CHAPTER 4

The Methods and Ethics of Research

Science, Research, and Theory

Research Techniques

Research Ethics Science, research,  and theory

A theory integrates and interprets diverse observations in an attempt to explain some phenomenon.

A theory explains existing facts, but it also generates hypotheses that guide further research.

An experiment is a study in which the researcher manipulates a condition (the independent variable) that is expected to produce a change in the subject’s behavior (the dependent variable).

The experimenter also eliminates extraneous variables that might influence the behavior, or equates them across subjects.

In a correlational study the researcher does not control an independent variable, but observes whether two variables are related to each other.

Variables can be potentially confounded with each other so that their effects cannot be separated.

Conclusions cannot be drawn about cause and effect from a correlational study.

Research techniques

The Golgi stain method randomly stains about 5% of neurons, placing them in relief against the background of seeming neural confusion

The Italian anatomist Camillo Golgi developed this technique in 1875, and shortly after his Spanish contemporary Santiago Ramón y Cajal used it to discover that neurons are separate cells.

Myelin stains are taken up by the fatty myelin that wraps and insulates axons; the stain thus identifies neural pathways

Nissl stains do the opposite; they identify cell bodies of neurons.

Autoradiography makes neurons stand out visibly just as staining does, but it also reveals which neurons are active, and this information can be correlated with the behavior the animal engaged in.

In this procedure the animal is injected with a substance that has been made radioactive, such as a type of sugar called 2-deoxyglucose (2-DG).

Active neurons take up more glucose, and because 2-DG is similar to glucose, the neurons involved in the activity become radioactively “labeled.”

Immunocytochemistry uses antibodies attached to a dye to identify cellular components such as receptors, neurotransmitters, or enzymes.

The technique takes advantage of the fact that antibodies, which attack foreign intruders in the body, can be custom designed to be specific to any cellular component.

The dye, which is usually fluorescent, makes the antibodies’ targets visible when the tissue is removed and examined under a microscope.

In situ hybridization involves constructing strands of complementary DNA which will dock with strands of messenger RNA.

Genes control the production of proteins; the instructions for protein production are carried from the nucleus into the cytoplasm of a cell by messenger ribonucleic acid (RNA), which is a copy of one strand of the gene’s DNA.

When we locate specific messenger RNA we know that the gene is active in that place, this is done by in situ hybridization.

With the development of the light microscope investigators were able to see the gross details of neurons: cell bodies, dendrites, axons, and the largest organelles.

But the capability of the light microscope is limited.

The electron microscope works by passing a beam of electrons through a thin slice of tissue onto a photographic film; different parts of the tissue block or pass electrons to different degrees, so the electrons produce an image of the object on the film.

The electron’s microscope’s high resolution allows us to see details like the synaptic vesicles in an axon terminal.

The electroencephalogram (EEG, or brain waves) is recorded from two electrodes on the scalp over the area of interest, which are connected to an electronic amplifier; it detects the combined electrical activity of all the neurons between the two electrodes.

Usually the researcher applies a number of electrodes and monitors activity in multiple brain areas at the same time.

The temporal (time) resolution of the EEG is one of its best features.

It can distinguish events only 1 millisecond apart in time, so it can track the brain’s responses to rapidly changing events.

Its spatial resolution, or ability to detect precisely where in the brain the signal is coming from, is poor.

This problem can be alleviated somewhat by applying electrodes directly to the brain, which removes the interference of the skull.

By combining electroencephalography with the computer the research can average the EEG over several presentations of the stimulus to produce an evoked potential.

Averaging over many trials cancels out the ongoing “noise” of the brain’s other activity, leaving only the unique response to the stimulus.

When the area of interest is below the surface, the researcher must use probes that can penetrate deep into the brain. Two important aids make this task feasible.

The first is a map of the brain called a stereotaxic atlas.

A large number of brains are sliced into very thin vertical sections; drawings are prepared that show the (average) location of brain structures on each section.

A stereotaxic instrument is a device used for the precise positioning in the brain of an electrode or other device.

Microelectrodes can be fashioned with tips so fine that they can be placed inside the neurons themselves.

Instead of an electrode, the stereotaxic instrument can be used to insert a small-diameter tube called a cannula for injecting chemicals.

With this, the researcher can simulate the effects of a neurotransmitter or block a transmitter’s effects at the synapse.

Historically one of the most profitable avenues of brain research has been the study of patients who have sustained brain damage.

Although these “natural experiments” have been extremely valuable to neuroscientists, they also have major disadvantages; most important, the damage doesn’t coincide neatly with the functional area.

The removal of brain tissue is called ablation.

Ablation can be done with a scalpel, but aspiration is a more precise technique, and it allows access to deeper structures.

The skull is opened and a fine-tipped glass micropipette connected to a vacuum pump is used to suck out neural tissue.

Lesions, or damage to neural tissue, can be produced by electrical current, heat, or injection of a neurotoxin (using a stereotaxic instrument), or by using a knife or fine wire to sever connections between areas.

Usually, lesioning is preferred in place of ablation because the damage can be more precisely controlled.

Computed tomography scanning (CT), produces a series of X rays taken from different angles.

A computer combines the series of two-dimensional horizontal cross sections, or “slices” so the researcher can scan though them as if they are a three-dimensional image of the entire organ.

Magnetic resonance imaging (MRI) works by measuring the radio-frequency waves emitted by the hydrogen atoms when they are subjected to a strong magnetic field.

Positron emission tomography (PET) involves injecting a radioactive substance into the bloodstream, which is taken up by parts of the brain according to how active they are. 

The scanner captures the positrons emitted by the radioactive substance to form an image that is color coded to show the relative amounts of activity.

Functional magnetic resonance imaging (fMRI) measures brain activation by detecting the increase in oxygen levels in active neural structures.

A family study determines how strongly a characteristic is shared among relatives.

People who have similar genes have often share a similar environment, so the effects of heredity are confounded with the effects of environment.

Correlation is the degree of relationship between two variables, measured on a scale between 0.0 and ± 1.0 (the correlation coefficient).

The strength of the relationship is indicated by the absolute value – how close the correlation is to either 1.0 or -1.0.

A high positive correlation means that when one variable is high the other tends to be high as well, and vice versa.

A negative value indicates the opposite tendency – when one value is high the other tends to be low – not that the relationship is weaker.

Adoption studies compare adopted children’s similarity to their biological parents with their similarity to their adoptive parents.

Twin studies assess how similar twins are in some characteristic.

Their similarity is then compared with that of non-twin siblings, or the similarity between identical twins is compared with the similarity between fraternal twins

A useful measure for identifying genetic influence in disorders is the concordance rate, the frequency that relatives are alike in a characteristic.

Genetic engineering involves actual manipulation of the organism’s genes or their functioning.

In the knockout technique a nonfunctioning mutation is introduced into the isolated gene, and the altered gene is transferred into embryos.

After multiple matings, mice carrying the altered gene on both chromosomes are selected for study.

The antisense RNA procedure blocks messenger RNA’s participation in protein construction.

This is accomplished by inserting strands of complementary RNA into the animal, which dock with the gene’s messenger RNA.

The cell recognizes this newly-formed molecule as abnormal and releases an enzyme that

destroys the RNA.

In gene transfer, a gene is inserted into an animal’s cells.

To create a transgenic animal, the gene is inserted into embryos.

The gene shows up in only some of the animal’s cells, but after these animals are mated with each other the gene is integrated into all the cells, including the sperm and ova.

Plagiarism is the theft of another’s work or ideas.

Fabrication, or faking, of results is more serious than plagiarism because it introduces erroneous information into the body of scientific knowledge.

More important, fabrication in clinical research can slow therapeutic progress and endanger lives, so universities and agencies take research fraud seriously.

Informed consent means that the individual voluntarily agrees to participate after receiving information about any risks, discomfort, or other adverse effects that might occur.

Sometimes the nature of the study requires deception, either failing to tell the participants the exact purpose of the research or what will happen during the study, or actively misinforming them.

According to the American Psychological Association, deception is acceptable only when the value of the study justifies it, alternative procedures are not available, and the individuals are correctly informed afterward.

Psychological and medical research has perhaps no more important resource than the laboratory animal.

Psychologists have used animals to investigate behavior, aging, pain, stress, and cognitive functions such as learning and perception.

It may seem that the best subjects for that purpose would be humans, but animals are useful because they live in a controlled environment and have a homogeneous history of experience, as well as a briefer development and life span.

Gene therapy is the treatment of disorders by manipulating genes.

Embryonic stem cells are undifferentiated cells that have the potential for developing into any other body cell.

Extracting stem cells destroys the embryo, so right-to-life advocates oppose this use of human embryos, even though most are “extras” resulting from fertility treatment and would otherwise be discarded.