1 Methods in Cognitive Neuroscience Flashcards
what does the cog neuro approach provide
brain-based account of cognitive processes
give 3 examples of cognitive processes
thinking percieving remembering
how is studying cognitive processes made possible
technological advances in studying the brain that are safer and less crude than Penfield’s method
what did cognitive psychology provide
Cognitive psychology provided experimental paradigms and theoretical framework.
what does cog neuro test
Cognitive neuroscience tests psychological theories but local blood oxygen and RTs are just data, they do not tell us HOW things happen
what is priming
faster speed of response if you encounter the experience before
name the 9 methods for looking at the brain
- Single unit recording
- Electroencephalography (EEG)
- Magnetoencephalography (MEG)
- Positron Emission Tomography (PET)
- Magnetic Resonance Imaging (MRI)
- Functional MRI – fMRI
- Diffusion Tensor Imaging – DTI
- Functional Near-Infrared Spectroscopy – fNIRS
- Intracranial electroencephalography (iEEG) - ECoG
what is EEG
• Electroencephalography (EEG)
what is MEG
• Magnetoencephalography (MEG)
what is PET
• Positron Emission Tomography (PET)
what is MRI
Magnetic Resonance Imaging (MRI)
what is fMRI
Functional MRI – fMRI
what is DTI
• Diffusion Tensor Imaging – DTI
what is fNIRS
• Functional Near-Infrared Spectroscopy – fNIRS
what is ECoG
Intracranial electroencephalography (iEEG) - ECoG
what do these methods represent
98% of methods cog sci use
what method type invasiveness and brain property used is EEG/ERP
method type: recording
invasiveness: non-invasive
brain property used: electrical
what method type invasiveness and brain property used is single cell (and multi-unit) recordings
method type: recording
invasiveness: invasive
brain property used: electrical
what method type invasiveness and brain property used is TMS
method type: stimulation
invasiveness: non-invasive
brain property used: electromagnetic
what method type invasiveness and brain property used is MEG
method type: recording
invasiveness: non-invasive
brain property used: magnetic
what method type invasiveness and brain property used is PET
radio-active tracer injected in blood stream
method type: recording
invasiveness: invasive
brain property used: hemodynamic - uses some property of blood flow
what method type invasiveness and brain property used is fMRI
method type: recording
invasiveness: non-invasive
brain property used: hemodynamic - uses some property of blood flow
there is no best method
true
which has the lowest spatial resolution - at the level of the dendrite and neuron
single-cell recording
which has spatial resolution at the level of the neuron
multi-unit recording
which has the lowest temporal resolution
MEG and ERP
TMS
why is it not possible in brain to record from single neurons
dont have electrodes that are fine enough to measure a single cell
brain doesnt have pain receptors
Electrophysiological techniques- single cell recording
how does it work in monkeys
Very small electrode implanted into axon (intracellular) or outside axon membrane (extracellular)
Records neural activity from population of neurons
what happens in single unit recording in monkeys
Electrodes, consisting of thin wires, are implanted into specific areas of the brain. Recordings of brain cell activities are made by measuring the electrical potential of nearby neurons that are in close proximity to the electrode.
what happens in EEG
Electroencephalography (EEG) is the measurement of the electrical activity of the brain by recording from electrodes placed on the scalp. The resulting traces are known as an electroencephalogram (EEG) and represent an electrical signal from a large number of neurons
what is EEG used for
developmental research
how many electrodes are used in EEG
The 10–20 system of electrodes used in a typical EEG/ERP experiment.
28
258 electrodes
the more electrodes the more precise
how do cells in brain talk to eachother
through electrical impulses
non invasive
what do EEG signals represent
EEG signals represent the change in the potential difference between two electrodes placed on the scalp in time
general activity
when can EEGs form ERPs
The EEG obtained on several trials can be averaged together time locked to the stimulus to form an event-related potential (ERP)
what are ERPs
ERPs (event related potentials) are voltage fluctuations that are associated in time with particular event (visual, auditory, olfactory stimuli)
want to know reaction to a stimulus
how can ERPs be recorded
ERPs can be recorded from the human scalp and extracted from the ongoing electroencephalogram EEG by means of filtering and signal averaging.
what are different ERP peaks associated with in face processing
Different ERP peaks associated with different aspects of face processing
what is the N170 specialised for
The N170 is relatively specialized for faces, recorded from right PSTS (posterior superior temporal sulcus)
when is the posterior superior temporal sulcus active
when you see faces
when is p300 active
when you see famous and familiar faces
what is n and p
negative and positive
N170 is a trough
true
what is N170
perceptual coding of the face
affected by perceptual changes to image
what is N250
Face recognition - identity processing
unaffected by view changes but affected by familiarity
what is p400-600
person recongition
faces and names
400 - schematics
500 - know name
comparison of ERPs in Alzheimers and control
A comparison between the ERPs from patients with Alzheimer’s disease and those from control subjects. A markedly reduced P300 is seen for the demented patients at each electrode site
can be seen 10 years before development
what are the classical EEG frequencies from slowest to fastest
delta, theta, alpha and beta
what happens in EEG conversion
Th e conversion of the raw EEG from three electrodes (F3, C3 and P3) into the four classical EEG frequencies: from slowest to fastest (delta, theta, alpha and beta)
what happens in MEG
Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices known as SQUIDs. These measurements are commonly used in both research and clinical settings. Excellent temporal and spatial resolution
why is MEG not used very often
expensive
need to be kep in dry ice
isnt readily accessible
what do single cell studies tell us
Single cells studies tell us how neurons code information, by measuring their response to external stimuli
what happens when populations of neurons are active in synchrony
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
what do neuronal activity generate
Neuronal activity generates electrical and magnetic fields that can be measured invasively (single cell recordings) or non-invasively (EEG, MEG)
what is an ERP
An ERP is an electrical signature of all different cognitive components that contribute to processing of that stimulus. Systematically varying aspects of a stimulus (e.g. any face vs. famous face) may lead to variations in aspects of ERP waveform. This can tell us about the timing and independence of cognitive processes
what happens in MRI
Uses differential magnetic properties of types of tissue and of blood to produce images of the brain
what is structural imaging
Structural: different types of tissue (skull, gray matter, white matter, CSF fluid) have different physical properties – used to create STATIC maps (CT and structural MRI)
a photo of someones brain
x-rays
MRI machine
better image
what happens in functional imaging
Functional: temporary changes in brain physiology associated with cognitive processing (PET & fMRI)
what happens in PET
Measures local blood flow (rCBF)
• Radioactive tracer injected into blood stream
• Tracer takes up to 30 seconds to peak
• When the material undergoes radioactive decay a positron is emitted, which can be
picked up be the detector
• Areas of high radioactivity are associated with brain activity, based on blood volume
what does PET measure
measures blood volume directly
if a certain brain area is more active more blood will flow to that area
how long does the radioactive tracer in PET take to peak
30 seconds
what happens in fMRI
- Directly measures the concentration of deoxyhemoglobin in the blood
- This is called the BOLD response (Blood Oxygen Level Dependent contrast)
- The change in BOLD response over time is called the hemodynamic response function
- The Hemodynamic Response Function peaks in 6–8 seconds. This limits the temporal resolution of fMRI
what does fMRI directly measure
Directly measures the concentration of deoxyhemoglobin in the blood
how much oxygen that has been consumed by the brain
more blood is pumped into active areas - deoxygenated blood measuring contrast between oxy and deoxy
The Hemodynamic Response Function peaks in
6-8 seconds
what is the study correlation between brain activity and stimulus timings in fMRI
fMRI can be used to produce activation maps showing which parts of the brain are involved in a particular mental process.
what does fMRI measure activity in
Measure activity in voxels — or volume pixels the smallest distinguishable box- shaped part in 3D image
how long is the lag in fMRI
5 seconds
what is there a correlation between with brain activity
stimulus time
understanding intentions of others
‘‘intention’’ will be always used in this specific sense, to indicate the ‘‘why’’ of an action
mirror neurons
which brain areas are involved in intentions and context
Actions embedded in contexts and intentions, compared with the other two conditions, yielded a significant signal increase in the posterior part of the inferior frontal gyrus IFG and the ventral premotor cortex PMv where hand actions are represented.
premotor mirror neuron areas, previously thought to be involved only in action recognition are also involved in understanding the intentions of others.
What Does it Mean to Say a Brain Region is “Active”?
• The brain has a constant supply of blood and oxygen; if it didn’t, it would die, this
means we cannot literally stick someone in a scanner and read their thoughts
(because the whole brain would look active)
• In order to infer functional specialization, one needs to compare RELATIVE
differences in brain activity between two or more conditions
• This involves selecting a baseline or comparison condition
what happens when a brain region is active
A region is “active” if it shows a greater response in one condition relative to another. If the experimenter chooses inappropriate conditions the regions of activity will be meaningless
what is a cognitive subtraction
activity in a control task is subtracted from the activity in an experimental task
who did the brain region experiment
peterson et al 1988
what regions in the brain are used for recognising words
occipital-temporal junction
how to work out what regions in the brain are used for recognising words
word - cross
passive viewing of written words vs passive viewing of fixation cross
cognitive components
word recognition
what region of brain used for saying words
motor areas
how to work out what region of brain used for saying words
reading aloud - passive
read aloud a written word - experiemental - cognitive- and phonology/articulation
passive viewing of written word - baseline - cognitive components
what region of brain is used for retrieving meaning
inferior frontal cortex
left inferior frontal gyrus
how do we know what region of brain is used for retrieving meaning
verb generation - eading
experimental - generate an action e.g. see cake say eat -cog component - retrieve meaning
baseline - read aloud - cog components
what is the problem with cog subtractions
Problems: difficulty of the baseline task
if too easy - active - all vocals active when not actually active
disagreements between imaging and lesion studies
evidence from semantic processing
left inferior frontal gyrus implicated by brain imaging studies of semantic memory
left anterior temporal lobe implicated in semantic dementia
what does Devlin fMRI show
Areas of activation in the Semantic minus Letter categorization comparison
what is DTI
Diffusion Tensor Imaging
what happens in DTI
An imaging method that uses a modified MRI scanner to reveal bundles of axons in the living brain
Measures white matter organization based on limited diffusion of water molecules in axons - axons that are mylonated - water move within and cannot escape bc of lipid covering
We can visualize connections in the brain
what is Functional Near-Infrared Spectroscopy (fNIRS)
Measures the same BOLD response as fMRI but in a completely different way ‘
Light’ in infrared range passes through skull and scalp but is scattered differently by oxy- v. deoxyhemoglobin
Portable and more tolerant of head movement but can’t image deep structures
what is similar between Functional Near-Infrared Spectroscopy (fNIRS) and fMRI
measures the same BOLD
create similar pictures
done in more natrualistic settings
what is Intracranial electroencephalography (iEEG) or ECoG
The only method that gives us the high resolution in both place and time is intercranial recording, when we record directly from the inside the human brain, when people are undergoing neurosurgery
They are placed to locate the seizure and map function (for neurosurgery purposes)
Recording straight from the cortical surface, approximately from tens of thousands of neurons
how does intracranial electroencephalography (iEEG) or ECoG work
hospital settings - surgery for epilepsy
remove a bit of bone to get brain and put electrodes to measure location of epilepst to map functions
if near vocal dont take out part of brain
In tracranial recordings - in Humans (ECoG) - mukamel et al., 2010
recorded extracellular activity from 1177 cells in human medial frontal and temporal cortices while patients executed or observed hand grasping actions and facial emotional expressions (control condition).
Neurons in supplementary motor area SMA, and hippocampus responded to both observation and execution of actions
brain can mirror different actions -
how to pick a neuroimaging technique
pick based on research question
