Human Event-related Potential Research Articles

Functionally Independent Components of the Late Positive Event-Related Potential during Visual Spatial Attention

Human event-related potentials (ERPs) were recorded from 10 subjects presented with visual target and nontarget stimuli at five screen locations and responding to targets presented at one of the locations. The late positive response complexes of 25-75 ERP average waveforms from the two task conditions were simultaneously analyzed with Independent Component Analysis, a new computational method for blindly separating linearly mixed signals. Three spatially fixed, temporally independent, behaviorally relevant, and physiologically plausible components were identified without reference to peaks in single-channel waveforms. A novel frontoparietal component (P3f) began at approximately 140 msec and peaked, in faster responders, at the onset of the motor command. The scalp distribution of P3f appeared consistent with brain regions activated during spatial orienting in functional imaging experiments. A longer-latency large component (P3b), positive over parietal cortex, was followed by a postmotor potential (Pmp) component that peaked 200 msec after the button press and reversed polarity near the central sulcus. A fourth component associated with a left frontocentral nontarget positivity (Pnt) was evoked primarily by target-like distractors presented in the attended location. When no distractors were presented, responses of five faster-responding subjects contained largest P3f and smallest Pmp components; when distractors were included, a Pmp component appeared only in responses of the five slower-responding subjects. Direct relationships between component amplitudes, latencies, and behavioral responses, plus similarities between component scalp distributions and regional activations reported in functional brain imaging experiments suggest that P3f, Pmp, and Pnt measure the time course and strength of functionally distinct brain processes.

Attentional orienting and reorienting is indicated by human event-related brain potentials.

We investigated event-related potential indications for the orienting towards task-irrelevant, distracting aspects of stimulation and for the subsequent reorienting towards task-related aspects of stimulation. An identical experimental protocol was run in three conditions manipulating the task relevance of the sounds. As to be expected, distractors elicited the MMN (reflecting the brain's pre-attentive change detection) in each condition (even when the sounds were ignored) and subsequent N2b and P3 (reflecting orienting towards the distractor) when the sounds were attended. A late negativity was confined to a condition in which subjects discriminating long from short sounds were distracted by task-irrelevant frequency deviations. The 'reorienting negativity' (RON) probably reflects processes in the context of reorienting towards task-relevant aspects of stimulation following distraction.

Topographic study of human event-related potentials using a task requiring mental rotation

Event-related potentials (ERPs) were recorded during a mental rotation task that required subjects to determine whether two stimuli presented in turn had the same shape regardless of any difference in orientation. This task consisted of two conditions: the control condition, when the two stimuli presented were identical, requiring only recognition, and the experimental condition that required recognition following mental rotation. We hypothesized that differences between ERPs recorded during the control and experimental conditions were neurophysiologically correlated with mental rotation. In the experimental condition, a marked negative component arose about 430 ms after the second stimulus. The statistically significant difference between the negative components of the two conditions was maximal over the right frontocentral region, suggesting that mental rotation processing is a right hemisphere dominant function.

Automatic change detection: Does the auditory system use representations of individual stimulus features or gestalts?

The effects of global and feature-specific probabilities of auditory stimuli were manipulated to determine their effects on the mismatch negativity (MMN) of the human event-related potential. The question of interest was whether the automatic comparison of stimuli indexed by the MMN was performed on representations of individual stimulus features or on gestalt representations of their combined attributes. The design of the study was such that both feature and gestalt representations could have been available to the comparator mechanism generating the MMN. The data were consistent with the interpretation that the MMN was generated following an analysis of stimulus features.

Automatic change detection: Does the auditory system use representations of individual stimulus features or gestalts?

The effects of global and feature-specific probabilities of auditory stimuli were manipulated to determine their effects on the mismatch negativity (MMN) of the human event-related potential. The question of interest was whether the automatic comparison of stimuli indexed by the MMN was performed on representations of individual stimulus features or on gestalt representations of their combined attributes. The design of the study was such that both feature and gestalt representations could have been available to the comparator mechanism generating the MMN. The data were consistent with the interpretation that the MMN was generated following an analysis of stimulus features.

Serotonergic modulation of the P300 event related brain potential

While dopaminergic, noradrenergic, cholinergic and gabaergic effects on the P300 component of the human event-related brain potential have been largely described, little is known about serotonergic influence. Therefore, we investigated the relationship between P300 and serotonergic activity as reflected by prolactin (PRL) response to flesinoxan, a 5-HT1A full agonist, among 28 normal subjects. Results showed a significant negative correlation between P300 amplitude and PRL response to flesinoxan (r=−0·47, p=0·01 at Cz; r=−0·45, p=0·01 at Pz). In contrast, both P300 latency and reaction time were not related to endocrine response. This study supports a role for serotonin in the neurobiological modulation of P300 amplitude. Clinical implications of these results are considered. © 1998 John Wiley & Sons, Ltd.

Quantitative trait loci analysis of human event-related brain potentials: P3 voltage

The P3 event-related brain potential (ERP) is a positive-going voltage change of scalp-recorded electroencephalographic activity that occurs between 300–500 ms after stimulus onset. It is elicited when a stimulus is perceived, memory operations are engaged, and attentional resources are allocated toward its processing. Because this ERP component reflects fundamental cognitive processing, it has found wide utility as an assessment of human mental function in basic and clinical studies. In particular, P3 attributes are heritable and have demonstrated considerable promise as a means to identify individuals at genetic risk for alcoholism. We have conducted a quantitative linkage analysis on a large sample from families with a high density of affected individuals. The analyses suggest that several regions of the human genome contain genetic loci related to the generation of the P3 component of the ERP, which are possible candidate loci underlying the functional organization of human neuroelectric activity.

Human event-related brain potentials to auditory periodic noise stimuli

Periodic noise is perceived as different from ordinary non-repeating noise due to the involvement of echoic memory. Since this stimulus does not contain simple physical cues (such as onsets or spectral shape) that might obscure sensory memory interpretations, it is a valuable tool to study sensory memory functions. We demonstrated for the first time that the processing of periodic noise can be tapped by event-related brain potentials (ERPs). Human subjects received repeating segments of noise embedded in non-repeating noise. They were instructed to detect the periodicity inherent to the stimulation. We observed a central negativity time-locked on the periodic segment that correlated to the subjects behavioral performance in periodicity detection. It is argued that the ERP result indicates an enhancement of sensory-specific processing.

Event-related potential indices of semantic priming following an unrelated intervening item

Interposing an unrelated word between related primes and targets often disrupts priming. This finding has been used to support the view that semantic information is represented in a distributed fashion, rather than locally. In some studies where unrelated items intervened between the prime and target, however, significant priming was nevertheless obtained. The discrepant results of these studies has been attributed to differences in speed-accuracy tradeoff, post-lexical checking, conscious rehearsal of the prime and differences in the depth to which the prime and target were processed. The present study was designed in such a way as to minimize variability associated with post-lexical influences. The N400 component of the human event-related potential was used as a physiological index of the extent to which priming occurred with and without the interposition of an unrelated item. Priming effects on both the amplitude and latency of the N400 were rendered non-significant by the presence of an intervening unrelated word. The results are interpreted as tentative evidence that semantic representations are distributed.

A high resolution EEG method based on the correction of the surface Laplacian estimate for the subject's variable scalp thickness

To improve the spatial resolution of human event-related potentials, we developed a new high resolution EEG method based on the improved estimate of the realistic surface Laplacian (SL). The novelty of this method consisted in the computation of the local scalp resistance that was assumed to be inversely proportional to the local scalp thickness measured from magnetic resonance images of the subject's head. The local scalp thickness was then multiplied by the SL estimate of the potential over a realistic magnetic resonance-constructed model of the subject's scalp surface. The new method was applied on human movement-related and somatosensory-evoked potentials, the SL estimate at a constant scalp thickness being used as a reference. The locally-predicted scalp thickness was significantly ( P < 0.05) higher in the temporal areas (9.5 ± 2.6 mm) than in the parieto-occipital (6.6 ± 1.3 mm) and frontal (4.8 ± 1.1 mm) areas. Compared to the SL estimate at constant scalp thickness, the improved SL estimate enhanced the spatial detail of both movement-related and somatosensory-evoked potentials.

Adequate scalp sampling density for the human visual event-related potential

Adequate scalp sampling density for the human visual event-related potential

Clonidine-induced antagonism of norepinephrine modulates the attentional processes involved in peak-interval timing.

Duke University The effects of the a2-agonist clonidine and the a2-antagonist idazoxan were studied with emphasis on the attentional mechanisms subserving interval-timing behavior. Administration of clonidine (0.015 mg/kg IP) to rats trained on a 20-s peak-interval (PI) timing procedure caused a rightward shift in peak functions, whereas idazoxan (0.15 mg/kg IP) caused a leftward shift. Rats were also trained on 10-s and 30-s baseline PI timing procedures in combination with the prior-entry and prior-entry reversal versions of this task that produced leftward shifts and rightward shifts relative to baseline training, respectively. Clonidine (0.025 mg/kg IP) produced a rightward shift in peak functions for all of these behavioral procedures. Taken together, these horizontal shifts in the peak functions indicate a decrease (leftward shift) or an increase (rightward shift) in the latency to start the internal clock that is influenced both by the attentional demands of the task and the effective level of brain norepinephrine. Cognitive accounts of information processing divide atten- tion into three major functions: orienting to sensory events, detecting signals for conscious processing, and maintaining an alert state (Posner & Petersen, 1990). The allocation of attention for the detection of signals for conscious processing may result in the subject attending to the expected spatial location, temporal location, or sensory modality of the signal. As a consequence, if the signal is either in an unexpected location or of an unexpected modality, it will not be processed as rapidly. In contrast, if attention is allocated to maintaining a general state of alertness or arousal, then any signal that is of sufficient intensity will engage conscious processing. An information-processing model of interval timing suggests Trevor B. Penney, Department of Psychology, Columbia University; Mark D. Holder, Department of Psychology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada and Department of Psychology, Okanagan University College, Kelowna, British Columbia, Canada; Warren H. Meck, Department of Psychology: Experimental, Duke University. This research was supported in part by a grant from the Natural Sciences and Engineering Research Council of Canada (A1221). Preliminary reports based on this work were presented at the 64th Annual Meeting of the Eastern Psychological Association, Arlington, Virginia (Penney, Holder, M Meck, 1984). Data from human event-related potential (ERP) para- digms (e.g., Gratton et al., 1990) and animal timing tasks (Meck, 1984) suggest that warning signals serve to prime perceptual processing. Consequently, the use of warning signals can be used to influence a subject's expectation of thc stimulus properties (e.g., modality) of a forthcoming signal presentation. Central nervous system norepinephrine (NE) may accentu- ate activity of neurons that are transmitting the presence of significant stimuli and inhibit the activity of other neurons (Kety, 1970). This could be interpreted as an improvement in the signal-to-noise ratio or an enhancement of sclectivc attention. The selective attention hypothesis was initially based on the behavioral results of lesions to the dorsal noradrenergic bundle (DNAB; e.g., Mason, 1980; Robbins, Everitt, Cole, Archer, & Mohammed, 1985). This pathway originates in the pontine nucleus of the locus coeruleus (LC) and provides innervation to the spinal cord, cerebellum, and many forebrain areas including the caudate-putamen (Mason, 1980). The LC may act as an important gating mechanism for 82

The P300 to novel and target events

It has been reported that frontal lobe structures are critical for the generation of P300 activity in the human event-related potential (ERP) evoked by novel events. In this study spatial-temporal dipole model analyses were employed to obtain further evidence on the temporal dynamics and the approximate location of neuronal activity involved in P300 generation for target and novel events. A triple dipole configuration was found to describe the scalp recorded P300 activity for novel and target events with less than 2.5% residual variance. For the novel, but not the target dipole configuration a frontally oriented dipole was obtained whose temporal activity function suggests that the brain areas involved in the processing of novel events are engaged about 70 ms earlier than those relevant for target processing.

The P300 to novel and target events: a spatio–temporal dipole model analysis

It has been reported that frontal lobe structures are critical for the generation of P300 activity in the human event-related potential (ERP) evoked by novel events. In this study spatial–temporal dipole model analyses were employed to obtain further evidence on the temporal dynamics and the approximate location of neuronal activity involved in P300 generation for target and novel events. A triple dipole configuration was found to describe the scalp recorded P300 activity for novel and target events with less than 2.5% residual variance. For the novel, but not the target dipole configuration a frontally oriented dipole was obtained whose temporal activity function suggests that the brain areas involved in the processing of novel events are engaged about 70 ms earlier than those relevant for target processing.

Multivariate composite estimators: new ways to track signals with application to human cerebral potentials.

In this paper, we propose new multivariate composite estimators (MCE) to track multiple channel potential waves of individual and grand averages of recorded potentials at the scalp from a number of trials in a group of subjects. The advantages of these estimators over simple averages used in the literature are that they have larger signal to noise ratios (SNR), and that they have taken into account variations and correlations of the recorded potentials at the electrode sites as well as differences among subjects. Multivariate techniques and composite concept are used for deriving the estimators. We also provide an application to human event-related potentials in a memory for faces experiment.

Surface energy, its density and distance: new measures with application to human cerebral potentials.

In this paper, we propose three new measures for topographic studies of event related potentials (ERP) called the surface energy (SE), its density (SED) and the distance of surface energy density fields (DSED) based on the entire scalp current density (SCD) field. These measures have a specific physical meaning, are free of the reference electrode and any physical conductive model of the head. They capture not only spatial properties, but also continuous time elements present and smeared in the original scalp potential records. They provide a common base for comparisons of recorded potentials among different time points, subjects, regions on the scalp, or experimental conditions. We also construct a statistical inference based on these new measures, and provide an application to human event-related potentials in a visual short-term memory experiment.

A Neural System for Error Detection and Compensation

Humans can monitor actions and compensate for errors. Analysis of the human event-related brain potentials (ERPs) accompanying errors provides evidence for a neural process whose activity is specifically associated with monitoring and compensating for erroneous behavior. This error-related activity is enhanced when subjects strive for accurate performance but is diminished when response speed is emphasized at the expense of accuracy. The activity is also related to attempts to compensate for the erroneous behavior.

Unsupervized clustering by waveform of evoked potentials in a memory-scanning task

We investigated the potential effects of 20 min irradiation from a new generation Universal Mobile Telecommunication System (UMTS) 3G mobile phone on human event related potentials (ERPs) in an auditory oddball paradigm. In a double-blind task design, subjects were exposed to either genuine or sham irradiation in two separate sessions. Before and after irradiation subjects were presented with a random series of 50 ms tone burst (frequent standards: 1 kHz, P=0.8, rare deviants: 1.5 kHz, P=0.2) at a mean repetition rate of 1500 ms while electroencephalogram (EEG) was recorded. The subjects' task was to silently count the appearance of targets. The amplitude and latency of the N100, N200, P200 and P300 components for targets and standards were analyzed in 29 subjects. We found no significant effects of electromagnetic field (EMF) irradiation on the amplitude and latency of the above ERP components. In order to study possible effects of EMF on attentional processes, we applied a wavelet-based time-frequency method to analyze the early gamma component of brain responses to auditory stimuli. We found that the early evoked gamma activity was insensitive to UMTS RF exposition. Our results support the notion, that a single 20 min irradiation from new generation 3G mobile phones does not induce measurable changes in latency or amplitude of ERP components or in oscillatory gamma-band activity in an auditory oddball paradigm.

The P300 wave of the human event-related potential.

The P300 wave is a positive deflection in the human event-related potential. It is most commonly elicited in an "oddball" paradigm when a subject detects an occasional "target" stimulus in a regular train of standard stimuli. The P300 wave only occurs if the subject is actively engaged in the task of detecting the targets. Its amplitude varies with the improbability of the targets. Its latency varies with the difficulty of discriminating the target stimulus from the standard stimuli. A typical peak latency when a young adult subject makes a simple discrimination is 300 ms. In patients with decreased cognitive ability, the P300 is smaller and later than in age-matched normal subjects. The intracerebral origin of the P300 wave is not known and its role in cognition not clearly understood. The P300 may have multiple intracerebral generators, with the hippocampus and various association areas of the neocortex all contributing to the scalp-recorded potential. The P300 wave may represent the transfer of information to consciousness, a process that involves many different regions of the brain.

Event-related brain potentials and discrimination of steady-state vowels within and between phoneme categories: A preliminary study

The mismatch negativity (MMN), a component of the human auditory event-related brain potential, is elicited by a physically deviant stimulus in a sequence of homogeneo. “standard”, stimuli. MMN reflects an automatic discrimination process between the sensory input and the short-term memory trace left by the previous stimuli. These memory traces might form the neurophysiological basis of auditory sensory memory, the echoic memory. The purpose of the study was to determine whether the automatic discrimination process of vowels, as reflected in MMN, and the discrimination performance (measured as percentage of correct responses, d's, and RTs) with the same stimuli show effects of categorical perception. According to the results the study failed to show any statistically significant neurophysiological and behavioral effects of categorical perception on vowels. However, a consistent trend toward faster reaction times and better discrimination performance in phoneme boundary conditions than in phoneme center co...