When you think about how your brain looks, you probably picture a roundish, two-lobed gray mass covered in "wrinkles." As humans evolved as a species, our brains grew larger to accommodate all of the higher functions that set us apart from other animals. But in order to keep the brain compact enough to fit into a skull that would actually be in proportion with the rest of our body size, the brain folded in on itself as it grew. If we unfolded all of those ridges and crevices, the brain would be the size of a pillowcase. The ridges are called gyri and the crevices are called sulci. Several of these ridges and crevices even have names, and there are variations in exactly how they look from person to person.

We don't start out with wrinkly brains, however; a fetus early in its development has a very smooth little brain. As the fetus grows, its neurons also grow and migrate to different areas of the brain, creating the sulci and gyri. By the time it reaches 40 weeks, its brain is as wrinkled as yours is (albeit smaller, of course). So we don't develop new wrinkles as we learn. The wrinkles we're born with are the wrinkles we have for life, assuming that our brains remain healthy.

Our brains do change when we learn -- it's just not in the form of additional sulci and gyri. This phenomenon is known as brain plasticity. By studying changes in the brains of animals like rats as they learn tasks, researchers have discovered that synapses (the connections between neurons) and the blood cells that support neurons grow and increase in number. Some believe that we get new neurons when we make new memories, but this hasn't yet been proven in mammalian brains like ours.

If you've ever gotten the feeling that there were hidden messages in commercials, TV shows or movies, the next myth should interest you.

The concept of subliminal messages feeds into our suspicions about what the government, bug corportations and media are really trying to tell us. A subliminal message (meaning, below "limen," or our conscious perception threshold) is a message embedded into images or sound meant to penetrate into our subconscious and influence our behavior. The first person to coin the term was James Vicary, a market researcher. In 1957, Vicary stated that he inserted messages into a showing of a movie in New Jersey. The messages, which flashed for 1/3000th of a second, told moviegoers to drink Coca-Cola and eat popcorn.

According to Vicary, Coke sales in the theater increased by more than 18 percent and popcorn sales by more than 57 percent, proving that his subliminal messages worked. Books published in the late 1950s and early 1970s outlined how advertisers could use techniques like Vicary's to convince consumers to buy their products. Some radio and TV commercials included subliminal messages, but many networks and professional associations banned them. In 1974, the FCC banned the use of subliminal advertising.

But did the messages work? Turns out, Vicary actually lied about the results of his study. Subsequent studies, including one which flashed the message "Call now" during a broadcast on a Canadian TV station, had no effect on viewers. The infamous 1990s Judas Priest trial, in which the families of two boys who committed suicide claimed that a song told the boys to do it, ended with the judge stating that there was no scientific evidence in their favor. Yet some people still claim that music, as well as advertisements, contains hidden messages.

So listening to those self-help tapes while you sleep probably can't hurt you, but they aren't likely to help you quit smoking, either.

When it comes to the human brain versus other animals' brains, does size matter?

Many animals can use their brains to do some of the things that humans can do, such as finding creative ways to solve problems, exhibiting self-awareness, showing empathy toward others and learning how to use tools. But although scientists can't agree on a single definition of what makes a person intelligent, they do generally agree that humans are the most intelligent creatures on Earth. In our "bigger is better" society, then, it might stand to reason that humans should have the biggest brains of all animals, because we're the smartest. Well, not exactly.

The average adult human brain weighs about 3 pounds (1,361 grams). The dolphin -- a very intelligent animal -- also has a brain that weighs about 3 pounds on average. But a sperm whale, not generally considered to be as intelligent as a dolphin, has a brain that weighs about 17 pounds (7,800 grams). On the small end of the scale, a beagle's brain is about 2.5 ounces (72 grams), and an orangutan's brain is about 13 ounces (370 grams). Both dogs and orangutans are pretty smart animals, but they have small brains. A bird like a sparrow has a brain that weighs less than half an ounce (1 gram).

You may notice something important in all of those comparisons. An average dolphin's body weighs about 350 pounds (158.8 kilograms), while a sperm whale can weigh as much as 13 tons. In general, the larger the animal, the larger the skull, and therefore, the larger the brain. Beagles are fairly small dogs, at about 25 pounds (11.3 kg) maximum, so it stands to reason that their brains would also be smaller. The relationship between brain size and intelligence isn't really about the actual weight of the brain; it's about the ratio of brain weight to the entire body weight. For humans, that ratio is about 1-to-50. For most other mammals, it's 1-to-180, and for birds, it's 1-to-220. The brain takes up more weight in a human than it does in other animals.

Intelligence also has to do with the different components of the brain. Mammals have very large cerebral cortexes, unlike birds, fish or reptiles. The cerebellum in mammals houses the cerebral hemispheres, which are responsible for higher functions like memory, communication and thinking. Humans have the largest cerebral cortex of all mammals, relative to the size of their brains.

At one time in history, decapitation was one of the preferred methods of execution, in part thanks to the guillotine. Although many countries that executecriminals have dispatched with the method, it's still performed by certain governments, terrorists and others. There's nothing more final than the severing of one's head. The guillotine came about because of the desire for a quick, relatively humane death. But how quick is it? If your head were cut off, would you still be able to seeor otherwise move it, even for just a few seconds? 

This concept perhaps first appeared during the French Revolution, the very time period in which the guillotine was created. On July 17, 1793, a woman named Charlotte Corday was executed by guillotine for the assassination of Jean-Paul Marat, a radical journalist, politician and revolutionary. Marat was well-liked for his ideas and the mob awaiting the guillotine was eager to see Corday pay. After the blade dropped and Corday's head fell, one of the executioner's assistants picked it up and slapped its cheek. According to witnesses, Corday's eyes turned to look at the man and her face changed to an expression of indignation. Following this incident, people executed by guillotine during the Revolution were asked to blink afterward, and witnesses claim that the blinking occurred for up to 30 seconds.

Another often-told tale of demonstrated consciousness following beheading dates to 1905. French physician Dr. Gabriel Beaurieux witnessed the beheading of a man named Languille. He wrote that immediately afterward, "the eyelids and lips ... worked in irregularly rhythmic contractions for about five or six seconds." Dr. Beaurieux called out his name and said that Languille's eyelids "slowly lifted up, without any spasmodic contraction" and that "his pupils focused themselves" [source: Kershaw. This happened a second time, but the third time Beaurieux spoke, he got no response.

These stories seem to give credence to the idea that it's possible for someone to remain conscious, even for just a few seconds, after being beheaded. However, most modern physicians believe that the reactions described above are actually reflexive twitching of muscles, rather than conscious, deliberate movement. Cut off from the heart (and therefore, from oxygen), the brain immediately goes into a coma and begins to die. According to Dr. Harold Hillman, consciousness is "probably lost within 2-3 seconds, due to a rapid fall of intracranial perfusion of blood.'

So while it's not entirely impossible for someone to still be conscious after being decapitated, it's not likely. Hillman also goes on to point out that the so-called painless guillotine is likely anything but. He states that "death occurs due to separation of the brain and spinal cord, after transection of the surrounding tissues. This must cause acute and possibly severe pain." This is one of the reasons why the guillotine, and beheading in general, is no longer an accepted method of execution in many countries with capital punishment.

If your head stays on your shoulders, though, it can still be damaged beyond repair.

Brain damage is an extremely scary thing. For something so mysterious and amazing, the brain can actually be quite fragile and susceptible to a multitude of injuries. Brain damage can be caused by anything from an infection to a car accident, and it essentially means the death of brain cells. To many people, the mere idea of brain damage conjures images of people in persistent vegetative states, or at the very least, permanent physical or mental disability.

But that's not always the case. There are many different types of brain damage, and exactly how it will affect someone depends largely on its location and how severe it is. A mild brain injury such as a concussion, usually occurs when the brain bounces around inside the skull, resulting in bleeding and tearing. The brain can recover from minor injuries remarkably well; the vast majority of people who experience a mild brain injury don't experience permanent disability.

On the other end of the spectrum, a severe brain injury means that the brain has suffered extensive damage. It sometimes requires surgery to remove built-up blood or relieve pressure. For nearly all patients who live through a severe brain injury, permanent, irreversible damage results.

So what about those in between? Some people with brain damage experience permanent disability but can recover partially from their injury. If neurons are damaged or lost, they can't grow back -- but the synapses, or connections between neurons, can. Essentially, the brain creates new pathways between neurons. In addition, areas of the brain not originally associated with some functions can take over and allow the patient to relearn how to do things. Remember the phenomenon of brain plasticity mentioned in the myth about brain wrinkles? That's how stroke patients, for example, can regain speech and motor skills through therapy.

The important thing to remember is that there are still a lot of unknowns about the brain. When a person is diagnosed with a brain injury, it's not always possible for doctors to know exactly how well someone will be able to recover from the damage. Patients surprise doctors all the time and exceed expectations of what they're able to do days, months and even years later. Not all brain damage is permanent.

Exactly how different drugs affect your brain is a pretty controversial subject. Some people claim that only the most severe drug use can have any lasting effects, while others believe that the first time you use a drug, you're causing long-term damage. One recent study states that using drugs like marijuana only cause minor memory loss, while another claims that heavy marijuana use can permanently shrink parts of your brain. When it comes to using drugs like cocaine or Ecstacy some people even believe that you can actually get holes in your brain.

In truth, the only thing that can actually put a hole in your brain is physical trauma to it. Researchers do claim that drugs can cause short-term and long-term changes in the brain. For example, drug use can lower the impact of neurotransmitters (chemicals used to communicate signals in the brain) like dopamine, which is why addicts need more and more of the drug to achieve the same feeling. In addition, changes in the levels of neurotransmitters can result in problems with neuron function. Whether this is reversible or not is also up for debate.

On the other hand, a study in New Scientist from August 2008 states that long-term use of some drugs actually causes certain structures in the brain to grow, resulting in a permanent change. They claim that this is which is why it's so difficult to change the behaviors of addicts.

But although the jury's still out on exactly how different drugs can affect your brain for the long term, we can be reasonably sure of one thing: No drug actually puts holes in your brain.

Just one observation of a drunken person is enough to convince you that alcohol directly affects the brain. People who drink enough to get drunk often end up with slurred speech and impaired motor skills and judgment, among other side effects. Many of them suffer from headaches, nausea and other unpleasant side effects afterward -- in other words, a hanover. But are a few drinks on the weekend, or even the occasional long drinking session, enough to kill brain cells? What about binge drinking or the frequent, sustained drinking of alcoholics?

Not so much. Even in alcoholics, alcohol use doesn't actually result in the death of brain cells. It can, however, damage the ends of neurons, which are called dendrites. This results in problems conveying messages between the neurons. The cell itself isn't damaged, but the way that it communicates with others is altered. According to researchers such as Roberta J. Pentney, professor of anatomy and cell biology at the University at Buffalo, this damage is mostly reversible.

Alcoholics can develop a neurological disorder called Wernicke-Korsakoff syndrome, which can result in a loss of neurons in some parts of the brain. This syndrome also causes memory problems, confusion, paralysis of the eyes, lack of muscle coordination and amnesia. It can lead to death. However, the disorder isn't caused by the alcohol itself. It's the result of a deficiency of thiamine, an essential B vitamin. Not only are severe alcoholics often malnourished, extreme alcohol consumption can interfere with the body's absorption of thiamine.

So while alcohol doesn't actually kill brain cells, it can still damage your brain if you drink in mass quantities.

We've often been told that we only use about 10 percent of our brain. Famous people such as Albert Einstein and Margaret Mead have been quoted as stating a variation of it. This myth is probably one of the most well-known myths about the brain, in part because it's been publicized in the media for what seems like forever. Where did it come from? Many sources point to an American psychologist of the early 1900s named William James, who said that "the average person rarely achieves but a small portion of his or her potential" [source: AARP]. Somehow, that was converted into only using 10 percent of our brain.

This seems really puzzling at first glance. Why would we have the biggest brain in proportion to our bodies of any animal (as discussed in the sixth myth in our list) if we didn't actually use all of it? Many people have jumped on the idea, writing books and selling products that claim to harness the power of the other 90 percent. Believers in psychic abilities such as ESP point to it as proof, saying that people with these abilities have tapped into the rest of their brains.

Here's the thing, though; it's not really true. In addition to those 100 billion neurons, the brain is also full of other types of cells that are continually in use. We can become disabled from damage to just small areas of the brain depending on where it's located, so there's no way that we could function with only 10 percent of our brain in use.

Brain scans  have shown that no matter what we're doing, our brains are always active. Some areas are more active at any one time than others, but unless we have brain damage, there is no one part of the brain that is absolutely not functioning. Here's an example. If you're sitting at a table and eating a sandwich, you're not actively using your feet. You're concentrating on bringing the sandwich to your mouth, chewing and swallowing it. But that doesn't mean that your feet aren't working -- there's still activity in them, such as blood flow, even when you're not actually moving them.

So there's no hidden, extra potential you can tap into, in terms of actual brain space

http://science.howstuffworks.com