TMS tDCS rTMS spTMS Flashcards
- Functional principles of TMS and TDCS …
TMS :
- electric current that is flowing through a wird does generate a magnetic field
- the field runs perpendicular to the current. ( parallel)
- the greater the change in the current, the greater the magnetic field.
- TMS induces a secondary current to flow that enters the brain.
- The effect of TMS is dependent on the activity state of the brain region, that the TMS is applied to.
If the region is active - TMS disrupts
If the region is inactive- TMS makes the region active
- TMS coils, protocols, and associated risks
associated risks:
- epileptic seizures ( especially if someone has epilepsy those seizures may be triggered by TMS).
- Kindling - repeated regular application of the stimulus can add up ( culminate) to seizures.
Set up of TMS :
- 2 coils
1 - power pulse generating unit
2 - Electromagnetic Stimulating Coil
- Spatial specificity of TMS,
behavioral and neural effects of TMS
TMS has a relatively high spatial resolution better than PET and EEG fMRI, MRI …,
- no deeper regions can be reached ( only cortical areas)
- -> Though stimulating cortical areas can also cause a chain reaction which leads to deeper areas being stimulated.
- Combination of TMS with neuroimaging,
interpretation of effects of TMS
–> TMS needs to be combined with fMRI in order to proof that there is activation in the area that was targeted by the TMS.
- Visuospatial manipulation study.
- first step is finding out where it makes sense to apply TMS stimulation.
- mental clock task was used
Cortical activation during mental clock test: most prominent in posterior parietal lobes of both
hemispheres
o Confirmation of findings that certain imagery conditions produce increases in activity
in primary visual areas only to a small extent
● Reverse inference: activation of PFC associated with attentional demand involved in different
kinds of mental imagery and working memory tasks
o PFC strongly involved in processing of spatially coded material in imagery domain.
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- Dis-/advantages of TMS compared with
‘real’ lesion method (Task 8)
- advantage:
- grouping can be done more easily
- larger amounts of participants can be researched on
- the inhibition of certain brain areas can be done intentionally and controlled
- non invasive
- several ( reversable lesions) can be researched on one participant.
Disadvantage:
- TMS does not reach the deeper areas
- can not realls inhibit the whole functioning of one area but only slow its reaction time.
rTMS
- Repetitive TMS : Capable of modulating the excitability for longer than a single TMS application
–> more powerful in detecting the necessity of a region.
- is not powerful in the regard of timing.
-
spTMS
- single Pulse TMS
- -> Delivers Pulses at different time windows.
- the timing of the pulse is especially important in spTMS
–> delivers pulses in different time windows.
Visospatial Manipulation with TMS
Comment on the outcome :
The most prominent differences in cortical activation during the detection of angles compared to that of variations of color were found in the superior IPS bilaterally
Comment [FD20]: This null result on
the control task is very important.
–> It shows that disruption of parietal cortex left
performance intact for one task but not the
other, even though the stimulus material
was identical. The only difference was the
cognitive processes (color vs. angle), so
TMS effects were specific to that cognitive
process.
–> Reaction time differences are due to TMS on higher functions not on motor functions.
Findings :
Both Hemispheres were active, the one compensated for the other . Therefore there was no effect of TMS visible.
Follow up study
- rTMS is applied to left side of the brain
- the right side of the brain was manipulated with tripel pulse TMS .
–> The reaction time was increased. when the right side of the brain took over.
P3 = left P4 = right
