Anuradha Sharma

Intraindividual variability in inhibitory function in adults with ADHD - an ex-Gaussian approach

Objective Attention deficit disorder (ADHD) is commonly associated with inhibitory dysfunction contributing to typical behavioral symptoms like impulsivity or hyperactivity. However, some studies analyzing intraindividual variability (IIV) of reaction times in children with ADHD (cADHD) question a predominance of inhibitory deficits. IIV is a measure of the stability of information processing and provides evidence that longer reaction times (RT) in inhibitory tasks in cADHD are due to only a few prolonged responses which may indicate deficits in sustained attention rather than inhibitory dysfunction. We wanted to find out, whether a slowing in inhibitory functioning in adults with ADHD (aADHD) is due to isolated slow responses. Methods Computing classical RT measures (mean RT, SD), ex-Gaussian parameters of IIV (which allow a better separation of reaction time (mu), variability (sigma) and abnormally slow responses (tau) than classical measures) as well as errors of omission and commission, we examined response inhibition in a well-established GoNogo task in a sample of aADHD subjects without medication and healthy controls matched for age, gender and education. Results We did not find higher numbers of commission errors in aADHD, while the number of omissions was significantly increased compared with controls. In contrast to increased mean RT, the distributional parameter mu did not document a significant slowing in aADHD. However, subjects with aADHD were characterized by increased IIV throughout the entire RT distribution as indicated by the parameters sigma and tau as well as the SD of reaction time. Moreover, we found a significant correlation between tau and the number of omission errors. Conclusions Our findings question a primacy of inhibitory deficits in aADHD and provide evidence for attentional dysfunction. The present findings may have theoretical implications for etiological models of ADHD as well as more practical implications for neuropsychological testing in aADHD.

Event-related potentials during recognition of semantic and pictorial food stimuli in patients with anorexia nervosa and healthy controls with varying internal states of hunger.

Objective To elucidate maladaptive central processing of food cues during recognition tasks in anorexia nervosa (AN), while considering influences of nutritional preload and presentation modality (word versus picture). Methods Event-related potentials to food-related word and pictorial stimuli were assessed during recognition tasks in 16 patients with AN, 16 control participants with food intake before the study, and 16 control participants with a fasting period before the study. Results Patients with AN showed a P3b amplitude reduction especially at the midline parietal site compared with satiated controls (5.7 [standard deviation = 3.3] versus 8.7 [3.1] &mgr;V, p < .03). Subtle recognition deficits in patients with AN were indicated by smaller “old/new” effects compared with satiated (p = .049) and fasting controls (p < .003) for pictorial stimuli. Hunger-modulated enhanced old/new effects for food pictures compared with neutral pictorial stimuli could be observed in fasting controls only (2.7 [2.6] versus 0.8 [2.2] &mgr;V, p < .01). Conclusions The presented data provide evidence for a midline parietal P3b amplitude reduction in patients with AN, which might point to reduced network activation in AN even during satiety. Observed subtle recognition deficits either represent a stable trait characteristic or a “scar” effect of chronic starvation that may play a role in the development and/or persistence of the disorder.

Relationship between serum calcium and neuropsychological performance might indicate etiological heterogeneity underlying cognitive deficits in schizophrenia and depression

Cognitive dysfunction is a core feature of schizophrenia spectrum and depressive disorders. Influx of extracellular calcium is essential for neuronal processes such as pre-synaptic neurotransmitter release and NMDA receptor mediated neuroplasticity. Since serum and brain interstitial fluids maintain equilibrium for ion concentrations via passive diffusion, the amount of peripheral calcium could affect neuronal and hence cognitive function. Within the physiological norm-levels, we hypothesized higher serum-calcium would be associated with better neuropsychological performance in patients diagnosed with schizophrenia or depression. One-tailed Pearsons correlations were calculated between total serum-calcium levels and performance on an extensive computer-based neuropsychological test battery. Influence of covariates was assessed using linear regression. Serum calcium was significantly and positively correlated with neuropsychological composite, information processing speed, executive function and global assessment of functioning (GAF) in depression patients but not in schizophrenia patients. Amongst covariates, age associated significantly with serum calcium and neuropsychological functioning in depression but only with serum calcium in schizophrenia group. The study provides first evidence for a positive relationship between serum calcium and neuropsychological/daily-life function in depression. Absence of this correlation in schizophrenia could point to etiological heterogeneity concerning calcium-related processes underlying cognitive deficits in these disorders.

Genetic Liability to Schizophrenia Measured by P300 in Concordant and Discordant Monozygotic Twins

Background: Differential effects of genes and environment can contribute to etiological heterogeneity in schizophrenia. Twins concordant and discordant for schizophrenia may differ in genetic predisposition to schizophrenia with concordant twins having a higher genetic liability and discordant twins having a lower genetic liability to schizophrenia. We aimed to investigate whether P300 amplitude (which has been postulated as a genetic marker for schizophrenia) reflected this heterogeneity. Sampling and Methods: We compared P300 amplitudes across 36 monozygotic twin pairs (6 concordant for schizophrenia/schizoaffective disorder, 11 discordant and 19 healthy control pairs) performing an auditory oddball task, using multiple regression (age, gender, birth order, premorbid IQ as covariates). We further looked at the correlation between the Brief Psychiatric Rating Scale (BPRS) and P300 amplitude in affected twins, and compared concordant and discordant affected twins on the Global Assessment Scale (GAS). Results: Multiple regression yielded a highly significant model (p = 0.004) though the explained variance was limited (21%). The main effect of the group on P300 amplitude was significant (p = 0.0001): affected concordant twins showed a significantly lower P300 amplitude as compared to affected discordant (p = 0.005, Cohen’s d = 1.08) and control twins (p = 0.000, d = 1.16). Discordant affected and unaffected twins did not differ significantly from each other or from control twins. P300 did not correlate significantly with the BPRS and the affected groups did not differ across the GAS. Conclusions: Our results provide evidence for etiological heterogeneity within schizophrenia pointing to different pathophysiological mechanisms that may underlie more and less genetically determined forms of schizophrenia. They also indicate that P300 correlates with a differing degree of genetic liability to schizophrenia independently of the psychopathological status and even in the presence of similar functional profiles.

Perception of facial expressions of emotion in migraine

Both lower-level perceptual changes and especially higher-level cognitive alterations in individuals with migraine are poorly understood. Here, we behaviorally and electrophysiologically investigated the perception of emotional facial expressions in migraine. Young female individuals with migraine and healthy controls watching neutral faces gradually shifting to either happy, fearful, or angry expressions were asked to classify the facial expressions as quickly and accurately as possible by pressing a corresponding button, and to keep looking at the face until the last frame disappeared. Migraine individuals, compared to healthy controls, had a reduced habituation in the N170 time interval towards a gradually emerging emotional expression. The early P1, the early posterior negativity (EPN), and the late positive potential (LPP) amplitudes were not statistically different between groups and among expressions. The mean reaction time for recognizing an expression did not differ between groups and it was not at a cost of more incorrect responses. Interestingly, the amplitude of the early posterior negativity correlated negatively with the time interval since the last attack. It is concluded that young female individuals with migraine, compared to healthy controls, do not show a biased emotional facial processing toward positive or negative expressions.

Abnormal N400 Semantic Priming Effect May Reflect Psychopathological Processes in Schizophrenia : A Twin Study

Objective Activation of semantic networks is indexed by the N400 effect. We used a twin study design to investigate whether N400 effect abnormalities reflect genetic/trait liability or are related to psychopathological processes in schizophrenia. Methods We employed robust linear regression to compare N400 and behavioral priming effects across 36 monozygotic twin pairs (6 pairs concordant for schizophrenia/schizoaffective disorder, 11 discordant pairs, and 19 healthy control pairs) performing a lexical decision task. Moreover, we examined the correlation between Brief Psychiatric Rating Scale (BPRS) score and the N400 effect and the influence of medication status on this effect. Results Regression yielded a significant main effect of group on the N400 effect only in the direct priming condition (p = 0.003). Indirect condition and behavioral priming effect showed no significant effect of group. Planned contrasts with the control group as a reference group revealed that affected concordant twins had significantly reduced N400 effect compared to controls, and discordant affected twins had a statistical trend for reduced N400 effect compared to controls. The unaffected twins did not differ significantly from the controls. There was a trend for correlation between reduced N400 effect and higher BPRS scores, and the N400 effect did not differ significantly between medicated and unmedicated patients. Conclusions Reduced N400 effect may reflect disease-specific processes in schizophrenia implicating frontotemporal brain network in schizophrenia pathology.

Contents / Acknowledgement Vol. 44, 2011

R. Bentall, Manchester C.E. Berganza, Guatemala City D. Bhugra, London C. Brewin, London Y.-F. Chen, Beijing D. Clark, London N.M.J. Edelstyn, Keele H. Fabisch, Graz K. Fabisch, Graz P. Falkai, Göttingen H.J. Freyberger, Greifswald/Stralsund N. Ghaemi, Boston, Mass. C. Haasen, Hamburg A. Heerlein, Santiago P. Henningsen, München P. Hoff , Zürich Y. Kim, Tokyo A. Marneros, Halle/Saale M. Musalek, Wien F. Poustka, Frankfurt/Main J. Raboch, Prague P. Salkovskis, London I.M. Salloum, Miami, Fla. F. Schneider, Aachen J.C. Soares, Chapel Hill, N.C. J.S. Strauss, New Haven, Conn. E. Vieta, Barcelona M. Weisbrod, Karlsbad Official Journal of the World Psychiatric Association (WPA),