The topography of 4 subtraction ERP-waveforms derived from a 3-tone auditory oddball task in healthy young adults

Introduction: Five components were studied in 4 subtraction waveforms derived from ERPs obtained in passive and active conditions of a 3-tone oddball task (common=70%, C, 0.8 KHz; deviant=15%, D, 2 KHz; 1.4 KHz=15%, t, also used as a target (T)). These waveforms reflect different stimulus-mismatch processes and thus their topography could be revealing of different brain regions mediating them. Methods: The following mismatches were studied: stimulus-mismatch (deviant - common, D/C, rarity and pitch confounded, known as the mismatch negativity, MMN), pitch-mismatch (T - deviant, T/D, rarity not target features controlled, known as processing negativity PN), attention - mismatch (T - t), T/t, controlled for pitch and rarity to show the influence of target features, known as the Negative difference Nd). These are compared with Goodin's procedure (G-wv, (T-common (active) - (t-common (passive)- the "Goodin-waveform"). Results: There were main site effects in normalized data in all cases (not P2 and N2 latency). There were separate frontal and posterior contributions to P1, with the former emphasized where target comparisons were involved. Frontal N1 peaks, largest in D/C (MMN), spread posterior and to the right where target matching was involved. P2 posterior maxima were also less localized where target features were involved in the comparison. N2 topography was similar between waveforms but spread slightly more to each side in the T/t comparison (i.e. Nd). Onset was earlier in the D/C comparison (i.e MMN). Parietal P3 peaks in waves based on target-ERPs showed a left temporal shift (vs D/C), though in T/D P3 was in fact maximal on the right (i.e. PN waveform). Conclusions: Thus an attentional effect(controlled processing) is evident as early as 60 ms. Target features modify the anteroposterior distribution of positivity and negativity for the early components and in the lateralization of P3-like positivity. A comparison of waveforms by latency of potential shift (running t-test) vs. peak identification (MANOVA) is illustrated and discussed. D/C (MMN) and T/t (Nd) waveforms, rather than T/D or G-wv (PN & Goodin waveforms) waveforms are recommended for distinguishing comparator mechanisms for stimulus- and task-relevant features

Development and topography of auditory event-related potentials (ERPs): Mismatch and processing negativity in individuals 8-22 years of age

Introduction: How do ERPs reflecting auditory information processing develop across adolescence? This development is described for the amplitude and latency of five ERP components and four difference-waves in four groups of 11 healthy subjects with mean ages of 10, 14, 17 & 21 years. Methods: Vector normalised data were recorded from 19 sites during diffuse and focused attention in a three-tone oddball. (i.e. in passive, diffuse-attention and active, focussed-attention, discrimination conditions) to see how ERP loci varied with age for tone-type, attention-condition and for four types of difference-wave reflecting nontarget and target comparisons: (mismatch negativity, MMN, an auditory working memory trace; Negative difference, Nd, an attentional trace, but also Processing Negativity, PN and the Goodin-waveform). Results: Age interacted with site for most components. P1 loci sensitive to rare tones moved posteriorly and N1 loci lost their right bias at early puberty. But P2 loci did not move anterior to Cz until adulthood. N2 amplitude, sensitive to attention condition, developed a mature frontal focus by 17 years. Right-biased P3 loci move to the midline with focused attention in young and old alike. Difference-waves reflected three developmental stages (figure 2): In 10 year-olds early deflections (<150 ms) were diffusely distributed; in mid-adolescence the main frontal negative component (150-300 ms) became well-formed and lost an earlier right bias; over 17 years the late positive complex developed a right bias in target-derived waves. Latency decreases for early frontal components were marked in 10-14y olds and for later posterior components in 14-17y olds. MMN topography matured (from a right lateral to bilateral distribution) between 10 and 14 y, while Nd topography matured and became bilateral between 14 and 17y. Conclusions: Major developments of brain function appear at the onset of adolescence (<14y) in early stimulus-selection processes and during adolescence in the differential use of this information (N2- and P3-like latencies

Impaired attention-dependent augmentation of MMN in nonparanoid vs paranoid schizophrenic patients: a comparison with obsessive-compulsive disorder and healthy subjects

Introduction: Mismatch negativity (MMN), in the deviant-minus-standard event-related potential (ERP) difference-waveform, may represent a working memory trace for tone differences (a deviant among a sequence of standards). Most, but not all studies find MMN reduced in patients with schizophrenia. Aims: This report investigates if differences may be attributable to experimental condition (diffuse vs focused attention), component identification (N1-like vs N2-like), topographic distribution and clinical condition (with / without paranoid -hallucinatory symptoms, PH/NP). Comparisons were made for 12 PH and 12 NP schizophrenic patients with 13 obsessive compulsive and 25 normal control subjects. Results: Frontal MMN reduction in schizophrenics largely resulted from an absence of an increase in focused attention conditions as in comparison groups. But there was marked activity recorded from sites over the temporal lobe in NP patients. These features were not reflected in other components except for a visible but nonsignifiant N1-like temporal locus in NP patients. Further, schizophrenic patients did not show an increase in late positivity with focused attention like the comparison groups. Conclusions: The results show that so-called automatic processing deficits in schizophrenia (amount and locus of MMN) are best seen in situations requiring the activation of controlled attentional processes. It is suggested that impaired processing of irrelevant stimuli and reduced frontal MMN in NP patients may reflect reduced dopaminergic responsivity

Mismatch negativity (MMN) is altered by directing attention

Introduction: MMN is a negative component resulting from the difference in event-related potential (ERP) waveforms elicited by a standard and a deviant stimulus. It is usually studied in the absence of attentional requirements. Method: Here we compare this measure of perceptual comparison in a nontask situation (3 tones presented) with that obtained in a task requiring focussed attention and response to the third tone. Subjects were 9 male and 16 female healthy volunteers aged 18-25 years Results: MMN amplitude (comparison of standard and deviant irrelevant tones) increased with focussed attention to the third (target) tone and frontal maxima shifted slightly posteriorly. The succeding P3 in the difference waveform increased more posteriorly than frontally confirming continued differential processing of irrelevant stimuli under active conditions. Conclusion: This demonstrates that not only attending to stimuli, but the active processing of irrelevant stimuli (vs passive perception) involves small changes of the amount and distribution of neural activity. i.e. active controlled processing in focussed attention can affect the capacity or distribution of resources even for automatic processing of information (the MMN)

Auditory event-related potential (ERP) and difference-wave topography in schizophrenic patients with/without active hallucinations and deluisions: a comparison with young obsessive-compulsive disorder (OCD) and healthy subjects

Introduction: Event-related potentials (ERPs) in schizophrenics have been reported to show a reduced P3 on the left and less frontal mismatch negativity. But the specificity of such findings to component, its locus, the type of eliciting event and patient group remains uncertain. Hence, we examined ERP topography for P3, N2 and 3 precursor peaks according to stimulus (3-tone oddball), attention condition (diffuse/focused) and four types of difference-waves (Mismatch negativity, Processing negativity, Negative difference (Nd) and the 'Goodin-Waveform'). Method: We contrasted ERPs in a 3-tone oddball task-form in 24 healthy (mean 18.5y of age) and 13 OCD (mean age 16.3 y) subjects with schizophrenic patients with high versus low ratings of active delusions and hallucinations (12 paranoid-hallucinatory, PH [mean age 18.5y]; 12 nonparanoid, NP [mean age 18.9y]) Results: 1. P3 peaks were delayed and reduced in NP and PH groups. Peaks in the midline were usual in the focused attention condition, but a right bias in diffuse attention (passive presentation). 2. P3 responses to irrelevant non-targets remained lateralised in NP, and small in OCD patients. All showed a small left and anterior bias in the P3-like peak recorded after subtraction in the difference waves. 3. Mismatch negativity (MMN) peaks shifted to the right in OCD, laterally to both sides in PH and more posteriorly in NP patients. 4. Frontal processing negativity was biased to the left (early) in NP and to the right (late) in PH groups. 5. Early peak topography in the difference waveforms reflected some of these later changes (e.g., for PH and NP groups the normal right bias in the P1-like peak was absent; the N1-like peak was reduced and widely distributed: for the NP group, the P2-like peak appeared smaller on the left). 6. In OCD patients, the peak latencies were topographically undifferentiated for P1 and P2, or delayed in the case of the N2 component. Conclusions: A) The OCD group showed an unusual regional allocation of processing effort. B) Before 200 ms, fronto-central activity was more widespread in both the PH and NP groups. C) NP patients, in particular, treated irrelevant stimuli anomalously. D) Lateralisation of negativity in target- and nontarget-derived difference waves may reflect differential disruption of the frontal-temporal dialogue in registering important vs. unimportant features. Indeed, the apparent left/right differences of negative difference (Nd) or processing negativity amplitude may not so much reflect amplitude differences as a delayed latency over left frontal areas in PH and over the right frontal areas in NP patients with schizophrenia

A frontal attention mechanism in the visual mismatch negativity

Automatic detection of environmental change is a core component of attention. The mismatch negativity (MMN), an electrophysiological marker of this mechanism, has been studied prominently in the auditory domain, with cortical generators identified in temporal and frontal regions. Here, we combined electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to assess whether the underlying frontal regions associated with auditory change detection also play a role in visual change detection. Twenty healthy young adults completed a visual MMN task in separate EEG and fMRI sessions. Region of interest analyses were conducted on left and right middle frontal (MFG) and inferior frontal (IFG) gyri, i.e., the frontal areas identified as potential auditory MMN generators. A significant increase in activation was observed in the left IFG and MFG in response to blocks containing deviant stimuli. These findings suggest that a frontal mechanism is involved in the detection of change in the visual MMN. Our results support the notion that frontal mechanisms underlie attention switching, as measured via MMN, across multiple modalities

Functional neuroanatomy of auditory sensory memory

Abstract not available