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KHA452 > Week 3 - Brain Stimulation > Flashcards

Week 3 - Brain Stimulation Flashcards

1
Q

What are some non-invasive forms of brain stimulation?

A

Transcranial Magnetic Stimulation (TMS)

Transcranial Direct Current Stimulation (tDCS)

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2
Q

Why is transcranial magnetic stimulation (TMS) so useful?

A

Non-invasive

Excellent temporal specifity

Ok spatial specificity (intensity-dependent - coil selection important)

Can be used in conjunction with motor tasks/cognitive tasks to actually explore the neural mechanisms of behaviour

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3
Q

What adverse events have been reported for transcranial magnetic stimulation?

A

Mild transient headache

light headedness/fainting

Nausea

Seizure

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4
Q

What are the uses of transcranial magnetic stimulation?

A

Assessment

  • corticospinal exciability
  • Intracortical inhibition
  • Connectivity

Disruption

Modulation

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5
Q

How is average corticospinal excitability calculated via single-pulse TMS?

A

MEP (mV) averaged over a number of stimulations

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6
Q

What is the principle of Electromagnetic induction by Michael Faraday 1831?

A

Production of a voltage across an electrical conductor due to its dynamic interaction with a magnetic field

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7
Q

What happens following a stroke?

A

Ipsilesional hemisphere is reduced

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8
Q

What further suppresses the ipsilesional cortext?

A

Interhemispheric inhibition (via the corpus callosum) from the contralesional to ipsilesional hemisphere

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9
Q

What did Fregni et al find in a small study of 15 chronic stroke patients?

A

Daily low frequency of rTMS to the contralesional hemisphere for 5 days resulted in reduced excitability of the contralesional M1

Improves paretic hand function compared to control group, with effects lasting up to 2 weeks after completion of the treatment

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10
Q

What did Ackerly et al find in a study of stroke patients?

A

A single session of cTBS suppressing the contralesional hemisphere resulted in a deterioration in paretic hand function

suggests that the contralesional hemisphere may play a role in the recovery of hand function after stroke in some patients, possibly via ipsilateral descending pathways

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11
Q

How are motor symptoms of Parkinsons treated with TMS?

A

HF (high freq), rTMS to SMA or M1

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12
Q

How does TMS treat depression associated with parkinsons disease?

A

rTMS to DLPFC (dorsal lateral prefrontal. cortex)

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13
Q

What is dystonia?

A

Problems with loss of inhibition or excessive plasticity

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14
Q

How can dystonia be treated with TMS?

A

LF (low frequency) rTMS (or cTBS) to try and reset levels of inhibition and counteract excessive plasticity (M1, PMC, SMA, S1, Cbm)

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15
Q

Is TMS effective for treating dystonia?

A

Insufficient evidence to recommend rTMS as a therapeutic tool

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16
Q

Is TMS effective in treating motor symptoms of parkinsons disease?

A

Not strong evidence for treatment of motor symptoms

17
Q

Is TMS effective in treating the depression associated with parkinsons disease?

A

Probable efficacy in treating depression associated with PD

18
Q

What area of the brain is involved in movement preparation and organisation of self-initiated movements?

A

SMA (supplementary motor area)

19
Q

What brain regions can be targetted by TMS to reduce tic severity of people with Tourettes?

A

Some evidence for LF (low frequency) rTMS to SMA reduces tic severity

20
Q

What is a much better alternative than ECT when treating treatment-resistant Major Depressive Disorder?

A

TMS

21
Q

What are the side effect of Transcranial Direct Current Stimulation?

A

Tingling, itching redness

22
Q

What is the typical time of stimulation for tDCS?

A

20 min

23
Q

What is transcranial direct current stimulation (tDCS)

A

Induction of LTP-like of LTD-like plasticity through

1) shifts in the membrane potential of underlying tissue
2) changes in synaptic-activity that mimic LTP and LTD processes

24
Q

How is tDCS different from TMS?

A

tDCS and other electrical current stimulations can only be used to induce neuroplasticity - they do not meaure excitability or inhibition in regions or circuits

25
Q

What is used to assess the physiological outcome of tDCS (e.g increase in excitability of M1) or look at the behavioural effect of tDCS (clinical, cognitive, affect etc)

A

TMS (suprathreshold stimulation)

26
Q

The volume of grey matter in the brain steadily declines across the life span. What is this a result of?

A

Not a result of cell death,

but lower synaptic densities in older adults

27
Q

What needs to be established before we can start to investigate the highly complex and multifaceted relationships between the changes in cortical excitability and behaviour?

A

The fundamentals of non motor tDCS need to be established

28
Q

What is electron doping?

A

The use of brain stimulation (mainly electrical stimulation) to enhance cognitive (and motor) performance in the healthy population

29
Q

TMS has primarily studied what brain area?

A

Primary motor cortex (M1)

30
Q

As the intensity of TMS declines quickly with distance from the coil, what is usually assumed?

A

That neural stimulation is limited to the cortex and superficial subcortical white matter

31
Q

What happens when M1 is stimulated by TMS?

A

A motor provoked potential (MEP)

Produces a descending activity in the corticospinal pathway that activates muscles on the opposite side of the body and produces a physical twitch

32
Q

What is the purpose of delivering pairs of pulses rather than a single pulse?

A

To study intracortical inhibitory and excitatory circuits

33
Q

How can TMS assess inputs to M1 from other areas?

A

By observing how the MEP (motor provoked potential) is modulated by a preceding stimulus, either a magnetic pulse applies over a different cortical area or a stimulus activating afferents from various sensory modalities

34
Q

What protocols can induce long-term changes in cortical excitability that are a result of synaptic plasticity?

A

Repetitive TMS in the form of short or long trains, regular or patterned or associated with diverse cortical or sensory stimulation

35
Q

What is the rational use of non-invasive brain stimulation (TMS)?

A

Provide additional benefit to conventional treatment

36
Q

How does TMS induce long term potentiation?

A

Short period of high-frequency repetitive stimulations

37
Q

How does TMS induce long-term depression?

A

Low frequency stimulation

38
Q

How many rTMS sessions are required for depression remission?

A

up to 6 weeks

at least 20-30 sessions

KHA452 (10 decks)

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