The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but precede the start of motor programming.     

Extending General Processing Tree Models to Analyze Reaction Time Experiments

General processing tree (GPT) models are usually used to analyze categorical data collected in psychological experiments. Such models assume functional relations between probabilities of the observed behavior categories and the unobservable choice probabilities involved in a cognitive task. This paper extends GPT models for categorical data to the analysis of continuous data in a class of response time (RT) experiments in cognitive psychology. Suppose that a cognitive task involves several discrete processing stages and both accuracy (categorical) and latency (continuous) measures are obtained for each of the response categories. Furthermore, suppose that the task can be modeled by a GPT model that assumes serialization among the stages. The observed latencies of the response categories are functions of the choice probabilities and processing times (PT) at each of the processing stages. The functional relations are determined by the processing structure of the task. A general framework is presented and it is applied to a set of data obtained from a source monitoring experiment. Copyright 2001 Academic Press.     

Mental ability,P300, and mismatch negativity: Analysis of frequency and duration discrimination

Individual differences in mental ability (MA) were examined with event-related potentials (ERP). In addition to using an auditory frequency discrimination task, a duration discrimination task was used to elicit P300 and mismatch negativity (MMN) components of the ERP. Frequency and duration P300 latencies explained 9% and 10% of variance of MAB performance scores independently of each other and commonly 28% of variance. The finding that duration P300 latency explained variance of MA independent of that explained by frequency P300 latency, suggests that temporal information processing is partly dissociable from processing of frequency information in its prediction of MA. Duration and frequency MMNs were shown to be indices of discrimination ability and predicted 11% of variance of MAB performance scores. The outcome of the present study not only emphasizes the importance of both mental speed and discrimination ability for MA but also points to the significance of duration- and frequency-related ERP measures for the understanding of underlying brain mechanisms.     

Speed of processing of the visual-orthographic and auditory-phonological systems in adult dyslexics: the contribution of "asynchrony" to word recognition deficits

This study investigated whether "asynchrony" in speed of processing (SOP) between the visual-orthographic and auditory-phonological modalities contributes to word recognition deficits among adult dyslexics. Male university students with a history of diagnosed dyslexia were compared to age-matched normal readers on a variety of experimental measures while event-related potentials and reaction time data were collected. Measures were designed to evaluate auditory and visual processing for non-linguistic (tones and shapes) and linguistic (phonemes and graphemes) low-level stimuli as well as higher-level orthographic and phonological processing (in a lexical decision task). Data indicated that adult dyslexic readers had significantly slower reaction times and longer P300 latencies than control readers in most of the experimental tasks and delayed P200 latencies for the lexical decision task. Moreover, adult dyslexics revealed a systematic SOP gap in P300 latency between the auditory/phonological and visual/orthographic processing measures. Our data support and extend previous work that found SOP asynchrony to be an underlying factor of childhood dyslexia. The present data suggests, however, that among adult dyslexics the between modalities asynchrony occurs at later processing stages than in children.     

Tracking the influence of reflexive attention on sensory and cognitive processing

Previously, we demonstrated that reflexive attention facilitates early visual processing during form discrimination (Hopfinger & Mangun, 1998). In the present study, we tested whether reflexive facilitation of early visual processing will be generated when task load is low (simple luminance detection). Target stimuli that were preceded at short cue-to-target intervals by irrelevant visual events (cues) elicited an enhanced sensory (P1) event-related potential (ERP) component as well as an enhanced longer latency, cognitive ERP component (P300). At long cue-to-target intervals, facilitation in these ERP components was no longer observed, and, although inhibition of return (IOR) was observed in reaction times, the ERPs did not show an inhibition of sensory processing. These results provide converging evidence that reflexive attention transiently facilitates neural processing of visual inputs at multiple stages of analysis (i.e., sensory processing and higher order cognitive processing) but question the view that IOR is manifest at the earliest visual cortical stages of analysis.     

Mental slowing in elderly persons: a cognitive psychophysiological analysis

In recent attempts to formulate an integrative model of mental slowing in elderly persons, regression analyses have been done in which reaction-time data from a large number of studies spanning a broad range of speeded decision-making tasks were combined. The results of these meta-analyses were then used to support the conclusion that there is a generalized, proportional decline in mental processing speed among elderly adults that affects all elements of mentation equally. We present a series of similar regression analyses in which both reaction time and the latency of the P300 component of the event-related brain potential are included. The results of these analyses indicate that there are elements of mental processing that may be slowed additively, not proportionately, in older persons. Furthermore, the results raise some questions about the logic underlying the interpretation of the meta-regression analysis.     

A diffusion model account of normal and impaired readers

Acquired aphasics and dyslexics with even very profound word reading impairments have been shown to perform relatively well on the lexical decision task, but direct contrasts with unimpaired participant's data is often complicated by extremely long reaction times for patient data. The dissociation between lexical decision and word naming performance shown by these patients is of theoretical importance, and here we present an analysis of processing underlying the lexical decision task. We are able to determine what aspects of performance are affected by acquired aphasics in the lexical decision task. We fit lexical decision data from aphasic patients and from normal readers with a sequential sampling model (the diffusion model) that simultaneously considers reaction time and accuracy. This model provides a powerful means of assessing processes involved in impaired and unimpaired lexical decision. Our results suggest that lexical decision may tap impairments at both a linguistic and a nonlinguistic level. These impairments combine to make patients produce the exaggerated lexical decision reaction times typical of neurolinguistic patients: we demonstrate that patients have compromised decision and nondecision processes but that the quality of the information upon which they base their decisions is not much different from that of unimpaired participants.     

Hemodynamic and electrophysiological relationship involved in human face processing: evidence from a combined fMRI-ERP study

Functional magnetic resonance imaging (fMRI) and event-related potential (ERP) experiments were conducted in the same group of subjects and with an identical task paradigm to investigate a possible relationship between hemodynamic and electrophysiological responses within the brain. The subjects were instructed to judge whether visually presented stimuli were faces or houses and then press the corresponding button. Functional MRI identified face- and house-related regions in the lateral and medial part of the fusiform gyrus, respectively, while ERP showed significantly greater N170 negativity for face than for house stimuli in the temporo-occipital electrodes. Correlation analysis between the BOLD signal in the fusiform gyrus and ERP parameters demonstrated a close relationship between the signal and both latency and amplitude of N170 across the subjects. These correlations may indicate that the variation in cognitive demand and hemodynamic responses during the face/house discrimination task is coupled with the variation of N170 peak latency/amplitude across the subjects. Thus, integrative analysis of spatial and temporal information obtained from the two experimental modalities may help in studying neural correlates involved in a particular cognitive task.     

Change in intraindividual variability over time as a key metric for defining performance-based cognitive fatigability

Cognitive fatigability is conventionally quantified as the increase over time in either mean reaction time (RT) or error rate from two or more time periods during sustained performance of a prolonged cognitive task. There is evidence indicating that these mean performance measures may not sufficiently reflect the response characteristics of cognitive fatigue. We hypothesized that changes in intraindividual variability over time would be a more sensitive and ecologically meaningful metric for investigations of fatigability of cognitive performance. To test the hypothesis fifteen young adults were recruited. Trait fatigue perceptions in various domains were assessed with the Multidimensional Fatigue Index (MFI). Behavioral data were then recorded during performance of a three-hour continuous cued Stroop task. Results showed that intraindividual variability, as quantified by the coefficient of variation of RT, increased linearly over the course of three hours and demonstrated a significantly greater effect size than mean RT or accuracy. Change in intraindividual RT variability over time was significantly correlated with relevant subscores of the MFI including reduced activity, reduced motivation and mental fatigue. While change in mean RT over time was also correlated with reduced motivation and mental fatigue, these correlations were significantly smaller than those associated with intraindividual RT variability. RT distribution analysis using an ex-Gaussian model further revealed that change in intraindividual variability over time reflects an increase in the exponential component of variance and may reflect attentional lapses or other breakdowns in cognitive control. These results suggest that intraindividual variability and its change over time provide important metrics for measuring cognitive fatigability and may prove useful for inferring the underlying neuronal mechanisms of both perceptions of fatigue and objective changes in performance.     

Time pressure effects on information processing in overlapping tasks: evidence from the lateralized readiness potential

Information processing is impaired when two tasks are performed concurrently. The interference between the tasks is commonly attributed to structural bottlenecks or strategic scheduling of information processing. The present experiment investigated the effects of time pressure for the second of two responses on information processing in overlapping tasks by recording the lateralized readiness potential (LRP). Time pressure shortened the latency of the second response by diminishing the time devoted to motoric processing. In addition, task interference decreased under time pressure, which is probably due to the relatively early availability of the central bottleneck stage rather than to increased overlap of central stages. The LRP also provided direct evidence for an additional bottleneck following response selection, possibly due to supramodal refractoriness of response initiation.     

卡通面孔分类与识别加工的ERP比较研究

通过ERP方法,考察卡通面孔分类（人和动物）的脑机制及其与卡通面孔识别（人与车）的差异。结果表明,分类任务中,动物面孔VPP潜伏期显著长于人,N170潜伏期主效应不显著、波幅半球效应显著,LPP波幅在顶叶和中央区最大;分类任务VPP和LPP波幅均显著大于识别。结论：卡通面孔分类比识别速度慢、强度大,消耗心理资源多。顶叶和中央区可能是执行分类任务的主要脑区,且加工人类面孔具有优势。面孔加工中结构编码和特征编码可能部分是并行的。     

Extroversion-related differences in speed of premotor and motor processing as revealed by lateralized readiness potentials

To further elucidate extroversion-related differences in speed of sensorimotor processing, the authors obtained behavioral and psychophysiological measures as participants (16 introverts and 16 extroverts) performed a visual go/no-go task. Although no extroversion-related differences in reaction time emerged, introverts showed faster premotor processing but slower central and peripheral motor processing--as indicated by latencies of the lateralized readiness potential (LRP) and electromyographic (EMG) data, respectively--than extroverts did. Additional regression analyses revealed that stimulus-locked LRP latency, response-locked LRP latency, and Nl EMG amplitude accounted for 40% of overall variability in individual extroversion scores. On the basis of the present results, the authors introduce a compensation hypothesis that accounts for the common failure of researchers to demonstrate extroversion-related differences in reaction time. The present results challenge J. Brebner and C. Cooper's (1985) model of extroversion in which stimulus analysis is not slower in introverts than in extroverts. However, the present findings support the assumption of faster motor processing in extroverts.     

Attention network test: Assessment of cognitive function in chronic fatigue syndrome

Information processing difficulties are common in patients with chronic fatigue syndrome (CFS). It has been shown that the time it takes to process a complex cognitive task, rather than error rate, may be the critical variable underlying CFS patients' cognitive complaints. The Attention Network Task (ANT) developed by Fan and colleagues may be of clinical utility to assess cognitive function in CFS, because it allows for simultaneous assessment of mental response speed, also called information processing speed, and error rate under three conditions challenging the attention system. Comparison of data from two groups of CFS patients (those with and without comorbid major depressive disorder; n = 19 and 22, respectively) to controls (n = 29) consistently showed that error rates did not differ among groups across conditions, but speed of information processing did. Processing time was prolonged in both CFS groups and most significantly affected in response to the most complex task conditions. For simpler tasks, processing time was only prolonged in CFS participants with depression. The data suggest that the ANT may be a task that could be used clinically to assess information processing deficits in individuals with CFS.     

Analysis of information processing stages using event-related potentials.

The event-related potential (ERP) was recorded to identify the time epochs during which different independent variables have their effects on stages in a memory search task. Stimulus intensity, memory set size and response type were varied. For the most part, the order and timing of effects (evaluated by Principal Components Analysis of within-subjects ERP differences) were consistent with the presumed underlying stages, except for early effects of response type prior to memory set effects (suggesting precategorical target recognition). The usefulness of this type of analysis for the investigation of information processing stages is discussed.     

Visual load and variability of muscle activation: Effects on reactive driving of older adults

BackgroundThe functional significance of the increase in motor output variability with increased visual information processing in older adults remains unclear. Here, we test the hypothesis that increased visual information processing increases muscle activation variability in older adults and impairs their ability to react as fast and as precisely as young adults during a simulated reactive driving task.MethodsFourteen young and sixteen older adults performed a reactive driving simulation task that required responding to unexpected brake lights of the car ahead during a simple reaction time task (low visual information processing condition) and a choice reaction time task with “no go” trials condition (high visual information processing condition). We quantified the following: 1) reactive driving performance – combination of premotor response time, motor response time, and brake force error; 2) motor output variability – brake impulse variability; 3) muscle activation variability – variability in the tibialis anterior (TA) muscle activity.ResultsThe increase in information processing exacerbated the impaired reactive driving performance in older adults. The best predictor of this impairment was the increase in brake force error. The impaired reactive driving performance was related to brake impulse variability and variability in the TA activity.ConclusionsThis study provides novel evidence that increased information processing increases muscle activation variability in older adults with detrimental consequences to their ability to perform a simulated reactive driving task.     

Speed of phonological and orthographic processing as factors in dyslexia: electrophysiological evidence

The author investigated the hypothesis that speed of processing in the phonological and orthographic systems is one of the underlying variables of word-reading effectiveness. Speed of processing was assessed using measures of behavioral reaction time and electrophysiological latencies during phonological and orthographic task performance. Participants were 20 dyslexic and 20 normal-reading, male college students. An electrophysiological component complex (N1-P2-N2), as well as 2 other components (P3 and N4), was identified in both groups on each of the experimental tasks. Significant group differences were obtained only on the phonological tasks. Speed of processing during phonological judgment tasks was significantly prolonged among the dyslexic readers compared with the controls as reflected by P2, P3, and N4 latencies and reaction time. Between-task comparisons revealed significantly prolonged P2, P3, and N4 latencies on phonological compared with orthographic tasks in both dyslexic and normal readers, indicating that phonological classification of words may demand more time than orthographic classification. However, the gap score between speed of processing on the phonological and orthographic tasks was larger among the dyslexic readers and was observed mainly in P3 latency and reaction time. The highest correlation between word-reading accuracy score and the experimental measures was obtained in the dyslexic group with P3 latency gap score and in the control group with P2 latency gap score. The author proposes that slow phonological processing may cause "asynchrony" between the processing speeds within and between phonological and orthographic systems and may lead to a lack of efficient integration among the various subprocesses activated in reading, may slow down reading rate, and may impair word-reading effectiveness.     

Executive working memory load induces inattentional blindness

When attention is engaged in a task, unexpected events in the visual scene may go undetected, a phenomenon known as inattentional blindness (IB). At what stage of information processing must attention be engaged for IB to occur? Although manipulations that tax visuospatial attention can induce IB, the evidence is more equivocal for tasks that engage attention at late, central stages of information processing. Here, we tested whether IB can be specifically induced by central executive processes. An unexpected visual stimulus was presented during the retention interval of a working memory task that involved either simply maintaining verbal material or rearranging the material into alphabetical order. The unexpected stimulus was more likely to be missed during manipulation than during simple maintenance of the verbal information. Thus, the engagement of executive processes impairs the ability to detect unexpected, task-irrelevant stimuli, suggesting that IB can result from central, amodal stages of processing.     

Dissociable stages of problem solving (II): first evidence for process-contingent temporal order of activation in dorsolateral prefrontal cortex

In a companion study, eye-movement analyses in the Tower of London task (TOL) revealed independent indicators of functionally separable cognitive processes during problem solving, with processes of building up an internal representation of the problem preceding actual planning processes. These results imply that processes of internalization and planning should also be distinguishable in time and space with respect to concomitant brain activation patterns. To investigate this possibility, here we conducted analyses of fMRI data for left and right dorsolateral prefrontal cortex (dlPFC) during problem solving in the TOL task by accounting for the trial-by-trial variability of onsets and durations of the different cognitive processing stages. Comparisons between stimulus-locked and response-locked modeling approaches affirmed that activation in left dlPFC was elicited particularly during early processes of internalization, comprising the extraction of goal information and the generation of an internal problem representation, whereas activation in right dlPFC was predominantly attributable to later processes of mental transformations on this representation, that is planning proper. Thus, present data corroborate the proposal that often observed bilateral dlPFC activation patterns during complex cognitive tasks such as problem solving may reflect functionally and, to some extent, even temporally separable processes with opposing lateralizations.     

Attentional blink and impulsiveness: evidence for higher functional impulsivity in non-blinkers compared to blinkers

The attentional blink (AB) represents a fundamental limit of information processing. About 5–10 % of all subjects, however, do not show the AB. Because of the low base rate of these so-called non-blinkers, studies on mechanisms underlying non-blinkers’ absent AB are extremely scant. The few existent studies found non-blinkers to be faster and more efficient in information processing compared to blinkers. A personality trait that has been linked previously to speed and efficiency of information processing as well as to the magnitude of the AB is impulsivity. Therefore, the present study investigated whether 15 non-blinkers and 15 blinkers differed from each other in functional and/or dysfunctional impulsivity. To obtain a better understanding of the underlying processing mechanisms, the P300 component in the event-related potential was recorded during performance on the AB task. Our results indicated higher functional impulsivity in non-blinkers compared to blinkers but no differences between the two groups in dysfunctional impulsivity. As indicated by shorter P300 latency, non-blinkers processed information faster than blinkers after the AB period but slower during the AB period. These speed effects, however, were not associated with functional impulsivity. Thus, impulsivity and speed of information processing appear to represent two rather independent sources for non-blinkers’ absent AB.     

Electrophysiological evidence reveals affective evaluation deficits early in stimulus processing in patients with panic disorder

Cognitive and neurobiological accounts of clinical anxiety and depression were examined via event-related brain potentials (ERPs) recorded from patients with panic disorder and healthy controls as they performed an old/new recognition memory task with emotionally negative and neutral words. The emotive connotation of words systematically influenced control subjects' - but not patients' - ERP effects at prefrontal sites in a latency range (to approximately 300-500 ms) generally assumed to reflect greater contribution of automatic than controlled memory processes. This provides evidence for dysfunctional inhibitory modulation of affective information processing in panic disorder. The ERP effects after 700 ms, however, suggest that some patients may adopt conscious strategies to minimize the impact of these early processing abnormalities on overt behaviors.