Chapter 5: Methods And Strategies Of Research Flashcards
Experimental Ablation
Removal/ destruction of portion of brain of lab animals
- functions that can no longer be performed are the ones the region previously controlled
= lesion study
Goal of Experimental Ablation
Discover what functions are performed by different regions of brain and to understand how functions are combined to accomplish particular behaviors
Produce Brain Lesions
Pass electrical current through stainless steel wire that is coated with insulated coating
Excitotoxic Lesion
Brain lesion produced by intracerebral injection of excitatory AA (ex. Kainic acid)
Sham lesion
Placebo procedure that duplicates all the steps of producing a brain lesion except one that actually causes brain damage
Muscimol
Local anesthetic into parts of brain
- stimulates GABA-R —> inactivates region of brain by inhibiting neurons located there
Optogenetics
Can be used to stimulate/ inhibit brain regions
Stereotaxic Surgery
Brain surgery using a stereotaxic apparatus to position an electrode or cannula in specified position of brain
Stereotaxis
Ability to locate objects in space
Stereotaxis Atlas
Collection of drawings of sections of brain of particular animal with measurements that provide coordinates for stereotaxic surgery
Bregma
Junction of sagital and coronal sutures of skull
- used as reference point for stereotaxic brain surgery
Stereotaxic Apparatus
Device that permits surgeon to position an electrode/ cannula into specific part of brain
- Used to treat chronic pain, movement disorders, epilepsy, depression, and OCD
Histological Methods: Fixation and Sectioning
Tissue must be preserved to prevent decomposition by baceria or molds
Fixative
Chemical used to prepare and preserve body tissue
ex. Formalin
Formalin
Aqueous solution of formaldehyde gas
Microtome
Instrument that produces very thing slices of body tissues
Cryostat
Instrument that produces very thin slices of body tissue inside freezer chamber
Staining dyes
Methylene blue
Cresyl violet
Immunocytochemical Method
Histological method that uses radioactive antibodies or antibodies bound with dye molecules to indicate presence of particular proteins of peptides
Transmission Electron Microscope
Microscope passes focused beam of electrons through thin slices of tissue to reveal extremely small details
Scanning Electron Microscope
Provides 3D info about shape of surface of small object by scanning object with thin beam of electrons
Confocal Laser Scanning Microscopy
Microscope that provides high-resolution images of various depths of thick tissue that contains fluorescent molecules by scanning the tissue with light from laser beam
Tracing Efferent Neurons
Understand destination of neural pathway
Anterograde Labeling Method
Histological method that labels axons and terminal buttons of neurons whose cell bodies are located in particular region
- employ chems that are taken up by dendrites/ cell bodies
Tracing Afferent Neurons
Circuits before structure of interest
Retrograde Labeling Method
Histological method that labels cell bodies that give rise to terminal buttons that form synapses with cells in particular region
- Employ chems that are taken up by terminal button
Computerized Tomography (CT)
Use of device that employs computer to analyze data obtained by scanning beam of X-rays to produce 2D picture of “slice” through body
Magnetic Resonance Imaging (MRI)
Technique where interior of body can be accurately imaged
- Involves interaction between radio waves and strong magnetic field - Shows “slice” of brain - Better detail than CT
Diffusion Tensor Imaging (DTI)
Imaging method that uses modified MRI scaner to reveal bundles of myelinated axons in living human brain
- Movement of water molecules in bundles of white matter - Find location of fiber bundles in living human brain
Microelectrodes
Very fine electrode, generally used to record activity of individual neurons
- Can be implanted permanently to record neural activity as animal moves
Single-Unit Recording
Recording of electrical activity of single neuron
Macroelectrodes
Electrode used to record electrical activity of large numbers of neurons in particular region of brain
Electroencephalogram
Electrical brain potential recorded by placing electrodes on scalp
Magnetoencephalography (MEG)
Procedure that detects groups of synchronously activated neurons by means of magnetic field induced by their electrical activity
- Uses an array of SQUIDs - shows changes in brain activity quickly
2-deoxyglucose (2-DG)
Sugar that enters cells along with glucose but is not metabolized
- Measures local glucose utilization in autoradiography - Measures regional metabolic activity of human brain
Autoradiography
Procedure that locates radioactive aubstances in slice of tissue
- Radiation exposes photographic emulsion or piece of film that covers tissue
- consuming radioactive 2-DG
Fos
Protein produced in nucleus of neuron in response to synaptic stimulation
- When neurons activated —> immediate early genes turned on —> particular proteins produced
Functional Imaging
Computerized method of detecting metabolic or chemical changes in particular regions of brain
Positron Emission Tomography (PET)
Functional imaging method that reveals localization of radioactive tracer in living brain
- can localize any radioactive substance taken up in human brain
Functional MRI (fMRI)
Functional imaging method that is modification of MRI procedure that permits measurement of regional metabolism in brain, usually by detecting changes in blood O2 level
- Best spatial resolution - BOLD: blood O2 level-dependent signal - HIgher resolution than PET scans
Electrical Stimulation
Passes electrical current through wire inserted into brain using stereotaxic surgery
Chemical Stimulation
Inject small amount of excitatory AA (ex. Kainic acid)
- Requires cannulas, tubes, special pumps or syringe - Activates cell bodies but not axons
Transcranial Magnetic Stimulation (TMS)
Stimulation of cerebral cortex by means of magnetic fields prodiced by passing pulses of electricity through coil of wite placed next to skull
- Interferes with functions of brain region that is stimulated - Treats symptoms of neurological and mental disorders
Optogenetic Method
Use of genetically modified virus to insert light-sensitive ion channels into membrane of particular neurons in brain
- can depolarize or hyperpolarize neurons when light of appropriate wavelength is applied - Stimulate or inhibit selected populations of neurons in specific brain region - used to study functions of particular neural circuit in brain
Immunocytochemical localization of peptide/ protein
- exposes brain tissue to antibodies
- requires specific antibody
- identify neurons producing a particular NT or neuromodulator
Immunocytochemical localization of enzyme responsible for synthesis of substance
- Useful if substance is not peptide/ protein
- Identify neurons producing a particular NT or neuromodulator
Microdialysis
Procedure for analyzing chemicals present in interstitial fluid by extracting them through small piece of tubing made of semipermeable membrane that is implanted in brain
- Dialysis - Measures NT and neuromodulators released by neurons - Wide variety of substances can be analyzed
Dialysis
Process in which substances are separated by means of an artificial membrane that is permeable to some molecules but not others
Target Mutations
- Mutation gene produced in lab and inserted into chromosomes of mices
- Alters production of functional protein
Conditional Knockouts
Animal’s genes to stop expressing a particular gene when the animal is given a particular drug
Antisense Oligonucleotides
- Modified strand of RNA or DNA that binds with a specific molecule of mRNA and prevents it from producing its protein
- Prevents production of particular protein
- Can produce changes in behavior
- Antisense
Antisense
Synthetic oligonucleotides contain sequence of bases complementary to these contained by particular gene/ molecule of mRNA
CRISPR-Cas Method
- Technique that inactivate or alters the production of proteins by inserting new genetic sequences into DNA
- Alters production of proteins thorugh changes to DNA
- Breaks both strands at target site, causing cells to repair
- Can inactivate gene, creating new gene sequence
- Can create new genetic sequence, which can be inserted into DNA
- Used to model neurodegenerative diseases caused by genetic mutation
Deep Brain Stimulation
technique using stereotaxis surgery to implant permanent electrode in brain
- used to treat chronic pain, movement disorders, epilepsy, depression, and OCD
ChR2-ion channel
blue light causes channels to depolarize and let in Na+ and Ca2+
NpHR-ion channel
yellow causes channels to hyperpolarize and let in Cl-
Genome
complete set of genes that compose the DNA of a particular species
Allele
nature of the particular sequence of base pairs of DNA that constitutes a gene
