1b Methods in Cog Neuro

What is the cog neuro approach to cognitive processes

a brain-based account

What are the two key dimensions for evaluating neuroimaging methods?

Temporal resolution and spatial resolution

Name 9 of the cognitive neuroscience methods

single-unit recording, EEG, MEG, PET, MRI, fMRI, DTI, fNIRS, iEEG/ECoG

What is the method behind single cell recording

a small electrode is implanted into axon or outside axon membrane (specific areas of the brain)

What are the formal terms for inside vs outside axon membrane

intracellular vs extracellular

What does single cell recording measure

neural activity from a population of neurons in response to stimuli

How does single cell recording measure brain cell activities

by measuring the electrical potential of nearby neurons to the electrode

Spell out EEG

electroencephalography

What is the method being EEG

electrodes placed on the scalp

What does EEG measure

electrical activity of the brain

What are the resulting traces of EEG measurement

electroencephalogram (EEG 2)

What do EEG 2 traces represent

an electrical signal from a large number of neurons

What does each electrode measure in EEG

the difference in electrical charge (voltage) between the recording and a reference electrode in time

What do the differences in electrical charge of electrodes reflect

brain activity

What is the strength of electrical signals (strong or weak (formal name))

weak (microvolts)

What are two steps in improving the weak electrical signals from the brain

amplified and filtered

Two examples of what must be filtered from EEG signals

noise eye blinks and muscle movement

Spell out ERPs

event-related potential

What are ERPs

voltage fluctuations that are associated in time with particular event

How are ERPs obtained

the EEG obtained on several trials is averaged together time-locked to the stimulus

What is an "event" in ERP?

A presented stimulus, sound, or word that triggers a small electrical change in the brain

What is associated with different aspects of face processing

different ERP peaks

What ERP component is associated with face processing/specialised for faces

N170

What is the P300 ERP component associated with

familiar and famous faces

What reduced ERP component is associated with patients with Alzheimer’s disease

P300

What two aspects of brain waves do EEG spectral analysis examine

frequency and power

What functions are different EEG waveforms associated with

different cognitive functions

Spell out MEG

magnetoencephalography

What is the method used with MEG

imaging technique using sensitive devices

What are the sensitive devices in MEG called

SQUIDs

What does MEG measure

the magnetic fields produced by electrical activity in the brain

Spell out MRI

magnetic resonance imaging

What does MRI use to produce brain images (two components of brain)

different magnetic properties of types of tissues and of blood

What is structural imaging

uses different physical properties of tissues types to create STATIC maps

What are 4 different types of tissue

skull, gray matter, white matter, CSF fluid

What is functional imaging

temporary changes in brain physiology associated with cognitive processing

Two examples of functional imaging

PET and fMRI

Is MRI an example of structural or functional imaging

structural

Spell out PET

positron emission tomography

What is the method used for PET

a radioactive tracer is injected into blood stream; when the material undergoes radioactive decay, a positron is emitted and picked up by the scanner detector

How long does it take for the tracker to peak in PET

up to 30 seconds

What does PET measure

local blood flow

What is the abbreviation for local blood flow

rCBF

What are areas of high radioactivity associated with in PET, and what is this based on

brain activity, based on blood volume

What do radioactive tracers measure in PET

different brain properties/functions

Spell out fMRI

functional magnetic resonance imaging

What 2 things does mental activity require as fuel, and what carries them

glucose and oxygen, carried by haemoglobin (Hb)

With the knowledge of what mental activity requires, what occurs when neurons are active

oxygenated blood flows to the area

What is the method used by fMRI to identify active brain regions

detect blood oxygenation changes through detectable magnetic signal changes (BOLD response) created by deoxyhemoglobin’s magnetic properties

What does fMRI directly measure

the concentration of deoxyhemoglobin in the blood

What is the BOLD response detected by fMRI

blood oxygen level dependent contrast

What is the change in BOLD response over time called

hemodynamic response function

When (in seconds) does the hemodynamic response function peak

in 6-8 seconds

What does the peak time limit in fMRI

temporal resolution

What is the purpose of fMRI studies and how might this be a limitation

to study the correlation between brain activity and stimulus timings, only correlational

What do activation maps in fMRI show

which parts of the brain are involved in particular mental processes

How is activity measured on activation maps

in voxels

What is a voxel in fMRI

the smallest distinguishable box (in a 3D image)

Why can it be difficult to pin point activity in the brain when using fMRI

because the brain has a constant supply of blood and oxygen which makes the whole brain look active

How do we infer functional specialisation in fMRI

by comparing relative differences in brain activity between two or more conditions (baseline/comparison condition needed)

What does it mean when we say a brain region is "active" in fMRI?

It shows a greater response in one condition relative to another

What is cognitive subtraction in fMRI (an equation)?

Activity in a control task is subtracted from the activity in an experimental task

What are 4 advantages of fMRI (resolution, coverage, technique, application)

excellent spatial resolution, whole brain coverage, non-invasive and safe, and widely used in cog and clinical research

Why is it a limitation if the BOLD effect is small, how does this impact the process of obtaining brain response measures

sensitivity is limited so requires multiple samplings

When is fMRI reliability reduced, think about a potential confound

When a participant moves

What 4 everyday substances affect blood levels in fMRI, and what is the consequence of this?

Caffeine, nicotine, glucose, and hormones; likely affect the BOLD signal

What 3 factors affect the magnitude of the BOLD response?

Ageing, impaired cerebrovascular supply, and proximity to sinuses

Spell out DTI

diffusion tensor imaging

What is the method used for DTI

imaging method which reveals bundles of axons in the brain

What does DTI measure, and using what

white matter connectivity between brain regions using MRI

What are white-matter pathways in DTI

pathways formed by grouped axons that started and ended in each other’s vicinity

What does DTI allow us to visualise, and is the focus structural or functional

connections in the brain, structural

What can DTI test that is relevant to the neural basis of behaviour

changes in connectivity between brain regions

Spell out fNIRS

functional near-infrared spectroscopy

What is the method used by fNIRS

emits light on the skull using a set of small photo emitters and measures reflection of light

What info does reflectance provide in fNIRS

activity in brain

What picks up reflectance

photo detectors

What size wavelengths does fNIRS emit (in nanometers)

between 700-900

What brain components are mostally transparent to the light in fNIRS

skin, tissues and bone

What are 2 strong absorbers of fNIRS light, and are they similar or different profiles of reflectance

haemoglobin and deoxyhaemoglobin, different

What causes reflectance of light to change in fNIRS?

Concentration changes due to neural activity

What 2 things does fNIRS pick up that is similar to fMRI?

The same BOLD contrast and hemodynamic response function

Relative to fMRI, what are the 2 cons of fNIRS (resolution, depth)

poorer spatial resolution due to limited fine spatial localisation, and only measures superficial activity

What depth does fNIRS lack

no reflectance from within sulci or deeper structures

Relative to fMRI, what are the 4 pros of fNIRS (ease, cost, safety, specific population)

portable, cheaper, less intrusive and drawbacks are alleviated in infants

Why are fNIRS drawbacks alleviated in infants, 2 reasons ?

Infants have thin skulls and small heads

Spell out iEEG

intracranial electroencephalography

What is the method used for iEEG

electrodes surgically implanted inside human brain when people are undergoing neurosurgery

What do electrodes do in iEEG

locate seizure and map function

Where does iEEG record from

straight from the cortical surface

Approximately how many neurons does iEEG record from?

Tens of thousands of neurons

What 3 methods in cog neuro use electrical property of brain

EEG, single-cell recording, iEEG

What 3 methods in cog neuro use magnetic property of brain

MEG, MRI, DTI

What 3 methods in cog neuro use haemodynamic property of brain

PET, fMRI, fNIRS

Which 3 methods in cog neuro are invasive

single-cell recording, PET, iEEG

Which 6 methods in cog neuro are non-invasive

EEG, MEG, MRI, fMRI, DTI, fNIRS

Which 2 cog neuro methods have excellent temporal and spatial resolution

single-cell recording and iEEG

Which cog neuro method is moderate in both temporal and spatial resolution

fNIRS

Which 2 cog neuro methods are only structural, so no temporal resolution

MRI and DTI

Which 2 cog neuro methods have good temporal but poor spatial resolution

EEG and MEG