1-15 Research Methods (Part 2)

Front 1

Objective

Describe three techniques used to inactivate specific brain structures.

Back 1

1. Researchers may lesion (or damage) a specific brain area by using a stereotaxic instrument, a device for the precise placement of electrodes in the brain.

2. In the gene-knockout approach, researchers use biochemical methods to direct a mutation to a particular gene that is important for certain types of cells, transmitters, or receptors. Certain chemical temporarily inactivate one part of the brain or one type of synapse.

3. Transcranial magnetic stimulation, the application of an intense magnetic field to a portion of the scalp, can temporarily inactivate the neurons below the magnet.

Front 2

Objective

Identify a limitation of brain stimulation studies.

Back 2

Complex behaviors and experiences depend on many brain areas, not just one. So, artificial stimulation can produce artificial responses. For example, electrically or magnetically stimulating the primary visual areas of the brain produces reports of sparkling flashing points of light, not the sight of a face or other recognizable object. It is easier to discover which brain area is responsible for vision (for example) than to discover how it produces a meaningful pattern.

Front 3

Objective

Discuss the relationship between brain size and intelligence.

Back 3

IQ positively correlates with brain size. However, correlation does not mean causation. For example, brain size and IQ might correlate because good health and nutrition contribute to both brain growth and intellectual performance.

Front 4

Objective

Compare the brains of men and women.

Back 4

On the average, men have larger brains than women but equal IQs. IQ relates more closely to the gray matter of the brain—that is, the cell bodies—rather than total mass including white matter (the axons). Women on the average have more and deeper gyri on the surface of the cortex, especially in the frontal and parietal areas. Consequently, the surface area of the cortex is about the same in men and women. Because the surface is lined with cells (gray matter), the sexes are nearly equal in gray matter, whereas men have more white matter.

Front 5

Objective

Explain how gray and white matter relate to intelligence.

Back 5

More gray matter is associated with better performance on intellectual tests. However, the difference between human brains and chimpanzees and gorillas is more a matter of increased white matter in humans than increased gray matter. The species difference seems to imply that white matter (i.e. connectivity within the brain) is important for intelligence.

Front 6

lesion

Back 6

Damage to a brain area

Front 7

ablation

Back 7

Removal of a brain area

Front 8

stereotaxic instrument

Back 8

A device for the precise placement of electrodes in the brain

Front 9

sham lesion

Back 9

A placebo procedure that duplicates all the steps of producing a lesion, but without the electrical current (produced in a control group)

Front 10

gene-knockout approach

Back 10

Use of biochemical methods to direct a mutation to a particular gene that is important for certain types of cells, transmitters, or receptors

Front 11

transcranial magnetic stimulation

Back 11

The application of an intense magnetic field to a portion of the scalp; it can activate the neurons below the magnet