Ch5 - Methods and Strategies of Research

Question 1

Types of brain lesions

Answer 1

RF lesion (radio frequency, destroy cell bodies, axons, & terminals in region of electrode)

Excitotoxic lesions (injecting excitatory AA like kainic acid, destroy cell bodies in the region where chemical is injected)

need Sham lesions (placebo)

Question 2

Stereotaxic surgery

Answer 2

Stereotaxic atlas - images that correspond to frontal sections of brain at various distances
Bregma - point of reference - crossing of coronal & sagittal sutures
Stereotaxic apparatus - device used in brain surgeries & deep brain stimulation to implant electrode or cannula
To section: place neural tissue in a fixative (formalin) - slice into thin section using microtome or cytostat & stain

Question 3

Stereotaxic apparatus

Answer 3

Device used in brain surgeries & deep brain stimulation to implant electrode or cannula

Question 4

Histological Methods

Answer 4

Staining (some stains use immunocytochemical methods (ICC) to produce antibodies to any peptide or protein)

Electron microscopy (Transmission electron microscope - passes beam of electrons through tissues (enables to see very small tissues); Scanning electron microscope - provides 3D info)

Confocal laser scanning microscopy - details inside thick sections of tissue or in upper layers of tissue in a living brain- cells stained with a fluorescent dye

Question 5

Tracing neural connections

Answer 5

Efferent axons - to understand destination of neural pathway - anterograde (Ex: PHA-L is injected, taken up by dendrites & cell bodies; transported by axoplasmic flow)
Afferent - upstream - retrograde - inject flurogoid in VMH then see cell bodies in medial amygdala
Transneuronal tracing methods - to discover circuits of interconnected neurons

Question 6

Transneuronal tracing methods

Answer 6

To discover circuits of interconnected neurons

Identifies series of neurons that form serial synaptic connections with each other, either in an anterograde or retrograde direction

Involves infecting specific neurons with weakened forms of rabies or herpes viruses

Question 7

Noninvasive methods to study structure of living human brain

Answer 7

Computerized tomography (CT) - scanning beam of X-rays to produce 2D pic

Magnetic resonance imaging (MRI) - accurate images in interior of body - interactions between radio waves & strong magnetic field - white vs gray matter

Diffusion tensor imaging (DTI) - modified MRI to reveal bundles of myelinated axons in living brain

Question 8

Ways to record neural activity

Answer 8

electrical activity, magnetic fields induced by neural activity, metabolic activity of regions

Question 9

EEG

Answer 9

electroencephalograms/polygraph - timeline of electrical activity of whole brain (macroelectrodes - vs microelectrodes (recording single neurons)

Question 10

Magnetoencephalography

Answer 10

Detects groups of synchronously activated neurons by the magnetic field induced using array of superconducting quantum interference devices (SQUIDs)

Question 11

Ways to record regional metabolic activity

Answer 11

2-DG autoradiography - measurement of Fos protein - injecting radioactive 2-deoxyglucose in cells visualized by autoradiography. Immunocytochemical methods identify cells containing Fos proteins (activity in particular behaviors) - identifies recently stimulated neurons

Functional imaging - computerized method of detecting metabolic or chemical changes in brain

Question 12

Functional imaging

Answer 12

Positron emission tomography (PET) - uses a radioactive tracer (2-DG injected, taken up by more active neurons, when disintegrate emits photons on opposite directions)

Functional MRI (fMRI) - higher resolution, measures regional metabolism in the brain (blood oxygen levels)

Question 13

Stimulating neural activity

Answer 13

Electral (electrical current through wire) vs Chemical (eAA to detect oxygenation, more located, activates cell bodies but not axons) stimulation

Transcranial magnetic stimulation (non invasive)

Optogenetic methods

Question 14

Transcranial magnetic stimulation

Answer 14

passing pulses of electricity through coil of wire placed next to skull - magnetic fields activate neurons in the cortex - interferes with functions of the brain region that is stimulated - treats symptoms of mental & neurological disorders

Question 15

Optogenetic methods

Answer 15

Inject a virus that has light-sensitive ion channels → depol or hyperpolarize neurons - used to study functions of particular neural circuits

Blue light (ChR2, protein found in green algae - influx of Ca & Na - activation)

Yellow light (NpHR, found in bacterium - influx of Cl - deactivation)

Question 16

Neurochemical methods

Answer 16

PET - autoradiography? - can localize any radioactive substance taken up in the brain (2-DG)

immunocytochemistry (receptor by antibodies)

microdialysis (neurotransmitter by diffusion)

Question 17

Genetic methods

Answer 17

Twin studies, genomic studies, adoption studies, targeted mutations, antisense oligonucleotides

Question 18

Genomic studies

Answer 18

linkage studies (some diseases have marker on chromosome) - mutated genes

Question 19

Targeted mutations

Answer 19

(CRISPR-Cas methods) - inactivation, insertion, or increased expression of a gene. Changes to DNA using Cas protein to identify target sites in double strand of DNA and break both strands at that site, 2 pathways used by cells to repair: NHEJ (non-homologous end joining → mutate or deleted → gene knockout) or HDR (homology directed recombination → new sequence can be inserted)

Question 20

Antisense oligonucleotides

Answer 20

modified strands of RNA or DNA bind with messenger RNA; prevent synthesis of protein