Development of attentional processes in ADHD and normal children

Attention Deficit Hyperactivity Disorder (ADHD) is a developmental disorder. Typical development of attentional processes is rapid during early childhood. ADHD results in impairment in response inhibition, error monitoring, attentional disengagement, executive attention, and delay aversion and may effect the ongoing development of these processes during childhood. We examined the development of attentional processes in children with ADHD and normal children. Two hundred forty children (120 in each group) in the age range of 6–9 years participated in the study. Four tasks: Stop-Signal, attentional disengagement, attention network, and choice delay task were administered. Stop signal reaction time, switch costs, conflict effect, and percentage choice of short delay reward was higher in ADHD group compared to normal group. Post error of slowing was less in ADHD children. Endogenous orienting effect was more in normal children compared to ADHD children. Different developmental trajectories were observed for control functions in normal children. Major development in response inhibition occurred in 7–8 years, error monitoring in 6–9 years, and attentional disengagement in 7–9 years. Late development in alerting network was observed in normal children at age 9 years. No developmental changes occurred on these control functions in ADHD children aged 6–9 years. Age related changes were observed on delay aversion between 6 and 9 years in normal children, while it changed between 6 and 7 years in ADHD children. Performance was not changed on orienting and conflict attentional networks in both the children except conflict effect reduced between 7 and 9 years in ADHD children under double cue condition. Conflict network was interacted with the alerting and orienting network in normal children; specifically conflict network interacted with the orienting network in younger children (age 6 years) and with alerting network in older children (age 9 years). In ADHD group interaction between alerting and conflict network was observed only in the double cue condition. Together these results indicated that the deficits in control processes accumulate with age in ADHD children Present study favors the conceptual view of ADHD as a stable deficit in cognitive control functions, which are implicated in the pathology of ADHD. These results have theoretical implication for the theories of executive control and ADHD

Interpretative Bias: Indicators of Cognitive Vulnerability to Depression

Objectives: The study aimed at testing the existence of interpretative bias in remitted depressives as compared to unipolar depressives and never-depressed individuals. Method: Cognitive Bias Questionnaire was administered on 10 individuals each with unipolar depression, remitted depression, and never-depressed participants. Participants were presented with vague and ambiguous vignettes of potentially problematic situation that individuals often encounter their daily lives. Each vignette is followed by four questions with four response options reflecting a depressed-distorted, depressed-nondistorted, nondepressed-distorted, or nondepressed- nondistorted option. Participants choose the response option that best represents how they would respond to the situation if it actually happened to them. Results: Unipolar depressives interpret their condition as high on depressive mood symptoms as well as distorted thoughts whereas remitted depressives interpret their condition as high on distorted thoughts alone. Conclusions: It may suggest that despite of reduction in level of symptomatic severity of depression, cognitive errors are still maintained during remission, can increase one’s vulnerability for relapse. It implies that management of depression should focus on reducing cognitive vulnerability to depression, rather than only targeting a reduction in the symptoms

Development of Task Switching and Post-Error Slowing in Children

Background: Executive control processes such as task switching and error processing have been shown to change with age. The present study explored from a developmental perspective whether shared or different mechanisms underlie these processes. Methods: The sample included 180 children (30 in each of the six age groups from 6-11 years) who were required to perform two different tasks: identification of a digit, or counting the number of digits. We computed switch costs as a function of response-repetition, stimulus-response (S-R) compatibility, and post-error-slowing. We also analyzed reaction time distributions. Results and discussion: The results showed a switch cost in the response-repetition condition, with a reduction in switch cost between 7 to 8 and 9 to 10 years of age, and an S-R compatibility effect in 6 to 9 years old children. Reaction time (RT) distributions showed that the decrement in the switch cost is due to the overall decrease in RTs in fast (5th percentile) trials in 9 to 11 year olds, and slow (95th percentile) trials in 7 to 8 and 9 to 11 years old children, in both the task switch and non-switch trials. A major reduction in RT was found between 9 to 11 years in both the response type and S-R compatibility type conditions. RT distributions for post-error trials revealed that the large decrement seen in 7 to 8 and 9 to 10 years old children is primarily due to the sudden decrease in RTs in the fast and slow trials respectively. The developmental pattern of error processing was similar to one component of task switching (switch cost of the response-repetition condition), indicating that inhibition could be a common mechanism underlying both the processes. However, the failure to maintain task set was found only with task switching. Conclusion: The development of task switching and error processing is not gradual. The developmental pattern of error processing is similar to that of the switch cost of the responserepetition condition in task switching, indicating that inhibition could be a common mechanism underlying both processes. The present results have implications for theories of executive control

Nonlinear DC-response in Composites: a Percolative Study

The DC-response, namely the $I$-$V$ and $G$-$V$ charateristics, of a variety of composite materials are in general found to be nonlinear. We attempt to understand the generic nature of the response charactersistics and study the peculiarities associated with them. Our approach is based on a simple and minimal model bond percolative network. We do simulate the resistor network with appropritate linear and nonlinear bonds and obtain macroscopic nonlinear response characteristics. We discuss the associated physics. An effective medium approximation (EMA) of the corresponding resistor network is also given.Comment: Text written in RevTEX, 15 pages (20 postscript figures included), submitted to Phys. Rev. E. Some minor corrections made in the text, corrected one reference, the format changed (from 32 pages preprint to 15 pages

Occurrence & nucleotide sequence analysis of hepatitis G virus in patients with acute viral hepatitis & fulminant hepatitis

Background & objectives: Association of hepatitis G virus (HGV) with acute viral hepatitis (AVH) and fulminant hepatitis (FH) is not clearly understood.This study was designed to asses the occurrence of HGV infection and its relationship with other hepatotropic viruses in patients with FH and AVH and also to determine the nucleotide sequence of HGV isolates. Methods: The study included 100 patients of FH and 125 of AVH on the basis of clinical examination, liver function test and serology for hepatitis A, B, C and E virus. HGV RNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and direct sequencing for 4 randomly selected samples followed by phylogenetic analysis. Results: Of the 100 patients with FH, 30 were negative for hepatitis viruses A, B, C and E by serology (non A - non E) while 60 were negative in the AVH group. In the non A- non -E hepatitis group, HGV was positive in 16.66 per cent (5/30) cases of FH, 10 per cent (6/60) cases of AVH and 6 per cent (6/100) of healthy controls. The difference in HGV seropositivity between FH and AVH patients was statistically not significant compared to healthy controls, while HBV and HCV infections were significant. The four isolates sequenced seemed to be of same type and close to Chinese strain of HGV (Y13755.1 Y13756.1 Y15407, and U67782) on phylogeny. Interpretation & conclusion: In HGV infection was not found to be clinically significant as well as nonpathogenic in the patients of FH and AVH and appeared to be an innocent bystander in the course of the disease. The four sequenced HGV isolates showed close pairing with Chinese strains

Symmetry, Gravity and Noncommutativity

We review some aspects of the implementation of spacetime symmetries in noncommutative field theories, emphasizing their origin in string theory and how they may be used to construct theories of gravitation. The geometry of canonical noncommutative gauge transformations is analysed in detail and it is shown how noncommutative Yang-Mills theory can be related to a gravity theory. The construction of twisted spacetime symmetries and their role in constructing a noncommutative extension of general relativity is described. We also analyse certain generic features of noncommutative gauge theories on D-branes in curved spaces, treating several explicit examples of superstring backgrounds.Comment: 52 pages; Invited review article to be published in Classical and Quantum Gravity; v2: references adde

Comparison between the two models of dephasing in mesoscopic systems

In mesoscopic systems to study the role of inelastic scattering on the phase coherent motion of electrons two phenomenological models have been proposed. In the first one, due to B\"uttiker, one adds a voltage probe into the system (or in the scattering matrix). The second model invokes the complex (or optical) potential in the system Hamiltonian. Studying a simple geometry of a metallic loop in the presence of Aharonov-Bohm magnetic flux, we show that the two probe conductance is symmetric in the reversal of the magnetic field in B\"uttiker's approach. Whereas the two probe conductance within the complex potential model is asymmetric in the magnetic flux reversal contrary to the expected behavior.Comment: 11 pages RevTex, 4 figures inculded, Communicated to PR

Evidence of Coronavirus (CoV) Pathogenesis and Emerging Pathogen SARS-CoV-2 in the Nervous System: A Review on Neurological Impairments and Manifestations.

The coronavirus disease 2019 (COVID-19) pandemic is an issue of global significance that has taken the lives of many across the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for its pathogenesis. The pulmonary manifestations of COVID-19 have been well described in the literature. Initially, it was thought to be limited to the respiratory system; however, we now recognize that COVID-19 also affects several other organs, including the nervous system. Two similar human coronaviruses (CoV) that cause severe acute respiratory syndrome (SARS-CoV-1) and Middle East respiratory syndrome (MERS-CoV) are also known to cause disease in the nervous system. The neurological manifestations of SARS-CoV-2 infection are growing rapidly, as evidenced by several reports. There are several mechanisms responsible for such manifestations in the nervous system. For instance, post-infectious immune-mediated processes, direct virus infection of the central nervous system (CNS), and virus-induced hyperinflammatory and hypercoagulable states are commonly involved. Guillain-Barré syndrome (GBS) and its variants, dysfunction of taste and smell, and muscle injury are numerous examples of COVID-19 PNS (peripheral nervous system) disease. Likewise, hemorrhagic and ischemic stroke, encephalitis, meningitis, encephalopathy acute disseminated encephalomyelitis, endothelialitis, and venous sinus thrombosis are some instances of COVID-19 CNS disease. Due to multifactorial and complicated pathogenic mechanisms, COVID-19 poses a large-scale threat to the whole nervous system. A complete understanding of SARS-CoV-2 neurological impairments is still lacking, but our knowledge base is rapidly expanding. Therefore, we anticipate that this comprehensive review will provide valuable insights and facilitate the work of neuroscientists in unfolding different neurological dimensions of COVID-19 and other CoV associated abnormalities