Sequential processing in the equiprobable auditory Go/NoGo task: Children vs. adults

Age-Related Differences in Prestimulus EEG Affect ERPs and Behaviour in the Equiprobable Go/NoGo Task

Detailed studies of the equiprobable auditory Go/NoGo task have allowed for the development of a sequential-processing model of the perceptual and cognitive processes involved. These processes are reflected in various components differentiating the Go and NoGo event-related potentials (ERPs). It has long been established that electroencephalography (EEG) changes through normal lifespan development. It is also known that ERPs and behaviour in the equiprobable auditory Go/NoGo task change from children to young adults, and again in older adults. Here, we provide a novel examination of links between in-task prestimulus EEG, poststimulus ERPs, and behaviour in three gender-matched groups: children (8-12 years), young adults (18-24 years), and older adults (59-74 years). We used a frequency Principal Component Analysis (f-PCA) to estimate prestimulus EEG components and a temporal Principal Component Analysis (t-PCA) to separately estimate poststimulus ERP Go and NoGo components in each age group to avoid misallocation of variance. The links between EEG components, ERP components, and behavioural measures differed markedly between the groups. The young adults performed best and accomplished this with the simplest EEG-ERP-behaviour brain dynamics pattern. The children performed worst, and this was reflected in the most complex brain dynamics pattern. The older adults showed some reduction in performance, reflected in an EEG-ERP-behaviour pattern with intermediate complexity between those of the children and young adults. These novel brain dynamics patterns hold promise for future developmental research.

Inhibitory control deficits in patients with mesial temporal lobe epilepsy: an event-related potential analysis based on Go/NoGo task

Objective

Neuropsychiatric comorbidities are common among patients with mesial temporal lobe epilepsy (MTLE). One of these comorbidities, impulsivity, can significantly impact the quality of life and prognosis. However, there have been few studies of impulsivity in these patients, and the existing findings are inconsistent. The present study investigates impulsivity in MTLE patients from the perspective of inhibitory control and its underlying processes using event-related potentials (ERPs) initiated using a Go/NoGo task.

Methods

A total of 25 MTLE patients and 25 age-, gender-, and education-matched healthy controls (HCs) completed an unequal visual Go/NoGo task. Different waveforms as well as behavioral measures were analyzed between Go and NoGo conditions (N2d and P3d). Impulsivity was also assessed using self -rating scales, and clinical variables that may be related to ERPs were explored.

Results

Compared with HCs, MTLE patients exhibited significantly longer reaction time (RT) (p = 0.002) and lower P3d especially at the frontal electrode sites (p = 0.001). In the MTLE group, the seizure frequency (p = 0.045) and seizure types (p < 0.001) were correlated with the P3d amplitude. A self-rated impulsivity assessment revealed that MTLE patients had higher non-planning (p = 0.017) and total scores (p = 0.019) on the BIS-11 as well as higher DI (p = 0.010) and lower FI (p = 0.007) on the DII.

Conclusion

The findings demonstrate that the presence of inhibitory control deficits in patients with MTLE are characterized by deficits in the late stage of inhibition control, namely the motor inhibition stage. This study improves our understanding of impulsivity in MTLE patients and suggests that ERPs may constitute a sensitive means of detecting this trait.

Effects of 6-Month Combined Physical Exercise and Cognitive Training on Neuropsychological and Neurophysiological Function in Older Adults with Subjective Cognitive Decline: A Randomized Controlled Trial

Background

Multidomain intervention may delay or ameliorate cognitive decline in older adults at risk of Alzheimer's disease, particularly in the memory and inhibitory functions. However, no study systematically investigates the changes of brain function in cognitively-normal elderly with subjective cognitive decline (SCD) when they receive multidomain intervention.

Objective

We aimed to examine whether a multidomain intervention could improve neuropsychological function and neurophysiological activities related to memory and inhibitory function in SCD subjects.

Methods

Eight clusters with a total of 50 community-dwelling SCD older adults were single-blind, randomized into intervention group, which received physical and cognitive training, or control group, which received treatment as usual. For the neuropsychological function, a composite Z score from six cognitive tests was calculated and compared between two groups. For the neurophysiological activities, event-related potentials (ERPs) of memory function, including mismatch negativity (MMN) and memory-P3, as well as ERPs of inhibitory function, including sensory gating (SG) and inhibition-P3, were measured. Assessments were performed at baseline (T1), end of the intervention (T2), and 6 months after T2 (T3).

Results

For the neuropsychological function, the effect was not observed after the intervention. For the neurophysiological activities, improved MMN responses of ΔT2-T1 were observed in the intervention group versus the control group. The multidomain intervention produced a sustained effect on memory-P3 latencies of ΔT3-T1. However, there were no significant differences in changes of SG and inhibition-P3 between intervention and control groups.

Conclusions

While not impactful on neuropsychological function, multidomain intervention enhances specific neurophysiological activities associated with memory function.

EEG, ERPs, and EROs in patients with neurodegenerative dementing disorders: A window into the cortical neurophysiology of cognition and behavior

In the human brain, physiological aging is characterized by progressive neuronal loss, leading to disruption of synapses and to a degree of failure in neurotransmission and information flow. However, there is increasing evidence to support the notion that the aged brain has a remarkable level of resilience (i.s. ability to reorganize itself), with the aim of preserving its physiological activity. It is therefore of paramount interest to develop objective markers able to characterize the biological processes underlying brain aging in the intact human, and to distinguish them from brain degeneration associated to age-related neurological progressive diseases like Alzheimer's disease. EEG, alone and combined with transcranial magnetic stimulation (TMS-EEG), is particularly suited to this aim, due to the functional nature of the information provided, and thanks to the ease with which it can be integrated in ecological scenarios including behavioral tasks. In this review, we aimed to provide the reader with updated information about the role of modern methods of EEG and TMS-EEG analysis in the investigation of physiological brain aging and Alzheimer's disease. In particular, we focused on data about cortical connectivity obtained by using readouts such graph theory network brain organization and architecture, and transcranial evoked potentials (TEPs) during TMS-EEG. Overall, findings in the literature support an important potential contribution of such neurophysiological techniques to the understanding of the mechanisms underlying normal brain aging and the early (prodromal/pre-symptomatic) stages of dementia.

A tutorial on the use of temporal principal component analysis in developmental ERP research - Opportunities and challenges

Developmental researchers are often interested in event-related potentials (ERPs). Data-analytic approaches based on the observed ERP suffer from major problems such as arbitrary definition of analysis time windows and regions of interest and the observed ERP being a mixture of latent underlying components. Temporal principal component analysis (PCA) can reduce these problems. However, its application in developmental research comes with the unique challenge that the component structure differs between age groups (so-called measurement non-invariance). Separate PCAs for the groups can cope with this challenge. We demonstrate how to make results from separate PCAs accessible for inferential statistics by re-scaling to original units. This tutorial enables readers with a focus on developmental research to conduct a PCA-based ERP analysis of amplitude differences. We explain the benefits of a PCA-based approach, introduce the PCA model and demonstrate its application to a developmental research question using real-data from a child and an adult group (code and data openly available). Finally, we discuss how to cope with typical challenges during the analysis and name potential limitations such as suboptimal decomposition results, data-driven analysis decisions and latency shifts.

General principles of brain electromagnetic rhythmic oscillations and implications for neuroplasticity

Neuro-plasticity describes the ability of the brain in achieving novel functions, either by transforming its internal connectivity, or by changing the elements of which it is made, meaning that, only those changes, that affect both structural and functional aspects of the system, can be defined as "plastic." The concept of plasticity can be applied to molecular as well as to environmental events that can be recognized as the basic mechanism by which our brain reacts to the internal and external stimuli. When considering brain plasticity within a clinical context-that is the process linked with changes of brain functions following a lesion- the term "reorganization" is somewhat synonymous, referring to the specific types of structural/functional modifications observed as axonal sprouting, long-term synaptic potentiation/inhibition or to the plasticity related genomic responses. Furthermore, brain rewires during maturation, and aging thus maintaining a remarkable learning capacity, allowing it to acquire a wide range of skills, from motor actions to complex abstract reasoning, in a lifelong expression. In this review, the contribution on the "neuroplasticity" topic coming from advanced analysis of EEG rhythms is put forward.

Identification of an early-stage Parkinson's disease neuromarker using event-related potentials, brain network analytics and machine-learning

OBJECTIVE

The purpose of this study is to explore the possibility of developing a biomarker that can discriminate early-stage Parkinson's disease from healthy brain function using electroencephalography (EEG) event-related potentials (ERPs) in combination with Brain Network Analytics (BNA) technology and machine learning (ML) algorithms.

BACKGROUND

Currently, diagnosis of PD depends mainly on motor signs and symptoms. However, there is need for biomarkers that detect PD at an earlier stage to allow intervention and monitoring of potential disease-modifying therapies. Cognitive impairment may appear before motor symptoms, and it tends to worsen with disease progression. While ERPs obtained during cognitive tasks performance represent processing stages of cognitive brain functions, they have not yet been established as sensitive or specific markers for early-stage PD.

METHODS

Nineteen PD patients (disease duration of ≤2 years) and 30 healthy controls (HC) underwent EEG recording while performing visual Go/No-Go and auditory Oddball cognitive tasks. ERPs were analyzed by the BNA technology, and a ML algorithm identified a combination of features that distinguish early PD from HC. We used a logistic regression classifier with a 10-fold cross-validation.

RESULTS

The ML algorithm identified a neuromarker comprising 15 BNA features that discriminated early PD patients from HC. The area-under-the-curve of the receiver-operating characteristic curve was 0.79. Sensitivity and specificity were 0.74 and 0.73, respectively. The five most important features could be classified into three cognitive functions: early sensory processing (P50 amplitude, N100 latency), filtering of information (P200 amplitude and topographic similarity), and response-locked activity (P-200 topographic similarity preceding the motor response in the visual Go/No-Go task).

CONCLUSIONS

This pilot study found that BNA can identify patients with early PD using an advanced analysis of ERPs. These results need to be validated in a larger PD patient sample and assessed for people with premotor phase of PD.

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.

Modality differences in ERP components between somatosensory and auditory Go/No-go paradigms in prepubescent children

We investigated modality differences in the N2 and P3 components of event-related potentials (ERPs) between somatosensory and auditory Go/No-go paradigms in eighteen healthy prepubescent children (mean age: 125.9±4.2 months). We also evaluated the relationship between behavioral responses (reaction time, reaction time variability, and omission and commission error rates) and amplitudes and latencies of N2 and P3 during somatosensory and auditory Go/No-go paradigms. The peak latency of No-go-N2 was significantly shorter than that of Go-N2 during somatosensory paradigms, but not during auditory paradigms. The peak amplitude of P3 was significantly larger during somatosensory than auditory paradigms, and the peak latency of P3 was significantly shorter during somatosensory than auditory paradigms. Correlations between behavioral responses and the P3 component were not found during somatosensory paradigms. On the other hand, in auditory paradigms, correlations were detected between the reaction time and peak amplitude of No-go-P3, and between the reaction time variability and peak latency of No-go-P3. A correlation was noted between commission error and the peak latency of No-go-N2 during somatosensory paradigms. Compared with previous adult studies using both somatosensory and auditory Go/No-go paradigms, the relationships between behavioral responses and ERP components would be weak in prepubescent children. Our data provide findings to advance understanding of the neural development of motor execution and inhibition processing, that is dependent on or independent of the stimulus modality.

A simple and cheap setup for timing tapping responses synchronized to auditory stimuli

Measuring human capabilities to synchronize in time, adapt to perturbations to timing sequences, or reproduce time intervals often requires experimental setups that allow recording response times with millisecond precision. Most setups present auditory stimuli using either MIDI devices or specialized hardware such as Arduino and are often expensive or require calibration and advanced programming skills. Here, we present in detail an experimental setup that only requires an external sound card and minor electronic skills, works on a conventional PC, is cheaper than alternatives, and requires almost no programming skills. It is intended for presenting any auditory stimuli and recording tapping response times with within 2-ms precision (up to - 2 ms lag). This paper shows why desired accuracy in recording response times against auditory stimuli is difficult to achieve in conventional computer setups, presents an experimental setup to overcome this, and explains in detail how to set it up and use the provided code. Finally, the code for analyzing the recorded tapping responses was evaluated, showing that no spurious or missing events were found in 94% of the analyzed recordings.

Inferior Auditory Time Perception in Children With Motor Difficulties

Accurate time perception is crucial for hearing (speech, music) and action (walking, catching). Motor brain regions are recruited during auditory time perception. Therefore, the hypothesis was tested that children (age 6-7) at risk for developmental coordination disorder (rDCD), a neurodevelopmental disorder involving motor difficulties, would show nonmotor auditory time perception deficits. Psychophysical tasks confirmed that children with rDCD have poorer duration and rhythm perception than typically developing children (N = 47, d = 0.95-1.01). Electroencephalography showed delayed mismatch negativity or P3a event-related potential latency in response to duration or rhythm deviants, reflecting inefficient brain processing (N = 54, d = 0.71-0.95). These findings are among the first to characterize perceptual timing deficits in DCD, suggesting important theoretical and clinical implications.

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.

Neurophysiological Hallmarks of Neurodegenerative Cognitive Decline: The Study of Brain Connectivity as A Biomarker of Early Dementia

Neurodegenerative processes of various types of dementia start years before symptoms, but the presence of a "neural reserve", which continuously feeds and supports neuroplastic mechanisms, helps the aging brain to preserve most of its functions within the "normality" frame. Mild cognitive impairment (MCI) is an intermediate stage between dementia and normal brain aging. About 50% of MCI subjects are already in a stage that is prodromal-to-dementia and during the following 3 to 5 years will develop clinically evident symptoms, while the other 50% remains at MCI or returns to normal. If the risk factors favoring degenerative mechanisms are modified during early stages (i.e., in the prodromal), the degenerative process and the loss of abilities in daily living activities will be delayed. It is therefore extremely important to have biomarkers able to identify-in association with neuropsychological tests-prodromal-to-dementia MCI subjects as early as possible. MCI is a large (i.e., several million in EU) and substantially healthy population; therefore, biomarkers should be financially affordable, largely available and non-invasive, but still accurate in their diagnostic prediction. Neurodegeneration initially affects synaptic transmission and brain connectivity; methods exploring them would represent a 1st line screening. Neurophysiological techniques able to evaluate mechanisms of synaptic function and brain connectivity are attracting general interest and are described here. Results are quite encouraging and suggest that by the application of artificial intelligence (i.e., learning-machine), neurophysiological techniques represent valid biomarkers for screening campaigns of the MCI population.

The effect of age on N2 and P3 components: A meta-analysis of Go/Nogo tasks

Suppressing the neural activities to non-target stimuli becomes problematic with advancing age. Go/Nogo tasks, in which subjects are instructed to respond to a certain type of stimuli (Go) and withhold responses to other types of predefined stimuli (Nogo), have been extensively employed to study the age-related alterations of cognitive inhibition. However, it remains inconclusive whether the N2 and P3 electrophysiological responses to successful inhibition to Nogo stimuli are affected by aging processes. Thus, we performed a meta-analysis of Go/Nogo studies to investigate the age effect on Nogo-N2 and Nogo-P3 activities as well as behavioral performance of commission errors. The potential moderators regarding different probabilities of Nogo trials and levels of task difficulty on the effect sizes were also assessed. There were no significant age-related differences in commission errors. However, compared to the younger group, the elderly demonstrated reduced Nogo-N2 amplitudes, particularly in the condition where Nogo probability was less than 50%. Furthermore, age-related reduction of Nogo-P3 amplitudes and prolongation of Nogo-P3 latencies were observed in the condition where Nogo probability was less than 50%. In conclusion, our data suggest that despite similar behavioral performance in the younger and older adults, neural processing of response inhibition becomes inefficient with advancing age.

Sequential processing in the classic oddball task: ERP components, probability, and behavior

This study compared the ERP components and behavior associated with the auditory equiprobable and classic oddball tasks, to relate the cognitive processing stages in those paradigms and continue the development of the sequential processing schema. Target and nontarget ERP data were acquired from 66 healthy young adults (M_age = 20.1, SD = 2.4 years, 14 male) who completed both equiprobable (target p = 0.5) and oddball tasks (target p = 0.3). Separate temporal PCAs were used to decompose the ERP data in each task and condition, and the similarity of the components identified in each condition was examined between tasks. Probability effects on component amplitudes and behavior were also analyzed to identify task differences in cognitive demands. A highly similar series of components was identified in each task, closely matching the schema: targets elicited N1-3, N1-1, PN, N2c, P3b, SW1, SW2; whereas nontargets elicited N1-3, N1-1, PN, N2b, P3a, SW1, SW2. N1-1 and PN amplitudes increased as stimulus probability decreased, irrespective of the condition. N2b, P3b, SW1, and SW2 amplitudes also varied between tasks, illustrating task-specific demands on those processing stages. These findings complemented the behavioral outcomes, which demonstrated greater accuracy and control in the classic oddball task. Overall, this study demonstrated comparable processing in the auditory equiprobable and classic oddball tasks, extending the generalizability of the schema and enabling further integration of the ERP theory associated with these tasks. This study also clarifies stimulus probability effects on the schema, providing important insight into the functionality of common ERP components.

Connectome: Graph theory application in functional brain network architecture

•

Network science and graph theory applications can help in understanding how human cognitive functions are linked to neuronal network structure.

•

The present review focuses on pivotal recent studies regarding graph theory application on functional dynamic connectivity investigated by electroencephalographic (EEG) analysis.

•

Graph analysis applications represent an interesting probe to analyze the distinctive features of real life by focusing on functional connectivity networks.

•

Application of graph theory to patient data might provide more insight into the pathophysiological processes underlying brain disconnection.

•

Graph theory might aid in monitoring the impact of eventual pharmacological and rehabilitative treatments.

Network science and graph theory applications have recently spread widely to help in understanding how human cognitive functions are linked to neuronal network structure, thus providing a conceptual frame that can help in reducing the analytical brain complexity and underlining how network topology can be used to characterize and model vulnerability and resilience to brain disease and dysfunction. The present review focuses on few pivotal recent studies of our research team regarding graph theory application in functional dynamic connectivity investigated by electroencephalographic (EEG) analysis. The article is divided into two parts. The first describes the methodological approach to EEG functional connectivity data analysis. In the second part, network studies of physiological aging and neurological disorders are explored, with a particular focus on epilepsy and neurodegenerative dementias, such as Alzheimer's disease.

Significance and Novelty effects in single-trial ERP components and autonomic responses

The phasic orienting reflex (OR) was investigated in two counterbalanced blocks of an auditory dishabituation paradigm differing in stimulus Significance (operationalised as tone counting). Twelve tones were presented at very long, randomly-varying interstimulus intervals (ISIs). Novelty and Significance were varied within subjects. Stimulus-response patterns were assessed to find ERP matches for autonomic measures. The phasic OR index was represented by the skin conductance response (SCR). SCR decremented over 10 standard trials, showed recovery on trial 11 (change trial), enhancement to re-presentation of the standard tone (trial 12: dishabituation), and a main effect of Significance over the first 10 trials - demonstrating the formal criteria for an OR index. The evoked cardiac response (HR) subcomponents ECR1 (deceleration) and ECR2 (acceleration) showed no trial effects, but ECR2 showed a Significance effect. Respiratory pause (RP) decreased linearly over trials, and showed recovery, but no dishabituation or Significance effect. Temporal PCA was applied to single-trial EOG-corrected data. Ten ERP components were extracted: P1, N1-3, N1-1, PN, P2, P3a, P3b, HabP3, a Frontal Slow Wave (FSW), and the Classic SW. The dependent measures showed 4 distinct patterns. Pattern 1: No trial or Significance effects (ECR1, P1, N1-3, P3a, FSW); Pattern 2: No trial effect but a Significance effect (ECR2, N1-1, P2); Pattern 3: Trial but not Significance effects (RP, PN, P3b, HabP3); Pattern 4: Both trial and Significance effects (SCR and Classic SW). The evidenced fractionation of autonomic and central measures is compatible with Preliminary Process Theory (PPT), contrary to the notion of a unitary OR.

Delayed N2 response in Go condition in a visual Go/Nogo ERP study in children who stutter

PURPOSE OF THE STUDY

The main aim of the study was to investigate the attentional and inhibitory abilities and their underlying processes of children who stutter by using behavioural measurement and event-related potentials (ERP) in a visual Go/Nogo paradigm.

METHODS

Participants were 11 children who stutter (CWS; mean age 8.1, age range 6.3-9.5 years) and 19 typically developed children (TDC; mean age 8.1, age range 5.8-9.6 years). They performed a visual Go/Nogo task with simultaneous EEG recording to obtain ERP responses.

RESULTS

Results showed that CWS had longer N2 and P3 latencies in the Go condition compared to the TDC. In contrast, the groups did not differ significantly in the Nogo condition or behavioural measures.

CONCLUSIONS

Our findings did not confirm less efficient inhibitory control in CWS but suggest atypical attentional processing such as stimulus evaluation and response selection.

EDUCATIONAL OBJECTIVES

The reader will be able to (a) describe recent findings on attention and inhibitory control in children who stutter, (b) describe the measurement of attentional processing, including inhibitory control, and (c) describe the findings on attentional processing in children who stutter as indexed by the event-related potentials in a visual Go/Nogo paradigm.

The Influence of Selective and Divided Attention on Audiovisual Integration in Children

This article aims to investigate whether there is a difference in audiovisual integration in school-aged children (aged 6 to 13 years; mean age = 9.9 years) between the selective attention condition and divided attention condition. We designed a visual and/or auditory detection task that included three blocks (divided attention, visual-selective attention, and auditory-selective attention). The results showed that the response to bimodal audiovisual stimuli was faster than to unimodal auditory or visual stimuli under both divided attention and auditory-selective attention conditions. However, in the visual-selective attention condition, no significant difference was found between the unimodal visual and bimodal audiovisual stimuli in response speed. Moreover, audiovisual behavioral facilitation effects were compared between divided attention and selective attention (auditory or visual attention). In doing so, we found that audiovisual behavioral facilitation was significantly difference between divided attention and selective attention. The results indicated that audiovisual integration was stronger in the divided attention condition than that in the selective attention condition in children. Our findings objectively support the notion that attention can modulate audiovisual integration in school-aged children. Our study might offer a new perspective for identifying children with conditions that are associated with sustained attention deficit, such as attention-deficit hyperactivity disorder.

Trials and intensity effects in single-trial ERP components and autonomic responses in a dishabituation paradigm with very long ISIs

The phasic orienting reflex (OR) was investigated using single-trial data collected concurrently from 4 autonomic measures and event-related potentials (ERPs). In an auditory dishabituation paradigm, twelve indifferent tones of two intensities (60 or 80 dB, intensity change on trial 11, counterbalanced between subjects) were presented at very long interstimulus intervals (ISIs). Novelty and intensity based stimulus-response patterns were examined seeking ERP analogues of autonomic measures representing pre-OR and OR processing. Skin conductance response (SCR) represented the phasic OR index. EOG-corrected ERP data for 16 subjects were decomposed by a temporal Principal Components Analysis (PCA). SCR diminished over 10 standard trials, recovered on change trial 11, dishabituated to the re-presentation of the standard tone on trial 12, and showed intensity effects at the change - formal requirements for an OR index. The evoked cardiac response (HR) showed no trial or intensity effects. Respiratory pause (RP) decreased linearly over trials and showed recovery but no dishabituation or intensity effect. Peripheral vasoconstriction (PVC) failed to decrement but exhibited an intensity effect. Ten identifiable ERP components were extracted: Na, P1, N1-1, PN, P2, P3a, P3b, a novelty-sensitive HabP3, an intensity-sensitive IntP3, and the Slow Wave (SW). Pattern 1 showed no trial or intensity effects (HR, P1, PN, P2); Pattern 2 showed no trial effect but an intensity effect (PVC, Na, N1-1, P3a); and Pattern 3 demonstrated habituation and an intensity effect (SCR, RP, P3b, HabP3, IntP3, SW). The observed fractionation of autonomic and central measures is consistent with Preliminary Process Theory (PPT) rather than the notion of a unitary OR.

Future challenges for vection research: definitions, functional significance, measures, and neural bases

This paper discusses four major challenges facing modern vection research. Challenge 1 (Defining Vection) outlines the different ways that vection has been defined in the literature and discusses their theoretical and experimental ramifications. The term vection is most often used to refer to visual illusions of self-motion induced in stationary observers (by moving, or simulating the motion of, the surrounding environment). However, vection is increasingly being used to also refer to non-visual illusions of self-motion, visually mediated self-motion perceptions, and even general subjective experiences (i.e., “feelings”) of self-motion. The common thread in all of these definitions is the conscious subjective experience of self-motion. Thus, Challenge 2 (Significance of Vection) tackles the crucial issue of whether such conscious experiences actually serve functional roles during self-motion (e.g., in terms of controlling or guiding the self-motion). After more than 100 years of vection research there has been surprisingly little investigation into its functional significance. Challenge 3 (Vection Measures) discusses the difficulties with existing subjective self-report measures of vection (particularly in the context of contemporary research), and proposes several more objective measures of vection based on recent empirical findings. Finally, Challenge 4 (Neural Basis) reviews the recent neuroimaging literature examining the neural basis of vection and discusses the hurdles still facing these investigations.

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.