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PSY neur 17 > W3/4 signalling, EEG, MEG, fMRI, TCS > Flashcards

W3/4 signalling, EEG, MEG, fMRI, TCS Flashcards

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1
Q

action potentials info

A

cell body with dendrites receive signals
action potential goes through axon

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2
Q

action potential =

A

sudden change in electrical properties of neuron membrane in an axon

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3
Q

axon

chemical signalling

cleft =

A

axon terminals release Neurtransmitrs (NT) into synaptic cleft
- protein receptors in dendritic membrane of postsynaptic neuron bind to NT
- results in synaptic potential (created)

c = space between neurons

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4
Q

electrical signalling

A

through voltage-gated ion channels
- sodium NA positive charge
- potassium K positive charge

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5
Q

electrical signalling steps

A
  1. resting state -70mV
  2. NT bind to dendrites - dentrites more positive
  3. if strong enough then cell depolarises (above -50mV)
  4. Na+ channels react to voltage change, open and let Na+ into axon (ion-channels)
  5. lots of Na+ makes positive potential = firing
  6. Na channels close, K+ opens, potassium pumping out to repolarise
  7. refractory period undershoot
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6
Q

Single-cell recordings

A
  • small electrode implanted into axon
  • directly measure axon potential
  • via number of spikes per second to stimulus

invasive, anaesthesia

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7
Q

How do neurons code information?

spiking

A

spiking/firing rate = number of action potential propagated per second
spiking - informational code carried by neuron

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8
Q

Rate vs temporal coding

A

R = neurons encode information in rate of neural firing
- eg single-cell recording increase firing when stimulus

T = synchony with other neurons, neurons encode info in synchrony of neural firing
eg. multi-cell recording

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9
Q

Grandmother cell is

Oprah

A

= hypothetical neuron that responds to specific concept/object
- local representation, know what she looks like

Spiking rates increase when stimuli of Oprah face, name, not other celeb

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10
Q

selective responsing reflects:
person + landmark

A

association between person and landmark
–> neurons are involved in learning+memory

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11
Q

PROS + CONS

Single-cell recording

A
  • very invasive, surgery
  • very localised 1 axon at a time
  • translational
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12
Q

EEG

Electroencephalography

what it measures

A

patient wears electrode cap
- measures activity of multiple neurons at one time
- rhythmic oscillations over time, waves at different frequencies
- rate of escalation correlates with behavioural activity

summed electrical potentials from neurons

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13
Q

Electrode locations

A

distance 10% to 20% away from each other
- letter = location (P parietal)
- number = hemisphere (odd left, even right)

control electrodes on face/ear

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14
Q

signal is sensitive to…

Dipoles

A

= a pair of positive and negative electoral charges separated by small distance
- as positive ions flow into dendrite, space outside is more negative (dendrite currents)
- population of neurons aligned direction, firing in synchrony, dipoles can be summed together

perpendicular are read on EEG

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15
Q

EEG signal

A
  • neurons aligned in similar direction and firing synchrony
  • dipoles can be summed together
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16
Q

EEG during sleep

A

beta waves = alert
alpha waves = relaxed
stage 1 2 - sleep spindles
stage 3 4- delta waves
REM sleep - small

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17
Q

ERP

amplitude

event r p

A

using EEG to study ERPs
linking average change in EEG signal to the timing of a cognitive event
- signal up = positive (more activity/performance)
- down = negative
- averaged over many events/trials (increase signal to noise ratio)

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18
Q

what is noise?

A

Random neural firing
outside interference
- many trials = less noise = more signal

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19
Q

ERP polarity and timing

2 names

Study These Flashcards
A

Pxxx= positive peak ‘xx’ ms after event
Nxxx = negative peak ms after event
- some are exogenous = stimulus properties
- others endogenous = persons reaction

20
Q

P300

Study These Flashcards
A

oddball paradigm = brain responds to unexpected stimuli
- endogenous reaction based
- eg cats, then snake shows up (snake is p300)
- beep beep boop

21
Q

MEG - magnetoencephalography

Study These Flashcards
A

measures magnetic fields associated with electrical activity in brain
- more sensitive to activity at sulci, than gyri

good temporal resolution

22
Q

How MEG works

ERF

Study These Flashcards
A

dipoles have magnetic field perpendicular to direction of dipole
- dipoles run parallel to skull in sulci
- dipoles perpendicular to skull in gyri

CAN ONLY READ PARALLEL at Sulci where magnetic field leaves the skull

event related field

23
Q

Spatial vs temporal resolution

Study These Flashcards
A

Spatial = where
Temporal = when
in brain

24
Q

MRI

Magnetic resonance imaging

Study These Flashcards
A
  • collection of static images
  • slices in sagittal, coronal, horizontal planes
25
MRI - how does it work
soft tissue in body is water based - H2O molecules have single protons in hydrogen atoms, weak magnetic field - magnet attracts hydrogen - when pulse goes away, hydrogen atoms turn again - (radiofrequency pulse)
26
Different tissue types
curve - area of greatest difference between curves - water appears dark on MRI - fat appears bright
27
MRI steps
1. magnetic fields of protons are arranged randomly 2. MRI strong magnetic field - some protons align 3. radio pulse moves protons, then relax, depends on tissue
28
fMRI
functional mri - active brain activity during tasks - compared to controls - compare relative differences in brain between 2or more conditions | brain activity baseline task subtracted from activity in experiment
29
BOLD signals are | what does neural activity consume?
Blood Oxygenated Level Dependent Signal - fmri captures it - indirect measure of neural activity - neural activity consumes oxygen - oxyhemoglobin to deoxyhe - oxygen increases, more activity, more blood | HIGHER BOLD SIGNAL = GREATER PROPORTION OF OXY TO DEOX BLOOD = MORE ACTI
30
Hemodynamic response function
using more oxygen, more blood to area peaks at 6-8 seconds (overcompensation)
31
voxels
3D pixel
32
1997 kanwisher, mcdermott FFA
Fusiform face area subjects viewed faces and objects faces more activity than objects FFA part of the fusiform gyrus
33
fMRI analysis needs: | weaknesses too
1. correct for head movement 2. normalise data brain scans onto reference template 3. smoothing, increase signal to noise ratio 4. analyses with t-test | activation doesnt mean processing shows regions
34
fNRIS is
fuctional near infrared spectroscopy - using near-infrared to measure how light scatters - scalp | good for children, portable
35
PET is
Positron emission tomography spatial - radioactive tracer injected in tissue - scanner detects radiation in different areas | example - alzheimers - accumuluate certain areas
36
Lesioned brain examples | hard to...
- stroke - neurosurgery - tumour - head injury - neurodegenerative disorders - hard to locate lesion (tumour/swelling) --> areas can be active on fMRI but not impact performance
37
# Lesion studies Single dissociation
- patient can do task A, but not task B - can infer lesion area involved with task B - might be task demand or resource | more severe brain damage, can do easy, not hard task
38
# Lesion studies Double dissociation
patient 1 can do task A, not B patient 2 can do task B, not A - two lesion patients complementary profiles - more useful
39
what methods used for: Simulated lesions
TMS - transcranial magnetic stimulation tDCS - transcranial direct current stimulation
40
TMS
- coil carries electric current, produces magnetic field - this field induces current into neurons - neurons fire (action potentials) - simulated lesion/interference | temporary current in cortex 1cm ## Footnote treatment in major depression
40
TMS control conditions
- Best = same region in critical vs non-critical time period or a different task - Medium = Critical vs noncritical brain region - Worst = Sham (pretending, above the head, placebo)
41
tDCS
weak electric current between two stimulating electrodes - anodal - positive (increases performance) - cathodal - negative (decreases performance) | one electrode at ROI, other not
42
How neurotransmitters work
synapse = where axons and dendrites meet - axons away - dendrites receive **- excitatory effect** - postsynaptic neuron more positive, action potential **- inhibitory effect** = postsynaptic neuron more negative
43
# tDCS cathodal negative
- hyperpolarises neurons - decrease excitability - reduce concentration of glutamate - less excitation of neurons
44
# tDCS anodal positive
- depolarises neurons - increase excitability - reduce inhibitory GABA - less inhibition of neurons

PSY neur 17 (11 decks)

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