Studies of brain structure and functions (OLI)

Compare the two approaches (cadaver and lesion studies) and the five methods (single-unit microelectrode, EEG, PET scan, fMRI, and TMS) that scientists use to study brain structure and functions.

One problem in understanding the brain is that it is difficult to get a good picture of what is going on inside it. But a variety of empirical methods allow scientists to look at brains in action, and the means by which to study the brain have improved dramatically in recent years with the development of new neuroimaging techniques. In this section, we consider the various techniques that psychologists use to learn about the brain. Each technique has some advantages, and when we put them together, we begin to get a relatively good picture of how the brain functions and which brain structures control which activities.

Perhaps the most immediate approach to visualizing and understanding the structure of the brain is to directly analyze the brains of human cadavers. When Albert Einstein died in 1955, his brain was removed and stored for later analysis. Researcher Marian Diamond [1] later analyzed a section of the Einstein’s cortex to investigate its characteristics. Diamond was interested in the role of glia, and she hypothesized that the ratio of glial cells to neurons was an important determinant of intelligence. To test this hypothesis, she compared the ratio of glia to neurons in Einstein’s brain with the ratio in the preserved brains of 11 more “ordinary” men. However, Diamond was able to find support for only part of her research hypothesis. Although she found that Einstein’s brain had relatively more glia in all the areas she studied than did the control group, the difference was statistically significant in only one of the areas she tested. Diamond admits a limitation in her study is that she had only one Einstein to compare with 11 ordinary men.

An advantage of the cadaver approach is that the brains can be fully studied, but an obvious disadvantage is that the brains are no longer active. In other cases, however, we can study living brains. The brains of living human beings may be damaged, for instance, as a result of strokes, falls, automobile accidents, gunshots, or tumors. These damages are called lesions. In rare circumstances, brain lesions may be created intentionally through surgery, for example, to remove brain tumors or (as in split-brain patients) to reduce the effects of epilepsy. Psychologists also sometimes intentionally create lesions in animals to study the effects on their behavior. In so doing, they hope to be able to draw inferences about the likely functions of human brains from the effects of the lesions in animals.
MRI Showing Brain Stem Lesions (indicated with arrows)
Lesions allow the scientist to observe any loss of brain function that may occur. For instance, when an individual suffers a stroke, a blood clot deprives part of the brain of oxygen, killing the neurons in the area and rendering that area unable to process information. In some cases, the result of the stroke is a specific lack of ability. For instance, if the stroke influences the occipital lobe, then vision may suffer, and if the stroke influences the areas associated with language or speech, these functions will suffer. In fact, our earliest understanding of the specific areas involved in speech and language were gained by studying patients who had experienced strokes.

It is now known that a good part of our social decision-making abilities are located in the frontal lobe, and at least some of this understanding comes from lesion studies. For instance, consider the well-known case of Phineas Gage, a 25-year-old railroad worker who, as a result of an explosion in 1848, had an iron rod driven into his right cheek and out through the top of his skull, causing major damage to his frontal lobe. [2] Remarkably, Gage was able to return to work after the wounds healed, but he no longer seemed to be the same person to those who knew him. The amiable, soft-spoken Gage had become irritable, rude, irresponsible, and dishonest. Although there are questions about the interpretation of this case study, [3] it did provide early evidence that the frontal lobe is involved in personality, emotion, inhibitory control, and goal-setting abilities.
Areas in the frontal lobe of Phineas Gage were damaged when a metal rod blasted through it. Although Gage lived through the accident, his personality, emotions, and moral reasoning were influenced. The accident helped scientists understand the role of the frontal lobe in these processes.

Did I get this

Until recently, the brain was difficult to study because __________________.
  • of a lack of cadavers available for investigating brain functions 
  • nonintrusive imaging techniques to get a good picture of he structures and activities of the brain did not exist 
  • lesion studies did not allow researchers to target specific brain areas for study 
  • all of the above 
Before the invention of the computer and modern technological equipment, it was not possible to look into a living brain to see if its structures and functions worked when a specific part of the brain was stimulated.

In the past, the most immediate approach in visualizing and understanding the structure of the brain was to analyze _______________.
  • brains of human cadavers 
  • brain of a life person 
  • lesion studies 
  • damaged brains 
Studying brains of human cadavers was initially the only way to discover information about the structure of the various parts of the brain. 

An advantage of studying the brains of human cadavers is that _________ of the brain can be fully studied and a disadvantage is the brain is _________.
parts; alive OR method; functional OR functions; alive OR structures; dead
Structural characteristics and any damage to the brain can be determined by studying cadaver brains, but nothing can be determined about the functioning of the structures because the brain tissues are no longer living.

Lesion studies are used to study the ______________________.
  • healthy part of a brain to determine its structure 
  • functioning of a brain to determine its structure 
  • damaged part of a brain to determine its functioning ability 
  • damaged part of a brain to determine its structure 
Lesion studies determine the extent of damage to a part of the brain and attempt to associate the damage to a specific loss of mental or physical function.

An advantage of lesion studies is that _________________.
  • loss of brain function can be observed 
  • loss of brain structure can be observed 
  • there is no advantage of lesion studies 
  • all of the above 
Lesion studies are conducted on brains in which the tissue has been damaged, so the loss of mental or physical functioning can be associated with the location of a lesion.

The significance of the lesion study of Phineas Gage’s damaged brain is that it provided evidence that __________________.
  • the parietal lobe is involved in controlling vision 
  • the frontal lobe is involved in controling hearing 
  • the frontal lobe is involved in controlling personality traits, emotion, inhibitory control and goal-setting abilities 
  • the parietal lobe is involved in controlling personality traits, emotion and moral reasoning abilities 
The Phineas Gage case study documented his change in personality, emotions, and decision-making after his head injury in which a metal rod entered his right cheek, went penetrated the frontal lobe of his brain, and came out the top of his head. Since the injury caused the most damage to his frontal lobe, the frontal lobe was determined to control his personality, emotions, inhibitory control, and goal-setting abilities.

Noninvasive Techniques

Lesion studies are done using various neuroimaging methods that can record electrical activity in the brain, visualize blood flow and areas of brain activity in real time, provide cross-sectional images, and even provide computer-generated three-dimensional composites of the brain.

The single-unit recording method, in which a thin microelectrode is surgically inserted in or near an individual neuron, is used primarily with animals. The microelectrode records electrical responses or activity of the specific neuron. Research using this method has found, for instance, that specific neurons, known as feature detectors, in the visual cortex detect movement, lines, edges, and even faces. [1]

A less invasive electrical method that is used on humans is called the electroencephalograph (EEG). The EEG is an instrument that records the electrical activity produced by the brain’s neurons through the use of electrodes placed on the surface of the research participant’s head. An EEG can show if a person is asleep, awake, or anesthetized because the brain wave patterns are known to differ during each state. EEGs can also track the waves that are produced when a person is reading, writing, and speaking and are useful for understanding brain abnormalities, such as epilepsy. A particular advantage of EEG is that the participant can move around while the recordings are being taken, which is useful when measuring brain activity in children who often have difficulty keeping still. Furthermore, by following electrical impulses across the surface of the brain, researchers can observe changes over very short time periods (microseconds).

A participant in an EEG study has a number of electrodes placed around the head, which allows the researcher to study the activity of the person’s brain. The patterns of electrical activity vary depending on the participant’s current state (e.g., whether he or she is sleeping or awake) and on the tasks the person is engaging in.
A Participant in an EEG Study
EEG Instrument that Records Electrical Currents from a Brain
Electroencephalograph, an Instrument That Records Electrical Currents from a Brain

Although the EEG can provide information about the general patterns of electrical activity within the brain, and although the EEG allows the researcher to see these changes quickly as they occur in real time, the electrodes must be placed on the surface of the skull, and each electrode measures brain waves from large areas of the brain. As a result, EEGs do not provide a very clear picture of the structure of the brain.

But other methods exist to provide more specific brain images. The positron emission tomography (PET) scan is an invasive imaging technique that provides color-coded images of brain activity by tracking the brain’s use of a radioactively tagged compound, such as glucose, oxygen, or a drug that has been injected into a person’s bloodstream. The person lies in a PET scanner and performs a mental task, such as recalling a list of words or solving an arithmetic problem, while the PET scanner tracks the amounts of radioactive substance that causes metabolic changes in different brain regions as they are stimulated by a person’s activity. A computer analyzes the data, producing color-coded images of the brain’s activity. A PET scan can determine levels of activity when a person is given a task that requires hearing, seeing, speaking, or thinking.

Positron Emission Tomography (PET scan) machine
Positron Emission Tomography (PET Scan) Machine

PET scan of a healthy brain
PET Scan of a Healthy Brain

Functional magnetic resonance imaging (fMRI) is a type of brain scan that uses a magnetic field to create images of brain activity in each brain area. The patient lies on a bed in a large cylindrical structure containing a very strong magnet. Neurons that are firing use more oxygen than neurons that are not firing, and the need for oxygen increases blood flow to the area. The fMRI detects the amount of blood flow in each brain region and thus is an indicator of neural activity.
fMRI Machine
fMRI Machine
fMRI of a Healthy Brain (Left) and a Schizophrenic Brain
fMRI of a Healthy Brain (Left) and a Schizophrenic Brain

Very clear and detailed pictures of brain structures can be produced via fMRI. Often, the images take the form of cross-sectional “slices” that are obtained as the magnetic field is passed across the brain. The images of these slices are taken repeatedly and are superimposed on images of the brain structure itself to show how activity changes in different brain structures over time. When the research participant is asked to engage in tasks (e.g., playing a game with another person), the images can show which parts of the brain are associated with which types of tasks. Another advantage of the fMRI is that is it noninvasive. The research participant simply enters the machine and the scans begin.

Although the scanners are expensive, the advantages of fMRI are substantial, and the machines are now available in many university and hospital settings. fMRI is now the most commonly used method of learning about brain structure.
The fMRI creates images of brain structure and activity. In this image the red and yellow areas represent increased blood flow and thus increased activity. From your knowledge of brain structure, can you guess what this person is doing?
fMRI Brain Image with Color Activity Scale

Did I get this

A noninvasive neuroimaging technique that produces very clear and detailed images of the structures and activities in the brain in response to magnetic fields is called _________________.
PET OR single-unit mictoelectrode OR fMRI OR EEG
The fMRI is the most commonly used brain imaging method because it is noninvasive and produces very clear and detailed images of brain structures and activities.

An invasive imaging technique that provides color-coded images of brain activity by tracking the brain’s use of a radioactively tagged compound, such as glucose, oxygen, or a drug, is called:
PET OR single-unit mictoelectrode OR fMRI OR EEG
The PET scan produces color-coded images of brain activity by tracking the brain’s use of a radioactively tagged compound, such as glucose, oxygen, or a drug, that has been injected into a participant’s bloodstream.

A thin probe is implanted in the brain to study the response of a specific neuron. Viewing the brain using this technique is called _______________.
PET OR single-unit mictoelectrode OR fMRI OR EEG
The single-unit microelectrode technique provides information on activity of a single neuron in the brain of an animal.

A technique that records the electrical activity produced by the brain’s neurons through the use of electrodes placed on the surface of the head is called _____________.
PET OR single-unit mictoelectrode OR fMRI OR EEG
The electrocephalograph, or EEG, provides information about the general patterns of and changes in electrical activity.

Transcranial Magnetic Stimulation

A new approach that is being more frequently implemented to understand brain function, transcranial magnetic stimulation (TMS), may turn out to be the most useful of all. TMS is a procedure in which magnetic pulses are applied to the brain of living persons with the goal of temporarily and safely deactivating a small brain region. In TMS studies, the research participant is first scanned in an fMRI machine to determine the exact location of the brain area to be tested. Then the electrical stimulation is provided to the brain before or while the participant works on a cognitive task, and the effects of the stimulation on performance are assessed. If the participant’s ability to perform the task is influenced by the presence of the stimulation, then the researchers can conclude that this particular area of the brain is important to carrying out the task.
Transcranial Magnetic Stimulation (TMS) Equipment
The primary advantage of TMS is that it allows the researcher to draw causal conclusions about the influence of brain structures on thoughts, feelings, and behaviors. When the TMS pulses are applied, the brain region becomes less active, and this deactivation is expected to influence the research participant’s responses. Current research has used TMS to study the brain areas responsible for emotion and cognition and their roles in how people perceive intention and approach moral reasoning. [1] [2] [3] TMS is also used as a treatment for a variety of conditions, including migraine, Parkinson disease, and major depressive disorder.

Did I get this

A psychologist wants to determine which area of the brain is activated by mental imagery. She wants to view brain activity while each participant is thinking about the mental images of the tragic events of 9/11 when the Twin Towers were attacked. What brain imaging technique would she most likely use to view the brain activity?
PET OR single-unit mictoelectrode OR TMS OR EEG OR lesion studies
The PET scan measures the amount of glucose in various parts of the brain. An active part of the brain uses more glucose than inactive parts of the brain. The PET scan measurements of the glucose levels produce images in varying colors; Active areas of the brain produce a range of colors from blue, green, yellow, orange, and red depending on the degree of activity. Areas of low activity or inactivity black or dark blue.

Robert thinks he might have a sleep disorder because he feels tired when he wakes up in the morning. A doctor at a sleep clinic recommends that Robert undergo several sleep tests, including one that records his brain’s electrical activity while he is sleeping. These recordings will be compared to recordings of normal sleep patterns. Which brain technique will be used to record Robert’s brain activity?
PET OR single-unit mictoelectrode OR TMS OR EEG OR fMRI
The EEG is the brain imaging method that records the rhythmic electrical patterns throughout Robert’s sleep.

Transcranial magnetic stimulation (TMS) is a useful technique that _________________.
  • uses shock treatments to the brain
  • provides relief of pain in patients with Alzheimer's disease
  • uses magnetic pulses to areas of the brain to relieve symptoms of Parkinson's disease
  • uses magnetic pulses to areas of the brain to activate lesions
TMS is a useful technique that uses magnetic pulses to areas of the brain to relieve symptoms of Parkinson’s disease. TMS is also useful in treating conditions such as migraine headaches and depression.

Research Focus: Cyber-ostracism

Neuroimaging techniques have important implications for understanding human behavior, including people's responses to others. Naomi Eisenberger and her colleagues tested the hypothesis that people who were excluded by others would report emotional distress and that images of their brains would show they experienced pain in the same part of the brain where physical pain is normally experienced. The experiment involved 13 participants. Each was placed into an fMRI brain imaging machine and told that he or she would be playing a computer cyberball game with two other players who were also in fMRI machines (the two opponents did not actually exist, and their responses were controlled by the computer).

Each participant was measured under three different conditions. In the first part of the experiment, the participants were told that due to technical difficulties, the link to the other two scanners could not yet be made, and until the problem was fixed, they could not engage in, but only watch, the game play. This allowed the researchers to take a baseline fMRI reading. Then, during a second inclusion scan, the participants played the game, supposedly with two other players. During this time, the other players threw the ball to the participants. In the third, exclusion, scan, however, the participants initially received seven throws from the other two players but were then excluded from the game because the two players stopped throwing the ball to the participants for the remainder of the scan (45 throws).

The results of the analyses showed that activity in two areas of the frontal lobe was significantly greater during the exclusion scan than during the inclusion scan. Because these brain regions are known from prior research to be active for individuals who are experiencing physical pain, the results suggest that the physiological brain responses associated with being socially excluded by others are similar to brain responses experienced upon physical injury.

Further research [5] [6] has documented that people react to being excluded in a variety of situations with a variety of emotions and behaviors. People who feel they are excluded, and even those who observe other people being excluded, not only experience pain but feel worse about themselves and their relationships with people more generally, and they may work harder to try to restore their connections with others.


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