methods of cognitive neuroscience Flashcards
What is the primary objective of cognitive neuroscience, and how does it differ from traditional approaches like Penfield’s method?
cognitive neuroscience gives us a brain based account of how our cognitive process happen
give us experimental paradigms using modern technology (safer than Penfield) to expand our understanding
Give some examples of different recording methods used in cognitive neuroscience
EEG, Single-Cell, MEG, PET, fMRI
Which stimulating method is often used in cognitive neuroscience?
TMS
What are the main 2 invasive measures used in cognitive neuroscience?
single cell, PET
What is single cell recording?
Small electrode planted into axon (INTRACELLULAR) or outside axon membrane (EXTRACELLULAR).
Firing rate and pattern of single receptor cell can be measured in response to sensory input
Recordings of brain activities, measuring electrical potentials of nearby neurons
How does an EEG work? (electroencephalogram)
Positions electrodes over the scalp to show the brain’s electrical activity.
Measures amount of activity caused by stimulus or event
Voltage change at the scalp: how many neurons fire and how synchronous firing is.
What is rate coding?
Rate of firing - Informational content of a neuron related to the number of action potentials per second
What is temporal coding?
How synchronous firing is
What is a reference point?
Part of the brain used to compare if something is in motion. Uninfluenced by variable / event being measured.
Why is EEG not always best equipped for detecting location?
Neural activity can be recorded at a location even when neural activity isn’t at that location - can show firings in multiple areas (also signal to noise)
What is a dipole?
A pair of positive and negative electrical charges separated by a small distance
What is polarity?
Distribution of electrical charges across neurons and their connections. Direction of the electrical current flow.
By manipulating the polarity of electrical stimulation - investigate how brain regions are involved in cognitive processes.
Positive polarity
High electrical charge at the electrode compared to reference point
Negative polarity
Low electrical charge at electrode compared to reference
How does an ERP (event related potentials) differ from an EEG?
ERP = SPECIFIC brain response to a stimulus
EEG reflects neural activity from all parts of the brain. Some activity relates to specific tasks - reading or listening but a lot of the activity from EEG is spontaneous
Signal to noise ratio
Signal = electrical neural response to the event
Noise = background level of electrical activity
It becomes harder to detect a signal as background noise increases
- Seen in EEG’s
What do EEG signals represent?
The changes in potentials between two electrodes = rate of firing and how synchronous firing is
How do EEG’s form ERP’s?
EEG’s obtained on several trials are averaged to form an ERP. This decreases signal to noise ratio and reduces contribution of fluctuations not related to the event
What is an ERP? (event related potential)
Voltage fluctuations associated in time with particular event
What ERP is involved in perceptual coding
N170 - specialised for face perception (right posterior superior temporal sulcus) - changes to image and coding of faces.
What ERP is involved in recognising famous and familiar faces?
P300
What ERP is involved in familiarity? - face recognition and identity processing
N250
What ERP is involved in person recognition? - activated by faces and names
P400-P600
What is mental chronometry?
Changes in the efficiency of information processing - time it takes for cognitive processes to occur. Duration and speed. E.G PPTs are faster at working out 4+2=6 compared to 4+3=7
What is associative priming?
Shorter reaction times when the target stimulus is related to the previously presented stimulus compared to when the target is unrelated. A prime stimulus activates / brings to mind a related concept.
What are exogenous components of ERPs?
Neural responses linked to the physical characteristics of a stimulus; occur early in the waveform (P1 / N1)- initial onset of stimulus. PROPERTIES OF STIMULUS
What are endogenous components of ERPs?
Neural responses modulated by internal cognitive processes - higher order cognitive functions (N400). Later in the wave form - PROPERTIES OF THE TASK
What is the inverse problem in ERP research?
Difficulty locating the source of electrical activity
What is dipole modelling?
Solves the inverse problem - assumes how many dipoles (regions of activity) contribute to the signal recorded at the scalp
what is single cell recording
- very small electrodes implanted into axon (intracellular) or outside axon membrane (extracellular)
- records neural activity from population of neurones
- recordings made by measuring electrical potential of nearby neurones that are close to the electrode
what is found in terms of ERP’s from Alzheimer patients?
reduced P300
What is Magnetoencephalography (MEG)
- an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via SQUIDS
- commonly used in research and clinical settings
- high temporal and spatial resolution
- very expensive and lots of energy needed
what is structural imaging?
- creates STATIC maps of different types of tissue (skull, grey matter, white matter, CSF) due to their different properties
- CT & Structural MRI
what is functional imaging?
- maps temporary changes in brain physiology associated with cognitive processing
- (PET & fMRI)
What is a PET (positron emission tomography) scan?
measures local blood flow
- radioactive tracer injected into blood stream, takes up to 30s to peak
- when material undergoes radioactive decay, positron is emitted which can be picked up by the detector
- areas of high radioactivity are associated with brain activity
What is an fMRI?
- studies correlation between brain activity and stimulus timings
- directly measures the concentration of deocyhemoglobin in the blood called the BOLD response
- change in BOLD over time is the hemodynamic response function
- HRF peaks in 6-8 seconds which limits temporal resolution but has good spatial resolution
What is DTI (diffusion tensor imaging)?
- imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain
- measures white matter organisation based on limited diffusion of water molecules in axons
what is functional Near Infrared Spectroscopy (fNRIS)
- measures BOLD response like fMRI but in different way
- light in infrared passes through skull and scalp but is scattered by oxy- v. deoxyhemoglobin
- portable method and more tolerant of head movement
- cannot image deep structures
what is intracranial EEG?
- record directly from inside human brain during neurosurgery
- only method that gives high resolution in both place and time
What is transcranial magnetic stimulation?
- a means of disrupting normal brain activity by introducing neural noise (virtual lesion)
- Faradays Coil
what are the advantages of TMS?
- Interference/virtual lesion technique.
- transient and reversible
- Control location of stimulation
- Establishes a causal link of different brain areas and a behavioural task
Which brain measuring techniques involves diapoles?
(MEG). MEG measures the magnetic fields produced by the electrical activity in the brain.
When neurons in the brain are activated, they produce tiny electrical currents. These currents create weak magnetic fields that can be detected.
The dipoles refer to the pairs of positive and negative charges that are generated when neurons fire, creating a current flow.
MEG measures these dipoles to map brain activity with high temporal and spatial resolution
Outline the recording techniques used in cognitive neuroscience.
- Neuronal activity generates electrical and magnetic fields that can be measured invasively (single cell
recordings) or non-invasively (EEG, MEG) - Single cells studies tell us how neurons code information, by measuring their response to external stimuli
- When populations of neurons are active in synchrony, they produce an electric field that can be detected at
the scalp (EEG). When many waves are averaged and linked to the onset of the stimulus, then an ERP is
obtained - An ERP is an electrical signature of all different cognitive components that contribute to processing of that
stimulus. This can tell us about the timing and independence of cognitive processes
