TMS: L1-2 Flashcards

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1
Q

what is TMS?

A
  • non-invasive

- creates virtual cortical lesions

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2
Q

what did removing hippocampus, parahippocampal gyrus and amygdala lead to (H.M)

A

anterograde amnesia

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3
Q

what does TMS do?

-currents

A
  • produces a rapidly changing magnetic field to induce electrical currents in the brain
  • currents depolarise neurons ini a small circumscribed area of the cortex
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4
Q

D’arsonval (1896) discovered what?

A

magnetic stimulation of the visual cortex can elicit phosphenes

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5
Q

how is the current pulse generated?

A

-capacitor is charged then suddenly discharged

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6
Q

whats rTMS

A

repetitive tms, fast pulses

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7
Q

what are the loading times and durations of rTMS

A

100-200μs and <1ms

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8
Q

the figure 8 coil generates what?

-where’s the strongest effect?

A
  • magnetic fields in the opposite direction = more precision
  • in the centre, 3-4mm radius
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9
Q

What does a single TMS pulse test?

A
  • disrupts a cognitive function, demonstrating its causal involvement (causality)
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10
Q

whats a way of injecting “neural noise”?

A
  • interfere with the process of interest at exactly the time window during which the regions is requires
  • regions don’t stop working completely, but are interfered
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11
Q

Amassian et al study

  1. what was the study
  2. what approach
  3. critical period
A
  1. 3 alphabetical letters as stimuli presented under difficult viewing conditions
  2. neural noise (rTMS)
  3. 40-120 ms affected letter detection
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12
Q

Amassian study: what was impaired

  1. left to right stimulation
  2. top to bottom stimulation
A
  1. letters in the contra-lateral visual field were impaired

2. stimulation above the reference line suppressed letters at the bottom of the display

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13
Q

‘visual mask’ study:

1. what did it test

A
  1. whether a visual mask can be masked using single pulse stimulation -> unmasking the stimulus
    - > TMS can be used to disrupt processing of stimuli, therefore it could disrupt processing of the mask, preventing the stimulus from becoming suppressed
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14
Q

‘visual mask’ study results

  1. no TMS
  2. TMS
  3. unmasking found at what ms

-> what can this inform us?

A
  1. 100ms SOA detection rate 0.37
  2. detection rate 0.9
  3. 60-140ms stimulation after the mask

-> time-course of processing

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15
Q

what is the virtual lesion approach?

A

using repetitive TMS to interrupt or enhance cognitive processing

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16
Q

what can be measured when applying repetitive rTMS?

A

whether and for how long a specific cognitive task is impaired

17
Q

what is the probing excitability approach?

- whats measured

A
  • test how responsive or excitable the motor cortex is during a cognitive task
  • if the motor cortex is required for a cognitive task it should already be activated when single-pulse TMS is delivered
  • how strongly the motor cortex reacts to the pulse
18
Q

probing excitability approach is measured by recording what, using what?

A

MEPs using the EMG -> electrical activity of muscles

19
Q

probing excitability approach

  1. area stimulated
  2. how MEPs are processed (results)
A
  1. central sulcus

2. MEPs for each stimulation and compare average MEPs between experimental conditions

20
Q

Eisenegger study:

  • results
  • evidence
A
  • stimulation of M1 during mental rotation elicited stronger MEPs as compared to baseline, reading aloud and silently
  • M1 more excitable during mental rotation
21
Q

Bode study:

  • study
  • results
  • > possibly..?
A
  • does involvement of M1 depend on strategy used?
  • MEPs equally high for mental rotation of all stimuli
  • hands lowest
  • > M1 more excitable because of adjacent brain regions?
22
Q

what is the paired-pulse approach?

A

two pulses delivered in brief succession

- one sub-threshold, the other supra-threshold

23
Q

Fitzgerald study

  1. study - define CSP
  2. results
A
  1. schizophrenia. - a period of suppression of tonic motor activity following descending excitatory activity
  2. compared to controls, patients with and without medication showed stronger responses to second pulse -> general deficits in motor inhibition
24
Q

clinical application of TMS

A
  • endorsed TMS as treatment for depression
  • 1 hemisphere stimulated -> depression is linked to imbalance of prefrontal activity between hemispheres
  • treatment is last resort
  • TMS debated as treatment for other mental disorders