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Psychology - CN > Lecture 7- TMS > Flashcards

Lecture 7- TMS Flashcards

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1
Q

first person in the UK to report magnetically induced phosphenes

A

Thompson

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2
Q

How does TMS work?

A

Pass an intense,rapidly varying, electrical current through a set of coils

Causes a strong but transient and rapidly changing magnetic field over a region of the scalp (2 Telsa)

This magnetic field induces a rapidly changing electrical field in the underlying brain tissue

Results in an extraneous flow of current that interacts with local neural processing
Rises (very brief pulse; 0.1ms) and dips within 1ms

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3
Q

Two types of coil

A

Round coil

Figure of 8 coil

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4
Q

Round coil?

A

More general disruption

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5
Q

Figure of 8 coil?

A

Combination in the middle makes it more focal

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6
Q

What is Barker’s model?

A

If magnetic field is parallel to axon, no induced current

If perpendicular, depolarisation can occur = disruption

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7
Q

Disruptive mode?

A

Strong stimulation
Neural noise/brain lesion
e.g. Disrupting language areas while reciting

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8
Q

What do we need to think about when designing TMS experiments?

A

People blink/move eyebrows/move shoulders

The noise TMS produces (need sham control condition)

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9
Q

Productive mode?

A

Weaker stimulation
Can facilitate activation

Produces phosphenes/hand movements

Usually over primary areas

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10
Q

TMS is what type of technique?

A

Interference technique

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11
Q

TMS over primary motor area? (M1)

A

TMS depolarizes corticospinal tract neurons

Evokes contralateral hand muscle movements
as measured by MEP

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12
Q

Is TMS constrained to stimulation site?

A

No…

Spreads into connected and functionally coupled areas (inc. subcortical areas)

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13
Q

Allen et al

A

(2007)

Short rTMS trains (1-4s) at various frequencies in cat visual cortex

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14
Q

In Allen et al’s (2007) study, there was an enhancement of spontaneous neural activity of up to ____ lasting up to ___ after TMS

A

200%

1 minute

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15
Q

In Allen et al’s (2007) study, activity in the visual cortex evoked by sinusoidal gratings was suppressed up to __ after TMS and gradually recovered after ___

A

60%

10 minutes or longer

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16
Q

In Allen et al’s (2007) study, they found that effects of TMS depend on ____ and ____

A

frequency and duration

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17
Q

Based on Allen et al’s (2007) study, TMS disrupts the ___ relationship among ___ responses
Evidence?

A

phase
neural

Neural spikes were decoupled from ongoing oscillations for 30s across all frequency bands

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18
Q

Based on Allen et al’s study, what type of coupling is there between TMS-evoked neural responses and changes in cerebral haemodynamics?
Evidence?

A

Tight!

TMS led to initial increase and longer decrease in tissue oxygenation

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19
Q

Paus et al (1997)
Which method was CBF measured?
There is a ___ relationship between changes in CBF and ____ at the stimulation sight

A

PET
Positive
Number of trains

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20
Q

Temporal resolution of TMS in behavioural studies

A

At least 10ms (Ashbridge et al, 1997)

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21
Q

Temporal resolution?

A

Milliseconds to Seconds (depending on number of pulses)

Also depends on recovery rate of neural area

22
Q

Ilmoniemi et al (1997)

A

TMS applied to left sensorimotor area

As measured by EEG:
Response spread to adjacent ipsi motor area within 5-10 ms
Response spread to homologous area in opposite hemisphere within 20 ms

23
Q

There is a difference between physiological TMS and ___ TMS effect on behaviour

A

Functional

24
Q

Spatial resolution?

A

Not as good as fMRI but better than MEG and EEG

25
Q

Who ‘invented’ TMS?

A

Barker (1984)

26
Q

Stimulation depth?

A

Cannot stimulate medial or sub-cortical areas

27
Q

How can you elicit moving phosphenes?

A

Stimulate V5

28
Q

Repetitive TMS use and general findings

A

Behavioural tests can be administered during and after the rTMS

rTMS can either enhance or impair performance on these tasks

29
Q

Single pulse use

A

Deliver single pulse to specific brain area at a specific time during a task

Provides greater temporal resolution in assessing role of area in that task

30
Q

Three types of rTMS

A 
High frequency (typically online) 
5 pulses at 10Hz

Low frequency (typically offline) (before)
1 Hz rTMS for 10/15 minutes
Lasts for 5-10 minutes

Theta burst (very high burst) 
50 Hz
Effects last a lot longer
31
Q

Critical time for TMS delivery coincides with time at which ____ can be recorded which is earlier than ___

A

single unit responses

ERPS

32
Q

Two types of control in TMS experiments

A

Control task

Control site

33
Q

fMRI guided TMS neuronavigation

A

Best but most expensive method

Have PS complete the same task in fMRI and TMS

Can stimulate (with TMS) the most activated area (in fMRI)

34
Q

MRI guided neuronavigation

A

Anatomically identify the area of brain which you want to stimulate based on MRI

35
Q

TMS neuronavigation based on group coordinates

A

localise brain region via coordinates from other fMRI paper/study
- doesn’t take into account individual anatomy

36
Q

TMS based on the 10-20 EEG system (anatomical landmark approach)

A

Conduct the same measurement as one would do for EEG

- not very precise

37
Q

Functional TMS localizer

A

For each PS, the site at which TMS provides maximal disruption in a different task is determined

38
Q

What did Sack et al find?

A

(2008)
Compared fMRI, MRI, group coordinates and 10-20 system neuronavigation
Determined how many PS were needed to gain sig. result

fMRI: effect size = 1.13, only need 5 PS for sig. effect
MRI: 0.82, only need 10 PS
Talairach/group coordinate: 0.67, need 13 PS
Landmark/EEG (P4): 0.3 - needed 45 PS

39
Q

Silvanto et al

A

(2007) Patient GY

Blindsight patient but could detect and localise stimuli in the blind field
Shows two pathways:
1) Retina –> PVC
2) Brainstem –> Higher visual areas

TMS applied over V5

GY experienced TMS induced phosphenes in his blind field following bilateral stimulation
THEREFORE

V5 is necessary for awareness

40
Q

Gobel et al (2001) (double digits)

When TMS is applied over left angular gyrus, much ___ ___ for numbers larger than ___

A

larger RT

65

41
Q

Gobel et al (2001)

There was no sig effect of TMS on double digit numbers when TMS was applied to ____

A

Left supra-marginal gyrus

42
Q

Gobel et al (2001) (single digits)

When TMS is applied over left supra-marginal gyrus, there is a significant ____ in ___ for numbers larger than ___

A

increase
RT
5

43
Q

Gobel et al (2001) (single digits)

There was no sig effect of TMS on single digit numbers when TMS was applied to ____

A

Left Angular gyrus

44
Q

The size of the magnetic field generated with a TMS coil can be up to…

A

2.5 Tesla

45
Q

Which of these frequencies is NOT typically used when rTMS is applied to human subjects:

5
10
50
100

A

100

46
Q

What did the TMS experiment with the patient GY show?

A

GY experienced TMS induced qualia in his blind field, only with bilateral stimulation

47
Q

In Goebel et al. (2001) ____________ number comparison was significantly impaired when rTMS was applied over ___________________.

A

double digit/left angular gyrus

48
Q

Grotheer et al (2016)

A

TMS over right Number Form Area: gave them 2 pulses at 0ms and 100ms after stimulus presentation, found a decrease in accuracy for both letters and numbers.

TMS over ILO (control): no significant effect on numbers or letters

49
Q

O’shea (2007)

A

Wanted to know if changes in brain activation after stroke are due to altered structure or reorganisation of function

Two tasks: select (harder) or execute
Select: more activation in premotor cortex compared to execute

1hz of TMS over LD PMC: increase in BOLD in right PMC (compensatory) (only for selection task)

1Hz of TMS over sensorimotor cortex: no increase in BOLD in right PMC

THEREFORE
Changes seen in stroke patients in right dorsal PMC are due to reorganisation of function

50
Q

What did d’Arsonval do?

A

Presented the first report of magnetically induced phosphenes in human subjects by stimulation of the retina, not the cortex

Painless stimulation of the nervous system
by electromagnetic induction

51
Q

Effects of a single TMS pulse may last up to ___ (but not all ___ ____)

A

70ms

physiologically active

Psychology - CN (9 decks)

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