Habituation of P300 in the Use of P300-based Brain-Computer Interface Spellers: Individuals With Amyotrophic Lateral Sclerosis Versus Age-Matched Controls.

The P300-based brain-computer interface speller can provide motor independent communication to individuals with amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disorder that affects the motor system. P300 amplitude stability is critical for operation of the P300 speller. The P300 has good long-term stability, but to our knowledge, short-term habituation in the P300 speller has not been studied. In the current study, 15 participants: 8 ALS patients and 7 age-matched healthy volunteers (HVs), used 2 versions of P300 spellers, Face speller and Flash speller, each for 30 minutes. The ALS group performed as well as the HVs in both spellers and HVs did better with the Face speller than Flash speller while the ALS group performed equally well in both spellers. Neither intra-run P300 habituation nor inter-run P300 habituation was found. The P300 speller could be a reliable communication device for individuals with ALS.

Seeking neurophysiological manifestations of speech production: An ERP study.

The aim of this study was to examine the neurophysiological correlates of speech production by elucidating pertinent ERP components. Such examination can pave way for investigations on typical and atypical speech neuromotor control. Participants completed a speech task by saying a specific word (speaking condition) or withholding the verbal response (non-speaking condition) based on the color of a frame placed around a fixation cross that were displayed on a computer screen. They also completed a simple hand motor task by pressing a button with the right or left index finger based on the color of a frame. The hand motor task was administered to verify that neural activity specific to motor preparation was detectable. Two ERP components emerged from the multichannel principal component analysis (PCA) as distinguishing between the speaking and no speaking conditions: a posterior negative component, and a left lateralized positive component. The morphology of the posterior negative component, as well as the correlation between its magnitude and mean response time suggest that this component is closely associated with speech motor control. The left-lateralized component was interpreted as reflecting a process possibly mediated by the speech dominant left hemisphere.

The Error-Related Negativity.

We look back on the events surrounding the genesis of our 1993 article on the error-related negativity (ERN), a component of the event-related brain potential that accompanies errors in the performance of speeded-response tasks. Our reminiscences focus on the personal friendships, intellectual influences, and chance occurrences that shaped the article. To put our work in historical context, we consider subsequent trends in neuroimaging, computational modeling, and psychiatry that gave the ERN high visibility and contributed to the longevity of its scientific interest.

Developmental changes in the feedback related negativity from 8 to 14 years.

The study examined age related changes in the magnitude of the Feedback Related Negativity (FRN) in 8-14 year old children performing a variation of a Go/No-Go task. Participants were presented with four stimuli and tasked with mapping each of them either to a response or to a "no response" by trial and error guided by feedback. Feedback was valid for two stimuli (Go and No-Go) and invalid (.5 positive; .5 negative feedback) for the other two stimuli. The amplitude of the FRN was evaluated as a function of age separately for Go and No-Go trials. The results indicated that while performance on valid Go trials improved with age, accuracy on valid No-Go trials remained stable with age. FRN amplitude was found to be inversely related to age such that smaller FRN amplitudes were observed in older children even after controlling for variance in learning. Additionally, the FRN was found as a predictor of post-learning performance on Go trials but not on No-Go trials, regardless of age. These results do not provide support to the link between the FRN and inhibition control as measured by No-Go performance, but do suggest a link with other executive control abilities called for by the Go condition.

On the roles of distinctiveness and semantic expectancies in episodic encoding of emotional words.

We examined the factors that contribute to enhanced recall for emotionally arousing words by analyzing behavioral performance, the P300 as an index of distinctiveness, and the N400 as an index of semantic expectancy violation in a modified Von Restorff paradigm. While their EEG was recorded, participants studied three list types (1) neutral words including one emotionally arousing isolate (either positive or negative), (2) arousing, negative words including one neutral isolate, or (3) arousing, positive words including one neutral isolate. Immediately after each list, free recall was tested. Negative, but not positive, words exhibited enhanced recall when presented as isolates in lists of neutral words and elicited a larger P300 for subsequently recalled than not-recalled words. This suggests that arousing, negative words stand out and that their distinctiveness contributes to their superior recall. Positive valence had an enhancing effect on recall only when the list contained mostly other positive words. Neutral isolates placed in either positive or negative lists elicited an N400, suggesting that semantic expectations developed in emotional word lists regardless of valence. However, semantic relatedness appeared to more strongly contribute to recall for positive than negative words. Our results suggest that distinctiveness and semantic relatedness contribute to episodic encoding of arousing words, but the impact of each factor depends on both a word's valence and its context.

Resampling (bootstrapping) the mean: A definite do.

There has been discussion lately about whether bootstrap versus permutations methods are the more appropriate in diagnostic psychophysiology, especially in the context of concealed information tests (CITs), also called guilty knowledge tests (GKTs). We review the use of bootstrapping in most published CIT/GKT studies (where means, or correlations, as opposed to peak amplitudes are estimated) and find them valid and reliable. When bootstrapping and permutations were applied to the same synthesized ERP datasets, they agreed 98.1% of the time, averaged over 24,000 iterations.

ERP and pupil responses to deviance in an oddball paradigm.

We investigated the relationship between, and functional significance of, P300, novelty P3, and the pupil dilation response (PDR). Subjects categorized stimuli including (a) words of a frequent category, (b) words of an infrequent category (14%), and (c) pictures of the frequent category ("novels"; 14%). The P300 and novelty P3 were uncorrelated with the PDR and differed in their response to experimental manipulation. Therefore, although the three physiological responses often co-occur, they appear to each manifest a distinct function: The PDR may be more closely linked to aspects of behavioral responding than the event-related potentials. Within participants, P300 and PDR latencies accounted for unique portions of the reaction time variance, and amplitudes of all three responses were larger for stimuli recalled on a subsequent test, compared to not recalled. We discuss the possibility that all three responses reflect norepinephric input from the locus coeruleus.

Error and performance feedback processing by children with Specific Language Impairment--an ERP study.

The study evaluates error and feedback related processing in children with Specific Language Impairment (SLI), and in age and gender matched controls. Participants performed two tasks which varied in the extent to which feedback was provided following each response. Although no group differences were found in accuracy and response time measures, children with SLI corrected a smaller proportion of their errors in comparison with the control group. Neurophysiological data pointed to error and feedback processing differences between the two groups. Errors committed by the control group elicited error-related ERP components (ERN, Pe), while these components were attenuated in the SLI group. A posterior positivity was elicited in association with incorrect responses in both groups. When a feedback stimulus informed the participants about the accuracy of the response, the feedback, rather than the response, elicited an ERN in the control group, while no ERN was elicited in the SLI group. These results suggest that children with SLI have an impaired ability to self-monitor performance and to take advantage of performance feedback.

On the utility of positive and negative feedback in a paired-associate learning task.

This study offers a neurophysiological examination of the relationship between feedback processing and learning. A two-choice paired-associate learning task borrowed and modified from Tricomi and Fiez [Tricomi, E., & Fiez, J. A. Feedback signals in the caudate reflect goal achievement on a declarative memory task. Neuroimage, 41, 1154-1167, 2008] was employed to examine the mediofrontal electrophysiological brain activity associated with the processing of performance feedback in a learning task and to elucidate the extent to which the processing of the initial informative feedback is related to learning outcomes. Twenty participants were tasked with learning to correctly pair 60 novel objects with their names by choosing on a trial-by-trial basis between two possible names and receiving feedback about the accuracy of their selection. The novel objects were presented in three blocks of trials (rounds), each of which presented the same set of 60 objects once. The rounds allowed the separation of the initial informative feedback in Round 1 from the other feedback stimuli in Rounds 2 and 3. The results indicated differences in the processing of initial informative and proceeding feedback stimuli. More specifically, the difference appeared to be driven by the change in the processing of positive feedback. Moreover, very first positive feedback provided in association with a particular new object was found associated with learning outcomes. The results imply that signs of successful and unsuccessful learning may be detected as early as the initial positive feedback provided in a learning task. The results suggest that the process giving rise to the feedback-related negativity is sensitive to the utility of the feedback and that the processing of the first informative positive feedback is associated with learning outcomes.

The component structure of event-related potentials in the p300 speller paradigm.

We investigated the componential structure of event-related potentials elicited while participants use the P300 BCI. Six healthy participants "typed" all characters in a 6 × 6 matrix twice in a random sequence. A principal component analysis indicated that in addition to the P300, target flashes elicited an earlier frontal positivity, possibly a Novelty P3. The amplitudes of both P300 and the Novelty P3 varied with the matrix row in which the target character was located. However, the P300 elicited by row flashes was largest for targets in the lower part of the matrix, whereas the Novelty P3 elicited by column flashes was largest in the top part. Classification accuracy using stepwise linear discriminant analysis mirrored the pattern in the Novelty P3 (an accuracy difference of 0.1 between rows 1 and 6). When separate classifiers were generated to rely solely on the P300 or solely on the Novelty P3, the latter function led to higher accuracy (a mean accuracy difference of about 0.2 between classifiers). A possible explanation is that some nontarget flashes elicit a P300, leading to lower selection accuracy of the respective classifier. In an additional set of data from six different participants we replicated the ERP structure of the initial analyses and characterized the spatial distributions more closely by using a dense electrode array. Overall, our findings provide new insights in the componential structure of ERPs elicited in the P300 speller paradigm and have important implications for optimizing the speller's selection accuracy.

The component structure of ERP subsequent memory effects in the Von Restorff paradigm and the word frequency effect in recall.

We examined the degree to which ERP components elicited by items that are isolated from their context, either by their font size ("size isolates") or by their frequency of usage, are correlated with subsequent immediate recall. Study lists contained (a) 15 words including a size isolate, (b) 14 high frequency (HF) words with one low frequency word ("LF isolate"), or (c) 14 LF words with one HF word. We used spatiotemporal PCA to quantify ERP components. We replicated previously reported P300 subsequent memory effects for size isolates and found additional correlations with recall in the novelty P3, a right lateralized positivity, and a left lateralized slow wave that was distinct from the slow wave correlated with recall for nonisolates. LF isolates also showed evidence of a P300 subsequent memory effect and also elicited the left lateralized subsequent memory effect, supporting a role of distinctiveness in word frequency effects in recall.

A comment on Farwell (2012): brain fingerprinting: a comprehensive tutorial review of detection of concealed information with event-related brain potentials.

In a recent issue of Cognitive Neurodynamics Farwell (Cogn Neurodyn 6:115-154, 2012) published a comprehensive tutorial review of the use of Event Related Brain Potentials (ERP) in the detection of concealed information. Farwell's review covered much of his own work employing his "brain fingerprinting" technology. All his work showed a 100 % accuracy rate in detecting concealed information. We argue in this comment that Farwell (Cogn Neurodyn 6:115-154, 2012) is misleading and misrepresents the scientific status of brain fingerprinting technology.

The good, the bad, or the useful? The examination of the relationship between the feedback-related negativity (FRN) and long-term learning outcomes.

According to the reinforcement learning account of the error-related negativity (ERN), the ERN is a manifestation of a signal generated in ACC as a consequence of a phasic decrease in the activity of the mesencephalic dopamine system occurring when the monitoring system evaluates events as worse than expected. This signal is also hypothesized to be used to modify behavior to ascertain that future events will have better outcomes. It is therefore expected that this signal be correlated with learning outcomes. We report a study designed to examine the extent to which the ERN is related to learning outcomes within a paired-associates learning task. The feedback-related negativity (FRN) elicited by stimuli that indicated to the participants whether their response was correct or not was examined both according the degree to which the associates were learned in the session and according to whether participants recalled the associations on the next day. The results of the spatio-temporal PCA indicate that, whereas the process giving rise to the negative feedback elicited a FRN whose amplitude was not correlated with long-term learning outcomes, positive feedback was associated with a FRN-like activity, which was correlated with the learning outcomes. Another ERP component that follows the FRN temporally and shares its spatial distribution was found associated with long-term learning outcomes. Our findings shed light on the functional significance of the feedback-related ERP components and are discussed within the framework of the reinforcement learning ERN hypothesis.

Efficiency of responding to unexpected information varies with sex, age, and pubertal development in early adolescence.

Entry into adolescence is marked by dramatic changes resulting from a dynamic interplay among biological and psychosocial processes. Despite the complexity, development is often indexed only by age in event-related potential (ERP) studies. To broaden this approach, we address the effects of gender and pubertal development, along with age, in adolescents using a psychophysiological probe of decision making, the P300 component. Overall, girls exhibited shorter P300 latencies and smaller P300 amplitudes compared to boys, suggesting more efficient information processing. In both genders, P300 latency and amplitude also diminished as age and pubertal status increased, again suggesting increasing efficiency of information processing with development. Our findings highlight the necessity of considering more than age when examining cognitive functioning in adolescents and, in particular, the necessity of considering gender whenever developmental issues are addressed.

How large the sin? A study of the event related potentials elicited by errors of varying magnitude.

We report the results of an experiment designed to elucidate the extent to which the error related ERP components are affected by response and stimulus similarity. We examined the ERPs under varying degrees of mismatch between the representations of actual and appropriate responses. We replicated the design used in an earlier study, which demonstrated that response similarity rather than stimulus similarity affected the amplitude of the error related negativity (ERN). We report the results of a spatial-temporal principal component analysis (PCA), which indicates that response similarity affects the amplitudes of the ERN and the fronto-central positive component, but not those of the P300 and the frontal negativity. The results provide evidence to suggest that the ERN and the proceeding positive deflection are error related and are sensitive to the degree of the committed error, whereas the P300 and the frontal negativity are not.

When a child errs: the ERN and the Pe complex in children.

We report an analysis of the componential structure of the event-related potentials (ERPs) elicited when 8-10-year-old children err. We demonstrated previously that the positive deflection that follows the error-related negativity (ERN) in young adults is a combination of two ERP components, a fronto-central positive component and a P300. As these findings affect the interpretation of error-related ERP data, it is essential to determine if the componential structure of the ERPs elicited by children's errors is similar to that found in young adults. The results of the current study confirm that, as is the case in adults, both an ERN and a fronto-central positivity are elicited by errors committed by children. In contrast to what has been previously found in adults, errors committed by children elicited a central positivity in addition to a parietal negativity that was elicited by correct responses.

Neural response to action and reward prediction errors: Comparing the error-related negativity to behavioral errors and the feedback-related negativity to reward prediction violations.

The error-related negativity (ERN) is thought to index an anterior cingulate (ACC) behavioral monitoring system. The feedback ERN (FRN) is elicited to error feedback when the correct response is not known, but also when a choice outcome is suboptimal and to passive reward prediction violation, suggesting that the monitoring system may not be restricted to actions. This study used principal components analysis to show that the ERN consists of a single central component whereas the reward prediction violation FRN is comprised of central and prefrontal components. A prefrontal component is also present in action monitoring but occurs later, at the error positivity latency. This suggests that ACC monitors both actions and events for reward prediction error. Prefrontal cortex may update reward expectation based on the prediction violation with the latency difference due to differential processing time for motor and perceptual information.

The N400 and the P300 are not all that independent.

This study assessed whether two ERP components that are elicited by unexpected events interact. The conditions that are known to elicit the N400 and the P300 ERP components were applied separately and in combination to terminal-words in sentences. Each sentence ended with a terminal-word that was highly expected, semantically unexpected, physically deviant, or both semantically unexpected and physically deviant. In addition, we varied the level of semantic relatedness between the unexpected terminal-words and the expected exemplars. Physically deviant words elicited a P300, whereas semantically unexpected words elicited an N400, whose amplitude was sensitive to the level of semantic relatedness. Words that were both semantically unexpected and physically deviant elicited both an N400 with enhanced amplitude, and a P300 with reduced amplitude. These results suggest an interaction between the processes manifested by the two components.

Single trial independent component analysis for P300 BCI system.

A Brain Computer Interface (BCI) is a device that allows the user to communicate with the world without utilizing voluntary muscle activity (i.e., using only the electrical activity of the brain). It makes use of the well-studied observation that the brain reacts differently to different stimuli, as a function of the level of attention allotted to the stimulus stream and the specific processing triggered by the stimulus. In this article we present a single trial independent component analysis (ICA) method that is working with a BCI system proposed by Farwell and Donchin. It can dramatically reduce the signal processing time and improve the data communicating rate. This ICA method achieved 76.67% accuracy on single trial P300 response identification.

Parsing the componential structure of post-error ERPs: a principal component analysis of ERPs following errors.

We report the results of two experiments designed to clarify the spatial and temporal characteristics of the positive deflection that follows the error related negativity (ERN) elicited to incorrect responses in speeded reaction time tasks. Principal components analysis (PCA) indicates that the positive deflection reported to follow the ERN is composed of two different components: (a) a fronto-central positive deflection that follows the ERN and shares its spatial distribution and (b) a P300. When accuracy was required of the participants, the ERN and the P300 were larger in amplitude than when speed and accuracy were equally weighted. On the other hand, the amplitude of the fronto-central positive component was not affected by the degree to which accuracy was stressed.