THE METHODS AND ETHICS OF RESEARCHCHAPTER 4

SLIDES 1-5•Science, research, and theory•Research techniques•Research ethics

Science, Research, and Theory

• Science is constantly evolving, so it is tentative.• Theory makes sense amid ambiguity.

– Theory integrates diverse observations.• Example: Amphetamines produce symptoms of schizophrenia,

and amphetamines increase activity in dopamine-releasing neurons.

– Theory generates testable hypotheses.• Example: Drugs that decrease dopamine activity will improve

functioning in schizophrenics.

◊

Science, Research, and Theory

– Theory attempts to explain the observations.• Example: Schizophrenia is caused by excess dopamine

activity.– Science’s method—empiricism—makes it self correcting.

• Example: Further research showed the dopamine theory is incomplete, so researchers are pursuing additional causes.

◊

Science, Research, and TheoryExperimental Research

– The experimenter manipulates an independent variable to see if there is an effect on the dependent variable.

• Example: The experimenter induces temporary impairment in the frontal lobes to see if it increases aggression in a laboratory simulation.

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

• Examples: Subjects are screened; distracting stimuli are eliminated; subjects are cautioned to avoid stimulants.

The experimenter can conclude that changes in the independent variable caused the changes in the independent variable.

Science, Research, and Theory

Correlational research The researcher determines whether two variables change together,

but does not manipulate either of them. Example: Relating criminal behavior to frontal lobe deficits.

Correlational studies cannot determine whether there is a cause and effect relationship.

Nevertheless, correlational studies provide valuable knowledge and are an indispensible tool in research.

◊

Research Techniques

• Neuronal Staining and Imaging Techniques– The Golgi stain method randomly stains about 5% of neurons,

making them visible against the background of neural “chaos”.

– Myelin stains identify neural pathways.– Nissl stains identify cell bodies of neurons.

◊

Golgi, Nissl, and Myelin StainsFigure 4.3

Research Techniques

– The fluorogold method determines neural destinations.• Injected fluorogold is taken up by terminals of

neurons and transported through the axons to the cell bodies.

• The fluorogold will flouresce—radiate light—revealing which areas receive input from the injected area.

• Example: Fluorogold injected into the superior colliculi will show up in the retina of the eye.

◊

Research Techniques• Techniques That Reveal Function:

– In autoradiography, uptake of a radioactive substance reveals which neurons are active during a specific behavior.

• Example: Identification of visual pathways with radioactive 2-DG

• Example: Use of radioactive naloxone to identify opiate receptors

– Immunocytochemistry uses antibodies attached to a dye to identify cellular components.

• Example: Mouritsen determined cryptochromes were present at night in the retinas of night-migrating birds.

Research Techniques– In situ hybridization uses radioactive complementary

DNA, which docks with messenger RNA, to locate gene activity.

• Example: Mouritsen focused on the CRY2 cryptochrome (rather than CRY1) because it was constructed outside the retina.

Figure 4.6 In situ hybridization

Research TechniquesLight microscopes:

allow researchers to see cell bodies, dendrites, axons, and large organelles in neurons;

have limited capability due to the nature of light.Electron microscopes:

pass beams of electrons through a thin slice of tissue onto photographic film to produce an image;

have high resolution, magnifying objects up to 250,000 times; can reveal objects in 3-D (scanning electron microscope).

Newer microscopes can use thicker tissue samples. Confocal laser scanning microscope Two-photon microscope

Scanning Electron MicrographFigure 4.7

Research Techniques• EEG or electroencephalogram:

– records the combined activity from many neurons by using multiple electrodes;

– has good temporal resolution but poor spatial resolution;– is best used to detect changes in arousal.

• Evoked potential measurement:– uses a computer to average the EEG over several stimulus

presentations;– cancels out the “noise” of the brain’s other activity, leaving only

the unique response to the stimulus.

◊

EEG and Evoked PotentialsFigures 4.8b, 4.9

Evoked potential to a novel toneEEG during waking and sleep