Weeks 1-3 Jen Mcbride & Wai Yeung Flashcards
What does cognitive neuroscience provide?
A brain based account of cognitive proceses.
(Thinking, perceiving, remembering etc)
What makes cognitive neuroscience possible?
Technological advances
(that are safer and less crude than Penfield’s method).
What are the 11 main imaging techniques?
Single Cell 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)
Transcranial Magnetic Stimulation (TMS)
Transcranial Electrical Stimulation (tES - tDCS & tACS)
Outline the method type, invasiveness and brain property used for EEG/ERP.
Recording
Non-invasive
Electrical
Outline the method type, invasiveness and brain property used for Single-cell (and multi unit) recordings.
Recording
Invasive
Electrical
Outline the method type, invasiveness and brain property used for TMS.
Stimulation
Non-invasive
Electromagnetic
Outline the method type, invasiveness and brain property used for MEG
Recording
Non-invasive
Magnetic
Outline the method type, invasiveness and brain property used for PET
Recording
Invasive
Hemodynamic
Outline the method type, invasiveness and brain property used for fMRI.
Recording
Non-invasive
Hemodynamic
What does hemodynamic mean?
Looking at the blood flow in the brain to measure that
What is the basic process of single cell recording?
A very small electrode is implanted into an axon (intracellular) or outside axon membrane (extracellular)
Records neural activity from population of neurons (or precise neuron).
The closer the electrode is to the neuron, the higher the firing rate is. (detected by an oscilloscope)
What is the basic process of EEG?
It is the measurement of the electrical activity of the brain by recording from electrodes placed on the scalp.
Stimulus is presented
EEG amplifies it
A raw trace is created (with lot’s of noise)
How does EEG work? What is their relations to ERPs?
EEG signals represent the change in the potential difference between two electrodes placed on the scalp in time.
ERPs are voltage fluctuations that are associated in time with a particular event (average of the EEGs with the noise cancelled out).
An EEG repeated numerous times leads to an ERP.
What are the following:
- N170
- N250
- P300
What do they represent?
Explain the notation too.
These are all peaks on an ERP chart related to different aspects of face processing.
N is for negative, P is for positive and the number is the time (ms) it appears.
N170:
- Perceptual coding of the face.
- recorded from the right PSTS (posterior superior temporal sulcus).
N250:
- Face recognition (identity processing)
P300:
- Person recognition (face and names)
These occur sequentially in the above order and show the development of facial processing to a conscious understanding of who and what is in front of you.
Briefly outline the differences between Alzheimer’s patients and Healthy controls in their ERPs.
P300 was reduced in Alzheimer’s patients.
This is the facial recognition (who is this?) ERP and makes sense as there is a reduced memory in these patients, therefore less likely to recognise them.
Summarise MEG:
- What is it and how does it work?
- Why isn’t it used more often?
It is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices known as SQUIDS.
Magnetic fields generated by our brain activities are weak therefore this machine is very sensitive and resultingly expensive - hence it isn’t used that much.
Has an excellent temporal and spatial resolution.
(FYI, SQUIDS = superconducting quantum Interference device)
What is MRI? What are the two types?
Magnetic Resonance Imaging - uses differential magnetic properties of types of tissue and of blood to produce the images of the brain.
Structural:
- Looks at different types of tissues with different physical properties and creates STATIC maps.
Functional:
- Temporary changes in brain physiology associated with cognitive processing
What are the two main types of functional imaging?
PET and fMRI
What are the two main types of structural imaging?
CT and structural MRI
How does PET work?
It measures local blood flow.
PROCESS:
- 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 by the detector.
- Areas of high radioactivity are associated with brain activity, based on blood volume.
How does fMRI work?
It directly measures the concentration of deoxyhaemoglobin in the blood.
This is called the BOLD response (Blood Oxygen Level Dependent)
This change in BOLD response over time is used to make activation maps showing which parts of the brain are involved in particular mental processes.
How is activity measured spatially in fMRI?
Voxels
Volume pixels - the smallest distinguishable box-shaped part in 3D image.
What does it mean to say a brain region is active?
How can we infer functional specialisation using this information?
The brain has a constant supply of oxygen - if it didn’t, it would die.
Therefore, to infer functional specialisation, there must be a relative comparison between brain activity.
So to say an area is active, there must be more activity relative to baseline.
What are cognitive subtractions in fMRI studies?
When the activity in a control task is subtracted from the activity in an experimental task.
What is DTI imaging and what is the basic process behind it?
Diffusion Tensor Imaging.
It uses a modified MRI scanner to reveal bundles of axons in the living brain.
It measures white matter organisation based on limited diffusion of water molecules in axons.
Allowing us to be able to visualise connections in the brain.
(it produces a very colourful visualisation of the brain)
What is fNIRS?
Functional Near-Infrared Spectroscopy (fNIRS)
Measures BOLD response but in different way to fMRI.
‘Light’ in infrared range passes through the skull and scalp and is scattered differently by oxy-/deoxyhaemoglobin.
It is portable and more tolerant of head movement but can’t image deep structures.
What is iEEG?
Intracranial electroencephalography.
Only method to give both high spatial and temporal resolution.
Occurs during neurosurgery where electrodes are placed directly on the brain to locate seizure location/map functions.
Records straight from cortical surface, approximately from tens of thousands of neurons.
What is TMS?
Transcranial Magnetic Stimulation: a means of disrupting normal brain activity by introducing neural noise – “virtual lesion”
What are the advantages of TMS (4)
- interference/virtual lesion technique.
- transient and reversible
- control the location of stimulation
- establishes a causal link between different brain areas and a behavioural task
How does TMS work?
(4 steps)
- TMS pulse applied at a cortical node (area) of the network
- TMS will interfere with the relevant neural signal
- The efficacy of the neural signal will be degraded
- We observe changes in behaviour (RT change – it will take us longer to perform a given task)
What is language lateralization?
(hint - hemisphere)
Left hemisphere shows greater involvement in language functions that the right
How does TES work?
Transcranial Electric Stimulation uses low-level (1-2 mA) currents applied via scalp electrodes to specific brain regions
What are the protocols for TES? (3 types)
- Transcranial direct current stimulation - tDCS
- Transcranial alternating current stimulation -tACS
- Transcranial random noise stimulation - tRNS
What are the lasting effects of tDCS? (TES protocol)
When applied in sessions of repeated stimulation, tDCS can lead to changes in neuronal excitability that outlast the stimulation itself. Such aftereffects are at the heart of the tDCS protocols for clinical application
What conditions does tDCS show promising improvements in? (9)
-migraines,
-dementia,
-stroke,
-Parkinson’s disease,
-neglect,
-depression,
-schizophrenia,
-OCD,
-eating disorders
What are the 3 types of tDCS? What effects do they have?
- Anodal stimulation (positive to negative): facilitation effects
- Cathodal stimulation (negative to positive) :– inhibition effects
- Sham (CONTROL) - 30sec stimulation
What neurotransmitter does Anodal stimulation (tDCS) inhibit?
GABA
(GABA inhibits transmission to neurons => it is an inhibitory neurotransmitter so if inhibited it FACILITATES excitability of neurons)
What neurotransmitter does Cathodal stimulation (tDCS) inhibit?
Glutamate
(glutamate is excitatory=> if inhibited it also inhibits neurons’ excitability)
How does tACS (TES protocol) work?
Transcranial alternating current stimulation uses low-level (0.5-2 mA) alternating currents applied via scalp electrodes to specific brain regions.