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

Difference between Quantitative Electroencephalography, Loudness Dependence of Auditory Evoked Potential, and Mismatch Negativity between a Manic and a Depressive Episode in a Single Bipolar Patient with Mixed Features

This study compares the changes in Quantitative electroencephalography (QEEG), loudness dependence of auditory evoked potentials (LDAEP), and mismatch negativity (MMN) in the case of bipolar depression, mania, and euthymia in a single patient. the characteristic of QEEG in this patient with mixed depression was an increase in alpha; in mixed mania, there was little increase in alpha, and the decrease in delta, theta, and beta was noticeable. LDAEP increased more in the manic phase than in the depressive phase. In contrast, MMN decreased more in the manic than in the depressive phase. After remission of mania, QEEG, LDAEP, and MMN were re-measured. Compared with the manic phase, the decrease in delta, theta, and beta bands in the occipital, temporal, and parietal lobes improved significantly. The LDAEP decreased from LDAEP 1.67 to 0.97. However, in spite of the euthymic phase, MMN amplitude showed a further decrease, from -1.7 to -0.9. In conclusion, using QEEG, LDAEP, and MMN can help clinicians predict a patient's bipolar state and evaluate serotonin intensity and cognitive function, enabling customized treatment. However, there are still few consistent research results; therefore, there is a need to utilize a larger sample size.

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.

Neurovascular coupling during auditory stimulation: event-related potentials and fNIRS hemodynamic

Intensity-dependent amplitude changes (IDAP) have been extensively studied using event-related potentials (ERPs) and have been linked to several psychiatric disorders. This study aims to explore the application of functional near-infrared spectroscopy (fNIRS) in IDAP paradigms, which related to ERPs could indicate the existence of neurovascular coupling. Thirty-three and thirty-one subjects participated in two experiments, respectively. The first experiment consisted of the presentation of three-tone intensities (77.9 dB, 84.5 dB, and 89.5 dB) lasting 500 ms, each type randomly presented 54 times, while the second experiment consisted of the presentation of five-tone intensities (70.9 dB, 77.9 dB, 84.5 dB, 89.5 dB, and 94.5 dB) in trains of 8 tones lasting 70 ms each tone, the trains were presented 20 times. EEG was used to measure ERP components: N1, P2, and N1-P2 peak-to-peak amplitude. fNIRS allowed the analysis of the hemodynamic activity in the auditory, visual, and prefrontal cortices. The results showed an increase in N1, P2, and N1-P2 peak-to-peak amplitude with auditory intensity. Similarly, oxyhemoglobin and deoxyhemoglobin concentrations showed amplitude increases and decreases, respectively, with auditory intensity in the auditory and prefrontal cortices. Spearman correlation analysis showed a relationship between the left auditory cortex with N1 amplitude, and the right dorsolateral cortex with P2 amplitude, specifically for deoxyhemoglobin concentrations. These findings suggest that there is a brain response to auditory intensity changes that can be obtained by EEG and fNIRS, supporting the neurovascular coupling process. Overall, this study enhances our understanding of fNIRS application in auditory paradigms and highlights its potential as a complementary technique to ERPs.

Endocannabinergic modulation of central serotonergic activity in healthy human volunteers

BACKGROUND

The serotonergic and the endocannabinoid system are involved in the etiology of depression. Depressive patients exhibit low serotonergic activity and decreased level of the endocannabinoids anandamide (AEA) and 2-arachidonylglycerol (2AG). Since the cannabinoid (CB) 1 receptor is activated by endogenous ligands such as AEA and 2AG, whose concentration are controlled by the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, respectively, we investigated the effects on serotonergic utilization. In this study, we investigated the impact of the rs1049353 single-nucleotide polymorphism (SNP) of the cannabinoid receptor 1 (CNR1) gene, which codes the endocannabinoid CB1 receptor, and the rs324420 SNP of the FAAH gene on the serotonergic and endocannabinoid system in 59 healthy volunteers.

METHODS

Serotonergic activity was measured by loudness dependence of auditory-evoked potentials (LDAEP). Plasma concentrations of AEA, 2AG and its inactive isomer 1AG were determined by mass spectrometry. Genotyping of two SNPs (rs1049353, rs344420) was conducted by polymerase chain reaction (PCR) and differential enzymatic analysis with the PCR restriction fragment length polymorphism method.

RESULTS

Genotype distributions by serotonergic activity or endocannabinoid concentration showed no differences. However, after detailed consideration of the CNR1-A-allele-carriers, a reduced AEA (A-allele-carrier M = 0.66, SD = 0.24; GG genotype M = 0.72, SD = 0.24) and 2AG (A-allele-carriers M = 0.70, SD = 0.33; GG genotype M = 1.03, SD = 0.83) plasma concentration and an association between the serotonergic activity and the concentrations of AEA and 2AG has been observed.

CONCLUSIONS

Our results suggest that carriers of the CNR1-A allele may be more susceptible to developing depression.

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.

Investigation of the Serotonergic Activity and the Serotonin Content in Serum and Platelet, and the Possible Role of the Serotonin Transporter in Patients with Depression

According to the monoamine hypothesis, the development of depression is associated with dysfunctions of the serotonergic system. Alterations in the serotonin transporter gene (5-HTTLPR), the serotonergic activity in the brain, and the content of serotonin (5-HT) have been related to depression and were examined separately by previous studies. This study investigates these parameters in 89 depressed patients and 89 healthy participants. We investigated the serotonergic activity measured by the loudness dependence of auditory evoked potentials (LDAEP). In addition to the examination of the serotonin content (serum and platelet), enzyme-linked immunosorbent assays (ELISA) were used and 5-HTTLPR genotypes were analyzed. We observed a lower serotonin content in patients compared to healthy participants. Further, we noticed a correlation between anxiety and depression-associated symptoms with serotonergic activity. Patients treated with SSRI/SNRI showed decreased contents of serum serotonin compared to patients without any psychotropic medication or other psychotropic medications. Since the serotonergic activity, peripheral serotonin content, and 5-HTTLPR were unrelated, the results suggest independent alterations of central and peripheral serotonergic systems in depression. In line with this finding, serotonergic activity was related to anxiety and depression symptoms. Furthermore, the applied medication seems to influence serum serotonin content in patients with depression.

How Childhood Maltreatment Is Related to Suicidality, Bipolarity and Central Serotonergic Activity in Patients with Major Depressive Disorder: A Cross-Sectional Pilot Study

OBJECTIVE

The aims of this study were to determine whether childhood maltreatment contributes to the occurrence of major depressive disorder (MDD) with bipolarity, and whether there is a relationship between central serotonergic activity, as assessed using loudness dependence of auditory evoked potentials (LDAEP), and childhood maltreatment.

METHODS

Thirty-five MDD patients were stratified according to the presence or absence of childhood trauma into two subgroups, childhood trauma (CT) and no childhood trauma (NCT), using the Korean version of the Childhood Trauma Questionnaire (K-CTQ). The CT group was subjected to further analysis. Several psychometric ratings were also applied. In addition, auditory processing for the loudness dependence of auditory evoked potentials (LDAEP), which was used as a marker of serotonergic activity, was measured before beginning medication.

RESULTS

There was a significant difference in total Korean Bipolar Spectrum Disorder Scale score between the CT and NCT groups (t=-2.14, p=0.04). The total K-CTQ score was positively correlated with the total Beck Scale for Suicidal Ideation (BSS) score (r=0.36, p=0.036). In particular, emotional abuse was positively correlated with the total Barratt Impulsiveness Scale (r=0.38, p=0.026), BSS (r=0.38, p=0.025), and Hamilton Depression Rating Scale (HAMD) (r=0.36, p=0.035) scores. There was also a positive correlation between LDAEP and total Hypomania Personality Scale (r=0.49, p=0.02) and HAMD (r=0.58, p=0.004) scores within CT group.

CONCLUSION

The findings of this study support that there is a relationship between childhood maltreatment and bipolarity in patients with MDD.

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.

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.

Relationship between Serotonergic Dysfunction Based on Loudness Dependence of Auditory-Evoked Potentials and Suicide in Patients with Major Depressive Disorder

The relationship between suicidality and the loudness dependence of auditory-evoked potentials (LDAEP) remains controversial. This article reviews the literature related to the LDAEP and suicide in patients with major depressive disorder, and suggests future research directions. Serotonergic dysfunction in suicidality seems to be more complicated than was originally thought. Studies of suicide based on the LDAEP have produced controversial results, but it is possible that these are due to differences in study designs and the smallness of samples. For example, some studies have evaluated suicide ideation and the LDAEP, while others have evaluated suicide attempts and the LDAEP. Furthermore, some of the latter studies enrolled acute suicide attempters, while others enrolled those with the history of previous suicide attempts, irrespective of whether these were acute or chronic. Thus, a more robust study design is needed in future studies, for example by evaluating the LDAEP immediately after a suicide attempt rather than in those with a history of suicide attempts and suicide ideation in order to reduce bias. Moreover, genuine suicide attempt, self-injurious behaviors, and faked suicide attempt need to be discriminated in the future.

Clinical implications of loudness dependence of auditory evoked potentials in patients with atypical depression

OBJECTIVES

The loudness dependence of auditory evoked potentials (LDAEP) has been proposed as a useful biomarker of serotonin activity, and the LDAEP value is low in patients with melancholic depression. In this study, we evaluated LDAEP levels in patients with atypical depression.

METHODS

We recruited 53 patients with atypical depression and 68 patients with non-atypical depression. Subjects were evaluated by the Atypical Depression Diagnostic Scale (ADDS), Hamilton Rating Scale for Depression (HAMD), Hamilton Rating Scale for Anxiety (HAMA), Beck Scale for Suicidal Ideation (BSI), Behavioral Inhibition System and Behavioral Activation System (BIS/BAS) scales, and Hypomanic Personality Scale (HPS). To determine LDAEP, the peak-to-peak N1/P2 was measured at five stimulus intensities and the LDAEP was calculated as the linear-regression slope.

RESULTS

Patients with atypical depression had stronger LDAEP values and higher BAS and HPS scores than those with non-atypical depression. LDAEP showed a pattern of gradual decrease according to ADDS score hierarchy in patients with major depressive disorder. In the atypical depression group, LDAEP showed significant negative correlation with the BSI score and significant positive correlation with BAS score. In the non-atypical depression group, LDAEP did not show any significant correlations with the scores of psychological scales.

CONCLUSIONS

Our results suggest that there is a relatively deficient serotonergic activity in patients with atypical depression and that LDAEP reflects mood reactivity. The transient drop of serotonergic activity induced by mood vulnerability might contribute to suicidal tendencies in patients with atypical depression.

Loudness modulation after transient and permanent hearing loss: implications for tinnitus and hyperacusis

Loudness is the primary perceptual correlate of sound intensity. The relationship between sound intensity and loudness is not fixed, and can be modified by short-term sound deprivation or stimulation. Deprivation increases sound sensitivity, whereas stimulation decreases it. We review the effects of short-term auditory deprivation and stimulation on the auditory central nervous system of humans and animals, and we extend the discussion to permanent auditory deprivation (hearing loss) and auditory pathologies of loudness perception. Although there is sufficient evidence to conclude that loudness can be modulated in normal hearing listeners by temporary sound deprivation and stimulation, evidence is scanter for the hearing-impaired listeners. In addition, cortical effects of sound deprivation and stimulation in humans, which may correlate with loudness coding, are still largely unknown and should be the target of future research.

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.

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.