Chapter 5: EXPERIMENTAL ABLATION

Question 1

What are lesions studies?

Answer 1

Experiments in which

• part of brain is damaged
• individual’s behavior is subsequently observed

Question 2

What are the purposes of lesion studies?

2 of them

Answer 2

• discover what functions are performed by different regions of the brain
• understand how these functions are combined to accomplish particular behaviors

Question 3

What are three ways you can cause brain lesions experimentally?

Answer 3

• RF current
• Excitotoxic lesion
• Sham lesions

Question 4

What does damage by RF current consist of?

Answer 4

passing radio-frequency current through brain tissues

Question 5

What do RF lesions destroy?

Answer 5

-cell bodies, axons and terminals in the region of the electrode

Question 6

What does excitotoxic lesion consist of?

Answer 6

Lesion produced by intracerebral injection of an excitatory amino acid such as kainic acid.

Question 7

What does excitotoxic lesion destroy?

Answer 7

cell bodies in the region where the chemical is injected.

Question 8

What do researchers use Sham lesions for?

Answer 8

to control for the brain lesions caused solely by the damage of the surgery process.

Question 9

What do sham lesions consist of ?

Answer 9

• 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.

Question 10

What is the easiest method to cause temporary brain damage rather than permanent?

Answer 10

-inject local anesthetic muscimol: blocks action potential in the region being lesioned, stimulates GABA receptors.

Question 11

What is a stereotaxic atlas?

Answer 11

collection of drawings of frontal sections of the brain of a particular animal with measurements that provide coordinates for stereotaxic surgery.

Question 12

What is stereotaxic surgery?

Answer 12

brain surgery using a stereotaxic apparatus to position an electrode or cannula in a specified position of the brain.

Question 13

What do we call sutures in the brain ?

Answer 13

Seams that are formed by several bones of the skull that grow together

Question 14

What is bregma?

Answer 14

• called the fontanelle in babies, soft spot
• junction of the coronal and sagittal sutures
• often used as a reference point for stereotaxic brain surgery

Question 15

What is a stereotaxic apparatus?

Answer 15

Device that permits a surgeon to position an electrode or cannula into a specific part of the brain

Question 16

What is a stereotaxic apparatus used for?

Answer 16

• For different species (can be scale up or down to adapt)

- Used in brain surgeries and deep brain stimulation

Question 17

What does deep brain stimulation consist of?

Answer 17

• A technique using stereotaxic surgery to implant a permanent electrode in the brain
• Used to treat chronic pain, movement disorders, epilepsy, depression, and OCD.

Question 18

Why do we have to use a fixative before sectioning the brain?

Answer 18

• To protect from autolytic (self-dissolving) enzymes

- Preserve against decomposition by bacteria or molds.

Question 19

What is the most commonly used fixative ?

Answer 19

Formalin

Question 20

What is slicing done with?

Answer 20

• microtome

- cryostat

Question 21

What is a microtome?

Answer 21

Instrument that produces very thin slices of body tissues.

Question 22

What is a cryostat?

Answer 22

An instrument that produces very thin slices of body tissues inside a freezer chamber.

Question 23

What type of staining is needed to visualize cell structures?

Answer 23

special histological stains

Question 24

What stain do alot of researchers use?

Answer 24

cell-body stain

Question 25

what are two examples of dyes that stain cell-bodies?

Answer 25

-methylene blue -cresyl violet They stain all cells, not just neural cells.

Question 26

What is an immunocytochemical method?

Answer 26

A histological method that uses radioactive antibodies or antibodies bound with a dye molecule to indicate the presence of particular proteins of peptides.

Question 27

What is a transmission electron microscope?

Answer 27

- 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.

Question 28

What is a scanning electron microscope?

Answer 28

- provides three-dimensional information about the shape of the surface of a small object - HOW: scans the object with a thin beam of electrons.

Question 29

What does confocal laser scanning microscopy allow?

Answer 29

- see details inside thick sections of tissue or in upper layers of tissue in a living brain - cells are stained with a fluorescent dye

Question 30

What is a confocal laser scanning microscope?

Answer 30

-provides high-resolution images of various depths of thick tissue that contains fluorescent molecules by scanning the tissue with light from a laser beam.

Question 31

What are researchers trying to understand by tracing efferent axons ?

Answer 31

- trying to understand the destination of a neural pathway | - HOW: by identifying where cells in a brain region send their axons and terminals

Question 32

What method is used for tracing efferent axons?

Answer 32

anterograde labeling method

Question 33

What does the anterograde labeling method consist of ?

Answer 33

- 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.

Question 34

What are researchers trying to understand by tracing afferent neurons?

Answer 34

-Discover parts of the brain involved in the "upstream" components of neural circuitry.

Question 35

What does the retrograde labeling method consist of?

Answer 35

- 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

Question 36

What is the goal of transneuronal tracing methods?

Answer 36

-to discover circuits of interconnected neurons

Question 37

What do transneuronal tracing methods exactly do?

Answer 37

- 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.

Question 38

What are the three main noninvasive methods used?

Answer 38

- computerized tomography (CT) - Magnetic resonance imaging (MRI) - Diffusion tensor imaging (DTI)

Question 39

What does computerized tomography consist of?

Answer 39

- 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

Question 40

What does magnetic resonance imaging consist of?

Answer 40

- accurate images in interior of body | - HOW: involves the interaction between radio waves and a strong magnetic field.

Question 41

What does diffusion tensor imaging consist of?

Answer 41

-imaging method that uses a modified MRI scanner to reveal bundles of myelinated axons in the living human brain.