Biopsychology Notes - Chapter 5

Page 1

Experimental Ablation (108-118)

Evaluating the Behavioral Effects of Brain Damage

Producing Brain Lesions

Stereotaxic Surgery

Histological Methods

Tracing Neural Connections

Studying the Structure of the Living Human Brain

THOUGHT QUESTIONS

In the subsection "Tracing Neural Connections," [the author] wrote that "one experimental rat did copulate, but we discovered later that the lesion had missed the VMH in the animal, so we discarded the data from that animal." Should the person who looks at the stained brain sections containing the lesions and decides whether the target was destroyed or missed know which animal each of these sections belonged to? Explain.

Would you like to see an MRI of your own brain? Why or why not?

KEY CONCEPTS

Neuroscientists produce brain lesions to try to infer the functions of the damaged region from changes in the animals’ behavior.

Brain lesions may be produced in the depths of the brain by passing electrical current through an electrode placed there or by infusing an excitatory amino acid; the latter method kills cells but spares axons that pass through the region.

The behavior of animals with brain lesions must be compared with that of a control group consisting of animals with sham lesions.

A stereotaxic apparatus is used to place electrodes or cannulas in particular locations in the brain. The coordinates are obtained from a stereotaxic atlas.

The location of a lesion is verified by means of histological methods, which include fixation, slicing, staining, and examination of the tissue under a microscope.

Special histological methods have been devised to trace the afferent and efferent connections of a particular brain region.

The structure of the living human brain can be revealed through CT scans or MRI scans.

Page 2

Recording and Stimulating Neural Activity (119-125)

Recording Neural Activity

Recording the Brain's Metabolic and Synaptic Activity

Stimulating Neural Activity

THOUGHT QUESTIONS

Suppose that you had the opportunity to record an fMRI from a person (perhaps yourself) while the person was performing a behavior, thinking about something, or attending to a particular stimulus. Describe what you would have the person do.

Can you think of some ways that you could use optogenetic methods to investigate neural mechanisms involved in the control of a behavior or sensory system?

KEY CONCEPTS

The electrical activity of single neurons can be recorded with microelectrodes, and that of entire regions of the brain can be recorded with macroelectrodes. EEGs are recorded on polygraphs with data from macroelectrodes pasted on a person’s scalp.

Metabolic activity of particular parts of animals’ brains can be assessed by means of 2-DG autoradiography or by measurement of the production of Fos protein. The metabolic activity of specific regions of the human brain can be revealed through PET scans or functional MRI scans.

Neurons can be stimulated electrically, through electrodes, or chemically, by infusing dilute solutions of excitatory amino acids through cannulas.

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Neurochemical Methods (125-128)

Finding Neurons That Produce Particular Neurochemicals

Localizing Particular Receptors

Measuring Chemicals Secreted in the Brain

THOUGHT QUESTION

Using methods you learned about in this chapter so far, describe a behavior, cognitive process, or perceptual ability that you would like to study. Describe the kinds of experiments you would perform and say what kinds of information each method might provide.

KEY CONCEPTS

Immunocytochemical methods can be used to localize peptides in the brain or localize the enzymes that produce substances other than peptides.

Receptors can be localized by exposing the brain tissue to radioactive ligands and assessing the results with autoradiography or immunocytochemistry.

Microdialysis permits a researcher to measure the secretion of particular chemicals in specific regions of the brain. PET scans can be used to reveal the location of particular chemicals in the human brain.

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Genetic Methods (129-131)

Twin Studies

Adoption Studies

Genomic Studies

Targeted Mutations

Antisense Oligonucleotides

THOUGHT QUESTIONS

You have probably read news reports about studies of the genetics of human behavioral traits or seen them on television. What does it really mean when a laboratory reports the discovery of, say, a "gene for shyness"?

Most rats do not appear to like the taste of alcohol, but researchers have bred rats that will drink alcohol in large quantities. Can you think of ways to use these animals to investigate the possible role of genetic factors in susceptiblity to alcoholism?

KEY CONCEPTS

Twin studies, adoption studies, and genomic studies enable investigators to estimate the role of hereditary factors in a particular physiological characteristic or behavior.

Targeted mutations are artificially produced mutations that interfere with the action of one or more genes, which enables investigators to study the effects of the lack of a particular gene product.

Genes that cause the production of foreign proteins or increase production of native proteins can be inserted into the genome of strains of animals, and antisense oligonucleotides can be used to block the production of particular proteins.

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Research Methods Discussed in This Chapter

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Resources