Neurodynamic Studies on Emotional and Inverted Faces in an Oddball Paradigm

The detection of a change in a face stimulus was studied in an oddball paradigm. Event-related potentials (ERPs) and MEG responses to face stimuli were recorded in four conditions: 1) happy standard, neutral deviant; 2) neutral standard, neutral deviant; 3) inverted happy standard, inverted neutral deviant; 4) inverted neutral standard, inverted neutral deviant. In all conditions, the target was a face with glasses. Neutral deviants elicited a negative deflection (with a maximum around 280 ms) in ERP and MEG responses, an effect similar to auditory mismatch negativity. Face inversion diminished deviance-related negativity, implying an important role of face recognition in the observed effect. Emotional content and larger physical differences between stimuli in conditions 1 and 3 compared to conditions 2 and 4 did not show statistically significant effect on the neutral-deviant-related negativity.     

Word-specific cortical activity as revealed by the mismatch negativity

Neurophysiological brain activity evoked by individual spoken words and pseudowords was recorded and the mismatch negativity (MMN), an automatic index of experience-dependent auditory memory traces, was calculated. Consistent with earlier reported results, the MMN response to word-final syllables was enhanced compared with that elicited by the same syllables placed in a pseudoword context. Here we now demonstrate that the enhancement of the MMN elicited by two individual words showed different scalp topographies. The early word-specific brain activity is consistent with the assumption that the memory traces activated by individual words are carried by large neuronal ensembles that differ in their distributions over the cortex. Current source estimates localized the between-word differences in the right hemisphere and in parieto-occipital left-hemispheric areas. The differential brain responses to individual words appeared as early as ∼100 ms after the recognition points of the words, suggesting that their specific memory traces become active almost immediately after the information in the acoustic input is sufficient for word identification.     

Electrophysiological indices of acute effects of ethanol on involuntary attention shifting

Dose-related effects of ethanol (placebo, 0.30, and 0.60 g/kg) on behavioral and event-related brain potential (ERP) indices of involuntary attention shifting of audition were investigated. ERPs were recorded from 11 healthy social drinkers during a forced-choice reaction-time (RT) task. Subjects were presented with 100 and 200 ms tones (P = 0.50 for each) with a constant inter-stimulus interval (ISI) of 1 s. The task was to press either of two buttons, depending on the tone duration. The majority of the tones (“standards”) were of 700 Hz (P = 0.82). Occasionally, however, the frequency of the tones changed, deviating either slightly (750 Hz), moderately (900 Hz), or widely (1200 Hz; P = 0.06 for each) from the standard frequency. In accordance with previous findings, the task-irrelevant frequency deviations prolonged the RT. This RT prolongation was attenuated by alcohol with the 0.3 g/kg dose, thus suggesting less distraction by irrelevant stimulus deviations under the influence of ethanol. Furthermore, the P3a, reflecting involuntary attention shifting, was suppressed by alcohol even with the 0.3 g/kg dose. These findings demonstrate a detrimental effect of alcohol on involuntary attention shifting, evident with doses considerably smaller than previously described, and still juridically acceptable in road traffic in most countries. Received: 19 December 1997/Final version: 26 May 1998     

Effects of physiological aging on mismatch negativity: A meta-analysis

Mismatch negativity (MMN) is a promising window on how the functional integrity of auditory sensory memory and change discrimination is modulated by age and relevant clinical conditions. However, the effects of aging on MMN have remained somewhat elusive, particularly at short interstimulus intervals (ISIs). We performed a meta-analysis of peer-reviewed MMN studies that had targeted both young and elderly adults to estimate the mean effect size. Nine studies, consisting of 29 individual investigations, were included and the final total study population consisted of 182 young and 165 elderly subjects. The effects of different deviant types and duration of ISIs on the effect size were assessed. The overall mean effect size was 0.63 (95% CI at 0.43–0.82). The effect sizes for long ISI (> 2 s, effect size 0.68, 95% CI at 0.31–1.06) and short ISI (< 2 s, effect size 0.61, 95% CI at 0.39–0.84) were both considered moderate. A further analysis showed a prominent aging-related decrease in MMN responses to duration and frequency changes at short ISIs. It was also interesting to note that the effect size was about 25% larger for duration deviant condition compared to the frequency deviant condition. In conclusion, a reduced MMN response to duration and frequency deviants is a robust feature among the aged adults, which suggests that there has been a decline in the functional integrity of central auditory processing in this population.     

The auditory novelty system: An attempt to integrate human and animal research

In this account, we attempt to integrate two parallel, but thus far, separate lines of research on auditory novelty detection: (1) human studies of EEG recordings of the mismatch negativity (MMN), and (2) animal studies of single‐neuron recordings of stimulus‐specific adaptation (SSA). The studies demonstrating the existence of novelty neurons showing SSA at different levels along the auditory pathway's hierarchy, together with the recent results showing human auditory‐evoked potential correlates of deviance detection at very short latencies, that is, at 20–40 ms from change onset, support the view that novelty detection is a key principle that governs the functional organization of the auditory system. Furthermore, the generation of the MMN recorded from the human scalp seems to involve a cascade of neuronal processing that occurs at different successive levels of the auditory system's hierarchy.     

High ultrasound variability in chronic immune-mediated neuropathies. Review of the literature and personal observations

Chronic immune-mediated neuropathies show high clinical variability. Diagnosis is based on clinical and neurophysiological studies, but recently ultrasound (US) of peripheral nerves has been shown to provide useful morphological information. US has already been shown to crucially influence diagnosis and clinical care in entrapment neuropathies, in traumatic nerve lesions and in tumors. The role of US in the evaluation of polyneuropathies is still not clearly defined, but increasing attention has recently been focused on the immune-mediated neuropathies and specific US measures (namely the intra- and inter-nerve cross-sectional area variability) have been developed. The aim of the current paper is to make a review of the available nerve US studies and provide data from personal observations in the most common chronic immune-mediated neuropathies.     

Untangling syntactic and sensory processing: an ERP study of music perception

The present study investigated music-syntactic processing with chord sequences that ended on either regular or irregular chord functions. Sequences were composed such that perceived differences in the cognitive processing between syntactically regular and irregular chords could not be due to the sensory processing of acoustic factors like pitch repetition, pitch commonality (the major component of "sensory dissonance"), or roughness. Three experiments with independent groups of subjects were conducted: a behavioral experiment and two experiments using electroencephalography. Irregular chords elicited an early right anterior negativity (ERAN) in the event-related brain potentials (ERPs) under both task-relevant and task-irrelevant conditions. Behaviorally, participants detected around 75% of the irregular chords, indicating that these chords were only moderately salient. Nevertheless, the irregular chords reliably elicited clear ERP effects. Amateur musicians were slightly more sensitive to musical irregularities than nonmusicians, supporting previous studies demonstrating effects of musical training on music-syntactic processing. The findings indicate that the ERAN is an index of music-syntactic processing and that the ERAN can be elicited even when irregular chords are not detectable based on acoustical factors such as pitch repetition, sensory dissonance, or roughness.     

Auditory event-related potentials at preschool age in children born very preterm

ObjectiveTo assess auditory event-related potentials at preschool age in children born very preterm (VP, 27.4 ± 1.9 gestational weeks, n = 70) with a high risk of cognitive dysfunction.MethodsWe used an oddball paradigm consisting of a standard tone randomly replaced by one of three infrequent deviants (differing in frequency, sound direction or duration).ResultsThe P1 and N2 latencies were inversely correlated to age (50–63 months) both in VP (r = −0.451, p < 0.001, and r = −0.305, p = 0.01, respectively) and term born controls (TC; n = 15). VP children had smaller P1 than near-term (n = 12) or TC (1.70 ± 0.17 μV vs 2.68 ± 0.41 and 2.92 ± 0.43, respectively; p < 0.05). Mismatch negativity response did not differ between groups.ConclusionsOur data suggest a fast maturation of P1 and N2 responses with fast decrease in P1 and N2 latencies around the age of 5 years. Mismatch negativity response does not seem to be a robust measure for defining abnormalities in VP children.SignificanceIn ERP studies in preschool children, even small, non-significant group differences in age at recording should be corrected for. Very preterm born children at preschool age have aERP patterns as earlier described in full-term born children with cognitive deficits.