P3a Response Research Articles

P3b versus P3a: an event-related potential investigation of the glucose facilitation effect

The ingestion of a glucose containing drink has been shown to improve performance on a variety of cognitive tasks. There is debate, however, as to whether glucose especially benefits hippocampal memory functioning or whether it has a more global effect on attentional systems. The present study used event related potential methodology (ERPs) to investigate further glucose-mediated cognitive processes. Each participant acted as his/her own control in a repeated measures design, receiving one of two possible treatments (25 g glucose vs. placebo) in a counterbalanced order. After a two hour fasting period participants completed a visual three-stimulus oddball task. This paradigm involves an individual detecting an infrequent target stimulus randomly embedded in a train of repetitive background or standard stimuli. Detection of the target results in a large P3b ERP component (memory updating effect). The infrequent presentation of a novel and irrelevant stimulus, randomly interspersed with the target and standard stimuli, generates a P3a response (orientation of attention effect). These components were used as markers to establish whether the glucose enhancement effect was restricted to the neuro-cognitive processes related to memory. Consistent with behavioural work, glucose moderated the magnitude and latency of the P3b ERP component. However, glucose also interacted with attentional systems (P3a and an earlier P2), although this effect was non-significant. This work converges with recent fMRI findings indicating the sensitivity of the medial-temporal lobes and the pre-frontal cortex to glucose administration.

Event-related potentials to pitch and rise time change in children with reading disabilities and typically reading children

Objective The purpose of the present study was to investigate whether children with reading disabilities (RD) process rise time and pitch changes differently to control children as a function of the interval between two tones. Methods Children participated in passive oddball event-related potential (ERP) measurements using paired stimuli. Mismatch negativity (MMN), P3a and late discriminative negativity (LDN) responses to rise time and pitch changes were examined. Results Control children produced larger responses than children with RD to pitch change in the P3a component but only when the sounds in the pair were close to each other. Compared to children with RD, MMN was smaller and LDN larger in control children in response to rise time change when the sounds in the pair were further apart. The non-overlap in ERP measures between the groups was 40–50%. Conclusions Problems in rapid processing of pitch change were reflected in a component associated with attention switching while amplitude envelope processing problems were reflected in components associated with stimulus detection or discrimination. Significance Children with RD process both rise time and pitch changes differently from control children thus providing evidence for the nature of amplitude envelope processing and rapid auditory processing deficits in dyslexia.

Preattentive Sensory Processing as Indexed by the MMN and P3a Brain Responses is Associated with Cognitive and Psychosocial Functioning in Healthy Adults

Understanding the basic neural processes that underlie complex higher order cognitive operations and psychosocial functioning is a fundamental goal of cognitive neuroscience. Event-related potentials allow investigators to probe the earliest stages of information processing. Mismatch negativity (MMN) and P3a are auditory event-related potential components that reflect automatic sensory discrimination. The aim of the present study was to determine if MMN and P3a are associated with higher order cognitive operations and psychosocial functioning in clinically normal healthy subjects. Twenty adults were assessed using standardized clinical, cognitive, and psychosocial functional instruments. All individuals were within the normal range on cognitive tests and functional ratings. Participants were also tested on a duration-deviant MMN/P3a paradigm (50-msec standard tones, p = .90; 100-msec deviant tones, p = .10; stimulus onset asynchrony [SOA] = 505 msec). Across fronto-central electrode regions, significant correlations were observed between psychosocial functioning and MMN (r = -.62, p < .01) and P3a (r = .63, p < .01) amplitudes. P3a amplitude was also highly associated with immediate and delayed recall of verbal information with robust correlations widely distributed across fronto-central recording areas (e.g., r = .72, p < .001). The latency of the P3a response was significantly associated with both working memory performance (r = -.53, p < .05) and functional ratings (r = -.48, p < .05). Neurophysiological measures of relatively automatic auditory sensory information processing are associated with higher order cognitive abilities and psychosocial functioning in normal subjects. Efficiency at elementary levels of information processing may underlie the successful encoding, retrieval, and discrimination of task-relevant information, which, in turn, facilitates the iterative and responsive processing necessary for adaptive cognitive and social functioning.

Heterogeneity in the Patterns of Neural Abnormality in Autistic Spectrum Disorders: Evidence from ERP and MRI

Autistic spectrum disorder (ASD) refers to a heterogeneous group of social communication problems. Research into the neural basis of ASD has revealed abnormalities in a number of different regions of the brain. However, the literature is highly inconsistent. One possible explanation for these discrepancies is differences in intelligence. Children with ASD and below average intelligence may be hypothesised to show additional or different neural abnormalities. This possibility was explored using structural magnetic resonance imaging (MRI) and event-related potentials (ERP). Two groups of children with ASD were studied, those with average or above average intelligence (high ASD group) and those with below average intelligence (low ASD group). The structural MRI data were analysed using voxel-based morphometry (VBM). Using the family-wise error threshold, results showed bilateral abnormality common to the two ASD groups in the cerebellum, fusiform gyrus and frontal cortex. In addition, a number of regions were found to be significantly different in the two ASD groups: regions of the cerebellum showed increased grey matter density bilaterally in the high ASD group, but decreased grey matter density bilaterally in the low ASD group. Further, compared to the high ASD group, additional bilateral abnormalities were found in the postcentral gyrus and regions of the dorsolateral prefrontal cortex in the low ASD group. Using the less stringent false discovery rate (FDR) threshold, differences were also seen in the medial temporal lobes. ERPs also showed differences between the two ASD groups. Whereas the ERPs of the high ASD group were not significantly different from those of the controls, the low ASD group had delayed novelty P3a responses and reduced amplitude target P3b components. These data provide convergent ERP and MRI evidence for the heterogeneity of neural abnormality in ASD in relation to variations in intelligence.

Attentional load of the primary task influences the frontal but not the temporal generators of mismatch negativity

According to the model hypothesized by Näätänen and Michie (Biol Psychol 1979; 8: 81–136), the generation of the mismatch negativity (MMN) requires a mismatch detection, taking place in temporal areas, followed by the activation of frontal generators, underlying attention switching toward the deviant stimulus. We aimed at verifying whether the activation of temporal and frontal regions is dependent on the amount of attentional resources allocable toward the deviant stimulus. We recorded event-related potentials (ERPs) in nine healthy subjects while reading and during a demanding visual task (Multiple Features Target Cancellation, MFTC). Raw data were further evaluated by Brain Electrical Source Analysis (BESA). During the Reading condition, distraction toward the unattended auditory stimuli was reflected by the enhancement of the N1 response to frequent stimuli and by the elicitation of a P3a response to deviant ones. The MMN distribution was explained by bilateral temporal dipoles. During the MFTC condition, no P3a was detected, while source analysis showed the activation of a right frontal generator. Temporal dipoles showed no change between the two conditions: we thus conclude that the earlier mismatch detection is independent on the attentional load. By contrast, the activation of a right frontal subcomponent occurred only during the high-load task, independently on any actual attention shift reflected by the P3a component. We thus discuss the hypothesis whether the right frontal MMN generator, rather than subserving a simple attention switching toward the deviant stimulus, plays a role in modulating the auditory change detection system (“contrast enhancement” model).

Effects of cold stress on early and late stimulus gating

The P50 component of the event-related potential (ERP) mainly reflects early pre-attentional processing. Along with P50, the N100 component and mismatch negativity (MMN) were postulated to represent a complex multistage and multi-component gating system. If some variable threshold or gating is exceeded by the MMN signal, the MMN is often followed by a relatively sharp fronto-central positive wave, the P3a component, which reflects an attentional switch to an environmental change. The P50 was shown to be affected by mental and cold stress, and the P3a amplitude was shown to be increased by the anticipation of threat. The aim of this study is to examine concurrently the early and late ERP indices of gating during acute stress. The ERPs to auditory stimuli in a passive oddball paradigm were recorded in 15 normal subjects during the cold pressor test and a control condition. The cold pressor test diminished P50 gating, increased N100 amplitude, elicited P3a responses and had no significant effect on MMN. Transient stress could impair early sensory gating and the ability to ignore irrelevant information that can cause passive attention switches indexed by the P3a component.

Aging effects on the ERP correlates of involuntary attentional capture in speech sound analysis

In an auditory oddball paradigm, 16 old and 16 young adults were asked to ignore binaurally presented disyllabic speech sounds and to watch a silent movie while event-related potentials (ERPs) were recorded. Four types of phonetic deviants occurred on, respectively: (1) the Stressed-First syllable, (2) the Unstressed-First syllable, (3) the Stressed-Second syllable and (4) the Unstressed-Second syllable. The nature of the phonetic change was the same across the four deviants. A P3a was seen only for deviant 3 in the elderly while observed for deviants 1 and 3 in the young. The mismatch negativities (MMNs) to deviants 1 and 2 were reduced compared with those to the other two deviants in both age groups. It is concluded that the ability to use salient prosody to involuntarily capture attention for speech sounds is preserved in normal aging. The lack of P3a response to deviant 1 in the elderly may result from the combined effects of backward masking and age-related temporal encoding inefficiency as indicated by reduced MMNs for the elderly.

Subtitled videos and mismatch negativity (MMN) investigations of spoken word processing.

The purpose of this study was to determine whether the presence of subtitles on a distracting, silent video affects the automatic mismatch negativity (MMN) response to simple tones, consonant-vowel (CV) nonwords, or CV words. Two experiments were conducted in this study, each including ten healthy young adult subjects. Experiment 1 investigated the effects of subtitles on the MMN response to simple tones (differing in frequency, duration, and intensity) and speech stimuli (CV nonwords and CV words with a /d/-/g/ contrast). Experiment 2 investigated the effects of subtitles on the MMN response to a variety of CV nonword and word contrasts that incorporated both small (e.g., /d/ vs. /g/) and/or large (e.g., /e:/ vs. /el/) acoustic deviances. The results indicated that the presence or absence of subtitles on the distracting silent video had no effect on the amplitude of the MMN or P3a responses to simple tones, CV nonwords, or CV words. In addition, the results also indicated that movement artifacts may be statistically reduced by the presence of subtitles on a distracting silent video. The implications of these results are that more "engaging" (i.e., subtitled) silent videos can be used as a distraction task for investigations into MMN responses to speech and nonspeech stimuli in young adult subjects, without affecting the amplitude of the responses.

Nociceptive processing in the human brain of infrequent task-relevant and task-irrelevant noxious stimuli. A study with event-related potentials evoked by CO 2 laser radiant heat stimuli

Laser evoked potentials (LEPs) are nociceptive-related brain responses to activation of cutaneous nociceptors by laser radiant heat stimuli. We previously showed that LEP amplitude during the P2 period (∼400 ms) was increased by rare noxious stimuli, inside and outside the focus of spatial attention. It was postulated that this effect reflected a P3a response indexing an involuntary shift of attention. In the present study, LEPs were recorded in a three-stimulus oddball paradigm, commonly used to evoke P3a (or novelty-P3). CO 2 laser-induced noxious stimuli were delivered on one hand (80%, frequent). Two series of rare stronger-intensity deviant stimuli were randomly intermixed: target stimuli (10%) were delivered on the same hand while distractor stimuli (10%) were delivered on the other hand. Subjects were instructed to count targets. During an additional session, strong stimuli were delivered alone on one hand without instruction (100%, no-task stimuli). All stimulus types evoked a first positivity around 360 ms (P360). Targets and distractors elicited a late positive complex (LPC) around 465–500 ms. Topography of LPC to distractors was central and significantly more anterior than that of LPC to targets. Distractor LPC corresponds to P3a (or novelty-P3) indexing an involuntary orientation of attention toward an unexpected new/deviant event. It suggests that at least an early part of the LEP positivity (P360) is independent of P3-activities.

Think differently: a brain orienting response to task novelty.

Cognitive flexibility hinges on a readiness to direct attention to novel events, and on an ability to change one's mental set to find new solutions for old problems. Human event-related potential (ERP) studies have described a brain 'orienting' response to discrete novel events, marked by a frontally distributed positive potential peaking 300-400 ms post-stimulus (P3a). This brain potential has been typically related to bottom-up processing of novel non-targets under a fixed task-set (i.e., press a button to coloured targets), but had never been related to top-down attention control in dual-task paradigms. In this study, 27 subjects had their ERPs measured while they performed a version of the Wisconsin card sorting test (WCST), a dual-task paradigm where the same feedback cue signalled unpredictable shifts to a new task set (i.e., from 'sort by colour' to 'sort by shape'). Feedback cues that directed a shift in the subject's mental set to a new task-set elicited frontally distributed P3a activity, thus suggesting a role of the P3a response system in task-set shifting. Feedback cues also evoked a longer latency positive potential (350-600 ms; P3b), that was larger the more task rules were held in memory. In line with current models of prefrontal function in the executive control of attention, this P3a/P3b response system appears to reflect the co-ordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory.

Maturation of the auditory change detection response in infants: a longitudinal ERP study.

Mismatch negativity (MMN) is a negative component of auditory event-related potential (ERP), reflecting the brain's automatic change detection process. In the present study we investigated the development of the pitch change detection, as indexed by the MMN, in the same infants from birth until 12 months of age. The MMN was identified in approximately 75% of infants at each age, being relatively stable in latency and amplitude at the group level across the ages studied. However, within the same subjects the MMN substantially varied from age to age. The inspection of individual data revealed a possible source of this variability: in a portion of 3- to 9-month-old infants, a large-amplitude positive component commenced at the latency of the MMN and thus might have masked it. The results of the additional experiment, employing distracting novel sounds in 2-year-old infants and newborns, suggested that the observed positive component could represent an infant analogue of the adult P3a response, indexing an involuntary orienting of attention. Therefore, the variability from age to age might be, at least partially, caused by the differences in degree of infants' orienting, resulting in the reduction of the scalp recorded mismatch negativity in recordings when the orienting P3a positivity was elicited.

Predictive value of novel stimuli modifies visual event-related potentials and behavior

Objective: We examined how behavioral context influences novelty processing by varying the degree that a novel event predicted the occurrence of a subsequent target stimulus.Methods: Visual event-related potentials (ERPs) and reaction times (RTs) were recorded in 3 detection experiments (23 subjects). The predictive value of a novel stimulus on the occurrence of a subsequent target was varied as was novel-target pairing intervals (200–900 ms). In Experiment 1, novel stimuli always preceded a target, in Experiment 2, 40% of novel stimuli were followed by a target, and in Experiment 3, novel stimuli occurred randomly.Results: In Experiment 1, RTs following 100% predictive novels were shortened for targets at all spatial locations and novel-target pairing intervals. Novel stimuli predicting a target generated a central negativity peaking at 300 ms and reduced P3a and P3b ERPs. In Experiments 2 and 3, target RTs were prolonged only when novel and target stimuli were presented in the same spatial location at short ISIs (200 ms). The central novel N2 was smaller in amplitude in comparison to Experiment 1, and novelty P3a and target extrastriate N2 and posterior scalp P3b ERPs were enhanced.Conclusions: The enhanced N2 for100% predictive novel stimuli appears to index an alerting system facilitating behavioral detection. The same novel stimuli with no predictive value distract attention and generate a different ERP pattern characterized by increased novelty P3a and target P3b responses. The results indicate that behavioral context determines how novel stimuli are processed and influence behavior.

Effect of blood collection tubes on tricyclic antidepressant blood levels

Involuntary switching of attention to distracting sounds was studied by measuring effects of these events on auditory discrimination performance and event-related brain potentials (ERPs) in 6–11-year-old boys with Attention Deficit – Hyperactivity Disorder (ADHD) and comorbid Oppositional Defiant Disorder (ODD) and in age-matched controls. The children were instructed to differentiate between two animal calls by pressing one response button, for example, to a dog bark and another button to a cat mew. These task-relevant sounds were presented from one of two loudspeakers in front of the child, and there were occasional task-irrelevant changes in the sound location, that is, the loudspeaker. In addition, novel sounds (e.g., a sound of hammer, rain, or car horn) unrelated to the task were presented from a loudspeaker behind the child. The percentage of correct responses was lower for target sounds preceded by a novel sound than for targets not preceded by such sound in the ADHD group, but not in the control group. In both groups, a biphasic positive P3a response was observed in ERPs to the novel sounds. The later part of the P3a appeared to continue longer over the frontal scalp areas in the ADHD group than in the controls presumably because a reorienting negativity (RON) ERP response following the P3a was smaller in the ADHD group than in the control group. This suggests that the children with ADHD had problems in reorienting their attention to the current task after a distracting novel sound leading to deterioration of performance in this task. The present study also indicates that children with ADHD and comorbid ODD show same kind of distractibility as found in previous studies for children with ADHD without systematic comorbid ODD.

Neural mechanisms of involuntary attention to acoustic novelty and change.

Behavioral and event-related brain potential (ERP) measures were used to elucidate the neural mechanisms of involuntary engagement of attention by novelty and change in the acoustic environment. The behavioral measures consisted of the reaction time (RT) and performance accuracy (hit rate) in a forced-choice visual RT task where subjects were to discriminate between odd and even numbers. Each visual stimulus was preceded by an irrelevant auditory stimulus, which was randomly either a "standard" tone (80%), a slightly higher "deviant" tone (10%), or a natural, "novel" sound (10%). Novel sounds prolonged the RT to successive visual stimuli by 17 msec as compared with the RT to visual stimuli that followed standard tones. Deviant tones, in turn, decreased the hit rate but did not significantly affect the RT. In the ERPs to deviant tones, the mismatch negativity (MMN), peaking at 150 msec, and a second negativity, peaking at 400 msec, could be observed. Novel sounds elicited an enhanced N1, with a probable overlap by the MMN, and a large positive P3a response with two different subcomponents: an early centrally dominant P3a, peaking at 230 msec, and a late P3a, peaking at 315 msec with a right-frontal scalp maximum. The present results suggest the involvement of two different neural mechanisms in triggering involuntary attention to acoustic novelty and change: a transient-detector mechanism activated by novel sounds and reflected in the N1 and a stimulus-change detector mechanism activated by deviant tones and novel sounds and reflected in the MMN. The observed differential distracting effects by slightly deviant tones and widely deviant novel sounds support the notion of two separate mechanisms of involuntary attention.

Event-related potential evidence for frontal cortex effects of chronic cocaine dependence

We examined the effects of cocaine dependence and cocaine and alcohol codependence on the P3A event-related potential component. Ten chronic cocaine-dependent subjects, 10 chronic cocaine and alcohol codependent subjects, and 20 controls were studied in an auditory paradigm that included target, nontarget, and novel rare nontarget conditions. Substance-dependent subjects were abstinent from cocaine and/or alcohol for 2-6 weeks. Eighteen of these subjects (4 chronic cocaine-dependent subjects, 4 chronic cocaine/alcohol codependent subjects, and 10 normal controls) were also studied in an analogous visual paradigm. In the auditory modality, the latency of the P3A response in the novel rare nontarget condition was delayed and its amplitude was reduced in both substance-dependent samples compared to controls. Comparable results were found for the smaller samples studied in the visual modality. These results suggest that chronic cocaine dependence produces deficits in frontal cortex functions.

Delayed P3A in Abstinent Elderly Male Chronic Alcoholics

Significant central nervous system toxicity in frontal brain regions has been demonstrated with chronic alcohol consumption both on autopsy and using neuropsychological testing. This study examined the latency of an objective and reproducible brain event-related potential measure of frontal cortex function in chronic elderly male alcoholics who were abstinent 3 months-2 years, a patient group in whom the central nervous system effects of chronic alcohol abuse are thought to be largest and most persistent. We examined the latency of the P3A event-related potential component, which reflects a frontal maximum orienting response to novel stimuli. Twelve elderly abstinent chronic alcoholic males and 11 elderly male controls were studied in an auditory and a visual paradigm, each of which included target, nontarget, and novel rare nontarget conditions. In both modalities, the P3A response to the novel rare nontarget stimuli was significantly delayed in the chronic alcoholics. P3B delays to the target stimuli were also present in the alcoholics, with the P3A and P3B effects being independent of each other. For both P3A and P3B, the effects were larger and more consistent in the visual compared with the auditory modality. Our conclusions are as follows: (1) both P3A and P3B latency delays are evident in elderly abstinent chronic alcoholics; (2) separate mechanisms are responsible for these effects; (3) these effects are more sensitively detected in the visual versus the auditory modality; and (4) delayed P3A latency may be an objective and reproducible index of the frontal cortex effects of chronic alcohol abuse.