Event-related potentials during individual, cooperative, and competitive task performance differ in subjects with analytic vs. holistic thinking

It has been presented that Western cultures (USA, Western Europe) are mostly characterized by competitive forms of social interaction, whereas Eastern cultures (Japan, China, Russia) are mostly characterized by cooperative forms. It has also been stated that thinking in Eastern countries is predominantly holistic and in Western countries analytic. Based on this, we hypothesized that subjects with analytic vs. holistic thinking styles show differences in decision making in different types of social interaction conditions. We investigated behavioural and brain-activity differences between subjects with analytic and holistic thinking during a choice reaction time (ChRT) task, wherein the subjects either cooperated, competed (in pairs), or performed the task without interaction with other participants. Healthy Russian subjects (N=78) were divided into two groups based on having analytic or holistic thinking as determined with an established questionnaire. We measured reaction times as well as event-related brain potentials. There were significant differences between the interaction conditions in task performance between subjects with analytic and holistic thinking. Both behavioral performance and physiological measures exhibited higher variance in holistic than in analytic subjects. Differences in amplitude and P300 latency suggest that decision making was easier for the holistic subjects in the cooperation condition, in contrast to analytic subjects for whom decision making based on these measures seemed to be easier in the competition condition. The P300 amplitude was higher in the individual condition as compared with the collective conditions. Overall, our results support the notion that the brains of analytic and holistic subjects work differently in different types of social interaction conditions.

The brains of high functioning autistic individuals do not synchronize with those of others

Multifaceted and idiosyncratic aberrancies in social cognition characterize autism spectrum disorders (ASDs). To advance understanding of underlying neural mechanisms, we measured brain hemodynamic activity with functional magnetic resonance imaging (fMRI) in individuals with ASD and matched-pair neurotypical (NT) controls while they were viewing a feature film portraying social interactions. Pearson's correlation coefficient was used as a measure of voxelwise similarity of brain activity (InterSubject Correlations—ISCs). Individuals with ASD showed lower ISC than NT controls in brain regions implicated in processing social information including the insula, posterior and anterior cingulate cortex, caudate nucleus, precuneus, lateral occipital cortex, and supramarginal gyrus. Curiously, also within NT group, autism-quotient scores predicted ISC in overlapping areas, including, e.g., supramarginal gyrus and precuneus. In ASD participants, functional connectivity was decreased between the frontal pole and the superior frontal gyrus, angular gyrus, superior parietal lobule, precentral gyrus, precuneus, and anterior/posterior cingulate gyrus. Taken together these results suggest that ISC and functional connectivity measure distinct features of atypical brain function in high-functioning autistic individuals during free viewing of acted social interactions. Our ISC results suggest that the minds of ASD individuals do not ‘tick together’ with others while perceiving identical dynamic social interactions.

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We studied brain function in autism during free viewing of social interactions.

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The brains of individuals with autism do not ‘tick together’ with others.

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Long-range functional connectivity is altered in individuals with autism.

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Link between autistic traits and social brain synchrony extends to normal population.

Brain state-triggered stimulus delivery: An efficient tool for probing ongoing brain activity

What is the relationship between variability in ongoing brain activity preceding a sensory stimulus and subsequent perception of that stimulus? A challenge in the study of this key topic in systems neuroscience is the relative rarity of certain brain 'states'-left to chance, they may seldom align with sensory presentation. We developed a novel method for studying the influence of targeted brain states on subsequent perceptual performance by online identification of spatiotemporal brain activity patterns of interest, and brain-state triggered presentation of subsequent stimuli. This general method was applied to an electroencephalography study of human auditory selective listening. We obtained online, time-varying estimates of the instantaneous direction of neural bias (towards processing left or right ear sounds). Detection of target sounds was influenced by pre-target fluctuations in neural bias, within and across trials. We propose that brain state-triggered stimulus delivery will enable efficient, statistically tractable studies of rare patterns of ongoing activity in single neurons and distributed neural circuits, and their influence on subsequent behavioral and neural responses.

Effects of haloperidol on selective attention: a combined whole-head MEG and high-resolution EEG study

We used 122-channel magnetoencephalography (MEG) and 64-channel electroencephalogrphy (EEG) simultaneously to study the effects of dopaminergic transmission on human selective attention in a randomized, double-blind placebo-controlled cross-over design. A single dose of dopamine D2 receptor antagonist haloperidol (2 mg) or placebo was given orally to 12 right-handed healthy volunteers 3 hours before measurement. In a dichotic selective attention task, subjects were presented with two trains of standard (700 Hz to the left ear, 1,100 Hz to the right ear) and deviant (770 and 1,210 Hz, respectively) tones. Subjects were instructed to count the tones presented to one ear; whereas, the tones presented to the other ear were to be ignored. Haloperidol significantly attenuated processing negativity (PN), an event-related potential (ERP) component elicited by selectively attended standard tones at 300-500 ms after stimulus presentation. These results, indicating impaired selective attention by a blockade of dopamine D2 receptors, were further accompanied with increased mismatch negativity (MMN), elicited by involuntary detection of task-irrelevant deviants. Taken together, haloperidol seemed to induce functional changes in neural networks accounting for both selective and involuntary attention, suggesting modulation of these functions by dopamine D2 receptors.

No evidence for dependence of early cortical auditory processing on dopamine D(2)-receptor modulation: a whole-head magnetoencephalographic study

Magnetoencephalography (MEG) was used to determine the effect of neuroleptic challenge on brain responses in healthy subjects. In a double-blind, randomized, placebo-controlled, cross-over design study, the dopamine D(2) receptor antagonist haloperidol (2 mg) was given orally to 12 healthy volunteers. The middle-latency auditory evoked magnetic fields (MAEF) were recorded 3 h after administration of haloperidol or placebo with a whole-head 122-channel MEG. Haloperidol did not significantly affect MAEF responses. The dipole moments and source locations of the responses were not significantly influenced by haloperidol. These results suggest that dopamine D(2) receptors are not involved in the early phases of auditory cortical processing.

Auditory sensory memory and the cholinergic system: implications for Alzheimer's disease

Auditory sensory memory represents one of the simplest types of short-term memory that can be studied electrophysiologically with mismatch negativity (MMN); a specific auditory event-related potential indexing automatic comparison of incoming stimuli to an existing memory trace. Previous results suggest that auditory sensory memory deteriorates in aging and especially in Alzheimer's disease (AD). It has remained unsettled, however, whether MMN is regulated by the cholinergic system, which is deteriorated in AD contributing to cognitive impairments. We recorded cortical auditory responses with a magnetometer from 13 healthy subjects after intravenous injection of scopolamine, centrally acting cholinergic antagonist, or glycopyrrolate, a drug with a peripheral anticholinergic properties without penetrating the blood-brain barrier, using a double-blind protocol. Scopolamine reduced MMNm amplitude in response to frequency, but not duration, change, increased P50m amplitude, and delayed N100m latency. These findings suggest that the cholinergic system regulates the frequency-specific comparison of incoming stimuli to existing memory trace and modulates the preattentive processing related to stimulus detection. Further, neural mechanisms responsible for cortical frequency- and duration-specific discrimination appear to have different sensitivities to cholinergic modulation. Auditory evoked potentials might be suitable to monitor cholinergic activity in AD.

Scopolamine reduces the P35m and P60m deflections of the human somatosensory evoked magnetic fields

Acetylcholine (ACh) is a potent neuromodulator in the brain with multiple, complex effects on neuronal function, most of which are mediated by muscarinic receptors. Generally, the most significant effect is excitation of pyramidal neurones and facilitation of responses to afferent stimulation. Much of the information on the ACh effects comes from studies utilizing in vitro or anesthetized in vivo preparations, while fewer data are available from awake animals or humans. We studied human somatosensory evoked magnetic fields (SEFs), which reflect summated postsynaptic currents in pyramidal neurones in area 3b, and in the opercular somatosensory cortex, when cholinergic transmission was modulated either by a central (scopolamine, 0.3 mg, i.v.) or peripheral (glycopyrrolate, 0.2 mg, i.v.) muscarinic antagonist. A randomized, double-blind, cross-over design was employed. SEFs were elicited by right median nerve stimulation at the wrist with constant-current pulses above motor threshold. The first excitatory cortical response from area 3b (N20m) was not affected by the central muscarinic blockade, while later P35m and P60m deflections were significantly reduced. The responses from the opercular somatosensory cortex showed some tendency toward reduction, but no significant alterations. The results show that somatosensory cortical processing can be modulated by muscarinic transmission at a relatively early stage. Relative membrane hyperpolarization of pyramidal neurons due to scopolamine (caused by blocking an ACh-induced tonic depolarization) is discussed as a possible mechanism underlying the observed effects.

Increased distractibility by task-irrelevant sound changes in abstinent alcoholics

BACKGROUND

Chronic alcoholism is accompanied by "frontal" neuropsychological deficits that include an inability to maintain focus of attention. This might be associated with pronounced involuntary attention shifting to task-irrelevant stimulus changes and, thereafter, an impaired reorienting to the relevant task. The neural abnormalities that underlie such deficits in alcoholics were explored with event-related potential (ERP) components that disclosed different phases of detection and orienting to stimulus changes.

METHODS

Twenty consecutive abstinent male alcoholics (DSM-IV) and 20 age-matched male controls (healthy social drinkers) were instructed to discriminate equiprobable 100 and 200 msec tones in a reaction-time task (RT) and to ignore occasional, either slight (7%) or wide (70%), frequency changes (hypothesized to increase RT) during an ERP measurement.

RESULTS

In the alcoholics, we found pronounced distractibility, evidenced by a RT lag (p < 0.01) caused by deviants, that correlated (Spearman p = 0.5) with a significantly enhanced (p < 0.01) amplitude of mismatch negativity (MMN) to deviants. Significantly increased RT lag for trials subsequent to deviants (slight p < 0.001, wide p < 0.05) in the alcoholics suggested impaired reorienting to the relevant task. The MMN enhancement also predicted poorer hit rates in the alcoholics (Spearman p = 0.6-0.7). Both the MMN enhancement and pronounced distractibility correlated (Spearman p = 0.4) with an early onset of alcoholism.

CONCLUSIONS

Attentional deficits in the abstinent alcoholics were indicated by the increased distractibility by irrelevant sound changes. The MMN enhancement suggested that this reflects impaired neural inhibition of involuntary attention shifting, being most pronounced in early-onset alcoholics.

Acute and chronic effects of alcohol on preattentive auditory processing as reflected by mismatch negativity

Chronic alcoholism, a major worldwide health problem, is associated with a variety of neurocognitive changes in the afflicted individuals. The precise neurophysiological basis of these changes is not yet understood. Mismatch negativity (MMN) is a preattentive event-related potential component indexing cortical auditory memory traces and automatic change detection in the brain that can be used to study the neural basis of cognitive impairments in various neurodegenerative diseases. MMN studies have revealed that even a low dose of acute alcohol significantly impairs automatic change detection and involuntary attention shifting. Recent MMN results on chronic alcoholism in turn suggest that auditory sensory traces decay slightly faster and are substantially more vulnerable to the distracting effect of backward masking in alcoholics than in healthy subjects. Furthermore, chronic alcohol abuse might accelerate the age-related impairment of automatic change detection. There is also evidence that the MMN changes might predict impaired performance in behavioral memory and attention tasks in alcoholics. In MMN studies of detoxified alcoholics, however, many confounding factors have to be taken into account. For instance, postwithdrawal brain hyperexcitability might be associated with a slightly enhanced or accelerated MMN/MMNm (the magnetic equivalent of MMN). In sum, MMN and MMNm provide an objective noninvasive tool for exploring the neurophysiological functional deficits related to both acute alcohol intoxication and chronic alcoholism.

Suppression of transient 40-Hz auditory response by haloperidol suggests modulation of human selective attention by dopamine D2 receptors

Cognitive processes including selective attention may depend on synchronous activity of neurons at the gamma-band (around 40Hz). To determine the effect of neuroleptic challenge on transient auditory evoked 40-Hz response, simultaneous measurement of 122-channel magnetoencephalogram (MEG) and 64-channel electroencephalogram (EEG) was used. Either 2mg of dopamine D(2)-receptor antagonist haloperidol or a placebo was administered orally to 11healthy subjects in a double-blind randomized crossover design in two separate sessions. The subjects attended to tones presented to one ear and ignored those presented to the other ear. Haloperidol significantly suppressed the transient 40-Hz electric response to the attended stimuli, while no significant effect was observed in the electric responses to the unattended tones or in the magnetic responses. The present result suggests that dopamine D(2) receptors modulate selective attention.

Global field power of auditory N1 correlates with impaired verbal-memory performance in human alcoholics

First weeks after alcohol withdrawal, associated with profound changes in neural transmission, constitute the critical period for relapse prevention and pharmacological intervention in alcoholism. Here, 20 male alcoholics with 1-6 weeks of abstinence and 20 age-matched healthy controls were studied using auditory event-related potentials (ERP), measured with a 32-channel electroencephalogram, and neuropsychological tests of auditory-verbal memory. Global field power maximum of ERP during 80-150 ms period after presentation of unattended tones (binaural 700 Hz pure tones, inter-stimulus interval 2.5 s) was significantly (P<0.01) larger in the alcoholics than controls. This effect, reflecting augmented N1 generation, significantly correlated (r=0.5) with impaired memory performance in the alcoholics. The profound change in pre-attentive auditory processing, predicting impaired memory performance, might reflect impaired cerebral inhibitory transmission in alcoholics.

Dose-dependent suppression by ethanol of transient auditory 40-Hz response

RATIONALE

Acute alcohol (ethanol) challenge is known to induce various cognitive disturbances, yet the neural basis of the effect is poorly known. The auditory transient evoked gamma-band (40-Hz) oscillatory responses have been suggested to be associated with various perceptual and cognitive functions in humans; however, alcohol effects on auditory 40-Hz responses have not been investigated to date.

OBJECTIVES

The objective of the study was to test the dose-related impact of alcohol on auditory transient evoked 40-Hz responses during a selective-attention task.

METHODS

Ten healthy social drinkers ingested, in four separate sessions, 0.00, 0. 25, 0.50, or 0.75 g/kg of 10% (v/v) alcohol solution. The order of the sessions was randomized and a double-blind procedure was employed. During a selective attention task, 300-Hz standard and 330-Hz deviant tones were presented to the left ear, and 1000-Hz standards and 1100-Hz deviants to the right ear of the subjects (P=0. 425 for each standard, P=0.075 for each deviant). The subjects attended to a designated ear, and were to detect the deviants therein while ignoring tones to the other ear.

RESULTS

The auditory transient evoked 40-Hz responses elicited by both the attended and unattended standard tones were significantly suppressed by the 0.50 and 0.75 g/kg alcohol doses.

CONCLUSIONS

Alcohol suppresses auditory transient evoked 40-Hz oscillations already with moderate blood alcohol concentrations. Given the putative role of gamma-band oscillations in cognition, this finding could be associated with certain alcohol-induced cognitive deficits.

Adenosine A1/A2a receptors mediate suppression of mismatch negativity by ethanol in humans

Acute alcohol challenge suppresses the mismatch negativity (MMN) component of the auditory event-related potential (ERP), however, the transmitter systems underlying MMN generation/mediating this effect have remained vague. To test adenosinergic contribution, 12 healthy social drinkers participated in four sessions, ingesting: (1) placebo pill and placebo beverage; (2) caffeine (100 mg) and placebo beverage; (3) placebo pill and alcohol (0.55 g/kg in 10% (v/v) solution); or (4) both caffeine and alcohol. ERP measured during a dichotic-listening task disclosed increased MMN and P3b peak latencies, and diminished amplitude of processing negativity (PN) with alcohol, however, only the increase in MMN peak latency was significantly antagonized by caffeine. The results suggest that A1 and A2a receptors play a role in the generation of, and mediate partly the suppressant effect of ethanol on, the MMN.

Scopolamine augments transient auditory 40-hz magnetic response in humans

The influence of neocortical muscarinic transmission on auditory-evoked 40-Hz magnetic response was studied in 13 healthy subjects in a double-blind randomized cross-over design. Either a centrally (scopolamine hydrobromide, 0.3 mg, i.v.) or a peripherally (glycopyrrolate, 0.2 mg, i.v.) acting antagonist of muscarinic transmission was administered during two sessions of magnetoencephalographic recording of 40-Hz response elicited by monaural tones. Scopolamine significantly (P < 0.01) augmented the 40-Hz magnetic response over the hemispheres ipsi- and contralateral to the ear stimulated. This finding suggests muscarinic modulation of the auditory evoked transient 40-Hz response.

Impaired preconscious auditory processing and cognitive functions in Alzheimer's disease

OBJECTIVE

To study whether preconscious auditory processing is deteriorated in patients with Alzheimer's disease (AD) having mild to moderate cognitive symptoms. To investigate whether auditory processing correlates with the impairment of the higher cortical functions.

METHODS

P50m and N100m responses elicited by a sequence of repetitive tones were recorded with a whole-head magnetometer from 22 patients with probable AD and from 18 healthy age-matched controls. In addition, an extensive neuropsychological test battery assessing main cognitive domains was administered to all subjects.

RESULTS

The patients with AD had significantly delayed N100m responses in the left hemisphere that correlated with the impairment of the language functions.

CONCLUSIONS

N100m auditory responses measured with magnetoencephalography may be useful in evaluating the severity and progression of the cortical dysfunction in dementia.

Suppression of mismatch negativity by backward masking predicts impaired working-memory performance in alcoholics

BACKGROUND

Pronounced disruption of memory traces by subsequent distractors may result in impaired behavioral memory performance in alcoholics.

METHODS

This hypothesis was investigated with an electrophysiological index of auditory sensory-memory traces, mismatch negativity, a preattentive event-related potential component elicited by a "deviant" tone within a train of "standard" tones.

RESULTS

Inserting a masking stimulus after these tones abolished mismatch negativity in alcoholics (DSM-IV) but not in social-drinker controls. This effect predicted working-memory impairment in alcoholics, and correlated significantly with self-reported alcohol consumption of the subjects. Furthermore, the backward-masking mismatch negativity paradigm detected sensory-memory impairment in 9 of 20 alcoholics (sensitivity 45%), whereas all 20 social drinkers were unimpaired (specificity 100%).

CONCLUSIONS

Vulnerability to memory trace disruption by shortly following sounds may be one of the factors contributing to behavioral memory dysfunction in alcoholics. The present result may provide an objective neurophysiological tool for investigation of alcohol-induced and other degenerative brain disorders.

Post-withdrawal changes in middle-latency auditory evoked potentials in abstinent human alcoholics

We investigated the effects of chronic alcoholism on middle-latency auditory evoked potentials (MAEP) in 14 male alcoholics with 1-6 weeks of abstinence (without other severe disorders) and 13 age-matched male social-drinker controls. The peak amplitude of a positive deflection (Pa) of the MAEP, peaking at about 30 ms post-stimulus, was significantly larger in the alcoholics than in the controls (P < 0.01), and notably, a significant negative correlation (r = -0.65) was observed between the Pa amplitude and duration of abstinence in the alcoholics. The present results suggest that the post-withdrawal brain hyperexcitability in the alcoholic brain, gradually recovering with abstinence, could be objectively and non-invasively studied with the MAEP.

Benzodiazepine temazepam suppresses the transient auditory 40-Hz response amplitude in humans

To discern the role of the GABA(A) receptors in the generation and attentive modulation of the transient auditory 40-Hz response, the effects of the benzodiazepine temazepam (10 mg) were studied in 10 healthy social drinkers, using a double-blind placebo-controlled design. Three hundred Hertz standard and 330 Hz rare deviant tones were presented to the left, and 1000 Hz standards and 1100 Hz deviants to the right ear of the subjects. Subjects attended to a designated ear and were to detect deviants therein while ignoring tones to the other. Temazepam significantly suppressed the amplitude of the 40-Hz response, the effect being equal for attended and non-attended tone responses. This suggests involvement of GABA(A) receptors in transient auditory 40-Hz response generation, however, not in the attentive modulation of the 40-Hz response.

Occurrence of sialic acids in healthy humans and different disorders

Sialic acid (SA), N-acetylated derivatives of neuraminic acid, play a central role in the biomedical functioning of humans. The normal range of total sialic acid (TSA) level in serum/plasma is 1.58-2.22 mmol L-1, the free form of SA only constituting 0.5-3 mumol L-1 and the lipid-associated (LSA) forms 10-50 mumol L-1. Notably, considerably higher amounts of free SA are found in urine than in serum/plasma (approximately 50% of the total SA). In inherited SA storage diseases such as Salla's disease, SA levels are elevated many times over, and their determination during clinical investigation is well established. Furthermore, a number of reports describe elevated SA levels in various other diseases, tentatively suggesting broader clinical utility for SA markers. Increased SA concentrations have been reported during inflammatory processes, probably resulting from increased levels of richly sialylated acute-phase glycoproteins. A connection between increased SA levels and elevated stroke and cardiovascular mortality risk has also been reported. In addition, SA levels are slightly increased in cancer, positively correlating with the degree of metastasis, as well as in alcohol abuse, diabetes, chronic renal failure and chronic glomerulonephritis. Several different mechanisms are assumed to underlie the elevated SA concentrations in these disorders. The apparent non-specificity of SA to a given disease limits the potential clinical usefulness of SA determination. In addition, some non-pathological factors, such as aging, pregnancy and smoking, may cause changes in SA concentrations. The absolute increases in SA levels are also rather small (save those in inherited SA storage disorders); this further limits the clinical potential of SA as a marker. Tentatively, SA markers might serve as adjuncts, when combined with other markers, in disease screening, disease progression follow-up, and in the monitoring of treatment response. To become clinically useful, however, the existing SA determination assays need to be considerably refined to reduce interferences, to be specific for certain SA forms, and to be more easy to use.

Temporal span of human echoic memory and mismatch negativity: revisited

The stimulus onset asynchrony (SOA)-related decrease in mismatch negativity (MMN) amplitude has been used to infer a putative auditory sensory memory duration of 4-10 s. However, both increased standard-to-standard (SSA) and standard-to-deviant (SDA) gaps could contribute to the effect. Fourteen subjects were presented with standard and deviant tones with short (0.35 s) and long (3.5 s) SOAs. In addition, the SSA and SDA were separately manipulated to test the relative contributions of slower rate of standard tone presentation and longer SDA gap to the SOA-related decrease in MMN amplitude. The MMN amplitude decreased with long SOA by 61%. Increases in SSA and SDA resulted in intermediate 47% and 31% decreases, these manipulations explaining 67% of the long SOA effect (p<0.001). Consequently, echoic memory length cannot be directly inferred from an MMN-SOA dependency function.

Decay of cortical pre-attentive sound discrimination in middle-age

Ageing effects on pre-attentive cortical detection of sound change, as indexed by magnetic mismatch negativity (MMNm), were disclosed with whole-head magnetoencephalography (MEG). Seventy healthy subjects (aged 17-82 years) were presented with a sequence of homogeneous standard tones and occasional deviants of shorter duration. The MMNm elicited by the shorter tones was diminished in amplitude (r = -0.42, p < 0.001) and increased in latency in the hemisphere ipsilateral to the ear stimulated (r = 0.38, p < 0.01), these effects being significant even in middle-aged subjects. The results suggest that pre-attentive comparison of incoming stimuli to a short-lived sensory memory trace in the central auditory system is impaired, and delayed in the ipsilateral hemisphere, already by the middle-age.

Scopolamine enhances middle-latency auditory evoked magnetic fields

To study the influence of central cholinergic muscarinic transmission on human cortical middle-latency auditory evoked magnetic fields (MAEF), centrally acting antagonist scopolamine hydrobromide (0.3 mg, i.v.), and peripheral muscarinic receptor antagonist glycopyrrolate (0.2 mg, i.v.), were administered to 13 healthy subjects in a double-blind randomized cross-over design. MAEF, measured with whole-head magnetoencephalography (MEG), were elicited with clicks applied at 10-Hz rate to the left ear. The amplitudes of N(b)m and P(a)m responses were augmented by scopolamine (P < 0.01 and P < 0.08). These effects were about equally strong for responses from ipsi- and contralateral auditory cortices. Thus, the present MEG findings revealed specific modulation of cortical generators of middle-latency auditory evoked responses by muscarinic transmission. These findings might be associated with auditory processing deficits observed in dementias with cholinergic disturbances.

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.

Combined mapping of human auditory EEG and MEG responses

Auditory electric and magnetic P50(m), N1(m) and MMN(m) responses to standard, deviant and novel sounds were studied by recording brain electrical activity with 25 EEG electrodes simultaneously with the corresponding magnetic signals measured with 122 MEG gradiometer coils. The sources of these responses were located on the basis of the MEG responses; all were found to be in the supratemporal plane. The goal of the present paper was to investigate to what degree the source locations and orientations determined from the magnetic data account for the measured EEG signals. It was found that the electric P50, N1 and MMN responses can to a considerable degree be explained by the sources of the corresponding magnetic responses. In addition, source-current components not detectable by MEG were shown to contribute to the measured EEG signals.

Selective acceleration of auditory processing in chronic alcoholics during abstinence

Simultaneous auditory processing between the hemispheres was studied with a whole-head magnetometer in 13 abstinent chronic alcoholics and 10 healthy control subjects. Auditory stimuli were presented monaurally with interstimulus intervals of 0.5 and 2.5 sec in different blocks. The N100m response, which contributes to stimulus detection, was significantly accelerated in the hemisphere ipsilateral to the ear stimulated in abstinent alcoholics. The MMNm response reflecting automatic stimulus-change detection peaked earlier in alcoholics, and the ipsilateral N100m latency correlated significantly with the abstinence duration. These results suggest that auditory processing is accelerated in the auditory cortex ipsilateral to the stimulated ear in chronic abstinent alcoholics and that the accelerated processing is at least partly reversible. This may be caused by the hyperexcitation in the brain related to the ethanol withdrawal.

Reversal of cerebral asymmetry in schizophrenia measured with magnetoencephalography

It has been suggested that schizophrenic patients fail to develop left-hemisphere dominance because of an early disturbance in neuronal development. This hypothesis has been supported by some post-mortem. CT and magnetic resonance imaging (MRI) studies, while other in-vivo studies have given contradicting results. We used 122-channel whole-head magnetoencephalography and MRI to locate the sources of auditory evoked responses in 19 schizophrenic patients and in 20 healthy controls. Auditory evoked responses were detected in all subjects. The left-right hemisphere asymmetry of cerebral sources for auditory evoked responses was markedly dispersed among patients when compared with controls. The source locations for left auditory cortex were clearly anterior with respect to the right hemisphere in 32% of the patients, while the corresponding prevalence of this abnormal asymmetry was 0% in controls (p = 0.008. Fisher's exact test). The reversed asymmetry appeared to be associated with a shorter anterior-posterior distance between the auditory cortex and the anterior tip of the temporal lobe in the left side when compared with the right side. The reversed asymmetry was associated with higher PANSS general psychopathological score, and especially with higher guilt feelings and motor retardation scores. The large 2.5-fold standard deviation in the inter-hemispheric anterior posterior difference in the location of the auditory cortex among patients (p 0.001 for the difference in the magnitude of variance between controls and patients) clearly reflects the dispersion of the left right asymmetry into both direction, and three of the patients with 'normal asymmetry' had a greater left-right asymmetry than any of the controls. Markedly greater reversal of hemispheric asymmetry among patients implies that regulation of the development of brain asymmetry is disturbed among schizophrenic patients. Abnormality in the cerebral asymmetry may be a crucial factor in the development of schizophrenic disorder in a substantial proportion of patients. The results suggest that the reversed asymmetry is associated with the higher severity of general psychopathological symptoms.

Processing of novel sounds and frequency changes in the human auditory cortex: magnetoencephalographic recordings

Whole-head magnetoencephalographic (MEG) responses to repeating standard tones and to infrequent slightly higher deviant tones and complex novel sounds were recorded together with event-related brain potentials (ERPs). Deviant tones and novel sounds elicited the mismatch negativity (MMN) component of the ERP and its MEG counterpart (MMNm) both when the auditory stimuli were attended to and when they were ignored. MMNm generators were located bilateral to the superior planes of the temporal lobes where preattentive auditory discrimination appears to occur. A subsequent positive P3a component was elicited by deviant tones and with a larger amplitude by novel sounds even when the sounds were to be ignored. Source localization for the MEG counterpart of P3a (P3am) suggested that the auditory cortex in the superior temporal plane is involved in the neural network of involuntary attention switching to changes in the acoustic environment.

Effects of naltrexone and ethanol on auditory event-related brain potentials

Acute effects of ethanol (0.55 g/kg) and the opioid antagonist naltrexone (50 mg) on auditory event-related brain potentials (ERP) (i.e., electrical brain activity time-locked to sensory stimuli) were investigated in 13 healthy social drinkers, using a double-blind, placebo-controlled, design. The subjects' task was to attend to tones presented to a designated ear while ignoring tones to the other, and to detect deviant tones among the attended tones. When administered alone, naltrexone significantly reduced the amplitude of the later part of negative difference (Nd[l]), suggesting impaired selective attention. However, this effect might have been caused by naltrexone-induced nausea. Ethanol, when ingested alone, attenuated the amplitude of the N1, and increased the peak latencies of the mismatch negativity (MMN) and N2b that have been suggested to reflect automatic change detection in audition and allocation of attentional resources to processing of stimulus deviance, respectively. In contrast, the P1 amplitude was augmented by alcohol, but only when the tones were attended. When ethanol and naltrexone were simultaneously ingested, however, the alcohol-induced P1 amplitude augmentation was canceled, thus tentatively suggesting opioidergic mediation of this alcohol effect. In contrast, the MMN peak latency was increased significantly more in the interaction condition than in the ethanol condition, thus suggesting that the detrimental effects of alcohol on involuntary attention switching were augmented by naltrexone. Furthermore, the N2b amplitude was significantly suppressed in the interaction condition, suggesting attentional impairment.

Mismatch negativity subcomponents and ethyl alcohol

Effects of ethanol (0.55 and 0.85 g/kg) on event-related potentials were investigated by presenting 50-ms standard and 25-ms deviant pure tones to 9 social drinkers during a reading task, in a single-blind, placebo-controlled paradigm. Whereas the lower ethanol dose had no impact on ERPs with an 0.8-s inter-stimulus interval (ISI), it attenuated the N1, P2, and mismatch negativity (MMN) amplitudes with a longer ISI of 2.4 s. The higher alcohol dose increased the N1 peak latency with both ISIs. It also suppressed the N1 and MMN amplitudes with the longer ISI. The MMN suppression did not, however, occur at scalp sites below the Sylvian fissure, thus suggesting that ethanol affected only the frontal MMN subgenerator. Moreover, the different dose responses of the N1, P2, and MMN (subcomponents) to ethanol may indicate that the neurotransmitter systems underlying their generation are, to some extent, different.

Effects of ethanol and auditory distraction on forced choice reaction time

Effects of ethanol (0.55 g/kg) and auditory distraction on visual forced choice reaction time (RT) were investigated in 10 healthy social drinkers, using a single-blind, placebo-controlled, crossover design. Subjects were to respond by pressing a button either with their right-hand index or middle finger, depending on whether an odd or an even digit was presented on a PC screen. In control blocks, the digits were presented alone, whereas in distraction blocks they were shortly preceded by either a frequent "standard" tone of 600 Hz, or an infrequent tone that was either a 660 Hz "deviant" tone or a "novel" sound (e.g., telephone ringing). Alcohol reduced the hit rate by increasing the amount of errors, but had no effect on the RT, thus supporting the previous observations. In the placebo condition, the RT was prolonged by the deviant and novel sounds, and the hit rate was reduced by the deviant tones. During ethanol intoxication, however, the reduction in hit rate caused by the deviant tones was significantly smaller. This suggests that the attention-capturing effects of the deviant sounds were suppressed by ethanol, thus demonstrating a detrimental effect of ethanol on involuntary attention.

Dose-related effect of alcohol on mismatch negativity and reaction time performance

In a recent study, the mismatch negativity (MMN) component of auditory event-related potential, elicited by occasional frequency changes in a repetitive tone, was strongly attenuated by a low dosage of alcohol. We investigated the phenomenon in nine subjects with two different dosages of ethanol (0.35 and 0.55 g/kg), and with two magnitudes of frequency changes (5% and 10%), in a single-blind, placebo-controlled paradigm. Ethanol had no observable effect on the N1 and P2 deflections, nor on the reaction time to frequency changes measured in a separate session. However, the MMN was attenuated after administration of the larger dosage of alcohol, suggesting impaired preconscious processing of stimulus features outside the scope of attention. The results support the view according to which the automatic functions of human information processing are more sensitive than the controlled functions to the detrimental effects of alcohol. The fact that the MMN suppression was stronger when stimulus deviation was smaller indicates that at relatively low blood alcohol concentrations the detection of small deviations is especially hampered.

Low dose of ethanol suppresses mismatch negativity of auditory event-related potentials

The acute effect of a low dose of ethanol (0.5 g/kg) on attention and auditory event-related potentials (ERPs) was investigated in 10 social drinkers using a single-blind, placebo-controlled cross-over design. A dichotic listening task, in which the subjects were instructed to attend selectively to stimuli to one ear while ignoring stimuli to the other, was used. The amplitudes of N1, P2, and the mismatch negativity (MMN) were significantly diminished by alcohol. The latencies of the MMN and N2b were also significantly increased after alcohol ingestion. The novel finding of the significant (> 60% reduction in amplitude) suppression of the MMN can be interpreted as indicating disturbed preconscious detection of acoustic changes outside the scope of attention. Because this is a prerequisite to an attentional shift, the MMN suppression may be related to increased risk for accidents after alcohol ingestion. The same dose of alcohol that suppressed the MMN left intact selective attention and conscious "target" detection, as reflected by the processing negativity and P3 deflections, thus suggesting that the automatic functions of human information processing are more sensitive to alcohol than the controlled, attentional functions.