Quiz 1 - Ways to Study the Brain

Question 1

Factors to consider when studying the brain.

Answer 1

1. Invasive: Electrodes
2. Nonivasive: MRI, electrodes on scalp
3. Resolution: How big (spatial)/how much detail in time do you want in the image (temporal)?
4. Structural: What are we looking at?
5. Functional: What parts of the brain are associated with what?

Question 2

What is phrenology?

Answer 2

Behaviors associated with physical structure of skull.

• Functions correlate to area of skull.
• Objection 1: Shape of skull does not correlate with the function of the brain.
• Objection 2: We don’t localize anything to just one region of the brain.

Question 3

What is electron microscopy?

Answer 3

Using Electrons to provide HIGH spatial resolution, but LOW temporal resolution.

Question 4

What is light microscopy?

Answer 4

Used to identify individual cells or groups of cells.

- Stains can be applied to highlight different types of cells.

Question 5

What is immunohistochemistry?

Answer 5

When antibodies are produced to react to specific proteins in or on cells.
- Raising antibodies against a particular kind of protein.

Question 6

What is In Situ Hybridization?

Answer 6

Used to Identify where certain genes are expressed by using radioactive isotopes to synthesize a complementary mRNA to the gene of interest.

Question 7

What is genetic engineering?

Answer 7

1. Gene knockout techniques: Breaking a gene to observe what sort of behaviors are lost.
2. Gene replacement techniques: Transgenic organsims (add a gene and see how it changes the behavior of an organism = knock IN)

Question 8

What is optogenetics?

Answer 8

• Control events in living tissues with millisecond resolution.
• Light-activated ion channels allow gain or loss of function in neurons.
• Light-activated GPCRs (gene protein coupled receptors) allow manipulation of metabotropic events.
• Provide insight to autism, schizophrenia, depression and drug addiction.

Question 9

What is tracing?

Answer 9

Injecting a molecule at one location in nervous system and it travels along axons or dendrites.

• Identifies connections in nervous system
• Anterograde: forward from point of interest
• Retrograde: Backwards from point of interest

Question 10

What is an intracellular unit recording?

Answer 10

An intracellular microelectrode records the membrane potential from ONE neuron as it fires. mV/mS

Question 11

What is a multiple-unit recording?

Answer 11

A small electrode records the action potentials of MANY nearby neurons.
- These are added up and plotted.

Question 12

What is an extracellular unit recording?

Answer 12

An extracellular microelectrode records the electrical disturbance that is created each time an adjacent neuron fires.

Question 13

What is an invasive EEG recording?

Answer 13

A large implanted electrode picks up general changes in electrical brain activity. The EEG signal is not related to neural firing in any obvious way.

Question 14

What is EEG?

Answer 14

Electroencephalography measures the average electrical activity of brain and can be combined with other techniques.

• Noninvasive
• Deep sleep = HIGH amplitude and LOW frequency waves.
• Aroused = LOW amplitudes and HIGH frequency waves.

Question 15

What is an ERP?

Answer 15

Event Related Potentials are EEG time-linked to sensory stimulus.

• A stimulus is repeated many times and recorded responses are averaged.
• The averaging cancels out irregular or unrelated electrical activity; leaves on those potentials that were generated by stimulus.
• Looking for mismatch negativity ie. novelties from a pattern. beep beep beep BOOP beep beep beep

Question 16

What types of lesion studies are there?

Answer 16

• Stroke or Tumor Damage: Can’t control where damage occurs, but observe behaviors.
• Stereotactic Surgery: Big metal framework, screw into skull. Lesion a particular region and see how that affects behavior (surgical).
• Chemical Lesions: Neural tissue is destroyed by the infusion of a neurotoxin.
• Reversible Lesions: TMS (Transcranial Magnetic Stimulation) used to stimulate or inhibit function and is non invasive.

Question 17

What sort of behavioral studies are there?

Answer 17

Animals: Mazes, Social behaviors, leraning, conditioning
Humans: Attention, Memory, Neuropsychological, Testing

Question 18

What types of brain imaging are there?

Answer 18

CAT(CT) and MRI = Structural

fMRI, PET, and MEG = Functional

Question 19

What is the subtraction method?

Answer 19

Trying to see what parts of the brain are active when performing a simple cognitive task. If I examine the brain when I wiggle my thumb VS doing nothing, I can find the part of the brain active during “wiggle thumb” action.

• Paired-image subtraction: AVG of moving thumb - AVG of doing nothing
• Parametric designs: Varying speeds.

Question 20

What is a CT scan?

Answer 20

Computed Axial Tomography or CT uses many x-rays at different angles.
- Image reconstructed by computer to create 3D representation of brain structure.
~ 1 mm resolution
- Not functional

Question 21

What is a PET scan?

Answer 21

Positron Emission Tomography (PET)

• Inject or inhale isotope that emits positrons.
• O15 or F18-deoxyglucose most common
• Isotope carried by blood to most metabolically active area. (Used a lot in cancer patients because tumors use a lot of energy).
• Isotopes decay giving off gamma rays.
• Can also identify location of different receptors.
• Spatial resolution ~ 3mm
• Build synthetic neurotransmitters and determine where the receptors are in the body.
• Functional

Question 22

What is an MRI?

Answer 22

Magnetic Resonance Imaging

• Strong magnetic fields align and disturb protons in brain.
• Excellent spatial resolution&raquo_space; 1mm
• Data often combined with fMRI to show structure and function.
• Structural: detects change in energy from the alignment of protons.
• Field strength: ~ 3-4 teslas

Question 23

What is an fMRI?

Answer 23

Functional MRI

• Identity changes in blood oxygenation that result from metabolic activity in brain.
• Increased activity brains more oxygenated blood.
• Increased Hb-O/Hb increases MRI signal
• Localizes function indirectly
• Spatial resolution ~ 2mm
• Deoxygenated hemoglobins are detected, determine what parts of the brain are active by measuring the blood flow changes.

Question 24

What is a MEG?

Answer 24

Magnetoencephalography

• Electrical activity of neurons generates VERY small magnetic fields
• Directly detects neuronal activity perpendicular to scalp
• Detectors have 100 - 200 channels allowing sub -mm and second resolution
• HIGH resolution and detects brain activity directly.