Chapter 5: EXPERIMENTAL ABLATION Flashcards
What are lesions studies?
Experiments in which
- part of brain is damaged
- individual’s behavior is subsequently observed
What are the purposes of lesion studies?
2 of them
- discover what functions are performed by different regions of the brain
- understand how these functions are combined to accomplish particular behaviors
What are three ways you can cause brain lesions experimentally?
- RF current
- Excitotoxic lesion
- Sham lesions
What does damage by RF current consist of?
passing radio-frequency current through brain tissues
What do RF lesions destroy?
-cell bodies, axons and terminals in the region of the electrode
What does excitotoxic lesion consist of?
Lesion produced by intracerebral injection of an excitatory amino acid such as kainic acid.
What does excitotoxic lesion destroy?
cell bodies in the region where the chemical is injected.
What do researchers use Sham lesions for?
to control for the brain lesions caused solely by the damage of the surgery process.
What do sham lesions consist of ?
- placebo procedure
- do the same as other procedure but don’t activate the cell destroyer just do the first few steps that cause the inevitable brain damage.
What is the easiest method to cause temporary brain damage rather than permanent?
-inject local anesthetic muscimol: blocks action potential in the region being lesioned, stimulates GABA receptors.
What is a stereotaxic atlas?
collection of drawings of frontal sections of the brain of a particular animal with measurements that provide coordinates for stereotaxic surgery.
What is stereotaxic surgery?
brain surgery using a stereotaxic apparatus to position an electrode or cannula in a specified position of the brain.
What do we call sutures in the brain ?
Seams that are formed by several bones of the skull that grow together
What is bregma?
- called the fontanelle in babies, soft spot
- junction of the coronal and sagittal sutures
- often used as a reference point for stereotaxic brain surgery
What is a stereotaxic apparatus?
Device that permits a surgeon to position an electrode or cannula into a specific part of the brain
What is a stereotaxic apparatus used for?
- For different species (can be scale up or down to adapt)
- Used in brain surgeries and deep brain stimulation
What does deep brain stimulation consist of?
- A technique using stereotaxic surgery to implant a permanent electrode in the brain
- Used to treat chronic pain, movement disorders, epilepsy, depression, and OCD.
Why do we have to use a fixative before sectioning the brain?
- To protect from autolytic (self-dissolving) enzymes
- Preserve against decomposition by bacteria or molds.
What is the most commonly used fixative ?
Formalin
What is slicing done with?
- microtome
- cryostat
What is a microtome?
Instrument that produces very thin slices of body tissues.
What is a cryostat?
An instrument that produces very thin slices of body tissues inside a freezer chamber.
What type of staining is needed to visualize cell structures?
special histological stains
What stain do alot of researchers use?
cell-body stain
what are two examples of dyes that stain cell-bodies?
-methylene blue
-cresyl violet
They stain all cells, not just neural cells.
What is an 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.
What is a transmission electron microscope?
- A microscope that passes a focused beam of electrons through thin slices of tissue to reveal extremely small details.
- it allows to see very small anatomical structures such as synaptic vesicles and details of cell organelles.
What is a scanning electron microscope?
- provides three-dimensional information about the shape of the surface of a small object
- HOW: scans the object with a thin beam of electrons.
What does confocal laser scanning microscopy allow?
- see details inside thick sections of tissue or in upper layers of tissue in a living brain
- cells are stained with a fluorescent dye
What is a confocal laser scanning microscope?
-provides high-resolution images of various depths of thick tissue that contains fluorescent molecules by scanning the tissue with light from a laser beam.
What are researchers trying to understand by tracing efferent axons ?
- trying to understand the destination of a neural pathway
- HOW: by identifying where cells in a brain region send their axons and terminals
What method is used for tracing efferent axons?
anterograde labeling method
What does the anterograde labeling method consist of ?
- method that labels the axons and terminal buttons of neurons whose cell bodies are located in a particular region
- HOW: employs chemicals that are taken up by dendrites or cell bodies and then transported through the axons toward the terminal buttons.
What are researchers trying to understand by tracing afferent neurons?
-Discover parts of the brain involved in the “upstream” components of neural circuitry.
What does the retrograde labeling method consist of?
- labels cell bodies that give rise to terminal buttons that form synapses with cells in a particular region
- HOW: employs chemicals that are taken up by terminal buttons and carried backward through the axons toward the cell bodies
What is the goal of transneuronal tracing methods?
-to discover circuits of interconnected neurons
What do transneuronal tracing methods exactly do?
- identify a series of neurons that form serial synaptic connections with each other, either in an anterograde or retrograde direction
- they involve infecting specific neurons with weakened forms of rabies or herpes viruses.
What are the three main noninvasive methods used?
- computerized tomography (CT)
- Magnetic resonance imaging (MRI)
- Diffusion tensor imaging (DTI)
What does computerized tomography consist of?
- device that employs a computer to analyse data obtained by a scanning beam of X-rays
- produces a two-dimensional picture of a “slice” through the body
What does magnetic resonance imaging consist of?
- accurate images in interior of body
- HOW: involves the interaction between radio waves and a strong magnetic field.
What does diffusion tensor imaging consist of?
-imaging method that uses a modified MRI scanner to reveal bundles of myelinated axons in the living human brain.
