,, September 27, 2010, by Marilynn Marchione, BOSTON — Cancer patients, brace yourselves. Many new drug treatments cost nearly $100,000 a year, sparking fresh debate about how much a few months more of life is worth.

The latest is Provenge, a first-of-a-kind therapy approved in April. It costs $93,000 and adds four months’ survival, on average, for men with incurable prostate tumors. Bob Svensson is honest about why he got it: insurance paid.

“I would not spend that money,” because the benefit doesn’t seem worth it, says Svensson, 80, a former corporate finance officer from Bedford, Mass.

His supplemental Medicare plan is paying while the government decides whether basic Medicare will cover Provenge and for whom. The tab for taxpayers could be huge – prostate is the most common cancer in American men. Most of those who have it will be eligible for Medicare, and Provenge will be an option for many late-stage cases. A meeting to consider Medicare coverage is set for Nov. 17.

“I don’t know how they’re going to deal with that kind of issue,” said Svensson, who was treated at the Lahey Clinic Medical Center in suburban Boston. “I feel very lucky.”

For the last decade, new cancer-fighting drugs have been topping $5,000 a month. Only a few of these keep cancer in remission so long that they are, in effect, cures. For most people, the drugs may buy a few months or years. Insurers usually pay if Medicare pays. But some people have lifetime caps and more people are uninsured because of job layoffs in the recession. The nation’s new health care law eliminates these lifetime limits for plans that were issued or renewed on Sept. 23 or later.

Celgene Corp.‘s Revlimid pill for multiple myeloma, a type of blood cancer, can run as much as $10,000 a month; so can Genentech‘s Avastin for certain cancers. Now Dendreon Corp. ‘s Provenge rockets price into a new orbit.

Unlike drugs that people can try for a month or two and keep using only if they keep responding, Provenge is an all-or-nothing $93,000 gamble. It’s a one-time treatment to train the immune system to fight prostate tumors, the first so-called “cancer vaccine.”

It’s also in short supply, forcing the first rationing of a cancer drug since Taxol and Taxotere were approved 15 years ago. At the University of Texas M.D. Anderson Cancer Center, doctors plan a modified lottery to decide which of its 150 or so eligible patients will be among the two a month it can treat with Provenge. An insurance pre-check is part of the process to ensure they financially qualify for treatment.

“I’m fearful that this will become a drug for people with more resources and less available for people with less resources,” said M.D. Anderson’s prostate cancer research chief, Dr. Christopher Logothetis.

For other patients on other drugs, money already is affecting care:

_Job losses have led some people to stop taking Gleevec, a $4,500-a-month drug by Novartis AG that keeps certain leukemias and stomach cancers in remission. Three such cases were recently described in the New England Journal of Medicine, and all those patients suffered relapses.

_Retirements are being delayed to preserve insurance coverage of cancer drugs. Holly Reid, 58, an accountant in Novato, Calif., hoped to retire early until she tried cutting back on Gleevec and her cancer recurred. “I’m convinced now I have to take this drug for the rest of my life” and will have to work until eligible for Medicare, she said.

_Lifetime caps on insurance benefits are hitting many patients, and laws are being pushed in dozens of states to get wider coverage of cancer drugs. In Quincy, Mass., 30-year-old grad student Thea Showstack testified for one such law after pharmacists said her first cancer prescription exceeded her student insurance limit. “They said ‘OK, that will be $1,900,'” she said. “I was absolutely panicked.” The federal health care law forbids such caps on plans issued or renewed Sept. 23 or later.

_Tens of thousands of people are seeking help from drug companies and charities that provide free medicines or cover copays for low-income patients. Genentech’s aid to patients has risen in each of the last three years and the company says nearly 85 percent of Americans earn less than $100,000, making them potentially eligible for help if no other programs like Medicaid will pay.

_Doctors and insurers increasingly are doing the cruel math that many cancer patients want to avoid, and questioning how much small improvements in survival are worth. A recent editorial in a medical journal asked whether the extra 11 weeks that Genentech’s Herceptin buys for stomach cancer patients justified the $21,500 cost.

Doctors also have questioned the value of Genentech’s Tarceva for pancreatic cancer. The $4,000-a-month drug won approval by boosting median survival by a mere 12 days. Here’s how to think about this cost: People who added Tarceva to standard chemotherapy lived nearly 6 1/2 months, versus 6 months for those on chemo alone. So the Tarceva folks spent more than $24,000 to get those extra 12 days.

When is a drug considered cost-effective?

The most widely quoted figure is $50,000 for a year of life, “though it has been that for decades – never really adjusted – and not written in stone,” said Dr. Harlan Krumholz, a Yale University expert on health care costs.

Many cancer drugs are way over that mark. Estimates of the cost of a year of life gained for lung cancer patients on Erbitux range from $300,000 to as much as $800,000, said Dr. Len Lichtenfeld, the American Cancer Society’s deputy chief medical officer.

Higher costs seem to be more accepted for cancer treatment than for other illnesses, but there’s no rule on how much is too much, he said.

Insurers usually are the ones to decide, and they typically pay if Medicare pays. Medicare usually pays if the federal Food and Drug Administration has approved the use.

“Insurance sort of isolates you from the cost of health care,” and if people lose coverage, they often discover they can’t afford their medicines, said Dr. Alan Venook, a cancer specialist at the University of California, San Francisco. He wrote in the New England Journal in August about three of his patients who stopped taking or cut back on Gleevec because of economic hardship.

Two of the three now are getting the drug from its maker, Novartis AG, which like most pharmaceutical companies has a program for low-income patients. About 5,000 patients got help for Gleevec last year, said Novartis spokesman Geoffrey Cook.

“We have seen a steady increase in requests over the past few years” as the economy worsened, he said.

Showstack, whose leukemia was diagnosed last year, gets Gleevec from Novartis. The dose she’s on now would cost $50,000 a year.

“I’m not actually sure that I know anyone who could afford it,” she said.

Gleevec’s cost is easier to justify, many say, because it keeps people alive indefinitely – a virtual cure. About 2,300 Americans died each year of Showstack’s form of leukemia before Gleevec came on the market; only 470 did last year.

“I don’t think we quibble with a drug that buys people magical quality of life for years,” Venook said.

It’s unclear whether Provenge will ever do that – it needs to be tested in men with earlier stages of prostate cancer, doctors say. So far, it has only been tried and approved for men with incurable disease who have stopped responding to hormone therapy. On average, it gave them four months more, though for some it extended survival by a year or more.

Until it shows wider promise, enthusiasm will be tepid, said Dr. Elizabeth Plimack a prostate specialist at the Fox Chase Cancer Center in Philadelphia.

“I’ve not had any patient ask for it,” she said. “They ask about it. Based on the information, they think the cost is tremendous, and they think the benefit is very small.”

Logothetis, at M.D. Anderson, said Provenge and other experimental cancer vaccines in development need “a national investment” to sort out their potential, starting with Medicare coverage.

“It’s no longer a fringe science. This is working,” he said. “We need to get it in the door so we can evolve it.”

Personal Exoskeletons for Paraplegics

Assisted Steps: A patient with paralysis stands with the aid of the Berkeley exoskeleton. The exoskeleton moves the patient’s hips and knees to imitate a natural walk.   Credit: University of California, Berkeley

A mobile device helps patients with spinal cord injuries walk.

MIT Technology Review, September 27, 2010, by Kristina Grifantini  —  Exoskeletons–wearable, motorized machines that can assist a person’s movements–have largely been confined to movies or military use, but recent advances might soon bring the devices to the homes of people with paralysis.

So far, exoskeletons have been used to augment the strength of soldiers or to help hospitalized stroke patients relearn how to walk. Now researchers at the University of California, Berkeley, have demonstrated an exoskeleton that is portable and lets paraplegics walk in a relatively natural gait with minimal training. That could be an improvement for people with spinal-cord injuries who spend a lot of time in wheelchairs, which can cause sores or bone deterioration.

Existing medical exoskeletons for patients who have lost function in their lower extremities have either not been equipped with power sources or have been designed for tethered use in rehabilitation facilities, to correct and condition a patient’s gait.

In contrast, the Berkeley exoskeleton combines “the freedom of not being tethered with a natural gait,” says Katherine Strausser, PhD candidate and one of the lead researchers of the Berkeley project. Last week at the 2010 ASME Dynamic System and Control Conference in Cambridge, Massachusetts, Strausser presented experimental results from four paraplegics who used the exoskeleton.

Other mobile exoskeletons–like those developed by companies such as Rex Bionics or Cyberdene–don’t try to emulate a natural gait, Strausser says. Because walking is a dynamic motion that is essentially falling forward, Strausser says, many designs opt for a shuffle instead of a natural gait, because “it’s safer and a lot easier.” However, emulating a natural gait mimics the efficiency of natural walking and doesn’t strain the hips, Strausser says.

The Berkeley device, which houses a computer and battery pack, straps onto a user’s back like a backpack and can run six to eight hours on one charge. Pumps drive hydraulic fluid to move the hip and knees at the same time, so that the hip swings through a step as one knee bends. The device plans walking trajectories based on data (about limb angles, knee flexing, and toe clearance) gathered from people’s natural gaits. Pressure sensors in each heel and foot make sure both feet aren’t leaving the ground at the same time.

The Berkeley program was successful. The four paraplegics described in Strausser’s talk, three of whom had been in wheelchairs for years, were able to walk with the device after only two hours of training. “It’s very easy to walk in,” says Strausser. “It moves your leg exactly like you would in your normal gait.” To begin a step, the exoskeleton requires a user to press a button on a remote control; the team is working on a more intuitive interface.

When designing the medical exoskeleton–which uses parts from two military exoskeletons–the team needed controllers and a design that takes into account the user’s lack of strength. While military exoskeletons work with a soldier’s motion to add strength, medical exoskeletons do the opposite, fighting against incorrect gaits or performing the gait, explains Strausser. “The biggest problem is holding a person into the ‘exo’ safely and securely,” she says. After field testing at the University of Virginia’s Clinical Motion Analysis and Motor Performance Laboratory last year, the group developed a proprietary design that keeps users from sliding out of the exoskeleton and distributes the weight of the 80-pound machine. The group plans to make the device lighter and to make a low-cost version that patients can use in their homes. (The research group is affiliated with a company, Berkeley Bionics, that plans to begin selling a form of the technology.)

“Overall I think it’s a very good device,” says Panagiotis Artemiadis, an MIT researcher who heard Strausser’s talk. He is developing an exoskeleton called the MIT-SkyWalker that helps stroke patients practice walking on a machine that resembles a treadmill. He says he can picture the Berkeley device being used by patients in their homes, particularly if the researchers reduce the weight.

Other mobile exoskeletons to help paralyzed people are just starting to come to market. German company Argo Medical Technologies is releasing its first product, a 100,000-euro exoskeleton intended for use in rehab centers, in October. The company plans to release a home version soon after for about half the price. Unlike the Berkeley exoskeleton, this one, dubbed ReWalk, takes the user a few weeks to learn. “It’s like getting a driver’s license,” says John Frijters, vice president of business development for Argo. ReWalk is customizable, able to tailor the sensitivity of the sensors, step length, and stride depending on how the user feels. It weighs about 45 pounds and runs eight to 10 hours on a charge, according to Frijters.

While ReWalk doesn’t yet have data to share on the advantages of using exoskeletons, “dozens” of patients have tested ReWalk, and “they all enjoy the benefit of being active,” says Frijters. “They have the opportunity to get up from the wheelchair and walk again. It’s very emotional.”

Mind control: PhD student Michele Tavella operates a wheelchair that uses “shared control” to navigate. Brain signals are translated into simple commands like “forward” or “left”; the chair then steers itself around any obstacles.
Credit: EPFL

Artificial intelligence improves a wheelchair system that could give paralyzed people greater mobility. A robotic wheelchair combines brain control with artificial intelligence to make it easier for people to maneuver it using only their thoughts. The approach, known as “shared control,” could help paralyzed people gain new mobility by turning crude brain signals into more complicated commands

MIT Technology Review, September 27, 2010, by Duncan Graham-Rowe  —   The wheelchair, developed by researchers at the Federal Institute of Technology in Lausanne, features software that can take a simple command like “go left” and assess the immediate area to figure out how to follow the command without hitting anything. The software can also understand when the driver wants to navigate to a particular object, like a table.

Several technologies allow patients to control computers, prosthetics, and other devices using signals captured from nerves, muscles, or the brain. Electroencephalography (EEG) has emerged as a promising way for paralyzed patients to control computers or wheelchairs. A user needs to wear a skullcap and undergo training for a few hours a day over about five days. Patients control the chair simply by imagining they are moving a part of the body. Thinking of moving the left hand tells the chair to turn left, for example. Commands can also be triggered by specific mental tasks, such as arithmetic.

But EEG has limited accuracy and can only detect a few different commands. Maintaining these mental exercises when trying to maneuver a wheelchair around a cluttered environment can also be very tiring, says, José del Millán, director of noninvasive brain-machine interfaces at the Federal Institute of Technology, who led the project. “People cannot sustain that level of mental control for long periods of time,” he says. The concentration required also creates noisier signals that can be more difficult for a computer to interpret.

Shared control addresses this problem because patients don’t need to continuously instruct the wheelchair to move forward; they need to think the command only once, and the software takes care of the rest. “The wheelchair can take on the low-level details, so it’s more natural,” says Millán.

The wheelchair is equipped with two webcams to help it detect obstacles and avoid them. If drivers want to approach an object rather than navigate around it, they can give an override command. The chair will then stop just short of the object.

In Millán’s prototype, 16 electrodes monitor the user’s brain activity. So far it hasn’t been tested on any paralyzed patients.

Damien Coyle, a researcher in the Brain-Computer Interfacing and Assistive Technology group at the University of Ulster, says EEG signals can be slow and tricky to work with. Because of this, he says, many researchers are looking at ways to use shared control, and Millán’s project is a good example of it being put into practice. “The more shared control you have, the better the brain-computer interface, and the faster the person can get from one place to another,” Coyle says.

Millán’s team is developing object recognition capabilities to make the chair smart enough to automatically “dock” with a table or desk to ensure the chair is close enough and not skewed at an angle.

Freedom to move: The Fluidhand (above) uses lightweight miniature hydraulics to enable the wearer to move each finger individually.
Credit: The Research Center, Karlsrühe/Forschungszentrum

A lightweight prosthetic hand uses hydraulics to achieve more natural finger movement



MIT Technology Review, by Kate Baggott  —  A lightweight hydraulic hand with individually powered fingers could change the lives of amputees, say researchers in Germany. The Fluidhand, according to its developers, is lighter, behaves more naturally, and has greater flexibility than artificial hands that use motorized fingers.

The Fluidhand prototype, developed by a team led by Stefan Schulz at the Research Center in Karlsrühe, in partnership with the Orthopedic University Hospital, in Heidelberg, Germany, has flexible drives located in each of its finger joints, enabling the wearer to move each finger independently. Lightweight miniature hydraulics are connected to elastic chambers that can flex the joints of the fingers. As sensors on the fingers and palm close around objects, nerves in the amputation stump pick up muscular sensations so that the amputee can use a weaker or stronger grip. The prosthetic provides five different strengths of grip.

“It is so intuitive that learning to use the device only takes about 15 minutes,” says Schulz.

Last September, 18-year-old Sören Wolf, who was born with only one hand, became the first person to use the Fluidhand. According to German press reports, Wolf was able to type on a keyboard with both of his hands for the first time in his life, and he told reporters that, when he’s wearing the Fluidhand, he doesn’t feel handicapped anymore.

International interest in the Fluidhand peaked late last month, when it was announced that the Orthopedic University Hospital is testing the device in comparison with the i-LIMB Hand. Wolf is the first amputee to use both prosthetics.

Produced by the Scottish company Touch Bionics, i-LIMB was the first prosthetic hand that enabled the movement of individual fingers. The prosthetic, released last summer, uses a different technical principle than the Fluidhand. With i-LIMB, movement is enabled by five small, battery-powered motors that are embedded in each finger. Schulz believes that the hydraulic system has some advantages over the motorized fingers. “In contrast to the movement with electric motors and transmissions, the Fluidhand remains soft and flexible,” he says. “Articles can therefore be seized more reliably, and the hand feels more natural.”

Both devices are significant improvements over conventional hand prostheses that only enable the wearer to pinch the thumb and forefinger to create a grip.

“There are many hand movements that require individual digit movements,” says Hugh Herr, director of the Biomechatronics Group at the MIT Media Lab. “The development of individual finger movements in a prosthetic is a remarkable step forward.”

One patient is currently wearing the Fluidhand to complete daily tasks, and a second is about to be fitted for the device. Some 250 people, including soldiers wounded in Afghanistan and Iraq, already use i-LIMB.

Stuart Mead, CEO of Touch Bionics, points out that the comparative study in Heidelberg is not a competitive one. “Many people have many different devices for different activities, and what works for one patient may not work for another,” he says.

Comparative studies of this nature do have value for determining how well the device can meet amputees’ needs. “They are probably testing each device’s strength, power, and versatility,” says Herr. “The prosthetics have to be able to pick up something very lightweight and fragile, like a piece of china, as well as something large and heavy.”

Soon, people requiring a prosthetic hand with movable digits will have more options. “The German-Austrian company OttoBock will probably present a new hand with movable fingers in 2009,” says Schulz.

Experts expect this rapid development in the field of prosthetic technologies to continue into the near future.

“I believe that there is a big push into wearable exoskeletons because the mechatronic technology has matured, becoming more cost effective, miniaturized, and powerful,” says Thomas Sugar of Arizona State University, who works in robotic prosthetics. “Batteries and motors are smaller and more powerful. Microprocessors have been very fast and cheap. Lastly, I do think there has been a big push by NIH [National Institutes of Health] and the DOD [Department of Defense] into medical robots for stroke therapy, powered exoskeletons, and powered prosthetics.”

The Biomechatronics Group’s Herr agrees. “Typically, when you plot prosthetic innovations against time, you see a spike in innovation after every war, and that is certainly true today,” he says. “In addition, we’re also seeing a number of disciplines such as robotics, mechanical engineering, and biomechatronics mature to the point [where] we can merge to create truly remarkable systems.”

There is still room for those remarkable innovations in prosthetic development.

“We find ourselves, as an industry, working to manage people’s expectations,” says Touch Bionics’ Mead. “A prosthetic doesn’t function like a real hand. We’re still only able to replicate 5 to 10 percent of what a real hand can do.”

Walking the walk: A quasi-passive MIT exoskeleton bears most of an 80-pound payload without needing any motors.   
Credit: Samuel Au

Researchers have developed a motorless exoskeleton that can carry 80 pounds


MIT Technology Review, by Duncan Graham-Rowe  —  Researchers at MIT have developed a leg exoskeleton capable of carrying an 80-pound load without the use of motors. According to its developers, the prototype can support 80 percent of this weight while using less than one-thousandth of a percent of the power used by its motorized equivalents.

The aim of developing leg exoskeletons is to make it easier for people to carry heavy loads, says Hugh Herr, director of the Biomechatronics Group at MIT and leader of the research. By designing mechanical structures that transfer much of the load directly to the ground, rather than via the walker’s legs, it should be possible to enable soldiers and firefighters to carry heavier loads while reducing the risk of injury and the amount of metabolic effort they expend in doing so.

To date, most exoskeleton research has focused on using motors to carry the load. Not only is this expensive, requiring large power supplies and frequent refueling, but it also tends to be noisy, which can be a problem for military applications. Conor Walsh, a graduate student at MIT who also worked on the exoskeleton, says that the system “is much quieter than the powered exoskeletons” and only slightly noisier than normal human walking.

Working with Ken Endo, also an MIT graduate student, Herr and Walsh have taken a quasi-passive approach. Their mechanical system is specially designed to follow the movement of the wearer’s legs and mimic some of the energy-storage strategies that legs exploit to reduce muscle work.

When we walk, the muscle power required to swing our legs is minimal because of the pendulum-like exchange of gravitational potential energy and the kinetic energy of our limbs. Our muscles also provide a degree of elastic energy storage to help joints flex, which again reduces the amount of overall energy that walking requires.

The MIT exoskeleton works using similar principles. The payload worn on the user’s back is attached to two leglike mechanical structures that run parallel to the user’s legs. These structures have elastic energy-storage devices at the ankle and hip, and a damping device at the knee joint.

In simple terms, the springlike joints take advantage of the user’s motion and payload to store energy. For example, as the heel of one foot makes contact with the ground, the continued forward motion of the body will cause springs in that hip and ankle to be compressed. These springs help propel the leg forward at the next stride.

A variable damper in the knee joint lets the leg swing freely as it moves forward. Then, as the heel strikes the ground, the damping is increased to prevent the knee from buckling under the weight of the payload.

The exoskeleton is not entirely passive. A small amount of energy is required to control the dampers’ variability. (The dampers contain a fluid with tiny magnetic particles. When electricity is applied to the fluid, these particles change its viscosity.) But it is very efficient compared with other such systems. “Our exoskeleton only consumes two watts of electrical power during walking,” says Herr. This is nothing compared with the 3,000 watts consumed by a motorized exoskeleton.

But there is a catch. Tests of the exoskeleton revealed that although it lightens the load for the user, that person consumes 10 percent more oxygen than if he or she had simply carried the load without mechanical assistance. This higher metabolic rate is attributed to the fact that the device interferes with the natural gait of the walker. “Walking with the exoskeleton takes more energy than walking without,” says Michael Goldfarb, director of the Center for Intelligent Mechatronics at Vanderbilt University, in Nashville, TN.

Even so, it is a good effort, says Goldfarb. “I’m not aware of any exoskeleton–active or passive–that has been shown to effectively decrease metabolic energy expenditure,” he says. And even if more energy is burned, the exoskeleton still reduces the stress on the wearer’s back and legs.

The MIT group believes that by carefully selecting and angling the springs, it can reduce the amount of energy that a person needs to walk with the exoskeleton.

It would probably take about two years to commercialize this technology, says Herr. “But we have no plans at this time to move forward with commercialization,” he says.

Goldfarb still believes that there are hurdles to overcome. There are great advantages to using variable dampers and springs, not least that they are much lighter and less power hungry than motors and actuators, he says. But a device that requires less effort and is capable of covering a broad range of terrains, such as uneven surfaces and stairs, must have not just variable dampers but also springs of variable stiffness. This is a taller order, Goldfarb says., September 27, 2010, by Max Miller  —  We spend one-third of our lives asleep—for an average American, that’s over 26 years—yet sleep remains one of the biggest mysteries of neuroscience. With brains scans, scientists have learned much about what happens in our heads during sleep, but they still can’t answer the simple question: why do we sleep? There are theories, of course (summarized in the takeaway below), but one thing is very clear: without sleep, our brain begins to malfunction.

Columbia University neuropsychologist Yaakov Stern tells Big Think that people’s abilities to perform simple tasks drops dramatically after 48 hours without sleep. But some people are affected more than others. What Stern’s research hoped to answer was why some brains are better able to cope with sleeplessness than others, with the hopes of potentially minimizing our biological need for sleep.

First, Stern located a neural network, mostly in the occipital and parietal lobes of the brain, that seemed to determine whether a person coped well or poorly without sleep. Then he used Transcranial Magnetic Stimulation (TMS) to stimulate these areas that were affected by sleep deprivation.  “Our hope was that if we stimulated that area, we could improve people’s performance,” he tells Big Think. “And what we found, which was surprising to me was that, first of all, the stimulation to the occipital area did help people respond a little faster compared to some other area that had nothing to do with the network.  And the people who benefited most from that stimulation were the people who had showed the most reduction in the network, which is another confirmation that we were finding something interesting.”

Stern’s studies may suggest future ways to mitigate sleep deprivation, but they don’t lead us any closer to understanding the function of sleep. Nor do they explain the nightly hallucinations we call dreams. Dreams occur mostly during REM sleep, a stage of sleep characterized by heightened brain activity. During a normal night of sleep, the brain cycles repeated back and forth between REM sleep and three stages of non-REM sleep: Stage 1, the twilight period between sleeping and waking which occurs only at the beginning of sleep; Stage 2, light sleep which accounts for 60% of night’s rest; and Stage 3, deep sleep, during which most sleep disorders occur. 

In her Big Think interview, Shelby Harris, the director of the behavioral sleep medicine program at Montefiore Medical Center in the Bronx, told us that we normally cycle through these stages five or six times in a night and that REM sleep (and therefore dreaming) becomes more prevalent the long er we sleep. “That’s why people tend to remember their dreams in the morning a little bit better,” she explains. But what should we do with the fuzzy dream images that we do manage to hold onto? Are they really the “golden highway to the unconscious,” as Freud believed? Can we learn more about ourselves by trying to interpret them?

Harris doesn’t think so. As she explains in the video below, our understanding of dreams has changed dramatically in the past century. Freud and Jung believed that dreams are the way that the subconscious communicates with the conscious mind. If a person experiences anxiety or fear in a dream, analyzing the dream might help him understand why he is anxious in the first place and what he could do to mitigate that anxiety during the day. But modern theories don’t place as much stock in the actual content of the dreams. Harris thinks dreams are the brain’s method of sorting memories and experiences from the previous day, deciding which ones to retain and which ones to discard. 


Though scientists haven’t found conclusive evidence for why our brains need so much sleep, there are some interesting theories:

Information processing theory — Several studies have suggested that REM sleep and/or non-REM sleep might be important for the brain’s ability to process and consolidate memories from the previous day, forming new neural networks and strengthening others. Related studies have also suggested that sleep helps clear away unimportant information, making room for new neural connections.

Damage reversal theory — During waking hours, neurons in the brain are subjected to the wear-and-tear of oxidative stress caused by free radicals; one theory holds that the cool-down period of sleep help to regulate homeostasis in the body and brain and to repair any damage that has occurred during waking.

Adaptive inactivity theory — Last year UCLA neuroscientist Jerome Siegel proposed that sleep might not be physiologically necessary to animals at all. He hypothesized that rather than serving some universally vital, but unknown, function in animals, sleep actually emerged because of its evolutionary benefits: sleep optimizes the timing and duration of behavior, conserving energy and protecting them from certain dangers. Across the animal kingdom there is wide variability in sleep duration, and Siegel suggests that ecological variables more so than biological needs dictate the timing and duration of sleep for different species. 

More Resources

— “Sleep viewed as a state of adaptive inactivity” (2009) published by Jerome Siegel in Nature

—    Time magazine article about our biological need for sleep