Neurophysiological markers of novelty processing are modulated by COMT and DRD4 genotypes

Prevalence of Common Alleles of Some Stress Resilience Genes among Adolescents Born in Different Periods Relative to the Socioeconomic Crisis of the 1990s in Russia

Social stress is common among people and is considered one of the causes of the declining birth rate. Predisposition to stress and stress-induced disorders is largely determined genetically. We hypothesized that due to differences in stress resistance, carriers of different genetic variants of genes associated with stress resilience and stress-induced diseases may have dissimilar numbers of offspring under conditions of long-term social stress. To test this hypothesis, a comparative analysis of frequencies of seven common polymorphic regions [exon 3 variable number of tandem repeats (VNTR) of the DRD4 gene, rs4680 of COMT, STin2 VNTR and the 5-HTTLPR (rs774676466) insertion/deletion polymorphism of SLC6A4, rs4570625 of TPH2, rs6265 of BDNF, and rs258747 of NR3C1] was performed on standardized groups of randomly selected adolescents born before, during, and after severe socioeconomic deprivation (the crisis of the 1990s in Russia). There were significant differences in frequencies of "long" alleles of the DRD4 gene (p = 0.020, χ² = 5.492) and rs4680 (p = 0.022, χ² = 5.289) in the "crisis" group as compared to the combined "noncrisis" population. It is possible that the dopaminergic system had an impact on the successful adaptation of a person to social stress.

Brain predictive coding processes are associated to COMT gene Val158Met polymorphism

Predicting events in the ever-changing environment is a fundamental survival function intrinsic to the physiology of sensory systems, whose efficiency varies among the population. Even though it is established that a major source of such variations is genetic heritage, there are no studies tracking down auditory predicting processes to genetic mutations. Thus, we examined the neurophysiological responses to deviant stimuli recorded with magnetoencephalography (MEG) in 108 healthy participants carrying different variants of Val158Met single-nucleotide polymorphism (SNP) within the catechol-O-methyltransferase (COMT) gene, responsible for the majority of catecholamines degradation in the prefrontal cortex. Our results showed significant amplitude enhancement of prediction error responses originating from the inferior frontal gyrus, superior and middle temporal cortices in heterozygous genotype carriers (Val/Met) vs homozygous (Val/Val and Met/Met) carriers. Integrating neurophysiology and genetics, this study shows how the neural mechanisms underlying optimal deviant detection vary according to the gene-determined cathecolamine levels in the brain.

Neurophysiological correlates of purchase decision-making

Economic decisions are characterized by their uncertainty and the lack of explicit feedback that indicates the correctness of decisions at the time they are made. Nevertheless, very little is known about the neural mechanisms involved in this process. Our study sought to identify the neurophysiological correlates of purchase decision-making in situations where the optimal purchase time is not known. EEG was recorded in 24 healthy subjects while they were performing a new experimental paradigm that simulates real economic decisions. At the time of price presentation, we found an increase in the P3 Event-Related Potential and induced theta and alpha oscillatory activity when participants chose to buy compared to when they decided to wait for a better price. These results reflect the engagement of attention and executive function in purchase decision-making and might help in the understanding of brain mechanisms underlying economic decisions in uncertain scenarios.

Neurophysiological correlates of abnormal auditory processing in episodic migraine during the interictal period

BACKGROUND

The characteristics of the hypersensitivity to auditory stimuli during the interictal period in episodic migraine are discussed. The combined use of event-related potentials, time-frequency power and phase-synchronization can provide relevant information about the time-course of sensory-attentional processing in migraine and its underlying mechanisms.

OBJECTIVE

The aim of this nested case-control study was to examine these processes in young, female, episodic migraine patients interictally and compare them to controls using an active auditory oddball task.

METHOD

We recorded, using 20 channels, the electrophysiological brain activity of 21 women with episodic migraine without aura and 21 healthy matched controls without family history of migraine, during a novelty oddball paradigm. We collected sociodemographic and clinical data as well as scores related to disability, quality of life, anxiety and depression. We calculated behavioural measures including reaction times, hit rates and false alarms. Spectral power and phase-synchronization of oscillatory activity as well as event-related potentials were obtained for standard stimuli. For target and novel stimuli, event-related potentials were acquired.

RESULTS

There were no significant differences at the behavioural level. In migraine patients, we found an increased phase-synchronization at the theta frequency range and a higher N1 response to standard trials. No differences were observed in spectral power. No evidence for a lack of habituation in any of the measures was seen between migraine patients and controls. The Reorienting Negativity was reduced in migraine patients as compared to controls on novel but not on target trials.

CONCLUSION

Our findings suggest that migraine patients process stimuli as more salient, seem to allocate more of their attentional resources to their surrounding environment, and have less available resources to reorient attention back to the main task.

Auditory Dysfunction in Parkinson's Disease

PD is a progressive and complex neurological disorder with heterogeneous symptomatology. PD is characterized by classical motor features of parkinsonism and nonmotor symptoms and involves extensive regions of the nervous system, various neurotransmitters, and protein aggregates. Extensive evidence supports auditory dysfunction as an additional nonmotor feature of PD. Studies indicate a broad range of auditory impairments in PD, from the peripheral hearing system to the auditory brainstem and cortical areas. For instance, research demonstrates a higher occurrence of hearing loss in early-onset PD and evidence of abnormal auditory evoked potentials, event-related potentials, and habituation to novel stimuli. Electrophysiological data, such as auditory P3a, also is suggested as a sensitive measure of illness duration and severity. Improvement in auditory responses following dopaminergic therapies also indicates the presence of similar neurotransmitters (i.e., glutamate and dopamine) in the auditory system and basal ganglia. Nonetheless, hearing impairments in PD have received little attention in clinical practice so far. This review summarizes evidence of peripheral and central auditory impairments in PD and provides conclusions and directions for future empirical and clinical research. © 2020 International Parkinson and Movement Disorder Society.

Effects of Transcutaneous Vagus Nerve Stimulation (tVNS) on the P300 and Alpha-Amylase Level: A Pilot Study

Recent research suggests that the P3b may be closely related to the activation of the locus coeruleus-norepinephrine (LC-NE) system. To further study the potential association, we applied a novel technique, the non-invasive transcutaneous vagus nerve stimulation (tVNS), which is speculated to increase noradrenaline levels. Using a within-subject cross-over design, 20 healthy participants received continuous tVNS and sham stimulation on two consecutive days (stimulation counterbalanced across participants) while performing a visual oddball task. During stimulation, oval non-targets (standard), normal-head (easy) and rotated-head (difficult) targets, as well as novel stimuli (scenes) were presented. As an indirect marker of noradrenergic activation we also collected salivary alpha-amylase (sAA) before and after stimulation. Results showed larger P3b amplitudes for target, relative to standard stimuli, irrespective of stimulation condition. Exploratory post hoc analyses, however, revealed that, in comparison to standard stimuli, easy (but not difficult) targets produced larger P3b (but not P3a) amplitudes during active tVNS, compared to sham stimulation. For sAA levels, although main analyses did not show differential effects of stimulation, direct testing revealed that tVNS (but not sham stimulation) increased sAA levels after stimulation. Additionally, larger differences between tVNS and sham stimulation in P3b magnitudes for easy targets were associated with larger increase in sAA levels after tVNS, but not after sham stimulation. Despite preliminary evidence for a modulatory influence of tVNS on the P3b, which may be partly mediated by activation of the noradrenergic system, additional research in this field is clearly warranted. Future studies need to clarify whether tVNS also facilitates other processes, such as learning and memory, and whether tVNS can be used as therapeutic tool.

Brain oscillations reveal impaired novelty detection from early stages of Parkinson's disease

The identification of reliable biomarkers for early diagnosis and progression tracking of neurodegenerative diseases has become an important objective in clinical neuroscience in the last years. The P3a event-related potential, considered as the neurophysiological hallmark of novelty detection, has been shown to be reduced in Parkinson's disease (PD) and proposed as a sensitive measure for illness duration and severity. Our aim for this study was to explore for the first time whether impaired novelty detection could be observed through phase- and time-locked brain oscillatory activity at early PD. Twenty-seven patients with idiopathic PD at early stages (disease duration <5 years and Hoehn and Yahr stage <3) were included. A healthy control group (n = 24) was included as well. All participants performed an auditory involuntary attention task including frequent and deviant tones while a digital EEG was obtained. A neuropsychological battery was administered as well. Time-frequency representations of power and phase-locked oscillations and P3a amplitudes were compared between groups. We found a significant reduction of power and phase locking of slow oscillations (3-7 Hz) for deviant tones in the PD group compared to controls in the P3a time range (300-550 ms). Also, reduced modulation of late induced (not phase locked) alpha-beta oscillations (400-650 ms, 8-25 Hz) was observed in the PD group after deviant tones onset. The P3a amplitude was predicted by years of evolution in the PD group. Finally, while phase-locked slow oscillations were associated with task behavioral distraction effects, induced alpha-beta activity was related to cognitive flexibility performance. Our results show that novelty detection impairment can be identified in neurophysiological terms from very early stages of PD, and such impairment increases linearly as the disease progresses. Also, induced alpha-beta oscillations underlying novelty detection are related to executive functioning.

Event-related potentials reflect impaired temporal interval learning following haloperidol administration

BACKGROUND

Signals carried by the mesencephalic dopamine system and conveyed to anterior cingulate cortex are critically implicated in probabilistic reward learning and performance monitoring. A common evaluative mechanism purportedly subserves both functions, giving rise to homologous medial frontal negativities in feedback- and response-locked event-related brain potentials (the feedback-related negativity (FRN) and the error-related negativity (ERN), respectively), reflecting dopamine-dependent prediction error signals to unexpectedly negative events. Consistent with this model, the dopamine receptor antagonist, haloperidol, attenuates the ERN, but effects on FRN have not yet been evaluated.

METHODS

ERN and FRN were recorded during a temporal interval learning task (TILT) following randomized, double-blind administration of haloperidol (3 mg; n = 18), diphenhydramine (an active control for haloperidol; 25 mg; n = 20), or placebo (n = 21) to healthy controls. Centroparietal positivities, the Pe and feedback-locked P300, were also measured and correlations between ERP measures and behavioral indices of learning, overall accuracy, and post-error compensatory behavior were evaluated. We hypothesized that haloperidol would reduce ERN and FRN, but that ERN would uniquely track automatic, error-related performance adjustments, while FRN would be associated with learning and overall accuracy.

RESULTS

As predicted, ERN was reduced by haloperidol and in those exhibiting less adaptive post-error performance; however, these effects were limited to ERNs following fast timing errors. In contrast, the FRN was not affected by drug condition, although increased FRN amplitude was associated with improved accuracy. Significant drug effects on centroparietal positivities were also absent.

CONCLUSIONS

Our results support a functional and neurobiological dissociation between the ERN and FRN.

Auditory Target and Novelty Processing in Patients with Unilateral Hippocampal Sclerosis: A Current-Source Density Study

The capacity to respond to novel events is crucial for adapting to the constantly changing environment. Here, we recorded 29-channel Event Related Brain Potentials (ERPs) during an active auditory novelty oddball paradigm and used for the first time Current Source Density-transformed Event Related Brain Potentials and associated time-frequency spectra to study target and novelty processing in a group of epileptic patients with unilateral damage of the hippocampus (N = 18) and in healthy matched control participants (N = 18). Importantly, we used Voxel-Based Morphometry to ensure that our group of patients had a focal unilateral damage restricted to the hippocampus and especially its medial part. We found a clear deficit for target processing at the behavioral level. In addition, compared to controls, our group of patients presented (i) a reduction of theta event-related synchronization (ERS) for targets and (ii) a reduction and delayed P3a source accompanied by reduced theta and low-beta ERS and alpha event-related synchronization (ERD) for novel stimuli. These results suggest that the integrity of the hippocampus might be crucial for the functioning of the complex cortico-subcortical network involved in the detection of novel and target stimuli.

Electrophysiological, cognitive and clinical profiles of at-risk mental state: The longitudinal Minds in Transition (MinT) study

The onset of schizophrenia is typically preceded by a prodromal period lasting several years during which sub-threshold symptoms may be identified retrospectively. Clinical interviews are currently used to identify individuals who have an ultra-high risk (UHR) of developing a psychotic illness with a view to provision of interventions that prevent, delay or reduce severity of future mental health issues. The utility of bio-markers as an adjunct in the identification of UHR individuals is not yet established. Several event-related potential measures, especially mismatch-negativity (MMN), have been identified as potential biomarkers for schizophrenia. In this 12-month longitudinal study, demographic, clinical and neuropsychological data were acquired from 102 anti-psychotic naive UHR and 61 healthy controls, of whom 80 UHR and 58 controls provided valid EEG data during a passive auditory task at baseline. Despite widespread differences between UHR and controls on demographic, clinical and neuropsychological measures, MMN and P3a did not differ between these groups. Of 67 UHR at the 12-month follow-up, 7 (10%) had transitioned to a psychotic illness. The statistical power to detect differences between those who did or did not transition was limited by the lower than expected transition rate. ERPs did not predict transition, with trends in the opposite direction to that predicted. In exploratory analysis, the strongest predictors of transition were measures of verbal memory and subjective emotional disturbance.

Attentional dysfunction in abstinent long-term cannabis users with and without schizophrenia

Long-term cannabis use may confer cognitive deficits and increased risk of psychosis. However, the relationship between cannabis use and schizophrenia is complex. In particular, little is known about the effects of chronic cannabis use on the attention-related electric brain response in schizophrenia. We investigated auditory novelty and oddball P300 evoked potentials in a mixed sample of first-episode and chronic schizophrenic patients and healthy controls with (SZCA, n = 20; COCA, n = 20, abstinence ≥28 days) or without (SZ, n = 20; CO, n = 20) chronic cannabis use. Duration of regular cannabis use was 8.3 ± 5.6 (SZCA) and 9.1 ± 7.1 (COCA) years. In general, schizophrenic patients showed reduced P300 amplitudes. Cannabis use was associated with both a reduced early and late left-hemispheric novelty P300. There was a significant 'diagnosis × cannabis' interaction for the left-hemispheric late novelty P300 in that cannabis use was associated with a reduced amplitude in the otherwise healthy but not in the schizophrenic group compared with their relative control groups (corrected p < 0.02; p > 0.9, respectively). The left-hemispheric late novelty P300 in the otherwise healthy cannabis group correlated inversely with amount and duration of cannabis use (r = -0.50, p = 0.024; r = -0.57, p = 0.009, respectively). Our study confirms attentional deficits with chronic cannabis use. However, cannabis use may lead to different cognitive sequelae in patients with schizophrenia and in healthy controls, possibly reflecting preexisting alterations in the endocannabinoid system in schizophrenia.

Reward Sensitivity of ACC as an Intermediate Phenotype between DRD4-521T and Substance Misuse

The development and expression of the midbrain dopamine system is determined in part by genetic factors that vary across individuals such that dopamine-related genes are partly responsible for addiction vulnerability. However, a complete account of how dopamine-related genes predispose individuals to drug addiction remains to be developed. Adopting an intermediate phenotype approach, we investigated whether reward-related electrophysiological activity of ACC—a cortical region said to utilize dopamine reward signals to learn the value of extended, context-specific sequences of goal-directed behaviors—mediates the influence of multiple dopamine-related functional polymorphisms over substance use. We used structural equation modeling to examine whether two related electrophysiological phenomena associated with the control and reinforcement learning functions of ACC—theta power and the reward positivity—mediated the relationship between the degree of substance misuse and genetic polymorphisms that regulate dopamine processing in frontal cortex. Substance use data were collected from 812 undergraduate students. One hundred ninety-six returned on a subsequent day to participate in an electrophysiological experiment and to provide saliva samples for DNA analysis. We found that these electrophysiological signals mediated a relationship between the DRD4-521T dopamine receptor genotype and substance misuse. Our results provide a theoretical framework that bridges the gap between genes and behavior in drug addiction and illustrate how future interventions might be individually tailored for specific genetic and neurocognitive profiles.

The effects of methylphenidate on cerebral responses to conflict anticipation and unsigned prediction error in a stop-signal task

To adapt flexibly to a rapidly changing environment, humans must anticipate conflict and respond to surprising, unexpected events. To this end, the brain estimates upcoming conflict on the basis of prior experience and computes unsigned prediction error (UPE). Although much work implicates catecholamines in cognitive control, little is known about how pharmacological manipulation of catecholamines affects the neural processes underlying conflict anticipation and UPE computation. We addressed this issue by imaging 24 healthy young adults who received a 45 mg oral dose of methylphenidate (MPH) and 62 matched controls who did not receive MPH prior to performing the stop-signal task. We used a Bayesian Dynamic Belief Model to make trial-by-trial estimates of conflict and UPE during task performance. Replicating previous research, the control group showed anticipation-related activation in the presupplementary motor area and deactivation in the ventromedial prefrontal cortex and parahippocampal gyrus, as well as UPE-related activations in the dorsal anterior cingulate, insula, and inferior parietal lobule. In group comparison, MPH increased anticipation activity in the bilateral caudate head and decreased UPE activity in each of the aforementioned regions. These findings highlight distinct effects of catecholamines on the neural mechanisms underlying conflict anticipation and UPE, signals critical to learning and adaptive behavior.

Neurotransmitters and Novelty: A Systematic Review

Our brains are highly responsive to novelty. However, how novelty is processed in the brain, and what neurotransmitter systems play a role therein, remains elusive. Here, we systematically review studies on human participants that have looked at the neuromodulatory basis of novelty detection and processing. While theoretical models and studies on nonhuman animals have pointed to a role of the dopaminergic, cholinergic, noradrenergic and serotonergic systems, the human literature has focused almost exclusively on the first two. Dopamine was found to affect electrophysiological responses to novelty early in time after stimulus presentation, but evidence on its effects on later processing was found to be contradictory: While neuropharmacological studies mostly yielded null effects, gene studies did point to an important role for dopamine. Acetylcholine seems to dampen novelty signals in the medial temporal lobe, but boost them in frontal cortex. Findings on 5-HT (serotonin) were found to be mostly contradictory. Two large gaps were identified in the literature. First, few studies have looked at neuromodulatory influences on behavioral effects of novelty. Second, no study has looked at the involvement of the noradrenergic system in novelty processing.

Neurophysiological Evidence of Compensatory Brain Mechanisms in Early-Stage Multiple Sclerosis

Multiple sclerosis (MS) is a chronic central nervous system disorder characterized by white matter inflammation, demyelination and neurodegeneration. Although cognitive dysfunction is a common manifestation, it may go unnoticed in recently-diagnosed patients. Prior studies suggest MS patients develop compensatory mechanisms potentially involving enhanced performance monitoring. Here we assessed the performance monitoring system in early-stage MS patients using the error-related negativity (ERN), an event-related brain potential (ERP) observed following behavioral errors. Twenty-seven early-stage MS patients and 31 controls were neuropsychologically assessed. Electroencephalography recordings were obtained while participants performed: a) a stop task and b) an auditory oddball task. Behavior and ERP measures were assessed. No differences in performance were found between groups in most neuropsychological tests or in behavior or ERP components in the auditory oddball task. However, the amplitude of the ERN associated with stop errors in the stop task was significantly higher in patients. ERN amplitude correlated positively with scores on the Expanded Disability Status Scale and the Multiple Sclerosis Severity Score, and negatively with the time since last relapse. Patients showed higher neuronal recruitment in tasks involving performance monitoring. Results suggest the development of compensatory brain mechanisms in early-stage MS and reflect the sensitivity of the ERN to detect these changes.

Genetic psychophysiology: advances, problems, and future directions

This paper presents an overview of historical advances and the current state of genetic psychophysiology, a rapidly developing interdisciplinary research linking genetics, brain, and human behavior, discusses methodological problems, and outlines future directions of research. The main goals of genetic psychophysiology are to elucidate the neural pathways and mechanisms mediating genetic influences on cognition and emotion, identify intermediate brain-based phenotypes for psychopathology, and provide a functional characterization of genes being discovered by large association studies of behavioral phenotypes. Since the initiation of this neurogenetic approach to human individual differences in the 1970s, numerous twin and family studies have provided strong evidence for heritability of diverse aspects of brain function including resting-state brain oscillations, functional connectivity, and event-related neural activity in a variety of cognitive and emotion processing tasks, as well as peripheral psychophysiological responses. These data indicate large differences in the presence and strength of genetic influences across measures and domains, permitting the selection of heritable characteristics for gene finding studies. More recently, candidate gene association studies began to implicate specific genetic variants in different aspects of neurocognition. However, great caution is needed in pursuing this line of research due to its demonstrated proneness to generate false-positive findings. Recent developments in methods for physiological signal analysis, hemodynamic imaging, and genomic technologies offer new exciting opportunities for the investigation of the interplay between genetic and environmental factors in the development of individual differences in behavior, both normal and abnormal.

Prefrontal transcranial direct current stimulation alters activation and connectivity in cortical and subcortical reward systems: a tDCS-fMRI study

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique used both experimentally and therapeutically to modulate regional brain function. However, few studies have directly measured the aftereffects of tDCS on brain activity or examined changes in task-related brain activity consequent to prefrontal tDCS. To investigate the neural effects of tDCS, we collected fMRI data from 22 human subjects, both at rest and while performing the Balloon Analog Risk Task (BART), before and after true or sham transcranial direct current stimulation. TDCS decreased resting blood perfusion in orbitofrontal cortex and the right caudate and increased task-related activity in the right dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) in response to losses but not wins or increasing risk. Network analysis showed that whole-brain connectivity of the right ACC correlated positively with the number of pumps subjects were willing to make on the BART, and that tDCS reduced connectivity between the right ACC and the rest of the brain. Whole-brain connectivity of the right DLPFC also correlated negatively with pumps on the BART, as prior literature would suggest. Our results suggest that tDCS can alter activation and connectivity in regions distal to the electrodes.

Contributions of COMT Val¹⁵⁸ Met to cognitive stability and flexibility in infancy

Adaptive behavior requires focusing on relevant tasks while remaining sensitive to novel information. In adult studies of cognitive control, cognitive stability involves maintaining robust cognitive representations while cognitive flexibility involves updating of representations in response to novel information. Previous adult research has shown that the Met allele of the COMT Val(158) Met gene is associated with enhanced cognitive stability whereas the Val allele is associated with enhanced cognitive flexibility. Here we propose that the stability/flexibility framework can also be applied to infant research, with stability mapping onto early indices of behavioral regulation and flexibility mapping onto indices of behavioral reactivity. From this perspective, the present study examined whether COMT genotype was related to 7-month-old infants' reactivity to novel stimuli and behavioral regulation. Cognitive stability and flexibility were assessed using (1) a motor approach task, (2) a habituation task, and (3) a parental-report measure of temperament. Val carriers were faster to reach for novel toys during the motor approach task and received higher scores on the temperament measure of approach to novelty. Met carriers showed enhanced dishabituation to the novel stimulus during the habituation task and received higher scores on the temperament measures of sustained attention and behavioral regulation. Overall, these results are consistent with adult research suggesting that the Met and Val alleles are associated with increased cognitive stability and flexibility, respectively, and thus suggest that COMT genotype may similarly affect cognitive function in infancy.

Family history of psychosis moderates early auditory cortical response abnormalities in non-psychotic bipolar disorder

OBJECTIVES

Bipolar I disorder is a disabling illness affecting 1% of people worldwide. Family and twin studies suggest that psychotic bipolar disorder (BDP) represents a homogeneous subgroup with an etiology distinct from non-psychotic bipolar disorder (BDNP) and partially shared with schizophrenia. Studies of auditory electrophysiology [e.g., paired-stimulus and oddball measured with electroencephalography (EEG)] consistently report deviations in psychotic groups (schizophrenia, BDP), yet such studies comparing BDP and BDNP are sparse and, in some cases, conflicting. Auditory EEG responses are significantly reduced in unaffected relatives of psychosis patients, suggesting that they may relate to both psychosis liability and expression.

METHODS

While 64-sensor EEGs were recorded, age- and gender-matched samples of 70 BDP, 35 BDNP {20 with a family history of psychosis [BDNP(+)]}, and 70 psychiatrically healthy subjects were presented with typical auditory paired-stimuli and auditory oddball paradigms.

RESULTS

Oddball P3b reductions were present and indistinguishable across all patient groups. P2s to paired stimuli were abnormal only in BDP and BDNP(+). Conversely, N1 reductions to stimuli in both paradigms and P3a reductions were present in both BDP and BDNP(-) groups but were absent in BDNP(+).

CONCLUSIONS

Although nearly all auditory neural response components studied were abnormal in BDP, BDNP abnormalities at early- and mid-latencies were moderated by family psychosis history. The relationship between psychosis expression, heritable psychosis risk, and neurophysiology within bipolar disorder, therefore, may be complex. Consideration of such clinical disease heterogeneity may be important for future investigations of the pathophysiology of major psychiatric disturbance.

Reduced P3a amplitudes in antipsychotic naïve first-episode psychosis patients and individuals at clinical high-risk for psychosis

Event related potentials (ERP) associated with early sensory information processing have been proposed as possible vulnerability markers for psychosis. Compared to other ERPs reported in schizophrenia research, like Mismatch Negativity (MMN), little is known about P3a, an ERP related to novelty detection. The aim of this study was to analyze the MMN-P3a complex in 20 antipsychotic naïve first-episode psychosis patients (FEP), 23 antipsychotic naïve individuals at clinical high-risk for psychosis (CHR) and 24 healthy controls. The MMN-P3a amplitudes and latencies were obtained during a passive auditory mismatch frequency deviant ERP paradigm and analyzed in frontal and central scalp regions. There were no significant differences in MMN amplitude between groups. There was a significant group difference in P3a due to reduced amplitude (F[2,64] = 3.7, p = 0.03) in both CHR and FEP groups (Mean difference (MD) = 0.39, p = 0.04 and MD = 0.49, p = 0.02, respectively) compared to the control group and this effect was most prominent on the right side (Group × laterality effect: MD = 0.57, p < 0.01 and MD = 0.58, p < 0.01, respectively). No significant differences were observed for MMN or P3a latencies between groups. Although a P3a decrement in chronic schizophrenia and FEP has been previously reported, our results suggest that this novelty detection impairment is present even in pre-psychosis stages in antipsychotic naïve subjects. This study supports the evidence that P3a could represent a neurophysiological vulnerability marker for the development of psychosis.

Genetic polymorphisms of the dopamine and serotonin systems modulate the neurophysiological response to feedback and risk taking in healthy humans

Genetic differences in the dopamine and serotonin systems have been suggested as potential factors underlying interindividual variability in risk taking and in brain activation during the processing of feedback. Here, we studied the effects of dopaminergic (dopamine transporter [DAT1], catecholamine-O-methyltransferase val158met [COMT]) and serotonergic (serotonin transporter [5HTTLPR]) polymorphisms on risk taking and brain responses following feedback in 60 healthy female subjects. The subjects completed a well-established experimental gambling paradigm while an electroencephalogram was recorded. During the task, risk-taking behavior and prefrontal brain responses (feedback-related negativity [FRN]) following monetary gains and losses were assessed. FRN amplitudes were enhanced for nine-repeat-allele carriers of the DAT1 and short-allele carriers of 5HTTLPR, which are both presumably linked to less transporter activity and higher neurotransmitter levels. Moreover, nine-repeat DAT1 carriers displayed a trend toward increased risk taking in general, whereas 5HTTLPR short-allele carriers showed decreased risk taking following gains. COMT val158met genotype was unrelated to FRN amplitude and average risk taking. However, COMT met/met carriers showed a pronounced feedback P3 amplitude independent of valence, and a gradual increase in risk taking during the gambling task. In sum, the present findings underline the importance of genetic variability in the dopamine and serotonin systems regarding the neurophysiology of feedback processing.

Fiber connectivity between the striatum and cortical and subcortical regions is associated with temperaments in Chinese males

The seven-factor biopsychosocial model of personality distinguished four biologically based temperaments and three psychosocially based characters. Previous studies have suggested that the four temperaments-novelty seeking (NS), reward dependence (RD), harm avoidance (HA), and persistence (P)-have their respective neurobiological correlates, especially in the striatum-connected subcortical and cortical networks. However, few studies have investigated their neurobiological basis in the form of fiber connectivity between brain regions. This study correlated temperaments with fiber connectivity between the striatum and subcortical and cortical hub regions in a sample of 50 Chinese adult males. Generally consistent with our hypotheses, results showed that: (1) NS was positively correlated with fiber connectivity from the medial and lateral orbitofrontal cortex (mOFC, lOFC) and amygdala to the striatum; (2) RD was positively correlated with fiber connectivity from the mOFC, posterior cingulate cortex/retrosplenial cortex (PCC), hippocampus, and amygdala to the striatum; (3) HA was positively linked to fiber connectivity from the dorsolateral prefrontal cortex (dlPFC) and PCC to the striatum; and (4) P was positively linked to fiber connectivity from the mOFC to the striatum. These results extended the research on the neurobiological basis of temperaments by identifying their anatomical fiber connectivity correlates within the subcortical-cortical neural networks.

Auditory event-related potentials (P3a, P3b) and genetic variants within the dopamine and serotonin system in healthy females

The late positive components of the human event-related brain potential comprise electrocortical reflections of stimulus-driven attentional capture (the anteriorly distributed P3a) and top-down control detection of relevant events (the posteriorly distributed P3b). As of yet, the neuropharmacologic and neurogenetic origin of the P3a and P3b is not fully understood. In this study, we address the contribution of dopaminergic and serotoninergic mechanisms. Sixty healthy females completed an active auditory novelty oddball paradigm while EEG was recorded. In all subjects, genetic polymorphisms within the dopamine system (dopamine transporter [DAT1], catecholamine-O-methyltransferase val158met [COMT val158met]) and the serotonin system (serotonin transporter [5HTTLPR]) were assessed. Across genotypes, novels (relative to standards) elicited a fronto-centrally distributed P3a, and targets (relative to standards) a parieto-centrally distributed P3b. Genotypes effects were observed for both P3a (COMT, 5HTTPLR) and P3b (DAT1, COMT, 5HTTLPR) only at prefrontal electrode location (Fz). Specifically, the frontal P3a was enhanced in COMT met/met homozygotes, but not in DAT1 9R. The target-related P3b was enhanced in COMT met/met and DAT1 9R relative to its genetic counterparts, but only at frontal electrodes. This 'anteriorized' enhancement may reflect either an additional frontal component in the target-related P3 dependent on dopamine, or a more subtle shift in the neural ensemble that generates the target-related P3. Results for 5HTTLPR short allele homozygotes mimicked those in COMT met/met homozygotes. In all, the present findings suggest involvement of frontal-cortical dopaminergic and serotoninergic mechanisms in bottom-up attentional capture (COMT val158met, 5HTTLPR), with an additional top-down component sensitive to striatal signals (DAT1).

Visual event-related potentials as markers of hyperarousal in Gulf War illness: evidence against a stress-related etiology

An exaggerated response to emotional stimuli is among the many symptoms widely reported by veterans of the 1991 Persian Gulf War. These symptomologies have been attributed to damage and dysfunction associated with deployment-related exposures. We collected event-related potential data from 22 veterans meeting Haley criteria for Gulf War (GW) Syndromes 1-3 and from 8 matched GW veteran controls, who were deployed but not symptomatic, while they performed a visual three-condition oddball task where images authenticated to be associated with the 1991 Persian Gulf War were the distractor stimuli. Hyperarousal reported by ill veterans was significantly greater than that by control veterans, but this was not paralleled by higher amplitude P3a in their ERP responses to GW-related distractor stimuli. Whereas previous studies of PTSD patients have shown higher amplitude P3b responses to target stimuli that are placed amid trauma-related nontarget stimuli, ill veterans in this study showed P3b amplitudes to target stimuli - placed amid GW-related nontarget stimuli - that were significantly lower than those of the control group. Hyperarousal scores reliably predicted P3b, but not P3a, amplitudes. Although many factors may contribute to P3b amplitude differences - most notably depression and poor sleep quality, symptoms that are prevalent in the GW syndrome groups - our findings in context of previous studies on this population are consistent with the contention that dysfunction in cholinergic and dopaminergic neurotransmitter systems, and in white matter and basal ganglia may be contributing to impairments in GW veterans.

Genetic influences on composite neural activations supporting visual target identification

Behavior genetic studies of brain activity associated with complex cognitive operations may further elucidate the genetic and physiological underpinnings of basic and complex neural processing. In the present project, monozygotic (N=51 pairs) and dizygotic (N=48 pairs) twins performed a visual oddball task with dense-array EEG. Using spatial PCA, two principal components each were retained for targets and standards; wavelets were used to obtain time-frequency maps of eigenvalue-weighted event-related oscillations for each individual. Distribution of inter-trial phase coherence (ITC) and single trial power (STP) over time indicated that the early principal component was primarily associated with ITC while the later component was associated with a mixture of ITC and STP. Spatial PCA on point-by-point broad sense heritability matrices revealed data-derived frequency bands similar to those well established in EEG literature. Biometric models of eigenvalue-weighted time-frequency data suggest a link between physiology of oscillatory brain activity and patterns of genetic influence.

Functional brain networks underlying perceptual switching: auditory streaming and verbal transformations

Recent studies have shown that auditory scene analysis involves distributed neural sites below, in, and beyond the auditory cortex (AC). However, it remains unclear what role each site plays and how they interact in the formation and selection of auditory percepts. We addressed this issue through perceptual multistability phenomena, namely, spontaneous perceptual switching in auditory streaming (AS) for a sequence of repeated triplet tones, and perceptual changes for a repeated word, known as verbal transformations (VTs). An event-related fMRI analysis revealed brain activity timelocked to perceptual switching in the cerebellum for AS, in frontal areas for VT, and the AC and thalamus for both. The results suggest that motor-based prediction, produced by neural networks outside the auditory system, plays essential roles in the segmentation of acoustic sequences both in AS and VT. The frequency of perceptual switching was determined by a balance between the activation of two sites, which are proposed to be involved in exploring novel perceptual organization and stabilizing current perceptual organization. The effect of the gene polymorphism of catechol-O-methyltransferase (COMT) on individual variations in switching frequency suggests that the balance of exploration and stabilization is modulated by catecholamines such as dopamine and noradrenalin. These mechanisms would support the noteworthy flexibility of auditory scene analysis.

Event-related potential patterns associated with hyperarousal in Gulf War illness syndrome groups

An exaggerated response to emotional stimuli is one of the several symptoms widely reported by veterans of the 1991 Persian Gulf War. Many have attributed these symptoms to post-war stress; others have attributed the symptoms to deployment-related exposures and associated damage to cholinergic, dopaminergic, and white matter systems. We collected event-related potential (ERP) data from 20 veterans meeting Haley criteria for Gulf War Syndromes 1-3 and from 8 matched Gulf War veteran controls, who were deployed but not symptomatic, while they performed an auditory three-condition oddball task with gunshot and lion roar sounds as the distractor stimuli. Reports of hyperarousal from the ill veterans were significantly greater than those from the control veterans; different ERP profiles emerged to account for their hyperarousability. Syndromes 2 and 3, who have previously shown brainstem abnormalities, show significantly stronger auditory P1 amplitudes, purported to indicate compromised cholinergic inhibitory gating in the reticular activating system. Syndromes 1 and 2, who have previously shown basal ganglia dysfunction, show significantly weaker P3a response to distractor stimuli, purported to indicate dysfunction of the dopaminergic contribution to their ability to inhibit distraction by irrelevant stimuli. All three syndrome groups showed an attenuated P3b to target stimuli, which could be secondary to both cholinergic and dopaminergic contributions or disruption of white matter integrity.