The Role of Serotonin in Fear Learning and Memory: A Systematic Review of Human Studies

Fear is characterized by distinct behavioral and physiological responses that are essential for the survival of the human species. Fear conditioning (FC) serves as a valuable model for studying the acquisition, extinction, and expression of fear. The serotonin (5-hydroxytryptamine, 5-HT) system is known to play a significant role in emotional and motivational aspects of human behavior, including fear learning and expression. Accumulating evidence from both animal and human studies suggests that brain regions involved in FC, such as the amygdala, hippocampus, and prefrontal cortex, possess a high density of 5-HT receptors, implicating the crucial involvement of serotonin in aversive learning. Additionally, studies exploring serotonin gene polymorphisms have indicated their potential influence on FC. Therefore, the objective of this work was to review the existing evidence linking 5-HT with fear learning and memory in humans. Through a comprehensive screening of the PubMed and Web of Science databases, 29 relevant studies were included in the final review. These studies investigated the relationship between serotonin and fear learning using drug manipulations or by studying 5-HT-related gene polymorphisms. The results suggest that elevated levels of 5-HT enhance aversive learning, indicating that the modulation of serotonin 5-HT2A receptors regulates the expression of fear responses in humans. Understanding the role of this neurochemical messenger in associative aversive learning can provide insights into psychiatric disorders such as anxiety and post-traumatic stress disorder (PTSD), among others

Oxygen isotope effect and phase separation in the optical conductivity of (La0.5_{0.5}Pr0.5_{0.5})0.7_{0.7}Ca0.3_{0.3}MnO3_3 thin films

The optical conductivities of films of (La$_{0.5}$Pr$_{0.5}$)$_{0.7}$Ca$_{0.3}$MnO$_3$ with different oxygen isotopes ($^{16}$O and $^{18}$O) have been determined in the spectral range from 0.3 to 4.3 eV using a combination of transmission in the mid-infrared and ellipsometry from the near-infrared to ultra-violet regions. We have found that the isotope exchange strongly affects the optical response in the ferromagnetic phase in a broad frequency range, in contrast to the almost isotope-independent optical conductivity above $T_C$. The substitution by $^{18}$O strongly suppresses the Drude response and a mid-infrared peak while enhancing the conductivity peak at 1.5 eV. A qualitative explanation can be given in terms of the phase separation present in these materials. Moreover, the optical response is similar to the one extracted from measurements in polished samples and other thin films, which signals to the importance of internal strain.Comment: 11 pages, 11 figures, to appear in PR

Idiopathic Perforation of the Sigmoid Colon in a 2.5 Years Old Girl: A Case Report

Idiopathic colon perforation is rare in children. It is more common at the extremes of age. Splenic flextures, ileocecal and lower sigmoid regions are the most common sites of perforation. Delay in proper management of this condition is associated with high mortality and morbidity rate. We report on the case of a 2.5 years old girl who presented with fever, diarrhea, nausea and vomiting and progressive abdominal distention.Finally, she underwent an exploratory laparotomy for suspected peritonitis because of the patient's worsening condition. An area of perforation was found in the sigmoid colon that segmental resection and an end double barrel colostomy was done

Principles of sensorimotor learning.

The exploits of Martina Navratilova and Roger Federer represent the pinnacle of motor learning. However, when considering the range and complexity of the processes that are involved in motor learning, even the mere mortals among us exhibit abilities that are impressive. We exercise these abilities when taking up new activities - whether it is snowboarding or ballroom dancing - but also engage in substantial motor learning on a daily basis as we adapt to changes in our environment, manipulate new objects and refine existing skills. Here we review recent research in human motor learning with an emphasis on the computational mechanisms that are involved

Comparing the physical properties of Pr/Gd and Pr/Ce substitutions in Ru(Gd 1.5 Ce 0.5 )Sr 2Cu 2O 10−δ

74.25.Ha Magnetic properties, 74.25.Fy Transport properties, 74.70.Pq Ruthenates,