Theta Asymmetry Research Articles

Brain electrical patterns associated with pleasure and emotion induced by tonal and atonal music.

Several studies in the last 40 years have used electroencephalography (EEG) to recognize patterns of brain electrical activity correlated with emotions evoked by various stimuli. For example, the frontal alpha and theta asymmetry models to distinguish musical emotions and musical pleasure, respectively. Since these studies have used mainly tonal music, in this study, we decided to incorporate both tonal (n = 8) and atonal (n = 8) musical stimuli to observe the subjective and electrophysiological responses associated with valence, arousal, pleasure, and familiarity, from 25 nonmusician Mexican adults (10 females, 15 males; M = 37.8 years old, SD = 15.1). Our results showed that atonal music was perceived as less familiar and pleasurable than tonal music, according to the average subjective ratings. Interestingly, greater right hemispheric activity (alpha suppression) was associated with atonal music listening. Additionally, there was an increase of theta power at the right frontal cortex (F4) correlated with a decrease of pleasure ratings, in line with the frontal theta asymmetry (FTA) model. Finally, according to the model of frontal alpha asymmetry (FAA) to distinguish musical emotions, activation (alpha suppression) of the left frontal cortex (F3) was correlated with greater valence and arousal-that is, joyful music. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Prefrontal, Frontal, and Temporal Theta EEG Asymmetries and Self-Reports of Emotional Regulation.

Previous studies have shown thatright-sided frontal alpha asymmetry (fAA) is an electroencephalography (EEG) marker for negatively valenced emotions and a marker for negative self-perceptions of a person's psychosocial interactions. Alpha activity is affected by the changes in visual stimulation associated with eye-opening and eye-closing; theta activity is not so affected. Therefore, this analysis investigates the relationship between an individual's theta asymmetry and self-perceptions of their psychosocial interactions. We used quantitative electroencephalographic (qEEG) data from eight right-handed male medical students aged between 19 and 38 years, recorded under eyes-open (EO) and eyes-closed (EC) conditions. Significant correlations were found between self-reported measures of psychosocial interactions via the Interactive Self-Report Inventory (ISI). The main finding was that greater left-sided frontal temporal asymmetry (fTA) under both EO and EC conditions was associated with lower "regulated" ISI scores and lower "dependent" ISI scores. Greater left-sided temporal theta asymmetry (tTA), under EC conditions, was associated with higher "anxious" ISI scores. Greater left-sided prefrontal theta symmetry (pfTA), under EO conditions, was associated with lower "relaxed" ISI scores. These findings suggest that theta asymmetries in the frontal, prefrontal, and temporal cortices may be indicative of negative emotional states. The results of this study underscore the potential of pfTA, fTA, and tTA to be used as biomarkers for cognitive-emotional balance. The implications for mental health interventions, particularly personalized therapeutic approaches, are significant.

Neurological Validation of ASD Diagnostic Criteria Using Frontal Alpha and Theta Asymmetry.

Background/Objectives: Diagnosis of Autism Spectrum Disorder (ASD) relies on the observation of difficulties in social communication and interaction, plus the presence of repetitive and restrictive behaviors. The identification of neurological correlates of these symptoms remains a high priority for clinical research, and has the potential to increase the validity of diagnosis of ASD as well as provide greater understanding of how the autistic brain functions. This study focused on two neurological phenomena that have been previously associated with psychiatric disorders (alpha- and theta-wave asymmetry across the frontal region of the brain), and tested for their association with the major diagnostic criteria for ASD. Methods: A total of 41 male autistic youth underwent assessment with the Autism Diagnostic Observation Schedule (ADOS-2) and 3 min of eyes-closed resting EEG to collect alpha- and theta-wave data from right and left frontal brain sites. Results: Different associations were found for theta versus alpha asymmetry and the ADOS-2 subscales, across different brain regions responsible for a varying range of cognitive functions. In general, theta asymmetry was associated with conversation with others, sharing of enjoyment, and making social overtures, whereas alpha asymmetry was linked with making eye contact, reporting events to others, and engaging in reciprocal social communication. Specific brain regions involved are identified, as well as implications for clinical practice. Conclusions: Specific autism symptoms may be associated with selected brain region activity, providing a neurological basis for diagnosis and treatment.

Frontal Theta Asymmetry may be a new target for reducing the severity of depression and improving cognitive function in depressed patients

BackgroundThe prevalence of depressive disorder is increasing due to a variety of factors, which brings a huge strain on individuals, families and society. This study aims to investigate whether there is Frontal Theta Asymmetry (FTA) in depressed patients, and whether FTAs are related to depression severity and cognitive function changes in depressed patients. MethodsParticipants who met the inclusion criteria were enrolled in this study. Socio-demographic data of each participant were recorded. Zung's self-rating Depression Scale was used to assess the depression status of participants. P300 was used to evaluate the cognitive function of participants. EEG data from participants were collected by the NeuroScan SynAmps RT EEG system. t-test, Wilcoxon rank-sum test and Chi-square test were used to detect the differences of different variables between the two groups. Multiple linear regression analysis and multiple logistic regression analysis were used to analyze relationships between FTAs in different regions and participants' depression status and cognitive function. ResultsA total of 66 depressed participants and 47 healthy control participants were included in this study. The theta spectral power of the left frontal lobe was slightly stronger than that of the right frontal lobe in the depression group, while the opposite was true in the healthy control group. The FTA in F3/F4 had certain effects on the emergence of depression in participants, the emergence of depression in participants and Changes in cognitive function. ConclusionsFTAs are helpful to assess the severity of depression and early identify cognitive impairment in patients with depression.

The Relationship Between Theta Power, Theta Asymmetry and the Effect of Escitalopram in the Treatment of Depression.

Only about one-third of depressed patients respond to initial antidepressant treatment. Therefore, it is crucial to find effective predictors of antidepressants. The purpose of our study was to learn the relationship between EEG theta power, theta asymmetry, and the efficacy of escitalopram. The study included 34 patients with depression. Before and after each patient's course of treatment, EEG data was gathered. Both the Hamilton Anxiety Scale (HAMA) and the 17-item Hamilton Depression Scale (HAMD-17) were evaluated simultaneously. The natural logarithm of right frontal theta power minus left frontal theta power was used to calculate inter-electrode theta asymmetry (AT). First, our study found no statistically significant difference between intra-electrode theta power and inter-electrode AT before and after treatment (P ≥ 0.05). When we later looked at the data regarding treatment effects, the findings revealed that patients (n = 9) who did not respond to treatment had lower baseline theta power at C4 [6.190 (2.000, 12.990) vs 15.800 (7.255, 22.330), z = -2.166, P = 0.030]. The two groups had no difference in other electrodes (P ≥ 0.05). The AT of C3/C4 in non-responders (n = 9) was lower [0.012 (0.795) vs 0.733 (0.539), t = -3.224, P = 0.005]. However, there was no difference in inter-electrode AT between the two groups in F3/F4 and F7/F8 (P ≥ 0.05). We finally show that the theta power at C4 was negatively correlated with HAMD scores before treatment (r = -0.346, P = 0.045). Our findings determined that increased theta power and positive asymmetry in the right frontal-central area correlate with favourable escitalopram treatment, providing a basis for finding predictive markers for antidepressants.

Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making

Exploring ones surroundings may yield unexpected rewards, but is associated with uncertainty and risk. Alternatively, exploitation of certain outcomes is related to low risk, yet potentially better outcomes remain unexamined. As such, risk-taking behavior depends on perceived uncertainty and a trade-off between exploration-exploitation. Previously, it has been suggested that risk-taking may relate to theta activity in the prefrontal cortex. Furthermore, previous studies hinted at a relationship between a right-hemispheric bias in frontal theta asymmetry and risky behavior. In the present double-blind sham-controlled within-subject study, we applied bifrontal transcranial alternating current stimulation (tACS) at the theta frequency (5 Hz) on eighteen healthy volunteers during a gambling task. Two tACS montages with either left-right or posterior-anterior current flow were employed at an intensity of 1 mA. Results showed that, compared to sham, theta tACS increased perceived uncertainty irrespective of current flow direction. Despite this observation, no direct effect of tACS on exploration behavior and general risk-taking was observed. Furthermore, frontal theta asymmetry was more right-hemispherically biased after posterior-anterior tACS, compared to sham. Finally, we used electric field simulation to identify which regions were targeted by the tACS montages as an overlap in regions may explain why the two montages resulted in comparable outcomes. Our findings provide a first step towards understanding the relationship between frontal theta oscillations and different features of risk-taking.

Driving-Induced Neurological Biomarkers in an Advanced Driver-Assistance System.

Physiological signals are immediate and sensitive to neurological changes resulting from the mental workload induced by various driving environments and are considered a quantifying tool for understanding the association between neurological outcomes and driving cognitive workloads. Neurological assessment, outside of a highly-equipped clinical setting, requires an ambulatory electroencephalography (EEG) headset. This study aimed to quantify neurological biomarkers during a resting state and two different scenarios of driving states in a virtual driving environment. We investigated the neurological responses of seventeen healthy male drivers. EEG data were measured in an initial resting state, city-roadways driving state, and expressway driving state using a portable EEG headset in a driving simulator. During the experiment, the participants drove while experiencing cognitive workloads due to various driving environments, such as road traffic conditions, lane changes of surrounding vehicles, the speed limit, etc. The power of the beta and gamma bands decreased, and the power of the delta waves, theta, and frontal theta asymmetry increased in the driving state relative to the resting state. Delta-alpha ratio (DAR) and delta-theta ratio (DTR) showed a strong correlation with a resting state, city-roadways driving state, and expressway driving state. Binary machine-learning (ML) classification models showed a near-perfect accuracy between the resting state and driving state. Moderate classification performances were observed between the resting state, city-roadways state, and expressway state in multi-class classification. An EEG-based neurological state prediction approach may be utilized in an advanced driver-assistance system (ADAS).

Resting-State Theta Oscillations and Reward Sensitivity in Risk Taking.

Females demonstrate greater risk aversion than males on a variety of tasks, but the underlying neurobiological basis is still unclear. We studied how theta (4–7 Hz) oscillations at rest related to three different measures of risk taking. Thirty-five participants (15 females) completed the Bomb Risk Elicitation Task (BRET), which allowed us to measure risk taking during an economic game. The Domain-Specific Risk-Taking Scale (DOSPERT) was used to measure self-assessed risk attitudes as well as reward and punishment sensitivities. In addition, the Barratt Impulsiveness Scale (BIS11) was included to quantify impulsiveness. To obtain measures of frontal theta asymmetry and frontal theta power, we used magnetoencephalography (MEG) acquired prior to task completion, while participants were at rest. Frontal theta asymmetry correlated with average risk taking during the game but only in the female sample. By contrast, frontal theta power correlated with risk taking as well as with measures of reward and punishment sensitivity in the joint sample. Importantly, we showed that reward sensitivity mediated a correlation between risk taking and the power of theta oscillations localized to the anterior cingulate cortex. In addition, we observed significant sex differences in source- and sensor-space theta power, risk taking during the game, and reward sensitivity. Our findings suggest that sensitivity to rewards, associated with resting-state theta oscillations in the anterior cingulate cortex, is a trait that potentially contributes to sex differences in risk taking.

Patterns of Intrahemispheric EEG Asymmetry in Insomnia Sufferers: An Exploratory Study.

Individuals with insomnia present unique patterns of electroencephalographic (EEG) asymmetry between homologous regions of each brain hemisphere, yet few studies have assessed asymmetry within the same hemisphere. Increase in intrahemispheric asymmetry during rapid eye movement (REM) sleep in good sleepers (GS) and disruption of REM sleep in insomnia sufferers (INS) both point out that this activity may be involved in the pathology of insomnia. The objective of the present exploratory study was to evaluate and quantify patterns of fronto-central, fronto-parietal, fronto-occipital, centro-parietal, centro-occipital and parieto-occipital intrahemispheric asymmetry in GS and INS, and to assess their association with sleep-wake misperception, daytime anxiety and depressive symptoms, as well as insomnia severity. This paper provides secondary analysis of standard EEG recorded in 43 INS and 19 GS for three nights in a sleep laboratory. Asymmetry measures were based on EEG power spectral analysis within 0.3–60 Hz computed between pairs of regions at frontal, central, parietal and occipital derivations. Repeated-measures ANOVAs were performed to assess group differences. Exploratory correlations were then performed on asymmetry and sleep-wake misperception, as well as self-reported daytime anxiety and depressive symptoms, and insomnia severity. INS presented increased delta and theta F3/P3 asymmetry during REM sleep compared with GS, positively associated with depressive and insomnia complaints. INS also exhibited decreased centro-occipital (C3/O1, C4/O2) and parieto-occipital (P3–O1, P4/O2) theta asymmetry during REM. These findings suggest that INS present specific patterns of intrahemispheric asymmetry, partially related to their clinical symptoms. Future studies may investigate the extent to which asymmetry is related to sleep-wake misperception or memory impairments.

Instantaneous amplitude and shape of postrhinal theta oscillations differentially encode running speed.

Hippocampal theta oscillations have a temporally asymmetric waveform shape, but it is not known if this theta asymmetry extends to all other cortical regions involved in spatial navigation and memory. Here, using both established and improved cycle-by-cycle analysis methods, we show that theta waveforms in the postrhinal cortex are also temporally asymmetric. On average, the falling phase of postrhinal theta cycles lasts longer than the subsequent rising phase. There are, however, rapid changes in both the instantaneous amplitude and instantaneous temporal asymmetry of postrhinal theta cycles. These rapid changes in amplitude and asymmetry are very poorly correlated, indicative of a mechanistic disconnect between these theta cycle features. We show that the instantaneous amplitude and asymmetry of postrhinal theta cycles differentially encode running speed. Although theta amplitude continues to increase at the fastest running speeds, temporal asymmetry of the theta waveform shape plateaus after medium speeds. Our results suggest that the amplitude and waveform shape of individual postrhinal theta cycles may be governed by partially independent mechanisms and emphasize the importance of employing a single cycle approach to understanding the genesis and behavioral correlates of cortical theta rhythms. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Classification of Depression Patients and Normal Subjects Based on Electroencephalogram (EEG) Signal Using Alpha Power and Theta Asymmetry.

Depression or Major Depressive Disorder (MDD) is a mental illness which negatively affects how a person thinks, acts or feels. MDD has become a major disease affecting millions of people presently. The diagnosis of depression is questionnaire based and is not based on any objective criteria. In this paper, feature extracted from EEG signal are used for the diagnosis of depression. Alpha, alpha1, alpha2, beta, delta and theta power and theta asymmetry was used as feature. Alpha1, alpha2 along with theta asymmetry was also used as a feature. Multi-Cluster Feature Selection (MCFS) was used for feature selection when feature combination was used. The classifiers used were Support Vector Machine (SVM), Logistic Regression (LR), Naïve-Bayesian (NB) and Decision Tree (DT). Alpha2 showed higher classification accuracy than alpha1 and alpha power in all applied classifier. From t-test it was found that there was a significant difference in the theta power of left and right hemisphere of normal subjects, but there was no significant difference in depression patients. Average theta asymmetry in normal subjects is higher than MDD patients but the difference in theta asymmetry in normal subjects and MDD patients is not significant. The combination of alpha2 and theta asymmetry showed the highest classification accuracy of 88.33% in SVM.

Frontal EEG Asymmetry and Middle Line Power Difference in Discrete Emotions.

A traditional model of emotion cannot explain the differences in brain activities between two discrete emotions that are similar in the valence-arousal coordinate space. The current study elicited two positive emotions (amusement and tenderness) and two negative emotions (anger and fear) that are similar in both valence and arousal dimensions to examine the differences in brain activities in these emotional states. Frontal electroencephalographic (EEG) asymmetry and midline power in three bands (theta, alpha and beta) were measured when participants watched affective film excerpts. Significant differences were detected between tenderness and amusement on FP1/FP2 theta asymmetry, F3/F4 theta and alpha asymmetry. Significant differences between anger and fear on FP1/FP2 theta asymmetry and F3/F4 alpha asymmetry were also observed. For midline power, midline theta power could distinguish two negative emotions, while midline alpha and beta power could effectively differentiate two positive emotions. Liking and dominance were also related to EEG features. Stepwise multiple linear regression results revealed that frontal alpha and theta asymmetry could predict the subjective feelings of two positive and two negative emotions in different patterns. The binary classification accuracy, which used EEG frontal asymmetry and midline power as features and support vector machine (SVM) as classifiers, was as high as 64.52% for tenderness and amusement and 78.79% for anger and fear. The classification accuracy was improved after adding these features to other features extracted across the scalp. These findings indicate that frontal EEG asymmetry and midline power might have the potential to recognize discrete emotions that are similar in the valence-arousal coordinate space.

Frontal Theta Asymmetry as a Biomarker of Depression

Electroencephalography (EEG) has been used extensively to study affective disorders. Quantitative spectral analysis of an EEG scan has been used to assess the biological basis of emotional disorders such as depression as well as to investigate biomarkers of affective disorders. Inter-hemispheric asymmetries in both baseline and stimulus-evoked frequencies (alpha, beta, theta, and delta) are potential biomarkers of depression. The role of frontal alpha asymmetry has been established, but other spectral frequencies such as frontal theta remain elusive. We compared the hemispheric differences in frontal theta power in depressed patients and controls before and during listening to music to study the correlation of frontal theta asymmetry with depression. To determine whether stimulus-evoked frontal theta asymmetry is a biomarker of depression, we compared 23 patients with mild depression (based on the Hamilton Depression Rating Scale) with 17 age- and sex-matched controls by conducting EEG at rest and after listening to Indian classical music. In controls without depression, the mean frontal theta power of the left hemisphere and frontal theta asymmetry increased significantly during music listening. In depressed patients, frontal theta asymmetry was reversed during music listening. Frontal theta asymmetry is a potential biomarker of depression.

Methods of Neuromarketing and Implication of the Frontal Theta Asymmetry induced due to musical stimulus as choice modeling

Neuromarketing is a discipline that uses the principles of neuroscience to study the market and consumer behavior to help companies improve the products and services they provide to their customers and help them beat their competitors. Even after a decade of research work and studies, neuromarketing is still in its infant stage. This paper explores various methods opted in neuromarketing and inferred the significant outcome of Frontal Theta Asymmetry during music listening to 41 subjects. Positive emotions (happy) increases theta power in the left the hemisphere, whereas negative emotions (sad) increases power in the right region. The formatted model of frontal theta asymmetry recommended for musical neuromarketing such advertising jingles; other film music launches other multimedia applications where the reduced electrode and computational complexity matter a lot In estimating the emotions evoked due to stimulus.

Abnormal Parietal Brain Function in ADHD: Replication and Extension of Previous EEG Beta Asymmetry Findings.

Background: Abundant work indicates ADHD abnormal posterior brain structure and function, including abnormal structural and functional asymmetries and reduced corpus callosum size. However, this literature has attracted considerably less research interest than fronto-striatal findings.Objective: To help address this imbalance, the current study replicates and extends our previous work showing abnormal parietal brain function in ADHD adults during the Conner’s Continuous Performance Test (CPT).Method: Our previous study found that ADHD adults had increased rightward EEG beta (16–21 Hz) asymmetry in inferior parietal brain regions during the CPT (p = 0.00001), and that this metric exhibited a lack of normal correlation (i.e., observed in controls) with beta asymmetry at temporal–parietal regions. We re-tested these effects in a new ADHD sample and with both new and old samples combined. We additionally examined: (a) EEG asymmetry in multiple frequency bands, (b) unilateral effects for all asymmetry findings, and (c) the association between EEG asymmetry and a battery of cognitive tests.Results: We replicated our original findings by demonstrating abnormal rightward inferior parietal beta asymmetry in adults with ADHD during the CPT, and again this metric exhibited abnormal reduced correlation to temporal–parietal beta asymmetry. Novel analyses also demonstrated a broader pattern of rightward beta and theta asymmetry across inferior, superior, and temporal–parietal brain regions, and showed that rightward parietal asymmetry in ADHD was atypically associated with multiple cognitive tests.Conclusion: Abnormal increased rightward parietal EEG beta asymmetry is an important feature of ADHD. We speculate that this phenotype may occur with any form of impaired capacity for top-down task-directed control over sensory encoding functions, and that it may reflect associated increase of attentional shifting and compensatory sustained/selective attention.

Frontal EEG/ERP correlates of attentional processes, cortisol and motivational states in adolescents from lower and higher socioeconomic status

Event-related potentials (ERPs) and other electroencephalographic (EEG) evidence show that frontal brain areas of higher and lower socioeconomic status (SES) children are recruited differently during selective attention tasks. We assessed whether multiple variables related to self-regulation (perceived mental effort) emotional states (e.g., anxiety, stress, etc.) and motivational states (e.g., boredom, engagement, etc.) may co-occur or interact with frontal attentional processing probed in two matched-samples of fourteen lower-SES and higher-SES adolescents. ERP and EEG activation were measured during a task probing selective attention to sequences of tones. Pre- and post-task salivary cortisol and self-reported emotional states were also measured. At similar behavioural performance level, the higher-SES group showed a greater ERP differentiation between attended (relevant) and unattended (irrelevant) tones than the lower-SES group. EEG power analysis revealed a cross-over interaction, specifically, lower-SES adolescents showed significantly higher theta power when ignoring rather than attending to tones, whereas, higher-SES adolescents showed the opposite pattern. Significant theta asymmetry differences were also found at midfrontal electrodes indicating left hypo-activity in lower-SES adolescents. The attended vs. unattended difference in right midfrontal theta increased with individual SES rank, and (independently from SES) with lower cortisol task reactivity and higher boredom. Results suggest lower-SES children used additional compensatory resources to monitor/control response inhibition to distracters, perceiving also more mental effort, as compared to higher-SES counterparts. Nevertheless, stress, boredom and other task-related perceived states were unrelated to SES. Ruling out presumed confounds, this study confirms the midfrontal mechanisms responsible for the SES effects on selective attention reported previously and here reflect genuine cognitive differences.

Cortical asymmetry: catching an object in free fall

The main goal of the present study was to analyze theta asymmetry through quantitative electroencephalography (qEEG) when individuals were exposed to a sequential motor task, i.e. catching a ball. The sample was composed of 23 healthy subjects, male and female, between 25 and 40 years of age. A two-way factor Anova was applied to compare pre and post moments related to the balls' drop and scalp regions (i.e., frontal and parieto-occipital cortices). The first analysis of the frontal region compared electrodes in the left, right and left/right hemispheres combined, with the frontal midline electrode (FZ) included in the analysis. The results showed moment and region main effects. The second analysis compared left versus right hemisphere without the FZ site. The findings demonstrated an interaction effect between moment and region. The first parieto-occipital analysis, comparing left, right and central regions, with PZ included in all regions, showed main effects of moment and region. The second analysis, comparing left, right (without Pz) and central regions strictly demonstrated a region main effect. Thus, we observed an asymmetric pattern in the frontal cortex (i.e., planning and response selection) when the subjects were waiting for the balls' drop. Moreover, the left hemisphere seems to engage differently from the other regions when the central nervous system needs to prepare for a motor action. On the other hand, the parieto-occipital cortex, which is related to attentive processes, demonstrated a more asymmetric activity towards the right region which implies a participation of this area in cognitive strategies in this particular task. Taken together, we concluded that the adopted experimental approach can be useful to explore several others directions combining sensorimotor integration tasks with different pathologies, such as depression, Alzheimer's and Parkinson's diseases.

Stable Asymmetric Interhemispheric Theta Power in Patients With Anorexia Nervosa During Haptic Perception Even After Weight Gain: A Longitudinal Study

The aim of this study was to investigate the interhemispheric brain electrical asymmetries during a resting period and during haptic tasks in theta frequency band (4–8 Hz) between healthy controls (N=10) and patients with anorexia nervosa (AN) (N=10). Additionally, AN patients were investigated twice in a longitudinal design (T0–T1) to analyze treatment effects. At rest, a theta asymmetry was observed in the AN group during an acute stage of starvation (T0) but not after weight gain (T1). Importantly, theta asymmetry over central regions (C3–C4) was observed in the AN group during the acute stage of starvation (T0) as well as after weight gain (T1) while performing haptic exploration tasks. In the control group, we found no significant theta asymmetry neither at rest nor during haptic explorations. Results are interpreted as an over-arousal of the right hemisphere in AN patients during complex multisensory integration processing which is possibly a result of general functional deficits of the right hemisphere.

Stable Asymmetric Interhemispheric Theta Power in Patients With Anorexia Nervosa During Haptic Perception Even After Weight Gain: A Longitudinal Study

The aim of this study was to investigate the interhemispheric brain electrical asymmetries during a resting period and during haptic tasks in theta frequency band (4–8 Hz) between healthy controls (N=10) and patients with anorexia nervosa (AN) (N=10). Additionally, AN patients were investigated twice in a longitudinal design (T0–T1) to analyze treatment effects. At rest, a theta asymmetry was observed in the AN group during an acute stage of starvation (T0) but not after weight gain (T1). Importantly, theta asymmetry over central regions (C3–C4) was observed in the AN group during the acute stage of starvation (T0) as well as after weight gain (T1) while performing haptic exploration tasks. In the control group, we found no significant theta asymmetry neither at rest nor during haptic explorations. Results are interpreted as an over-arousal of the right hemisphere in AN patients during complex multisensory integration processing which is possibly a result of general functional deficits of the right hemisphere.

Aging, Smoking and Hemispheric EEG Asymmetry

ABSTRACTAs previous research has shown central nicotinic receptors to (a) be asymmetrical, (b) decline with age, and (c) be more abundant in smokers, quantified EEG indices of hemispheric asymmetry were employed to assess whether smoker/non-smoker status affected the aging brain and whether the aging brain demonstrated an altered response to acute smoking/nicotine. Forty healthy volunteers participated, including 20 young (18–39 years) and 20 elderly (64–81 years) adults. Half of the subjects in each age category were lifelong non-smokers and half were cigarette smokers with average smoking histories of 9.3 and 52.0 years for young and elderly respectively. Inter-hemispheric theta and alpha asymmetry indices illustrated greater left hemisphere power (relative to right) in elderly adults, while the reverse trend was seen in young adults. Smokers and non-smokers both showed similar aging trends but differed with respect to their presence in frontal and posterior regions. Intra-hemispheric asymmetry indices, particularly with alpha activity, illustrated a reduced anterior-posterior gradient of power distribution in the elderly. Acute smoking increased slow (delta) and fast (beta) inter-hemispheric indices but only in elderly smokers. Smoking also altered the intra-hemispheric balance of slow wave activity in both age groups of smokers. The results are discussed in relation to normal and pathological aging.