Methods of studying the CNS

Question 1

Nissl staining reveals

Answer 1

‘Nissl bodies’ which are dark patches in the staining where patches of RER, ribosomes and golgi are.

Question 2

What is an example of a basic Nissl dye?

Answer 2

Cresyl violet

Question 3

What is a stain used to reveal myelinated fibre tracts within the CNS?

Answer 3

Luxol fast blue and weigert staining

Question 4

What staining reveals the cytoarchitecture of the brain?

Answer 4

Nissl stains

Question 5

Reticular theory

Answer 5

The reticular theory, (Golgi) stated that the nervous system consisted of a diffuse nerve network formed by anastomosing branches of nerve processes.

Question 6

Neuron doctrine

Answer 6

The “Neuron Doctrine” (Cajal) includes descriptions of synapses and their proposed function.

Neurons are individual cells, which are not continuous to other neurons, neither anatomically nor genetically;

The neuron has three parts: dendrites, soma (cell body) and axon.

Question 7

Why is doctrine an oversimplification?

Answer 7

Doctrine is an over-simplification of how a neuron functions

In addition to synaptic contacts there are gap junctions, modulatory receptors on pre-synaptic elements, and the modulatory action of transmitters, hormones and gaseous messengers in the local environment which affect neuronal activity.

Question 8

Golgi staining

Answer 8

Impregnation of the cell cytoplasm with a silver chromate precipitate.

Question 9

Luxol blue myelin appears

Answer 9

Blue myelin, pink neuropil, purple nerve cells

Question 10

Cresyl violet RNA appears

Answer 10

Violet (Nissl bodies darkest)

Question 11

Weigert stain myelin appears

Answer 11

Darkest

Question 12

What method gives a direct measure of the activity of nerve cells?

Answer 12

Two-photon calcium imaging

Question 13

HRP staining

Answer 13

HRP is an enzyme that associates with nerve cells. DAB substrate is oxidized by horseradish peroxidase (HRP). The oxidized DAB forms a brown precipitate, at the location of the HRP, which can be visualized using light microscopy.

Question 14

What enables imaging areas of functional activity in the CNS?

Answer 14

fMRI

Question 15

What enables activity of neurons to be increased or decreased?

Answer 15

Optogenetics or chemogenetics

Question 16

CT

Answer 16

Computed tomography - combinations of multiple X-ray measurements taken from different angles to produce tomographic (cross-sectional) images (virtual “slices”) of a body, allowing the user to see inside the body without cutting.

Bone clearly white air and fat black

Question 17

MRI scanners

Answer 17

Use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body.

Contrast provided between grey and white matter

Fat underneath the skin or reservoirs of water in the body can be either white or dark in appearance, depending on the pulse sequence.

Bones often black, fat is bright

Question 18

Functional MRI (fMRI)

Answer 18

Functional magnetic resonance imaging (fMRI) measures brain activity by detecting changes associated with blood flow.

This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases

Question 19

PET

Answer 19

Positron emission tomography (PET is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption.

Question 20

MEG

Answer 20

Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.

Question 21

MEG uses

Answer 21

Research into perceptual and cognitive brain processes, localizing regions affected by pathology before surgical removal, determining the function of various parts of the brain, and neurofeedback.

Question 22

EEG vs MEG

Answer 22

Magnetic fields are less distorted than electric fields by the skull and scalp, which results in a better spatial resolution of the MEG.

EEG can detect activity both in the sulci and at the top of the cortical gyri, whereas MEG is most sensitive to activity originating in sulci.

EEG is, therefore, sensitive to activity in more brain areas, but activity that is visible in MEG can also be localized with more accuracy.

Question 23

Extracellular recordings

Answer 23

Give information about the electrical excitement and action potentials of neurons

Question 24

Single unit extracellular recordings

Answer 24

An electrode inserted into the brain detects electrical activity that is generated by the neurons adjacent to the electrode tip.

Very similar (but smaller) results to intracellular recordings

Question 25

Multi-unit extracellular recordings

Answer 25

f the electrode tip is slightly larger, then the electrode might record the activity generated by several neurons (multi-unit recording).

Question 26

Field potential

Answer 26

Electrode tip is very large, in general the activity of individual neurons cannot be distinguished but the electrode will still be able to record a field potential generated by the activity of many cells.

Question 27

Electroencephalography (EEG)

Answer 27

Non-invasive recordings of electrical activity of the brain.

Electrodes placed along the scalp

EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain.

EEG is used in clinical circumstances to determine changes in brain activity that might be useful in diagnosing brain disorders, especially epilepsy or another seizure disorder.

Question 28

What enables the imaging of neurotransmitter vesicles at a synaptic cleft?

Answer 28

EM

Question 29

What is used to study patterns of electrical activity within the entire brain?

Answer 29

EEG

Question 30

What method could specifically stain astroglia?

Answer 30

GFAP stain determine whether cells contain glial fibrillary acidic protein, a protein found in glial cells.

Immunohistochemistry

Question 31

What method gives a direct measure of the activity of large populations of nerve cells?

Answer 31

Field potentials