Amar Sarkar

Cognitive Enhancement or Cognitive Cost: Trait-Specific Outcomes of Brain Stimulation in the Case of Mathematics Anxiety

The surge in noninvasive brain stimulation studies investigating cognitive enhancement has neglected the effect of interindividual differences, such as traits, on stimulation outcomes. Using the case of mathematics anxiety in a sample of healthy human participants in a placebo-controlled, double-blind, crossover experiment, we show that identical transcranial direct current stimulation (tDCS) exerts opposite behavioral and physiological effects depending on individual trait levels. Mathematics anxiety is the negative emotional response elicited by numerical tasks, impairing mathematical achievement. tDCS was applied to the dorsolateral prefrontal cortex, a frequent target for modulating emotional regulation. It improved reaction times on simple arithmetic decisions and decreased cortisol concentrations (a biomarker of stress) in high mathematics anxiety individuals. In contrast, tDCS impaired reaction times for low mathematics anxiety individuals and prevented a decrease in cortisol concentration compared with sham stimulation. Both groups showed a tDCS-induced side effect—impaired executive control in a flanker task—a cognitive function subserved by the stimulated region. These behavioral and physiological double dissociations have implications for brain stimulation research by highlighting the role of individual traits in experimental findings. Brain stimulation clearly does not produce uniform benefits, even applied in the same configuration during the same tasks, but may interact with traits to produce markedly opposed outcomes.

Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals

Psychobiotics were previously defined as live bacteria (probiotics) which, when ingested, confer mental health benefits through interactions with commensal gut bacteria. We expand this definition to encompass prebiotics, which enhance the growth of beneficial gut bacteria. We review probiotic and prebiotic effects on emotional, cognitive, systemic, and neural variables relevant to health and disease. We discuss gut–brain signalling mechanisms enabling psychobiotic effects, such as metabolite production. Overall, knowledge of how the microbiome responds to exogenous influence remains limited. We tabulate several important research questions and issues, exploration of which will generate both mechanistic insights and facilitate future psychobiotic development. We suggest the definition of psychobiotics be expanded beyond probiotics and prebiotics to include other means of influencing the microbiome.

Mathematics Anxiety: What Have We Learned in 60 Years?

The construct of mathematics anxiety has been an important topic of study at least since the concept of “number anxiety” was introduced by Dreger and Aiken (1957), and has received increasing attention in recent years. This paper focuses on what research has revealed about mathematics anxiety in the last 60 years, and what still remains to be learned. We discuss what mathematics anxiety is; how distinct it is from other forms of anxiety; and how it relates to attitudes to mathematics. We discuss the relationships between mathematics anxiety and mathematics performance. We describe ways in which mathematics anxiety is measured, both by questionnaires, and by physiological measures. We discuss some possible factors in mathematics anxiety, including genetics, gender, age, and culture. Finally, we describe some research on treatment. We conclude with a brief discussion of what still needs to be learned.

Individual differences and specificity of prefrontal gamma frequency-tACS on fluid intelligence capabilities.

Emerging evidence suggests that transcranial alternating current stimulation (tACS) is an effective, frequency-specific modulator of endogenous brain oscillations, with the potential to alter cognitive performance. Here, we show that reduction in response latencies to solve complex logic problem indexing fluid intelligence is obtained through 40 Hz-tACS (gamma band) applied to the prefrontal cortex. This improvement in human performance depends on individual ability, with slower performers at baseline receiving greater benefits. The effect could have not being explained by regression to the mean, and showed task and frequency specificity: it was not observed for trials not involving logical reasoning, as well as with the application of low frequency 5 Hz-tACS (theta band) or non-periodic high frequency random noise stimulation (101-640 Hz). Moreover, performance in a spatial working memory task was not affected by brain stimulation, excluding possible effects on fluid intelligence enhancement through an increase in memory performance. We suggest that such high-level cognitive functions are dissociable by frequency-specific neuromodulatory effects, possibly related to entrainment of specific brain rhythms. We conclude that individual differences in cognitive abilities, due to acquired or developmental origins, could be reduced during frequency-specific tACS, a finding that should be taken into account for future individual cognitive rehabilitation studies.

Transcranial electrical stimulation and numerical cognition.

The effects of transcranial electrical stimulation (tES) have been documented for a variety of mental functions, including numerical cognition. This article first reviews 2 prominent forms of tES, transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS). This is followed by an assessment of the applications of this technology in the enhancement of aspects of numerical cognition, including numerosity, magnitude representation, and more complex arithmetic operations. The review concludes with discussions of directions for future research. These include the need to take individual differences into account in experimental designs, extending research to individuals with difficulties and deficits in working with numbers, the need to consider potential cognitive costs that may offset cognitive benefits of tES. A recurring theme in this article is the need to move toward greater ecological validity of experimental findings.

Sacred Slaughter: An Analysis of Historical, Communal, and Constitutional Aspects of Beef Bans in India

ABSTRACT Cow protection is not new to India. However, the political ascendancy of the Bharatiya Janata Party and by extension, that of its parent organization, the Rashtriya Swayamsevak Sangh, gives new force to beef bans. These have significant consequences for the religious freedom and material welfare of India’s minorities. The article locates the beef bans among rising Hindu chauvinist trends, and examines the textual, communal, and historical antecedents of cow protection. We subject the bans to the essentials of religion test which the state has used to resolve contentious religious issues in the past, finding that proscriptions on beef consumption are not essential components of Hindu religious practice. The beef bans are also emboldening violence by fringe groups such as cow vigilantes. Though ostensibly supported by the Constitution and enacted in order to protect Hindu sensibilities, in practice beef bans endorse an excessively narrow, Brahmanical form of Hinduism—Hindutva—while simultaneously impoverishing the material, religious, and physical well-being of minority communities such as Muslims and Dalits. The cumulative effect is totalitarian and inimical to the democratic and secular foundations of the Indian state.

The Microbiome in Psychology and Cognitive Neuroscience

Psychology and microbiology make unlikely friends, but the past decade has witnessed striking bidirectional associations between intrinsic gut microbes and the brain, relationships with largely untested psychological implications. Although microbe-brain relationships are receiving a great deal of attention in biomedicine and neuroscience, psychologists have yet to join this journey. Here, we illustrate microbial associations with emotion, cognition, and social behavior. However, despite considerable enthusiasm and potential, technical and conceptual limitations including low statistical power and lack of mechanistic descriptions prevent a nuanced understanding of microbiome-brain-behavior relationships. Our goal is to describe microbial effects in domains of cognitive significance and the associated challenges to stimulate interdisciplinary research on the contribution of this hidden kingdom to psychological processes.

The impact of using documented but uncharged offense data on JSORRAT-II predictive validity

Following the implementation of sexual offender notification laws, researchers have found a drop in the rate of prosecutions and an increase in plea bargains for sexual offenses committed by male juveniles. This type of prosecutorial hesitation has implications for the predictive validity of sexual recidivism risk assessments, such as the Juvenile Sexual Offender Recidivism Risk Assessment Tool–II (JSORRAT-II), that require data from officially adjudicated offenses in the scoring of several items. The present study sought to test the impact of including data from documented but uncharged (DBU) sexual offenses in the scoring of the JSORRAT-II on its predictive validity using an exhaustive sample of 1,095 juveniles who offended sexually from the states of Iowa and Utah. Although sexual recidivists had significantly more DBU data, the inclusion of those data did not improve the predictive validity of the tool. The authors discuss additional reasons why changes in prosecutorial practice might remain confound in risk assessment studies and suggest future research to investigate those hypotheses.

Transcranial Electrical Stimulation and the Enhancement of Numerical Cognition

Transcranial electrical stimulation (tES) is being employed as a tool for cognitive enhancement in an increasing number of research studies. Its effects have been noted in a range of psychological functions, including numerical cognition and learning. This chapter first presents the historical background, technical principles, and limitations that contextualize modern tES experiments, and then considers how this technology has been applied in the enhancement of numerical cognition. The populations considered here include individuals with normal numerical abilities, such as judging numerosity, perceiving and comparing magnitudes, and carrying out more advanced arithmetic operations, as well as individuals with serious difficulties in working with numbers, as seen in mathematics anxiety and developmental dyscalculia. The chapter concludes with a consideration of important directions that research may take in the future. The emphasis throughout is the need to test the ecological validity of tES-induced cognitive benefits, which is particularly important in the context of an ever-increasing number of positive reports, both in the media and in academia. However, enhancements in healthy individuals have been restricted entirely to controlled laboratory settings. The essential bridge between using tES to enhance numerical cognition in the laboratory and the enhancement of mathematical achievement in educational or occupational settings has yet to be built. As this chapter illustrates, the steady accumulation of evidence is providing firmer ground to begin explorations of the ecological validity of tES interventions.