Instant Expert: The Human Brain
Instant Expert: The Human Brain
- 11:58 04 September 2006
- NewScientist.com news service
- Helen Philips
The Human Brain - With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.
The brain is the most complex organ in the human body. It produces our every thought, action, memory, feeling and experience of the world. This jelly-like mass of tissue, weighing in at around 1.4 kilograms, contains a staggering one hundred billion nerve cells, or neurons.
The complexity of the connectivity between these cells is mind-boggling. Each neuron can make contact with thousands or even tens of thousands of others, via tiny structures called synapses. Our brains form a million new connections for every second of our lives. The pattern and strength of the connections is constantly changing and no two brains are alike.
While people often speak of their "grey matter", the brain also contains white matter. The grey matter is the cell bodies of the neurons, while the white matter is the branching network of thread-like tendrils - called dendrites and axons - that spread out from the cell bodies to connect to other neurons.
But the brain also has another, even more numerous type of cell, called glial cells. These outnumber neurons ten times over. Once thought to be support cells, they are now known to amplify neural signals and to be as important as neurons in mental calculations. There are many different types of neuron, only one of which is unique to humans and the other great apes, the so called spindle cells.
Brain structure is shaped partly by genes, but largely by experience. Only relatively recently it was discovered that new brain cells are being bornneurogenesis. The brain has bursts of growth and throughout our lives - a process called then periods of consolidation, when excess connections are pruned. The most notable bursts are in the first two or three years of life, during puberty, and also a final burst in young adulthood.
The neurons in our brains communicate in a variety of ways. Signals pass between them by the release and capture of neurotransmitter and neuromodulator chemicals, such as glutamate, dopamine, acetylcholine, noradrenalin, serotonin and endorphins.
Some neurochemicals work in the synapse, passing specific messages from release sites to collection sites, called receptors. Others also spread their influence more widely, like a radio signal, making whole brain regions more or less sensitive.
These neurochemicals are so important that deficiencies in them are linked to certain diseases. For example, a loss of dopamine in the basal ganglia, which control movements, leads to Parkinson’s disease. It can also increase susceptibility to addiction because it mediates our sensations of reward and pleasure.
Similarly, a deficiency in serotonin, used by regions involved in emotion, can be linked to depression or mood disorders, and the loss of acetylcholine in the cerebral cortex is characteristic of Alzheimer’s disease.
Within individual neurons, signals are formed by electrochemical pulses. Collectively, this electrical activity can be detected outside the scalp by an electroencephalogram (EEG).
These signals have wave-like patterns, which scientists classify from alpha (common while we are relaxing or sleeping), through to gamma (active thought). When this activity goes awry, it is called a seizure. Some researchers think that synchronising the activity in different brain regions is important in perception.
Other ways of imaging brain activity are indirect. Functional magnetic resonance imaging (fMRI) or positron emission tomography (PET) monitor blood flow. MRI scans, computed tomography (CT) scans and diffusion tensor images (DTI) use the magnetic signatures of different tissues, X-ray absorption, or the movement of water molecules in those tissues, to image the brain.
These scanning techniques have revealed which parts of the brain are associated with which functions. Examples include activity related to sensations, movement, libido, choices, regrets, motivations and even racism. However, some experts argue that we put too much trust in these results and that they raise privacy issues.
Before scanning techniques were common, researchers relied on patients with brain damage caused by strokes, head injuries or illnesses, to determine which brain areas are required for certain functions. This approach exposed the regions connected to emotions, dreams, memory, language and perception and to even more enigmatic events, such as religious or "paranormal" experiences.
One famous example was the case of Phineas Gage, a 19th century railroad worker who lost part of the front of his brain when a 1-metre-long iron pole was blasted through his head during an explosion. He recovered physically, but was left with permanent changes to his personality, showing for the first time that specific brain regions are linked to different processes.
Structure in mind
The most obvious anatomical feature of our brains is the undulating surfac of the cerebrum - the deep clefts are known as sulci and its folds are gyri. The cerebrum is the largest part of our brain and is largely made up of the two cerebral hemispheres. It is the most evolutionarily recent brain structure, dealing with more complex cognitive brain activities.
It is often said that the right hemisphere is more creative and emotional and the left deals with logic, but the reality is more complex. Nonetheless, the sides do have some specialisations, with the left dealing with speech and language, the right with spatial and body awareness.
See our Interactive Graphic for more on brain structure
Further anatomical divisions of the cerebral hemispheres are the occipital lobe at the back, devoted to vision, and the parietal lobe above that, dealing with movement, position, orientation and calculation.
Behind the ears and temples lie the temporal lobes, dealing with sound and speech comprehension and some aspects of memory. And to the fore are the frontal and prefrontal lobes, often considered the most highly developed and most "human" of regions, dealing with the most complex thought, decision making, planning, conceptualising, attention control and working memory. They also deal with complex social emotions such as regret, morality and empathy.
Below the cerebral hemispheres, but still referred to as part of the forebrain, is the cingulate cortex, which deals with directing behaviour and pain. And beneath this lies the corpus callosum, which connects the two sides of the brain. Other important areas of the forebrain are the basal ganglia, responsible for movement, motivation and reward.
Urges and appetites
Beneath the forebrain lie more primitive brain regions. The limbic system, common to all mammals, deals with urges and appetites. Emotions are most closely linked with structures called the amygdala, caudate nucleus and putamen. Also in the limbic brain are the hippocampus - vital for forming new memories; the thalamus - a kind of sensory relay station; and the hypothalamus, which regulates bodily functions via hormone release from the pituitary gland.
The back of the brain has a highly convoluted and folded swelling called the cerebellum, which stores patterns of movement, habits and repeated tasks - things we can do without thinking about them.
The most primitive parts, the midbrain and brain stem, control the bodily functions we have no conscious control of, such as breathing, heart rate, blood pressure, sleep patterns, and so on. They also control signals that pass between the brain and the rest of the body, through the spinal cord.
Source: Johns Hopkins Advanced Studies in Medicine (JHASiM) [more]
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The United States faces a medical emergency. Costs of the nation's healthcare system are growing so fast they are out of control. Many employers are dumping escalating healthcare expenses for both employees and their retired workers as fast as they can manage, fearing a loss of competitiveness. Currently, the average American consumes $6,420 worth of healthcare services a year. That's more than $12,200 a year for the average family. It's the most inefficient medical system among industrial nations. US healthcare costs have reached $1.6 trillion a year. That's 15 percent of the nation's economy, up from 5 percent in 1963. Other industrial nations devote less than 10 percent of gross domestic product to healthcare.
Advancements in medical technology and science means that people are living longer. This does not always mean that there is a high quality of life for those that are living longer though. Many of these people who would have died from a medical condition two decades ago can now live for a long time to come. These people often require a great deal of long-term care, whether it is at home or in a long-term care facility.
Those receiving long-term care at home require nurses to help them with their day-to-day tasks. The following is a quote taken directly from the Medicare website (http://www.medicare.gov/LongTermCare/Static/Home.asp)
"Generally, Medicare doesn't pay for long-term care. Medicare pays only for medically necessary skilled nursing facility or home health care. However, you must meet certain conditions for Medicare to pay for these types of care. Most long-term care is to assist people with support services such as activities of daily living like dressing, bathing, and using the bathroom. Medicare doesn't pay for this type of care called "custodial care". Custodial care (non-skilled care) is care that helps you with activities of daily living. It may also include care that most people do for themselves, for example, diabetes monitoring."
There is also a great deal of talk about whether or not Medicare will even be around in the coming decades. Consider the fact that 28% of the population will no longer be contributing to Medicare via taxes, while at the same time that 28% will be using more of the resources.
Thursday, July 24, 2008
Posted by Jacob Goldstein
They way Medicare pays doctors encourages excessive testing and discourages spending time with patients, a doctor argues today on the New York Times op-ed page.
The fee-for-service system reimburses doctors not only for their time, but also for overhead — which includes the costs of expensive machines used to run tests such as CT scans.
This is why doctors who own their own imaging equipment order far more scans than doctors who refer patients elsewhere for scans, argues the author, Peter B. Bach of Memorial Sloan-Kettering Cancer Center. He writes:
Any first-year business school student can see the profit opportunity here. The cost of a CT scanner is fixed, but a doctor earns fees each time it is used. This means that a scanner becomes highly profitable as soon as it’s paid for.
Patient visits, on the other hand, don’t incur the overhead of fancy machinery and so aren’t big moneymakers in the current system.
Getting rid of this payment system would trim excessive use of expensive tests and encourage docs to spend more time with patients instead, argues Bach, who is a former adviser to Medicare’s top brass.
He suggests paying doctors a fixed amount for each patient, with higher payments for more complex patients to discourage cherry picking. Payment for overhead should be based on the typical costs of tests and treatments for a patient’s condition — similar to how Medicare pays hospitals.
Implementing such a program would be pretty complicated — you could run the risk of giving doctors incentive to under-treat patients, and you’d have to do a good job of setting fees to avoid cherry picking.
Still, it’s worth considering alternatives to the current system. The recent debate in Washington over Medicare payments to doctors is sure to be back next year. And the health-policy gurus we’ve been talking to say financial pressures mean some kind of radical restructuring of the payment system is coming sooner or later.
Photo by Associated Press
Tuesday, July 31, 2007
Due to the high costs of medical treatment and surgery in the United States, the waiting lists in the United Kingdom, Australia and Canada and the lack of high tech medical procedures in many third world countries, medical tourism is expected to blossom into a ten billion dollar business world-wide. Recognizing this trend governments, large corporations, hospitals, and doctors are flooding the medical tourism market with choices, and prices are dropping in many countries world-wide.
The concept of medical tourism is not a new one. The first recorded instance of medical tourism dates back thousands of years to when Greek pilgrims traveled from all over the Mediterranean to the small territory in the Saronic Gulf called Epidauria. This territory was the sanctuary of the healing god Asklepios. Epidauria became the original travel destination for medical tourism.
Medical tourists can come from anywhere in the world, including Europe, the UK, the Middle East, Japan, and the U.S. This is because of their large populations, comparatively high wealth, the high expense of health care or lack of health care options locally, and increasingly high expectations of their populations with respect to health care.
Additionally, patients are finding that insurance either does not cover orthopedic surgery (such as knee/hip replacement) or imposes unreasonable restrictions on the choice of the facility, surgeon, or prosthetics to be used. Medical tourism for knee/hip replacements has emerged as one of the more widely accepted procedures because of the lower cost and minimal difficulties associated with the traveling to/from the surgery. Colombia provides a knee replacement for about $5,000 USD, including all associated fees such as FDA approved prosthetics and hospital stay over expenses. However, many clinics quote prices that are not all inclusive and include only the surgeon fees associated with the procedure
As the number of uninsured Americans grows, medical patients are now becoming consumers of medical care in record numbers. Many of these medical consumers are taking part in medical tourism i.e., people who leave the country primarily for medical treatment.
When a medical consumer searches for a provider, they tend to focus on the credentials of the doctor and forget about other important factors. Possibly the most important other factor is the country where the doctor and hospital are located. The country determines many things about the quality of care you will receive.
A large draw to medical travel is convenience and speed. Countries that operate public health-care systems are often so taxed that it can take considerable time to get non-urgent medical care. The time spent waiting for a procedure such as a hip replacement can be a year or more in Britain and Canada; however, in Singapore, Hong Kong, Thailand, Colombia, Philippines or India, a patient could feasibly have an operation the day after their arrival. In Canada, the number of procedures in 2005 for which people were waiting was 782,936
Factors that have led to the recent increase in popularity of medical travel include the high cost of health care or wait times for procedures in industrialized nations, the ease and affordability of international travel, and improvements in technology and standards of care in many countries of the world.
To understand the phenomenon of medical travel, we can compare the average costs of cosmetic surgeries between the industrialized nations and Latin America countries where medical tourism and cosmetic surgery tourism are becoming popular, such Argentina, Bolivia, Brazil, Costa Rica, Colombia, Philippines, Mexico. Prices quoted in the table below are from offices affiliated with the ministries of health in the U.S., Europe (France, Spain, Switzerland), Argentina, Bolivia, Brazil, Costa Rica, India, and Mexico.
Medical tourism carries some risks that local medical procedures do not. Should complications arise, patients might not be covered by insurance or able to seek compensation via malpractice lawsuits, though it should be noted that malpractice insurance is a considerable portion of the cost in the Western countries such as the US that allow doctors to be sued. The most outspoken critics of medical tourism are U.S. malpractice lawyers who see this emerging trend as a threat to their livelihood. Some countries currently sought after as medical tourism destinations provide some form of legal remedies for medical malpractice. However, this legal avenue is unappealing to the medical tourist. Advocates of medical tourism advise prospective tourists to evaluate the unlikely legal challenges against the benefits of such a trip before undergoing any surgery abroad.
Those involved in medical tourism should seek a hospital in country where government inspections of the hospital are mandated and the standards are high. But just this mandate is not enough. After all the results of the inspections may be known to only a few. Government should also mandate that the results be made public. Such a practice is now law in Germany for German hospitals and other countries in Europe. Wouldn't the medical tourism consumer want to know the results? After all, hospital infection rates vary widely and give the consumer a good idea about how well the hospital is managed.
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The best places in the world to have cancer00:01 17 July 2008
- NewScientist.com news service
- Michael Marshall
Follow the links in the article to explore an interactive map of cancer survival rates
Women with cancer of the breast, colon or rectum have the best chance of survival if they live in Cuba. Algeria, in contrast, is one of the worst places to be if you have cancer.
Those are just two of many conclusions from a worldwide study comparing survival rates in nearly 2 million cancer patients.
In general, people in North America, Western Europe and other developed countries do better than people from Africa, South America and Eastern Europe.
Within the US, the analysis showed that black people with cancer have a worse chance of survival than white people. For breast cancer, white women had an 84.7% chance of surviving for five years after diagnosis, while for blacks the figure was 70.9%. The black-white disparity was also true of each of the smaller sub-populations within the US that the team were able to analyse. New York was the worst overall city in the US to live in.
Michel Coleman of the London School of Hygiene and Tropical Medicine, and colleagues from around the world, pulled together data from 31 countries across five continents. They looked at cancer of the breast and prostate – in, respectively, women and men only – and of the colorectum in both sexes.
Countries vary in their background mortality rate for many reasons, including crime rates, food availability and water quality. Accordingly, the team calculated "relative survival rates", which attempt to eliminate variation caused by these factors.
Journal reference: The Lancet Oncology (DOI: 10.1016/S1470-2045(08)70179-7)
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