Cognitive Psychology: 7 Techniques for Studying the Brain

cognition

This post will be dealing with a more science oriented approach to psychology known as cognitive neuroscience, which is a  branch of psychology that involves intensive study of the brain as well as behaviour. The human brain is a lot more than a mass of grey goop; it is an extremely complicated organ consisting of a team of 50 billion neurons (each of which link up to 10,000 more neurons!) that work around the clock to control every thought, action, and perception we have. Your brain is responsible for literally everything you think and know about yourself and the world you live in, and is therefore the holy grail of psychology, as everything that is knowable has it’s roots in the brain. Even though we all have a brain, we are not born with an instruction manual on how to use it, or how it works. So we spend the rest of our lives letting it work on autopilot, outside our conscious control – do we control the brain, or does the brain control us?

 

In a great display of irony, scientists and neuropsychologists have dedicated a significant portion of their own brains power in order to understandhow it works. Over time this has resulted in enormous advances in technology, which allow us numerous ways of obtaining detailed information about the brain’s structure and functioning and what roles it plays in dictating human behaviour. With access to this technology we are able to find out exactly what areas of the brain are responsible for certain behaviours and actions, and also how these areas of the brain are affected in cases of disability and mental illness. Note that each piece of technology has both its strengths and limitations – at the most basic level they vary in the precision with which they identify the brain areas active when a task is performed (spatial resolution), and the time course of such activation (temporal resolution). I will now list 7 of the major techniques for studying the brain, in no particular order they are:

Single-unit recording 

This technique involves inserting a micro-electrode one 110,000th of a millimetre in diameter into the brain to study activity in single neurons. This is a very sensitive technique, since electrical charges of as little as one-millionth of a volt can be detected. This technique has it’s obvious advantages in being able to observe brain activity at a very localised level. Another advantage is that information about neuronial activity can be obtained over time periods ranging from small fractions of a second up to several hours or even days. However, the technique can only provide information about activity at the level of single neurons, so other techniques are necessary in order to assess the functional of larger cortical areas.

Event-related potentials (ERPs)

eegThe electroencephalogram (EEG) is based on recordings of electrical brain activity measured at the surface of the scalp. Very small changes in electrical activity within the brain are picked up by scalp electrodes. These changes can be shown on the screen of a cathode-ray tube using an oscilloscope. However, background brain activity sometimes clouds the impact of stimulus processing on the EEG recording. This problem can be solved by presenting the same stimulus several times. After that, the segment of EEG following each stimulus is extracted and lined up with respect to the time of stimulus onset. These EEG segments are then simply averaged together to produce a single waveform. This method produces event-related potentials (ERPs) from EEG recordings and allows neuroscientists to distinguish genuine effects of stimulation from background brain activity. ERPs have very limited spatial resolution but their temporal resolution is excellent; they can often indicate when a given process occurred to within a few milliseconds.

Positron emission tomography (PET)

PETThis technique involves the detection of positrons, which are the atomic particles emitted from some radioactive substances. Radioactively labelled water (the tracer) is injected into the body, and rapidly gathers in the brain’s blood vessels (seriously, who’s idea was this?) When part of the cortex becomes active, the labelled water moves rapidly to that place. A scanning device next measures the positrons emitted from the radioactive water. A computer then translates this information into images of the activity level in different brain regions, which looks like the brain viewed through thermal goggles. It seems dangerous to inject a radioactive substance into the body, but I have been assured that only tiny amounts of radioactivity are involved (everything is o.k in moderation, right?), and the tracer has a half-life of only 2 minutes. PET has reasonable spatial resolution, in that any active area within the brain can be located to within 5-10 millimetres. However, as with most things in life, it suffers from limitations too. For example, it has very poor temporal resolution – PET scans indicate the amount of activity in each region of the brain over a 30-60 second period, so therefore PET cannot assess the rapid changes in brain activity associated with most cognitive processes. Also, more importantly, PET scans require the patient/victim to be stabbed with a syringe full of radioactivity, which can sometimes make it difficult to administer.

Functional magnetic resonance imaging (fMRI)

fmriMagnetic resonance Imaging (MRI) is the process of using radio waves to excite atoms in the brain, which produces magnetic changes detected by a very large magnet surrounding the patient. These changes are then interpreted by a computer and turned into a very precise 3D picture. MRI scans can be obtained from numerous different angles but can only tell us about the structure of the brain rather than its functions. As cognitive neuroscientists are generally more interested in brain functions than brain structure, it is lucky that MRI technology can provide functional information in the form of functional magnetic resonance imaging (fMRI). Oxyhaemoglobin is converted into deoxyhaemoglobin when neurons consume oxygen, and deoxyhaemoglobin produces distortions in the local magnetic field. This distortion is assessed by fMRI, and provides a measure of the concentration of deoxyhaemoglobin in the blood. Technically, what is measured infMRI is known as BOLD (blood-oxygen-level-dependent contrast). Changes in the BOLD signal produced by increased neural activity take some time to occur, so the temporal resolution of fMRI is about 2 or 3 seconds. However, its spatial resolution is very good (approximately 1mm). Since the temporal and spatial resolution of fMRI are both much better than PET, fMRI has largely overshadowed PET.

Magneto-encephalography (MEG)

MEGMagneto-encephalography (MEG) involves using a superconducting quantum interference device (SQUID) to measure the magnetic fields produced by electrical brain activity. This technology is quite complex due to the size of the magnetic field created by the brain, which is extremely small relative to the earth’s magnetic field. It is also extremely expensive to use, as SQUIDS need to be kept very cool by means of liquid helium, and recordings are taken under magnetically shielded conditions. Despite this, the MEG provides very accurate measurement of brain activity, in part because the skull is virtually transparent to magnetic fields. This means that magnetic fields are minimally distorted by intervening tissue, which is a definite advantage over the electrical activity assessed by the EEG. Overall, MEG has excellent temporal resolution (at the millisecond level) and often has very good spatial resolution as well.

Transcranial magnetic stimulation (TMS)

TMSTranscranial magnetic stimulation (TMS) is a technique in which a coil is placed close to the participant’s head, and a very brief (less than 1 millisecond) but large magnetic pulse of current is run through it. This causes a short-lived magnetic field that generally, but not always, leads to inhibited processing activity in the affected area. More specifically, the magnetic field created leads to electrical stimulation of the brain. In practice, several magnetic pulses are usually administered in a fairly short period of time – this process is known as repetitive transcranial magnetic stimulation (rTMS). This technique creates a temporary ‘lesion’ so that the role of any given brain area in performing a given task can be assessed. If TMS applied to a particular brain area results in impaired task performance, it is reasonable to conclude that that brain area is necessary for the tasks performance. Therefore, the greatest advantage of TMS and rTMS over neuroimaging techniques is that it increases our confidence that a given brain area is necessary for the performance of some task. TMS allows us to manipulate or experimentally control the availability of any part of the brain for involvement in the performance of some cognitive task. In contrast, we can only establish associations or correlations between activation in various brain areas and task performance when using functional neuroimaging.

And there you have it, stay tuned for the next post on cognitive psychology!

A Collection of Zen Stories

zen enlightenment

“We gain enlightenment like the moon reflecting in the water. The moon does not get wet, nor is the water broken. Although its light is wide and great, the moon is reflected even in a puddle an inch wide. The whole moon and the whole sky are reflected in a drop of dew in the grass.”
– Dōgen Zenji

Man and His Horse

There is a story in zen circles about a man and a horse. The horse is galloping quickly, and it appears that the man on the horse is going somewhere important. Another man, standing alongside the road, shouts, “Where are you going?” and the first man replies, “I don’t know! Ask the horse!”

A Beautiful Goose

A Zen monk saw a beautiful goose fly by and he wanted to share this joy with his elder brother who was walking beside him. But at that moment, the other monk had bent down to remove a pebble from his sandle. By the time he looked up, the goose had already flown by. He asked, “What did you want me to see?” but the younger monk could only remain silent.

Zen Tea

Nan-in, a Japanese master during the Meiji era (1868-1912), received a university professor who came to inquire about Zen. Nan-in served tea. He poured his visitor’s cup full, and then kept on pouring. The professor watched the overflow until he no longer could restrain himself. “It is overfull. No more will go in!”
“Like this cup,” Nan-in said, “you are full of your own opinions and speculations. How can I show you Zen unless you first empty your cup?”

Zen Dialogue

Zen teachers train their young pupils to express themselves. Two Zen temples each had a child protégé. One child, going to obtain vegetables each morning, would meet the other on the way.
“Where are you going?” asked the one.
“I am going wherever my feet go,” the other responded.
This reply puzzled the first child who went to his teacher for help. “Tomorrow morning,” the teacher told him, “when you meet that little fellow, ask him the same question. He will give you the same answer, and then you ask him: ‘Suppose you have no feet, then where are you going?’ That will fix him.”
The children met again the following morning.
“Where are you going?” asked the first child.
“I am going wherever the wind blows,” answered the other. This again nonplussed the youngster, who took his defeat to his teacher.
“Ask him where he is going if there is no wind,” suggested the teacher.
The next day the children met a third time.
“Where are you going?” asked the first child.
“I am going to the market to buy vegetables,” the other replied.

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Zen Story: Publishing the Sutras

zen oxTetsugen, a devotee of Zen in Japan, decided to publish the sutras (teachings of Buddha), which at that time were available only in Chinese. The books were to be printed with wood blocks in an edition of seven thousand copies – a tremendous undertaking. Tetsugen began by traveling and collecting donations for this purpose. A few sympathizers would give him a hundred pieces of gold, but most of the time he received only small coins. He thanked each donor with equal gratitude.

After ten years Tetsugen had enough money to begin his task. It happened that at that time the Uji River overflowed. Famine followed. Tetsugen took the funds he had collected for the books and spent them to save others from starvation. Then he began again his work of collecting. Several years afterwards an epidemic spread over the country. Tetsugen again gave away what he had collected, to help his people. For a third time he started his work, and after twenty years his wish was fulfilled. The printing blocks which produced the first edition of sutras can be seen today in the Obaku monastery in Kyoto. The Japanese proudly tell their children that Tetsugen made three sets of sutras, and that the first two invisible sets surpass even the last.

Zen Story: The Ghost and the Beans

japanese womanA young wife fell sick and was about to die. “I love you so much,” she told her husband, “I do not want to leave you. Do not go from me to any other woman. If you do, I will return as a ghost and cause you endless trouble.” Soon the wife passed away. The husband respected her last wish for the first three months, but then he met another woman and fell in love with her. They became engaged to be married. Immediately after the engagement a ghost appeared every night to the man, blaming him for not keeping his promise. The ghost was clever too. She told him exactly what has transpired between himself and his new sweetheart. Whenever he gave his fiancee a present, the ghost would describe it in detail. She would even repeat conversations, and it so annoyed the man that he could not sleep.

Someone advised him to take his problem to a Zen master who lived close to the village. At length, in despair, the poor man went to him for help. “Your former wife became a ghost and knows everything you do,” commented the master. “Whatever you do or say, whatever you give you beloved, she knows. She must be a very wise ghost. Really you should admire such a ghost. The next time she appears, bargain with her. Tell her that she knows so much you can hide nothing from her, and that if she will answer you one question, you promise to break your engagement and remain single.”
“What is the question I must ask her?” inquired the man.
The master replied: “Take a large handful of soy beans and ask her exactly how many beans you hold in your hand. If she cannot tell you, you will know she is only a figment of your imagination and will trouble you no longer.” The next night, when the ghost appeared the man flattered her and told her that she knew everything. “Indeed,” replied the ghost, “and I know you went to see that Zen master today.”
“And since you know so much,” demanded the man, “tell me how many beans I hold in this hand!” There was no longer any ghost to answer the question.

Zen Story: The Stingy Artist

zenGessen was an artist monk. Before he would start a drawing or painting he always insisted upon being paid in advance, and his fees were high. He was known as the “Stingy Artist.” A geisha once gave him a commission for a painting. “How much can you pay?” inquired Gessen. “‘Whatever you charge,” replied the girl, “but I want you to do the work in front of me.”
So on a certain day Gessen was called by the geisha. She was holding a feast for her patron. Gessen with fine brush work did the paining. When it was completed he asked the highest sum of his time. He received his pay. Then the geisha turned to her patron saying: “All this artist wants is money. His paintings are fine but his mind is dirty; money has caused it to become muddy. Drawn by such a filthy mind, his work is not fit to exhibit. It is just about good enough for one of my petticoats.” Removing her skirt, she then asked Gessen to do another picture on the back of her petticoat. “How much will you pay?” asked Gessen.
“Oh, any amount,” answered the girl. Gessen named a fancy price, painted the picture in the manner requested, and went away. It was learned later that Gessen had these reasons for desiring money: A ravaging famine often visited his province. The rich would not help the poor, so Gessen had a secret warehouse, unknown to anyone, which he kept filled with grain, prepared for these emergencies. From his village to the National Shrine the road was in very poor condition and many travelers suffered while traversing it. He desired to build a better road. His teacher had passed away without realizing his wish to build a temple, and Gessen wished to complete this temple for him. After Gessen had accomplished his three wishes he threw away his brushes and artist’s materials and, retiring to the mountains, never painted again.

The Stone Soup

stone soupThere are many variations of the story of the stone soup, but all of them involve a traveler visiting a town suffering from a famine. The town residents try to discourage the traveler from staying the night, fearing that he is looking for food. They tell him right away that they don’t haveany food at all, and that he should look elsewhere. The traveler explains with a smile that he doesn’t need any food, and that he was actually planning on making a soup large enough to feed the whole town. The townspeople watch suspiciously as he collects firewood from the nearby forest and lays it in a neat pile on the ground. They also watch carefully as he fills his cauldron with water from the stream by the towns entrance. The traveler builds a fire and places the cauldron of water over it, watching happily as it bubbles. With great confidence he reaches into his bag and pulls out a big stone, dropping it carelessly into the pot of water. He leans close to the pot and sniffs his brew, exclaiming how delicious stone soup is. The villagers are all very interested by now and one by one they check up on the bubbling cauldron.

A man walks by with hunger written on his face and stares down into the stone soup, the traveler says how delicious the soup will be if it had a little bit of cabbage; the man says he has some and runs home, returning moments later with a cabbage, which he drops into the cauldron. Later a woman walks over to the soup, she smells the cabbage and licks her lips hungrily. The traveler tells her how delicious the soup would be if it had just a little bit of carrot; the woman proudly replies that she has carrots growing in her garden and she rushes off to collect them, when she returns she drops the carrots into the soup. Throughout the day this episode repeats itself until the soup has cabbage, carrots, onions, leek, celery, potatoes, and of course, the big stone. Eventually the traveler takes the stone out of the soup and proclaims that the stone soup is ready. Everybody helps themselves to a big serving and enjoys the soup together; they all talk about how delicious it is. Plenty of soup remained in the cauldron after the feast was over, and so the town was relieved of their famine.