What are the effects of yoga and meditation on the brain? (Asked by @leximills)
Yoga and meditation have effects on physiology, brain chemistry, and cognitive processes; these vary depending on the exact type of practise being performed and how long a person has practised it for. Studies of brain activity confirm that meditation can achieve a state of calm, thoughtless awareness, by suppressing brain regions involved in external attention and irrelevant information, and activating brain regions involved in internalised attention and positive emotions. Meditation is thought to activate the parasympathetic-limbic pathways, reducing heart rate, lowering blood pressure and slowing breathing. Meditation practises can fundamentally change the shape, structure and function of the brain – reinforcing neural networks, developing particular brain regions and influencing the production of key neurotransmitters and hormones in the brain related to attention, self-awareness and emotional control. Yoga has far-reaching effects on the body, reducing inflammation, boosting mood and making long-term practitioners feel more awake. It may even speed up learning in childhood and slow the natural cognitive declines that come with ageing. However, our understanding of the effects of meditative practises on the brain and body is still in its infancy – much more work remains (especially large-scale, carefully controlled trials).
Brains rather than braun may have guided our ancestors out of Africa, but new research suggests primates’ big brains are no longer the assets they once were.
A study published in the journal Evolution reports that larger brains are directly related to an increased risk of extinction in modern primates. Researchers led by Alejandro Gonzalez-Voyer at Doñana Biological Station in Spain, compared published data on 474 species of mammal, with their IUCN Redlist categorisations, to find out how different biological traits influence extinction risk. The team found that larger brains tend to be associated with a longer gestation period, longer weaning period and smaller litter sizes, all of which indirectly increase extinction risk.
What can this squiggling, toothed eel-like creature possible tell us about our own brains? Well, the lamprey, although ugly, occupies a pivotal place in the evolutionary tree. Research on captive lampreys can tell us about the earliest evolution of the vertebrate brain and yield insights that may help to cure and treat neurological disease. A new study published in Nature last month suggests that the human pattern of development in an important region of our brains may have evolved much earlier than we thought, in a creature that looks much like a modern-day lamprey. So perhaps lampreys can tell us more about our brains than you might have thought!
When you think crayfish, you probably think of food rather than groundbreaking medical research, but a paper published last month in Developmental Cell reports an incredible neurological feature of the humble lobster. Stem cells, blueprint cells that produce new cells, are vital for repairing wear-and-tear. Research from the US revealed a remarkable talent in Crayfish – they can grow new brain stem cells from their blood.
We like to think that our more complex emotions are uniquely human, although researchers continually thwarting that belief with science. This week, another of our emotions came under threat – regret. Nobody has ever demonstrated regret in another non-human animal. Until now. A study released this month in Nature claims to have found evidence that rats are capable of feeling regret, a complex emotion distinct from mere disappointment.
Disappointment is when we recognise that we didn’t get as much as we expected, whereas to regret is to recognise that our actions are the reason behind this – that an alternative action, a different decision, would have produced a better outcome. In this study, researchers forced rats to choose between waiting for a particular reward, or moving onto the next reward that may come with an even longer wait. This is exactly the type of situation we might expect rats to feel regretful about, but are they smart enough to feel such a complex emotion?
One of the most distinctive characteristics of Homo sapiens is our exceptionally large brain, and enhanced cognitive capabilities. In fact, large brains, measured by the encephalisation quotient (EQ), are a characteristic of primates in general, and brain size and complexity has been increasing in the primate lineage for nearly 70 million years. However, this trend is particularly noticeable in the human lineage, and the last 3 million years of hominid evolution have seen the most pronounced increases in encephalisation, with a tripling in brain size. Such a rapid increase in size is extraordinary, especially for an organ so complex. Some areas of the brain have expanded disproportionately, such as the cerebral cortex, which has increased in size by 3 orders of magnitude since our divergence from Chimpanzees. The cerebral cortex accounts for around 85% of total brain volume in humans, and is responsible for complex mental functions.
The earliest known hominid was Sahelanthropus tchadensis, represented only by relatively few fossilised skull fragments, he is so ancient it isn’t clear whether he could truly be considered human at all. Fossils found in Chad, dated to around 7 million years old, may have belonged to a direct human ancestor, or more likely to a neighbouring branch of the ape family tree. This uncertainty is common until around 4 million years ago; many species are known only by partial skeletons and the relationships between them are often unclear. The Australopithecines may be the first group of hominids that we can be said to understand to any extent.
Understanding the evolution of Homo sapiens, and how humans came to be human, has been a fascination for people since Darwin’s time, but it has also proved to be one of the most controversial of the sciences. Humans and Chimpanzees diverged about 7 million years ago and during this time a great deal of anatomical and behavioural changes occurred which now distinguish us from our closest relatives. Despite this, we still share over 99% of our genetic make-up with Chimpanzees; only 1% of our genes truly make us human. What is the manifestation of this 1%? Some of these differences are very clear visually; we are taller and less hairy, with larger brains and an upright, two-legged stance. Other differences are slightly more subtle; we have language, we use tools, we have culture and art enabled by abstract thought, we have a concept of self… but as that list continues, it becomes increasingly difficult to determine whether Chimpanzees, or indeed other animals, also share these qualities. If Chimpanzees can be taught language, then this indicates they have a brain capable of understanding and learning language, and thus, surely they can in some sense be said to have language themselves? Other characteristics are even more difficult to pin down; how do you measure self-awareness? Although there is a long list of traits that most people would consider to be exclusively human, the situation is in fact far less clear cut than that.
Mind reading no longer exclusively belongs to the domain of science fiction writers and mediums. Over the last 50 years, researchers around the world have been working on a system known as the brain-computer interface (BCI) which allows direct communication between the brain and an external device such a computer or a robotic limb. The main goal of this research is to develop technology capable of restoring sensory function to the blind or deaf, and restoring movement to patients suffering from paralysis. Major strides have been made in this endeavour over the last decade, and BCI technology is now even being adapted to commercial purposes such as gaming.
BCI technology is possible because of the way in which the brain transmits messages within itself and to other areas of the body. The brain is composed of around 100 billion cells called neurons. Messages are sent from neuron to neuron as an electrical impulse, created by ion imbalances in neuronal membranes. Neurons are insulated by a coating known as the myelin sheath, which prevents most, but not all, of these electrical impulses from escaping. The tiny portion of the electricity which escapes from the myelin sheath can be detected and this signal can be interpreted by computers. A second feature of the brain is also key to the success of BCI: neural plasticity – the ability of the brain to adapt to new situations. Patients suffering with brain damage illustrate neural plasticity; in many cases patients are able to, over time, adapt other areas of their brain to perform the tasks of damaged regions. Neural plasticity also enables the brain to adapt to interpret new input, such as that provided by the brain-computer interface.
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