Copyright © 2008 Pearson Allyn & Bacon Inc.1 Chapter 5 Methods and Strategies of Research This...

Copyright © 2008 Pearson Allyn & Bacon Inc.1

Chapter 5

Methods and Strategies of Research

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• Chapter 5 Outline

• Experimental Ablation

• Recording and Stimulating Neural Activity

• Neurochemical Methods

• Genetic Methods



• Evaluating the behavioral effects of brain damage

• Experimental ablation (one of the oldest techniques in neuroscience)• The _____________________________of a portion of the brain of a laboratory

animal; presumably, thefunctions that can no longer be performed arethe ones the region previously controlled.

• Lesion study• A synonym for experimental ablation.

• Lesions __________________caused by strokes or other impairments to the CNS, and they provide an experimental platform for developing treatments.



• Producing brain lesions

• Excitotoxic lesion• A brain lesion produced by intracerebral injection

of an __________________, such as kainic acid.(Kainic acid stimulate glutamate receptors)

• ____________lesion• A placebo procedure that duplicates all the

steps of producing a brain lesion except for theone that actually causes the brain damage.


RF lesions


Excitotoxic Lesion



• Stereotaxic surgery

• Stereotaxic surgery• Brain surgery using a stereotaxic apparatus to

__________an electrode or cannula in a __________position of the brain.

• Bregma• The junction of the sagittal and coronal sutures of the

skull, often used as a ___________________for stereotaxic brain surgery.



• The stereotaxic atlas

• Stereotaxic atlas• A collection of drawings of sections of the brain of a

particular animal with measurements that provide ________________for the stereotaxic surgery.



• The stereotaxic apparatus

• Stereotaxic apparatus• A device that permits a surgeon to position an

electrode or cannula into a specific part of the brain.

• Steretaxic surgery methods developed first with animals are used with human subjects to treat some disorders.

• Parkinson’s disease

• Epilepsy



• Histological Methods

• Fixation and sectioning

• Fixative• A chemical such as formalin; used to prepare and

_____________ body tissue.

• Formalin• The aqueous solution of formaldehyde gas; the most

commonly used tissue fixative.• Halts autolysis (self dissolving)• Hardens soft tissue• Kills microorganisms



• Fixation and sectioning

• Microtome• An instrument that produces very ___________of

body tissue.

• 1 to 80 micrometer thick (1-millionth of a meter).

• Different ____________ are needed to make different cellular structures visible for light or electron microscopy.


Cresyl violet stain



• Electron microscopy (electron beam)

• ________________em is used for magnification above 1500 x (the limit for light microscopy)

• ______________ electron microscope• A microscope that provides three-dimensional

information about the shape of the surface of a small object.


• Tracing Neural Connections

• Tracing efferent axons• (VMH neurons do not connect to muscles directly,

but the pathway of CNS connections can be traced)

• Anterograde labeling method• A histological method that labels the axons and terminal

buttons of neurons whose cell bodies are located in a particular region.

• PHA-L• Phaseolus vulgaris leukoagglutinin; a protein derived

from kidney beans and used as an anterograde tracer; taken up by ____________and carried to the ___________________.



• Tracing efferent axons

• Immunocytochemical method• A histological method that uses ________antibodies or antibodies bound with a dye molecule to

indicate the presence of particular proteins of peptides.


VMH neurons project to the periaqueductal gray matter (PGA).



• 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. The chemical is carried from the _________________________________.

• Fluorogold• A dye that serves as a retrograde label that is taken up

by the terminal buttons and then carried back to the cell bodies.

• (Medial amygdala provides input to VMH)



• Tracing afferent axons

• Anterograde and retrograde methods label just a single link in a chain of neurons.

• _______________ methods may trace several links in the chain, and help establish a wiring diagram.

• Pseudorabies virus• A weakened form of a pig virus; used for transneuronal

tracing which labels a series of neurons that are interconnected synaptically.

• The virus ___________________________ in the chain. This method permits anterograde and retrograde directions.


• Study of the Living Human Brain

• Computerized tomography (CT)• The use of a device that employs a computer to

analyze data obtained by a scanning beam of X-rays

to produce a _________________________________________________________________________________.


Damaged area from a stroke


• Study of the Living Human Brain

• Magnetic resonance imaging (MRI)• A technique whereby the interior of the body can be

accurately imaged; involves the interaction between _______________________________________.



• Recordings with microelectrodes

• 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.



• Recording with macroelectrodes

• Macroelectrode• An electrode used to record the electrical activity of

_____________________in a particular region of the brain; much larger than a ______________.

• Electroencephalogram (EEG)• An electrical brain potential recorded by placing

electrodes on or in the scalp.



• Magnetoencephalography• A procedure that detects groups of ________

activated neurons by means of the magnetic field induced by their electrical activity.

• This procedure uses an array of superconducting quantum interference devices, or ______________.


• Recording the Brain’s Metabolic and Synaptic Activity

• 2-deoxyglucose (2-DG)• A sugar that enters cells along with glucose but is not

metabolized. _______ rates of metabolic activity are revealed by the increased up take of 2-DG.

• 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.


High level of activity in the hypothalamus


• 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 (_____)• The use of a device that reveals the localization of a

radioactive tracer in a living brain.

• Functional MRI (______)• A modification of the MRI procedure that permits the

measurement of regional metabolism in the brain.


FOS stain indicates the neurons activated during copulation (rat forebrain).


Rate of up take of 2-DG.

• Functional MRI scans have higher ____________ than PET scans, and can be acquired at a faster rate.

• Thus they reveal more detailed information than PET scans.



MaleFemale

Judgments of rhyming words


• Measuring the Brain’s Secretions

• Microdialysis• A procedure for analyzing chemicals present in the

interstitial fluid through a small piece of tubing madeof a semipermeable membrane that is implanted inthe brain.

A technique used to measure secretions of ____________________________________.

• In humans fetal dopaminergic neurons have been ___________ in the basal ganglia of some Parkinson’s patients.

• The transplant greated diminished the symptoms of Parkinson’s disease.



More dopamine secreted after the implant.


Chemicals are infused to stimulate the brain.


• Behavioral Effects of Electrical Stimulation

• Transcranial magnetic stimulation (TMS)• Stimulation of the cerebral cortex by means of magnetic

fields produced by passing pulses of electricity through a coil of wire placed next to the skull; interferes with the functions of the brain region that is stimulated.

• TMS has been used to disrupt the activity of some over active brain centers associated with depression.


• Neurochemical Methods

• Organophosphate insecticides• Human exposure to insecticides that contain

acetylcholinesterase inhibitors (acetylcholine agonists) could cause intense, bizarre dreams and walking hallucination.

• The insecticide directly activated the neural circuits responsible for dreaming.

• Neurochemical methods can be used to determine the location of an enormous variety of substances in the brain. These methods can be used to localize neurotransmitters themselves, or the enzymes that produce them.


Rat forebrain terminal buttons that secrete vasopressin.


Choline acetyltransferase in the pons


• Genetic Methods

• Targeted mutations• A mutated gene )also called a __________________

produced in the laboratory and inserted into the chromosomes of mice; fails to produce a functional protein.

• Antisense oligonucleotide• A modified strand of RNA or DNA that binds with a

specific molecule of messenger RNA and prevents it from producing it particular protein.

• These methods have the potential to reduce the likelihood of some individual developing inherited disorders or some addictions.

Copyright © 2008 Pearson Allyn & Bacon Inc.1 Chapter 5 Methods and Strategies of Research This...

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