Methods and Strategies of Research

Chapter 5

Methods and Strategies of

Research

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Copyright © 2004 Allyn and Bacon

 Experimental Ablation

 Evaluating the Behavioral Effects of Brain Damage:

 Experimental ablation:

• The removal or destruction of a portion of the brain of a laboratory animal; presumably, the functions that can no longer be performed are the ones the region previously controlled.

 Lesion study:

• A synonym for experimental ablation.

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 Producing Brain Lesions:

 Excitotoxic lesion:

• A brain lesion produced by intracerebral injection of an excitatory amino acid, such as kainic acid.

 6-hydroxydopamine (6-HD):

• A chemical that is selectively taken up by axons and terminal buttons of noradrenergic or dopaminergic neurons and acts as a poison, damaging or killing them.

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 Producing Brain Lesions:

 Sham lesion:

• A “placebo” procedure that duplicates all of the steps of producing a brain lesion except for the one that actually causes the brain damage.

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 Stereotaxic Surgery

 Stereotaxic Surgery:

• Brain surgery using a stereotaxic apparatus to position an electrode or cannula in a specified position of the brain.

 Bregma:

• The junction of the sagittal and coronal sutures of the skull, often used as a reference point for stereotaxic brain surgery.

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 The Stereotaxic Atlas

 Stereotaxic atlas:

• A collection of drawings of sections of the brain of a particular animal with measurements that provide coordinates for the stereotaxic surgery.

 Stereotaxic apparatus:

• A device that permits a surgeon to position an electrode of cannula into a specific part of the brain.

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 Histological Methods

 Fixation and Sectioning

 Fixative:

• A chemical such as formalin; used to prepare and preserve body tissue.

 Formalin:

• The aqueous solution of formaldehyde gas; the most commonly used tissue fixative.

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 Histological Methods

 Fixation and Sectioning

 Perfusion:

• The process by which an animal’s blood is replaced by a fluid such as a saline solution or a fixative in preparing the brain for histological examination.

 Microtome:

• An instrument that produces very thin slices of body tissue.

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 Tracing Neural Connections

 Tracing Efferent Axons

 Anterograde labeling method:

• A histological method that labels the axons and terminal buttons of neurons whose cell bodies are located in a particular region.

 PHLA-L:

• Phaseolus vulgaris leukoagglutinin; a protein derived from kidney beans and used as an anterograde tracer; taken up by dendrites and cell bodies and carried to the ends the axons.

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 Tracing Efferent Axons

 Immunocytochemical method:

• A histological method that uses radioactive antibodies or antibodies bound with a dye molecule to indicate the presence of particular proteins of peptides.

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 Tracing Afferent Axons

 Retrograde labeling method:

• A histological method that labels cell bodies that give rise to the terminal buttons that form synapses with cells in a particular region.

 Fluorogold:

• A dye that serves as a retrograde label; taken up by the terminal buttons and carried back to the cell bodies.

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 Study of the Living Human Brain

 Computerized tomography (CT):

• The use of a device that employed a computer to analyze data obtained by a scanning beam of Xrays to produce a two dimensional picture of a slice through the body.

 Magnetic resonance imaging (MRI):

• A technique whereby the interior of the body can be accurately imaged; involves the interaction between radio waves and a strong magnetic field.

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 Recording and Stimulating Neural Activity

 Recording Neural Activity

 Microelectrode:

• A very fine electrode, generally used to record activity of individual neurons.

 Single unit recording:

• Recording of the electrical activity of a single neuron.

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 Recording and Stimulating Neural Activity

 Recording with Macroelectrodes

 Macroelectrode:

• An electrode used to record the electrical activity of large numbers of neurons in a particular region of the brain; much larger than a microelectrode.

 Electroencephalogram (EEG):

• An electrical brain potential recorded by placing electrodes on or in the scalp.

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 Recording the Brain’s Metabolic and Synaptic Activity

 2-deoxytglucose (2-DG):

• A sugar that enters cells along with glucose but is not metabolized.

 Autoradiography:

• A procedure that locates radioactive substances in a slice of tissue; the radiation exposes a photographic emulsion or a piece of film that covers the tissue.

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 Recording the Brain’s Metabolic and Synaptic Activity

 Fos:

• A protein produced in the nucleus of a neuron in response to synaptic stimulation.

 Positron emission tomography (PET):

• A device that reveals the localization of a radioactive tracer in a living brain.

 Functional MRI (fMRI):

• A modification of the MRI procedure that permits the measurement of regional metabolism in the brain.

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 Measuring the Brain’s Secretions

 Measuring the Brain’s Secretions

 Microdialysis:

• A procedure for analyzing chemicals present in the interstitial fluid through a small piece of tubing made of a semipermeable membrane that is implanted in the brain.

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 Stimulating Neural Activity

 Multibarreled micropipette:

• A group of micropipettes attached together, used to infuse several different substance by means of iontophoresis while recording from a single neuron.

 Microiontophroesis:

• A procedure that uses electricity to inject a chemical from a micropipette to determine the effects of the chemical on the electrical activity of a cell.

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 Neurochemical Methods

 Finding Neurons that Produce Particular

Neurochemicals

 In situ hybridization:

• The production of DNA complementary to a particular messenger RNA to detect the presence of the RNA.

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Methods and Strategies of Research

Chapter 5

Methods and Strategies of

Research

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