Naloxone modulates visual judgments of similarity but not dissimilarity

Impact of short-term meditation and expectation on executive brain functions

Meditation improves executive functions such as attention and working memory processes. However, it remains unclear to what extent contextual effects contribute to these improvements, since the role of meditation-associated expectations has not been investigated so far. In a randomized, single-blind, deceptive, between-subject design we compared the impact of short-term meditation (MG) on executive functioning with an expectation (ECG) and a passive control group (CG) as well as the effect of positive and negative outcome expectations. Fifty-nine healthy meditation-naïve volunteers participated on three consecutive days (20 min/session). Five groups were examined: 2 MGs, 2 ECGs and 1 CG. While one MG and one ECG were given positive suggestions concerning the effect of meditation on attention, the other two groups were given negative suggestions. MGs practised a focused attention meditation technique; ECGs were told that they were practising meditation but were given instructions for a sham meditation. CG participants sat in silence with their eyes closed. Interference control (Stroop task), selective sustained attention (d2 task), figural and verbal fluency measures of executive functions were assessed. Results indicate that suggestions have a substantial impact on interference control and verbal fluency, with positive suggestions leading to an increase in performance, whereas negative suggestions impeded improvement. This proof of concept study demonstrates the importance of the implementation of a credible ECG to elucidate context effects in meditation processes. It also indicates that suggestions can modulate the small effect of meditation on verbal fluency.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.