Why does the brain remember dreams?

The reason for dreaming is still a mystery for the researchers who study the difference between “high dream recallers,” who recall dreams regularly, and “low dream recallers,” who recall dreams rarely. In January 2013 (work published in the journal Cerebral Cortex), the team led by Perrine Ruby, Inserm researcher at the Lyon Neuroscience Research Center, made the following two observations: “high dream recallers” have twice as many time of wakefulness during sleep as “low dream recallers” and their brains are more reactive to auditory stimuli during sleep and wakefulness. This increased brain reactivity may promote awakenings during the night, and may thus facilitate memorization of dreams during brief periods of wakefulness.In this new study, the research team sought to identify which areas of the brain differentiate high and low dream recallers. They used Positron Emission Tomography (PET) to measure the spontaneous brain activity of 41 volunteers during wakefulness and sleep. The volunteers were classified into 2 groups: 21 “high dream recallers” who recalled dreams 5.2 mornings per week in average, and 20 “low dream recallers,” who reported 2 dreams per month in average. High dream recallers, both while awake and while asleep, showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC) and in the temporo-parietal junction (TPJ), an area of the brain involved in attention orienting toward external stimuli.”This may explain why high dream recallers are more reactive to environmental stimuli, awaken more during sleep, and thus better encode dreams in memory than low dream recallers. Indeed the sleeping brain is not capable of memorizing new information; it needs to awaken to be able to do that,” explains Perrine Ruby, Inserm Research Fellow.The South African neuropsychologist Mark Solms had observed in earlier studies that lesions in these two brain areas led to a cessation of dream recall. The originality of the French team’s results is to show brain activity differences between high and low dream recallers during sleep and also during wakefulness.”Our results suggest that high and low dream recallers differ in dream memorization, but do not exclude that they also differ in dream production. Indeed, it is possible that high dream recallers produce a larger amount of dreaming than low dream recallers” concludes the research team.Story Source:The above story is based on materials provided by INSERM (Institut national de la sant et de la recherche mdicale). Note: Materials may be edited for content and length.

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Mechanism elucidated: How smell perception influences food intake

In animals, as in humans, hunger mechanisms are known to stimulate food intake. Hunger triggers a set of mechanisms that encourage feeding, for example by increasing sensory perceptions such as the sense of smell. The researchers have now succeeded in revealing what links hunger and increased smell perception in the brain, and the resulting urge to eat.The researchers have discovered how this mechanism is initiated in the endocannabinoid system in mice. This system interconnects receptors located in the brain and involved in different sensations such as euphoria, anxiety, or even pain, that are also sensitive to cannabinoid substances, such as cannabis.The researchers discovered that the CB1 cannabinoid receptors control a circuit that connects the olfactory bulb (the region in the nervous system that initially handles olfactory information, located above the nose) to the olfactory cortex (higher structures of the brain). When the sensation of hunger is felt, it triggers the activity of the cannabinoid receptors, which in turn activate the olfactory circuit, which then becomes more responsive.It is therefore this biological mechanism that brings about the increased sensitivity to smell during hunger, explaining one of the reasons for food intake and attraction to food.The researchers expect that the circuit involved in the olfactory system is altered in obese or anorexic patients, and that sensitivity to smell may be more or less strong compared to normal. Elucidation of the biological mechanism will allow better management of these types of pathologies.Story Source:The above story is based on materials provided by INSERM (Institut national de la sant et de la recherche mdicale). Note: Materials may be edited for content and length.

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Mother’s level of education has impact on depression in her children

May 31, 2013 — Children of women who did not finish high school were twice as likely to experience a major episode of depression in early adulthood as children whose mothers obtained a high school diploma, according to a new study by researchers at McGill University.”Our research indicates that a mother’s lack of high school education has a robust impact on her child’s risk of major depressive episode in early adulthood,” said Amélie Quesnel-Vallée, senior author of the study. Indeed, the increased risk of depression among children of mothers with less than a high school education could not be attributed to parental history of depression, early life adversity or the children’s own education and income in early adulthood.This study is the first in Canada to distinguish the impact of mother’s and father’s education on depression in early adulthood. The study employed a sample of 1,267 participants from Statistics Canada’s National Population Health Survey. The respondents were first interviewed in 1994, when they were between 12 and 24 years old, and living with their parents. They were then followed for 12 years, and their risk of major depressive episode was assessed when they were between 22 and 36 years old.”Depression in early adulthood strikes at a critical time. An individual may be pursuing studies or apprenticeships, or starting a career or a family. A disruption caused by depression can potentially derail these events and have lifelong consequences,” says Quesnel-Vallée.Interestingly, the father’s level of education had no impact. “This, along with the fact that the effect of mother’s education was not explained by the children’s own education or income, suggests that mothers’ parenting skills may be at play here,” according to Quesnel-Vallée.”Education gives people practical skills, such as communication, analytical and problem-solving skills, as well as an increased sense of mastery” says Alison Park, a researcher at the Institut National de Santé Publique du Québec who worked on this research in the course of her Master’s degree under Quesnel-Vallée’s supervision. “A better-educated mother might be more confident in coping with difficulties arising from child-rearing. This increased confidence and feeling of self-mastery might serve as a model for her children.”

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