Assessing the development of automatic processing: an application of dual-task and event-related brain potential methodologies

Previous research has found that properties of automatic processing do not always co-occur, suggesting that the acquisition rates may differ. The present study investigated the acquisition rate of several of these properties by employing additive factors logic, dual task methodology, and event-related brain potentials. Seven subjects participated in a ten session experiment in which they performed two tasks, a visual/memory search task and a pursuit step tracking task, both together and separately. RT and P300 latency measures indicated that parallel processing of the display was achieved early in training in the consistent mapping condition. This processing was unaffected by dual task demands. An analysis of RT/P300 ratios suggests that another form of perceptual efficiency was achieved later in practice in both the varied and consistently mapped search tasks. This effect was larger in the consistent mapping condition. Reductions in the slope of the memory set function occurred significantly earlier for P300 latency than for RT, suggesting that the stimulus evaluation processes became automated more rapidly than the response selection components of memory search. Consistent with an analysis of the processing demands of the two tasks, the introduction of the tracking task and an increase in tracking difficulty produced equivalent interference during consistent and varied mapping conditions. Results are discussed in terms of models of skill, skill acquisition and component task automaticity.     

Event-related potentials during delayed recognition of Wechsler memory scale-R paired associate learning

The P300 is a component of cortical event related-potentials that has been linked to memory and recognition. This study examined P300 amplitude and latency during recognition of pairs of words from the WMS-R Verbal Paired Associate Learning subscale. After 24 subjects learned the pairs of words, they were shown pairs of words taken directly from the subscale that were combined to form matching or nonmatching pairs. This parallels the Delayed Recall subtest of the WMS-R. P300 amplitude was greater during recognition of matching word pairs and most prominent at central and parietal recording sites. P300 latency was shorter for matching than for non-matching pairs. This points to a degree of psychophysiological validity of the WMS-R paired associate learning delayed recall task.     

Combined effects of alcohol and caffeine on the late components of the event-related potential and on reaction time

The effects of .7 ml/kg alcohol and 200 mg caffeine on the P200, N200, P300 and N500 difference wave components of the event-related potential and on reaction time (RT) were examined in 16 females who performed both simple and choice RT tasks. Alcohol slowed the decision time (DT) component of reaction time, lengthened the latency of the P200 and P300 components, reduced N200 amplitude, increased P300 amplitude at parietal sites, and modified the effect of sagittal site on N500 difference wave peak amplitude. Caffeine shortened DT in the choice RT task, shortened N200 latency at right hemisphere sites, and shortened N200 latency in the choice RT task in combination with alcohol compared to when alcohol was administered alone. Caffeine also increased P300 amplitude in the choice RT task and reduced the integral of the N500 difference wave at most sites when combined with alcohol. It was concluded that whereas alcohol slows attention allocation and impairs working memory, caffeine accelerated response-related decisions and enhanced cortical arousal.     

P300, Food Consumption, and Memory Performance

The effects of food intake on the P300 (P3) component of the event-related brain potential (ERP) were assessed in two studies. Experiment 1 compared 24 subjects who had not eaten within 6 hours of testing with 24 subjects who had consumed food within 3 hours of testing. P3 target stimulus amplitude was reduced significantly for the subjects who had not eaten relative to those who had eaten, whereas peak P3 latency was only moderately affected by the recency of food consumption over task conditions. In Experiment 2, P3 measurements, memory performance in a word recall task, and blood glucose levels were obtained from 24 subjects at three different times: 1) after a 14-hour fast, 2) 5 min after consuming lunch, and 3) 30 min after consuming lunch. P3 target stimulus amplitude increased initially after food intake and decreased slightly at the third measurement time, while peak P3 latency became somewhat shorter immediately after food intake but then returned to baseline. Recall for recently presented items mimicked the P3 amplitude changes, whereas blood glucose levels increased monotonically across food conditions. The results from both studies suggest that: 1) target stimulus P3 amplitude is affected by the recency of food intake; 2) food-related P3 amplitude changes appear related to memory function; and 3) subjects should eat within several hours before ERPs are acquired to ensure that P3 component measurements reflect values indicative of normal bodily functioning.     

The Effects of Practice and Task Structure on Components of the Event-Related Brain Potential

The present study focused on the effects of, and the interactions between, practice and task structure on human performance. The development of automatic processing through consistent stimulus-response mapping (CM) was assessed by means of measures of reaction time and event-related brain potentials. The subjects performed a visual search task in which they responded by pressing a button whenever a probe matched a memory set item. The variables manipulated in the study included the number of memory set items (1 or 4), the task structure (CM or VM), and the probability of occurrence of a memory set item (.2 or .8). Set size had a significant effect on RT in both CM and VM conditions prior to practice and in the VM condition following extensive practice. P300 latency mirrored RT, suggesting that the development of automatic processing substantially reduced stimulus evaluation time. The commonly observed relationship between probability and P300 amplitude, with larger P300s elicited by infrequent events, was found in the VM conditions but not in the CM condition after practice. Two different negative components were affected by stimulus mismatch. The N200 component behaved in a similar manner during automatic and controlled processing. However, a late frontally negative component was sensitive to the degree of mismatch only during controlled processing.     

健康人事件相关电位及心理学相关性研究

目的：探讨不同年龄健康人听觉事件相关电位（ERP）及其与心理测验间关系。方法：对不同年龄组健康者进行听觉ERP检测，以"oddball序列"刺激从Cz点引出P3，测其波幅和潜伏期。对其中30名成人进行韦氏智力量表和记忆量表测验。结果：P3潜伏期以儿童期最短，并随年龄增长逐渐延长，P3波幅儿童期明显高于成年人。成年组P3潜伏期与总智商、记忆商、及某些分测验呈显著负相关，而P3波幅与心理测验无明显相关关系。结论：不同年龄者ERP正常值不同，ERP能够反映智能的某些方面，特别倾向于反映言语和记忆能力。     

On P300 measurement stability: habituation, intra-trial block variation, and ultradian rhythms

P300 event-related brain potentials (ERPs) were elicited using a simple discrimination task in which participants discriminated two different equiprobable visual stimuli with button-press responses (n = 20). A total of ten trial blocks were presented at 10-min intervals. P300 amplitude declined significantly, but peak latency did not change reliably across trial blocks. P300 amplitude demonstrated a reliable cyclical fluctuation across trial blocks, although P300 latency did not. Intra-trial block ERP variability was assessed by computing the correlation coefficients between the target and standard stimuli for amplitude and latency measures across participants within each trial block. P300 amplitude correlations were weakest at the Fz electrode, more strongly associated at Cz, and were most strongly correlated at Pz across trial blocks. P300 latency correlations were somewhat weaker and similar in strength across electrodes sites. The correlational patterns for both P300 amplitude and latency demonstrated reliable cyclical variation. The N100 component produced strong and consistent correlations for both amplitude and latency, whereas the P200 and N200 component measures evinced cyclical correlational patterns similar to the P300 across trial blocks. These results suggest that the stability of P300 and other component measures can vary appreciably within and across trial blocks in a manner that reflects ultradian variation in arousal level.     

Can working memory predict target-to-target interval effects in the P300?

It has been suggested that the P300 component of the ERP is an electrophysiological index of memory-updating processes associated with task-relevant stimuli. Component magnitude varies with the time separating target stimuli (target-to-target interval: TTI), with longer TTIs eliciting larger P300 amplitudes. According to the template-update perspective, TTI effects observable in the P300 reflect the updating of stimulus-templates in working memory (WM). The current study explored whether young adults' memory-task ability could predict TTI effects in P300. EEG activity was recorded from 50 university students (aged 18–25 years) while they completed an auditory equiprobable Go/NoGo task with manipulations of TTIs. Participants also completed a CogState® battery and were sorted according to their WM score. ERPs were analysed using a temporal PCA. Two P300 components, P3b and the Slow Wave, were found to linearly increase in amplitude to longer TTIs. This TTI effect differed between groups only for the P3b component: The high WM group showed a steeper increase in P3b amplitude with TTI than the low WM group. These results suggest that TTI effects in P300 are directly related to WM processes.     

Task Versus Component Consistency in the Development of Automatic Processing: A Psychophysiological Assessment

A study was conducted to examine the role of consistency in the development of automatic processing. Subjects performed a memory search task in which consistent and inconsistent attending and responding were factorially combined. The task was performed with memory set sizes of two and four items. Results indicated that automaticity developed with consistent attending regardless of whether responding was consistent or inconsistent. However, measures of reaction time, P300 latency, and P300 amplitude revealed costs for inconsistent responding that were attributed to both stimulus evaluation and response related processes. The results suggest that total task consistency is not necessary for the development of automatic processing. Instead, it appears that automaticity can develop for consistent task components even when stimulus-response consistency is not maintained across the entire task.     

Response mode and P300 from auditory stimuli

The P300 component of the event-related brain potential (ERP) was elicited with a simple auditory discrimination task. Subjects were required to respond in three different ways to target stimuli across conditions: (1) silently counting the targets; (2) tapping their index finger every time a target was detected; or (3) pressing a button with their thumb when a target was presented. In addition, ERPs were recorded during each response mode while the subjects' eyes were either open or closed. P300 amplitude was larger for the counting compared to the tapping or button press tasks especially during the eyes closed condition. The peak latency of the P300 was longer when obtained from the counting compared to the tapping and button-press tasks for both eye conditions. Response mode also interacted with electrode site for peak latency. The results suggest that the P300 ERP component is sensitive to the nature of the subject's response during discrimination tasks.     

The n-back as a dual-task: P300 morphology under divided attention

The n-back task was hypothesized to be a dual task, permitting the imposition of parametrically increasing attentional and working memory demands, while keeping constant the demands of an embedded matching subtask. Visual targets were presented for 200 ms every 2.2 s at pseudorandomly varying positions on a computer screen. Participants were required to remember the most recent 0, 1, 2, or 3 positions and responded with a choice button push to whether the current target position matched the position presented n items previously. P300 peak latency was constant across n-back tasks, reflecting constant perceptual and cognitive demands of the matching subtask. P300 peak amplitude decreased with increasing memory load, reflecting reallocation of attention and processing capacity away from the matching subtask to working memory activity. These data support a dual-task nature of the n-back, which should be considered when employing this paradigm.     

Genetic Influence on the Variance in P3 Amplitude and Latency

The P3(00) event-related potential (ERP) component is widely used as a measure of cognitive functioning and provides a sensitive electrophysiological index of the attentional and working memory demands of a task. This study investigated what proportion of the variance in the amplitude and latency of the P3, elicited in a delayed response working memory task, could be attributed to genetic factors. In 335 adolescent twin pairs and 48 siblings, the amplitude and latency of the P3 were examined at frontal, central, and parietal sites. Additive genetic factors accounted for 48% to 61% of the variance in P3 amplitude. Approximately one-third of the genetic variation at frontal sites was mediated by a common genetic factor that also influenced the genetic variation at parietal and central sites. Familial resemblance in P3 latency was due to genetic influence that accounted for 44% to 50% of the variance. Genetic covariance in P3 latency across sites was substantial, with a large part of the variance found at parietal, central, and frontal sites attributed to a common genetic factor. The findings provide further evidence that the P3 is a promising phenotype of neural activity of the brain and has the potential to be used in linkage and association analysis in the search for quantitative trait loci (QTLs) influencing cognition.     

On the search for the neurophysiological manifestation of recollective experience

M.E. Smith (1993) obtained event-related brain potentials (ERPs) from subjects performing a recognition memory task using "remember" (R) and "know" (K) judgments, and reported observing in the ERP a "neurophysiological manifestation of recollective experience" as a difference between the positive waveforms elicited by stimuli that yielded R and K judgments. We replicated his experiment and examined the componential structure of the R > K effect in two ways. First, we found that correction for P300 latency jitter eliminated the effect reported by Smith. Second, the application of principal component analysis indicated that the positive waveform elicited by the words in the test list was a P300. These analyses do not support the hypothesis that there is a new component (the "memory-evoked shift") that is a specific manifestation of recollection.     

P300 and Response Selection: A New Look Using Independent-Components Analysis

Purpose: The most prevalent current view of the functional role of the P300 component of the event-related potential (ERP) is that it indexes strategic processing related to context updating. Using independent-components analysis (ICA), the present study examined the role of P300 in the tactical process of response selection. Methods: In a task crossing manipulations of perceptual difficulty (PD) and response-selection difficulty (R-SD), ICA was employed to measure not only P300 latency, but its onset and duration as well. Results: Increased PD delayed P300 latency and onset in parallel, while increased R-SD lengthened P300 duration. Conclusions: The latency and onset results suggest that the often-cited covaration of P300 latency with stimulus-evaluation time is secondary to effects on processing stages preceding P300. The results for duration indicate that P300 is involved in response selection, suggesting that it is not a unitary phenomenon. While P300's well-known relation to stimulus probability indicates a strategic role, our findings indicate a tactical role as well.     

Meta-analysis of P300 and schizophrenia: patients, paradigms, and practical implications

The goal of the present meta-analysis was to identify factors that contribute to P300 event-related brain potential (ERP) differences in patients with schizophrenia compared to unaffected controls in an attempt to characterize the clinically relevant dimensions underlying P300 deficits in patients with schizophrenia. P300 effect size (d) was smaller in amplitude and longer in latency in schizophrenic patients compared to normal controls, with the strongest effects obtained from the auditory oddball. Paranoid subtype demonstrated larger P300 amplitude effect sizes than other disease subtypes, and P300 latency effect size decreased with disease duration. Psychopathology severity and antipsychotic medications were unrelated to P300 amplitude effect size. Gender proportion, educational level, and stimulus and task variables also affected P300 amplitude and latency effect sizes. The findings are used to formulate a theoretical account of the empirical data and provide suggestions for maximizing the utility of the P300 component in the assessment of schizophrenia.     

On the Dependence of P300 Latency on Stimulus Evaluation Processes

McCarthy and Donchin (1981) found that the latency of a late positive component of the event-related potential (ERP) was influenced by the presence of noise in a stimulus matrix but not by the compatibility between the stimulus presented and the response required. They concluded that this component is a P300 and that its latency was influenced by stimulus evaluation but not by response selection processes. The present experiments were designed to confirm that the component identified by McCarthy and Donchin was indeed a P300 and to determine if its latency varies systematically with increases in stimulus evaluation time produced by graded changes in noise level. In Experiment 1, subjects performed a standard oddball task in which they were required to count the rarer of two stimuli (the words RIGHT or LEFT) which were, or were not, embedded in a noise matrix (characters from the alphabet). The positive component of the ERP, whose amplitude was larger for rare target stimuli, was labeled a P300, and the latency of this component was longer when the stimuli were embedded in noise. In Experiment 2, subjects performed a choice reaction time task. Following the procedures used by McCarthy and Donchin, stimulus words RIGHT and LEFT required right or left hand responses depending on the presence of a cue word SAME or OPPOSITE which preceded the stimulus. Stimulus words were presented in four different degrees of noise, the levels of which were manipulated by varying the set size of the alphabetic characters which could surround the stimulus words. Reaction time increased both with noise (by 325 ms) and as a function of stimulus-response incompatibility (by 127 ms). In contrast, P300 latency increased substantially with noise (by 200 ms) but, to a much lesser extent (by 14 ms), with response incompatibility. These results indicate that the P300 is sensitive to the ease with which a target stimulus can be discriminated from noise. They confirm that P300 latency can be used as a measure of the timing of stimulus evaluation processes that is relatively independent of response selection and execution.     

P300 and Long-Term Memory: Latency Predicts Recognition Performance

The study-test paradigm was used to investigate memory acquisition processes and the effects of repetition on long-term recognition memory. In this procedure, subjects are presented with a list of words (“targets”) to be memorized (Study series). They are later tested for recognition on a word list comprised of the target words mixed randomly with an equal number of new, distractor words (Test series). Both reaction time and the P300 component of the event-related brain potential were used as measures of processing time. During the Study series, large P300s were elicited despite a word category probability of 1.0. When the words from the Study series were divided on the basis of recognition performance, words that were subsequently recognized elicited P300s with shorter latencies than unrecognized words. P300 amplitude to words in the Study series increased with repetition while maintaining a constant latency. During the Test series, P300 latency and reaction time decreased with repetition for both target and distractor words. P300 amplitude to all words increased substantially over Test repetitions with target words eliciting larger P300s than distractor words. Words that were recognized more consistently during the Test series elicited larger and earlier P300s than words that were recognized less consistently. The P300 amplitude and latency results from both the Study and Test series are interpreted as reflecting the increased discriminability of the target words as the memory trace increases in strength.     

Effects of task complexity in young and old adults: reaction time and P300 latency are not always dissociated

Twelve young and 11 elderly men (mean ages 21.1 and 70.1) performed a choice-reaction time (RT) task in which stimulus degradation and stimulus-response (S-R) compatibility were manipulated. The extant literature has suggested that the effects of age on RT are usually augmented (multiplicative) in more difficult task conditions, but also that the effects of age on the latency of the P300 component of the event-related brain potential (ERP) are constant (additive). The results indicated that the effects of age on RT were enhanced in more difficult conditions, whether the difficulty consisted of stimulus degradation or S-R incompatibility. However, the effects of age on P300 latency were enlarged as the stimuli were degraded, but not if the S-R mapping was incompatible. Thus, it appears that task content determines if effects of age on P300 latency are additive or multiplicative. A simple model is proposed that produces the obtained pattern of effects.     

Cognitive brain potentials and psychological deficits in Alzheimer's dementia and Korsakoff's amnesic syndrome

Auditory-event-related potentials, including the P300 response, were recorded from 20 patients with Alzheimer-type dementia (ATD), 17 patients with Korsakoff's syndrome (KS) and 23 age-matched control subjects. Each of the subjects was assessed using a version of the Luria Neuropsychological Investigation. Prolonged P300 latency and reduced P300 latency and reduced P300 amplitude, which are features of normal ageing and which also occur, to a greater degree, in ATD, correlated significantly with degree of impairment of language ability in both Alzheimer patients and controls. On the other hand, the association between P300 latency changes and various tests of memory was not consistent across the three subject groups; there was a significant negative correlation between P300 latency and visual memory in ATD and a significant positive correlation in KS, whereas in controls no significant correlation was found. By contrast, P300 latency and memory for words were significantly negatively correlated in controls, but in neither of the patient groups. Detailed studies of language function may further elucidate the complex relationships between neuropsychological measures and P300 changes in normal ageing and dementia.     

Auditory event-related potential abnormalities in bipolar disorder and schizophrenia.

Auditory P300 latency prolongation or amplitude reduction has been reported in patients affected by bipolar disorder and in schizophrenia. The purpose of this study was to test whether the auditory P300 and earlier event-related potential (ERP) components elicited during an auditory discrimination task could differentiate between these two disorders. Thirteen patients with manic or mixed bipolar disorder, 12 patients with schizophrenia, and 24 control subjects were evaluated. None of the subjects had a history of alcohol or substance abuse or dependence. ERPs were elicited during an auditory discrimination task in which a subject pressed a key to infrequent 1500 Hz tones interspersed amid a series of 1000 Hz tones. The amplitude and latency of N100 and P200 were measured from ERPs to non-target tones, and N200 and P300 were measured from ERPs to target tones. N100, P200 and N200 amplitudes were reduced in schizophrenia patients, but not in bipolar patients. Both bipolar disorder and schizophrenia patients showed reduced P300 amplitude and prolonged P300 latency. Amplitude reduction in the early ERP components implicates auditory processing deficits in schizophrenia. Both groups showed reductions in P300 amplitude, suggesting a disturbance of the temporal-parietal generators of this component. Prolonged P300 latency is consistent with impaired attentional processing in schizophrenia and symptomatic bipolar disorder patients.