Response-related potentials during semantic priming: the effect of a speeded button response task on ERPs

This study examines the influence of a button response task on the event-related potential (ERP) in a semantic priming experiment. Of particular interest is the N400 component. In many semantic priming studies, subjects are asked to respond to a stimulus as fast and accurately as possible by pressing a button. Response time (RT) is recorded in parallel with an electroencephalogram (EEG) for ERP analysis. In this case, the response occurs in the time window used for ERP analysis and response-related components may overlap with stimulus-locked ones such as the N400. This has led to a recommendation against such a design, although the issue has not been explored in depth. Since studies keep being published that disregard this issue, a more detailed examination of influence of response-related potentials on the ERP is needed. Two experiments were performed in which subjects pressed one of two buttons with their dominant hand in response to word-pairs with varying association strength (AS), indicating a personal judgement of association between the two words. In the first experiment, subjects were instructed to respond as fast and accurately as possible. In the second experiment, subjects delayed their button response to enforce a one second interval between the onset of the target word and the button response. Results show that in the first experiment a P3 component and motor-related potentials (MRPs) overlap with the N400 component, which can cause a misinterpretation of the latter. In order to study the N400 component, the button response should be delayed to avoid contamination of the ERP with response-related components

ERPs and their brain sources in perceptual and conceptual prospective memory tasks: commonalities and differences between the two tasks

The present study examined whether Event-Related Potential (ERP) components and their neural generators are common to perceptual and conceptual prospective memory (PM) tasks or specific to the form of PM cue involved. We used Independent Component Analysis (ICA) to study the contributions of brain source activities to scalp ERPs across the different phases of two event-based PM-tasks: (1) holding intentions during a delay (monitoring) (2) detecting the correct context to perform the delayed intention (cue detection) and (3) carrying out the action (realisation of delayed intentions). Results showed that monitoring for both perceptual and conceptual PM-tasks was characterised by an enhanced early occipital negativity (N200). In addition the conceptual PM-task showed a long-lasting effect of monitoring significant around 700 ms. Perceptual PM-task cues elicited an N300 enhancement associated with cue detection, whereas a midline N400-like response was evoked by conceptual PM-task cues. The Prospective Positivity associated with realisation of delayed intentions was observed in both conceptual and perceptual tasks. A common frontal-midline brain source contributed to the Prospective Positivity in both tasks and a strong contribution from parieto-frontal brain sources was observed only for the perceptually cued PM-task. These findings support the idea that: (1) The enhanced N200 can be understood as a neural correlate of a ‘retrieval mode’ for perceptual and conceptual PM-tasks, and additional strategic monitoring is implemented according the nature of the PM task; (2) ERPs associated with cue detection are specific to the nature of the PM cues; (3) Prospective Positivity reflects a general PM process, but the specific brain sources contributing to it depend upon the nature of the PM task

Analytical methods and experimental approaches for electrophysiological studies of brain oscillations

Brain oscillations are increasingly the subject of electrophysiological studies probing their role in the functioning and dysfunction of the human brain. In recent years this research area has seen rapid and significant changes in the experimental approaches and analysis methods. This article reviews these developments and provides a structured overview of experimental approaches, spectral analysis techniques and methods to establish relationships between brain oscillations and behaviour

ERP Markers of Auditory Go/NoGo Processing

The Sequential Processing Schema is a data-driven model that uses event-related potential (ERP) components to chart the important psychophysiological processes activated when completing auditory equiprobable Go/NoGo tasks. This model is useful for measuring experimental effects on basic cognitive processes and provides a valuable framework to synthesise and test ERP component theories. Determining the cognitive and behavioural correlates of ERP components is critical for understanding their functional significance and utility in psychology. Additional research is also needed to refine the conceptualisation of the ERP components and cognitive processing requirements in equiprobable Go/NoGo tasks, which are commonly used in psychophysiological research. To do that, robust data-driven methods such as temporal Principal Components Analysis (PCA) are needed for effective ERP component quantification and analyses of the Go/NoGo ERP component ‘processing’ series. This doctoral thesis aimed to clarify ERP component functionality and refine our understanding of equiprobable Go/NoGo tasks by developing the Sequential Processing Schema and exploring how ERP/PCA components relate to cognitive and behavioural processing under different Go/NoGo task conditions. Study 1 compared the ERP component processing series associated with auditory equiprobable and oddball variants of the Go/NoGo task. The manipulation of probability and the relevant modulation of the ERP component series reflected a shift in particular cognitive demands or task requirements, which promoted the conceptual development of component functionality and the generalisability of the Schema. The results of Study 1 questioned the identity of a core ERP component (i.e., Processing Negativity) previously linked to auditory Go/NoGo processing; this was pursued in detail in Study 2, which aimed to clarify the ERP components associated with early information processing in auditory equiprobable and ‘frequent Go’ variants of the Go/NoGo task. Stimulus probability differences (this time the inverse of Study 1) were again used to elucidate component functionality and provide insight into the cognitive task demands. Study 3 and 4 explored ERP component functionality by examining Go stimulus- and response-locked ERP averaging effects, and the link between the equiprobable NoGo P3a and motor response inhibition. Studies 1–4 provided insight into the sequential processing requirements in auditory equiprobable Go/NoGo tasks, and the associated ERP/PCA components, promoting the development of common ERP components as indices of cognitive processes. These outcomes clarified the utility of the equiprobable Go/NoGo task, and highlight important similarities and differences between Go/NoGo and oddball processing, encouraging ERP theory development and integration between those common research paradigms. An update to the Schema was proposed to accommodate the ERP findings and reflect the refined interpretation of equiprobable Go/NoGo processing developed in this thesis, including a shift in the conceptualisation of the sensory processing and inhibitory requirements in the equiprobable task. This was considered to improve the conceptual framework of the Schema and its utility for charting the cognitive and behavioural processing in different task conditions. The outcomes also provide novel insight into how healthy young adults process information and encourage further studies of sequential processing to help delineate abnormalities in cognitive processing related to different psychopathologie

Reconstructing ERP amplitude effects after compensating for trial-to-trial latency jitter: A solution based on a novel application of residue iteration decomposition

© 2016 The Authors Stimulus-locked averaged event-related potentials (ERPs) are among the most frequently used signals in Cognitive Neuroscience. However, the late, cognitive or endogenous ERP components are often variable in latency from trial to trial in a component-specific way, compromising the stability assumption underlying the averaging scheme. Here we show that trial-to-trial latency variability of ERP components not only blurs the average ERP waveforms, but may also attenuate existing or artificially induce condition effects in amplitude. Hitherto this problem has not been well investigated. To tackle this problem, a method to measure and compensate component-specific trial-to-trial latency variability is required. Here we first systematically analyze the problem of single trial latency variability for condition effects based on simulation. Then, we introduce a solution by applying residue iteration decomposition (RIDE) to experimental data. RIDE separates different clusters of ERP components according to their time-locking to stimulus onsets, response times, or neither, based on an algorithm of iterative subtraction. We suggest to reconstruct ERPs by re-aligning the component clusters to their most probable single trial latencies. We demonstrate that RIDE-reconstructed ERPs may recover amplitude effects that are diminished or exaggerated in conventional averages by trial-to-trial latency jitter. Hence, RIDE-corrected ERPs may be a valuable tool in conditions where ERP effects may be compromised by latency variability.Link_to_subscribed_fulltex

Fluctuations in instantaneous frequency predict alpha amplitude during visual perception.

Rhythmic neural activity in the alpha band (8-13 Hz) is thought to have an important role in the selective processing of visual information. Typically, modulations in alpha amplitude and instantaneous frequency are thought to reflect independent mechanisms impacting dissociable aspects of visual information processing. However, in complex systems with interacting oscillators such as the brain, amplitude and frequency are mathematically dependent. Here, we record electroencephalography in human subjects and show that both alpha amplitude and instantaneous frequency predict behavioral performance in the same visual discrimination task. Consistent with a model of coupled oscillators, we show that fluctuations in instantaneous frequency predict alpha amplitude on a single trial basis, empirically demonstrating that these metrics are not independent. This interdependence suggests that changes in amplitude and instantaneous frequency reflect a common change in the excitatory and inhibitory neural activity that regulates alpha oscillations and visual information processing

Electroencephalographic Brain Dynamics Following Manually Responded Visual Targets

Scalp-recorded electroencephalographic (EEG) signals produced by partial synchronization of cortical field activity mix locally synchronous electrical activities of many cortical areas. Analysis of event-related EEG signals typically assumes that poststimulus potentials emerge out of a flat baseline. Signals associated with a particular type of cognitive event are then assessed by averaging data from each scalp channel across trials, producing averaged event-related potentials (ERPs). ERP averaging, however, filters out much of the information about cortical dynamics available in the unaveraged data trials. Here, we studied the dynamics of cortical electrical activity while subjects detected and manually responded to visual targets, viewing signals retained in ERP averages not as responses of an otherwise silent system but as resulting from event-related alterations in ongoing EEG processes. We applied infomax independent component analysis to parse the dynamics of the unaveraged 31-channel EEG signals into maximally independent processes, then clustered the resulting processes across subjects by similarities in their scalp maps and activity power spectra, identifying nine classes of EEG processes with distinct spatial distributions and event-related dynamics. Coupled two-cycle postmotor theta bursts followed button presses in frontal midline and somatomotor clusters, while the broad postmotor “P300” positivity summed distinct contributions from several classes of frontal, parietal, and occipital processes. The observed event-related changes in local field activities, within and between cortical areas, may serve to modulate the strength of spike-based communication between cortical areas to update attention, expectancy, memory, and motor preparation during and after target recognition and speeded responding

Evoked Potentials during Language Processing as Neurophysiological Phenomena

The evoked, event-related potential of the EEG has been extensively employed to study language processing. But what is the ERP? An extensive discussion of contemporary theories about the neurophysiology underlying late ERPs is given. Then, in a series of experiments, domain-general perspectives on ERP components are tested regarding their applicability for language-related brain activity. A range of analysis methods (some of which have not been previously applied to the study of auditory sentence processing) such as single-trial analyses and independent component decomposition, demonstrate the degree to which domain general mechanisms explain the language-related EEG