The loudness dependence of the auditory evoked potential (LDAEP) as a predictor of the response to escitalopram in patients with generalized anxiety disorder

Relationships between fear of flying, loudness dependence of auditory evoked potentials and frontal alpha asymmetry

Previous research has suggested that fear of flying, which is defined as a situational, specific phobia, could overlap with depressive and anxiety disorders. Whether the neuronal dysfunctions including altered serotonergic activity in the brain and altered neural oscillations observed for depressive and anxiety disorders also overlap with alterations in fear of flying is unclear. Here, thirty-six participants with self-reported fear of flying (FF) and forty-one unaffected participants (NFF) were recruited. The participants completed the Beck Depression Inventory (BDI-II), the State-trait Anxiety Inventory (STAI) and the Fear of Flying Scale (FFS). EEG-recording was conducted during resting-state and during presentation of auditory stimuli with varying loudness levels for analysis of the Loudness Dependence of Auditory Evoked Potentials (LDAEP), which is suggested to be inversely related to central serotonergic activity. Participants with fear of flying did not differ from the control group with regard to BDI-II and STAI data. The LDAEP was higher over F4 electrode in the FF group compared to controls, whereas exploratory analysis suggest that differences between groups were conveyed by female participants. Moreover, the FF group showed relatively higher right frontal alpha activity compared to the control group, whereas no difference in frequency power (alpha, beta and theta) was observed. Thus, this study brought the first hint for reduced serotonergic activity in individuals with fear of flying and relatively higher right frontal activity. Thus, based on the preliminary findings, future research should aim to examine the boundaries with anxiety and depressive disorders and to clarify the distinct neural mechanisms.

Association between the loudness dependence of auditory evoked potential, serotonergic neurotransmission and treatment outcome in patients with depression

Previous studies have suggested that the loudness dependence of auditory evoked potential (LDAEP) is associated with the effectiveness of antidepressant treatment in patients with major depressive disorders (MDD). Furthermore, both LDAEP and the cerebral serotonin 4 receptor (5-HT₄R) density is inversely related to brain serotonin levels. We included 84 patients with MDD and 22 healthy controls to examined the association between LDAEP and treatment response and its association with cerebral 5-HT₄R density. Participants underwent both EEG and 5-HT₄R neuroimaging with [¹¹C]SB207145 PET. Thirty-nine patients with MDD were re-examined after 8 weeks of treatment with selective serotonin reuptake inhibitors/serotonin noradrenaline reuptake inhibitor (SSRI/SNRI). We found that the cortical source of LDAEP was higher in untreated patients with MDD compared to healthy controls (p=0.03). Prior to SSRI/SNRI treatment, subsequent treatment responders had a negative association between LDAEP and depressive symptoms and a positive association between scalp LDAEP and symptom improvement at week 8. This was not found in source LDAEP. In healthy controls, we found a positive correlation between both scalp and source LDAEP and cerebral 5-HT₄R binding but that was not observed in patients with MDD. We did not see any changes in scalp and source LDAEP in response to SSRI/SNRI treatment. These results support a theoretical framework where both LDAEP and cerebral 5-HT₄R are indices of cerebral 5-HT levels in healthy individuals while this association seems to be disrupted in MDD. The combination of the two biomarkers may be useful for stratifying patients with MDD. Clinical Trials Registration:https://clinicaltrials.gov/ct2/show/NCT02869035?draw=1Registration number: NCT0286903.

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.

The Loudness Dependence of Auditory Evoked Potentials is associated with the Symptom Severity and Treatment in Boys with Attention Deficit Hyperactivity Disorder

Objective

Methods

Results

Conclusion

Association between the loudness dependence of auditory evoked potentials and age in patients with schizophrenia and depression

Objective

Although serotonergic dysfunction is significantly associated with major depressive disorder (MDD) and schizophrenia (SCZ), comparison of serotonergic dysfunction in both diseases has received little attention. Serotonin hypotheses have suggested diminished and elevated serotonin activity in MDD and SCZ, respectively. However, the foundations underlying these hypotheses are unclear regarding changes in serotonin neurotransmission in the aging brain. The loudness dependence of auditory evoked potentials (LDAEP) reflects serotonin neurotransmission. The present study compared the LDAEP between patients with SCZ or MDD and healthy controls (HCs). We further examined whether age was correlated with the LDAEP and clinical symptoms.

Methods

This prospective clinical study included 105 patients with SCZ (n = 54) or MDD (n = 51). Additionally, 35 HCs were recruited for this study. The LDAEP was measured on the midline channels via 62 electroencephalography channels.

Results

Patients with SCZ or MDD showed a significantly smaller mean LDAEP than those in HCs. The LDAEP was positively correlated with age in patients with SCZ or MDD.

Conclusions

Changes in central serotonergic activity could be indicated by evaluating the LDAEP in patients with SCZ or MDD. Age-related reductions in serotonergic activity may be screened using the LDAEP in patients with SCZ or MDD.

Does the Loudness Dependence of Auditory Evoked Potential Predict Response to Selective Serotonin Reuptake Inhibitors?: A Meta-analysis

Objective

Loudness of dependence of the auditory evoked potential (LDAEP) is an electroencephalogram-based measure that represents amplitude changes of auditory evoked potentials in primary auditory cortex. Several narrative reviews argued that pre-treatment LDAEP values predict responses to selective serotonin reuptake inhibitors (SSRIs). This study aims to quantify the overall relationship between baseline LDAEP values and treatment response to SSRIs in patients with depression and generalized anxiety disorders, evidenced by clinical symptoms reductions, across multiple studies.

Methods

In our meta-analysis, seven articles with a total sample of 241 patients were included.

Results

Our results showed that stronger baseline LDAEP values predicted favorable response to SSRIs for depression and anxiety, with a moderate effect size.

Conclusion

The current results support the idea that LDAEP is a promising biomarker for SSRIs treatment prediction in patients with depression and generalized anxiety disorder.

The Hypothesis on the Prediction of Treatment Response with Buspirone Augmentation along with Serotonergic Antidepressant in Patients with Major Depressive Disorder Using Loudness Dependence of Auditory Evoked Potentials: Two Cases and Review of the Literature for Evidence

Some studies have shown that augmenting buspirone with antidepressant has similar efficacy as the combination with two antidepressants in patients with major depressive disorder (MDD). Some researchers assume that the antidepressant boosting effect of buspirone is revealed under a poop-out state, which means a phenomenon where some patients having an initial response to an antidepressant may worsen or not improve any more even though they continue treatment because of serotonin depletion. Loudness dependence of auditory evoked potential (LDAEP) is a reliable marker of central serotonergic activity, and is inversely correlated with central serotonergic activity. Thus LDAEP will be a biological marker for prediction of treatment response with buspirone augmentation with SSRI because it can measure central serotonergic activity such as serotonin depletion. Two cases will be introduced and the literature evidence about whether LDAEP can predict the treatment response of buspirone augmentation in patients with MDD will be reviewed.

Neuropsychiatric Disorders as Erratic Attention Regulation - Lessons from Electrophysiology

Attention related electrophysiological waves, such as P300, often deviate from norm in various populations of neuropsychiatric patients. For example, the amplitude is often smaller and the latency is often longer in major depressive disorder, in bipolar disorder and in schizophrenia. On the other hand, in other neuropsychiatric populations, it is often possible to note the opposite phenomena of larger P300 amplitude and shorter latency in comparison with norm, but only for a specific subset of stimuli. This is often reported in various anxiety disorders, substance abuse and various chronic pain syndromes. These findings in the various clinical populations, on their commonalities and differences, are presented in this work. The prevalence of these two types of deviations in the electrophysiological markers of attention, shared by multiple neuropsychiatric populations, raise interesting questions regarding the role of attention deviation and regulation in neuropsychiatry. We present these questions and outline a possible hypothesis in this regard. Furthermore, such potential sensitivity of the attention-related markers to clinical dynamics suggests they could be candidates for monitoring and, potentially, early-sensing of clinical dynamics. Therefore, we discuss the potential usability of such markers.

Serum Levels of Tumor Necrosis Factor-α and Loudness Dependence of Auditory Evoked Potentials at Pretreatment and Posttreatment in Patients with Major Depressive Disorder

Background: Proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), are associated with the pathophysiology of major depressive disorder (MDD). Several studies have reported that increased TNF-α might be associated with tryptophan depletion, which eventually could result in MDD. However, other studies revealed that TNF-α increased serotonin firing in raphe. Therefore, whether TNF-α increases or decreases serotonin activity remains unclear. Here, we aimed to determine the relationship between serum TNF-α level and central serotonergic activity using the loudness dependence of auditory evoked potentials (LDAEP) and standardized low-resolution brain electromagnetic tomography (sLORETA), as well as to evaluate the effects of antidepressants on TNF-α levels. Methods: LDAEP, serum TNF-α level, and depression severity were measured in 64 MDD outpatients pre and post 3 months of treatment. Results: Pretreatment TNF-α levels were negatively correlated with the pretreatment N1 sLORETA-LDAEP, P2 sLORETA-LDAEP, and N1/P2 sLORETA-LDAEP (p < 0.05). In multiple regression analysis for N1/P2 sLORETA-LDAEP, lower N1/P2 sLORETA-LDAEP was significantly related to higher TNF-α (CE = −0.047, p = 0.017) when all subjects were dichotomized based on the median TNF-α level (7.16 pg/mL) into pretreatment low- and high-TNF-α groups. In addition, the pretreatment Beck Depression Inventory, P2 LDAEP, and N1/P2 sLORETA-LDAEP were greater in the high-TNF-α groups than in the low-TNF-α groups (p < 0.05). Moreover, the posttreatment TNF-α level was significantly decreased compared to the pretreatment TNF-α level (z = −2.581, p = 0.01). However, the posttreatment TNF-α levels were not associated with posttreatment LDAEP. Conclusions: Higher TNF-α level is associated with decreased LDAEP, which could indicate compensatory elevation of central serotonin activity in outpatients with MDD, although this effect disappeared and TNF-α level was reduced after three months of antidepressant treatment.

Long-Term Pharmacological Treatments of Anxiety Disorders: An Updated Systematic Review

Many aspects of long-term pharmacological treatments for anxiety disorders (AnxDs) are still debated. We undertook an updated systematic review of long-term pharmacological studies on panic disorder (PD), generalized anxiety disorder (GAD), and social anxiety disorder (SAD). Relevant studies dating from January 1, 2012 to August 31, 2015 were identified using the PubMed database and a review of bibliographies. Of 372 records identified in the search, five studies on PD and 15 on GAD were included in the review. No studies on SAD were found. Our review confirms the usefulness of long-term pharmacological treatments for PD and GAD and suggests that they can provide further improvement over that obtained during short-term therapy. Paroxetine, escitalopram, and clonazepam can be effective for long-term treatment of PD. However, further studies are needed to draw conclusions about the long-term benzodiazepine use in PD, particularly for the possible cognitive side-effects over time. Pregabalin and quetiapine can be effective for long-term treatment of GAD, while preliminary suggestions emerged for agomelatine and vortioxetine. We did not find any evidence for determining the optimal length and/or dosage of medications to minimize the relapse risk. Few investigations have attempted to identify potential predictors of long-term treatment response. Personalized treatments for AnxDs can be implemented using predictive tools to explore those factors affecting treatment response/tolerability heterogeneity, including neurobiological functions/clinical profiles, comorbidity, biomarkers, and genetic features, and to tailor medications according to each patient's unique features.

Influence of the 5-HT3A Receptor Gene Polymorphism and Childhood Sexual Trauma on Central Serotonin Activity

Background

Gene-environment interactions are important for understanding alterations in human brain function. The loudness dependence of auditory evoked potential (LDAEP) is known to reflect central serotonergic activity. Single nucleotide polymorphisms (SNPs) in the 5-HT3A serotonin receptor gene are associated with psychiatric disorders. This study aimed to investigate the effect between 5-HT3A receptor gene polymorphisms and childhood sexual trauma on the LDAEP as an electrophysiological marker in healthy subjects.

Methods

A total of 206 healthy subjects were recruited and evaluated using the childhood trauma questionnaire (CTQ) and hospital anxiety and depression scale (HADS). Peak-to-peak N1/P2 was measured at five stimulus intensities, and the LDAEP was calculated as the linear-regression slope. In addition, the rs1062613 SNPs of 5-HT3A (CC, CT, and TT) were analyzed in healthy subjects.

Results

There was a significant interaction between scores on the CTQ-sexual abuse subscale and 5-HT3A genotype on the LDAEP. Subjects with the CC polymorphism had a significantly higher LDEAP than T carriers in the sexually abused group. In addition, CC genotype subjects in the sexually abused group showed a significantly higher LDAEP compared with CC genotype subjects in the non-sexually abused group.

Conclusions

Our findings suggest that people with the CC polymorphism of the 5-HT3A gene have a greater risk of developing mental health problems if they have experienced childhood sexual abuse, possibly due to low central serotonin activity. Conversely, the T polymorphism may be protective against any central serotonergic changes following childhood sexual trauma.

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.

Differences in central serotoninergic transmission among patients with recent onset, sub-chronic, and chronic schizophrenia as assessed by the loudness dependence of auditory evoked potentials

Previous research has shown that abnormalities in serotonin systems are associated with schizophrenia. The loudness dependence of auditory evoked potentials (LDAEP) has been used as a metric of central serotonin activity. The present study aimed to evaluate LDAEP in patients with schizophrenia of differing chronicity. Sixty-four patients with schizophrenia and 50 healthy controls were enrolled in this study. LDAEP and psychometric ratings, such as the positive and negative syndrome scale (PANSS), were measured. The cohort was stratified into three subgroups according to the duration of illness: recent onset (<2years, n=21), sub-chronic (2-9years, n=28), and chronic (≥10years, n=15) groups. The LDAEP differed significantly among the three groups. A post-hoc analysis (Bonferroni) demonstrated that the LDAEP differed significantly between the recent onset and chronic groups (p=0.029), and between the healthy control and chronic groups (p=0.008). Age, sex, dosage of antipsychotics, and smoking did not significantly affect the group differences. In the correlation analysis, there was a significant correlation of LDAEP values with illness duration (r=-0.259, p=0.045). The present study verifies that the LDAEP is related to the duration of illness in patients with schizophrenia. This suggests that central serotonin neurotransmission is changeable, and it may depend on the chronicity of schizophrenia pathology.

Prediction of long-term treatment response to selective serotonin reuptake inhibitors (SSRIs) using scalp and source loudness dependence of auditory evoked potentials (LDAEP) analysis in patients with major depressive disorder

BACKGROUND

Animal and clinical studies have demonstrated that the loudness dependence of auditory evoked potentials (LDAEP) is inversely related to central serotonergic activity, with a high LDAEP reflecting weak serotonergic neurotransmission and vice versa, though the findings in humans have been less consistent. In addition, a high pretreatment LDAEP appears to predict a favorable response to antidepressant treatments that augment the actions of serotonin. The aim of this study was to test whether the baseline LDAEP is correlated with response to long-term maintenance treatment in patients with major depressive disorder (MDD).

METHODS

Scalp N1, P2 and N1/P2 LDAEP and standardized low resolution brain electromagnetic tomography-localized N1, P2, and N1/P2 LDAEP were evaluated in 41 MDD patients before and after they received antidepressant treatment (escitalopram (n = 32, 10.0 ± 4.0 mg/day), sertraline (n = 7, 78.6 ± 26.7 mg/day), and paroxetine controlled-release formulation (n = 2, 18.8 ± 8.8 mg/day)) for more than 12 weeks. A treatment response was defined as a reduction in the Beck Depression Inventory (BDI) score of >50% between baseline and follow-up.

RESULTS

The responders had higher baseline scalp P2 and N1/P2 LDAEP than nonresponders (p = 0.017; p = 0.036). In addition, changes in total BDI score between baseline and follow-up were larger in subjects with a high baseline N1/P2 LDAEP than those with a low baseline N1/P2 LDAEP (p = 0.009). There were significantly more responders in the high-LDAEP group than in the low-LDAEP group (p = 0.041).

CONCLUSIONS

The findings of this study reveal that a high baseline LDAEP is associated with a clinical response to long-term antidepressant treatment.

The association between serum lipid levels, suicide ideation, and central serotonergic activity in patients with major depressive disorder

BACKGROUND

There is some evidence that low lipid levels cause suicide in depressed patients. The purpose of this study was to identify whether low serum lipid levels are associated with suicide ideation or are correlated with central serotonin function.

METHODS

Auditory processing for the loudness dependence of auditory evoked potentials (LDAEP) was measured in 73 outpatients with major depressive disorder. The Hamilton Depression Rating Scale (HAMD) and the Beck Depression Inventory (BDI) were administered on the same day as measurement of the LDAEP. In addition, serum levels of total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglyceride (TG) levels were measured. All subjects had received antidepressant monotherapy.

RESULTS

The depressed subjects were divided into those with and without suicide ideation according to the score for HAMD item 3 or BDI item 9. TG levels differed significantly between the two groups, whereas body mass index (BMI), total cholesterol, LDL, HDL, and LDAEP did not. The scores for HAMD item 3 and BDI item 9 were negatively correlated with TG levels (p=0.045 and 0.026, respectively). The LDAEP was negatively correlated with TG levels (p=0.012). Although there was tendency toward a negative correlation between the LDAEP and serum LDL, it did not reach statistical significance (p=0.068).

LIMITATIONS

The cross-sectional design of this study means that baseline serum lipid levels were not measured.

CONCLUSION

The findings of this study revealed a relationship between TG and suicide ideation that is independent of both BMI and body weight. Furthermore, serum lipid levels were associated with central serotonergic activity, as assessed using the LDAEP.

Neural structures, functioning and connectivity in Generalized Anxiety Disorder and interaction with neuroendocrine systems: a systematic review

BACKGROUND

Research on the neurobiological basis of Generalized Anxiety Disorder (GAD) has considerably expanded in recent years. However, many studies investigated different domains and used different methods and paradigms. Therefore, this review aims to integrate the findings to date and to identify the core correlates of neurobiological underpinnings of GAD discovered so far.

METHODS

We conducted a systematic review of original papers investigating neural correlates, connectivity, or structural changes as well as reporting changes in the serotonergic system, noradrenergic system and cortisol levels in DSM-IV-defined GAD samples until December 2013.

RESULTS

Studies have identified abnormal amygdala and prefrontal cortex activation in patients and decreased functional connectivity between these areas. Furthermore, studies showed increased gray matter volume and decreased structural connectivity between these structures. Neuroendocrine findings are less consistent, but increased reactivity of the noradrenergic system and perpetuations in the cortisol secretion have been reported.

LIMITATIONS

Only studies on DSM-IV defined Generalized Anxiety Disorder which employed a group comparison were included.

CONCLUSIONS

Current research suggests a distinct set of neurobiological alterations in Generalized Anxiety Disorder. However, future research on the interaction between these structures and systems and on the specificity of these findings in relation to other mental disorders is urgently needed.

Serum BDNF levels in relation to illness severity, suicide attempts, and central serotonin activity in patients with major depressive disorder: a pilot study

The aim of this study was to test the hypothesis that serum levels of brain-derived neurotrophic factor (BDNF) are correlated with the loudness dependence of auditory evoked potentials (LDAEP). The question of whether there is a difference in BDNF levels between depressive patients according to their illness severity, history of suicide attempts, and central serotonin activity was also addressed. A sample of 51 patients who met the criteria for major depressive disorder following diagnosis using axis I of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders – text revision comprised the study subjects. The patients were stratified into two subgroups based on their illness severity, history of suicide attempts, and their LDAEP values. The LDAEP was evaluated by measuring the auditory event-related potentials, and serum BDNF was measured using blood sampling before beginning medication with serotonergic agents. There was no difference in serum BDNF levels between the two patient subgroups. The subgroup with moderate-to-severe depression (n = 16) was reanalyzed after stratifying it into two subgroups according to LDAEP and BDNF values (dichotomized at the medians into low and high). The high-LDAEP subgroup had higher serum BDNF levels and total Barratt Impulsiveness Scale score than the low-LDAEP subgroup (p = 0.03 and 0.036, respectively). Serum BDNF levels were positively correlated with LDAEP and total Beck Hopelessness Scale (BHS) score (r = 0.56, p = 0.025, and r = 0.59, p = 0.016, respectively). The high-BDNF subgroup had a higher LDAEP and total BHS score than the low-BDNF subgroup (p = 0.046 and p = 0.011, respectively). This is the first study to demonstrate a relationship between the BDNF level and LDAEP in Asian depressive patients. Intriguingly, the high-BDNF subgroup (divided according to illness severity) exhibited a more severe psychopathology on some psychometric rating scales, a finding that conflicts with previous results.

Relationship between SSRI-induced sexual dysfunction and central serotonergic activity based on the loudness dependence of auditory evoked potentials

RATIONALE

It has been hypothesized that selective serotonin reuptake inhibitor (SSRI)-induced sexual dysfunction can occur more frequently in patients with higher central serotonergic activity, and that this higher serotonergic activity can induce inhibition of sexual desire, ejaculation, and orgasm. Thus, the aim of this study was to determine the relationship between SSRI-induced sexual dysfunction and increased serotonin.

METHOD

Event-related potentials for the loudness dependence of auditory evoked potentials (LDAEP) were measured in 46 patients at a single time point. The subjects' scores on the Hamilton Depression Rating Scale and Antidepressant Side-Effect Checklist were also determined by the investigators at the same time point. All patients had received SSRI monotherapy.

RESULTS

Overall, 37 % (17/46) of the patients experienced some form of SSRI-induced sexual dysfunction: lack of sexual desire, impotence, orgasm, and menstrual abnormality or mastalgia were experienced by 21.7, 8.3, 15.2, and 20.6 % of the patients, respectively. The subjects were thus divided into two groups-those with and without sexual dysfunction-and their data were compared. There was a tendency for the LDAEP to be lower in the group with sexual dysfunction (1.04 ± 0.77 μV) than the group without sexual dysfunction (1.45 ± 0.86 μV), although the difference was not statistically significant (p = 0.086). Furthermore, the distribution of the frequency of SSRI-induced sexual dysfunction differed marginally significantly between patients with low and high LDAEP, dichotomized according to the median LDAEP on the Cz electrode (χ (2) = 3.664, p = 0.056).

CONCLUSIONS

There was a relatively high frequency of SSRI-induced sexual dysfunction in patients with low LDAEP.

Clinical Usefulness of Loudness Dependence of Auditory Evoked Potentials (LDAEP) in Patients with Bipolar Disorder

While it has been reported previously that the loudness dependence of auditory evoked potentials (LDAEP) is a putative biological marker or a predictor of treatment response, there have been few studies of LDAEP in bipolar disorder. However, a recent study by Park and colleagues raised the possibility that the LDAEP could be useful as a biological marker of bipolar disorder. They found that the LDAEP was significantly higher in normal controls than in patients with either bipolar disorder or schizophrenia. Lee and colleagues also examined the LDAEP in bipolar disorder and normal controls, and found that it differed according to the bipolar phase, being significantly higher in cases of euthymic bipolar disorder, bipolar depression, and bipolar mania. With regard to treatment response, early clinical findings were that a higher LDAEP and a stronger intensity dependence of visual evoked potentials were related to a favorable response to lithium treatment. Juckel and colleagues recently demonstrated that the pretreatment LDAEP could be a predictor of successful prophylactic lithium treatment. The present article reviews the literature in order to determine whether the LDAEP can be used as a biological marker or a predictor of treatment response in patients with bipolar disorder and of manic switch or treatment resistance in patients with major depressive episode(s).

Electrocortical features of depression and their clinical utility in assessing antidepressant treatment outcome

Major depressive disorder (MDD) is primarily characterized by decreased affect and accompanying behavioural consequences, but it is also associated with cognitive dysfunction. Assessment of electroencephalographic (EEG) activity and associated event-related potentials (ERPs; derived from averaged EEG activity in response to a stimulus) in the context of MDD has provided insights into the electrocortical abnormalities associated with the disorder. Importantly, EEG and ERPs also have emerged as candidates for predicting and optimizing antidepressant (AD) treatment outcome. This is critical in light of relatively low remission rates or a limited response to initial AD interventions. In contrast to other neuroimaging approaches, EEG and ERPs may be superior for predicting and monitoring AD response, as electrocortical measures are relatively inexpensive, easy to use, and have excellent temporal (that is, millisecond) resolution, enabling fine-grained assessment of basic cognitive and emotive processes. This review aims to highlight the most consistently noted EEG and ERP features in MDD, which may one day assist with diagnostic confirmation, as well as the potential clinical utility of specific electrocortical measures in aiding with response prediction.

Response prediction to antidepressants using scalp and source-localized loudness dependence of auditory evoked potential (LDAEP) slopes

The loudness-dependence of the auditory evoked potential (LDAEP) slope may be inversely related to serotonin (5-HT) neurotransmission. Thus, steep LDAEPs tend to predict a positive response to selective serotonin reuptake inhibitor (SSRI) antidepressants, which augment 5-HT. However, LDAEPs also predict outcome to antidepressants indirectly altering 5-HT (e.g. bupropion). Hence, the LDAEP's predicative specificity and sensitivity to antidepressant response/outcome remains elusive. Scalp N1, P2 and N1/P2 LDAEP slopes and standardized low resolution brain electromagnetic tomography (sLORETA)-localized N1 and P2 LDAEP slopes were assessed in depressed individuals (N=51) at baseline, 1 and 12 weeks post-treatment with one of three antidepressant regimens [escitalopram (ESC)+bupropion (BUP), ESC or BUP]. Clinical response was greatest with ESC+BUP at week 1. Treatment responders had steep N1 sLORETA-LDAEP baseline slopes while non-responders had shallow ones. P2 sLORETA-LDAEP slope increases at 1 week existed in responders; decreases were noted in non-responders. Exploratory analyses indicated that more BUP and ESC responders versus non-responders had steep baseline N1 sLORETA-LDAEP slopes. Additionally, slight decreases in scalp P2 LDAEP by week 1 existed for ESC treatment, while slope increases existed with ESC+BUP treatment. Only baseline N1 sLORETA-LDAEP discriminated treatment responders/non-responders. This work confirms that certain LDAEP measures are associated with treatment outcome and appear to be differentially modulated with varying antidepressant drug regimens, though this should be confirmed using larger samples.

Can the Loudness Dependence of Auditory Evoked Potentials and Suicidality Be Used to Differentiate between Depressive Patients with and without Bipolarity

OBJECTIVE

This study aimed to test the hypothesis that the loudness dependence of auditory evoked potentials (LDAEP) can be used to predict the presence of bipolarity in patients with major depressive episodes.

METHODS

A cohort of 61 patients who met the criteria for major depressive disorder (MDD) following diagnosis using Axis I of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders-text revision, and who had no history of hypomanic or manic episodes was included in this study. The patients were stratified into two subgroups based on whether or not they achieved a positive score for the Korean versions of the Mood Disorder Questionnaire (K-MDQ). The LDAEP was evaluated by measuring the auditory event-related potentials before beginning medication with serotonergic agents.

RESULTS

The Barratt Impulsiveness Scale (BIS) score was also higher for the positive screening group (81.24±11.87) than for the negative screening group (73.30±14.92; p=0.039, independent t-test). However, the LDAEP, Beck Depression Inventory, Hamilton Depression Rating Scale, Beck Hopelessness Scale (BHS), and Hamilton Anxiety Scale scores did not differ significantly between them. When binary logistic regression analysis was carried, the relationship between the positive or negative subgroups for K-MDQ and BIS or Beck Scale for Suicidal Ideation (BSS) score was also significant (respectively, p=0.017, p=0.038).

CONCLUSION

We found that LDAEP was not significantly different between depressive patients with and without bipolarity. However, our study has revealed the difference between two subgroups based on whether or not they achieved a positive score for the K-MDQ in BIS or BSS score.

Association between BDNF gene polymorphisms and serotonergic activity using loudness dependence of auditory evoked potentials in healthy subjects

It has been proposed that the loudness dependence of auditory evoked potentials (LDAEP) would be a reliable indicator of central serotonin system activity in humans. Serotonin levels and turnover are also increased by brain-derived neurotrophic factor (BDNF). The aim of the present study was to determine whether there is an association between genetic polymorphisms of BDNF and the LDAEP in healthy Korean young adults. The cohort comprised 211 mentally and physically healthy subjects, all of whom were nonsmokers (111 males, 100 females; age: 20∼32 years). To avoid hormonal effects, the LDAEP was measured during days 2–5 after the beginning of menstruation for female subjects. In addition, BDNF polymorphisms (rs6265, rs2030324, and rs1491850) were genotyped. The strength of the LDAEP differed significantly among the BDNF genotype groups. Furthermore, the distribution of genotypic frequencies differed significantly between subjects with high and low LDAEPs. In particular, subjects with the Val/Met (A/G) genotype for rs6265, the T/T genotype for rs2030324, or the C/C genotype for rs1491850 had a higher LDAEP, indicating lower central serotonergic activity. A low LDAEP was more prevalent than a high LDAEP among those with the C-T haplotype (C genotype for rs2030424 and T genotype for rs1491850). Our results concur with previous findings on BDNF polymorphisms and serotonergic drug responses in psychiatric disorder patients. The present results suggest the possibility that BDNF polymorphisms and LDAEP patterns can predict altered serotonergic activity.

Clinical characteristics associated with different strengths of loudness dependence of auditory evoked potentials (LDAEP) in major depressive disorder

Loudness dependence of auditory evoked potentials (LDAEP), also called as intensity dependence of auditory evoked potentials (IDAP), has been proposed as a potential marker for central serotonergic tone and has been noticed for its possible clinical implications in depression. However, its distributions in major depressive disorder (MDD) and factors affecting it are largely unknown. In this study, we examined its distribution and relationships with various demographic and clinical variables in MDD patients. In 143 MDD patients, the LDAEP was measured using five intensities of auditory stimulus. The influences of ten independent variables (age, gender, education years, marital status, psychiatric family history, age of onset, suicide attempt history, depression severity, later augmentation of mood stabilizer, and smoking status) on the LDAEP strength were examined using univariate analyses and data mining method. The mean (±S.D.) LDAEP was 0.90 (±0.73)μV/10dB (-0.78-3.83μV/10dB). Female gender, smoking, and being married were consistently associated with a weaker LDAEP. In the pathway model, sequential combination of being male, living alone, and older age predicted the strongest LDAEP, whereas female gender, older age, and smoking predicted the weakest LDAEP. These variables need to be considered when interpreting the LDAEP.

The loudness dependence of auditory evoked potentials and effects of psychopathology and psychopharmacotherapy in psychiatric inpatients

OBJECTIVE

Many studies have provided evidence for the loudness dependence of auditory evoked potentials (LDAEP) as a marker for central serotonergic activity but remained inconclusive for its suitability in clinical use.

METHODS

A cross-sectional sample of 162 psychiatric inpatients (major depression N = 86, bipolar disorder N = 12, schizophrenia N = 50, and schizoaffective disorder N = 14) and 40 healthy subjects was retrospectively examined for LDAEP and effects of psychopathology and psychopharmacology.

RESULTS

The LDAEP was weaker in patients with affective disorders than in healthy subjects but did not differentiate between the total patient sample and healthy controls. LDAEP correlated significantly with dimensions of the Brief Symptom Inventory in the total patient sample (depression, paranoid ideation, psychoticism, Global Symptom Index, and Positive Symptom Distress Index), in patients with affective disorders (depression) and with schizophrenia spectrum disorders (depression, psychoticism, Global Symptom Index, and Positive Symptom Distress Index). Similar correlations were found in depressed patients with a single noradrenergic and specific serotonergic antidepressant or serotonin-norepinephrine reuptake inhibitor. There was a negative correlation between dosage of typical antipsychotics and LDAEP. Hypnotics generally led to a lower LDAEP.

CONCLUSION

The LDAEP in patients is related to severity of psychopathologic syndromes irrespective of diagnosis. Chronic psychopharmacologic treatment may also differentially modulate the LDAEP, but longitudinal studies are needed.

Serotonergic dysfunction in patients with bipolar disorder assessed by the loudness dependence of the auditory evoked potential

OBJECTIVE

The loudness dependence of the auditory evoked potential (LDAEP) is suggested to be a marker of serotonin system function. This study explored the LDAEP of multiple mood statuses (depression, mania, and euthymia) and its clinical implication in bipolar disorder patients.

METHODS

A total of 89 subjects, comprising 35 patients with bipolar disorder, 32 patients with schizophrenia, and 22 healthy controls were evaluated. The bipolar disorder cases comprised 10 depressed patients, 15 patients with mania, and 10 euthymic patients. The N1/P2 peak-to-peak amplitudes were measured at 5 stimulus intensities, and the LDAEP was calculated as the slope of the linear regression. Both cortical and source LDAEP values were calculated.

RESULTS

LDAEP varied according to mood statuses, and was significantly stronger in cases of euthymia, depression, and mania. Cortical LDAEP was significantly stronger in patients with bipolar euthymia compared with schizophrenia, stronger in bipolar depression than in schizophrenia, stronger in healthy controls than in schizophrenia patients, and stronger in healthy controls than in patients with bipolar mania. Source LDAEP was significantly stronger in patients with bipolar euthymia, bipolar depression, and bipolar mania compared with schizophrenia, stronger in bipolar euthymia than in bipolar mania. Psychotic features weakened the source LDAEP relative to nonpsychotic features. The severity of the depressive symptom was negatively correlated with source LDAEP.

CONCLUSION

These findings suggest that the serotonin activity of patients with bipolar disorder may vary according to mood status. A longitudinal follow-up study should be pursued using drug-naive subjects.

Examination of the effect of acute levodopa administration on the loudness dependence of auditory evoked potentials (LDAEP) in humans

RATIONALE

The loudness dependence of the auditory evoked potential (LDAEP) is considered a noninvasive in vivo marker of central serotonergic functioning in humans. Nevertheless, results of genetic association studies point towards a modulation of this biomarker by dopaminergic neurotransmission.

OBJECTIVE

We examined the effect of dopaminergic modulation on the LDAEP using L-3,4-dihydroxyphenylalanine (levodopa)/benserazide (Madopar®) as a challenge agent in healthy volunteers.

METHODS

A double-blind placebo-controlled challenge design was chosen. Forty-two healthy participants (21 females and 21 males) underwent two LDAEP measurements, following a baseline LDAEP measurement either placebo or levodopa (levodopa 200 mg/benserazide 50 mg) were given orally. Changes in the amplitude and dipole source activity of the N1/P2 intensities (60, 70, 80, 90, and 100 dB) were analyzed.

RESULTS

The participants of neither the levodopa nor the placebo group showed any significant LDAEP alterations compared to the baseline measurement. The test-retest reliability (Cronbachs Alpha) between baseline and intervention was 0.966 in the verum group and 0.759 in the placebo group, respectively.

CONCLUSIONS

The administration of levodopa showed no effect on the LDAEP. These findings are in line with other trials using dopamine receptor agonists.

Usefulness of LDAEP to predict tolerability to SSRIs in major depressive disorder: a case report

We report here a patient with major depressive disorder who experienced severe adverse effects after the administration of SSRIs (serotonin selective reuptake inhibitors) without improvement of his depressive symptoms. These adverse effects disappeared and his depressive symptoms improved after discontinuation of the SSRIs and the administration of tianeptine. The patient exhibited a low value for the loudness dependent of auditory evoked potentials (LDAEP) -0.14 at baseline, which means that his central serotonergic neurotransmission was already highly active. We assumed that it was this high serotonergic activity that rendered him unresponsive to SSRIs, and brought on him the adverse effects, and that the tianeptine was effective due to the lack of serotonin reuptake inhibitory action. Thus, we suggest that LDAEP can be used to predict an individual patient's tolerability and clinical response to SSRIs in major depression.

Is serotonergic function associated with the antidepressant effects of modified-electroconvulsive therapy?

BACKGROUND

The effect of modified-electroconvulsive therapy (m-ECT) on central serotonergic function has not been sufficiently investigated. The aim of the present study is to investigate this effect via the neuroendocrine challenge test.

METHODS

Sixteen inpatients (9 men and 7 women) with major depressive disorder who were receiving m-ECT at our university hospital were recruited. A neuroendocrine challenge test to estimate central serotonergic function was performed both before and after m-ECT treatment.

RESULTS

On the whole, depressive symptoms significantly improved, but the improvement was not associated with changes in serotonergic function.

LIMITATIONS

The study was open-labeled and performed with a small number of subjects and no control group.

CONCLUSION

Serotonergic function may not be associated with the antidepressant effects of ECT.