Major Imaging Techniques Flashcards
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Establish a function for a brain region
Block, Mimic, Measure.
Block: is this area necessary for function?
Mimic: is this area sufficient for function?
Measure: does activity occur when and how it is predicted?
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Chemical methods
block: antagonists
mimic: agonists
measure: change
drawbacks: not specific, have slow, complex, global effects
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Electrical methods
measures redistribution of charge caused by synaptic activity and action potentials
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
electrophysiology or single-unit recordings
single-unit recordings of a neuron, or if further away the local field potential (LFP).
Advantage: very high spatial and temporal resolution. very specific (single neurons)
Disadvantages: invasive (rare clinical circumstances). location of the cell body is known, but not where the axons and dendrites are (no network or network interactions).
Timescale: fastest
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Microstimulation or intracranial stimulation
Advantage: can provide rather specifit neural perturbation
Disadvantage: stimulation is not local, including passing fibers and interneurons. Limited to animals and rare clinical circumstances
electrodes can deliver current instread of just measuring (mimics).
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Optogenetics
takes advantage of channel rhodopsin, light-gated ion channels.
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Electroencephalography (EEG)
Advantage: good temporal resolution. Good for state effects (e.g. arousal, sleep stages). Noninvasive. Inexpensive, fast, and easy recording procedures.
Disadvantages: low spatial resolution. Not very specific for information processing or cognitive function
- Can only use it for outer edges of lobes
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Transcranial magnetic stimulation (TMS)
Advantage: just like lesions, but transient and noninvasive. With single shot, can get some temporal resolution.
Disadvantages: Mostly can do only superficial cortex. Not very focused; stimulates other areas nearby and above the target area. Even for some superficial brain regions, is too uncomfortable. Some safety issues, particularly for repetitive TMS (rTMS)
Timescale: seconds
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Event-related potentials (ERP)
Advantage: very high temporal resolution. Noninvasive. Inexpensive, fast, and easy recording procedures.
Disadvantage: low spatial resolution. Difficult to distangle multicomponent activity. Activity may be associated with but not essential for the task
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Magnetoencephalography (MEG)
Advantage: very high temporal resolution (as good as EEG). Better localization than ERPs. Noninvasive.
Disadvantage: Picks up mainly only sulcal activity. Limited spatial localization. Expensive. Recordings very susceptible to interfering noise. Activity may be associated with but not essential for task
Timescale: Miliseconds
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Positron Emission tomography (PET)
measures isotopes (can measure anything you make radioactive). In this case, neurotransmitiers.
mesures from whole brain
Advantage: Good spatial resolution (3D). Identifies network of regions associated with task.
Disadvantage: no temporal resolution. Cannot do event-related designs (block design only). Need cyclotron. Need to inject radioactive molecules. Indirect measurement of neuronal activity. Activated areas may be associated with but not essential for the task
Timescale: Minutes
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
Functional magnetic resonance imaging (fMRI)
Advantage: high spatial resolution. Temporal resolution better than PET. Can do event-related designs. Identifies network of regions associated with task. Noninvasive.
Disadvantage: limited spatial resolution. Low temporal resolution (few seconds). indirect measurment of neuronal activity. activated areas may be associated with but not essential for the task
What are the advantages, disadvantages, and resolution (spatial and temporal) for each technique
The blood oxygenation level-dependent (BOLD)
Neural activity increases local energy demand (oxygen usage). Brain responds with increased blood supply (over-response) which results in a net decrease in magnetic interference. (a.k.a. oxygenated blood “shows up” better than deoxygenated blood, which interferes with the signal) BOLD response is sluggish; does not peak until 4-6 sec after a stimulus
Magnetic resonance imaging (MRI)
- indirect measure of brain activity
- can measure whole brain
- BOLD responce is slow
