Cognitive Neuroscience Flashcards
(23 cards)
What are the challenges for cognitive neuroscience?
Complex systems
Signal to noise ratio
Between-individual differences
Within-individual differences
Cognitive neuroscience techniques for brain structures
Autopsy
Structural Magnetic Resonance Imaging (MRI)
Cognitive neuroscience techniques for brain function
Scalp-located electrodes (EEG, ERP) Functional MRI (fMRI) Magneto-encephalography (MEG) Transcranial Magnetic Stimulation (TMS) Positron Emission Tomography (PET)
Cognitive neuroscience techniques for neuropsychology
Data from individuals with brain damage
fMRI advantages
Location of brain structure used in tasks
Reasonable temporal resolution
Get structural data within same session
fMRI disadvantages
Claustrophobic
Noisy
Movement artifacts (difficult for button presses)
Can’t have metal based equipment for stimuli
BOLD isn’t a direct measure of activity and care need to be taken when interpreting it
Transcranial Magnetic Stimulation principles
Noninvasive method which depolarises or hyperpolarises neurons in the brain (decrease/increase activity)
Electromagnetic induction induces weak electric currents in the cortex
Can cause motor evoked potential (limb twitches)
Can produce simulated temporary ‘lesion’ of brain region by preventing normal function without any long-lasting adverse effects
Who invented TMS?
Tony Barker and colleagues at the University of Sheffield in 1985
TMS advantages
Near portable
Can stimulate or lesion
Disadvantages of TMS
Difficult to specify precise regions
Only surface regions
Magnetoencephalogram (MEG)
Pyramidal cells of cortex, when active, generate significant magnetic field
MEG records this
Synchronous firing of 10000s neurons is required to produce a field large enough to measure
Magnetic fields are less distorted by the scalp than electrical fields
Advantages of MEG
Excellent temporal resolution
Good spatial resolution (not distorted by scalp and for the whole brain) especially when combined with MRI
Disadvantages of MEG
Expensive
The inverse problem for finding what causes what
Electroencephalography (EEG)
Measures electrical signals generated by the brain through electrodes placed at the scalp
EEG signals are produced by partial synchronisation of cortical field activity and are measured as changes in voltage, recorded at the scalp over time
Analysis of EEG signals may be…
Task-dependent or task-independent
How are EEG signals detected?
Electrodes are placed on the scalp, connected with gel or conductive solution
EEG signals are transported to an amplifier
Amplifier measures the difference in voltage between the active electrode and a reference electrode
What is the frequency of measurements in an EEG?
Up to 2000Hz
EEG advantages
Very good temporal resolution Less subject to motion artefacts Not claustrophobic Can be used by infants Major artefacts in eye blinks can be eliminated by monitoring eyelid
Disadvantages of EEG
Weak spatial resolution
Inverse problem - given pattern of activity, how do you determine which brain region caused it?
Principles of how information travels around the brain
Information received at dendrites
Travels to cell body
Down axon
To the synapse
How do we know where early visual processing occurs in the brain?
Using fMRI scans
Occurs in the primary visual cortex (V1)
N170
What is an ERP?
An event-related potential
A measured brain response that is a direct result of a specific sensory, cognitive or motor event
What is the N170
A component of ERPs that reflects the neural processing of faces in the brain
