Chapter 5: Methods
Overview of Lecture
Central nervous system approaches
Tracing neural connections
Localizing neuron activity
Chemical/electrical stimulation
Localization techniques
Transmitters vs. receptors
mRNA
The Goals of Physiological Psychology
Identify
Neural systems that control discrete behaviors
Understand
The physiological bases of behavior
Genes
Neurons
Transmitter/peptide systems
Systems of neurons
The Stereotaxic Instrument
Allows for precise manipulation of sub-cortical structures
Instrument involves 3 dimensions
Stereotaxic Atlases
For many species: rats to humans
A Side View of the Rat Brain
Central Nervous System Approaches
Ablation
Electrolytic lesions/RF lesions
Chemical lesions
Aspiration
Knife cuts
Temporary blockade
KCl (spreading depression)
Colchicine (slows down axoplasmic transport)
Cryogenic cooling
Anatomical Techniques
Histological Techniques
Perfuse (to remove blood from brain)
Remove brain
Fix to solidify brain material (prevent autolysis)
Section brain into thin slices (50-80 microns)
Use stains to highlight selective neural elements
Myelin (Weil stain)
Cell body (cresyl violet: Nissl substance in cytoplasm)
Membrane (Golgi stain)
Defining Neural Connections
Anterograde labeling
"Forward: toward axons from cell bodies"
Inject the lectin PHA-L into a nucleus, wait several days, process brain tissue.
Use immunocytochemistry tag to label antigen
Retrograde labeling
"Backwards: from axons to cell bodies"
e.g. fluorogold is a retrograde tracer
Localizing Neuron Activation
2-deoxy-glucose (2-DG) method:
Tags relative glucose utitilization
2-DG cannot be metabolized, is trapped in cell and accumulates.
Radioactive 2-DG can be quantitated using autoradiography
c-FOS activity
Neuronal activation is associated with activation of genes in the neuron nucleus- can localize Fos within nucleus, indicates relative degree of activation
Can examine behavioral states, drug states etc.
Visualizing Structure and
Activity in a Human Brain
MRI: Magnetic Resonance Imaging
Employs a magnetic field and radio waves to excite hydrogen molecules: forms an image of tissue.
PET scan
Inject radioactive substances such as 2-DG
Radioactive molecules decay- emit positrons that can be detected
Shows regions that alter activity during mental states
e.g.. laughter is associated with a wide spread decrease in neural activity
MRI Scans: Normal Human Brain
Chemical/Electrical Stimulation Methods
Cannulae
Allow for chemical injection of
Agonists/antagonists
Toxins (e.g. kainic acid, 6-OHDA)
Allow for chemical sampling within brain (microdialysis)
Electrodes
Allow for electrical elicitation of behavior
Localization of Neurotransmitters
Neurotransmitter itself
Peptide: immunoassay
Synthesis enzymes: useful for nonpeptides
mRNA that produces the neurotransmitter
An autoradiography technique
Localization Techniques
Immunocytochemistry
Pituitary cells
Dual label for Growth Hormone (GH)
Black = GHRH
Orange = GH antigen