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Science of the Mind | SP r = √SSxSSy |
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Science of the Mind | SP r = √SSxSSy |
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Observed Problems:
How We Decide 1/5 - Jonah Lehrer
How We Decide 2/5 - Jonah Lehrer
How We Decide 3/5 - Jonah Lehrer
How We Decide 4/5 - Jonah Lehrer
How We Decide. by Jonah Lehrer. Houghton Mifflin Harcourt, 2009. These are summaries of some major points in the book. Experiments that demonstrate the science and stories that illustrate the science are in the book. READ THE BOOK!
The frontal lobes are considered our emotional control center and home to our personality. There is no other part of the brain where lesions can cause such a wide variety of symptoms (Kolb & Wishaw, 1990). The frontal lobes are involved in motor function, problem solving, spontaneity, memory, language, initiation, judgement, impulse control, and social and sexual behavior. The frontal lobes are extremely vulnerable to injury due to their location at the front of the cranium, proximity to the sphenoid wing and their large size. studies have shown that the frontal area is the most common region of injury following mild to moderate traumatic brain injury (Levin et al., 1987).
There are important asymmetrical differences in the frontal lobes. The left frontal lobe is involved in controlling language related movement, whereas the right frontal lobe plays a role in non-verbal abilities. Some researchers emphasize that this rule is not absolute and that with many people, both lobes are involved in nearly all behavior.
Disturbance of motor function is typically characterized by loss of fine movements and strength of the arms, hands and fingers (Kuypers, 1981). Complex chains of motor movement also seem to be controlled by the frontal lobes (Leonard et al., 1988). Patients with frontal lobe damage exhibit little spontaneous facial expression, which points to the role of the frontal lobes in facial expression (Kolb & Milner, 1981). Broca's Aphasia, or difficulty in speaking, has been associated with frontal damage by Brown (1972).
An interesting phenomenon of frontal lobe damage is the insignificant effect it can have on traditional IQ testing. Researchers believe that this may have to do with IQ tests typically assessing convergent rather than divergent thinking. Frontal lobe damage seems to have an impact on divergent thinking, or flexibility and problem solving ability. There is also evidence showing lingering interference with attention and memory even after good recovery from a TBI (Stuss et al., 1985).
Another area often associated with frontal damage is that of "behavioral sponteneity." Kolb & Milner (1981) found that individual with frontal damage displayed fewer spontaneous facial movements, spoke fewer words (left frontal lesions) or excessively (right frontal lesions).
One of the most common characteristics of frontal lobe damage is difficulty in interpreting feedback from the environment. Perseverating on a response (Milner, 1964), risk taking, and non-compliance with rules (Miller, 1985), and impaired associated learning (using external cues to help guide behavior) (Drewe, 1975) are a few examples of this type of deficit.
The frontal lobes are also thought to play a part in our spatial orientation, including our body's orientation in space (Semmes et al., 1963).
One of the most common effects of frontal damage can be a dramatic change in social behavior. A person's personality can undergo significant changes after an injury to the frontal lobes, especially when both lobes are involved. There are some differences in the left versus right frontal lobes in this area. Left frontal damage usually manifests as pseudodepression and right frontal damage as pseudopsychopathic (Blumer and Benson, 1975).
Some common tests for frontal lobe function are: Wisconsin Card Sorting (response inhibition); Finger Tapping (motor skills); Token Test (language skills).
Centre for Neuro Skills
When you plan your day, think about your upcoming vacation, or defend an idea convincingly, your two frontal lobes are very active. In addition to to reasoning and planning, your frontal lobes modulate your emotions and are involved in what makes up your personality. Your voluntary body movements are also initiated in the frontal lobes, but in the portion farther back. Lastly, a small region in your left frontal lobe is very important, because it lets you convert your thoughts into words.
Henri Laborit (1914-1995)
A lot of what we know about the physiology of happiness came from some rather unhappy business indeed. Recall the plight of poor Phineas Gage. Phineas was a good man by any century‘s standards, diligent and popular with everyone he worked with on the railroads of Vermont. But in the fall of 1848, while laying dynamite along the tracks, Gage accidentally struck and detonated an exposed pack with his tamping iron. The metal rod quite literally flew through his head.in through his left cheek, behind his eye, and out through the back of his skull.
Miraculously, Gage was walking and talking again shortly after the accident. But it quickly became clear that he wasn‘t the man he used to be. .He is . . . irreverent, indulging at times in the grossest profanity, said his employer, who refused to rehire him because this once-happy and well-liked man suddenly was manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires . . . obstinate, yet capricious and vacillating. . . . his mind was radically changed, so that his friends and acquaintances said he was no longer Gage.
Today‘s technology has allowed researchers to carefully reconstruct the preserved remains of Gage‘s skull and determine that the part of his brain that was obliterated by the tamping iron was the prefrontal cortex. Therein lies one anatomical component of happiness in the brain. But ‘happiness‘ is not a word scientists use often in their work. UAB neurobiologist Robin Lester, Ph.D., says that researchers are more likely to use the term ‘positive affect‘ to discuss the neurobiology of positive emotions. Happiness is lumped into that concept, he says, because it allows you to discuss things like safety from danger. For an animal, at least, happiness is being safe from danger. Lester says that being in what‘s called a highly motivated state is also positive affect. People who are risk-takers or highly motivated tend to be happier in general.
Neurobiologists are using modern tools such as functional imaging to study how brain injuries, as well as powerful negative emotions such as fear ,stimulate different parts of the brain. In this way they have slowly mapped out much of the brain‘s geography of happiness. What they‘ve learned from these studies is that happiness doesn‘t seem to have a clearly defined neurobiological home. Like everything else about human nature, happiness has complex roots.
Your Happiness HousekeepersWhen you hear a funny joke, your laughter response is generated in the prefrontal cortex of your brain. People who have undergone prefrontal lobotomies experience drastic alterations of their personalities, as did Phineas Gage. But this is one of the more conscious coordinates of happiness in the head. At its fundamental level, says Lester, happiness, like all other emotional states.is under the brain.s subconscious control. That‘s because emotional states are important for regulating behaviors in general, he explains. Anyone who‘s been sleepless with worry or too heartsick to eat knows that a certain amount of positive affect is necessary to make sure you properly eat, drink, sleep, have sex, and do all the other things humans need to do to survive, thrive, and propagate our species. The brain uses, and depends on, our emotions to make sure of it.
One crucial part of that process is the hypothalamus, a tiny, subcortical structure shaped not unlike a very melty ice-cream cone. Its bottom tip rests on the chickpea-sized pituitary gland, which it uses to link the nervous system with the endocrine system. The main job of the hypothalamus is to maintain what neurobiologists call the .set point..a unique and fixed status quo in each person.s body. It registers stimuli from inside the body, such as your glucose level, and outside the body, such as whether or not you.re currently being chased by a bear. Everything from blood pressure to body weight falls under the purview of the hypothalamus; it controls hunger, thirst, sexual drive, and circadian rhythms. .The hypothalamus integrates internal and external information,. says Lester, .so that it can send out appropriate signals to control your response to a specific situation..
The hypothalamus is part of the limbic system of the brain.an old system, says Lester, responsible for emotional processing and learning. A variety of brain structures play a role in this system, including the amygdala, or .fear center,. and the nucleus accumbens, or .pleasure center.. .There is some conscious control of the limbic system,. he says, .but it can do a lot of stuff automatically.. Take smiling, for example.a universal expression of happiness that crosses all cultures. .In patients undergoing brain surgery,. says Lester, .researchers have shown that by stimulating the nucleus accumbens, you can induce a patient to smile. In fact, you can also induce feelings of mirth, so the person will actually feel happy.. The activities of these basic, often subconscious processes ultimately register in the personality center of the prefrontal cortex as emotions.
Currents of JoyBut it.s not just the physical structures along the happiness pathway that are important. It.s also what travels between them.the chemical foot patrol that turns up one response and dampens down another. These chemical signals, called neurotransmitters.including serotonin, dopamine, and norepinephrine.are required at certain levels in the brain to maintain your happiness status quo. Too little of them can result in clinical depression.inappropriate unhappiness, one could say. Other signals, such as endorphins and enkephalins, the body.s natural analgesics, contribute to positive affect through the mood elevation we get after exercise. Together, these signals create a current that runs from our most primordial brain structures to our highest cerebral echelons, and its ebb and flow seems to have a profound effect on our emotional highs and lows.
n addition to the pleasure center, the fear center, and the homeostasis mechanisms in the brain, Lester notes that the brain.s .reward system,. a concentration of neurons that transmit dopamine, is an important trail on the happiness map. .The reward system is essential for driving motivated behaviors that are responsible for the survival of self and species,. he says. .These are really fundamental behaviors, so this is a very powerful system. And you.ll find that in people who are extroverted, or risk-takers, this system is kind of tuned up. They have a more active dopaminergic system..
Unhappiness Has Its Uses
Dopamine and its fellow neurotransmitters also provide an excellent illustration of why happiness, homeostatically speaking, is a thing best meted out judiciously. That‘s to say, says Lester, that from a biologist‘s point of view, it‘s not necessarily a good thing to be happy all the time. This is because happy brains don‘t necessarily function in the most practical ways for long-term well-being. In fact, we tend to really make a mess of making the right predictions about what will give us happiness in the longterm, he says.
.The classic example is shopping for a new television. You get excited about the TV with the best picture. So you don‘t take into account whether it will integrate with your other entertainment devices, whether it‘s out of the price range you can afford, and other things. So if you buy the TV that makes you happiest in the store, you end up not being happy. The same model could be applied to other areas of life, from choosing a career to choosing a mate.
Happiness is only one emotion we need to make sure we do the right things, says Lester. If you‘re confronted by a tiger, it‘s not a good time to react by feeling happy. While that example is extreme, the concept holds true for more mundane experiences. In fact, studies suggest that unhappiness or mild depression might serve a social purpose. Let‘s say you‘re moving through positions of increasing responsibility at work, says Lester. You might get to a point where it‘s too much. That level is different for each person, so depression lowering your level of happiness might be your brain‘s way of indicating that you‘re not at the level that‘s best for you.
Slaves to Biology?Useful or not, it goes without saying that unhappiness is unpleasant, and there are times when our conscious minds want to chase those blues away. Luckily, says Lester, our emotions are not complete captives to the brain‘s structures and signaling mechanisms. Happiness depends on information that is constantly cycling throughout cortical and subcortical, conscious and subconscious brain systems, he says. Psychologists will tell you that through cognitive behavioral therapies you can reset some of this yourself.
If the level of a transmitter affects your state of mind, it stands to reason that you can use your mind to affect the level of the transmitter. A very basic example is hunger: The hypothalamus samples things like your glucose level, and that helps tell you whether you‘re hungry or not, says Lester. You‘re not going to be happy if you‘re very hungry, but then you might consciously engage the reward pathway by saying, Well, I‘m looking forward to getting something to eat later on, which will elevate your mood.
Lester notes that it can be hard to separate the psychologic from the physiologic components that drive happiness. But we do know from behavioral therapies that if you change your behaviors, you can change your brain chemistry, that is, within limits.
These processes, though they can operate below conscious level, are not entirely subconscious. That probably gives us an advantage over lower species, because we have more cortical control over our reward pathway. An animal is probably critically dependent on its brain‘s reward system to generate the appropriate response for a given situation. But we get more of a chance to think about it. Lester pauses a moment, and smiles. Maybe that‘s good, and maybe it‘s not.
Seeking the Aerial ViewThough neurobiologists know many of the locations on the brain‘s happiness map, they are still working to develop a comprehensive understanding of the human emotional landscape. We‘re talking about only a few small groups of neurons that contain the transmitters, but they transmit throughout the brain, Lester says. The big question we‘re left with is how all these systems integrate to control emotional behavior. There‘s a lot we can still learn about that.
Lester says the genetic basis of happiness is an especially rich area for ongoing study. It‘s pretty intriguing, the question of why some people say they‘re happier than others. We‘re all very different in that respect. And it has to be some combination of our experience and our genetics. With advances in genetic understanding and human imaging, Lester believes a clearer sense of the physiology that influences emotion will form. As these technologies improve, we‘ll better understand this happiness thing.
Yount
When the cortex has received and processed a sensory stimulus indicating a reward, it sends a signal announcing this reward to a particular part of the midbrain, the ventral tegmental area (VTA), whose activity then increases. The VTA then releases dopamine not only into the nucleus accumbens, but also into the septum, the amygdala, and the prefrontal cortex.
The nucleus accumbens then activates the individual‘s motor functions, while the prefrontal cortex focuses his or her attention.
These regions are connected by what is called the pleasure or reward bundle. In neuroanatomical terms, this bundle is part of the medial forebrain bundle (MFB), whose activation leads to the repetition of the gratifying action to strengthen the associated pathways in the brain.
First described by James Olds and Peter Milner in the early 1960s, the MFB is a bundle of axons that originates in the reticular formation, crosses the ventral tegmental area, passes through the lateral hypothalamus, and continues into the nucleus accumbens as well as the amygdala, the septum, and the prefrontal cortex.
The MFB is composed of ascending and descending pathways, including most of the pathways that use monoamines as a neurotransmitter. The mesocorticolimbic dopaminergic system is one of its main components.
Consequently, the reward circuit and the punishment circuit can be said to supply most of the necessary motivation for most of our behaviours.
Canadian Institutes of Health Research
Everybody smiles and laughs at some time or another. The first laughter appears at about 3.5 to 4 months of age , way before we are able to speak. The average adult laughs 17 times a day. Even monkeys and apes have some facial expressions that are similar to human smiles. But really, why do we laugh? Why are we not able to tickle ourselves? What part of the brain is responsible for laughter and humor? Why do we say some people have no sense of humor? We never go to the doctor because we feel good or because we think something is funny. Therefore, it is not a clinical problem; that is why there has not been much research done on the topic of laughter and the brain.
Although there is considerable information on the neuronal representation of speech, little is known about brain mechanisms of laughter. While many researchers have tracked the brain mechanisms of depression, fear and anger, they have ignored positive emotions and have just begun to study humor. Their investigations are shedding some light on how the brain processes humor and prompts laughter.
Take this joke for instance: How many Bryn Mawr college students does it take to change a lightbulb? Answer: None, they were all so busy studying that they didn't even notice the light was out. If you found this old joke funny, you will get some activity going on in the brain. Investigations into how humor and laughter influence the brain are leading to a clearer understanding of how positive emotions affect brain mechanisms. This in turn may lead to creative ideas for new therapies for emotion disorders and pain.
The physiological study of laughter has its own name, "gelotology". Research has shown that laughing is more than just a person's voice and movement. Laughter requires the coordination of many muscles throughout the body. Laughter also increases blood pressure and heart rate, changes breathing, reduces levels of certain neurochemicals (catecholamines, hormones) and provides a boost to the immune system . Can laughter improve health? It may be a good way for people to relax because muscle tension is reduced after laughing. Human tests have found some evidence that humorous videos and tapes can reduce feelings of pain, prevent negative stress reactions and boost the brain's biological battle against infection . More studies are needed in this field to uncover whether humor or some other component such as distraction, is the predominant factor in these results.
Researchers believe we process humor and laughter through a complex pathway of brain activity that encompasses three main brain components. In one new study, researchers used imaging equipment to photograph the brain activity of healthy volunteers while they underwent a sidesplitting assignment of reading written jokes, viewing cartoons from The New Yorker magazine as well as "The Far Side" and listening to digital recordings of laughter. Preliminary results indicate that the humor-processing pathway includes parts of the frontal lobe brain area, important for cognitive processing; the supplementary motor area, important for movement; and the nucleus accumbens, associated with pleasure . Investigations support the notion that parts of the frontal lobe are involved in humor. Subjects' brains were imaged while they listened to jokes. An area of the frontal lobe was activated only when they thought a joke was funny. A study that compared healthy individuals with people who had damage to their frontal lobes, the subjects with the damaged frontal lobes were more likely to choose a wrong punch line to written jokes and didn't laugh or smile as much at funny cartoons or jokes.
A paper published in the journal Nature has provided information about how the brain is involved with laughter. Electrical stimulation was applied at 85 discrete sites on the cortical surface of the left frontal lobe of a 16-year-old girl (A.K.) undergoing monitoring by intracranial subdural electrodes to locate the focus of chronic intractable seizures. The patient's seizures were never accompanied by laughter. During stimulation A.K. performed a variety of tasks such as naming of objects, reading a paragraph of text, or counting. A small area measuring about 2 cm x 2 cm was identified on the left superior frontal gyrus where stimulation consistently produced laughter. The laughter was accompanied by a sensation of merriment or mirth. Although it was evoked by stimulation on several trials, a different explanation for it was offered by the patient each time, attributing the laughter to whatever external stimulus was present. The duration and intensity of laughter increased with the level of stimulation current. At low currents only a smile was present, while at higher currents a robust contagious laughter was induced .The results suggest that electrical stimulation in the anterior part of the supplementary motor area (SMA) can elicit laughter. The observation that A.K. was able each time to invoke a stimulus context that explained the laughter suggests a close link between the motor, affective and cognitive components of laughter. Analysis suggests that smiling and laughter might involve similar mechanisms which are closely related phenomena on a single continuum. This shows that the areas of the brain that caused laughter in A.K. are part of a larger circuit involving several different brain areas. The movement of face muscles for a smile would be the motor part of humor and the understanding of the joke would be the cognitive, thinking part of humor.
Damage to any one part of the brain may affect one's overall ability to process humor. Peter Derks, a professor of psychology, conducted his research with a group of scientists at NASA-Langley in Hampton. Using a sophisticated electroencephalogram (EEG), they measured the brain activity of 10 people following exposure to a humorous stimuli. How quickly our brain recognizes the incongruity that deals with most humor and attaches an abstract meaning to it determines whether we laugh . However, different people find different jokes funny. That can be due to a number of factors, including differences in personality, intelligence, mental state and probably mood. But, according to Derks, the majority of people recognize when a situation is meant to be humorous. In a series of experiments, he noticed that several patients recovering from brain injuries could not distinguish between something that was funny and something that was not. As follow-up to his latest research, Derks has been trying to identify the connection between mood and responsiveness to humor. Derks had originally thought that mood played a vital role in whether a person responded to humor. Someone feeling happy would be more inclined to laugh at a joke than someone feeling sad. However, early findings suggest that there is no apparent consistent pattern among people. Individuals seem to respond to humor in different ways that can't be predicted from their mood . Derks traced the pattern of brainwave activity in subjects responding to humorous material. Subjects were attached to an EEG and their brain activity was measured when they laughed. In each case, the brain produced a regular electrical pattern. Within four-tenths of a second of exposure to something potentially funny, an electrical wave moved through the cerebral cortex, the largest part of the brain. If the wave took a negative charge, laughter resulted. If it maintained a positive charge, no response was given. During the experiment, researchers observed the following specific activities. The left side of the cortex (the layer of cells that covers the entire surface of the forebrain) analyzed the words and structure of the joke. The brain's large frontal lobe, which is involved in social emotional responses, became very active. The right hemisphere of the cortex carried out the intellectual analysis required to get the joke. Brainwave activity then spread to the sensory processing area of the occipital lobe (the area on the back of the head that contains the cells that process visual signals). Stimulation of the motor sections evoked physical responses to the joke . Emotional responses appear to be confined to specific areas of the brain, while laughter seems to be produced via a circuit that runs through many regions of the brain. Damage to any of these regions can impair one's sense of humor. Derks's work only provides a basic picture of how the brain responds to humor. More comprehensive findings could be made if an EEG, Positron Emission Tomography (PET) scanner and Magnetic Resonance Imaging (MRI) were used on a subject simultaneously. However, only a few laboratories in the world are equipped for such testing.
Dr. Shibata of the University of Rochester School of Medicine said our neurons get tickled when we hear a joke. The brain's 'funny bone' is located at the right frontal lobe just above the right eye and appears critical to our ability to recognize a joke. Dr. Shibata gave his patients MRI scans to measure brain activity. Dr. Shibata tried to find out what part of the brain is particularly active while telling the punch line of a joke as opposed to the rest of the joke and funny cartoons in comparison to parts of the cartoon that's not funny. The jokes "tickled" the frontal lobes. The scans also showed activity in the nucleus accumbens. Activity in the nucleus accumbens is likely related to our feeling of mirth after hearing a good joke and our "addiction" to humor . While his research was about humor, the results could help lead to answers and solutions about depression. Parts of the brain that are active during humor are actually abnormal in patients with depression. Eventually brain scans might be used to assess patients with depression and other mood disorders. The research may also explain why some stroke victims lose their sense of humor or suffer other personality changes. The same part of the brain is also associated with social and emotional judgement and planning.
Laughter is a complex human behavior that occurs unconsciously. While we can consciously inhibit it, we don't consciously produce laughter. That is why it is very hard to laugh on command or to fake laughter. We know that many sensations and thoughts trigger laughter, and that it activates many parts of the body. While we know that certain parts of the brain are responsible for certain functions and tasks, it seems that laughter cannot be traced to one specific area of the brain. Furthermore the relation between laughter and humor is not understood, despite their evident connection.
Humor plays a powerful and unique role in human life with wide-ranging effects on many aspects of functioning. Humor can tie people together, help us cope with daily stress, and have a positive effect on the immune systems .Hopefully, uncovering the brain's specific response to positive stimuli like humor and laughter may lead to new therapies for depression.
Although Derks's early findings suggest that mood has no correlation to responsiveness to humor more studies are needed. I know when I am sad, I do not find many things funny. However, when I am in a good mood I laugh much more readily. Although the purpose of humor and laughter is still largely unknown, having a sense of humor is a key part of our personalities and it can play a powerful role in balancing negative emotions, such as fear and anxiety. If we can increase the humor processing abilities of depressed people then we may be able to combat some forms of depression. Even though there have been few studies of humor's place in the brain, understanding the basis of positive emotions will likely be as helpful as understanding the negative ones.
Roth
A more precise description of humor and laughter is a 5 stage model more appropriate for neurologists and neuroscientists:
This makes the localization of humor and laughter in the brain complex. Humor and laughter is a complicated process. Each of these elements may have its own cerebral substrate.
The perception of humor is dependent on certain faculties of the brain, such as attention, working memory, mental flexibility, emotional evaluation, verbal abstraction and the feeling of positive emotions. Given these involvements, theory dictates that (at least) those regions of the brain associated with these processes should be active in the perception of humor.
Humor and laughter need a neural network in which frontal and temporal regions are involved in the perception of humor. These, in turn, would induce facial reactions and laughter mediated by dorsal brainstem regions. These reactions would be inhibited by the ventral brainstem, probably via frontal motor/premotor areas.
One of the latest publications discusses the results of fMRI research done by three different research groups. They all found the human reward system in the brain involved with humor. This system mainly uses dopamine as it.s neurotransmittor. That.s why everyone loves to laugh. The activation of this system, the mesolimbic regions represents the pleasurable component of humor.
Now, a recent fMRI study has found mesolimbic reward activation associated with humorous cartoons, providing a neurobiological link between theories of humor and hedonic processes in the brain.
More recent research found that both men and women share an extensive humor-response strategy as indicated by recruitment of similar brain regions. They also found a difference between men and women as far as brain activation in a fMRI study was concerned around humor.
Females activate the left prefrontal cortex more than males, suggesting a greater degree of executive processing and language-based decoding. Females also exhibit greater activation of mesolimbic regions, including the nucleus accumbens, implying greater reward network response and possibly less reward expectation. These results indicate sex-specific differences in neural response to humor with implications for sex-based disparities in the integration of cognition and emotion.
Dr Shock
The "laughter centre" is situated near the part of the brain controlling language. It's a funny old world. There you are carrying out vital work into chronic epilepsy. You stumble on a scientific breakthrough. And, suddenly, it's a huge joke.
That is at least part of the story of a group of scientists at the University of California medical school who say they have found the part of the brain that controls laughter. Whilst using electric currents to explore a 16-year-old girl's severe epilepsy, the team hit upon the so-called "laughter centre".
Laughter buzzBy passing the current through this region, located on the left-hand side of the brain, the girl could be made to laugh uncontrollably - even when there was nothing funnier going on than a group of men standing around in white coats.
Low voltages made her smile. As the current increased, so did her mirth. Finally, "a robust and contagious laughter was induced," the science journal Nature reported. The girl told the team: "You guys are just so funny standing around."
Stimulating other areas of the girl's brain did not produce similar results. Surgeon Dr Itzhak Fried, who led the team that made the discovery, told the BBC: "We have not seen this before in our studies." He said the girl would always link her good humour with the external stimulus present at the time.
Hilarious horse"Whatever she was doing at the time she would attribute the laughter to that activity. If she was looking at a picture of a horse, she would say the horse was so funny. "We got the impression that she was enjoying it. It was a pleasant experience for her."
But Dr Fried was uncertain if the results of his work could be repeated. "I think obviously this is a very particular clinical situation," he said. "We just tapped into perhaps one area in a very complex network. It was very close to areas that carry some speech function, so speech and laughter are very close together."
BBC News
The brain may have a "funny bone", a finding that may explain why some stroke victims lose their sense of humour. "A small part of the frontal lobes appears critical to our ability to recognise a joke," said Dean Shibata of the University of Rochester School of Medicine. "Although the purpose of humour and laughter is still largely unknown despite 2000 years of speculation, having a sense of humour is a key part of our personalities and it can play a powerful role in balancing negative emotions, such as fear," he said.
Reuters report that Shibata and colleagues released their findings at the annual meeting of the Radiological Society of North America. Their finding was based on the use of functional magnetic resonance imaging (MRI) to map activity in the brains of 13 people exposed to humour in four different tests.
"There have been few studies of humour's place in the brain, but understanding the basis of positive emotions will likely be as helpful as understanding the negative ones," he said.
"In the future, scans of brain activity might be used routinely by psychiatrists to assess patients who have mood disorders such as depression, which often is accompanied by a loss of humour," he added.
The study said the brain may help explain why people who suffer a stroke involving the lower frontal lobes of the brain have alterations of personality, including loss of their sense of humour.
The same part of the brain is also associated with social and emotional judgement and planning, the study said.
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