. Conclusions Aspects of "Go" vs. "NoGo" categorisation differ between adults and children, but subsequent processing reflected in the different Go/NoGo P3 components, and their sequellae, are similar. Significance This is the first detailed examination of child responses in this paradigm. The tested schema appears relatively robust in adults, and the child results may aid our understanding of developmental aspects of cognitive processing in normal and atypical individuals. Methods: Adult and child samples completed an equiprobable auditory Go/NoGo task while EEG was recorded from 19 channels. Go and NoGo ERPs were decomposed using unrestricted Varimax-rotated PCAs for the groups separately, and in combination. The separate adult and child components were compared using the Congruence Coefficient. Brain sources of each assessed component were examined using eLORETA.Results: Corresponding adult/child components were tentatively identified: two N1 subcomponents (N1-1, PN) and P2, followed by N2, P3 (separate P3a/P3b in children), the classic Slow Wave (SW), and a diffuse Late Positivity (LP). While early and late components showed similarities, the intermediate P2 and N2 differed substantially in their stimulus effects.Conclusions: Aspects of "Go" versus "NoGo" categorisation differ between adults and children, but subsequent processing reflected in the different Go/NoGo P3 components, and their sequellae, are similar.Significance: This is the first detailed examination of child responses in this paradigm. The tested schema appears relatively robust in adults, and the child results may aid our understanding of developmental aspects of cognitive processing in normal and atypical individuals. 3 Highlights• Some early and late ERP components show similarities, but Go/NoGo P2 and N2 effects differ with age.• This indicates that aspects of stimulus categorisation differ between children and adults.• Subsequent processing reflected in P3 and later components is similar. 4