On the conceptual foundations of cognitive psychophysiology

The P300 Auditory Event-Related Potential May Predict Segregation of Competing Speech by Bimodal Cochlear Implant Listeners

Compared to normal-hearing (NH) listeners, cochlear implant (CI) listeners have greater difficulty segregating competing speech. Neurophysiological studies have largely investigated the neural foundations for CI listeners' speech recognition in quiet, mainly using the P300 component of event-related potentials (ERPs). P300 is closely related to cognitive processes involving auditory discrimination, selective attention, and working memory. Different from speech perception in quiet, little is known about the neurophysiological foundations for segregation of competing speech by CI listeners. In this study, ERPs were measured for a 1 vs. 2 kHz contrast in 11 Mandarin-speaking bimodal CI listeners and 11 NH listeners. Speech reception thresholds (SRTs) for a male target talker were measured in steady noise or with a male or female masker. Results showed that P300 amplitudes were significantly larger and latencies were significantly shorter for the NH than for the CI group. Similarly, SRTs were significantly better for the NH than for the CI group. Across all participants, P300 amplitude was significantly correlated with SRTs in steady noise (r = -0.65, p = 0.001) and with the competing male (r = -0.62, p = 0.002) and female maskers (r = -0.60, p = 0.003). Within the CI group, there was a significant correlation between P300 amplitude and SRTs with the male masker (r = -0.78, p = 0.005), which produced the most informational masking. The results suggest that P300 amplitude may be a clinically useful neural correlate of central auditory processing capabilities (e.g., susceptibility to informational masking) in bimodal CI patients.

An ERP investigation of the working memory stroop effect

This study aimed to explore the neural activity associated with the Working Memory (WM) Stroop effect. Stroop facilitation and interference effects in WM were also investigated by adding a neutral condition to the WM Stroop paradigm. In each trial, participants were first asked to remember a word in WM, then respond to the color of the subsequent rectangle. The word meaning and rectangular color were congruent, incongruent, or irrelevant (neutral). Finally, a probe word appeared and participants judged whether it was the same as the first presented word. For the color decision task, behavioral results showed that 1) RTs were longer for the incongruent than congruent condition, indicating a WM Stroop effect; 2) RTs were shorter for the congruent than neutral condition, indicating a WM Stroop facilitation effect; and 3) RTs were shorter for the incongruent than neutral condition, indicating no Stroop interference effect in WM. ERPs locked to the rectangle revealed that 1) greater N2 and P3 activity was evoked for the incongruent than congruent condition, indicating more intensive conflict detection and conflict resolution processes for the incongruent condition; and 2) enhanced N2 but decreased P3 components were evoked for the neutral than the congruent and incongruent conditions, indicating a more intensive conflict monitoring process but decreased conflict resolution process for the neutral condition. These results demonstrate that when WM content is congruent with the attention task, it can facilitate attention, but WM content may not interfere with attention when they are incongruent.

The P300 auditory event-related potential as a method to assess the benefit of contralateral hearing aid use in bimodal listeners: a proof-of-concept

Objective: Bimodal listeners vary in the amount of benefit they receive from wearing the contralateral hearing aid. This may partially depend on the listener's auditory processing capacities. The current study explores whether the P300 event-related potential can provide insight into the mechanisms underlying the benefits of wearing a contralateral hearing aid.Design: P300s were recorded using an oddball paradigm with 500 and 250 Hz tone-bursts as standard and deviant stimuli, respectively. Subjects counted the number of deviants - a measure of performance. N2b latencies, P300 latencies, N2b-P300 amplitudes, and performance were assessed during CI-only and bimodal listening.Study sample: Five bimodal listeners.Results: P300s were present in four subjects. Amplitudes were larger during bimodal listening (bimodal: 22.3 ± 4.83 µV, CI-only: 13.1 ± 3.86 µV). Both N2b and P300 latencies were shorter during bimodal (N2b: 265 ± 20.0 ms, P300: 551 ± 129.4 ms) than CI-only listening (N2b: 326 ± 42.2 ms, P300: 402 ± 38.4 ms). While performance often reached ceiling level, the difference between the standard and deviant was generally more salient during bimodal listening.Conclusions: This study provides a proof-of-concept, suggesting that P300s may provide insight into benefits that are not always measurable with behavioural tasks.

The neurophysiology of working memory development: from childhood to adolescence and young adulthood

Working memory (WM) is an important cognitive function that is necessary to perform our daily activities. The present review briefly describes the most accepted models underlying WM and the neural networks involved in its processing. The review focuses on how the neurophysiological mechanisms develop with age in the periods from childhood to adolescence and young adulthood. Studies using behavioral, neuroimaging, and electrophysiological techniques showed the progress of WM throughout the development. The present review focuses on the neurophysiology of the basic processes underlying WM operations, as indicated by electroencephalogram-derived signals, in order to take advantage of the excellent time resolution of this technique. Children and adults use similar cerebral mechanisms and areas to encode, recognize, and keep the stimuli in memory and update the WM contents, although adults rely more on anterior sites. The possibility that a functional reorganization of WM brain processing occurs around the adolescent period is suggested, and would partly justify the high prevalence of the emergence of mental pathology in the adolescent period.

History of concussion impacts electrophysiological correlates of working memory

Sports-related concussions occur in approximately 21% of college athletes with implications for long-term cognitive impairments in working memory. Working memory involves the capacity to maintain short-term information and integrate with higher-order cognitive processing for planning and behavior execution, critical skills for optimal cognitive and athletic performance. This study quantified working memory impairments in 36 American football college athletes (18-23years old) using event-related potentials (ERPs). Despite performing similarly in a standard 2-back working memory task, athletes with history of concussion exhibited larger P1 and P3 amplitudes compared to Controls. Concussion History group latencies were slower for the P1 and faster for the N2. Source estimation analyses indicated that previously concussed athletes engaged different brain regions compared to athletes with no concussion history. These findings suggest that ERPs may be a sensitive and objective measure to detect long-term cognitive consequences of concussion.

Differences in processing violations of sequential and feature regularities as revealed by visual event-related brain potentials

Identifying novel or unexpected events which violate predictions based on the regularities extracted from our environment is crucially important for adaptive behavior. However, the exact dynamics of processing such events is not well understood. Furthermore, it is not known in which degree the process of deviant detection differs across contexts and how much it depends on the characteristics of deviant events. This issue was addressed by the present study which used event-related potentials (ERPs) in order to investigate the dynamics of identifying two types of deviants presented within the same visual setting. These events violated expectations based on two different types of information contained within each trial, either temporal order of stimulus presentation (sequential deviant) or physical attributes shared by the majority of individual stimuli (feature deviant). The obtained results indicate a certain degree of similarity in detecting two deviant types which, when task-relevant, both elicited N2 and P3b event-related potential components. However, significant differences across different stages of their processing were also identified. First, only feature, but not sequential deviants elicited an N1 enhancement. Furthermore, N2 and P3b responses elicited by sequential and feature deviants differed in their latency and topography and, in case of P3b, amplitude. Taken together, these results suggest that the dynamics of detecting different types of deviants strongly depends on the specific characteristics of such events. Furthermore, the identified differences in the topography of N2 and P3b indicate distinct mechanisms underlying several stages of their processing.

Event-related potential correlates of judgment categories and detection sensitivity in a visual detection task

Event-related potentials were recorded from human subjects performing a visual detection task to find correlates of detection performance (d' and beta) in accordance with the theory of signal detection. Two spatial frequencies of square waves shifted horizontally with three shifting-step varieties were presented to the subjects who reported whether or not the waves were perceived to shift. Although three components of N1, P2, and P3 were observed for all of four response categories of hit, miss, false alarm, and correct rejection, only the amplitudes of the P3 component at vertex and parietal sites highly correlated to the detection sensitivity of d'. It was also found that coefficients of correlation between the P3 amplitudes at these sites and observed hit and false alarm rates were highly significant and a d'-extrapolation value reproduced by the normalized P3 amplitudes and the usual d' indicated a highly linear trend. Results suggest that generation of the P3 component is associated with "threshold-modulating" mechanisms which determine detection sensitivity of a task for each perceptual event.

Effect of the relevance and position of the target stimuli on P300 and reaction time

The relationships among stimulus relevance and the position of target stimuli in a sequence with the P300 component of event related brain potentials and reaction time were investigated. An auditory oddball series was presented to 42 healthy, young, right-handed female participants. In the series, participants were to ignore the standard stimuli and count the deviants from 1 to 6. When reaching the count of 6, they had to restart their count from 1 again. While counting, half of the sample had to press a key after the deviants, numbers 1, 2 and 3, but not after the numbers 4, 5 and 6. The other half of the sample had to press the key when numbers 4, 5 and 6 rather than when numbers 1, 2, 3 appeared. The P300 amplitude of the more relevant (count and press) stimuli was higher than that of the P300 amplitude of the less relevant (count only) stimuli. This is associated with a greater allocation of cognitive resources to the more relevant stimuli. An interaction was also found between the position of the target stimuli in a sequence and the stimulus relevance, which is attributed to the cognitive preparation. Furthermore, the reaction time tended to increase along the sequence of the more relevant stimuli, due perhaps to an increase in physical fatigue.

Event-related desynchronization during an auditory oddball task

OBJECTIVE

The present study addressed what kind of mental processes would be presented by the event-related desynchronization (ERD) relevant to the stimuli of an auditory oddball count task.

METHODS

Electroencephalogram (EEG) was recorded from nine healthy subjects while target tones (2000 Hz, P = 0.2) and non-target tones (1000 Hz, P = 0.8) were presented randomly with constant stimulus onset asynchrony (SOA) of 3.3 s. To improve time resolution of ERD analysis, obtained EEG epochs were digitally convoluted by Gabor wavelet and averaged respectively.

RESULTS

For target stimulus, prominent ERD was observed in left parieto-occipital areas (peak latency: 400-600 ms), but there were no significant ERD for non-target stimulus.

CONCLUSION

Our result suggests that magnitude of ERD would reflect amount of mental effort which was associated with intentional and voluntary processes rather than automatically sensory process.

Stimulus probability and event-related potentials of the brain in 6-month-old human infants: a parametric study

The effects of a priori stimulus probability and local-stimulus sequences on the Nc, NSW and Pc components of the event-related brain potentials were studied in six groups of 6-month-old human infants. Predictions from memory, expectancy and attentional accounts of the Nc, NSW and Pc components were examined using an infant-control oddball paradigm in which visual stimuli were presented across groups, at 0.90/0.10, 0.80/0.20, 0.70/0.30, 0.60/0.40, 0.50/0.50 (alternation) and 0.50/0.50 (random) probabilities. The main results indicated that stimulus probabilities and local-stimulus sequences affected Nc amplitude and latency, NSW amplitude but not the Pc component. Concurrent visual fixation performance was also found to be influenced by stimulus probabilities. The results were discussed in terms of the predictions from memory, expectancy and attentional accounts of the infant late components.

A 'passive' event-related potential?

Event potentials (ERPs) were recorded in response to visual patterns in two conditions: (1) where no instructions were given to subjects; and (2) where subjects pressed a button whenever a rare stimulus was detected. P3 amplitudes for the No Instructions condition were smaller than for the Active condition, but the latency of the P3s did not differ across conditions. In both conditions, the P3 was either absent or significantly smaller for frequent stimuli than for rare stimuli. It appears a 'passive' visual P3 is measurable, and it occurs at the same latency as a P3 recorded in association with an active response. Thus, it may be possible to record P3s in response to visual stimulation in subjects who cannot follow instructions to respond to rare events.

A MEG analysis of the P300 in visual discrimination tasks

Based on recent research that indicated that P300 scalp topography varies as a function of task and/or information to be processed, this study examined scalp-recorded magnetic fields correlated with the P300 by means of whole-head magnetoencephalography. Subjects performed two discrimination tasks, in which targets, defined on either object or spatial characteristics of the same visual stimuli, had to be discriminated. Based on the across-subject root mean square (RMS) functions a sequence of 4 components could be identified in both tasks, N1m, P3m, and two later components, which, based on their estimated neuronal sources, were classified as representing motor processes during and following the manual responses to target stimuli. Reliable between-task differences in source localization were obtained for the P3m component, but not for the other components. Inferior-medial sources were found for the P3m evoked by both spatial and object targets, with these sources being located about 3.5 cm more anterior for object targets. These results suggest that different neuronal sources, possibly located in subcortical regions in the vicinity of the thalamus, contribute to the P3m evoked by target stimuli defined by either object or spatial stimulus characteristics.

Syntactic parsing as revealed by brain responses: first-pass and second-pass parsing processes

This paper reviews a series of electrophysiological experiments on syntactic processing against the background of a psycholinguistic two-stage model of parsing. The data reveal two event-related brain potential components in correlation with syntactic processes: an early left anterior negativity and a late centro-parietal positivity. It is argued that these two components can be correlated with two separate stages of syntactic processing: the early left anterior negativity reflecting first-pass parsing processes and the late positivity reflecting second-pass parsing processes possibly including processes of reanalyses.

Human brain potentials of spatial location encoding into memory

Event-related potentials (ERP) were elicited by little vertical bars located randomly in 1 of 4 positions (top, bottom, left or right) relative to a central fixation point. There were 4 experimental conditions requiring the subjects either to press a button if the stimulus was in the target location, count the number of stimuli appearing in the target location, look at the stimuli passively or memorize the location of the stimulus. The interstimulus interval was 2 sec for all tasks. In the memory condition subjects had to consider stimuli as pairs, memorize the location of the first stimulus of every pair and press a button if the second stimulus was in the same location. Our results indicate that ERPs corresponding to the memorization and retention of spatial location are different from those of the other 3 tasks in the presence of a long duration negativity mainly distributed bilaterally over O1, O2, T5 and T6 electrodes. This negativity seems to develop gradually several milliseconds before stimulus onset, reaches its highest value when the spatial location is assumed to be analyzed, and continues with uniform scalp distribution until the end of the recording (822 msec after stimulus onset).

Event-related brain potentials during natural speech processing: effects of semantic, morphological and syntactic violations

The present study investigated different aspects of auditory language comprehension. The sentences which were presented as connected speech were either correct or incorrect including a semantic error (selectional restriction), a morphological error (verb inflection), or a syntactic error (phrase structure). After each sentence, a probe word was presented auditorily, and subjects had to decide whether this word was part of the preceding sentence or not. Event-related brain potentials (ERPs) were recorded from 7 scalp electrodes. The ERPs evoked by incorrect sentences differed significantly from the correct ones as a function of error type. Semantic anomalies evoked a 'classical' N400 pattern. Morphological errors elicited a pronounced negativity between 300 and 600 ms followed by a late positivity. Syntactic errors, in contrast, evoked an early negativity peaking around 180 ms followed by a negativity around 400 ms. The early negativity was only significant over the left anterior electrode. The present data demonstrate that linguistic errors of different categories evoke different ERP patterns. They indicate that with using connected speech as input, different aspects of language comprehension processes cannot only be described with respect to their temporal structure, but eventually also with respect to possible brain systems subserving these processes.

Time effects on event-related brain potentials and vigilance performance

A review of the literature showed that in vigilance or oddball tasks, changes over time in event-related potentials (ERPs) and performance measures often seem to be unrelated, but a number of studies had some shortcomings. In the present study a visual vigilance experiment was carried out, in which single-trial ERPs and performance data of 40 males were obtained. A relationship between time trends in behavioral and ERP measures was found: an early P3 amplitude and response latency (RT) showed an inversely varying relation over time. Analysis of covariance showed that the two linear trends tap the same aspect of processing: both trends became insignificant when adjusted for common variance. A negative correlation between mean values of P3 amplitude and RT rather than for change scores has been observed in previous studies, but has been ignored in the literature. However, correlations with RT have also been reported for other ERP deflections. Although there were several correlations between mean scores, most time-induced changes in ERP parameters appeared to be unrelated to worsening performance, for which several explanations are advanced. The ERP results do not support the hypothesis that a decrement in performance is caused by increasing difficulty discriminating targets from nontargets. A gradual decline in effort or resources allocated to the task might be an alternative explanation of performance deterioration. However, an effort-hypothesis cannot easily be tested. Effort is often invoked post hoc, and has previously been associated with many ERP components. The relationship between ERPs and the signal detection measures "sensitivity" d' and "response bias" beta is discussed.

Effects of isolated and combined exposures to whole-body vibration and noise on auditory-event related brain potentials and psychophysical assessment

Auditory event-related brain potentials (ERP) in response to two different tone stimuli (1.1 kHz or 1 kHz, 80 dB, 50 ms; given by headphones at a regular interstimulus interval of 5 s with a probability distribution of 70:30) were recorded from 12 healthy male subjects (Ss) during four different conditions with two repetitions: A-60 dBA white noise (wN), no whole-body vibration (WBV); B-60 dBA wN plus sinusoidal WBV in the az-direction with a frequency of 2.01 Hz and acceleration of 2 m.s-2 root mean square; C-80 dBA wN, no WBV; D-80 dBA wN plus WBV. Each condition consisted of two runs of about 11 min interrupted by a break of 4 min. During the break with continuing exposure, but without auditory stimuli, Ss judged the difficulty of the tone-detection task and intensity of noise by means of cross-modality matching (CMM). Vibration-synchronous activity in the electrocardiogram was eliminated by a subtraction-technique. Noise caused an attenuation of the N1 and P2 amplitudes and prolongation of P3 latencies. The WBV did not cause systematic ERP effects. Condition B was associated with higher N1 and smaller P3 amplitudes. The factor "condition" had a significant effect on the peak latencies of P3 to target stimuli and the task difficulty judged by CMM. Both effects exhibited significant linear increases in the sequence of conditions A, B, C, D. For the evaluation of exposure conditions at work, it can be suggested that noise has a strong systematic effect which can be enhanced by WBV.(ABSTRACT TRUNCATED AT 250 WORDS)

Passive listening and task related P300 measurement for the evaluation of dementia and pseudodementia

The late evoked potential P300 was tested in three groups of subjects. These consisted of 25 patients suffering from dementia (Group I), 14 patients suffering from pseudodementia due to severe depressive disease (Group II), and 24 age-matched normal controls (Group III). Since patients suffering from dementia frequently have difficulties in counting targets in the "oddball" paradigm, we evaluated the usefulness of a Passive Listening condition. With the classical "oddball" paradigm, 78% of the subjects were correctly related to one of the three groups examined. The "P300-like" wave form produced in the Passive Listening condition was not found to be sensitive enough to allow such a distinction.

Event-related brain potentials as indices of information extraction and response priming

Measures of overt response and of the event-related brain potential (ERP) were used to investigate the processing of a priming stimulus varying in its information content. Subjects were shown sequences of 2 letters that served as a priming and an imperative stimulus. In 3 randomly interspersed conditions the imperative stimulus had a 0.80, 0.50, or 0.20 probability of physically matching the priming letter. The different probability conditions were signaled by the position of a dot flanking the priming letter. Reaction time and accuracy data indicated that the subjects primed their responses as a function of the information conveyed by the priming stimulus. The amplitude and latency of the P300 to the priming stimulus were sensitive to the amount of information conveyed by the priming stimulus and the duration of the processing required. The readiness potential in the foreperiod was lateralized as a function of the priming stimulus. Furthermore, the larger the amplitude of the P300 to the priming stimulus, the larger the lateralization of the readiness potential, indicating that information extraction, indexed by the P300, was related to response priming, indexed by the readiness potential. The results indicate that ERP measures make manifest covert aspects of the priming process occurring in the foreperiod.

Effects of stimulus repetition, duration, and rise time on startle blink and automatically elicited P300

Intense auditory stimuli of sudden onset evoke not only startle blinks but also an event-related potential component resembling classic P300, even when subjects have no assigned task. To more closely examine the relationship of this P300 to startle, event-related potentials and eyeblink were recorded from 16 young adults in three paradigms designed to produce wide variation in startle amplitude: an Habituation series of 30-ms, 105dBA white noise bursts, a Duration paradigm which presented 105dB noise bursts for 3, 10, 30, or 90 ms, and a Rise Time paradigm which varied the rise/fall times (3, 15, 30, and 45 ms) of 110dBA, 1000-Hz tone bursts. Subjects received two runs of each paradigm. Only on the final Duration and Rise Time runs were stimuli explicitly task relevant; on those runs subjects rated verbally, midway in each 8.4-s interstimulus interval, the disturbingness of the prior sound. Although even the briefest noise bursts evoked parietal P300 as well as startle blink, P300 did not behave like startle. P300 habituated more slowly than did blink amplitude, was more responsive to sustained noise than were blink, N110, and P190, and most importantly, did not show the sensitivity to stimulus rise time manifested by these measures. These findings suggest that the amplitude of automatically elicited P300 is not governed by the same mechanisms as startle amplitude, but behaves more like a defense response.

Effects of mnemonic strategy manipulation in a Von Restorff paradigm

Subjects were instructed to use either rote or elaborative strategies to memorize words in a Von Restorff paradigm. When instructed to use rote strategies, subjects displayed a higher Von Restorff effect and a lower recall performance than when instructed to use elaborative strategies. Furthermore the amplitude of the P300 component of the event-related brain potential predicted subsequent recall only when subjects used rote strategies. When subjects used elaborative strategies, the relationship between P300 amplitude and subsequent recall was not observed. These results confirm and expand, in a within-subjects design, the results reported by Karis, Fabiani and Donchin (1984) who capitalized on different strategies used by different subjects. These results also lend support to a 3-phase model of the von Restorff effect.

A parieto-occipital generator for P300: evidence from human intracranial recordings

Auditory event-related potentials (ERPs) were recorded simultaneously from the scalp and from bilateral intracranial sites within the frontal and temporal lobes, as well as from intracortical sites in the parieto-occipital region in a subject undergoing evaluation for surgical treatment of medically intractable epilepsy. Scalp ERP morphology was entirely normal. Large amplitude ERPs could be recorded from all intracranial sites. Furthermore, polarity inversions of ERP components with latencies similar to that of the scalp P300 were recorded in both temporal lobes and from the parieto-occipital region. These findings are consistent with suggestions that multiple intracranial generators, including extratemporal ones, give rise to the scalp-recorded P300. These data also provide a basis for a conceptual link between hypotheses concerning the neural substrate of attention and the psychological correlates of the P300.