How human electrophysiology informs psychopharmacology: from bottom-up driven processing to top-down control

Affective disorders and the loudness dependence of the auditory evoked potential: Serotonin and beyond

Identifying additional noninvasive biomarkers for affective disorders, such as unipolar major depressive disorder (MDD) and bipolar disorder (BD), could aid in the diagnosis and treatment of these prevalent and debilitating neuropsychiatric conditions. One such candidate biomarker is the loudness dependence of the auditory evoked potential (LDAEP), an event-related potential that measures responsiveness of the auditory cortex to different intensities of sound. The LDAEP has been associated with MDD and BD, including therapeutic response to particular classes of antidepressant drugs, while also correlating with several other neuropsychiatric disorders. It has been suggested that increased values of the LDAEP indicate low central serotonergic neurotransmission, further implicating this EEG measure in depression. Here, we briefly review the literature on the LDAEP in affective disorders, including its association with serotonergic signaling, as well as with that of other neurotransmitters such as dopamine. We summarize key findings on the LDAEP and the genetics of these neurotransmitters, as well as prediction of response to particular classes of antidepressants in MDD, including SSRIs versus noradrenergic agents. The possible relationship between this EEG measure and suicidality is addressed. We also briefly analyze acute pharmacologic studies of serotonin and/or dopamine precursor depletion and the LDAEP. In conclusion, the existing literature suggests that serotonin and norepinephrine may modulate the LDAEP in an opposing manner, and that this event-related marker may be of use in predicting response to chronic treatment with particular pharmacologic agents in the context of affective disorders, such as MDD and BD, including in the presence of suicidality.

Dopaminergic and norepinephrinergic modulation of endogenous event-related potentials: A systematic review and meta-analysis

Event-related potentials (ERPs) represent the cortical processing of sensory, motor or cognitive functions invoked by particular events or stimuli. A current theory posits that the catecholaminergic neurotransmitters dopamine (DA) and norepinephrine (NE) modulate a number of endogenous ERPs during various cognitive processes. This manuscript aims to evaluate a leading neurotransmitter hypothesis with a systematic overview and meta-analysis of pharmacologic DA and NE manipulation of specific ERPs in healthy subjects during executive function. Specifically, the frontally-distributed P3a, N2, and Ne/ERN (or error-related negativity) are supposedly modulated primarily by DA, whereas the parietally-distributed P3b is thought to be modulated by NE. Based on preceding research, we refer to this distinction between frontally-distributed DA-sensitive and parietally-distributed NE-sensitive ERP components as the Extended Neurobiological Polich (ENP) hypothesis. Our systematic review and meta-analysis indicate that this distinction is too simplistic and many factors interact with DA and NE to influence these specific ERPs. These may include genetic factors, the specific cognitive processes engaged, or elements of study design, i.e. session or sequence effects or data-analysis strategies.

A predictive model for consciousness recovery of comatose patients after acute brain injury

Background

Predicting the consciousness recovery for comatose patients with acute brain injury is an important issue. Although some efforts have been made in the study of prognostic assessment methods, it is still unclear which factors can be used to establish model to directly predict the probability of consciousness recovery.

Objectives

We aimed to establish a model using clinical and neuroelectrophysiological indicators to predict consciousness recovery of comatose patients after acute brain injury.

Methods

The clinical data of patients with acute brain injury admitted to the neurosurgical intensive care unit of Xiangya Hospital of Central South University from May 2019 to May 2022, who underwent electroencephalogram (EEG) and auditory mismatch negativity (MMN) examinations within 28 days after coma onset, were collected. The prognosis was assessed by Glasgow Outcome Scale (GOS) at 3 months after coma onset. The least absolute shrinkage and selection operator (LASSO) regression analysis was applied to select the most relevant predictors. We combined Glasgow coma scale (GCS), EEG, and absolute amplitude of MMN at Fz to develop a predictive model using binary logistic regression and then presented by a nomogram. The predictive efficiency of the model was evaluated with AUC and verified by calibration curve. The decision curve analysis (DCA) was used to evaluate the clinical utility of the prediction model.

Results

A total of 116 patients were enrolled for analysis, of which 60 had favorable prognosis (GOS ≥ 3). Five predictors, including GCS (OR = 13.400, P < 0.001), absolute amplitude of MMN at Fz site (FzMMNA, OR = 1.855, P = 0.038), EEG background activity (OR = 4.309, P = 0.023), EEG reactivity (OR = 4.154, P = 0.030), and sleep spindles (OR = 4.316, P = 0.031), were selected in the model by LASSO and binary logistic regression analysis. This model showed favorable predictive power, with an AUC of 0.939 (95% CI: 0.899-0.979), and calibration. The threshold probability of net benefit was between 5% and 92% in the DCA.

Conclusion

This predictive model for consciousness recovery in patients with acute brain injury is based on a nomogram incorporating GCS, EEG background activity, EEG reactivity, sleep spindles, and FzMMNA, which can be conveniently obtained during hospitalization. It provides a basis for care givers to make subsequent medical decisions.

How do extrinsic cues influence consumers’ online hotel booking decisions? An event-related potential experiment

Booking decision is a typical decision-making behavior in hospitality, while the neural processing of it is still unclear. To address this issue, with the help of event-related potential (ERP), this work uncovered the neural mechanism of the influence of two extrinsic cues, namely, brand familiarity (familiar vs. unfamiliar) and online reviews (positive vs. negative) on online hotel booking decisions. Behavioral results indicated that the booking rate under the condition of positive reviews was higher than that of negative reviews. In addition, the response time in the case of familiar brands was longer than that of unfamiliar brands. ERP results showed that the P200 amplitude of familiar brands was smaller than that of unfamiliar brands, while for the late positive potential amplitude, the opposite was the case. It is suggested that in the early stage of cognitive processing, unfamiliar brands evoke more automatic and unconscious attention while in the later stage, familiar brands attract more conscious attention. This study also found that the N400 amplitude of negative online reviews was larger than that of positive online reviews, indicating that negative stimuli can result in a larger emotional conflicts than that of positive stimuli. This study provides new insights into the neural mechanism of online booking decisions in the hospitality.

Relationship of loudness-dependent auditory evoked potentials with change-related cortical responses

Previous studies have suggested that change-related cortical responses are phenomena similar to the onset response and could be applied to the loudness dependence of auditory evoked potential (LDAEP) paradigm. In the present study, we examined the relationship between LDAEP and the change-related response using electroencephalography findings in 50 healthy subjects. There were five conditions (55, 65, 75, 85, and 95 dB) for LDAEP and five similar conditions (abrupt sound pressure increase from 70 to 75, 80, 85, 90, and 95 dB) for the change-related response. Both the onset and abrupt sound pressure increase evoked a triphasic response with peaks at approximately 50 (P50), 100 (N100), and 200 (P200) ms. We calculated the peak-to-peak amplitudes for P50/N100 and N100/P200. Medians and slopes for P50/N100 and N100/P200 amplitudes were calculated and compared between the two measures. Results revealed a significant correlation for both the slope and median for P50/N100 (r = 0.36, 0.37, p = 1.0 × 10⁻², 7.9 × 10⁻³), N100/P200 (r = 0.40, 0.34, p = 4.0 × 10⁻³, 1.6 × 10⁻²), and P50/N100/P200 (r = 0.36, 0.35, p = 1.0 × 10⁻², 1.3 × 10⁻²). These results suggested that the change-related response and LDAEP shared generation mechanisms at least partially.

Auditory mismatch negativity in bipolar disorder: a focused review

The auditory mismatch negativity, a component of the event-related potential elicited by an unexpected stimulus in a sequence of acoustic stimuli, provides an objective measure of the accuracy of the echoic information processing of the human brain in vivo. Auditory mismatch negativity is also a useful probe of cortical glutamatergic N-methyl-d-aspartate receptor activity and disturbance. Notably, auditory mismatch negativity is consistently impaired in schizophrenia. Because of the wide spectrum extending from bipolar affective illness and schizoaffective psychosis to typical schizophrenia, we examined the literature on auditory mismatch negativity in bipolar disorder with the aim to find any neurophysiological dysfunction concerning pre-attentive information processing shared by these clinical conditions. This focused review includes 26 original articles published in peer-reviewed journals and indexed in the National Institutes of Health National Library of Medicine (PubMed) search system. Overall, evidence is consistent with the finding that auditory mismatch negativity is impaired in bipolar disorder with psychotic features, even though to a lesser extent than in schizophrenia. It must be acknowledged that, in a few twin and family studies, mismatch negativity abnormalities were not specifically associated with bipolar disorder. In conclusion, auditory mismatch negativity research supports the involvement of the N-methyl-d-aspartate system in the pathophysiology of bipolar disorder, as previously assessed for schizophrenia, thus creating an intriguing trait d'union between these two mental illnesses and stimulating the development of novel therapeutic agents. With additional replication and validation, auditory mismatch negativity may be further considered as a correlate of a common psychopathology of schizophrenia and bipolar spectrum illnesses.

P300 and delay-discounting in obsessive-compulsive disorder

Previous research showed that dysfunctions of fronto-striatal neural networks are implicated in the pathophysiology of obsessive-compulsive disorder (OCD). Accordingly, patients with OCD showed altered performances during decision-making tasks. As P300, evoked by oddball paradigms, is suggested to be related to attentional and cognitive processes and generated in the medial temporal lobe and orbitofrontal and cingulate cortices, it is of special interest in OCD research. Therefore, this study aimed to investigate P300 in OCD and its associations with brain activity during decision-making: P300, evoked by an auditory oddball paradigm, was analysed in 19 OCD patients and 19 healthy controls regarding peak latency, amplitude and source density power in parietal cortex areas by sLORETA. Afterwards, using a fMRI paradigm, Blood-oxygen-level-dependent (BOLD) contrast imaging was conducted during a delay-discounting paradigm. We hypothesised differences between groups regarding P300 characteristics and associations with frontal activity during delay-discounting. The P300 did not differ between groups, however, the P300 latency over the P4 electrode correlated negatively with the NEO-FFI score openness to experience in patients with OCD. In healthy controls, P300 source density power correlated with activity in frontal regions when processing rewards, a finding which was absent in OCD patients. To conclude, associations of P300 with frontal brain activation during delay-discounting were found, suggesting a contribution of attentional or context updating processes. Since this association was absent in patients with OCD, the findings could be interpreted as being indeed related to dysfunctions of fronto-striatal neural networks in patients with OCD.

Relationship Between Depression After Hemorrhagic Stroke and Auditory Event-Related Potentials in a Chinese Patient Group

PURPOSE

Post-stroke depression (PSD) is the most common psychiatric sequelae of stroke. Numerous studies revealed that event-related potentials (ERP) can reflect depression severity to a certain extent, while there is almost no research on depression after hemorrhagic stroke. Therefore, we employed a prospective cross-sectional study to explore the relationship between ERP and depression after hemorrhagic stroke.

METHODS

A total of 74 patients with intracranial hemorrhage were included in this study. Neurological deficits were evaluated using the National Institutes of Health Stroke Scale (NIHSS) on admission. Depression severity and cognitive impairment were measured using the 17-item Hamilton Depression Scale (HAMD-17) and the Chinese version of the Montreal Cognitive Assessment (MoCA) after two weeks of treatment. All patients were conducted auditory Oddball paradigm for event-related potential mismatch negativity (MMN) and P300.

RESULTS

In total, 36 patients were diagnosed with PSD at the two weeks of treatment, for a percentage of 48.6%. Depression severity of ICH patients correlated positively with both the latency of MMN (r = 0.376, P = 0.001) and P300 (r = 0.325, P = 0.005), and correlated negatively with both the amplitude of MMN (r=-0.385, P = 0.001) and P300 (r=-0.311, P = 0.007). Depression severity was negatively correlated with cognitive function after hemorrhagic stroke (r=-0.347, P = 0.002).

CONCLUSION

The latency and amplitude of MMN and P300 can well reflect the degree of depression after hemorrhagic stroke, which may help in the early diagnosis and effective treatment of PSD.

Decreased mismatch negativity and elevated frontal-lateral connectivity in first-episode psychosis

Decreased mismatch negativity (MMN) is a proposed biomarker for psychotic disorders. However, the magnitude of the effect appears to be attenuated in first-episode populations. Furthermore, how mismatch negativity amplitudes are related to brain connectivity in this population is unclear. In this study, we used high-density EEG to record duration-deviant MMN from 22 patients with first-episode psychosis (FEP) and 23 age-matched controls (HC). Consistent with past work, we found decreased MMN amplitude in FEP over a large area of the frontal scalp. We also found decreased latency over the occipital scalp. MMN amplitude was negatively correlated with antipsychotic dose. We used Granger causality to investigate directional connectivity between frontal, midline, left, and right scalp during MMN and found reduced connectivity in FEP compared to HC and following deviant stimuli compared to standard stimuli. FEP participants with smaller decreases in connectivity from standard to deviant stimuli had worse disorganization symptoms. On the other hand, connectivity from the front of the scalp following deviant stimuli was relatively preserved in FEP compared to controls. Our results suggest that a relative imbalance of bottom-up and top-down perceptual processing is present in the early stages of psychotic disorders.

Loudness Dependence of Auditory-evoked Potentials, a Marker of Central Serotonergic Activity, is Affected by Fasting and Selective Uptake of Food

Serotonin is an important neuromodulator involved in many physiological processes including mood and satiety. In the brain, serotonin is manufactured from tryptophan, as serotonin itself cannot cross the blood-brain barrier. Previous research has shown that blood-tryptophan levels increase upon ingestion of carbohydrates and decrease upon protein consumption. How this translates into serotonin availability is as yet under-researched. Therefore, we examined the effect of fasting versus consuming carbohydrates or protein on central serotonergic activity using a repeated-measures crossover design in a sample of 37 healthy men. The loudness dependence of auditory-evoked potentials (LDAEP) serves as a noninvasive method to study central serotonergic activity. Blood-glucose levels and mood changes were also monitored before and after the nutritional intervention. The intervention had a significant nutrition-specific effect on LDAEP and blood-glucose levels. A significant difference emerged between the fasting condition and satiety, with LDAEP being lower during satiety, irrespective of the type of food. Thus, this indicator of serotonergic activity increased after food consumption, which was further related to mood improvement. Moreover, the LDAEP differed between the 2 measurements only for the carbohydrate testing day, suggesting that LDAEP can be selectively modulated by the type of nutrition consumed. Our data further indicate a high intraindividual stability of LDAEP, as the electrophysiological signals were very similar in the fasting condition across the 2 testing days. Together, these findings demonstrate that the LDAEP can serve as a biological marker for central serotonergic activity, while at the same time being sensitive to nutritional changes.

Mismatch negativity in patients with major depressive disorder: A meta-analysis

OBJECTIVE

Deficits of mismatch negativity (MMN), a general index of echoic memory function, have been documented in patients with schizophrenia. However, it remains controversial whether patients with major depressive disorder (MDD) demonstrate MMN defects compared with healthy controls (HC).

METHODS

After screening 41 potential studies identified in PubMed and Medline, 13 studies consisting of 343 HC and 339 patients with MDD were included in the present meta-analysis. The effect sizes (Hedges's g) with a random-effect and inverse-variance weighted model were estimated for the MMN amplitudes and latencies. The effects of different deviant types (i.e., frequency and duration) and of different illness stages (i.e., acute and chronic) on MMN were also examined.

RESULTS

We found that 1) MMN amplitudes (g = 1.273, p < 0.001) and latencies (g = 0.303, p = 0.027) to duration, but not frequency deviants, were significantly impaired in patients with MDD compared to HC; 2), acute patients exhibited lower MMN amplitudes (g = 1.735, p < 0.001) and prolonged MMN latencies (g = 0.461, p = 0.007) for the duration deviants compared to HC. Only the attenuated duration MMN amplitudes were detected in patients with chronic MDD (g = 0.822, p = 0.027); and 3) depressive symptoms did not significantly correlate with MMN responses.

CONCLUSIONS

Patients with MDD demonstrated abnormal MMN responses to duration deviants compared to HC.

SIGNIFICANCE

Duration MMN may constitute an electrophysiological indicator to differentiate HC from patients with MDD, particularly those in the acute stage.

Clinical significance of mismatch negativity in predicting the awakening of comatose patients after severe brain injury

We assessed the clinical significance of mismatch negativity (MMN) in predicting the awakening of comatose patients with severe brain injury. The clinical data of patients with severe brain injury, admitted to the neurosurgical intensive care unit of Xiangya Hospital of Central South University from July 2018 to March 2020, who underwent auditory MMN examinations within 28 days after coma onset, were reviewed. Correlations between clinical factors and prognosis [Glasgow Outcome Scale (GCS) for 3 mo] were analyzed. Fifty-three patients were included; 37 (69.8%) had favorable outcomes. A univariate analysis revealed the Glasgow Coma Scale (GCS) and absolute MMN amplitudes at electrodes Fz and Cz were significantly correlated with prognosis. Only GCS scores and MMN amplitude at Fz were independent predictors in multivariate logistic regression analysis (area under the curve 0.744 vs. 0.753, respectively); both combined, improved accuracy to 84.6%. MMN amplitudes at Fz were dichotomized at a value of 1.08 μV with a sensitivity and specificity of 81.1% and 68.7%, respectively, for predicting comatose patients' awakening. In conclusion, MMN amplitude at Fz is a reliable prognostic indicator for comatose patients with severe brain injury; the prediction value improved when combined with GCS. Thus, an event-related potential component with a clear site and cutoff value may support prognostication in severe brain injury.NEW & NOTEWORTHY Mismatch negativity (MMN) can assess the prognosis of comatose patients after severe brain injury, especially for MMN amplitude. In addition, MMN analysis at electrode Fz best predicts recovery of consciousness in patients with severe brain injury. Importantly, a quantitative approach (cutoff value of 1.08 μV) may improve the use of MMN for prognostication.

Mismatch Negativity and Loudness Dependence of Auditory Evoked Potentials among Patients with Major Depressive Disorder, Bipolar II Disorder, and Bipolar I Disorder

Mismatch negativity (MMN) and loudness dependence of auditory evoked potentials (LDAEP), which are event-related potentials, have been investigated as biomarkers. MMN indicates the pre-attentive function, while LDAEP may be an index of central serotonergic activity. This study aimed to test whether MMN and LDAEP are useful biological markers for distinguishing patients with bipolar disorder (BD) and major depressive disorder (MDD), as well as the relationship between MMN and LDAEP. Fifty-five patients with major depressive episodes, aged 20 to 65 years, who had MDD (n = 17), BD type II (BIID) (n = 27), and BD type I (BID) (n = 11), were included based on medical records. Patients with MDD had a higher MMN amplitude than those with BID. In addition, the MMN amplitude in F4 positively correlated with the Korean version of mood disorder questionnaire scores (r = 0.37, p = 0.014), while the MMN amplitude in F3 correlated negatively with LDAEP (r = −0.30, p = 0.024). The odds ratios for the BID group and some variables were compared with those for the MDD group using multinomial logistic regression analysis. As a result, a significant reduction of MMN amplitude was found under BID diagnosis compared to MDD diagnosis (p = 0.015). This study supported the hypothesis that MMN amplitude differed according to MDD, BIID, and BID, and there was a relationship between MMN amplitude and LDAEP. These findings also suggested that BID patients had a reduced automatic and pre-attentive processing associated with serotonergic activity or N-methyl-D-aspartate receptor.

The relationship between auditory evoked potentials and symptoms of attention-deficit/hyperactivity disorder in adult patients with major depressive disorder

OBJECTIVES

Loudness dependence of auditory evoked potential (LDAEP) has been proposed as a biological marker for central serotonergic activity in depressive illness. A recent study has suggested that serotonin plays an important role in impulsivity and emotional sensitivity that are prominent clinical manifestations in attention deficit and hyperactivity disorder (ADHD). The objective of this study was to examine the association between LDAEP and ADHD symptoms in major depressive disorder (MDD).

METHODS

A total of 60 participants (40 subjects with MDD and 20 healthy controls) aged >18 years who had LDAEPs performed during electroencephalograms were included in this study. ADHD symptoms, depressive, and anxiety symptoms were evaluated. Psychological characteristics and event-related potentials (ERP) were compared among three groups: depression with ADHD symptoms, depression without ADHD symptoms, and healthy controls.

RESULTS

MDD subjects with ADHD symptoms (N = 20) showed significantly lower LDAEP levels than those without ADHD symptoms (N = 20) and healthy controls (N = 20). LDAEP differences between MDD subjects without ADHD symptoms and healthy controls were not statistically significant. In partial correlation analyses adjusted for age and sex, significant correlations of psychological scales of depression, ADHD symptoms, and LDAEPs were found.

CONCLUSION

Results of the present study suggest that LDAEP can reflect adult ADHD symptoms in MDD. Auditory evoked potential appears to be a promising candidate as an evaluation tool for inattention and poor impulse control as well as emotional sensitivity.

Elucidating the glutamatergic processes underlying mismatch negativity deficits in early stage bipolar disorder and schizophrenia: A combined 1H-MRS and EEG study

Impairments in mismatch negativity (MMN) in schizophrenia are well-established; these findings have been extended to show impairments at early illness stages and in bipolar disorder. A substantial literature supports MMN as an index of NMDA receptor output, however, few studies have conducted in vivo assessments to elucidate the neurochemical underpinnings of MMN. Sixty young (16-33 years) participants with bipolar disorder (n = 47) or schizophrenia (n = 13) underwent ¹H-MRS and MMN assessment. Glutamate over creatine (Glu/Cr) levels in the anterior cingulate cortex (ACC) and hippocampus were determined and MMN was measured frontally and temporally. Correlational analyses assessed the relationship between MMN amplitudes and Glu/Cr. Any significant relationships were assessed for specificity with a follow up correlation analysis of MMN and n-acetyleaspartate (NAA/Cr). No associations between frontal or temporal MMN and ACC or hippocampal Glu/Cr were noted in the bipolar group. In the schizophrenia group, frontal and right temporal MMN amplitudes corresponded with increased ACC Glu/Cr at the trend-level. Right temporal MMN was similarly significantly associated with NAA/Cr. MMN was not associated with hippocampal Glu/Cr. This work provides in vivo evidence that glutamatergic processes may underlie MMN generation in early stage schizophrenia but not in early stage bipolar disorder suggesting differences in the MMN mechanism in these groups. The negative association between ACC Glu/Cr and MMN is consistent with findings of reduced MMN and increased in vivo glutamatergic neurometabolite levels in early stage schizophrenia. Furthermore, these results indicate that examining in vivo NAA/Cr may have provide additional insights into the MMN mechanism in schizophrenia.

Effect of GAD1 genotype status on auditory attention and acute nicotine administration in healthy volunteers

OBJECTIVE

The effects of GABA modulating drugs and nicotine, the prototypical nicotinic cholinergic agonist, on attention have been investigated using subcomponents of the P300 event-related potentials (ERP), which index involuntary (P3a) and voluntary attention (P3b). However, investigations into how such pharmacologic effects interact with genetic features in the GABA system remain unclear. This study examined the moderating effects of a single nucleotide polymorphism (rs7557793) in the glutamic acid decarboxylase 67 (GAD1) gene, which is implicated in the conversion of glutamate to GABA, on P300-indices of auditory attentional processing; the influence of nicotine administration was also assessed.

METHODS

The effects of GAD1 genotype (TT/CC/CT) were examined on the P3a/b in response to an auditory selective attention task in healthy, nonsmoking male volunteers (N = 126; 18-40 years). Participants responded to rare target stimuli (P3b-eliciting) and ignored frequent nontarget stimuli as well as rare distractor stimuli (P3a-eliciting). In a subsample (N = 59), P3a/b profiles to acute nicotine (vs. placebo) administration were examined as a function of GAD1 genotype. As a secondary aim, earlier sensory processes were assessed with N200 ERP subcomponents elicited by novel (N2a) and target (N2b) auditory stimuli.

RESULTS

GAD1 allelic variation moderated early sensory processes, enhancing N2a amplitudes in CT versus TT carriers. Further, TT homozygotes exhibited larger P3b amplitudes than CC homozygotes in the placebo versus nicotine condition. Regardless of genotype, nicotine versus placebo moderated the N200 ERP.

CONCLUSION

These findings expand our knowledge regarding the attentional effects of GAD1 genetic variants in relation to nicotine.

Non-contact Wearable EEG Sensors for SSVEP-based Brain Computer Interface Applications

Electroencephalography (EEG) based brain computer interfaces (BCI) introduces promising communication pathway between the brain and external devices, not only for the motor-impaired but also the healthy users. However, the current EEG-based interface device is not convenient enough for daily uses. In this study, we developed an EEG acquisition system that records brain signals without contacting scalp. The proposed system consists of a small sized ($5.5\,\times 3\,\mathrm{cm}^{2}$ acquisition hardware and four stainless steel electrodes integrated in a regular sport hat. To demonstrate the concept, we used an in-house developed steady-state visual evoked potentials (SSVEP) paradigm and recorded EEG signals using the proposed system. The EEG signals were compared with three different brain states - Eye Closed, Eye Open, and Visual Stimulation. The results show that the BCI system can record SSVEP from the brain without any professional setups or expensive dry-electrodes.

Gender effects on auditory P300: A systematic review

The evidence suggests that gender-related effects could influence the electrophysiological P300 parameters and stand as an additional source of variation for both clinical and non-clinical subjects. The aim of this paper is to characterize gender-related differences in P300 potential as elicited with simple auditory paradigms. This knowledge (1) is important for the practical assessment of P300 potential in normal and clinical populations, and (2) can provide an insight into the understanding of gender differences in pathophysiology, particularly those with differential risk or prevalence in males and females. With this review it is shown that a limited number of studies encounter possible gender effects on parameters of auditory P300, and the findings need to be read with caution due to methodological limitations of the studies. Nevertheless, evidence supports that the P300 amplitude could be significantly modulated by gender, with greater amplitude in females relative to males. Noteworthy, gender has a minimal effect on the P300 latency, and it is often comparable between males and females. Furthermore, the effect of gender on P300 could be modulated by hormonal background, anatomy and some methodological aspects.

Association between Cortical GABA and Loudness Dependence of Auditory Evoked Potentials (LDAEP) in Humans

Loudness dependence of auditory evoked potentials (LDAEP) is a widely used EEG-based biomarker for central serotonergic activity. Serotonin has been shown to be associated with different psychiatric disorders such as depression and schizophrenia. Despite its clinical significance, the underlying neurochemical mechanism of this promising marker is not fully understood, and further research is needed to improve its validity. Other neurotransmitters might have a significant impact on this measure. Thus, we assessed the inhibitory action through individual GABA/H20 concentrations and GABA/glutamate ratios by means of magnetic resonance spectroscopy at 3T in healthy subjects. The measurements were assessed in the primary auditory cortex to investigate the association with the LDAEP, whose generators are mainly in the primary auditory cortex. For the first time, this study examines the link between GABAergic neurotransmission and LDAEP, and the data preliminary show that GABA may not contribute to the generation of EEG-based LDAEP.

A Perceptual Inference Mechanism for Hallucinations Linked to Striatal Dopamine

Hallucinations, a cardinal feature of psychotic disorders such as schizophrenia, are known to depend on excessive striatal dopamine. However, an underlying cognitive mechanism linking dopamine dysregulation and the experience of hallucinatory percepts remains elusive. Bayesian models explain perception as an optimal combination of prior expectations and new sensory evidence, where perceptual distortions such as illusions and hallucinations may occur if prior expectations are afforded excessive weight. Such excessive weight of prior expectations, in turn, could stem from a gain-control process controlled by neuromodulators such as dopamine. To test for such a dopamine-dependent gain-control mechanism of hallucinations, we studied unmedicated patients with schizophrenia with varying degrees of hallucination severity and healthy individuals using molecular imaging with a pharmacological manipulation of dopamine, structural imaging, and a novel task designed to measure illusory changes in the perceived duration of auditory stimuli under different levels of uncertainty. Hallucinations correlated with a perceptual bias, reflecting disproportional gain on expectations under uncertainty. This bias could be pharmacologically induced by amphetamine, strongly correlated with striatal dopamine release, and related to cortical volume of the dorsal anterior cingulate, a brain region involved in tracking environmental uncertainty. These findings outline a novel dopamine-dependent mechanism for perceptual modulation in physiological conditions and further suggest that this mechanism may confer vulnerability to hallucinations in hyper-dopaminergic states underlying psychosis.

TRIMAGE: A dedicated trimodality (PET/MR/EEG) imaging tool for schizophrenia

Simultaneous PET/MR/EEG (Positron Emission Tomography - Magnetic Resonance - Electroencephalography), a new tool for the investigation of neuronal networks in the human brain, is presented here within the framework of the European Union Project TRIMAGE. The trimodal, cost-effective PET/MR/EEG imaging tool makes use of cutting edge technology both in PET and in MR fields. A novel type of magnet (1.5T, non-cryogenic) has been built together with a PET scanner that makes use of the most advanced photodetectors (i.e., SiPM matrices), scintillators matrices (LYSO) and digital electronics. The combined PET/MR/EEG system is dedicated to brain imaging and has an inner diameter of 260 mm and an axial Field-of-View of 160 mm. It enables the acquisition and assessment of molecular metabolic information with high spatial and temporal resolution in a given brain simultaneously. The dopaminergic system and the glutamatergic system in schizophrenic patients are investigated via PET, the same physiological/pathophysiological conditions with regard to functional connectivity, via fMRI, and its electrophysiological signature via EEG. In addition to basic neuroscience questions addressing neurovascular-metabolic coupling, this new methodology lays the foundation for individual physiological and pathological fingerprints for a wide research field addressing healthy aging, gender effects, plasticity and different psychiatric and neurological diseases. The preliminary performances of two components of the imaging tool (PET and MR) are discussed. Initial results of the search of possible candidates for suitable schizophrenia biomarkers are also presented as obtained with PET/MR systems available to the collaboration.

Heightened early-attentional stimulus orienting and impulsive action in men with antisocial personality disorder

We tested whether enhanced stimulus orienting operationalized as N1 and P2 auditory evoked potentials to increasing loudness (50-90 dB clicks) could be associated with trait impulsivity (Barratt Impulsiveness Scale, BIS-11), impulsive action (commission error on the Immediate Memory Task), or impulsive choice (immediate responses on temporal discounting tasks). We measured N1 and P2 loudness sensitivity in a passive listening task as linear intensity-sensitivity slopes in 36 men with antisocial personality disorder with a history of conviction for criminal conduct and 16 healthy control men. Across all subjects, regression analyses revealed that a steeper P2 slope predicted higher IMT commission error/correct detection ratio, and lower stimulus discriminability (A-prime). These associations were also found within both groups. These relationships suggest an association between enhanced early stimulus orienting (P2), impulsive action (response inhibition), and impaired signal-noise discriminability (A-prime).

The Effects of Attention on the Trigeminal Blink Reflex

During top-down processing, higher cognitive processes modulate lower sensory processing. The present experiment tested the effects of directed attention on trigeminal reflex blinks in humans (n = 8). In separate sessions, participants either attended to blink-eliciting stimuli or were given no attentional instructions during stimulation of the supraorbital branch of the trigeminal nerve. Attention to blink-eliciting stimuli significantly increased reflex blink amplitude and duration and shortened blink latency compared with the no attention condition. These results suggested that higher processes such as attention can modify the trigeminal blink reflex circuit.

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.

Dopaminergic modulation of performance monitoring in Parkinson's disease: An event-related potential study

Monitoring one’s actions is essential for goal-directed performance. In the event-related potential (ERP), errors are followed by fronto-centrally distributed negativities. These error(-related) negativity (N_e/ERN) amplitudes are often found to be attenuated in patients with Parkinson’s disease (PD) compared to healthy controls (HC). Although N_e/ERN has been proposed to be related to dopaminergic neuronal activity, previous research did not find evidence for effects of dopaminergic medication on N_e/ERN amplitudes in PD. We examined 13 PD patients “on” and “off” dopaminergic medication. Their response-locked ERP amplitudes (obtained on correct [N_c/CRN] and error [N_e/ERN] trials of a flanker task) were compared to those of 13 HC who were tested twice as well, without receiving dopaminergic medication. While PD patients committed more errors than HC, error rates were not significantly modulated by dopaminergic medication. PD patients showed reduced N_e/ERN amplitudes relative to HC; however, this attenuation of response-locked ERP amplitudes was not specific to errors in this study. PD-related attenuation of response-locked ERP amplitudes was most pronounced when PD patients were on medication. These results suggest overdosing of dopaminergic pathways that are relatively spared in PD, but that are related to the generation of the N_e/ERN, notably pathways targeted on the medial prefrontal cortex.

Haloperidol 2 mg impairs inhibition but not visuospatial attention

RATIONALE

The dopaminergic system has been implicated in visuospatial attention and inhibition, but the exact role has yet to be elucidated. Scarce literature suggests that attenuation of dopaminergic neurotransmission negatively affects attentional focusing and inhibition. To the best of our knowledge, this is the first study that evaluated the effect of dopaminergic antagonism on stopping performance.

METHODS

Dopaminergic neurotransmission was attenuated in 28 healthy male participants by using 2 mg haloperidol. A repeated-measures placebo-controlled crossover design was implemented, and performance indices of attention and inhibition were assessed in the visual spatial cueing task (VSC) and stop signal task (SST). Additionally, the effect of haloperidol on motoric parameters was assessed. It was expected that haloperidol as contrasted to placebo would result in a reduction of the "validity effect," the benefit of valid cueing as opposed to invalid cueing of a target in terms of reaction time. Furthermore, an increase in stop signal reaction time (SSRT) in the SST was expected.

RESULTS AND CONCLUSION

Results partially confirmed the hypothesis. Haloperidol negatively affected inhibitory motor control in the SST as indexed by SSRT, but there were no indications that haloperidol affected bias or disengagement in the VSC task as indicated by a lack of an effect on RTs. Pertaining to secondary parameters, motor activity increased significantly under haloperidol. Haloperidol negatively affected reaction time variability and errors in both tasks, as well as omissions in the SST, indicating a decreased sustained attention, an increase in premature responses, and an increase in lapses of attention, respectively.

What can time-frequency and phase coherence measures tell us about the genetic basis of P3 amplitude?

In a recent comprehensive investigation, we largely failed to identify significant genetic markers associated with P3 amplitude or to corroborate previous associations between P3 and specific single nucleotide polymorphisms (SNPs) or genes. In the present study we extended this line of investigation to examine time-frequency (TF) activity and intertrial phase coherence (ITPC) in the P3 time window, both of which are associated with P3 amplitude. Previous genome-wide research has reported associations between P3-related theta and delta activity and individual genetic variants. A large, population-based sample of 4211 subjects, comprising male and female adolescent twins and their parents, was genotyped for 527,828 single nucleotide polymorphisms (SNPs), from which over six million SNPs were accurately imputed. Heritability estimates were greater for TF energy than ITPC, whether based on biometric models or the combined influence of all measured SNPs (derived from genome-wide complex trait analysis). The magnitude of overlap in the specific SNPs associated with delta energy and ITPC and P3 amplitude was significant. A genome-wide analysis of all SNPs, accompanied by an analysis of approximately 17,600 genes, indicated a region of chromosome 2 around TEKT4 that was significantly associated with theta ITPC. Analysis of candidate SNPs and genes previously reported to be associated with P3 or related phenotypes yielded one association surviving correction for multiple tests: between theta energy and CRHR1. However, we did not obtain significant associations for SNPs implicated in previous genome-wide studies of TF measures. Identifying specific genetic variants associated with P3 amplitude remains a challenge.

Acute effects of cocaine and cannabis on response inhibition in humans: an ERP investigation

Substance abuse has often been associated with alterations in response inhibition in humans. Not much research has examined how the acute effects of drugs modify the neurophysiological correlates of response inhibition, or how these effects interact with individual variation in trait levels of impulsivity and novelty seeking. This study investigated the effects of cocaine and cannabis on behavioural and event-related potential (ERP) correlates of response inhibition in 38 healthy drug using volunteers. A double-blind placebo-controlled randomized three-way crossover design was used. All subjects completed a standard Go/NoGo task after administration of the drugs. Compared with a placebo, cocaine yielded improved accuracy, quicker reaction times and an increased prefrontal NoGo-P3 ERP. Cannabis produced opposing results; slower reaction times, impaired accuracy and a reduction in the amplitude of the prefrontal NoGo-P3. Cannabis in addition decreased the amplitude of the parietally recorded P3, while cocaine did not affect this. Neither drugs specifically affected the N2 component, suggesting that pre-motor response inhibitory processes remain unaffected. Neither trait impulsivity nor novelty seeking interacted with drug-induced effects on measures of response inhibition. We conclude that acute drug effects on response inhibition seem to be specific to the later, evaluative stages of response inhibition. The acute effects of cannabis appeared less specific to response inhibition than those of cocaine. Together, the results show that the behavioural effects on response inhibition are reflected in electrophysiological correlates. This study did not support a substantial role of vulnerability personality traits in the acute intoxication stage.

Multimodal EEG Recordings, Psychometrics and Behavioural Analysis

High spatial and temporal resolution measurements of neuronal activity are preferably combined. In an overview on how this approach can take shape, multimodal electroencephalography (EEG) is treated in 2 main parts: by experiments without a task and in the experimentally cued working brain. It concentrates first on the alpha rhythm properties and next on data-driven search for patterns such as the default mode network. The high-resolution volumic distributions of neuronal metabolic indices result in distributed cortical regions and possibly relate to numerous nuclei, observable in a non-invasive manner in the central nervous system of humans. The second part deals with paradigms in which nowadays assessment of target-related networks can align level-dependent blood oxygenation, electrical responses and behaviour, taking the temporal resolution advantages of event-related potentials. Evidence-based electrical propagation in serial tasks during performance is now to a large extent attributed to interconnected pathways, particularly chronometry-dependent ones, throughout a chain including a dorsal stream, next ventral cortical areas taking the flow of information towards inferior temporal domains. The influence of aging is documented, and results of the first multimodal studies in neuropharmacology are consistent. Finally a scope on implementation of advanced clinical applications and personalized marker strategies in neuropsychiatry is indicated.

Opposite effects of cannabis and cocaine on performance monitoring

Drug use is often associated with risky and unsafe behavior. However, the acute effects of cocaine and cannabis on performance monitoring processes have not been systematically investigated. The aim of the current study was to investigate how administration of these drugs alters performance monitoring processes, as reflected in the error-related negativity (ERN), the error positivity (Pe) and post-error slowing. A double-blind placebo-controlled randomized three-way crossover design was used. Sixty-one subjects completed a Flanker task while EEG measures were obtained. Subjects showed diminished ERN and Pe amplitudes after cannabis administration and increased ERN and Pe amplitudes after administration of cocaine. Neither drug affected post-error slowing. These results demonstrate diametrically opposing effects on the early and late phases of performance monitoring of the two most commonly used illicit drugs of abuse. Conversely, the behavioral adaptation phase of performance monitoring remained unaltered by the drugs.

Acute effects of BZP, TFMPP and the combination of BZP and TFMPP in comparison to dexamphetamine on an auditory oddball task using electroencephalography: a single-dose study

RATIONALE

Piperazine-based designer drugs such as benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been marketed and sold as legal alternatives to dexamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) until 2008 in New Zealand. When administered in combination, BZP + TFMPP have been reported to produce drug-drug synergism in rodents by stimulating the release of dopamine and serotonin.

OBJECTIVES

This study was to evaluate the acute event-related potential effects of BZP, TFMPP or the combination of BZP + TFMPP compared with dexamphetamine in young healthy male adults.

METHODS

A double-blind, randomised, placebo-controlled study investigated the effects of BZP, TFMPP, the combination of BZP + TFMPP, and dexamphetamine on the event-related potentials during an auditory oddball task. Healthy, right-handed males were given a single oral dose of either BZP (200 mg), TFMPP (60 mg), a combination of BZP + TFMPP (100/30 mg), dexamphetamine (20 mg) or placebo (lactose) and tested both before and 120 min after drug administration.

RESULTS

A single dose of either TMFPP (t = -2.29, p = 0.03) or dexamphetamine (t = -2.33, p = 0.02) significantly reduced the P300 amplitude. A similar trend was also found in BZP. In contrast, BZP and TFMPP in combination has no effect. Neither P300 latency nor the mean reaction time was affected by any of the drug treatments. In addition, neither the P100 nor the P200 component was significantly affected following any of the drug treatments.

CONCLUSIONS

A single oral dose of BZP or TFMPP, but not the combination of BZP/TFMPP, affected auditory sensory-evoked P300 potential in a manner similar to dexamphetamine.

What do phasic cholinergic signals do?

In addition to the neuromodulatory role of cholinergic systems, brief, temporally discrete cholinergic release events, or "transients", have been associated with the detection of cues in attention tasks. Here we review four main findings about cholinergic transients during cognitive processing. Cholinergic transients are: (1) associated with the detection of a cue and influenced by cognitive state; (2) not dependent on reward outcome, although the timing of the transient peak co-varies with the temporal relationship between detection and reward delivery; (3) correlated with the mobilization of the cue-evoked response; (4) causal mediators of shifts from monitoring to cue detection. We next discuss some of the key questions concerning the timing and occurrence of transients within the framework of available evidence including: (1) Why does the shift from monitoring to cue detection require a transient? (2) What determines whether a cholinergic transient will be generated? (3) How can cognitive state influence transient occurrence? (4) Why do cholinergic transients peak at around the time of reward delivery? (5) Is there evidence of cholinergic transients in humans? We conclude by outlining future research studies necessary to more fully understand the role of cholinergic transients in mediating cue detection.

Atypical sensory reactivity influences auditory attentional control in adults with autism spectrum disorders

Frequent observations of atypical sensory reactivity in people with autism spectrum disorders (ASD) suggest that the perceptual experience of those on the Spectrum is dissimilar to neurotypicals. Moreover, variable attention abilities in people with ASD, ranging from good control to periods of high distractibility, may be related to atypical sensory reactivity. This study used auditory event-related potential (ERP) measures to evaluate top-down and bottom-up attentional processes as a function of perceptual load, and examined these factors with respect to sensory reactivity. Twenty-five age and IQ-matched participants (ASD: 22.5 year, SD = 4.1 year; Controls: 22.8 year, SD = 5.1 year) completed the Adolescent/Adult Sensory Profile prior to performing a modified 3-stimulus (target, non-target, and distractor) auditory oddball target detection task EEG was recorded during task completion. ERP analysis assessed early sensory processing (P50, ∼50 ms latency; N100, ∼100 ms latency), cognitive control (N200, ∼200 ms latency), and attentional processing (P3a and P3b, ∼300 ms latency). Behavioral data demonstrates participants with ASD and neurotypical performed similarly on auditory target detection, but diverged on sensory profiles. Target ERP measures associated with top-down control (P3b latency) significantly increased under greater load in controls, but not in participants with ASD. Early ERP responses associated with bottom-up attention (P50 amplitude) were positively correlated to increased sensory sensitivity. Findings suggest specific neural mechanisms for increased perceptual capacity and enhanced bottom-up processing of sensory stimuli in people with autism. Results from participants with ASD are consistent with load theory and enhanced perceptual functioning. Autism Res 2016, 9: 1079-1092. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Brain oscillations in bipolar disorder and lithium-induced changes

Electroencephalography (EEG) studies in patients with bipolar disorder have revealed lower amplitudes in brain oscillations. The aim of this review is to describe lithium-induced EEG changes in bipolar disorder and to discuss potential underlying factors. A literature survey about lithium-induced EEG changes in bipolar disorder was performed. Lithium consistently enhances magnitudes of brain oscillations in slow frequencies (delta and theta) in both resting-state EEG studies as well as event-related oscillations studies. Enhancement of magnitudes of beta oscillations is specific to event-related oscillations. Correlation between serum lithium levels and brain oscillations has been reported. Lithium-induced changes in brain oscillations might correspond to lithium-induced alterations in neurotransmitters, signaling cascades, plasticity, brain structure, or biophysical properties of lithium. Therefore, lithium-induced changes in brain oscillations could be promising biomarkers to assess the molecular mechanisms leading to variability in efficacy. Since the variability of lithium response in bipolar disorder is due to the genetic differences in the mechanisms involving lithium, it would be highly promising to assess the lithium-induced EEG changes as biomarkers in genetic studies.

Effects of clonidine and scopolamine on multiple target detection in rapid serial visual presentation

RATIONALE

The specific role of neuromodulator systems in regulating rapid fluctuations of attention is still poorly understood.

OBJECTIVES

In this study, we examined the effects of clonidine and scopolamine on multiple target detection in a rapid serial visual presentation task to assess the role of the central noradrenergic and cholinergic systems in temporal attention.

METHOD

Eighteen healthy volunteers took part in a crossover double-dummy study in which they received clonidine (150/175 μg), scopolamine (1.2 mg), and placebo by mouth in counterbalanced order. A dual-target attentional blink task was administered at 120 min after scopolamine intake and 180 min after clonidine intake. The electroencephalogram was measured during task performance.

RESULTS

Clonidine and scopolamine both impaired detection of the first target (T1). For clonidine, this impairment was accompanied by decreased amplitudes of the P2 and P3 components of the event-related potential. The drugs did not impair second-target (T2) detection, except if T2 was presented immediately after T1. The attentional blink for T2 was not affected, in line with a previous study that found no effect of clonidine on the attentional blink.

CONCLUSIONS

These and other results suggest that clonidine and scopolamine may impair temporal attention through a decrease in tonic alertness and that this decrease in alertness can be temporarily compensated by a phasic alerting response to a salient stimulus. The comparable behavioral effects of clonidine and scopolamine are consistent with animal studies indicating close interactions between the noradrenergic and cholinergic neuromodulator systems.

Resting EEG and ERPs findings in methadone-substituted opiate users: a review

Methadone has been used to treat opiate dependence since the mid-1960s. Despite its clinical effectiveness there is evidence from neuropsychological studies demonstrating that its long-term use might have negative effects on cognition. Nevertheless, it remains uncertain whether the observed cognitive impairments in patients undertaking methadone maintenance treatment (MMT) are solely attributable to the pharmacological effects of methadone, as suggested by some researchers. Determining the effects of MMT on neuropsychological function using electroencephalography (EEG) combined with event-related potentials (ERP) has been used infrequently. However EEG and ERP provide a means of closely examining information processing to determine whether MMT induces any deficits. The purpose of this review was to investigate whether psychophysiological evidence supports cognitive impairment in association with MMT by focusing on research using EEG and ERPs. The findings of EEG studies to date appear not support the notion that cognitive impairments are attributable to the specific pharmacological effects of methadone suggested by some neuropsychological studies. However, due to the methodological deficits and limited number of the studies, any conclusion based on the findings of the existing EEG studies should be avoided.

The Loudness Dependence of Auditory Evoked Potentials (LDAEP) in individuals at risk for developing bipolar disorders and schizophrenia

OBJECTIVES

The Loudness Dependence of Auditory Evoked Potentials (LDAEP) is considered as an indicator of central serotonergic activity. Alteration of serotonergic neurotransmission was reported in bipolar disorders and schizophrenia. In line with previous reports on clinically manifest disorders, we expected a weaker LDAEP in subjects at risk for bipolar disorders and schizophrenia compared to healthy controls.

METHODS

We analyzed LDAEP of individuals at risk for developing bipolar disorders (n=27), with high-risk status (n=74) and ultra-high-risk status for schizophrenia (n=86) and healthy controls (n=47).

RESULTS

The LDAEP did not differ between subjects at risk for schizophrenia or bipolar disorders and controls. Among subjects without medication (n=122), the at-risk-bipolar group showed a trend towards a weaker LDAEP than both the high-risk and the ultra-high-risk groups for schizophrenia.

CONCLUSIONS

The LDAEP did not appear as a vulnerability marker for schizophrenia or bipolar disorders. This suggests that an altered LDAEP may not be measurable until the onset of clinically manifest disorder. However, the hypothesis that pathogenic mechanisms leading to bipolar disorders may differ from those leading to schizophrenia is supported.

SIGNIFICANCE

This is the first study investigating LDAEP in a population at risk for bipolar disorders.

Utility of event-related potentials in predicting antidepressant treatment response: An iSPOT-D report

It is essential to improve antidepressant treatment of major depressive disorder (MDD) and one way this could be achieved is by reducing the number of treatment steps by employing biomarkers that can predict treatment outcome. This study investigated differences between MDD patients and healthy controls in the P3 and N1 component from the event-related potential (ERP) generated in a standard two-tone oddball paradigm. Furthermore, the P3 and N1 are investigated as predictors for treatment outcome to three different antidepressants. In the international Study to Predict Optimized Treatment in Depression (iSPOT-D)--a multi-center, international, randomized, prospective practical trial--1008 MDD participants were randomized to escitalopram, sertraline or venlafaxine-XR. The study also recruited 336 healthy controls. Treatment response and remission were established after eight weeks using the 17-item Hamilton Rating Scale for Depression. P3 and N1 latencies and amplitudes were analyzed using a peak-picking approach and further replicated by using exact low resolution tomography (eLORETA). A reduced P3 was found in MDD patients compared to controls by a peak-picking analysis. This was validated in a temporal global field power analysis. Source density analysis revealed that the difference in cortical activity originated from the posterior cingulate and parahippocampal gyrus. Male non-responders to venlafaxine-XR had significantly smaller N1 amplitudes than responders. This was demonstrated by both analytical methods. Male non-responders to venlafaxine-XR had less activity originating from the left insular cortex. The observed results are discussed from a neural network viewpoint.

Heritability and molecular-genetic basis of the P3 event-related brain potential: a genome-wide association study

P3 amplitude is a candidate endophenotype for disinhibitory psychopathology, psychosis, and other disorders. The present study is a comprehensive analysis of the behavioral- and molecular-genetic basis of P3 amplitude and a P3 genetic factor score in a large community sample (N = 4,211) of adolescent twins and their parents, genotyped for 527,829 single nucleotide polymorphisms (SNPs). Biometric models indicated that as much as 65% of the variance in each measure was due to additive genes. All SNPs in aggregate accounted for approximately 40% to 50% of the heritable variance. However, analyses of individual SNPs did not yield any significant associations. Analyses of individual genes did not confirm previous associations between P3 amplitude and candidate genes but did yield a novel association with myelin expression factor 2 (MYEF2). Main effects of individual variants may be too small to be detected by GWAS without larger samples.

Hippocampal glutamatergic/NMDA receptor functioning in bipolar disorder: A study combining mismatch negativity and proton magnetic resonance spectroscopy

Disturbances in the hippocampal glutamate (Glu)/N-methyl-d-aspartate (NMDA) system have been implicated in the pathophysiology of bipolar disorder (BD). Here we aim to provide a targeted integration of two measures of glutamatergic functioning in BD; the association between mismatch negativity (MMN) and in vivo hippocampal-Glu measured via proton magnetic resonance spectroscopy ((1)H MRS). Participants comprised of 33 patients with BD and 23 matched controls who underwent a two-tone passive, duration deviant MMN paradigm and (1)H MRS. Levels of Glu/creatine (Cr) in the hippocampus were determined. Pearson's correlations were used to determine associations between MMN and Glu/Cr. In controls, MMN amplitude was positively associated with Glu/Cr at the left temporal site. We did not find any significant associations with Glu/Cr and frontocentral MMN nor did we find any significant associations in BD patients. The results provide further insight into the neurophysiology of MMN, with evidence supporting the role of hippocampal-Glu signalling through the NMDA receptor in temporal MMN. Our data also demonstrate that Glu/Cr regulation of MMN is dampened in BD, which may indicate a lack of tightly regulated hippocampal NMDA functioning. These findings provide insight into the underlying basis of glutamatergic transmission disturbances implicated in the disorder.

Alcohol use in bipolar disorder: A neurobiological model to help predict susceptibility, select treatments and attenuate cortical insult

In a series of neurophysiological and neuroimaging studies we investigated the neurobiology related to alcohol use in young people with bipolar disorder. Impairments were identified across frontal and temporal representations of event-related potential and proton magnetic resonance spectroscopy markers; mismatch negativity and in vivo glutathione, respectively. We propose these findings reflect impairments in the N-methyl-D-aspartate receptor and antioxidant capacity. This review seeks to place these findings within the broader literature in the context of two propositions: 1. Pathophysiological impairments in N-methyl-D-aspartate receptor functioning in bipolar disorder contribute to susceptibility toward developing alcohol problems. 2. Alcohol aggravates bipolar disorder neuroprogression via oxidative stress. A neurobiological model that incorporates these propositions is presented, with a focus on the potential for N-methyl-D-aspartate receptor antagonism and glutathione augmentation as potential adjunctive pharmacotherapies to treat the comorbidity. While this review highlights the importance of alcohol monitoring and reduction strategies in the treatment of bipolar disorder, the clinical impact of the proposed model remains limited by the lack of controlled trials of novel pharmacological interventions.

Forecasting psychosis by event-related potentials-systematic review and specific meta-analysis

BACKGROUND

Prediction and prevention of psychosis have become major research topics. Clinical approaches warrant objective biological parameters to enhance validity in prediction of psychosis onset. In this regard, event-related potentials (ERPs) have been identified as promising tools for improving psychosis prediction.

METHODS

Herein, the focus is on sensory gating, mismatch negativity (MMN) and P300, thereby discussing which parameters allow for a timely and valid detection of future converters to psychosis. In a first step, we systematically reviewed the studies that resulted from a search of the MEDLINE database. In a second step, we performed a meta-analysis of those investigations reporting transitions that statistically compared ERPs in converting versus nonconverting subjects.

RESULTS

Sensory gating, MMN, and P300 have been demonstrated to be impaired in subjects clinically at risk of developing a psychotic disorder. In the meta-analysis, duration MMN achieved the highest effect size measures.

CONCLUSIONS

In summary, MMN studies have produced the most convincing results until now, including independent replication of the predictive validity. However, a synopsis of the literature revealed a relative paucity of ERP studies addressing the psychosis risk state. Considering the high clinical relevance of valid psychosis prediction, future research should question for the most informative paradigms and should allow for meta-analytic evaluation with regard to specificity and sensitivity of the most appropriate parameters.

The use of EEG parameters as predictors of drug effects on cognition

It has been shown to be difficult to predict whether cognition-enhancing effects of drugs in animal studies have the same effect in humans. Various issues in translating findings from animal to human studies can be identified. Here we discuss whether EEG could be considered as a possible tool to translate the effects of cognition enhancers across species. Three different aspects of EEG measures are evaluated: frequency bands, event-related potentials, and coherence analysis. On basis of the comparison of these measures between species, and effects of drugs that improve or impair memory performance (mainly cholinergic drugs), it appears that event-related potentials and coherence analyses could be considered as potential translational tools to study cognition-enhancing drug effects in rodents and animals.