Ch5 - Methods and Strategies of Research Flashcards
Types of brain lesions
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)
Stereotaxic surgery
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
Stereotaxic apparatus
Device used in brain surgeries & deep brain stimulation to implant electrode or cannula
Histological Methods
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
Tracing neural connections
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
Transneuronal tracing methods
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
Noninvasive methods to study structure of living human brain
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
Ways to record neural activity
electrical activity, magnetic fields induced by neural activity, metabolic activity of regions
EEG
electroencephalograms/polygraph - timeline of electrical activity of whole brain (macroelectrodes - vs microelectrodes (recording single neurons)
Magnetoencephalography
Detects groups of synchronously activated neurons by the magnetic field induced using array of superconducting quantum interference devices (SQUIDs)
Ways to record regional metabolic activity
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
Functional imaging
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)
Stimulating neural activity
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
Transcranial magnetic stimulation
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
Optogenetic methods
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)