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Psyc 202 > Lecture 1- What is cognitive neuroscience? > Flashcards

Lecture 1- What is cognitive neuroscience? Flashcards

1
Q

What is cognitive neuroscience?

A

The study of the biological processes underlying cognition

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2
Q

What are neuroscience methods?

A
  1. Neuroanatomy
  2. Invasive neurophysiology: measurements from inside the brain
  3. Non-invasive methods: measurements of brain activity made from outside the brain
  4. Computer simulations
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3
Q

What is meant by temporal resolution?

A

the precision of measurement of brain activity in time

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4
Q

What is meant by spatial resolution?

A

the precision of measurement of brain activity with respect to space

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5
Q

What is meant by invasive techniques?

A

the degree to which the brain is directly and physically affected by the technique

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6
Q

What does the hypothalamus do?

A

Regulates functions that are essential for maintaining the normal state of the body (homostasis) and reproduction. Controls hormone release

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7
Q

What is the thalamus?

A

Relay station in the pathways from sensory receptors to the cortex

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8
Q

What does the brainstem do?

A

Connects the cerebrum with the spinal
Cord, carrying signals between the rest of
The brain and the body

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9
Q

What is the cerebellum related to?

A

Sensorimotor control and learning; other cognitive functions such as language

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10
Q

What does the cerebral cortex do?

A

Integrates information from across the brain and is the seat of most cognitive functions

Awareness, perception, memory, attention, planning, language, emotions, consciousness.

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11
Q

What connects the hemispheres?

A

The corpus Callosum

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12
Q

What separates the two hemispheres?

A

Longitudinal fissure

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13
Q

What are gyri?

A

The ridges of the brain

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14
Q

What are sulci?

A

The grooves of the brain

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15
Q

What is the gyrus surrounded by?

A

Two sulci

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16
Q

What is a very deep sulcus?

A

A fissure

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17
Q

What are the two main fissures?

A

Central fissure

Lateral fissure

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18
Q

What are the location descriptors of the brain?

A

Anterior
Dorsal (Top)
Ventral (Bottom)

Medial –>

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19
Q

What is computed tomography?

A

An early method of studying the brain which creates a 3D reconstruction of the brain .
It has a relatively low resolution (1cm)

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20
Q

What is Magnetic Resonance Imaging (MRI) ?

A
  • Essentially measures the presence of water in the brain
  • Specifically: the protons making up the nucleus of the hydrogen atom in H20
  • A combination of strong magnetic field + ratio pulses leads to protons emitting radio signals
    MRI picks up these radio waves
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21
Q

What to MRI images show?

A 
High-resolution structural images that show 
Grey matter (made of cell bodies "processors") 
White matter (axons "cabling")
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22
Q

What is Diffusion Tension Imaging (DTI)?

A
  • A variant of MRI
  • MRI can be tuned to detect diffusion (movement) of water, diffusion in the brain is anisotropic (restricted)
  • Myelin sheath surrounding axon produced a tight lipid (i.e. fatty) boundary
  • Water diffusion is greatest in axons
  • Reveals long range connections
  • High resolution structural images of long-range axons running in white matter (so called tracts)
23
Q

What are lesion studies?

A
  • Historically the oldest method of cognitive neuroscience (Broco, Wernicke)
  • Damage to the brain area leads to cognitive impairment
24
Q

What are the pros and cons of lesion studies?

A

Pros:
- Artificial ablations are
precise (usually in animals)
- Unequivocal evidence that damaged area participates in certain cognitive function

Cons:

  • Spatially imprecise when caused by injury when caused by injury or disease
  • Does not reveal fully how or where function takes place
25
Q

What are single and multi-cell reocrdings?

A

Extracellular recordings of action potential from one or many cells

Usually in animals: visual and auditory processes

In humans, occasionally: electrodes implanted in epilepsy patients

26
Q

What increases local blood flow to blood vessels in the brain?

A

Neural activity increases local bloodflow (with delay)

27
Q

What is Positron Emission Technology (PET)?

A
  • Measures changes in blood flow
  • Usually between control and experimental condition
  • Radioactive isotope injected into blood
  • As isotope decays, it generated gamma rays (photons) which the PET instrument detects
28
Q

What is Functional Magnetic Resonance Imaging (fMRI)?

A
  • Indirect: measures blood flow with same principle as MRI
  • Blood Oxygenation Level Dependent (BOLD) Signal
  • Sluggish: response peaks several seconds after stimulus onset
29
Q

What are the pros and cons of PET and fMRI?

A

Pros:

  • Good spatial resolution : PET: 1cm voxels (i.e., 3D pixels) fMRI: 3-6 mm
  • Access to all parts of the brain

Cons:

  • Poor temporal resolution: PET 1 min, fMRI 5 seconds
  • Indirect: measures blood flow rather than neural activity directly
30
Q

What do electroencephalography (EEG) and Magnetoencephalography (MEG) do?

A

Measure neural activity directly

31
Q

What is the pyramidal cell?

A
  • The majority of cortical cells are pyramidal cells
  • Their main feature is the apical dendritic tree
  • Pyramidal cells are logically aligned with each other
32
Q

What is the electrical circuit of the pyramidal cell?

A

Synaptic currents: positive ions flowing into dendrite

Primary current: current flowing along dendrite

Leak current: current leaks out along the dendrite

Secondary (volume) current: completes the circuit

33
Q

How are cortical cells organised?

A

Cortical cells are organised into columns, with multiple aligned apical dendrites, perpendicular to cortical surface.

Signal entering a column activates all the cells in the column

Cells within a column are synchronously active.

34
Q

How are currents of cortical cells summed?

A

Nerve cells seldom become active alone.

Nearby cells and columns tend to become synchronously active

A large number of aligned pyramidal neurons in columns sums up to large primary and volume currents.

EEG/MEG reflect these currents and the activity of neural masses.

35
Q

What is the basic physics behind EEG/MEG?

A
  • Positively charged ions repel each other
  • Electric charge is proportional to number of ions
  • If two regions have unequal charge, there is electric potential between them.
    Connecting the regions causes electric current. This measures the electric potential
  • Electric current causes a magnetic field around the current (Maxwell’s equations)
  • The right-hand rule gives the relationship between the current and the magnetic fields
  • Primary currents in the brain cause magnetic fields. This is measured in MEG.
36
Q

What other techniques are closely related to EEG?

A
  • Electrocoticography (ECoG): electric field potential measurements from the cortical surface
  • Local field potential (LFP): electric field potential measured from inside cortex
37
Q

What activity does MEG pick up?

A
  • MEG picks up cortical activity, but very little from deeper in the brain.
  • MEG “blind” to activity in gyri.
    It is sensitive to primary currents in sulci
38
Q

EEG and MEG Oscillation Bands

A
  • Both MEG and EEG show oscillatory activity in different frequency bands
  • Cognitive and arousal states are associated with characteristic oscillations
    Correlations between oscillations in different cortical regions reveal functional connectivity maps of the brain.
39
Q

Time Frequency Analysis (TF)

A
  • EEG/MEG signals contain many frequencies that change during a cognitive task
  • The amplitude of an oscillation is its power
    You can code power as colour, e.g. high amplitudes in red, low in blue
  • TF analysis is plotting power in time-frequency plane.
40
Q

Where do you measure MEG/EEG from?

A

The surface of the scalp= far away from brain activity

41
Q

What are the problems of localising activity with EEG and MEG?

A
  • EEG/MEG responses do not directly reveal locus of generation
  • Forward problem: calculate field pattern when primary current (sources) known.
  • Inverse problem: calculate primary current from field pattern.
42
Q

What are the solutions for the problems with EEG and MEG?

A
  • Simplifying assumptions: assume the primary current is a single point (dipole)
  • Constrain solutions to the cortex on the basis of MRI
    Constrain solutions to activity map given by fMRI
43
Q

What are the Pros and Cons of EEG and MEG ?

A

Pros:

  • Very good temporal resolution (1ms)
  • Quite good spatial resolution
  • Can be combined with other techniques

Cons:

  • MEG sensitive to current orientation
  • MEG doesn’t see deep sources
  • Localization difficult and uncertain
  • EEG worse spatial resolution than MEG
44
Q

What are examples of Invasive Perturbations?

A

Cortical Cooling
Pharmacology
Direct Electrical Stimulation
Optogenetics

45
Q

Are invasive perturbations possible to use on humans? And what are some methods?

A

Yes

Direct stimulation
Drug research

46
Q

How are invasive perturbations used in epilepsy?

A
  • Direct stimulation used for mapping speech areas of epilepsy patients, to avoid these in operations to remove parts of cortex.
47
Q

What are non-invasive methods

A
  • Transcranial magnetic stimulation (TMS)

- Transcranial direct-current stimulation (tDCS)

48
Q

What is Transcranial Magnetic Stimulation?

A
  • Electric current in coil generates magnetic field
  • Magnetic field generates focal electric field in brain
  • This field depolarises neurons locally
  • This interferes with cognitive processing
49
Q

What are the Pros and Cons of TMS?

A

Pros:

  • Good temporal (10ms) and spatial (10 mm) reolsution
  • Harmless- acts like temporary lesion
  • Subjects act as their own controls

Cons:

  • Cortical effect: doesn’t reach deeper brain areas
  • Neurophysiological effect not clear
50
Q

What is Transcranial Direct Current Stimulation (tDCS)

A
  • In this method, positive, low-level current is induced between two electrodes: the anode and the cathode
  • This results in depolarization and action potentials under the anode
  • Hyperpolarization (inhibited activity) under cathode.
51
Q

What are the pros and cons of t(DCS) ?

A

Pros:

  • Cheap, portable, safe
  • Subjects act as their own controls
  • Clinical applications (e.g., depression, Parkinson’s)

Cons:

  • Poor spatial and temporal resolution
  • Cortical effect: doesn’t reach deeper brain areas
  • Neurophysiological effect not clear
52
Q

What technique would you use to get high spatial resolution?

A

fMRI, PET

To see which networks are performing cognitive task

53
Q

What are the perturbation methods and what do they do?

A

TMS and tDCS

They . test if specific region is part of network performing task

54
Q

What are high temporal resolution methods and what do they do?

A

MEG and EEG

To find out the time in order of events of the brain

Psyc 202 (7 decks)

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