Auditory and visual P300 topography from a 3 stimulus paradigm.

OBJECTIVE: The P300 event-related brain potential (ERP) was elicited with auditory and visual stimuli in a separate session of a 3 stimulus oddball paradigm, and the scalp topography was assessed with 15 electrode locations. METHODS: Target (0.10), standard (0.80), and infrequent non-target (0.10) stimuli in the auditory task were 2000, 1000 and 500 Hz tone, and in the visual task, 'X', 'O', and 'H', respectively. The stimuli were presented in a random series, once every 2 s, and participants responded only to the target (N = 12). RESULTS: Target stimuli elicited larger P300 components than non-target did in both stimulus modalities. For both target and non-target stimuli, P300 amplitude was larger and latency longer for the visual compared with the auditory stimulus. Analysis of normalized P300 amplitude data indicated that the target and non-target P300s from both modalities had identical topography. CONCLUSION: The findings suggest that both target and non-target stimuli in 3 stimulus oddball paradigm elicited the same type of P300 (P3b) for both stimulus modalities.     

Stimulus context determines whether non-target stimuli are processed as task-relevant or distractor information.

OBJECTIVE: The P300 event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (standard 0.70, target 0.15, non-target 0.15) to examine how target/standard stimulus context affects non-target processing. METHODS: Target/standard discrimination difficulty (easy or difficult) and non-target /target similarity (similar or dissimilar) were manipulated orthogonally. Participants (N=13) were instructed to respond to each infrequent target stimulus by pressing a button. RESULTS: Target stimuli in all task conditions elicited P3b, which was affected only by the difficulty of target/standard discrimination. When target/standard discrimination was easy, the amplitude of non-target P3 was larger for similar than for dissimilar non-target. In contrast, when target/standard discrimination was difficult, non-target stimuli elicited P3a, the amplitude of which was larger for dissimilar than for similar non-target. Thus, the P300 component for non-target stimuli and the pattern of the effect of target similarity on each P300 component varied as a function of the target/standard stimulus context. CONCLUSIONS: The target/standard stimulus context influences the attentional set for stimulus processing such that it determines whether non-target stimuli are processed as task-relevant or distractor information. SIGNIFICANCE: The present results are important for understanding the mechanism of cognitive modification in non-target processing.     

P300 and blink instructions.

OBJECTIVES: The effects of instructions to refrain from blinking on the P300 event-related brain potential (ERP) from auditory and visual stimuli were assessed. METHODS: An oddball paradigm was employed in which young adult subjects (n = 20) silently counted the infrequent target stimuli and were given either no instructions or told "do not blink" in different conditions, with auditory and visual stimulus tasks employed for all subjects. ERPs were recorded from the midline electrodes, with amplitude and latency of the P300 and other components obtained. RESULTS: P300 amplitude for both modalities and target/standard stimulus conditions was smaller and visual peak latency longer in the "do not blink" condition. Blink instructions did not directly affect the other components. CONCLUSIONS: Instructions to refrain from blinking can decrease P300 amplitude and can increase peak latency.     

Task difficulty, probability, and inter-stimulus interval as determinants of P300 from auditory stimuli

The P300 event-related potential was elicited with auditory stimuli in 4 experiments which manipulated combinations of stimulus target probability (10% vs. 30%), task difficulty (easy vs. hard), and inter-stimulus interval (5 sec vs. 2 sec). P300 amplitude was smaller and peak latency longer for the more difficult relative to the easier tasks across experiments. Increases in stimulus target probability generally diminished P300 amplitude and shortened peak latency more for the easy relative to difficult task conditions. Increasing the number of non-target stimulus tones decreased P300 amplitude reliably, but increased latency only slightly. Task difficulty did not interact with variations in inter-stimulus interval which produced generally weak effects for both amplitude and latency. These findings suggest that P300 amplitude and latency obtained from auditory discrimination paradigms reflect processing difficulty independently of stimulus target probability unless differences in task requirements affect stimulus encoding.     

Auditory P3a deficits in male subjects at high risk for alcoholism.

BACKGROUND: Substantial evidence indicates that alcoholism is biologically mediated by a genetic predisposition. As the decreased P300 (P3b) event-related brain potential component does not recover with prolonged abstinence, it is unlikely to be related to drinking history but is more likely to be genetically influenced. This is supported by findings that P3b amplitudes are reduced in subjects at high-risk compared to low-risk for alcoholism. Although there are few studies of P3a in HR subjects, lower P3a amplitudes have been reported with a novel nontarget stimulus paradigm, as well as with a difficult three-stimulus visual paradigm. Using a similar three-tone auditory paradigm in which the discriminability between the target and standard tone is difficult, the P3a component can also be reliably elicited with a rare nontarget perceptually distinct stimulus. This technique was employed in young adult subjects at low-risk and high-risk for alcoholism. METHODS: A total of 17 low-risk and 24 high-risk male subjects were employed as subjects in an auditory paradigm that yielded a large amplitude P3a with a centro-frontal maximum to the nontarget and a robust low amplitude prolonged P3b with a parietal maximum amplitude to the target stimulus. Current source density maps were derived to assess topographic differences between low-risk and high-risk subjects. RESULTS: The high-risk group manifested significantly lower P3a amplitudes than the low-risk group at the frontal electrodes to rare nontarget stimuli. High-risk subjects also demonstrated a more disorganized current source density map for P3a compared to low-risk subjects. CONCLUSIONS: The reduction of P3a in the high-risk group may be due to cortical dysfunction including the frontal and prefrontal cortex. The lower P3a amplitude coupled with more disorganized current source density maps suggest inefficient brain functioning in high-risk subjects.     

No decrement in visual P300 amplitude during extended performance of the oddball task

Research indicates that in visual sustained attention paradigms, the amplitude of the P300 component of the event-related potential invoked by target (critical) stimuli shows a decrement in amplitude. This amplitude decrement parallels decrements in vigilance performance that result from the difficult discrimination that is typically required between the infrequent targets and the frequent nontargets (neutral stimuli). In contrast, target stimulus P300 does not appear to show a decrement across large numbers of trials during performance of the "oddball" paradigm, in which targets and nontargets are highly discriminable. The present study measured target and nontarget P300 amplitude during performance of a visual oddball paradigm extended over an interval of some 3 1/2 hours, a period well in excess of the 3/4 hour intervals employed in previous research. The results indicated no decrement in P300 amplitude as a function of time for either targets or nontargets. The only significant relationship between P300 and behavioral data was an inverse correlation across oddball runs between average nontarget P300 amplitude and total number of targets missed.     

Effects of stimulus modality and response mode on the P300 event-related potential differentiation of young and elderly adults.

The P300 event-related brain potential (ERP) was examined in 14 young (20 - 29 years of age) and 16 elderly (60 - 82 years of age) adult subjects during the performance of auditory and visual discrimination tasks requiring silent counting or key pressing in response to target stimuli. P300 latencies were longer in elderly (vs young) adults and in visual (vs auditory) tasks, and visual tasks elicited larger P300 amplitudes than auditory tasks in both age groups. Neither stimulus modality nor response mode affected P300 differentiation of young and elderly subjects. Steeper P300 anterior-posterior scalp amplitude gradients were seen in the young (vs elderly) adults, regardless of stimulus or response type. Examination of inter-subject variability with the coefficient of variation (CV) statistic found the lowest (i.e., best) CV values to be exhibited in the visual task requiring the counting of target stimuli. Implications of the findings are discussed in relation to P300 applications in the clinical assessment of dementia and aging-associated cognitive alterations.     

Distractor P3 is associated with attentional capture by stimulus deviance.

OBJECTIVE: A simple distractor elicits a large P3 when the standard and target are difficult to discriminate in the three-stimulus oddball paradigm. This study investigated whether the distractor P3 reflects attentional capture by stimulus deviance or cognitive interference with maintaining the standard representation. METHODS: Event-related brain potentials were recorded from 12 participants who performed a visual three-stimulus oddball paradigm. Four task conditions were defined by a combination of two presentation types of distractor stimuli (central or bilateral) and two levels of standard/target discrimination difficulty (easy or difficult). Bilateral distractors had stimulus deviance but did not interfere with maintenance of the standard representation. RESULTS: Central distractors elicited a P3, the amplitude of which was larger in the difficult task than in the easy task. In contrast, bilateral distractors elicited a large P3 in both the easy and difficult tasks. CONCLUSIONS: Distractor P3 reflects attentional capture by stimulus deviance, rather than cognitive interference with maintaining the standard representation. SIGNIFICANCE: This is the first report showing that simple distractors can elicit large anteriorly distributed P3 in an easy task. The present findings contribute to the clinical application of distractor P3 to assess the cognitive function of deviant processing.     

P300 differences between sinistrals and dextrals

The P3(00) event-related potential (ERP) was elicited in 20 left- and 20 normal right-handed young adult male subjects using a simple visual stimulus discrimination task. For left-compared to right-handed subjects, P3 amplitude was larger at anterior electrode sites for the target stimuli and larger overall for the novel visual stimuli; P3 latency was shorter for left-compared to right-handers for the target stimuli. The N1, P2, and N2 components demonstrated similar handedness effects. The relationships of ERP amplitude and handedness to anatomical variables and cognitive factors are discussed.     

Reduced P300 responses in criminal psychopaths during a visual oddball task.

BACKGROUND: Clinicians have long recognized that psychopaths show deficits in cognitive function, but there have been few experimental studies exploring these deficits. We present here the first in a series of event-related potential (ERP) experiments designed to elucidate and characterize the neural correlates of cognitive processes of psychopaths. METHODS: We recorded ERPs from a topographic array from 11 psychopathic and 10 nonpsychopathic prison inmates, assessed with the Hare Psychopathy Checklist-Revised, during performance of a visual oddball task. ERPs to target (25% of trials) and nontarget (75% of trials) visual stimuli were analyzed. RESULTS: Consistent with previous research, there were no group differences in the latency or amplitude of the ERPs for the nontarget stimuli. For nonpsychopaths, the P300 amplitude was larger when elicited by the target stimuli than when elicited by the nontarget stimuli. In contrast, psychopaths failed to show reliable P300 amplitude differences between the target and nontarget conditions. Psychopaths had a smaller amplitude P300 to target stimuli than did nonpsychopaths. In addition, the amplitude of the P300 was less lateralized in psychopaths than in nonpsychopaths. Psychopaths also had a larger centrofrontal negative wave (N550) during the target condition than did nonpsychopaths. CONCLUSIONS: The results of this study indicate that there are substantial differences between psychopaths and others in the processing of even simple cognitive tasks and provide support for information processing models of psychopathy.     

P3a from a passive visual stimulus task

OBJECTIVE: Visual event-related brain potentials (ERPs) were elicited using a 3-stimulus oddball paradigm to assess the P3a with passive stimulus processing. METHODS: Young adults (n=12) were presented with a series of visual stimuli consisting of a solid circle standard stimulus (P=0.76) that was difficult to discriminate from a larger target circle (P=0.12), with a large square distractor stimulus (P=0.12) presented randomly in the series. Subjects were instructed in the passive condition to simply look at the stimuli and in the active condition to press a mouse key only to the target stimulus. ERPs were recorded from 15 scalp electrodes, with the amplitude and latency of the P300 from the distractor and target stimuli assessed. RESULTS: The P3a from the distractor stimulus was similar in amplitude, scalp topography, and peak latency across the passive and active task conditions. The P3b from the target stimulus demonstrated much smaller amplitude, highly altered scalp topography, and longer latency for the passive compared to active task conditions. CONCLUSIONS: The P3a can be obtained with visual stimuli in the 3-stimulus paradigm under passive viewing conditions. Theoretical implications and clinical applications are discussed.     

Auditory and visual P300 reflecting cognitive improvement in patients with schizophrenia with quetiapine: A pilot study

We recorded event-related potentials (ERPs) in patients with schizophrenia before and after treatment with quetiapine, to investigate this drug's effects on cognitive function. Auditory and visual oddball stimulus discrimination paradigms were presented to patients with schizophrenia (N = 20) before and after 3 months' treatment with quetiapine. The 2-stimulus auditory oddball paradigm used a standard tone (1000 Hz, 75 dB, 80%) and a target tone (2000 Hz, 75 dB, 20%). The 2-stimulus visual oddball paradigm used a standard stimulus (small circle, 80%) and a target stimulus (large circle, 20%). Patients' severity of psychopathology was initially evaluated with the Positive and Negative Syndrome Scale (PANSS) and was likewise re-evaluated after treatment. After treatment with quetiapine, patients' P300 amplitudes increased over baseline for both tasks (auditory stimuli, P < 0.01; visual stimuli, P < 0.01) and their P300 latencies for both target stimuli decreased significantly (auditory stimuli, P < 0.001; visual stimuli, P < 0.01). Visual P300 amplitude was negatively correlated with the severity of positive symptoms at the Fz electrode before the treatment (r = − 0.45, P < 0.05). After treatment with quetiapine, there were no significant correlations between severity of positive or negative symptoms and visual P300 amplitudes for midline electrodes. These findings suggest that the reduced and delayed P300 may be a state marker for schizophrenia, which may in turn be modulated by positive symptoms, and also suggest that the amplitude and latency for both auditory and visual tasks may be decreased by quetiapine treatment. Based on these results, we suggest that the atypical antipsychotic quetiapine may improve some aspects of cognitive domains in patients with schizophrenia.     

Clinical application of the P3 component of event-related potentials. I. Normal aging

Normal adult volunteer subjects ranging in age from 18 to 90 years participated in a study in which analogous auditory and visual paradigms, with infrequently occurring target and non-target events, were used to elicit event-related potentials (ERPs) with a prominent P3 component. Of the 135 subjects participating, 66 completed both auditory and visual paradigms. The amplitude and latency of P3 were analyzed using average ERPs, single trials (adaptive filter) and principal components analysis (PCA). Age regressions were calculated using measures derived from average ERPs and single trials. Single trial measures were better than average ERP measures in demonstrating age-related changes in P3 latency. There was a significant increase in P3 latency with age of 1-1.5 msec/year. The range of normal P3 latency for a given age (1 S.E. of the regression = 40 msec for the visual target stimuli) was much larger than obtained by other investigators. The visual paradigm produced higher P3 latency/age correlations than the auditory paradigm (visual target r = 0.52, non-target r = 0.42; auditory target r = 0.32, non-target r = 0.33). Within individuals, the amplitude and latency of P3 generated by auditory and visual stimuli were highly correlated, though the visual paradigm produced larger and later P3s than the auditory paradigm. There is an apparent change in the scalp topography of P3 with age. In young adults, P3s to target stimuli have a markedly parietal distribution. The distribution of P3 becomes more uniformly distributed from Pz to Fz with age. This may be due to changes in overlapping components such as the slow wave (SW) rather than to changes in the amplitude of P3 per se.     

Abnormalities in Event-Related Potentials, N100, P200, P300 and Slow Wave in Schizophrenia

Abstract: Event-related potentials were recorded in 54 schizophrenics and 88 age-matched controls during a two-tone discrimination (odd ball) task. All the subjects were free from medication. In the schizophrenics, the mean amplitudes of the N100, P300 and Slow Wave latency ranges were decreased, and the amplitude of the P200 latency range was greater than that for the controls. These reductions and the increase were found both for the ERPs elicited by rare target stimuli and for those elicited by frequent nontarget stimuli. The peak latency of N200 to rare stimuli was more prolonged in the schizophrenics than in the controls. This finding confirms the prolongation of N200 latency that Brecher et al. (1987) found for a different visual stimuli task. Neither the N100 nor P300 latency differed between the two groups.     

Probability and interstimulus interval effects on the N140 and the P300 components of somatosensory erps

Event-related potentials (ERPs) evoked by somatosensory stimuli were studied in two experiments with manipulation of the interstimulus interval (ISI) in the range from 1 to 4 seconds and the stimulus probability from 10 to 50% in fine steps. All the stimuli were presented randomly on both index fingers as odd-ball paradigm, and the stimulus intensities on both sides were equally set at 2.5 times the subjective sensory threshold at which the stimuli could easily be ignored when delivered as nontarget stimuli. During the course of two experiments, the N140 was evoked by the target and nontarget stimuli, otherwise the P300 was evoked by the target stimuli alone. In the experiment on the effects of ISIs change, the N140 amplitude showed a tendency to increase with increasing ISI and the P300 amplitude increased with increasing ISI. In the other experiment on the effects of change in stimulus probability, the amplitudes of both the N140 and the P300 decreased with increasing stimulus probability. From the results across two experiments. it is argued that the effects of both probability and ISI changes on the amplitudes of both the N140 and the P300 do not directly reflect the recovery time of psychological functions but may also involve the complicated effects derived from the habituation of the individual generators and the difficulty for performing the task. Moreover, it is indicated that the stimulus intensity used is one of major factors to be considered for comparing results to discuss the effects of ISI and probability on the ERPs.     

Frequency, intensity, and duration as determinants of P300 from auditory stimuli

The auditory event-related potential was assessed in two experiments that evaluated the effects of stimulus factors on P300 (P3) component amplitude and latency. The first experiment manipulated the frequency of the target stimuli (500, 1,000, 1,500, and 2,000 Hz) and standard stimuli (250 and 4,000 Hz) in different conditions. Both P3 amplitude and latency were affected by the target and standard tone combinations in specific ways. The second experiment varied the target tone intensity and duration factorially. P3 amplitude was unaffected by these variables, but peak latency was significantly shorter for the loudest and longest target stimuli. The findings indicate that variation in auditory stimulus parameters can produce small but reliable effects for P3 values, which should be considered when results are compared across studies.     

Alcoholism risk, tobacco smoking, and P300 event-related potential.

OBJECTIVE: The P300 event-related potential (ERP) is sometimes larger for individuals at low- compared to high-risk for alcoholism. These effects are inconsistent, and how P300 is affected by tobacco smoking in the context of alcoholism risk is unknown. The present study used P300 to examine the inter-relationship between alcoholism heritability and smoking status. METHODS: P300 was elicited with a visual discrimination task from young adults at low- and high-risk for alcoholism. Half of the subjects in each risk category reported that they did not smoke cigarettes, and the other half reported that they smoked regularly, with equal numbers of male and female subjects assessed. ERPs were recorded, and subjects were instructed to respond only to an infrequently presented target stimulus that occurred in a series of standard and distracter stimuli. RESULTS: P300 amplitude from the target stimuli was larger for the low-risk compared to high-risk subjects overall. However, smoking status demonstrated even stronger effects, with non-smokers producing consistently larger component amplitudes than smokers and accounting for more variance than alcoholism risk. These group factors also significantly affected P300 scalp topography. No reliable alcoholism risk or smoking group effects were obtained for the ERPs from the other stimuli. CONCLUSIONS: The findings suggest that P300 measures of alcoholism risk in young adults are moderated by smoking status. Theoretical implications are discussed.     

P300 generation by novel somatosensory stimuli.

Event-related potentials (ERPs) to task-relevant target and task-irrelevant novel stimuli were recorded in a somatosensory discrimination task. Subjects pressed a button to mechanical taps of the fifth finger (targets, P = 0.12), randomly interposed in sequences of taps to the second finger (standards, P = 0.76). Two types of infrequent novel stimuli were delivered; one was a mechanical tap to the third or fourth finger (tactile novels, P = 0.06), another was an electric shock at the wrist (shock novels, P = 0.06). Correctly detected targets generated a parietal maximal P300 (P3b, latency 335 msec). Shock novels generated a central maximal P300 with a shorter peak latency (298 msec) than the P3b. Tactile novels generated a P300 with a scalp distribution comparable to the shock novels. Unlike the P3b, P300 amplitude to both the shock and tactile novel stimuli habituated by 20-30% across the first several stimulus presentations. These results indicate that, similar to the auditory and visual modality, task-irrelevant novel somatosensory stimuli generate a novelty P300 ERP. Differences in scalp distribution, latency and habituation characteristics suggest that the novelty P300 may have contributions from intracranial generators independent from target P300 sources.     

The effects of interstimulus interval on event-related indices of attention: an auditory selective attention test of perceptual load theory.

OBJECTIVE: We examined the impact of perceptual load by manipulating interstimulus interval (ISI) in two auditory selective attention studies that varied in the difficulty of the target discrimination. METHODS: In the paradigm, channels were separated by frequency and target/deviant tones were softer in intensity. Three ISI conditions were presented: fast (300ms), medium (600ms) and slow (900ms). Behavioral (accuracy and RT) and electrophysiological measures (Nd, P3b) were observed. RESULTS: In both studies, participants evidenced poorer accuracy during the fast ISI condition than the slow suggesting that ISI impacted task difficulty. However, none of the three measures of processing examined, Nd amplitude, P3b amplitude elicited by unattended deviant stimuli, or false alarms to unattended deviants, were impacted by ISI in the manner predicted by perceptual load theory. CONCLUSIONS: The prediction based on perceptual load theory, that there would be more processing of irrelevant stimuli under conditions of low as compared to high perceptual load, was not supported in these auditory studies. SIGNIFICANCE: Task difficulty/perceptual load impacts the processing of irrelevant stimuli in the auditory modality differently than predicted by perceptual load theory, and perhaps differently than in the visual modality.     

Updating P300: an integrative theory of P3a and P3b.

The empirical and theoretical development of the P300 event-related brain potential (ERP) is reviewed by considering factors that contribute to its amplitude, latency, and general characteristics. The neuropsychological origins of the P3a and P3b subcomponents are detailed, and how target/standard discrimination difficulty modulates scalp topography is discussed. The neural loci of P3a and P3b generation are outlined, and a cognitive model is proffered: P3a originates from stimulus-driven frontal attention mechanisms during task processing, whereas P3b originates from temporal-parietal activity associated with attention and appears related to subsequent memory processing. Neurotransmitter actions associating P3a to frontal/dopaminergic and P3b to parietal/norepinephrine pathways are highlighted. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations.