UI PSYC 372 - Techniques to Examine the Brain

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1Listen to the audio lecture while viewing these slides1Psychology 372Physiological PsychologySteven E. Meier, Ph.D.Techniques to Examinethe Brain2Psyc 372 – Physiological PsychologyInvasive Techniques• Lesioning•Electrical•Chemical• Radio Frequency• Electrical Recording• Cannulations• Push Pull• Invivo Autoradiography•Others3Psyc 372 – Physiological PsychologyNon-Invasive Techniques•X-Ray•CT•PET• MRI and FMRI• Electro Recording (EEG)•SPECT•SQUID•Others4Psyc 372 – Physiological PsychologyThe Stereotaxic Instrument• The holder allows you to swing in all directions.• A vertical knob allows you to vary the depth of the probe.• The anterior/posterior knob allows you to go front or back. • A lateral knob allows you to go from side to side.5Psyc 372 – Physiological PsychologyAnimal Stereotaxic Instrument6Psyc 372 – Physiological PsychologyGeneral Procedure• Identify and measure the dependent measure in the organism.• Anesthetize the animal.• Open the scalp.• Drill a trephine hole (hole in the skull).• Place the animal into the stereotaxic instrument.• Use the brain atlas to see where you want to go.27Psyc 372 – Physiological PsychologyGeneral Procedure• Find specif ic bra in landm arks.• Use stereotaxic instrument to insert:a. electrodes.b. cannulas.c. other instruments.• Perfo rm the technique yo u want, or yo u can seal the material in place with a glue-like substance.• Allow the animal to recover.• Monitor the dependent measure depending on the technique used.8Psyc 372 – Physiological PsychologyTechniques You Can Use• Lesioning (Ablations)• Cannulations• Push Pull• Electro recording9Psyc 372 – Physiological PsychologyElectrical Lesioning• Lesioning destroys particular brain structures. • You then observe what happens to the animal before and after the lesioning• There are several ways to lesion.10Psyc 372 – Physiological PsychologyElectrolytic (Use DC current)• Observe the animal for the particular behavior of interest.• Insert an insulated needle into the placement point. The needle is insulated except at the tip. • Apply current and burn the tissue, which ultimately dies.• Observe the animal for changes in behavior.11Psyc 372 – Physiological PsychologyDisadvantages• The electrode leaves a tract into the brain. Thus, you are also damaging other brain tissue. • Solution: destroy the tissue from several different angles.• Apply too much current, you will deposit metal particles from the electrode. • Metal particles can irritate tissue • Can cause focal points which may result in seizures. 12Psyc 372 – Physiological PsychologyRadio Frequency Techniques.• Radio frequency coagulates tissue. (Its action resembles that of a microwave oven.)• Insert an electrode insulated except at the tip. • When energy is applied to the electrode, water molecules oscillate inside neurons. • The oscillation builds up heat and kills the cells in the area.313Psyc 372 – Physiological PsychologyAdvantages and DisadvantagesAdvantage:Avoids metal particles.Disadvantage:Still have the electrode tract.14Psyc 372 – Physiological PsychologyChemical Techniques• Most commonly used technique today.• Instead of an electrode, use a cannula or tube. • Allows you to place chemicals in place where they can kill or influence neurons. 15Psyc 372 – Physiological PsychologyNeurotoxins• 6 Hydroxydopamine (6HDA) • De stroys dopamine neurons but leaves other neurons alone.• Advantage: Allows you to only kill one type of neuron.• Kanic Acid • Destroys somas (cell bodies) of neurons, but leaves axon tracts from other neurons alone.• Advantage: Can kill neurons in one area, but does not disturb neuron tracts from other areas16Psyc 372 – Physiological PsychologyChemical Stimulation Techniques. • Are the opposite of chemical lesioning• Researcher may stimulate neurons by putting in a neurotransmitter.• May also put in agonists (analogs of neurotransmitters that behave like them).• May put in compounds with unknown effects.17Psyc 372 – Physiological PsychologyGeneral Cannulation Procedures• Make a trephine hole.• Insert cannula with stereotaxic device.• Cement in place with dental cement.• Allow animal to recover and behave normally.• Later, deliver compound by injection (usually when the animal is behaving).• Observe the animal.18Psyc 372 – Physiological PsychologyDisadvantage• Over time the area fills up with the chemical.• Solution: Use a push-pull technique.419Psyc 372 – Physiological PsychologyPush-Pull Technique• Is similar to other chemical techniques except that the cannula is a little wider and has an extra tube within the main tube. • Allows you to insert solutions• Also allows you to withdraw excess compounds or other products for analysis.20Psyc 372 – Physiological PsychologyCompoundPush-Pull Technique21Psyc 372 – Physiological PsychologyAdvantages of Push-Pull• Localizes better.• Can add dyes or radioactive labels• Can change dosages or concentrations.• Can change compounds.• Can analyze materials you withdraw if you get an effect--gives better control.• Miniaturization is improving the technique further.22Psyc 372 – Physiological PsychologyCannulations• Where you place a catheter into the circulatory system of an organism• Jugular vein (Neck)• Femoral Artery or Vein (leg)• Brachial Artery or Vein (arm)• Vena Cava (vein that fills the heart)• Aorta (artery that leaves the heart)23Psyc 372 – Physiological PsychologyAdvantages• Can put the catheter almost anywhere• It’s a good way to deliver materials in the venous system.• Some materials are inserted to get past the blood–brain barrier.• If the molecules of a drug are large, they will stay in the vascular system and not cross the blood-brain barrier. • You can do the procedure in alert animals.24Psyc 372 – Physiological PsychologyDisadvantages• Clotting occurs after some time period at the end of the catheter.• Femoral 3-10 days• Descending Aorta 3-5 weeks525Psyc 372 – Physiological PsychologyOther Similar Techniques• Can insert cannulas in the mouth.• Can insert cannulas in the stomach.• Can insert cannulas in the liver.• Can insert to withdraw spinal fluid.• Can also place catheter in the fourth ventricle, substantia nigra, space above the cerebellum, • Other locations.26Psyc 372 – Physiological


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