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PSY4035 > Task 1 > Flashcards

Task 1 Flashcards

1
Q

What does EEG measure?

A

Records changes in brain activity over time by measuring differences in voltage between 2 electrode sites sampled at regular time intervals

It measures cycles per second/hertz (frequency) over time in mm; adult brain activity is 1-100Hz. Sleep & relaxation have slower HZ (1-13), and alertness is between 13-100 (Hz).

Sample EEG ranges from 500-1000 Hz or higher – data point recorded every 0.5-2ms.

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2
Q

What is the adult brain activity frequency range?

A

1-1000Hz

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3
Q

What is the brain frequency for sleep & relaxation?

A

slower at 1-13Hz

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4
Q

What is the brain frequency range for alertness?

A

13-100Hz

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5
Q

How can noise/artefacts be eliminated?

A

Low-pass filter: filters low noise (e.g. movements & skin potentials)

High-pass filter: filters high frequency noise (e.g. external sources, equipments)

Bandpass filter: filters both low & high

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6
Q

Name two ways in which electrodes are typically placed in EEG studies

A

10-20 international system

Spherical coordination

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7
Q

What are noise/artefacts in EEG studies?

A

unwanted signals which are mainly originated from environment noise, experimental error and physiological artifacts

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8
Q

What ERPs?

A

Averages of epochs of EGG at each electrode site, time-locked response to specific stimuli.
Characterized by negative & positive waveforms.
Fluctuations in voltage linked to specific sensory or cognitive events = components

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9
Q

Describe the 3 characteristics of ERP components

A

Polarity: negative-positive

Peak latency: timing of component’s higher/lowest peak (e.g. N400)

Order: of occurrence of waveform (e.g. first positive = P1)

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10
Q

What are ERP components?

A

Fluctuations in voltage linked to specific sensory or cognitive events

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11
Q

What are the 3 measures of ERP components?

A

Latency: timing
Longer = slower processing & related with higher order cognitive processing

Amplitude: max/mean P/N microvolts in time window)
Larger = more neural activities

Distribution: activity across the scalp/location
Area of given ERP component’s effect

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12
Q

What does a longer latency in an ERP indicate?

A

Slower processing & is related to higher order cognitive processing

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13
Q

What does amplitude in ERP refer to?

A

Max/mean positive or negatice microvolts in a time window

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14
Q

Name 6 advantages of ERP/EEG

A

Does not require overt responses

It is well-suited for the study of comprehension independent of production

Provides online measure of cognitive processing

Can be used to compare changes in brain activity across lifespan

High temporal resolution

Provides direct & instant measure of neural activity unlike NIRS & Fmri

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15
Q

List 5 disadvantages of EEG/ERPs

A

Sensitive to movements

ERPs can be largely distorted by large artefacts especially if they are time-locked to stimuli

Trials containing large voltages (for infants) can be rejected which is problematic

Limited spatial resolution

Precise relation between physiological source of brain activity & resulting surface potential is not fully understood.

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16
Q

What can be studied by NIRS?

A

Object processing in infants

Social communication

Voice processing

Face processing

Human action processing

Action observation

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17
Q

What does NIRS measure?

A

Changes in hemoglobin levels

Amplitude & timing hemoglobin activation is called hemodynamic response function (HDF

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18
Q

How does NIRS work?

A

It relies on relative transparency of biological tissue to near-infrared light & absorption of oxy & deoxyhemoglobin.

The firing of neurons causes increases in local blood flow that is not proportionate to the O2 demands; oxy (HbO) increases & deoxy (HHb) decreases, thus total hemoglobin level increases.

Light migrates from sources to detectors located on the head by travelling through the skin, skull & underlying tissue.

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19
Q

What happens to oxygen in the brain when neurons fire together?

A

There is an increase in local blood flow that is not proportionate to the oxygen demands.

Oxyhemoglobin (HBO) increases and deoxyhemoglobin (HBB) decreases.

Thus, the total level of hemoglobin increases.

20
Q

List 8 advantages of NIRS

A

When compared to EEG, it is less susceptible to data corruptions by artefacts

More spatially resolved image

Allows for localization of brain responses to cortical regions

Superior temporal resolution

Is silent

Measures both HbO & HBB

Fnirs has higher temporal resolution than NIRS

It’s portable & cheaper

21
Q

What is one advantage of NIRS over EEG infant studies?

A

It is not sensitive to movements thus it is less susceptible to data corruptions caused by artefacts

22
Q

List 3 disadvantages of NIRS

A

FNIRS has lower temporal resolution than EEG

Its depth resolution is dependent on age

Lower spatial resolution compared to MRI

23
Q

What is the difference in temporal resolution between NIRS & FNIRS?

A

FNIRS has a higher temporal resolution

24
Q

How do MRIs work?

A

Uses non-ionizing radio frequency (RD) energy to generate signal from the body.

Less energy are transmitted and electrons are excited to higher state, unlike PET & CT scans that removes electrons from their orbit..

MRI act as a magnet of hydrogen in the body & metals

25
Q

What do MRIs measure?

A

Structural images

volume, shape & position of tissues

26
Q

What can be studied using MRI?

A

Gray & white matter activities

Brain size & cortical thickness

27
Q

Types of MRI

A

MRI
FMRI
DTI

28
Q

How do FMRI work?

A

Uses blood oxygenated level dependent (BOLD)

It uses the change in ration of oxygenated to deoxygentated hemoglobin in the blood as direct measure of changes in location of neural firing

29
Q

Two direct measures rely on changes in oxygen levels in the brain upon firing of neurons. What are they?

A

NIRS & FMRI

30
Q

How do DTI work?

A

Uses the direction of water diffusion in brain tissues to reveal location & orientation of white matter tracts.

Water molecules move randomly

Water diffuses differently around white & gray matter; not easily diffused in gray matter & moves in different directions, move more quickly for white matter.

31
Q

Water is said to move differently around gray & white matter. Explain

A

It is not easily diffused around gray matter & moves in different directions

It moves more quickly around white matter

32
Q

List 5 advantages of MRI

A

Non-invasive due to its use of nonionizing radiation

Safe, flexible & fast data acquisition

Can take up to 5 minutes to acquire a single high-resolution scan showing structure of whole brain

4-8 mins for FMRI- localization

Can measure deeper structures compared to NIRS

33
Q

List 5 disavantages of MRI

A

Resource intensive: cost per hour, time & experience required

Some children cannot be scanned

Loud scanner noise

Participants have to remain still for 5-10 mins

Head movement issues

34
Q

Which direct measures are sensitive to movements?

A

MRI & EEG

35
Q

One issue with using MRI scans for infant studies is that children have the tendency to move their heads during scanning.

How can this be addressed?

A

Dummy scanners in which children are habituated to the scanner environment before the actual scan.

A movie can be played while the child is in the scanner

36
Q

What are methodological issues in brain studies when comparing children and adults?

A

How can brain activity related to age (maturation/growth) be dissociated from that related to performance?

37
Q

One methodological issue when studying brain activity is how can it be distinguished between age-related changes and performance related-changes.

Name three approaches that can be done to address this as proposed by Casey

A

Parametric Variation
Post-Hoc grouping
Correlation

38
Q

Describe parametric variation when distinguishing brain changes related to age and those related to performance.

A

Varying the difficulty of tasks.

Children and adults can be compared on similar or different performance levels.

e.g. memory tasks or visual search

39
Q

What is a disadvantage of parametric variation?

A

Varying task difficulty is not possible with every task

40
Q

Describe the correlation approach when ascertaining the causes of brain changes (i.e. age vs. performance)

A

Age and performance are correlated with brain activity data which allows:

Which brain regions are predominantly correlated with age (maturation) changes

Which brain regions are predominantly correlated with behavioural performance

41
Q

Describe the post-hoc approach

A

Children and adults with similar performances (matched)
Children and adults with different performances (non-matched)

42
Q

Schlaggar et al. 2002 used a post-hoc approach to determine whether brain activity changes were due to age or performance.

What were his findings?

A

Performance related regions = no differences between matched groups, but significant differences between non-matched groups

Age-related regions: different activities in both groups

43
Q

Schlaggar’s study consisted of three steps. Describe them.

A

Step 1: Develop comparable tasks (i.e. visual lexical processing) – single word processing task

Step 2: Voxel by voxel ANOVA
Within subject = time
Between subject = age

Step 3: are differences due to maturational stage or slower/inaccurate performance of children?

44
Q

In Schlaggar’s study, a voxel by voxel ANOVA was conducted. What were the results

A

Main effect of time: groups had similar activations of regions: left frontal and left extrastriate cortex

Interaction effect of time x group: children & adults differed in their activations

45
Q

What were some criticisms of the study by Schlaggar?

A

Did not measure baseline
Adults have more experience, so how can this be controlled?

46
Q

What is a voxel by voxel ANOVA?

A

It is an ANOVA that assess the activities of different segments of the brain.

The voxels are compared at baseline and after administration of tasks

47
Q

What is the general development of brain structure from birth to adulthood?

A

No major cerebral volume change after 5 years

Increases in cortical gray matter during the first years of life. After that there is a decrease until about 12 years.

Increases in cortical white matter in infancy and childhood until adulthood.

However, there are regional variations

PSY4035 (9 decks)

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