Basic Terms and Concepts

Question 1

Electroencephalography

Answer 1

measures synchronized synaptic activity in populations of cortical neurons

Question 2

Event-related potential

Answer 2

extraction of response evoked by an external event from EEG data in order to examine the way that tasks modulate brain activity

Question 3

Magnetencephalography

Answer 3

measures magnetic field changes produced by brain activity

Question 4

Magnetic Resonance imaging

Answer 4

creates images of soft tissues in body through magnetic field reoreintation following radiofrequency pulse of protons

Question 5

Computerised tomography

Answer 5

creates images of amount of x-ray absorbed by different tissue types

Question 6

Positron Emission Topography

Answer 6

radiolabelled pharmacological agents are used to trace certain specific pathways of neural activity

Question 7

Functional Near Infrared Spectroscopy

Answer 7

measures changes in electrochemical activity and blood levels through their effect on optical properties

Question 8

Lesion studies

Answer 8

makes use of already-existing lesions to examine their effect on behaviour

Question 9

Transcranial magnetic stimulation

Answer 9

non-invasive focal stimulation of the brain to create temporary lesions

Question 10

Classic neuropsychology (lesion studies)

Answer 10

inference of function of brain regions by examining impairment of abilities of patients with lesions in that area

Question 11

Cognitive neuropsychology (lesion studies)

Answer 11

examination of impairment of abilities to infer the building blocks of cognition

Question 12

Donder’s subtraction method

Answer 12

• A, B, C type tasks
• based on isolation of specific cognitive processes –> subtraction of one from another to determine length of cognitive process
• assumes seriality and pure insertion

Question 13

Additive factor method

Answer 13

• aimed at discovering the processing stages
• information is processed in successive stages : input –> transformation –> output
• theory: if experimental manipulation increases RT, the duration of 1+ processing stages is increased but output quality is not affected

Question 14

Speed-accuracy tradeoff

Answer 14

• instructions: be fast and accurate
• no proof that RTs produced are actually as fast as pp can go with minimum errors

Question 15

Outliers

Answer 15

• lapses of attention
• premature responses
• natural skew
• slower mean RT
• skew towards caution
• bad day

-> hard to discriminate naturally slow RTs from outliers

Question 16

Diffusion model of decision making

Answer 16

• neutral point: no information
• information builds in either direction
• at a certain point, threshold is reached –> response is made
• more often correct than incorrect
• smaller boundaries: more focus on speed, but less accuracy

Question 17

Signal detection theory

Answer 17

• stimulus vs. no stimulus
• stimulus close to perceptive threshold
• Hit: yes when tone is present
• miss: no response when tone is present
• false alarm: response when tone is not present
• correct rejection: no when tone is not present
  –> depends on sensitivity (d’)

Question 18

ROC curve

Answer 18

measures % of hits against % of false alarms
- higher d’ changes shape of curve
–> differences are caused by differences in response criteria

Question 19

Sensitivity d’

Answer 19

likelihood of responding to a stimulus
- determined by comparing experimentally determined curves to standard ones
- high sensitivity = large distance between N and S+N curve -> steeper ROC curve
- d’ = 0: full overlap = guessing
- d’<0: large overlap = bad sensitivity
- d’>0: small overlap = good sensitivity

Question 20

Dipole

Answer 20

• extracellular region of pos charge separated from region of neg. charge
• source: pos. charge
• sink: neg. charge
• radial: perpendicular
• tangential: parallel

Question 21

Volume conduction

Answer 21

• pools of ions repel nearby ions of same charge -> creates wave-like effect that travels through extracellular space
• brain is not homogenous -> signal hits body tissue this may interpede flow or not
• dura layers: skull layers and scalp are very bad conductors
• electrode gel transmits signal
  bigger dipole = stronger wave that travels further

Question 22

Capacitator

Answer 22

• 2 pools of charges are separated by insulating layer
• charge difference builds up across insulating layers (anions push against one side, cations accumulate on other side)
• amount of charge building up depends on properties of layer, size of charge pool, and distance
• stacks of capacitors: volumes

Question 23

Event-related potentials

Answer 23

• extraction of response evoked by external event from EEG data in order to examine how tasks modulate brain activity

Components
- exogenous sensory components: triggered by stimulus
- endogenous sensory components: task-dependent neural processes
- motor : accompany preparation and execution of motor responses

Question 24

inverse problem

Answer 24

difficulty of identifying which brain currents are responsible for which signals (EEG and MEG)

Question 25

Event-related fields

Answer 25

average of recorded MEG signals --> allows more accurate estimation of source localisation than ERPs because of minimal distortion

Question 26

Spectral analysis

Answer 26

any oscillatory activity can be characterised as sum of different sinusoidal waves with distinct frequencies and amplitudes - Fast Fourier Transformation: estimation of contribution of various frequencies on measured EEG signal

Question 27

Structural imaging

Answer 27

- different types of tissue have different rates of absorption - used to construct detailed maps of brain structure

Question 28

Functional imaging

Answer 28

- based on assumption that neural activity produces local physiological changes in that region of the brain -> used to produce dynamic maps of moment-to-moment brain activity during cognitive tasks

Question 29

Stereotactic normalisation

Answer 29

- each brain is mapped onto a standard reference brain to correct for differences in brain size and shape --> Talairach coordinates

Question 30

Smoothing

Answer 30

- enhances signal-to-noise ratio - facilitates detection of common activity across individuals - spreads raw activation of voxel to its neighbours - SNR: increases size of active regions --> voxels mutually reinforce each other: by turning signal into cluster activity and single voxels into noise --> helps with averaging: greater area = greater chance of finding common regions of activity

Question 31

Correction for head movement

Answer 31

- small movements in scanner produce spurious results which have ot be eliminated

Question 32

Cognitive subtraction

Answer 32

- comparison of brain activity in a task which uses cognitive component X vs. baseline task without X = inference which region is specialised - meaningful interpretation only occurs relative to baseline - depends on assumption that 2 tasks can be found which differ only in small number of cognitive processes

Question 33

Factorial design

Answer 33

- set of tasks with common component --> looking for shared region across different subtractions rather than in single subtraction - baseline task is required

Question 34

Parametric design

Answer 34

- variable of interest is treated as continuous instead of categorical - measures association between brain activity and variable of interest - no baseline needed - allows separation of areas from other brain regions involved in maintenance / basis for cognitive processes

Question 35

Functional integration

Answer 35

brain regions communicate with each other: models how activity in different regions is interdependent --> used to infer effective functional connectivity between regions while performing a certain task

Question 36

Functional specialisation

Answer 36

- implication that given region responds to limited range of stimuli that distinguishes it from neighbouring regions vs. localisation: - doesn't assume other regions don't also respond to same stimulus - doesn't assume region is solely responsible for task performance

Question 37

Brain computer interface

Answer 37

interface which connects brain to computer --> allows control over external devices without relying on motor input

Question 38

Dissociation of function

Answer 38

performance on one task is impaired while performance on anohter isn't --> functions and processes are dissociable and separable - logic: separate neural resources may be indicated by difficulty in one demain rel. to absence of difficulty in another domain

Question 39

Single dissociation

Answer 39

- non-reciprocal dissociation: impairment on one task but not the other possible reasons: - hierarchical relationship: one function is necessary for the other - task-resource artifact: Task A and B use same resources but A requires it more than B --> Task A suffers more from damage - Task-demand artifact: single dissociation occurs because patient performs suboptimally on one task due to instructions becoming unclear, e.g., due to impairment

Question 40

Double dissociation

Answer 40

reciprocal dissociation of function: impairment on one task but not the other and vice versa - relatively independent functions: each lesion gives insight into involvement in one function but not the other