Methods in CN

Question 1

What is single cell recording?
How and What does it record?

Answer 1

When a small electrode is implanted into an axon or outside its membrane

Records neural activity (EP) from a population of neurons nearby

invasive

Question 2

What does single cell recording tell us?

Answer 2

how neurons code info by measuring responses to external stimuli

Question 3

Single cell recording - if electrode in placed correctly…

Answer 3

if close to where brain activity is, oscilloscope will have readings very close to each other rather than sporadic

Question 4

what is electroencephalography (EEG)?
How and What does it record?

Answer 4

the measuring of electrical activity of the brain

Uses electrodes placed on the scalp. Records EEG which represents an electrical signal from a large number of neurons

non-invasive

Question 5

EEG signals - what do they represent?

Answer 5

EEG signals represent changes in PD between two electrodes

Question 6

EEG - what is an ERP?

Answer 6

EEGs obtained on several trials can be averaged together to form an ERP

are voltage fluctuations that are associated in time with a particular event

tell us about timing and independence of cognitive processes

Question 7

ERP - different aspects of face processing

N170 and P300

Answer 7

different ERP peaks are associated with different aspects of face processing

N17: relatively specialised for faces. recorded from right PSTS

P300: famous and familiar faces

Question 8

ERP - P300 in Alzheimer’s disease

Answer 8

have reduced P300 at each electrode site

Question 9

What is MEG?

Answer 9

Magnetoencephalography

imaging technique used to measure the magnetic fields produced by electrical activity in the brain

Use SQUIDS

non-invasive

Question 10

MEG - resolution

Answer 10

excellent temporal and spatial resolution

Question 11

What is MRI?

Answer 11

uses differential magnetic properties of types of tissue and blood to produce images of the brain

Question 12

What is structural imaging?

Answer 12

different types of tissue have different physical properties

create STATIC maps (CT and MRI)

Question 13

What is functional imaging?

Answer 13

temporary changes in brain psychology associated with cognitive processing

PET and fMRI

Question 14

What is PET?

Answer 14

Positron Emission Tomography

measures local blood flow (rCBF) by using a radioactive tracer which is injected into the blood stream (30s)

Question 15

PET - process

Answer 15

when the material undergoes radioactive decay, a positron is emitted, which is picked up by the detector

areas of high radioactivity are associated with brain activity - based on blood volume

Question 16

What is fMRI?

Answer 16

directly measures the concentration of deoxyhemoglobin in the blood

Question 17

fMRI: what is the BOLD response?

Answer 17

Blood Oxygen Level Dependent contrast

conc. of deoxy.

Question 18

what is the hemodynamic response function?

Answer 18

change in BOLD over time

peaks in 6-8, limiting the temporal resolution

Question 19

what does fMRI produce?

Answer 19

activation maps which show parts of the brain involved in particular mental processes

Question 20

fMRI - what are voxels?

Answer 20

measurement of activity

volume pixels: smallest distinguishable box-shaped part in 3D image

Question 21

What Does it Mean to Say a Brain Region is “Active”?

Answer 21

brain has constant supply of blood and oxygen

Question 22

functional specialisation

Answer 22

whole brain would look active so need to compare relative differences in brain activity between two or more conditions

have to select a baseline or comparison condition

Question 23

what is cognitive subraction?

Answer 23

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

issue: difficulty of baseline task

Question 24

What is DTI?

Answer 24

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

visualise connections in the brain

Question 25

what is fNIRS?

Answer 25

Functional Near-Infared Spectroscopy

Measures the same BOLD response as fMRI but…

‘light’ in infared range passes through skull and scalp but is scattered differently by oxy-v. Deoxyhemoglobin

Question 26

Pros and Cons of fNIRS

Answer 26

portable and more tolerant of head movement

can’t image deep structures

Question 27

What is iEEG/ECoG?

Answer 27

only method that gives high resolution in place and time

record directly from inside brain during neurosurgery

(cortical surface, tens of thousands of neurons)

grid placed to locate seizure and map function

Question 28

ECoG (intracranial recordings) in humans

Answer 28

record extracellular activity from 1177 cells in medial frontal and temporal cortices

while hand grasping actions and facial emotional expressions

neurons in supplementary motor area (SMA) and hippocampus, responsed to both observation and execution of actions