Week 3 - Brain Stimulation Flashcards
(38 cards)
What are some non-invasive forms of brain stimulation?
Transcranial Magnetic Stimulation (TMS)
Transcranial Direct Current Stimulation (tDCS)
Why is transcranial magnetic stimulation (TMS) so useful?
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
What adverse events have been reported for transcranial magnetic stimulation?
Mild transient headache
light headedness/fainting
Nausea
Seizure
What are the uses of transcranial magnetic stimulation?
Assessment
- corticospinal exciability
- Intracortical inhibition
- Connectivity
Disruption
Modulation
How is average corticospinal excitability calculated via single-pulse TMS?
MEP (mV) averaged over a number of stimulations
What is the principle of Electromagnetic induction by Michael Faraday 1831?
Production of a voltage across an electrical conductor due to its dynamic interaction with a magnetic field
What happens following a stroke?
Ipsilesional hemisphere is reduced
What further suppresses the ipsilesional cortext?
Interhemispheric inhibition (via the corpus callosum) from the contralesional to ipsilesional hemisphere
What did Fregni et al find in a small study of 15 chronic stroke patients?
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
What did Ackerly et al find in a study of stroke patients?
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
How are motor symptoms of Parkinsons treated with TMS?
HF (high freq), rTMS to SMA or M1
How does TMS treat depression associated with parkinsons disease?
rTMS to DLPFC (dorsal lateral prefrontal. cortex)
What is dystonia?
Problems with loss of inhibition or excessive plasticity
How can dystonia be treated with TMS?
LF (low frequency) rTMS (or cTBS) to try and reset levels of inhibition and counteract excessive plasticity (M1, PMC, SMA, S1, Cbm)
Is TMS effective for treating dystonia?
Insufficient evidence to recommend rTMS as a therapeutic tool
Is TMS effective in treating motor symptoms of parkinsons disease?
Not strong evidence for treatment of motor symptoms
Is TMS effective in treating the depression associated with parkinsons disease?
Probable efficacy in treating depression associated with PD
What area of the brain is involved in movement preparation and organisation of self-initiated movements?
SMA (supplementary motor area)
What brain regions can be targetted by TMS to reduce tic severity of people with Tourettes?
Some evidence for LF (low frequency) rTMS to SMA reduces tic severity
What is a much better alternative than ECT when treating treatment-resistant Major Depressive Disorder?
TMS
What are the side effect of Transcranial Direct Current Stimulation?
Tingling, itching redness
What is the typical time of stimulation for tDCS?
20 min
What is transcranial direct current stimulation (tDCS)
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
How is tDCS different from TMS?
tDCS and other electrical current stimulations can only be used to induce neuroplasticity - they do not meaure excitability or inhibition in regions or circuits
