Fruit fly research may reveal what happens in female brains during courtship and mating

What are the complex processes in the brain involved with choosing a mate, and are these processes different in females versus males? It’s difficult to study such questions in people, but researchers are finding clues in fruit flies that might be relevant to humans and other animals. Three different studies on the topic are being published in the Cell Press journals Neuron (1, 2) and Current Biology.

Work over the past 100 years has largely focused on the overt courtship behaviors that male flies direct toward females. However, the female ultimately decides whether to reject the male or copulate with him. How does the female make this decision? In one Neuron paper, researchers report that they have identified two small groups of neurons in the female brain that function to modulate whether she will mate or not with a male based on his distinct pheromones and courtship song. In this paper, a team led by Dr. Bruce Baker of the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Virginia also reports that these neurons are genetically distinct from the previously identified neurons that function to drive the elaborate courtship ritual with which a male woos a female. “An understanding of the neural mechanisms underlying how sensory information elicits appropriate sexual behaviors can be used as a point of comparison for how similar sexual behavior circuits are structured and function in other species,” says Dr. Baker.

In the Current Biology study, Dr. Leslie Vosshall of The Rockefeller University in New York City and her team found that a small group of neurons in the abdominal nerve cord and reproductive tract—called Abdominal-B neurons—is necessary for the female to pause her movement and interact with a courting male. When the neurons are inactivated, the female ignores the male and keeps moving, but when the neurons are activated, the female spontaneously pauses. “Sexual courtship is a duet—the male and female send signals back and forth until they reach the point that copulation proceeds,” says Dr. Jennifer Bussell, the lead author of the study. “Pausing to interact with a male, rather than avoiding him, is a crucial step in any female’s behavior leading to copulation. Tying a group of neurons to this particular response to males will allow us to dissect in detail how female mating circuitry functions.”

In another Neuron paper, researchers studied the effects of a small protein called sex peptide that is transferred along with sperm from males to females and is detected by sensory neurons in the uterus. Sex peptide changes the female’s behavior so that she is reluctant to mate again for about10 days. The investigators traced the neuronal pathway that is modulated when the uterus’s sensory neurons detect sex peptide. “Thanks to our work, we think the sex peptide signal goes to a region of the fly’s brain that is the homolog of the hypothalamus, which has been know for many years to be central in controlling sexual receptivity in vertebrates,” explains co-lead author Dr. Mark Palfreyman of the Research Institute of Molecular Pathology in Vienna, Austria. This region of the brain links the nervous system to the endocrine, or hormonal, system. “Of course, these models will still need to be tested and our work only provides an initial glimpse, but our study opens the possibility that analogous neuroendocrine systems control sexual receptivity from flies to vertebrates,” adds senior author Dr. Barry Dickson, who was also a co-author on the Current Biology paper published by Dr. Vosshall.

Only 25 Minutes of Mindfulness Meditation Alleviates Stress

Mindfulness meditation has become an increasingly popular way for people to improve their mental and physical health, yet most research supporting its benefits has focused on lengthy, weeks-long training programs.

New research from Carnegie Mellon University is the first to show that brief mindfulness meditation practice — 25 minutes for three consecutive days — alleviates psychological stress. Published in the journal “Psychoneuroendocrinology,” the study investigates how mindfulness meditation affects people’s ability to be resilient under stress.

"More and more people report using meditation practices for stress reduction, but we know very little about how much you need to do for stress reduction and health benefits," said lead author J. David Creswell, associate professor of psychology in the Dietrich College of Humanities and Social Sciences.

For the study, Creswell and his research team had 66 healthy individuals aged 18-30 years old participate in a three-day experiment. Some participants went through a brief mindfulness meditation training program; for 25 minutes for three consecutive days, the individuals were given breathing exercises to help them monitor their breath and pay attention to their present moment experiences. A second group of participants completed a matched three-day cognitive training program in which they were asked to critically analyze poetry in an effort to enhance problem-solving skills.

Following the final training activity, all participants were asked to complete stressful speech and math tasks in front of stern-faced evaluators. Each individual reported their stress levels in response to stressful speech and math performance stress tasks, and provided saliva samples for measurement of cortisol, commonly referred to as the stress hormone.

The participants who received the brief mindfulness meditation training reported reduced stress perceptions to the speech and math tasks, indicating that the mindfulness meditation fostered psychological stress resilience. More interestingly, on the biological side, the mindfulness meditation participants showed greater cortisol reactivity.

"When you initially learn mindfulness mediation practices, you have to cognitively work at it — especially during a stressful task," said Creswell. "And, these active cognitive efforts may result in the task feeling less stressful, but they may also have physiological costs with higher cortisol production."

Creswell’s group is now testing the possibility that mindfulness can become more automatic and easy to use with long-term mindfulness meditation training, which may result in reduced cortisol reactivity.

New study discovers biological basis for magic mushroom ‘mind expansion’

Psychedelic drugs such as LSD and magic mushrooms can profoundly alter the way we experience the world but little is known about what physically happens in the brain. New research, published in Human Brain Mapping, has examined the brain effects of the psychedelic chemical in magic mushrooms, called psilocybin, using data from brain scans of volunteers who had been injected with the drug.

The study found that under psilocybin, activity in the more primitive brain network linked to emotional thinking became more pronounced, with several different areas in this network - such as the hippocampus and anterior cingulate cortex - active at the same time. This pattern of activity is similar to the pattern observed in people who are dreaming. Conversely, volunteers who had taken psilocybin had more disjointed and uncoordinated activity in the brain network that is linked to high-level thinking, including self-consciousness.

Psychedelic drugs are unique among other psychoactive chemicals in that users often describe ‘expanded consciousness,’ including enhanced associations, vivid imagination and dream-like states. To explore the biological basis for this experience, researchers analysed brain imaging data from 15 volunteers who were given psilocybin intravenously while they lay in a functional magnetic resonance imaging (fMRI) scanner. Volunteers were scanned under the influence of psilocybin and when they had been injected with a placebo.

“What we have done in this research is begin to identify the biological basis of the reported mind expansion associated with psychedelic drugs,” said Dr Robin Carhart-Harris from the Department of Medicine, Imperial College London.  “I was fascinated to see similarities between the pattern of brain activity in a psychedelic state and the pattern of brain activity during dream sleep, especially as both involve the primitive areas of the brain linked to emotions and memory. People often describe taking psilocybin as producing a dream-like state and our findings have, for the first time, provided a physical representation for the experience in the brain.”    

The new study examined variation in the amplitude of fluctuations in what is called the blood-oxygen level dependent (BOLD) signal, which tracks activity levels in the brain. This revealed that activity in important brain networks linked to high-level thinking in humans becomes unsynchronised and disorganised under psilocybin. One particular network that was especially affected plays a central role in the brain, essentially ‘holding it all together’, and is linked to our sense of self.

In comparison, activity in the different areas of a more primitive brain network became more synchronised under the drug, indicating they were working in a more co-ordinated, ‘louder’ fashion. The network involves areas of the hippocampus, associated with memory and emotion, and the anterior cingulate cortex which is related to states of arousal.

Lead author Dr Enzo Tagliazucchi from Goethe University, Germany said: “A good way to understand how the brain works is to perturb the system in a marked and novel way. Psychedelic drugs do precisely this and so are powerful tools for exploring what happens in the brain when consciousness is profoundly altered. It is the first time we have used these methods to look at brain imaging data and it has given some fascinating insight into how psychedelic drugs expand the mind. It really provides a window through which to study the doors of perception.”

Dr. Carhart-Harris added: “Learning about the mechanisms that underlie what happens under the influence of psychedelic drugs can also help to understand their possible uses. We are currently studying the effect of LSD on creative thinking and we will also be looking at the possibility that psilocybin may help alleviate symptoms of depression by allowing patients to change their rigidly pessimistic patterns of thinking. Psychedelics were used for therapeutic purposes in the 1950s and 1960s but now we are finally beginning to understand their action in the brain and how this can inform how to put them to good use.”

The data was originally collected at Imperial College London in 2012 by a research group led by Dr Carhart-Harris and Professor David Nutt from the Department of Medicine, Imperial College London. Initial results revealed a variety of changes in the brain associated with drug intake. To explore the data further Dr. Carhart-Harris recruited specialists in the mathematical modelling of brain networks, Professor Dante Chialvo and Dr Enzo Tagliazucchi to investigate how psilocybin alters brain activity to produce its unusual psychological effects.

As part of the new study, the researchers applied a measure called entropy. This was originally developed by physicists to quantify lost energy in mechanical systems, such as a steam engine, but entropy can also be used to measure the range or randomness of a system. For the first time, researchers computed the level of entropy for different networks in the brain during the psychedelic state. This revealed a remarkable increase in entropy in the more primitive network, indicating there was an increased number of patterns of activity that were possible under the influence of psilocybin. It seemed the volunteers had a much larger range of potential brain states that were available to them, which may be the biophysical counterpart of ‘mind expansion’ reported by users of psychedelic drugs.

Previous research has suggested that there may be an optimal number of dynamic networks active in the brain, neither too many nor too few. This may provide evolutionary advantages in terms of optimising the balance between the stability and flexibility of consciousness. The mind works best at a critical point when there is a balance between order and disorder and the brain maintains this optimal number of networks. However, when the number goes above this point, the mind tips into a more chaotic regime where there are more networks available than normal. Collectively, the present results suggest that psilocybin can manipulate this critical operating point.

Insect diet helped early humans build bigger brains

Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors of humans and other primates, suggests research from Washington University in St. Louis.

“Challenges associated with finding food have long been recognized as important in shaping evolution of the brain and cognition in primates, including humans,” said Amanda D. Melin, PhD, assistant professor of anthropology in Arts & Sciences and lead author of the study.

“Our work suggests that digging for insects when food was scarce may have contributed to hominid cognitive evolution and set the stage for advanced tool use.”

Based on a five-year study of capuchin monkeys in Costa Rica, the research provides support for an evolutionary theory that links the development of sensorimotor (SMI) skills, such as increased manual dexterity, tool use, and innovative problem solving, to the creative challenges of foraging for insects and other foods that are buried, embedded or otherwise hard to procure.

Published in the June 2014 Journal of Human Evolution, the study is the first to provide detailed evidence from the field on how seasonal changes in food supplies influence the foraging patterns of wild capuchin monkeys.

The study is co-authored by biologist Hilary C. Young and anthropologists Krisztina N. Mosdossy and Linda M. Fedigan, all from the University of Calgary, Canada.

It notes that many human populations also eat embedded insects on a seasonal basis and suggests that this practice played a key role in human evolution.

“We find that capuchin monkeys eat embedded insects year-round but intensify their feeding seasonally, during the time that their preferred food – ripe fruit – is less abundant,” Melin said. “These results suggest embedded insects are an important fallback food.”

Previous research has shown that fallback foods help shape the evolution of primate body forms, including the development of strong jaws, thick teeth and specialized digestive systems in primates whose fallback diets rely mainly on vegetation.

This study suggests that fallback foods can also play an important role in shaping brain evolution among primates that fall back on insect-based diets, and that this influence is most pronounced among primates that evolve in habitats with wide seasonal variations, such as the wet-dry cycles found in some South American forests.

“Capuchin monkeys are excellent models for examining evolution of brain size and intelligence for their small body size, they have impressively large brains,” Melin said. “Accessing hidden and well-protected insects living in tree branches and under bark is a cognitively demanding task, but provides a high-quality reward: fat and protein, which is needed to fuel big brains.”

But when it comes to using tools, not all capuchin monkey strains and lineages are created equal, and Melin’s theories may explain why.

Perhaps the most notable difference between the robust (tufted, genus Sapajus) and gracile (untufted, genus Cebus) capuchin lineages is their variation in tool use. While Cebus monkeys are known for clever food-foraging tricks, such as banging snails or fruits against branches, they can’t hold a stick to their Sapajus cousins when it comes to the
innovative use and modification of sophisticated tools.

One explanation, Melin said, is that Cebus capuchins have historically and consistently occupied tropical rainforests, whereas the Sapajus lineage spread from their origins in the Atlantic rainforest into drier, more temperate and seasonal habitat types.

“Primates who extract foods in the most seasonal environments are expected to experience the strongest selection in the ‘sensorimotor intelligence’ domain, which includes cognition related to object handling,” Melin said. “This may explain the occurrence of tool use in some capuchin lineages, but not in others.”

Genetic analysis of mitochondial chromosomes suggests that the Sapajus-Cebus diversification occurred millions of years ago in the late Miocene epoch.

“We predict that the last common ancestor of Cebus and Sapajus had a level of SMI more closely resembling extant Cebus monkeys, and that further expansion of SMI evolved in the robust lineage to facilitate increased access to varied embedded fallback foods,
necessitated by more intense periods of fruit shortage,” she said.

One of the more compelling modern examples of this behavior, said Melin, is the seasonal consumption of termites by chimpanzees, whose use of tools to extract this protein-rich food source is an important survival technique in harsh environments.

What does this all mean for hominids?

While it’s hard to decipher the extent of seasonal dietary variations from the fossil record, stable isotope analyses indicate seasonal variation in diet for at least one South African hominin, Paranthropus robustus. Other isotopic research suggests that early human diets may have included a range of extractable foods, such as termites, plant roots and tubers.

Modern humans frequently consume insects, which are seasonally important when other animal foods are limited.

This study suggests that the ingenuity required to survive on a diet of elusive insects has been a key factor in the development of uniquely human skills:

It may well have been bugs that helped build our brains.

Addiction starts with an overcorrection in the brain

The National Institutes of Health has turned to neuroscientists at the nation’s most “Stone Cold Sober” university for help finding ways to treat drug and alcohol addiction.

Brigham Young University professor Scott Steffensen and his collaborators have published three new scientific papers that detail the brain mechanisms involved with addictive substances. And the NIH thinks Steffensen’s on the right track, as evidenced by a $2-million grant that will help fund projects in his BYU lab for the next five years.

“Addiction is a brain disease that could be treated like any other disease,” Steffensen said. “I wouldn’t be as motivated to do this research, or as passionate about the work, if I didn’t think a cure was possible.” 

Steffensen’s research suggests that the process of a brain becoming addicted is similar to a driver overcorrecting a vehicle. When drugs and alcohol release unnaturally high levels of dopamine in the brain’s pleasure system, oxidative stress occurs in the brain.

Steffensen and his collaborators have found that the brain responds by generating a protein called BDNF (brain derived neurotrophic factor). This correction suppresses the brain’s normal production of dopamine long after someone comes down from a high. Not having enough dopamine is what causes the pains, distress and anxiety of withdrawal.

“The body attempts to compensate for unnatural levels of dopamine, but a pathological process occurs,” Steffensen said. “We think it all centers around a subset of neurons that ordinarily put the brakes on dopamine release.”

A group of undergraduate students work in Steffensen’s lab along with post-doctoral fellows and graduate students. Jennifer Blanchard Mabey, a graduate student in neuroscience, co-authored a paper about withdrawal that is in the current issue of The Journal of Neuroscience.

“It’s rewarding to see that your research efforts place another small piece in the enormous addiction puzzle,” said Mabey.

A separate study, co-authored by Steffensen and Ph.D. candidates Nathan Schilaty and David Hedges, explains how nicotine and alcohol interact in the brain.

“Addiction is a huge concern in our society and is very misunderstood,” Schilaty said. “Our research is helping us to formulate ideas on how we can better help these individuals through non-invasive and non-pharmacological means.”

Eun Young Jang, a post-doctoral fellow in Steffensen’s lab, authored a third paper for Addiction Biology describing the effects of cocaine addiction on the brain’s reward circuitry.

In these three research papers, dopamine is the common thread.

“I am optimistic that in the near future medical science will be able to reverse the brain changes in dopamine transmission that occur with drug dependence and return an ‘addict’ to a relatively normal state,” Steffensen said. “Then the addict will be in a better position to make rational decisions regarding their behavior and will be empowered to remain drug free.”