Ablation: Removal of brain tissue.

Adoption Study: A technique for studying the roles of heredity and environment by comparing the similarity of adopted children to their biological parents with their similarity to their adoptive parents.

Antisense RNA: A technology that temporarily disables a targeted gene or reduces its effectiveness.

Autoradiography: A technique for identifying brain structures involved in an activity; it involves injecting a radioactive substance (such as 2-DG) that will be absorbed most by the more active neurons, which then will show up on an X-ray image.

Computed Tomography (CT): An imaging technique that produces a series of X-rays taken from different angles; these are combined by a computer into a three-dimensional image of the brain or another part of the body.

Concordance Rate: The proportion of cases in which a pair of related individuals shares a characteristic.

Correlation: The degree to which two variables are related, such as the IQs of siblings; it is measured by the correlation coefficient, a statistic that varies between the values of 0.0 and ±1.0.

Correlational Study: A study in which the researcher does not control an independent variable but determines whether two variables are related to each other.

Deception: In research, failing to tell the participants the exact purpose of the research or what will happen during the study or actively misinforming them.

Diffusion Tensor Imaging (DTI): A variant of MRI that measures movement of water molecules to image brain pathways and quantify their quality.

Electroencephalogram (EEG): A measure of brain activity recorded from two electrodes on the scalp over the area of interest and connected to an electronic amplifier; this detects the combined electrical activity of all the neurons between the two electrodes.

Event-Related Potential: An EEG technique for measuring the brain’s responses to brief stimulation; it involves presenting a stimulus repeatedly and averaging the EEG over all the presentations to cancel out random activity, leaving the electrical activity associated with the stimulus.

Experimental Study: A study in which the researcher manipulates an independent variable and observes its effect on one or more dependent variables.

Fabrication: In research, deliberately falsifying, altering, or manipulating data or results.

Family Study: A technique for studying the roles of heredity and environment by assessing how strongly a characteristic is shared among relatives.

Functional Magnetic Resonance Imaging (fMRI): A brain-imaging procedure that measures brain activation by detecting increases in blood flow and oxygen usage in active neural structures.

Gene Therapy: Treatment of a disorder by gene manipulation.

Genetic Engineering: Manipulation of an organism’s genes or their functioning.

Gene Transfer: Insertion of a gene from another organism into a recipient’s cells, usually within a virus.

Golgi Stain: A staining method that randomly stains about 5% of neurons, which makes them stand out individually.

Immunocytochemistry: A procedure for labeling cellular components such as receptors, neurotransmitters, or enzymes by using a dye attached to an antibody designed to attach the component.

Informed Consent: Voluntary agreement to participate in a study after receiving full information about any risks, discomfort, or other adverse effects that might occur.

In Situ Hybridization: A procedure for locating gene activity; involves constructing strands of complementary DNA that will dock with strands of messenger RNA. The complementary DNA is radioactive, so autoradiography can be used to locate the gene activity.

Knockdown Technique: A genetic engineering technique in which a gene’s activity is reduced by interfering with its expression.

Knockout Technique: A genetic engineering technique in which a nonfunctioning gene mutation is inserted during the embryonic stage.

Lesioning: Surgical damage to neural tissue, typically using electrical current, heat, a chemical, or a microscalpel. Lesions occur naturally as a result of trauma, disease, or developmental error.

Magnetic Resonance Imaging (MRI): An imaging technique that involves measuring the radio-frequency waves emitted by hydrogen atoms when they are subjected to a strong magnetic field. Because different structures have different concentrations of hydrogen atoms, the waves can be used to form a detailed image of the brain.

Messenger Ribonucleic Acid (mRNA): A copy of one strand of DNA that moves out of the nucleus to direct protein construction.

Myelin Stain: A staining method that stains the fatty insulation on axons, thus identifying neural pathways.

Nissl Stain: A staining method that stains cell bodies.

Plagiarism: The theft of or use without permission of another’s work or ideas.

Positron Emission Tomography (PET): An imaging technique that reveals function. It 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 makes an image that is color coded to show the relative amounts of activity.

Scanning Electron Microscope: A microscope that forms a three-dimensional image of up to 2 to 3 million times magnification by capturing electrons emitted by tissue when it is bombarded by a beam of electrons.

Stereotaxic Instrument: A device used for the precise positioning in the brain of an electrode or other device, such as a cannula.

Theory: A system of statements that integrate and interpret diverse observations to explain some phenomenon.

Transcranial Magnetic Stimulation (TMS): A noninvasive stimulation technique that uses a magnetic coil to induce a voltage in brain tissue.

Transmission Electron Microscope: A magnification system that passes a beam of electrons through a thin slice of tissue onto a detector plate that connects to a computer monitor, forming an image magnified up to 50 million times.

Twin Studies: A technique for studying the roles of heredity and environment by assessing how similar twins are in some characteristic; their similarity is compared with that of nontwin siblings, or the similarity between identical twins is compared with the similarity between fraternal twins.