'Pattern Formation and Dynamics in Nonequilibrium Systems'




 

  Click here for publications in 'Genetics and Neurophysiology of Alcohol Use Disorders'.

  Click here for publications in 'Environmental Radioactivity (Master thesis work)'.

 


"If all your papers are accepted, your career will blossom but you have to forget about the Nobel prize"


Alexei A. Abrikosov (Nobel Prize in Physics 2003) during his talk at the APS March Meeting 2004 - explaining the happy ending to the 50% rejection rate of his early paper submissions.


G. Bordyugov, N. Fischer, H. Engel, N. Manz, and O. Steinbock
"Anomalous dispersion in the Belousov–Zhabotinsky reaction: Experiments and modeling"
Physica D: Nonlinear Phenomena 239 (2010), 766-775.

Abstract:
We report results on dispersion relations and instabilities of traveling waves in excitable systems. Experiments employ solutions of the 1,4-cyclohexanedione Belousov–Zhabotinsky reaction confined to thin capillary tubes which create a pseudo-one-dimensional system. Theoretical analyses focus on a three-variable reaction-diffusion model that is known to reproduce qualitatively many of the experimentally observed dynamics. Using continuation methods, we show that the transition from normal, monotonic to anomalous, single-overshoot dispersion curves is due to an orbit flip bifurcation of the solitary pulse homoclinics. In the case of “wave stacking”, this anomaly induces attractive pulse interaction, slow solitary pulses, and faster wave trains. For “wave merging”, wave trains break up in the wake of the slow solitary pulse due to an instability of wave trains at small wavelength. A third case, “wave tracking” is characterized by the non-existence of solitary waves but existence of periodic wave trains. The corresponding dispersion curve is a closed curve covering a finite band of wavelengths.

PDF file of the publication on ResearchGate:

O. U. Kheowan, V. A. Davydov, N. Manz, and S. C. Müller
"Compensation of curvature effects by illumination"
Phys. Lett. A 367 (2007), 311-315.

Abstract:
Front deformation of initially planar excitation waves can be observed in nonplanar media or in spatially heterogeneously illuminated systems. The deformation of propagating reaction–diffusion waves in either of these systems has been investigated earlier separately. Here we present a combination of both heterogeneous systems, which can lead to a compensation of wave deformations. Our theoretical analysis of the evolution of propagating excitation waves, based on the framework of a kinematical theory, shows that the curvature effect can be compensated by illumination. Supporting experiments were performed with the light-sensitive Belousov–Zhabotinsky system.

PDF file of the publication on ResearchGate:

N. Manz and O. Steinbock
"Propagation failures, breathing pulses, and backfiring in an excitable reaction-diffusion system"
Chaos 16 (2006), 037112.

Abstract:
We report results from experiments with a pseudo-one-dimensional Belousov–Zhabotinsky reaction that employs 1,4-cyclohexanedione as its organic substrate. This excitable system shows traveling oxidation pulses and pulse trains that can undergo complex sequences of propagation failures. Moreover, we present examples for (i) breathing pulses that undergo periodic changes in speed and size and (ii) backfiring pulses that near their back repeatedly generate new pulses propagating in opposite direction.

PDF file of the publication on ResearchGate:

N. Manz, B. T. Ginn, and O. Steinbock
"Propagation Failure Dynamics of Wave Trains in Excitable Systems"
Phys. Rev. E 73 (2006), 066218.

Abstract:
We report experimental and numerical results on temporal patterns of propagation failures in reaction-diffusion systems. Experiments employ the 1,4-cyclohexanedione Belousov–Zhabotinsky reaction. The propagation failures occur in the frontier region of the wave train and can profoundly affect its expansion speed. The specific rhythms observed vary from simple periodic to highly complex and possibly chaotic sequences. All but the period-1 sequences are found in the transition region between “merging” and “tracking” dynamics, which correspond to wave behavior caused by two qualitatively different types of anomalous dispersion relations.

PDF file of the publication on ResearchGate:

N. Manz and O. Steinbock
"Dynamics of excitation pulses with attractive interaction: Kinematic analysis and chemical wave experiments"
Phys. Rev. E 70 (2004), 066213.

Abstract:
We present a theoretical analysis of stacking and destacking wave trains in excitable reaction-diffusion systems with anomalous velocity-wavelength dependence. For linearized dispersion relations, kinematic analysis yields an analytical function that rigorously describes front trajectories. The corresponding accelerations have exactly one extremum that slowly decays with increasing pulse number. For subsequent pulses these maxima occur with a lag time equal to the inverse slope of the linearized dispersion curve. These findings are reproduced in experiments with chemical waves in the 1,4-cyclohexanedione Belousov–Zhabotinsky reaction but should be also applicable to step bunching on crystal surfaces and certain traffic phenomena.

PDF file of the publication on ResearchGate:

N. Manz and O. Steinbock
"Tracking Waves and Spiral Drift in Reaction-Diffusion Systems with Finite Bandwidth Dispersion Relation"
J. Phys. Chem. A 108 (2004), 5295-5298.

Abstract:

We report experimental results on chemical waves in 1,4-cyclohexanedione Belousov–Zhabotinsky systems that obey finite bandwidth dispersion relations. Although solitary pulses and long-wavelength pulse trains are unstable, pacemakers can generate short-wavelength patterns in which fast waves periodically annihilate at the slowly expanding pattern boundary. Along these boundaries, one finds numerous traveling defects that can nucleate rotating spirals which drift outward with the island’s boundary. The drift follows logarithmic spirals and can induce spiral pair annihilation.

PDF file of the publication on ResearchGate:

Movie of a sprial drift in a 2D CHD-BZ system with tracking behavior.
Movie of a sprial drift and annihilation in a 2D CHD-BZ system with tracking behavior.

N. Manz, C. T. Hamik, and O. Steinbock
"Tracking Waves and Vortex Nucleation in Excitable Systems with Anomalous Dispersion"
Phys. Rev. Lett. 92 (2004), 248301.

Abstract:
We report experimental results obtained from a chemical reaction-diffusion system in which wave propagation is limited to a finite band of wavelengths and in which no solitary pulses exist. Wave patterns increase their size through repeated annihilation events of the frontier pulse that allow the succeeding pulses to advance farther. A related type of wave dynamics involves a stable but slow frontier pulse that annihilates subsequent waves in front-to-back collisions. These so-called merging dynamics give rise to an unexpected form of spiral wave nucleation. All of these phenomena are reproduced by a simple, three-species reaction-diffusion model that reveals the importance of the underlying anomalous dispersion relation.

PDF file of the publication on ResearchGate:

Movie of 1D CHD-BZ system with normal behavior.
Movie of 1D CHD-BZ system with stacking behavior.
Movie of 1D CHD-BZ system with merging behavior.
Movie of 1D CHD-BZ system with tracking behavior.

N. Manz, B. T Ginn, and O. Steinbock
"Meandering spiral waves in the 1,4-cyclohexanedione Belousov–Zhabotinsky system catalyzed by Fe[batho(SO3)2]34-/3-"
J. Phys. Chem. A 107 (2003), 11008-11012.

Abstract:
Meandering spiral waves are observed in the 1,4-cyclohexanedione Belousov–Zhabotinsky (CHD-BZ) reaction at very low concentrations (3-35 mM) of the organic substrate. The spiral tips describe hypocycle-like trajectories indicating the presence of two main rotation periods and radii. The ratio of these periods approaches 1 for decreasing concentrations of CHD. In this limit, we find Z-shaped trajectories with approximately two lobes. The use of Fe[batho(SO3)2]34-/3- as the BZ catalyst gives rise to extremely long rotation periods (1000-4000 s), and the tip trajectories span large areas of up to 40 mm2. As a result of the absence of gaseous products and the high absorption of the catalyst, this particular system is ideally suited for the investigation of spiral waves in closed, thin-layer systems, such as nonuniformly curved and micropatterned media.

PDF file of the publication on ResearchGate:

N. Manz and S. C. Müller
"Fabrication of quasi-two-dimensional, heterogeneously curved Belousov–Zhabotinsky systems"
Rev. Sci. Instrum. 74 (2003), 5161-5166.

Abstract:
For many years the Belousov–Zhabotinsky reaction has been used to explore the large variety of dynamical behavior of excitation waves. The understanding of chemical waves can be applied to other physical and biological systems. Most theoretical and experimental work has been done in planar media, whereas for nonplanar systems there exist many theoretical but only very few experimental studies. In this article we present a methodology to develop quasi-two-dimensional, nonhomogeneously curved reaction media. These systems can be used to perform experiments on chemical reaction-diffusion processes which occur, for instance, in the Belousov–Zhabotinsky reaction placed in nonplanar geometries.

PDF file of the publication on ResearchGate:

N. Manz, V. A. Davydov, S. C. Müller, and M. Bär
"Dependence of the spiral rotation frequency on the surface curvature of reaction-diffusion systems"
Phys. Lett. A 316 (2003), 311-316.

Abstract:
The dynamic behaviour of spiral waves rotating on surfaces of curved reaction–diffusion systems depends strongly on the curvature of the surface. It was shown in an earlier experiment that a spiral in a Belousov–Zhabotinsky system on a paraboloid drifts to the point of highest Gaussian curvature, as predicted numerically and analytically. Beyond this, theoretical work predicts an increase of the rotation frequency of spiral waves with an increase in the curvature of the system surface (e.g., spirals on different spherical surfaces with decreasing radii). This behaviour leads to an additional term in the function for the rotation frequency proportional to the Gaussian curvature of the system. In this Letter we combine both effects to determine the curvature dependence of the spiral rotation frequency in curved reaction–diffusion systems. On a non-homogeneously curved surface, the spiral tip (the inner end of a spiral) drifts through regions with increasing surface curvature. Measurements of the rotation frequency performed during this propagation verify the predicted effect. The experimental data are confirmed by analytical results in the framework of the kinematic theory.

PDF file of the publication on ResearchGate:

N. Manz, V. A. Davydov, V. S. Zykov, and S. C. Müller
"Excitation fronts in a spatially modulated light-sensitive Belousov–Zhabotinsky system"
Phys. Rev. E 66 (2002), 036207.

Abstract:
The evolution of excitation wave fronts in a spatially modulated light-sensitive Belousov–Zhabotinsky system is investigated experimentally and theoretically. The excitation wave propagates in a thin, quasi-twodimensional reaction layer, which is illuminated through a periodical gray level mask. The light-induceddifferences in excitability and velocity give rise to a temporal and spatial modulation of the initially flat fronts. The experimental front evolution is described in the framework of a kinematical theory as developed earlier for nonuniformly curved systems.

PDF file of the publication on ResearchGate:

V. A. Davydov, N. Manz, O. Steinbock, and S. C. Müller
"Critical properties of excitation waves on curved surfaces: Curvature-dependent loss of excitability"
Europhys. Lett. 59 (2002), 344-350.

Abstract:
In the literature, different properties of propagating excitation waves on curved surfaces are published. Theoretical papers predicted critical properties of waves on curved surfaces. If an excitation wave propagates in a non-planar system, its geodetic curvature causes a transition from excitable to non-excitable dynamics. In this paper we present first experimental results of the transition in a weakly excitable BZ system which are in good agreement with the theoretical predictions.

PDF file of the publication on ResearchGate:

C. T. Hamik, N. Manz, and O. Steinbock
"Anomalous Dispersion and Attractive Pulse Interaction in the 1,4-Cyclohexanedione Belousov–Zhabotinsky Reaction"
J. Phys. Chem. A 105 (2001), 6144-6153.

Abstract:
We report the formation of stable bound wave packets in a modified Belouso–Zhabotinsky reaction. These densely stacked structures arise from an attractive interaction between oxidation pulses that is not knownfrom the classical Belousov–Zhabotinsky system. The characteristic stacking period increases with the initial concentration of bromate but decreases with cyclohexanedione. Wave stacking can also induce cascades of bunching events in which internally dense but mutually well segregated wave clusters are formed. For different initial concentrations, we observed the apparent merging of waves in front-to-back collisions. All three modes of wave dynamics are analyzed in terms of their dispersion behavior. The dispersion relations proved to be anomalous in each case and revealed the existence of an attractor which induces the formation of stable wave packets. The underlying mechanism has a pure reaction-diffusion character since wave propagation is not affected by fluid convection. At high initial concentrations of ferroin, we detected complex relaxation kinetics which indicate the presence of at least two independent species that control the recovery and hence the dispersion behavior of the medium.

PDF file of the publication on ResearchGate:

V. A. Davydov, N. Manz, O. Steinbock, V. S. Zykov, and S. C. Müller
"Excitation Fronts on a Periodically Modulated Curved Surface"
Phys. Rev. Lett. 85 (2000), 868-871.

Abstract:
The evolution of an excitation front propagating on a nonuniformly curved surface is considered within the framework of a kinematical model of its motion. For the case of a surface with a periodically modulated curvature an exact solution of the front shape is obtained under the assumption of sufficiently small surface deformation. The results of the theoretical consideration are compared with the experimental data obtained with a modified Belousov–Zhabotinsky reaction in a thin nonuniformly curved layer.

PDF file of the publication on ResearchGate:

N. Manz, S. C. Müller, and O. Steinbock
"Anomalous dispersion of chemical waves in a homogeneously catalyzed reaction system"
J. Phys. Chem. A 104 (2000), 5895-5896.

Abstract:
We present experimental results that demonstrate anomalous dispersion in a Belousov–Zhabotinsky system. The reaction is carried out at high concentrations of sulfuric acid and involves 1,4-cyclohexanedione as its organic substrate. The unusual dispersion behavior of this excitable medium induces an attractive interaction between pulses that results in fusion or closed stacking of waves. Experimental results from quasi-onedimensional as well as two-dimensional media are presented. In two-dimensional reaction systems, a complex dependence of the propagation velocity on the relative direction between fronts is found and the formation of spiral defects is observed.

PDF file of the publication on ResearchGate:


Non peer-reviewed publications

N. Manz
"Untersuchung der Dynamik chemischer Erregungswellen in Belousov–Zhabotinsky-Systemen mit anomaler Dispersion" ("Investigation of the dynamic of chemical excitation waves in Belousov-Zhabotinsky systems with anomalous dispersion")
Nova Acta Leopoldina, Neue Folge Suppl. 20 (2006), 103-104.

PDF file of the publication on ResearchGate:

N. Manz
"Untersuchung der Dynamik chemischer Erregungswellen in Belousov–Zhabotinsky-Systemen mit anomaler Dispersion" ("Investigation of the dynamic of chemical excitation waves in Belousov-Zhabotinsky systems with anomalous dispersion")
Nova Acta Leopoldina, Neue Folge Suppl. 19 (2004), 135-137.

PDF file of the publication on ResearchGate:

N. Manz
"Untersuchung chemischer Wellen in der Belousov–Zhabotinsky-Reaktion: räumliche modulierte Systeme und anomale Dispersion" ("Investigation of chemical waves in the Belousov–Zhabotinsky reaction: spatially modulated systems and anomalous dispersion")
Cuvillier Verlag, Göttingen, Germany, pp 210. (ISBN-10: 3898735273) (2002)

PDF file of the publication on ResearchGate:




Publications in 'Genetics and Neurophysiology of Alcohol Use Disorders':

 


J. L. Meyers, J. Zhang, J.-C. Wang, J. Su, S. I.-C. Kuo, M. Kapoor, L. Wetherill, S. Bertelsen, D. Lai, J.E. Salvatore, C. Kamarajan, D. B. Chorlian, A. Agrawal, L. Almasy, L. Bauer, G. Chan, V. Hesselbrock, L. Koganti, J. Kramer, S. Kuperman, N. Manz, A. Pandey, M. Seay, D. Scott, R. E. Taylor, K.K. Buchholz, D. M. Dick, H. J. Edenberg, A. Goate, T. Foroud, and B. Porjesz
"An Endo-phenotype Approach to the Genetics of Alcohol Dependence: A Genome Wide Association Study of Fast Beta EEG in Families of African Ancestry"
Molecular Psychiatry xx (2017), in press.

Abstract:
Fast beta (20–28 Hz) electroencephalogram (EEG) oscillatory activity may be a useful endophenotype for studying the genetics of disorders characterized by neural hyperexcitability, including substance use disorders (SUDs). However, the genetic underpinnings of fast beta EEG have not previously been studied in a population of African-American ancestry (AA). In a sample of 2382 AA individuals from 482 families drawn from the Collaborative Study on the Genetics of Alcoholism (COGA), we performed a genome-wide association study (GWAS) on resting-state fast beta EEG power. To further characterize our genetic findings, we examined the functional and clinical/behavioral significance of GWAS variants. Ten correlated single-nucleotide polymorphisms (SNPs) (r2 < 0.9) located in an intergenic region on chromosome 3q26 were associated with fast beta EEG power at P < 5 × 10−8. The most significantly associated SNP, rs11720469 (β: −0.124; P < 4.5 × 10−9), is also an expression quantitative trait locus for BCHE (butyrylcholinesterase), expressed in thalamus tissue. Four of the genome-wide SNPs were also associated with Diagnostic and Statistical Manual of Mental Disorders Alcohol Dependence in COGA AA families, and two (rs13093097, rs7428372) were replicated in an independent AA sample (Gelernter et al.). Analyses in the AA adolescent/young adult (offspring from COGA families) subsample indicated association of rs11720469 with heavy episodic drinking (frequency of consuming 5+ drinks within 24 h). Converging findings presented in this study provide support for the role of genetic variants within 3q26 in neural and behavioral disinhibition. These novel genetic findings highlight the importance of including AA populations in genetics research on SUDs and the utility of the endophenotype approach in enhancing our understanding of mechanisms underlying addiction susceptibility.

PDF file of the publication on ResearchGate:

D. B. Chorlian, M. Rangaswamy, N. Manz, J. L. Meyers, S. J. Kang, C. Kamarajan, A. K. Pandey, J.-C. Wang, L. Wetherill, H. J. Edenberg, and B. Porjesz
"Genetic correlates of the development of theta event related oscillations in adolescents and young adults"
International Journal of Psychophysiology 115 (2017), 24-39.

Abstract:
The developmental trajectories of theta band (4–7 Hz) event-related oscillations (EROs), a key neurophysiological constituent of the P3 response, were assessed in 2170 adolescents and young adults ages 12 to 25. The theta EROs occurring in the P3 response, important indicators of neurocognitive function, were elicited during the evaluation of task-relevant target stimuli in visual and auditory oddball tasks. Associations between the theta EROs and genotypic variants of 4 KCNJ6 single nucleotide polymorphisms (SNPs) were found to vary with age, sex, scalp location, and task modality. Three of the four KCNJ6 SNPs studied here were found to be significantly associated with the same theta EROs in adults in a previous family genome wide association study. Since measures of the P3 response have been found to be a useful endophenotypes for the study of a number of clinical and behavioral disorders, studies of genetic effects on its development in adolescents and young adults may illuminate neurophysiological factors contributing to the onset of these conditions.

PDF file of the publication on ResearchGate:

C. Kamarajan, A. K. Pandey, D. B. Chorlian, N. Manz, A. T. Stimus, H. J. Edenberg, L. Wetherill, M. Schuckit, J.-C. Wang, S. Kuperman, J. Kramer, J. A. Tischfield, and B. Porjesz
"A KCNJ6 gene polymorphism modulates theta oscillations during reward processing"
International Journal of Psychophysiology 115 (2017), 13-23.

Abstract:
Event related oscillations (EROs) are heritable measures of neurocognitive function that have served as useful phenotype in genetic research. A recent family genome-wide association study (GWAS) by the Collaborative Study on the Genetics of Alcoholism (COGA) found that theta EROs during visual target detection were associated at genome-wide levels with several single nucleotide polymorphisms (SNPs), including a synonymous SNP, rs702859, in the KCNJ6 gene that encodes GIRK2, a G-protein inward rectifying potassium channel that regulates excitability of neuronal networks. The present study examined the effect of the KCNJ6 SNP (rs702859), previously associated with theta ERO to targets in a visual oddball task, on theta EROs during reward processing in a monetary gambling task. The participants were 1601 adolescent and young adult offspring within the age-range of 17–25 years (800 males and 801 females) from high-dense alcoholism families as well as control families of the COGA prospective study. Theta ERO power (3.5–7.5 Hz, 200–500 ms post-stimulus) was compared across genotype groups. ERO theta power at central and parietal regions increased as a function of the minor allele (A) dose in the genotype (AA > AG > GG) in both loss and gain conditions. These findings indicate that variations in the KCNJ6 SNP influence magnitude of theta oscillations at posterior loci during the evaluation of loss and gain, reflecting a genetic influence on neuronal circuits involved in reward-processing. Increased theta power as a function of minor allele dose suggests more efficient cognitive processing in those carrying the minor allele of the KCNJ6 SNPs. Future studies are needed to determine the implications of these genetic effects on posterior theta EROs as possible “protective” factors, or as indices of delays in brain maturation (i.e., lack of frontalization).

PDF file of the publication on ResearchGate:

J. L Meyers, J. Zhang, N. Manz, M. Rangaswamy, C. Kamarajan, L. Wetherill, D. B. Chorlian, S. J. Kang, L Bauer, H. J. Edenberg, A. Goate, V. Hesselbrock, J. Kramer, S. Kuperman, J. I. Nurnberger Jr, J. Tischfield, J.-C. Wang, T. Foroud, and B. Porjesz
"A Genome Wide Association Study of Fast Beta EEG in Families of European Ancestry"
International Journal of Psychophysiology 115 (2017), 74-85.

Abstract:
Background: Variation in fast beta (20-28 Hz) electroencephalogram (EEG) oscillatory activity has been observed among some individuals with psychiatric and substance use disorders, suggesting that it may be a useful endophenotype for studying the genetics of disorders characterized by neural hyper-excitability. Despite the high heritability estimates provided by twin and family studies, there have been relatively few genetic studies of beta EEG, and to date only one genetic association finding has replicated (i.e., GABRA2). Method: In a sample of 1,564 individuals from 117 families of European Ancestry (EA) drawn from the Collaborative Study on the Genetics of Alcoholism (COGA), we performed a Genome-Wide Association Study (GWAS) on resting-state fronto-central fast beta EEG power, adjusting regression models for family relatedness, age, sex, and ancestry. To further characterize genetic findings, we examined the functional and behavioral significance of GWAS findings. Results: Three intronic variants located within DSE (dermatan sulfate epimerase) on 6q22 were associated with fast beta EEG at a genome wide significant level (p<5×10-8). The most significant SNP was rs2252790 (p<2.6×10-8; MAF: 0.36; β: 0.135). rs2252790 is an eQTL for ROS1 expressed most robustly in the temporal cortex (p:1.2×10-6) and for DSE/TSPYL4 expressed most robustly in the hippocampus (p:7.3×10-4; β: 0.29). Previous studies have indicated that DSE is involved in a network of genes integral to membrane organization; gene-based tests indicated that several variants within this network (i.e., DSE, ZEB2, RND3, MCTP1, and CTBP2) were also associated with beta EEG (empirical p<0.05), and of these genes, ZEB2 and CTBP2 were associated with DSM-V Alcohol Use Disorder (AUD; empirical p<0.05). Discussion: In this sample of EA families enriched for AUDs, fast beta EEG is associated with variants within DSE on 6q22; the most significant SNP influences the mRNA expression of DSE and ROS1 in hippocampus and temporal cortex, brain regions important for beta EEG activity. Gene-based tests suggest evidence of association with related genes, ZEB2, RND3, MCTP1, CTBP2, and beta EEG. Converging data from GWAS, gene expression, and gene-networks presented in this study provide support for the role of genetic variants within DSE and related genes in neural hyperexcitability, and has highlighted two potential candidate genes for AUD and/or related neurological conditions: ZEB2 and CTBP2. However, results must be replicated in large, independent samples. PDF file of the publication on ResearchGate:

A. K. Pandey, C. Kamarajan, N. Manz, D. B. Chorlian, A. T. Stimus, and B. Porjesz
"Delta, theta, and alpha event-related oscillations in alcoholics during Go/NoGo task: neurocognitive deficits in execution, inhibition, and attention processing"
Progress in Neuro-Psychopharmacology & Biological Psychiatry 65 (2016), 158-171.

Abstract:
Higher impulsivity observed in alcoholics is thought to be due to neurocognitive functional deficits involving impaired inhibition in several brain regions and/or neuronal circuits. Event-related Oscillations (EROs) offer time-frequency measure of brain rhythms during perceptual and cognitive processing, which provide a detailed view of neuroelectric oscillatory responses to external/internal events. The present study examines evoked power (temporally locked to events) of oscillatory brain signals in alcoholics during an equal probability Go/NoGo task, assessing their functional relevance in execution and inhibition of a motor response. The current study hypothesized that increases in the power of slow frequency bands and their topographical distribution is associated with tasks that have increased cognitive demands, such as the execution and inhibition of a motor response. Therefore, it is hypothesized that alcoholics would show lower spectral power in their topographical densities compared to controls. The sample consisted of 20 right-handed abstinent alcoholic males and 20 age and gender-matched healthy controls. Evoked delta (1.0-3.5 Hz; 200-600 ms), theta (4.0-7.5 Hz; 200-400 ms), slow alpha (8.0-9.5 Hz; 200-300 ms), and fast alpha (10.0-12.5 Hz; 100-200 ms) ERO power were compared across group and task conditions. Compared to controls, alcoholics had higher impulsiveness scores on the Barrett Impulsiveness Scale (BIS-11) and made more errors on Go trials. Alcoholics showed significantly lower evoked delta, theta, and slow alpha power compared to controls for both Go and NoGo task conditions, and lower evoked fast alpha power compared to controls for only the NoGo condition. The results confirm previous findings and are suggestive of neurocognitive deficits while executing and suppressing a motor response. Based on findings in the alpha frequency ranges, it is further suggested that the inhibitory processing impairments in alcoholics may arise from inadequate early attentional processing with respect to the stimulus related aspects/semantic memory processes, which may be reflected in lower posterio-temporal evoked fast alpha power. It can thus be concluded that alcoholics show neurocognitive deficits in both execution and suppression of a motor response and inadequate early attentional processing with respect to the semantic memory/stimulus related aspects while suppressing a motor response

PDF file of the publication on ResearchGate:

C. Kamarajan, A. K. Pandey, D. B. Chorlian, N. Manz, A. T. Stimus, L. O. Bauer , V. M. Hesselbrock, M. A. Schuckit , S, Kuperman , J. Kramer, and B. Porjesz
"Reward processing deficits and impulsivity in high-risk offspring of alcoholics: A study of event-related potentials during a monetary gambling task"
International Journal of Psychophysiology 98 (2015), 182-200.

Abstract:
Background: Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. The goal of the present study is to elucidate reward processing deficits, externalizing disorders, and impulsivity as elicited by electrophysiological, clinical and behavioral measures in subjects at high risk for alcoholism from families densely affected by alcoholism in the context of brain maturation across age groups and gender.
Methods: Event-related potentials (ERPs) and current source density (CSD) during a monetary gambling task (MGT) were measured in 12-25 year old offspring (N = 1864) of families in the Collaborative Study on the Genetics of Alcoholism (COGA) Prospective study; the high risk (HR, N = 1569) subjects were from families densely affected with alcoholism and the low risk (LR, N = 295) subjects were from community families. Externalizing disorders and impulsivity scores were also compared between LR and HR groups.
Results: HR offspring from older (16-25 years) male and younger (12-15 years) female subgroups showed lower P3 amplitude than LR subjects. The amplitude decrement was most prominent in HR males during the loss condition. Overall, P3 amplitude increase at anterior sites and decrease at posterior areas were seen in older compared to younger subjects, suggesting frontalization during brain maturation. The HR subgroups also exhibited hypofrontality manifested as weaker CSD activity during both loss and gain conditions at frontal regions. Further, the HR subjects had higher impulsivity scores and increased prevalence of externalizing disorders. P3 amplitudes during the gain condition were negatively correlated with impulsivity scores.
Conclusions: Older male and younger female HR offspring, compared to their LR counterparts, manifested reward processing deficits as indexed by lower P3 amplitude and weaker CSD activity, along with higher prevalence of externalizing disorders and higher impulsivity scores.
Significance: Reward related P3 is a valuable measure reflecting neurocognitive dysfunction in subjects at risk for alcoholism, as well as to characterize reward processing and brain maturation across gender and age group.

PDF file of the publication on ResearchGate:

C. Kamarajan, A. K. Pandey, D. B. Chorlian, N. Manz, A. T. Stimus, A. P. Anokhin, L. O. Bauer, S. Kuperman, J. Kramer, K. K. Bucholz, M. A. Schuckit, V. M. Hesselbrock, and B. Porjesz
"Deficient event-related theta oscillations in individuals at risk for alcoholism: A study of reward processing and impulsivity features"
PlosONE 10 (2015), e0142659.

Abstract:
Background: Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. Event-related oscillations (EROs) have been used to effectively measure brain (dys)function during cognitive tasks in individuals with alcoholism and related disorders and in those at risk to develop these disorders. The current study examines ERO theta power during reward processing as well as impulsivity in adolescent and young adult subjects at high risk for alcoholism.
Methods: EROs were recorded during a monetary gambling task (MGT) in 12–25 years old participants (N = 1821; males = 48%) from high risk alcoholic families (HR, N = 1534) and comparison low risk community families (LR, N = 287) from the Collaborative Study on the Genetics of Alcoholism (COGA). Impulsivity scores and prevalence of externalizing diagnoses were also compared between LR and HR groups.
Results: HR offspring showed lower theta power and decreased current source density (CSD) activity than LR offspring during loss and gain conditions. Younger males had higher theta power than younger females in both groups, while the older HR females showed more theta power than older HR males. Younger subjects showed higher theta power than older subjects in each comparison. Differences in topography (i.e., frontalization) between groups were also observed. Further, HR subjects across gender had higher impulsivity scores and increased prevalence of externalizing disorders compared to LR subjects.
Conclusions: As theta power during reward processing is found to be lower not only in alcoholics, but also in HR subjects, it is proposed that reduced reward-related theta power, in addition to impulsivity and externalizing features, may be related in a predisposition to develop alcoholism and related disorders.

PDF file of the publication on ResearchGate:

D.B. Chorlian, M. Rangaswamy, N. Manz, C. Kamarajan, A.K. Pandey, H. Edenberg, S. Kuperman, and B. Porjesz:
"Gender modulates the development of Theta Event Related Oscillations in Adolescents and Young Adults" Behavioural Brain Research 292 (2015), 342-352.

Abstract:
The developmental trajectories of theta band (4-7 Hz) event-related oscillations (EROs), a key neurophysiological constituent of the P3 response, were assessed in 2170 adolescents and young adults ages 12 to 25. The theta EROs occurring in the P3 response, important indicators of neurocognitive function, were elicited during the evaluation of task-relevant target stimuli in visual and auditory oddball tasks. These tasks call upon attentional and working memory resources. Large differences in developmental rates between males and females were found; scalp location and task modality (visual or auditory) differences within males and females were small compared to gender differences. Trajectories of interregional and intermodal correlations between ERO power values exhibited increases with age in both genders, but showed a divergence in development between auditory and visual systems during ages 16 to 21. These results are consistent with previous electrophysiological and imaging studies and provide additional temporal detail about the development of neurophysiological indices of cognitive activity. Since measures of the P3 response has been found to be a useful endophenotypes for the study of a number of clinical and behavioral disorders, studies of its development in adolescents and young adults may illuminate neurophysiological factors contributing to the onset of these conditions.

PDF file of the publication on ResearchGate:

J.-C. Wang, T. Foroud, A. L. Hinrichs, N. X. H. Le, S. Bertelsen, J. P. Budde, O. Harari, D. L. Koller, L. Wetherill, A. Agrawal, L. Almasy, A. I. Brooks, K. Bucholz, D. Dick, V. Hesselbrock, E. O. Johnson, S. Kang, M. Kapoor, J. Kramer, S. Kuperman, P. A. F. Madden, N. Manz, N. G. Martin, J. N. McClintick, G. W. Montgomery, J. I. Nurnberger Jr, M. Rangaswamy, J. Rice, M. Schuckit, J. A. Tischfield, J. B. Whitfield, X. Xuei, B. Porjesz, A. C. Heath, H. J. Edenberg, L. J. Bierut, and A. M. Goate:
"A genome wide association study of alcohol dependence symptom counts in extended pedigrees identifies C15orf53" Molecular Psychiatry 18 (2013), 1218-1224.

Abstract:
Several studies have identified genes associated with alcohol-use disorders (AUDs), but the variation in each of these genes explains only a small portion of the genetic vulnerability. The goal of the present study was to perform a genome-wide association study (GWAS) in extended families from the Collaborative Study on the Genetics of Alcoholism to identify novel genes affecting risk for alcohol dependence (AD). To maximize the power of the extended family design, we used a quantitative endophenotype, measured in all individuals: number of alcohol-dependence symptoms endorsed (symptom count (SC)). Secondary analyses were performed to determine if the single nucleotide polymorphisms (SNPs) associated with SC were also associated with the dichotomous phenotype, DSM-IV AD. This family-based GWAS identified SNPs in C15orf53 that are strongly associated with DSM-IV alcohol-dependence symptom counts (P=4.5×10-8, inflation-corrected P=9.4×10-7). Results with DSM-IV AD in the regions of interest support our findings with SC, although the associations were less significant. Attempted replications of the most promising association results were conducted in two independent samples: nonoverlapping subjects from the Study of Addiction: Genes and Environment (SAGE) and the Australian Twin Family Study of AUDs (OZALC). Nominal association of C15orf53 with SC was observed in SAGE. The variant that showed strongest association with SC, rs12912251 and its highly correlated variants (D'=1, r2>=0.95), have previously been associated with risk for bipolar disorder.

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D. B. Chorlian, M. Rangaswamy, N. Manz, J.-C. Wang, D. Dick, L. Almasy, L. Bauer, K. Bucholz, T. Foroud, V. Hesselbrock, S. Kang, J. Kramer, S. Kuperman, J. Nurnberger Jr., J. Rice, M. Schuckit, J. Tischfield, H.J. Edenberg, A. Goate, L. Bierut, and B. Porjesz:
"Genetic and neurophysiological correlates of the age of onset of alcohol use disorders in adolescents and young adults" Behavior Genetics 43 (2013), 386-401.

Abstract:
Discrete time survival analysis was used to assess the age-specific association of event-related oscillations (EROs) and CHRM2 gene variants on the onset of regular alcohol use and alcohol dependence. The subjects were 2,938 adolescents and young adults ages 12–25. Results showed that the CHRM2 gene variants and ERO risk factors had hazards which varied considerably with age. The bulk of the significant age-specific associations occurred in those whose age of onset was under 16. These associations were concentrated in those subjects who at some time took an illicit drug. These results are consistent with studies which associate greater rates of alcohol dependence among those who begin drinking at an early age. The age specificity of the genetic and neurophysiological factors is consistent with recent studies of adolescent brain development, which locate an interval of heightened vulnerability to substance use disorders in the early to mid teens.

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S. J. Kang, M. Rangaswamy, N. Manz, J.-C. Wang, L. Wetherill, T. Hinrichs, L. Almasy, A. Brooks, D. B. Chorlian, D. Dick, V. Hesselbrock, J. Kramer, S. Kuperman, J. Nurnberger Jr, J. Rice, M. Schuckit, J. Tischfield, L.J. Bierut, H. J. Edenberg, A. Goate, T. Foroud, and B. Porjesz:
"Family-based Genome-wide Association Study of Frontal Theta Oscillations Identifies Potassium Channel Gene KCNJ6" Genes, Brain and Behavior 11 (2012), 712-719.

Abstract:
Event-related oscillations (EROs) represent highly heritable neuroelectric correlates of cognitive processes that manifest deficits in alcoholics and in offspring at high risk to develop alcoholism. Theta ERO to targets in the visual oddball task has been shown to be an endophenotype for alcoholism. A family-based genomewide association study was performed for the frontal theta ERO phenotype using 634 583 autosomal single nucleotide polymorphisms (SNPs) genotyped in 1560 family members from 117 families densely affected by alcohol use disorders, recruited in the Collaborative Study on the Genetics of Alcoholism. Genome-wide significant association was found with several SNPs on chromosome 21 in KCNJ6 (a potassium inward rectifier channel; KIR3.2/GIRK2), with the most significant SNP at p = 4.7 ×10-10). The same SNPs were also associated with EROs from central and parietal electrodes, but with less significance, suggesting that the association is frontally focused. One imputed synonymous SNP in exon four, highly correlated with our top three SNPs, was significantly associated with the frontal theta ERO phenotype. These results suggest KCNJ6 or its product GIRK2 account for some of the variations in frontal theta band oscillations. GIRK2 receptor activation contributes to slow inhibitory postsynaptic potentials that modulate neuronal excitability, and therefore influence neuronal networks.

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C. Kamarajan, M. Rangaswamy, N. Manz, D. B. Chorlian, A. K. Pandey, B. N. Roopesh, and B. Porjesz
"Topography, Power and Current Source Density of Theta Oscillations during Reward Processing as Markers for Alcohol Dependence"
Human Brain Mapping 33 (2012), 1019-1039.

Abstract:
Recent studies have linked alcoholism with a dysfunctional neural reward system. Although several electrophysiological studies have explored reward processing in healthy individuals, such studies in alcohol dependent individuals are quite rare. The present study examines theta oscillations during reward processing in abstinent alcoholics. The electroencephalogram (EEG) was recorded in 38 abstinent alcoholics and 38 healthy controls as they performed a single outcome gambling task which involved outcomes of either loss or gain of an amount (10¢ or 50¢) that was bet. Event-related theta band (3.0–7.0 Hz) power following each outcome stimulus was computed using the S-transform method. Theta power at the time window of the outcome-related negativity (ORN) and positivity (ORP) (200–500 ms) was compared across groups and outcome conditions. Additionally, behavioral data of impulsivity and task performance were analyzed. The alcoholic group showed significantly decreased theta power during reward processing compared to
controls. Current Source Density (CSD) maps of alcoholics revealed weaker and diffuse source activity for all conditions and weaker bilateral prefrontal sources during the Loss 50 condition as compared to controls who manifested stronger and focused midline sources. Further, alcoholics
exhibited increased impulsivity and risk-taking on the behavioral measures. A strong association between reduced anterior theta power and impulsive task-performance was observed. It is suggested that decreased power and weaker and diffuse CSD in alcoholics may be due to dysfunctional neural reward circuitry. The relationship among alcoholism, theta oscillations, reward processing and impulsivity could offer clues to understand brain circuitries that mediate reward processing and inhibitory control.

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M. Kapoor, J. C Wang, S. Bertelsen, K. Bucholz, J. P Budde, A. Hinrichs, A. Agrawal, A. Brooks, D. B Chorlian, D. Dick, V. Hesselbrock, T. Foroud, J. Kramer, S. Kuperman, N. Manz, J. Nurnberger Jr, B. Porjesz, J. P Rice, J. Tischfield, X. Xuei, M. Schuckit, H. J Edenberg, L. J Bierut, and A. Goate
"Variants located upstream of CHRNB4 on chromosome 15q25.1 are associated with age at onset of daily smoking and habitual smoking"
PLoS ONE 7 (2012), e33513.

Abstract:
Several genome-wide association and candidate gene studies have linked chromosome 15q24–q25.1 (a region including the CHRNA5-CHRNA3-CHRNB4 gene cluster) with alcohol dependence, nicotine dependence and smoking-related illnesses such as lung cancer and chronic obstructive pulmonary disease. To further examine the impact of these genes on the development of substance use disorders, we tested whether variants within and flanking the CHRNA5-CHRNA3-CHRNB4 gene cluster affect the transition to daily smoking (individuals who smoked cigarettes 4 or more days per week) in a cross sectional sample of adolescents and young adults from the COGA (Collaborative Study of the Genetics of Alcoholism) families. Subjects were recruited from families affected with alcoholism (either as a first or second degree relative) and the comparison families. Participants completed the SSAGA interview, a comprehensive assessment of alcohol and other substance use and related behaviors. Using the Quantitative trait disequilibrium test (QTDT) significant association was detected between age at onset of daily smoking and variants located upstream of CHRNB4. Multivariate analysis using a Cox proportional hazards model further revealed that these variants significantly predict the age at onset of habitual smoking among daily smokers. These variants were not in high linkage disequilibrium (0.28<r^2<0.56) with variants that have previously been reported to affect risk for nicotine dependence and smoking related diseases in adults. The data suggests that an age-associated relationship underlies the association of SNPs in CHRNB4 with onset of chronic smoking behaviors in adolescents and young adults and may improve genetic information that will lead to better prevention and intervention for
substance use disorders among adolescents and young adults.

PDF file of the publication on ResearchGate:

A. K. Pandey, C. Kamarajan, Y. Tang, D. B. Chorlian, B. N. Roopesh, N. Manz, A. Stimus, M. Rangaswamy, and B. Porjesz
"Neurocognitive Deficits in Male Alcoholics: An ERP/sLORETA Analysis of the N2 Component in an Equal Probability Go/NoGo Task"
Biological Psychiatry 89 (2012), 170-182.

Abstract:
In alcoholism research, studies concerning time-locked electrophysiological aspects of response inhibition have concentrated mainly on the P3 component of the event-related potential (ERP). The objective of the present study was to investigate the N2 component of the ERP to elucidate possible brain dysfunction related to the motor response and its inhibition using a Go/NoGo task in alcoholics. The sample consisted of 78 abstinent alcoholic males and 58 healthy male controls. The N2 peak was compared across group and task conditions. Alcoholics showed significantly reduced N2 peak amplitudes compared to normal controls for Go as well as NoGo task conditions. Control subjects showed significantly larger NoGo than Go N2 amplitudes at frontal regions, whereas alcoholics did not show any differences between task conditions at frontal regions. Standardized low resolution electromagnetic tomography analysis (sLORETA) indicated that alcoholics had significantly lower current density at the source than control subjects for the NoGo condition at bilateral anterior prefrontal regions, whereas the differences between groups during the Go trials were not statistically significant. Furthermore, NoGo current density across both groups revealed significantly more activation in bilateral anterior cingulate cortical (ACC) areas, with the maximum activation in the right cingulate regions. However, the magnitude of this difference was much less in alcoholics compared to control subjects. These findings suggest that alcoholics may have deficits in effortful processing during the motor response and its inhibition, suggestive of possible frontal lobe dysfunction.

PDF file of the publication on ResearchGate:

J. Derringer, R. F. Krueger, N. Manz, B. Porjesz, L. Almasy, E. Bookman, H. J. Edenberg, J. R. Kramer, J. A. Tischfield, GENEVA consortium, and L. J. Bierut
"Non-replication of an association of SGIP1 SNPs with alcohol dependence and theta EEG power"
Psychiatric Genetics 21 (2011), 265-266.

Abstract:
A recent study in a sample of Plains Indians showed association between eight single nucleotide polymorphisms (SNPs) located in the SGIP1 gene and
resting y electroencephalogram (EEG) power. This association appeared to generalize to alcohol use disorders, for which EEG power is a potential
endophenotype. We analyzed a large, diverse sample for replication of the association of these implicated SGIP1 SNPs (genotyped on the Illumina 1M platform) with alcohol dependence (N=3988) and y EEG power (N=1066). We found no evidence of association of the earlier implicated SGIP1 SNPs with either alcohol dependence or y EEG power (all P > 0.15) in this sample. The earlier implicated SNPs located in SGIP1 gene showed no association with alcohol dependence or y EEG power in this sample of individuals with European and/or African ancestry. This failure to replicate may be the result of differences in ancestry between this sample and the original sample.

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M. Zlojutro, N. Manz, M. Rangaswamy, X. Xuei, L. Flury-Wetherill, D. Koller, L. J. Bierut, A. Goate, V. Hesselbrock, S. Kuperman, J. Nurnberger Jr., J. P. Rice, M. A. Schuckit, T. Foroud, H. J. Edenberg, B. Porjesz, and L. Almasy
"Genome-wide association study of theta band event-related oscillations identifies serotonin receptor gene HTR7 influencing risk of alcohol dependence"
American Journal of Medical Genetics Part B: Neuropsychiatric Genetics 156 (2011), 44-58.

Abstract
Event-related brain oscillations (EROs) represent highly heritable neuroelectrical correlates of human perception and cognitive performance that exhibit marked deficits in patients with various psychiatric disorders. We report the results of the first genome-wide association study (GWAS) of an ERO endophenotype - frontal theta ERO evoked by visual oddball targets during P300 response in 1,064 unrelated individuals drawn from a study of alcohol dependence. Forty-two SNPs of the Illumina HumanHap 1M microarray were selected from the theta ERO GWAS for replication in family-based samples (N¼1,095), with four markers revealing nominally significant association. The most significant marker from the two-stage study is rs4907240 located within ARID protein 5A gene (ARID5A) on chromosome 2q11 (unadjusted, Fisher’s combined P=3.68×10-6).However, the most intriguing association to emerge is with rs7916403 in serotoninreceptor geneHTR7onchromosome 10q23 (combined P=1.53×10-4), implicating the serotonergic system in the
neurophysiological underpinnings of theta EROs. Moreover, promising SNPs were tested for association with diagnoses of alcohol dependence (DSM-IV), revealing a significant relationship with the HTR7 polymorphism among GWAS case–controls (p=0.008). Significant recessive genetic effects were also
detected for alcohol dependence in both case–control and family -based samples (p=0.031 and 0.042, respectively), with the HTR7 risk allele corresponding to theta ERO reductions among homozygotes. These results suggest a role of the serotonergic system in the biological basis of alcohol dependence and underscore the utility of analyzing brain oscillations as a powerful approach to understanding complex genetic psychiatric disorders.

PDF file of the publication on ResearchGate:

C. Kamarajan, M. Rangaswamy, Y. Tang, D. B. Chorlian, A. K. Pandey, B. N. Roopesh, N. Manz, R. Saunders, A. T. Stimus, and B. Porjesz
"Dysfunctional reward processing in male alcoholics: An ERP study during a gambling task"
Journal of Psychiatric Research 44 (2010), 576-590.

Abstract
Objective: A dysfunctional neural reward system has been shown to be associated with alcoholism. The current study aims to examine reward processing in male alcoholics by using event-related potentials (ERPs) as well as behavioral measures of impulsivity and risk-taking.
Methods: Outcome-related negativity (ORN/N2) and positivity (ORP/P3) derived from a single outcome gambling task were analyzed using a mixed model procedure. Current density was compared across groups and outcomes using standardized low resolution electromagnetic tomography (sLORETA). Behavioral scores were also compared across groups. Correlations of ERP factors with behavioral and impulsivity factors were also analyzed.
Results: Alcoholics showed significantly lower amplitude than controls during all outcome conditions for the ORP component and decreased amplitude during the loss conditions for the ORN component. Within conditions, gain produced higher amplitudes than loss conditions. Topographically, both groups had an anterior focus during loss conditions and posterior maxima during gain conditions, especially for the ORN component. Decreased ORP current density at cingulate gyrus and less negative ORN current density at sensory and motor areas characterized the alcoholics. Alcoholics had higher levels of impulsivity and risk-taking features than controls.
Conclusions: Deficient outcome/reward processing and increased impulsivity and risk-taking observed in alcoholics may be at least partly due to reward deficiency and/or dysfunctional reward circuitry in the brain, suggesting that alcoholism can be considered as part of the cluster of the reward deficiency syndrome (RDS).

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A. C. H. Chen, N. Manz, Y. Tang, M. Rangaswamy, L. Almasy, S. Kuperman, J. Nurnberger Jr, S. J. O'Connor, H. J. Edenberg, M. A. Schuckit, J. Tischfield, T. Foround, L. Bierut, J. Rohrbaugh, J. P. Rice, A. Goate, V. Hesselbrock, and B. Porjesz
"Single Nucleotide Polymorphisms in Corticotropin Releasing Hormone Receptor 1 Gene (CRHR1) Are Associated with Quantitative Traits of Event-Related Potential and Alcohol Dependence"
Alcoholism: Clinical and Experimental Research 34 (2010), 988-996.

Abstract

Background: Endophenotypes reflect more proximal effects of genes than diagnostic categories, hence providing a more powerful strategy in searching for genes involved in complex psychiatric disorders. There is strong evidence suggesting the P3 amplitude of the event-related potential (ERP) as an endophenotype for the risk of alcoholism and other disinhibitory disorders. Recent studies demonstrated a crucial role of corticotropin releasing hormone receptor 1 (CRHR1) in the environmental stress response and ethanol self-administration in animal models. The aim of the present study was to test the potential associations between single-nucleotide polymorphisms (SNPs) in the CRHR1 gene and the quantitative trait, P3 amplitude during the processing of visual target signals in an oddball paradigm, as well as alcohol dependence diagnosis. Methods: We analyzed a sample from the Collaborative Study on the Genetics of Alcoholism (COGA) comprising 1049 Caucasian subjects from 209 families (including 472 alcohol-dependent individuals). Quantitative transmission disequilibrium test (QTDT) and family-based association test (FBAT) were used to test the association, and false discovery rate (FDR) was applied to correct for multiple comparisons.
Results: Significant associations (p < 0.05) were found between the P3 amplitude and alcohol dependence with multiple SNPs in the CRHR1 gene.
Conclusions: Our results suggest that CRHR1 may be involved in modulating the P3 component of the ERP during information processing and in vulnerability to alcoholism. These findings underscore the utility of electrophysiology and the endophenotype approach in the genetic study of psychiatric disorders.

PDF file of the publication on ResearchGate:

C. Kamarajan, B. Porjesz, M. Rangaswamy, Y. Tang, D. B. Chorlian, A. Padmanabhapillai, R. Saunders, A. K. Pandey, B. N. Roopesh, N. Manz, A. T. Stimus, and H. Begleiter
"Brain signatures of monetary loss and gain: outcome-related potentials in a single outcome gambling task"
Behavioural Brain Research 197 (2009), 62-76.

Abstract
This study evaluates the event-related potential (ERP) components in a single outcome gambling task that involved monetary losses and gains. The participants were 50 healthy young volunteers (25 males and 25 females). The gambling task involved valence (loss and gain) and amount (50¢ and 10¢) as outcomes. The outcome-related negativity (ORN/N2) and outcome-related positivity (ORP/P3) were analyzed and compared across conditions and gender. Monetary gain (compared to loss) and higher amount (50¢ compared to 10¢) produced higher amplitudes and shorter latencies in both ORN and ORP components. Difference wave plots showed that earlier processing (200–400 ms) is dominated by the valence (loss/gain) while later processing (after 400 ms) is marked by the amount (50¢/10¢). Functional mapping using Low Resolution Electromagnetic Tomography (LORETA) indicated that the ORN separated the loss against gain in both genders, while the ORP activity distinguished the 50¢ against 10¢ in males. This study further strengthens the view that separate brain processes/circuitry may mediate loss and gain. Although there were no gender differences in behavioral and impulsivity scores, ORN and ORP measures for different task conditions had significant correlations with behavioral scores. This gambling paradigm may potentially offer valuable indicators to study outcome processing and impulsivity in normals as well as in clinical populations.

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C. Kamarajan, M. Rangaswamy, D. B. Chorlian, N. Manz, Y. Tang, A. K. Pandey, B. N. Roopesh, A. T. Stimus, and B. Porjesz
"Theta oscillations during the processing of monetary loss and gain: A perspective on gender and impulsivity"
Brain Research 1235 (2008), 45-62.

Abstract
Event-related oscillations (EROs) have proved to be very useful in the understanding of a variety of neurocognitive processes including reward/outcome processing. In the present study, theta power (4.0–7.0 Hz) following outcome stimuli in the time window of the N2–P3 complex (200–500 ms) was analyzed in healthy normals (20 males and 20 females) while performing a gambling task that involved monetary loss and gain. The main aim was to analyze outcome processing in terms of event-related theta power in the context of valence, amount, gender, and impulsivity. The S-transform was used for the signal processing of the ERO data in terms of time–frequency–power. Results from filtered waveforms showed a partially consistent phase-alignment of the increased theta activity corresponding to N2 and P3 components following the outcome stimuli. Gain conditions produced more theta power than loss conditions. While there was anterior involvement in both gain and loss, posterior activation was stronger during gain conditions than during loss conditions.
Females exhibited posterior maxima during gain conditions while males had an anterior maxima during both loss and gain conditions. The current source density of theta activity in females involved larger areas with a bilateral frontal activity while males predominantly had a frontal midline activity. Theta power was significantly higher in females than males across all conditions. Low theta (4.0–5.5 Hz) predominantly contributed to the posterior activity during gain conditions. High theta (5.5–7.0 Hz) was more associated with impulsivity measures than low theta activity. These findings may offer valuable clues to understand outcome processing, impulsivity, and gender differences.

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Publications in 'Environmental Radioactivity':

 


Non peer-reviewed publications

A. Honig, N. Manz, A. Paul, S. Röttger und U. Keyser
"Radondiffusion unterschiedlicher Schlauchmaterialien" ("Radon diffusion through different tube materials")
Jahresbericht der Physikalisch-Technischen-Bundesanstalt 1998, 2.6.4 (1999), 250-251

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N. Manz
"Aufbau und Optimierung einer Vieldraht-Impuls-Ionisationskammer zur Messung niedriger Radonaktivitätskonzentrationen in Luft" ("Construction and optimization of a multi-wire impulse ionization chamber to measure low-level radon activity concentrations in air''")
Diplom-Arbeit (1997)

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