neuroimaging

Question 1

fMRI terminology :
session
run
block
experiment

Answer 1

session: single participant time into the fMRI in a day without leaving the machine
can have multiple runs

run : single fMRi recording ( 5-12 min )
can have multiple blocks

block : fMRI recording to a specific continuous condition

Question 2

Advantages of fMRI

Answer 2

higher spatial resolution compared to other -_> allow for new types of analysis
non invasive –> high benefit low risk
easier to train people compared to other neuroimaging

Question 3

anatomical voxel

Answer 3

smaller than the fucntion

Question 4

spatial resolution, structural and functional voxels

Answer 4

spatial resolution : ability to detect differences, both structural and functional, across different location fo the map

for structural MRI
- spatial resolution means distinguishing afferent brainn areas ( the smallest structural change it can detect )
- voxel is smaller (0.05 to 1.5mm3)
pros: higher precision for restricted hypothesis
cons : low signal to noise ration, require more time for acquisition

functional MRI
- spatial resolution means the precision it can pinpoint activity on a map
- bigger voxel ( 2-3mm3)
pros: lower time , bigger noise to ration
cons: partial volume effect

Question 5

partial volume effect

Answer 5

in fMRI bigger voxel can cause the machine to record acticity of voxels form different structural tissues, functional regions and slices os belonging to the same voxels
solution: use smaller voxels nd slices, use slower frequency

Question 6

fictional resolution

Answer 6

the smallest detectable difference in two different bold activation

Question 7

signal to noise ratio

Answer 7

the ration between activity in target area divided by external noise ( ex: physical motion)

Question 8

contrast to noise ratio

Answer 8

the difference between two activated area divided by the (external ) noise

different within of firm have different contrats to noise ratios

Question 9

dynamic Contrast to noise ratio OR functional signal to noise ratio

Answer 9

the difference within the same voxel in activation across different condition

task related variability / non task related variability

higher in sensory area rather than associative areas

SNR range
– Total range: 0.1 to 4.0 – Typical: 0.2 – 0.5

Question 10

what to take into account for betewtr functional signal to noise ratio

Answer 10

since it is a measure depend experimental manipulation , make sure the manipulation is effective with the right stimulus –> ex: hone checking for the activation for FFA do not use the rest as control condition but use another visual stimulus

consider that different areas of the brain have different natural amount fo noise over time

Question 11

thermal noise

Answer 11

variation detection of single due to fluctuation of electrons either in the field or in the machine

increases with temperature and field strength

truly random ( so can be decreased with averaging

Question 12

mass motion ( mostly head )

Answer 12

if motion is larger than one voxel it is critical

motion artefact can be decomposed into 3 coordinates ( x,z,y with respect to anterior commissure ) and 3 movement components (and roll, jaw , pitch ) that can be used ars regressor of no interest to correct for the artifact

instructing the participant is fundamental ( can also have sham session to train) , also can be aided with some physical measure like padding

can also correct during preprocessing using realignment

Question 13

inter subject variability source of noise

Answer 13

people differ in RT and also BOLD signal ( especially in some more evolutionarily new areas that present more connectivity difference across subject s)

Question 14

validity problems as source of noise

Answer 14

RT is just a proxy
also different people might implement different strategies

Question 15

general solution of increase signal to noise ratio

Answer 15

use PCA And ICA
use filtering ( careful it can cut out important frequency )
increase field strength ‘??????
averaging by the number of trials

Question 16

problems with avaraging

Answer 16

• assumes noise is random - not correlated with other proccesses , but if not wea re ignoring potential relevant info
• we make activation cluster appear bigger
• since variability is actually divide by the square root of n of trial ( not just by pure n of trial ) at one point the difference betwween sir root of different numbers will not be detectable anymore , so advantage of averaging is lost

Question 17

temporal resolution

Answer 17

ability to detect changes over time

Question 18

problems with fMRI time resolutions

Answer 18

MEnon 1998 : some area might have fixed delayed onset times independently of the task type and duration

variability between subject –> averaging

variability between task in the same subject : make sure the difference in RT for different task is not due to confounding like duration of the task , difficulty , etc..

bold single is sluggish , it does not perfectly reflect neuronal activation times

dependency on sampling rate

Question 19

how can sampling rate (repetition time ) affect time resolution

Answer 19

aliasing problems = different repetition time can give different bold signal

too short rt cudl take long time or have a small ccoverage
woudl noy giev the time to the flip angle to reach the peak –> smaller signal
too large RT can make the initial dip go undetected

possible solution = jittering : starting the RT at different latencies in the Bold signal timeline

Question 20

what is the linearity system framework and what does really happen to bold signal of repeated stimuli ?

Answer 20

linearity systems assume
scaling : amplitude of single is proportional to the input magnitude
superimposition : the result of two successive stimuli is the summation of the two single output

BUT
we have refractory effects : the successive stimulus is influenced by the first one, t hey are not independent -> amplitude is lower and peak is later the closer they are
aka successive stimuli are under additive

Question 21

how do refractory effects become useful in adaptation studies ?

Answer 21

ina adaptation studies , if adaptation is present the two stimuli are perceived as a single one , so there is only one response , and therefore no refractory effect
if adaptation ins not present ,we have two successive percieve stimuli , which will show refractory effects

Question 22

ideal TR

Answer 22

for event related : 1.5-2 ms
for block design : 3-4 ms

Question 23

preprocessing steps

Answer 23

visual inspection of scans and movies to detect mass motion
check

remove dummy scans

adjust distortion: use the map fo the magnetic field to adjust distorted images

realignment : superimpose images of same modalities from same participant , by using the 6 parameters values to apply rigid body transformation ( if leftover unpatching in activated areas , sue the parameter as noise parameters , so as regressor of no interest ))

sparse scanning : alternate scanning session with non scanning session –> damp the motion artefact by avoiding recording gin unrelevant period for activation

slice timing correction: interpolate interleaved recording as if happening at the same time ,

coregistration: different modalities scans form same participant are superimposed to increase spatial resolution

normalisation: estimate the normalisation parameters form the tame plate and then apply them to the normalised scans

smoothing : a sort of wighted averaging of each voxel signal with their neighbouring ones, depending on how much each voxel influence each other
pros: better superimposition ( even more than normalisation ), less number of comparisons since we are now comparing cluster of voxels not single ones, increase signal to noise ratio
cons: bad spatial resolution, bad for ROi analysis

Question 24

General linear model components and general goal

Answer 24

Y= outcome aka activation of a voxel
x= predictors we take into account
b= how much of each parameters could be causing y
e= error

goal :
estimate for each voxel a pattern of predictors and estimate the value for their parameters such as the same pattern ( GLM ) can predict with different parameters, the activation of different voxels using different set of parameters for each voxel

How we do that ? just reminder Granziol : contrast matrix where we compare different time points ( rows) with different conditions ( columns ) to estimate the beta , then run test to first asses the model significancy and then the single parameters significancy

Question 25

problems with GLM

Answer 25

- assume errors are normally distributed in each voxel and has the same variance in all voxels ( which sit not ) -does not take into account the fact that activation is not all or none --> usually we convolute an actual HRF activation with the one obtained by the model - does not take into account physiological artefacts - assumes orthogonality in parameters--> in real life they are usually not voxels are not independent from each other--> we don't actually have many single isolated activations ALSO blood flow ( the proxy we use ) is not really localised and spreads

Question 26

problem with multiple comparison

Answer 26

the more test we run the higher the probability of false positive solely because we have more test so we have to correct for the number of comparison AKA diminish the single parameter p value so that when taking multiple test the whole model p value is still reliable

Question 27

main corrections for multiple comparisons

Answer 27

Bonferrroni : divide the the individual parameter p value by the number of test ( problem if you do voxel by voxel comparison so with 50 to 100 thousands fo comparison Family Wise Error Correction with gaussian field theory : estimate a priori the probability of fall expositive for each voxel assuming they have a normal distribution of activation ( so kinda considers clusters ) False discovery rate : estimate , from the significant results, the probability of them being false positives ROI we estimate significant areas in that are signifiant and run a different set of test on that area specifically , reducing the number of voxel to compare or just take predefined areas and run test within them reducing automatically the number of voxels to compare or we just compare rois

Question 28

first order analysis and second orders analysis

Answer 28

first ( fixed effects ) : assume inter subject differences are noise and that effect are the same for all subjects (aka Response magnitude is fixed) secodmn ( random effects). take into account inter individual difference ( magnitude is random ) by using the map of individual activation to estimate a single map of activation

Question 29

block design

Answer 29

pros: no task switching effect easier analysis easier fro participants and tester cons: can make the subject predict the stimuli some task cannot be bloked cannot differentiate individual responses to specific stimuli

Question 30

event related design

Answer 30

pros allow for post hoc analysis ( go back and pin point the activity correspondent to a specific stimulus ) make up for blocked design cons cons : some processes happen online 8 ex gestalt ) and can't be predefined in a n event related design some processed make it difficult to switch an cannot be made into a strip t pattern longer experiment

Question 31

history of neurostimulation

Answer 31

galvani : found that muscles moved with electrical impulse, hypothesised myelin and ion channels aldini : used electrical stimulation,ulation to treat melancholia ferrier : stimulation of cortex revealed cortical maps ( effect in one cortex area showed result in a specific body part 9 MEDUNA : discovered elctroconvulsive therapie to treat some disorders like depression penfield: homunculus and induced memories via electrical stimulation Magnusson & Stevens . found that magnetic field applied by coil had no reaction when continuously used, but di when stopped or restarted Bickford & Freeming : elicited muscles contraction with magnetic stimulation for peripheral nerve

Question 32

advantages of ems

Answer 32

causal elation possible located manipualtion possibility to change control site and task minimise the effect of plasticity any having shorter and non longitudinal l studies ??? can manipulate networks???? neural chronometry disadvantage : those damn cortical areas

Question 33

how does tms work

Answer 33

electric field in coil, elicit magnetic field that on skull elicit electric current on cortex

Question 34

what to take into account

Answer 34

orientation of neuron can determine whether effect is hyper or de polarisation??? orientation of the coil direction of the current

Question 35

monophasic vs bifasic

Answer 35

monophonic ( current in one direction??) is less powerful ( requires more intensity to reach same result as bifasic easier to see effect of summation since affecting more specific neural population=???? bifasic ( current is a sinus ) can recover more fastly so more suited for high frequency pulse s

Question 36

how to find the right areas to stimulate

Answer 36

stimulate an area and derive which one it is forms he effect fprovoked uset he eeg 10/20 system navigate form a know area if you know their relative position use a neuonavigation map

Question 37

how does fMRI work

Answer 37

protons that have moth a magnetic momentum and an angular momentum are said to have nuclear magnetic resonance (NMR) property laos we need molecules that have an odd number of protons or they cancel each other out hydrogen is one of those we align the portions magnetic momentum by applying a constant magnetic field then we tip the portions out of alignment using radiofrequencies at a specific frequency at which protons spin ( larmor frequency , calculated with angular and magnetic momentum values , protons of different molecules have different larmor frequencies)--> this make he potion go to a higher energy state when they go back to alignement and to a lower energy state , they release the excess energy in the form of a oscillation , free induction decay , recorded by the rf coils

Question 38

how hydrogen and deoxygenated and oxyhemoglobin relation on fMRI recording

Answer 38

even if we record hydrogen portions , the deoxygenated haemoglobin is a paramagnetic properties, modified the magnetic field, the oxyhemoglobin does not so fMRi signal increase is dictated by oxygen -deoxy , with more oxygen increasing the signal we know that blood flow is faster than oxygen consumption so what happen when neural activity starts is that we have a higher need and thus supply of oxy, making the single increase ( we woudl expect a decrease in signal due to increase of oxeye consumption and thus increase of deoxygenated BUT NOPE) Hemodynamic Response function has a canonical shape : hypo oxygen stage : initial dip due to oxygen consumption before blood flow supply hyper oxy stage : increase in signal due to arrival of oxy peak overshoot : oxygen consumption rate is catching up with oxygen flow , thus the ratio with deoxygenated is coming to a balance a making the signal decrease ( undershoot )

Question 39

contrast agent ss pros and cons

Answer 39

they have higher paramagnetic properties than deoxygenated , so more sensitive also the signal would now be based on blood volume not oxygen-deoxy ration cons : worse time course signal due to time requirements for the contrast agent to diffuse participant can have side effects injection of substances birth be discouraging

Question 40

history of fMRI

Answer 40

Mosso : understood more activity in brain was linked to more supply of blood to brain , so patient ofn equilibrium woudl tip toward the head if activation--> not totally correct: increase in blood flow( what actually happens ) is not necessarily correlated to increse in volume so weight Pauli : angular momentum rabiu : magntic momentum bloch and purcell : Determined relaxation times.--> They showed that energy applied at a resonant frequency was absorbed by matter, and the re-emission could be measured in detector coils--> NMR imaging Lauterbur: NMR became visual --> Introduced magnetic field gradients (“spatial gradients”), which changed the spin frequency of atomic nuclei over space and thus allowed recovery of spatial information DAMADIAN’: first NMR image Mansfield: echo planar imaging --> getting hwole 2 ogawa : started functional MRI

Question 40

functional contrast

Answer 40

measures differences in blood oxygenation (BOLD) between different confdition ( SNR is the actual value i think )

Question 41

anatomical contrast

Answer 41

ability to distinguish between different tissue types (depends not only on voxel size!)

Question 42

pros and cons of small voxel

Answer 42

better for restricted area hypothesis higher spatial resolutions lower signal to noise ratio longer time

Question 43

what re the CNR of T1 and proton density

Answer 43

t1: high between grey and white low between CSf and air proton --> opposite

Question 44

percentages of change in signal and in noise

Answer 44

singal : 0.5-2% noise: 0.5-5%

Question 45

what increases fucntional resolution but reduces spatial

Answer 45

smoothing normalization using ROI

Question 46

scanner drift

Answer 46

could be due to gradual changes in inhomogeneities in the static magnetic field, or to slow head movement use a high pass filter to correct it

Question 47

Ghost artifacts

Answer 47

slight rhythmic movement like hear pulsation and berating When the field of view (is not large enough to cover the entire area being imagedàsignals from outside FOV appearing on opposite side of image, creating "ghost" images

Question 48

type of hypothesis regarding temporal resolution

Answer 48

type oen : detection--> is the signla there or not ? type two : estimation--> estimate properties of the signal

Question 49

shimming coils

Answer 49

reduce the static magnetic field inhomogeneities

Question 50

radiofrequency coils

Answer 50

can be transmittent or receivers surface coils are not transmitters due to high inhomogeneities but good receivers since they pic up signal only of area of interest adn spare extra noise form irrelevant areas vlolume coils are both transmitters ( good for low inhomogeneities) and receivers ( ok but problem if we are interest in small area since it takes up al lot of noise )=

Question 51

T1

Answer 51

longitudinal relaxation : the return of the magnetic vector along the static magnetic field ( along the z axis ) after it has been tipped away form it

Question 52

t2

Answer 52

transverse relaxation: after resonance , where proton spin in phase, t2 detect their return to out of phase spinning

Question 53

t2*

Answer 53

is the transverse e relaxation that also takes into account the magnetic field disomogeneities (not only spin to spin interaction ) ---> since the deoxygenated causes magnetic field disohomogeneities, the change in deoxygenated is perceived by t2*--> t2* is the basis for bold detection

Question 54

Total NMR signal

Answer 54

PREMSISE: The number of protons directly affects the strength of the NMR signal: A higher proton density leads to a stronger signal. Tissues with abundant hydrogen (e.g., water and fat) generate stronger signals compared to those with lower hydrogen content (e.g., bone or air = depends on total number of protons reduced by t1, t2 and t2*

Question 55

gradient coils

Answer 55

coils that creates predictable changes ( according to a pattern ) to magnetic field, so we get spatial resolution

Question 56

relaxation times and color

Answer 56

t1: short relaxation time show as bright (fat/white =lighter) and longer as darker (less fat --> grey = darker , Csf = very dark ) t2: shot relaxation time show as dark ( fat / white matter ) and longer time as lighter (less fat and liquids ) oposite

Question 57

ideal for maximum visual contrats ( since they have very different relaxation times

Answer 57

t1= grey -white t2= tissue -csf

Question 58

echo planar imaging

Answer 58

Kiev only one pulse and then rapidly shift t the gradient

Question 59

what type of neural process dioes bold reflect more

Answer 59

NOT Sinaptic Density Function ( description of how the endogenous processe of the nuron affect activity-- output descriptor ) or Multi Unit Activity ( combination of output of many neuron ) YES local field potential , the sum of extracepllualr potential that get to the nuron--input descriptor extra , bold signal does not linearly increase with stimulus intensity

Question 60

How is bold connected to T2*

Answer 60

deixy emoglobina increases inhomogeneities--> faster dephasing of T2*--> lower BOLD signal opposite

Question 61

how long post stimulus does Bold reach peak ?

Answer 61

4-6 sec

Question 62

what is the delay afte stimulus of bold signal ?

Answer 62

2 sec

Question 63

how long is th total bold

Answer 63

16 sec fo even short stimuli

Question 64

chat is the toal variance account by the generic HRF ?

Answer 64

70%---> this is why inter subject specific model are important, chi can account for 93% ( otherwise there would be no difference )

Question 65

overshoot usually found in

Answer 65

bloked design

Question 66

overshoot more common for

Answer 66

long stimuli (>10s)

Question 67

initial dip and peak

Answer 67

initial dip is considered to be more spatially accrued as the onset of neural activity peak still used as a proxy for onset of processing

Question 68

Increasing the duration of neural firing (e.g., with longer stimulation)

Answer 68

ncreases HRF width

Question 69

Increasing The Rate Of neuronal firing (e.g., with more intense stimulation)

Answer 69

ncreases HRF amplitude

Question 70

Ogawa Et Al.,1992

Answer 70

they checked the signal at different echo time since echo time only affected t2* and not t1 , if there were changes they would be due to t2* the signal they saw at 80s and not 40 s was due to t2*

Question 71

Blamireetal.,1992

Answer 71

easuring changes in visual cortex activity following stimuli of different durations they saw that even stimuli as short a s2 sec woudl produce a significant change in the signal

Question 72

what does realignement consist of

Answer 72

estimate the 6 parameters that woudl make the scan match onto the reference via rigid body transformation

Question 73

pros and cons of coregistrationm

Answer 73

pro: we can take advantage of the structural images good spatial resolution basically cons: you cannot improve actually the spatial resolution of bad low res images also we cannot make direct inference about the intensity sdiffercnes since they are taken with different components ( t1, t2, t2*)

Question 74

two ways to normalise

Answer 74

1. estimate parametrter to normalise from a t1 image and form a t1 template , then map it onto a functional image 2. make a sort of average template from functional images , and then map each scan into that

Question 75

tf is smoothing

Answer 75

smoothing takes the voxel of the image and substitute with the average of the voxel itself and the neighbouring voxels , those last each weighted base o nt he value of th eternal that we are using

Question 76

statistical parametric mapping

Answer 76

eaning that a statistic (e.g., T-value) is calculated for every voxel – using the “General Linear Model” assumes continuou data and normal distributed noise

Question 77

the x matrix in the linear model

Answer 77

coloumns are condition ? or predictor? and each row is a time point so each whole column is a predicted BOLD signal course

Question 78

good things about glm

Answer 78

can test complex hypothesis , can include variability in the data ( like head motion )

Question 79

small volume correction

Answer 79

definbe an ROI and test just those voxels can be defined a priori ( structural) or with statistical data ( functional roi) WARNIGN : with functional roi do not use the same data used to determine statistically significant activation ROI to test for significance of the voxel inside the roi( of course they will be significant )

Question 80

some components of SP M

Answer 80

mask.img= defines the area to look for activation ResMS.img= info about variability of error beta images= info about the betas estimates beta images and resMS.img are combined to obtain the final image , the spmt.img

Question 81

how to maximise t2 and t1

Answer 81

you need long TR , so to give time to t1 to fully longitudinal magnetization (M₀) recovery before the next excitation pulse. also you need long TE so to give time to T2 relaxation to be completed for t1 is the opposite , wee need short TR and short TE

Question 82

the birth of fMRI with t2*

Answer 82

ogawa used t2* on rodents wo breathed 100% , 21% and =% oxygen , and 0% shoed up with dark spots where blood vessels were ( dark spots =deoxy)

Question 83

describe neurovascular couplign

Answer 83

initially , due to neuronal activation , we have a compensatory response , where blood flow increases faster than the volume , flooding the area with oxy , then the volume adapts increasing , finally the flow returns to normal levels and the volume once again tales longer to adapt

Question 84

fSNR =

Answer 84

task-related variability/non-task-related variability

Question 85

what is a cost fucntion

Answer 85

is the function that tells us how much an image is different from the references (useful for realisgnement)

Question 86

wha is mutual correlation

Answer 86

simile ro cost function but used when having different type of image to compare ( in coregistration) more similar to correlation

Question 87

multicollinearity

Answer 87

ndependent variables in a regression model are highly correlated,

Question 88

what is autocorrelated model

Answer 88

is a model that calculates the correlation of error and excludes it

Question 89

categorical design

Answer 89

tests whether there is activation or not for a specific process can use subtraction: based on pure insertion assumption we haev two task that differs for a component --> this mean if activation is present one y for the difference, thus the activation depends on that non overlapping process between the two tasks ex: familias vs unfamiliar faces recognition can use conjunction: to minimise the problem o fvalididty of pure insertion we isolate the process by making comparison between comparison ex: color naming vs object naming AND object passive vision vs color passive vison--> you compare the are common between object naming and object passive vision not present in the other two category s

Question 90

what are we testing for in the global null hypothesis

Answer 90

significant eset of effects

Question 91

what are we testing for in the conjunction null hypothesis

Answer 91

set of consistently significant effects

Question 92

parametric design

Answer 92

basically a simple lm model with just one predictor we cehc k the change in signal depending on the change in one of our predictor, like intensity , number , duration etc.. rather than its mere presence

Question 93

factorial design

Answer 93

looks for main effect and interaction can be categorical ( lm with two categorical predictors) or parametric ( lm with one categorial and one continuous predictor I)

Question 94

virtual lesion approach VS neuromodlatiuon approaches

Answer 94

virtual lesion aims at interfering with activity in one area so that the areas cannot perform its normal function neuromodulation aimas at enhancing or inhibiting activity in one area so

Question 95

type of pulses

Answer 95

single pulse: one pulse delivered per time , short lived effect dual pulse: two pulses delivered one right after the other from the same could multichannel /multicoil tms: using more than 2 coils ( 2 coils is the norm i think ) paired pulse : two pulses each delivered at a different location

Question 96

example of neural chronometry with single pulse

Answer 96

disrupting V1 activity at different time points from stimulus presentation will tell us when V1 process onset is, cause we woudl have impaired fucntion at that time point with tMS use

Question 97

example of neural chronometry with paired pulse

Answer 97

one stimulation at primary visual area ( static phosphene ) and one at v5( moving phosphene) ---> it was found that when we stimulated v5 first and v1 after 20 ms phosphene was not seen moving , but static AKA at that time V5 gives feedback that allow seeing movement

Question 98

repetitive TMS

Answer 98

longer effect at cortical levels ( 100 ms ) --> does not need temporal precision--> not good for neural chronometry can achieve longer behaviroal effects , usually lasting half of the total stimulation time

Question 99

inhibitory and excitatory TMS frequencies

Answer 99

<1 are usually inhibitory betwen 5 and 20 are usually excitatory theta bursts are an exception ( inhibitory even if they are at high frequency range )

Question 100

theta bursts

Answer 100

is at 5 hz , but each burst is made of 3 pulses at 50 hz efefct last longer than the total stimulation time , up to 90 min

Question 101

types of theta burst stimulation

Answer 101

intermittent : many bursts until they fill up 2 sec, then pause of 8 sec excitatory effect on motor cortex continuous : burst for up to 40 sec , inhibitory effect on motor cortex

Question 102

types of threshold for pms intensity

Answer 102

individual : intensity to elicit response 50 5 of the time motor: lowes intensity that elicits movements phosphene: lowest intensity to elicit moving phosphene

Question 103

what is the relation between motor and phosphene threshold

Answer 103

they are not correlated , so motor threshold cannot be used for visual areas stimulation and viceversa phospehen threshold cannot be used as a proxy for motor areas yet phosphene threshold proved reliable for visual areas

Question 104

what are the standard intensities ?

Answer 104

* single pulse: 60-80% maximum stimulator output (MSO) / 100-120% motor threshold (MT) * repetitive: 50-70% MSO / 80-110% MT * theta-burst: 35-50% MSO / 70-90% MT

Question 105

what to know when using online tms

Answer 105

- When the processing starts - How long it lasts - Whether it is distributed/parallel over multiple areas - Whether it is lateralized or bilateral - Whether it is a feedforward processing or involves backward processing.

Question 106

what can influence tms effects

Answer 106

the level of noise : certain amounts of tbs interference could actually be beneficial to some processes , and produce counterintuitive effects expected form lesion approach neural state : studies report TMS to actually excite less active neurone , again counterintuitive effect to lesion approach

Question 107

artifacts tms

Answer 107

clicks--> use earplugs or usi click also in control condition so ahabituation vibration--> either vibration absorbing padding or give vibration in control as well accidental cranial nerve stimulation ( can cause twitch and pain ) ---> change the coil orientation ( but it woudl influence the effect ) or give tbs offline ( again , it changes the effect

Question 108

what control could be used with tms

Answer 108

control site control task control stimulation ( sham )

Question 109

problems with sham

Answer 109

cold be a placebo coil ,a 90° flipped one , or inverted, or with a panel between it an d the cortex auditory effect is similar but the feeling of the sham does not resemble the one of real stimulation

Question 110

problems with choosing control site

Answer 110

should not be structurally or functionally connected to teh target area usually th homologous area is chosen

Question 111

the heating problem

Answer 111

we either change the coil, cool the coil, use self cooling coils , or include this problem in the experimental paradigm

Question 112

possibile side effects of tms

Answer 112

seizure( usually in patient s) hearing loss burns effect on mood and cognition neck and head ache

Question 113

what and who should avoid TMS

Answer 113

pregnant people brain injury stroke seizure substance abuse metallic medical aid

Question 114

the levels of risk with TMS

Answer 114

1 : benefit is expected directly just from teh stimulation-- risk is accepted 2. potential no verified benefit--> low risk 3 no benefit , just understanding --> needs to eb very very safe

Question 115

types of tES

Answer 115

transcranial direct current stimulation: cstant current of 1-2 mA t alternating current s: current flow is not continue can have different frequencies t random noise s: current alternates randomly t pulsed current s :

Question 116

what does TES do

Answer 116

does not makes action potential fire but changes the level of excitability of neuron

Question 117

anodal vs cathodal stimulation

Answer 117

anodal stimulation causes increased neural excitability ( depolarization ) → increases BOLD signal ( laso increased blood flow with PET ) cathodal stimulation (usually) causes decreased excitability. ( hyoerpolarization) --> decreases BOLD singal ( also decreased blood flow with pet ACTAULLY Low intensity (1 mA): differential effects (anode vs. cathode) Higher intensity (≥ 2 mA): increased excitability from both anodal and cathodal polarity (Batsikadzeet al., 2013).

Question 118

tes advanatges to TMS

Answer 118

cheaper easy to carry and to use acn use sham efficiently no noise