Methods Flashcards
Functional Neurosurgery
Intervention to alter/restore brain function
Deep brain stimulation DBS
Applying small amounts of electricity through surgically implanted electrodes
Little metal piece inserted into brain, patient can generate a pulse with a handheld device
Pharmacology
Use of drugs, agonists and antagonists
Drug MUST cross BBB to work
Agonists
Mimic neurotransmitters and have similar structure
Antagonists
Bind to receptors and block or dampen neurotransmission
Transcranial magnetic stimulation
Application of magnetic fields to the brain through an instrument held near the scalp
Allows for double dissociations
Transcranial direct current stimulation tDCS
Low voltage electrical current created non-invasively across the scalp
Hypothesized to potentiate neurons near the anodal electrode and hyperpolarize neurons near the cathodal electrode
Knockout mice
Specific genes (such as fear gene) are eliminated from lab rat population
Computed Tomography
X-ray radiation absorption correlates with tissue density
E.g. Bones look white because they absorb a lot
Magnetic Resonance Imaging MRI
Huge magnet, orients protons and releases energy afterwards
Diffusion Tensor Imaging DTI
Uses MRI scanner that allows white matter pathways to be imaged
Water diffuses anistropically
Single-cell recording
Microelectrode inserted into neuron and action potentials are recorded
Pros: excellent spatial and temporal resolution
Cons: Poor spatial coverage, not necessarily representative of all neurons, not done to healthy people, not causal
Multiunit recordings
Similar to single-cell recording, but an array of multiple electrodes is inserted in brain such that many cells can be recorded at once, makes a noise when neurons fire
Raster plots
Graphs that show timing of action potentials
Time on x axis number of trials on y axis
Electroencephalography EEG
Net of electrodes placed around head
Shows patterns in brain state and frequency of oscillations is measured
Event-related potential ERP
EEG analysis using a time-lock that allows scientists to look into events of interest
EEG and ERP Pros and Cons
P: Temporal resolution
C: Poor spatial localization and resolution, challenge in localizing source
Electrocorticography ECoG
Electrodes placed directly in/on brain (like EEG but invasive)
More accurate with spatial localization than ERP
Magnetoencephalography MEG
Synaptic activity produces small magnetic field
Average many trials
Same temporal resolution as ERP
More accurate spatial localization
Uses SQUID array
Positron Emission Tomography PET
Measures local variations in cerebral blood flow CBF
Detects gamma rays emitted indirectly by a tracer’
One prominent tracer is FDG
Concentrations of FDG indicate relative metabolic activity
Need to inject a radioactive tracer to use
More blood flow = more radiation
fMRI
Uses MRI imaging to focus on the magnetic properties of weakly magnetic deoxygenated hemoglobin
Altered blood flow alters the RF signal from active brain regions
As blood flow increases, so does oxygen concentration in the blood
Active neurons discard oxygen and become more magnetic,
increasing the BOLD signal (Blood Oxygen-Level Dependent).
P: Spatial res
C: Temporal res
BOLD signal
A technique that is commonly used for measuring brain activity in humans using magnetic resonance imaging (MRI). Blood supplies oxygen to brain cells. When these cells are active, there is an increase in blood flow and blood oxygen in the surrounding area.
