Oct 20, 2021 06:43 PM
Unfreezing the ice age: the truth about humanity’s deep past
https://www.theguardian.com/news/2021/oc...-deep-past
EXCERPT: Many of us probably still have something resembling this picture of human origins in our mind. More recent research, though, has shown it couldn’t possibly be accurate. In fact, biological anthropologists and geneticists are now converging on an entirely different picture. For most of our evolutionary history, we did indeed live in Africa – but not just the eastern savannas, as previously thought. Instead, our biological ancestors were distributed everywhere from Morocco to the Cape of Good Hope. Some of those populations remained isolated from one another for tens or even hundreds of thousands of years, cut off from their nearest relatives by deserts and rainforests. Strong regional traits developed, so that early human populations appear to have been far more physically diverse than modern humans. If we could travel back in time, this remote past would probably strike us as something more akin to a world inhabited by hobbits, giants and elves than anything we have direct experience of today, or in the more recent past.
Ancestral humans were not only quite different from one another; they also coexisted with smaller-brained, more ape-like species such as Homo naledi. What were these ancestral societies like? At this point, at least, we should be honest and admit that, for the most part, we don’t have the slightest idea. There’s only so much you can reconstruct from cranial remains and the occasional piece of knapped flint – which is basically all we have.
What we do know is that we are composite products of this original mosaic of human populations, which interacted with one another, interbred, drifted apart and came together mostly in ways we can only still guess at. It seems reasonable to assume that behaviours like mating and child-rearing practices, the presence or absence of dominance hierarchies or forms of language and proto-language must have varied at least as much as physical types, and probably far more.
Perhaps the only thing we can say with real certainty is that modern humans first appeared in Africa. When they began expanding out of Africa into Eurasia, they encountered other populations such as Neanderthals and Denisovans – less different, but still different – and these various groups interbred. Only after those other populations became extinct can we really begin talking about a single, human “us” inhabiting the planet. What all this brings home is just how radically different the social and physical world of our remote ancestors would have seemed to us – and this would have been true at least down to about 40,000BC. In other words, there is no “original” form of human society. Searching for one can only be a matter of myth-making... (MORE)
Researchers identify brain circuitry in rodents that may be responsible for negative emotional aspects of pain
https://www.drugabuse.gov/news-events/ne...ts-of-pain
RELEASE: A new study published today in Nature Neuroscience has uncovered neuronal circuitry in the brain of rodents that may play an important role in mediating pain-induced anhedonia -- a decrease in motivation to perform reward-driven behaviors. In the study funded by the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health, researchers were able to change the activity of this circuit and restore levels of motivation in a pre-clinical model of pain tested in rodents.
On a basic level, pain includes two components -- sensory (the pain you feel) and affective (the negative emotional component of pain). The presence of anhedonia, a hallmark of affective pain, is a common feature of depression, and may also increase one's vulnerability to opioid use disorder (OUD). Given this relationship, better understanding the brain circuitry involved in the affective component of pain is an important part of NIDA's research portfolio.
"Chronic pain is experienced on many levels beyond just the physical, and this research demonstrates the biological basis of affective pain. It is a powerful reminder that psychological phenomena such as affective pain are the result of biological processes," said NIDA Director, Nora D. Volkow, M.D. "It is exciting to see the beginnings of a path forward that may pave the way for treatment interventions that address the motivational and emotional effects of pain."
To investigate what might be underlying the affective component of pain, researchers at Washington University in St. Louis built upon prior studies where researchers observed that rats in pain were more likely to consume higher doses of heroin than the rats that were not in pain. In addition, their motivation for natural rewards, such as sugar tablets, was decreased. The new line of investigation sought to uncover the brain circuitry involved in this pathway, to better understand the relationship between pain and related changes in one's motivational state.
In this new study, the researchers measured the activity of dopamine neurons in the ventral tegmental area, part of the brain's "reward system," which process rewards and orchestrate motivated behavior. Dopamine neuronal activity was measured in rats while they pressed a lever with their front paw to receive a sugar tablet (the reward). To assess the impact of pain on the animals' behavior and activity of these dopamine neurons, either saline (the control condition) or a solution that produces a local inflammation (the pain condition) was injected into the hind paw.
After 48 hours, the researchers found that rats in the pain condition pressed the lever less to obtain the sugar tablet, demonstrating a decrease in motivation, and that their dopamine neurons were less active. They then discovered that the reason the dopamine neurons were less active was because pain was activating cells from a region of the brain known as the rostromedial tegmental nucleus (RMTg), which makes the inhibitory neurochemical GABA, and GABA blocks the activity of the dopamine neurons.
However, when the researchers artificially restored the activity of dopamine neurons (through a process called chemogenetics), they were able to reverse the negative effect of pain on the reward system and reinstate the motivation to push the lever for the sugar tablet among the rats in pain, even with the painful stimuli still present.
In additional experiments, the researchers were also able to restore the activity of the dopamine neurons by reversing the pain-induced hyperactivity of the GABA neurons. Doing so restored the motivation of rats that were experiencing pain to prefer a sweet solution of sucrose over water, indicating an improvement in their ability to feel pleasure, despite being in pain.
To the authors' knowledge, this is the first time it has been reported that pain promotes increased activity of GABA neurons and an "inhibitory pathway" in the reward system of the brain from the RMTg, which causes decreased activity of dopamine cells.
"Pain has primarily been studied at peripheral sites and not in the brain, with a goal of reducing or eliminating the sensory component of pain. Meanwhile, the emotional component of pain and associated comorbidities such as depression, anxiety, and lack of ability to feel pleasure that accompany pain has been largely ignored," said study author Jose Morón-Concepcion, Ph.D., of Washington University in St. Louis.
"It is fulfilling to be able to show pain patients that their mental health and behavioral changes are as real as the physical sensations, and we may be able to treat these changes someday," added study author Meaghan Creed, Ph.D., of Washington University in St. Louis.
https://www.theguardian.com/news/2021/oc...-deep-past
EXCERPT: Many of us probably still have something resembling this picture of human origins in our mind. More recent research, though, has shown it couldn’t possibly be accurate. In fact, biological anthropologists and geneticists are now converging on an entirely different picture. For most of our evolutionary history, we did indeed live in Africa – but not just the eastern savannas, as previously thought. Instead, our biological ancestors were distributed everywhere from Morocco to the Cape of Good Hope. Some of those populations remained isolated from one another for tens or even hundreds of thousands of years, cut off from their nearest relatives by deserts and rainforests. Strong regional traits developed, so that early human populations appear to have been far more physically diverse than modern humans. If we could travel back in time, this remote past would probably strike us as something more akin to a world inhabited by hobbits, giants and elves than anything we have direct experience of today, or in the more recent past.
Ancestral humans were not only quite different from one another; they also coexisted with smaller-brained, more ape-like species such as Homo naledi. What were these ancestral societies like? At this point, at least, we should be honest and admit that, for the most part, we don’t have the slightest idea. There’s only so much you can reconstruct from cranial remains and the occasional piece of knapped flint – which is basically all we have.
What we do know is that we are composite products of this original mosaic of human populations, which interacted with one another, interbred, drifted apart and came together mostly in ways we can only still guess at. It seems reasonable to assume that behaviours like mating and child-rearing practices, the presence or absence of dominance hierarchies or forms of language and proto-language must have varied at least as much as physical types, and probably far more.
Perhaps the only thing we can say with real certainty is that modern humans first appeared in Africa. When they began expanding out of Africa into Eurasia, they encountered other populations such as Neanderthals and Denisovans – less different, but still different – and these various groups interbred. Only after those other populations became extinct can we really begin talking about a single, human “us” inhabiting the planet. What all this brings home is just how radically different the social and physical world of our remote ancestors would have seemed to us – and this would have been true at least down to about 40,000BC. In other words, there is no “original” form of human society. Searching for one can only be a matter of myth-making... (MORE)
Researchers identify brain circuitry in rodents that may be responsible for negative emotional aspects of pain
https://www.drugabuse.gov/news-events/ne...ts-of-pain
RELEASE: A new study published today in Nature Neuroscience has uncovered neuronal circuitry in the brain of rodents that may play an important role in mediating pain-induced anhedonia -- a decrease in motivation to perform reward-driven behaviors. In the study funded by the National Institute on Drug Abuse (NIDA), part of the National Institutes of Health, researchers were able to change the activity of this circuit and restore levels of motivation in a pre-clinical model of pain tested in rodents.
On a basic level, pain includes two components -- sensory (the pain you feel) and affective (the negative emotional component of pain). The presence of anhedonia, a hallmark of affective pain, is a common feature of depression, and may also increase one's vulnerability to opioid use disorder (OUD). Given this relationship, better understanding the brain circuitry involved in the affective component of pain is an important part of NIDA's research portfolio.
"Chronic pain is experienced on many levels beyond just the physical, and this research demonstrates the biological basis of affective pain. It is a powerful reminder that psychological phenomena such as affective pain are the result of biological processes," said NIDA Director, Nora D. Volkow, M.D. "It is exciting to see the beginnings of a path forward that may pave the way for treatment interventions that address the motivational and emotional effects of pain."
To investigate what might be underlying the affective component of pain, researchers at Washington University in St. Louis built upon prior studies where researchers observed that rats in pain were more likely to consume higher doses of heroin than the rats that were not in pain. In addition, their motivation for natural rewards, such as sugar tablets, was decreased. The new line of investigation sought to uncover the brain circuitry involved in this pathway, to better understand the relationship between pain and related changes in one's motivational state.
In this new study, the researchers measured the activity of dopamine neurons in the ventral tegmental area, part of the brain's "reward system," which process rewards and orchestrate motivated behavior. Dopamine neuronal activity was measured in rats while they pressed a lever with their front paw to receive a sugar tablet (the reward). To assess the impact of pain on the animals' behavior and activity of these dopamine neurons, either saline (the control condition) or a solution that produces a local inflammation (the pain condition) was injected into the hind paw.
After 48 hours, the researchers found that rats in the pain condition pressed the lever less to obtain the sugar tablet, demonstrating a decrease in motivation, and that their dopamine neurons were less active. They then discovered that the reason the dopamine neurons were less active was because pain was activating cells from a region of the brain known as the rostromedial tegmental nucleus (RMTg), which makes the inhibitory neurochemical GABA, and GABA blocks the activity of the dopamine neurons.
However, when the researchers artificially restored the activity of dopamine neurons (through a process called chemogenetics), they were able to reverse the negative effect of pain on the reward system and reinstate the motivation to push the lever for the sugar tablet among the rats in pain, even with the painful stimuli still present.
In additional experiments, the researchers were also able to restore the activity of the dopamine neurons by reversing the pain-induced hyperactivity of the GABA neurons. Doing so restored the motivation of rats that were experiencing pain to prefer a sweet solution of sucrose over water, indicating an improvement in their ability to feel pleasure, despite being in pain.
To the authors' knowledge, this is the first time it has been reported that pain promotes increased activity of GABA neurons and an "inhibitory pathway" in the reward system of the brain from the RMTg, which causes decreased activity of dopamine cells.
"Pain has primarily been studied at peripheral sites and not in the brain, with a goal of reducing or eliminating the sensory component of pain. Meanwhile, the emotional component of pain and associated comorbidities such as depression, anxiety, and lack of ability to feel pleasure that accompany pain has been largely ignored," said study author Jose Morón-Concepcion, Ph.D., of Washington University in St. Louis.
"It is fulfilling to be able to show pain patients that their mental health and behavioral changes are as real as the physical sensations, and we may be able to treat these changes someday," added study author Meaghan Creed, Ph.D., of Washington University in St. Louis.