Video Module 4: Neuroimaging Flashcards
cognitive neuroscience and methods
a branch of neuroscience aimed at understanding how our brain structure is related to brain function
- Relies on naturally occurring brain damage from accidents, injuries, surgeries, and disease
brain lesions
areas of damaged tissue in the brain
- show no brain activity
- help us study brains by showing us which regions of the brain are implicated in disordered behaviour
computed tomography (CT)
a neuroimaging method for capturing static pictures of the brain that uses x-rays
- visualizes tissues and bony structures in the brain
- better for bony structures
magnetic resonance imaging (MRI)
a neuroimaging method for capturing static pictures of the brain that involves producing a strong magnetic field that causes protons in tissues to move
- better for soft tissue
static vs. functional imaging techniques
Static techniques:
- do not reveal anything about function
- useful for identifying damage and relative size of brain regions
- excellent spatial resolution
- no temporal resolution
Functional techniques:
- reveal areas of the brain with increased activity
- use the subtraction method
- varying spatial resolution
- temporal resolution
positron emission tomography (PET)
a functional imaging technique that relies on injecting a radioactive isotope into the bloodstream and measuring the relative metabolic activity in the brain (blood flow) by tracking the concentration of that isotope
- medium spatial resolution (5-10 mm^3)
- medium temporal resolution
functional magnetic resonance imaging (fMRI)
a functional imaging technique that relies on magnets to measure the relative volume of oxygenated blood in different areas of the brain
- no injections
- expensive
- requires patient to remain still
- good spatial resolution (~3mm^3)
- medium temporal resolution
electrical encephalography (EEG)
a functional imaging technique that relies on measuring the change in voltage across the scalp
- requires subjects to wear an electrode cap
- relies on cells sending action potentials across the brain
- poor spatial resolution
- excellent temporal resolution
—very effective for time-locked studies
event related potential (ERP)
the average electrical response to a particular stimulus, taken from the results of hundreds of EEG trials
single cell recording
a function imaging technique that relies on placing an electrical probe inside of a single neuron to record its firing rate in response to different stimuli
- very invasive; not often done with human subjects
- excellent temporal resolution
- excellent spatial resolution
- has the best spatial and temporal resolution, however it is not done often because of its invasiveness
Is it appropriate to assume a region of the brain is critical for completing a task if neuroimaging techniques reveal that that region to be more active when completing the task
(reverse inference problem)?
Not always. Just because we see a region is more or less active during a particular behaviour doesn’t mean that we can infer that region is responsible for the behaviour itself.
- Regions may be active for a multitude of reasons unrelated to a task: changes in emotion, stress levels, fear, etc.
double dissociation
a pattern of evidence that signals that two different regions show increased activity for two different tasks
- provides evidence of localization of function
- not enough to prove causal claims
fusiform face area (FFA)
a region of the brain that shows increased activity during facial recognition
- shows a double dissociation withe the PPA
- located in the temporal lobe
parahippocampal area (PPA)
a region of the brain that shows increased activity during object/spatial recognition
- shows a double dissociation withe the FFA
- located in the inferior temporo-occipital cortex
transcranial magnetic stimulation (TMS)
a technique that uses a magnetic pulse to briefly disrupt brain function in a targeted area
- if the magnetic pulse disrupts a subject’s ability to complete the task, scientists can then infer that the targeted region is critical for completing that task
- can be used to test causal claims about the brain
- poor spatial resolution
—the magnetic pulse affects everything in its path, meaning that it is more difficult to study deeper regions in the brain
