Brain Stimulation Flashcards
methods that have been used to model how behaviors and mental states are realized in the brain
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Lesion study
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Functional connectivity
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Dynamic causal modelling
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Neural decoding
what is the unique information we get with brain stimulation?
causal information: What brain areas are PLAYING A ROLE in the mental states/behaviors interested
what is necessary for a causal inference from brain stimulation?
A temporary (recoverable) disruption of cortical activity when participants are performing a task (also named as “Virtual lesion”)
what happens once a brain region is disrupted?
a cognitive function is (largely) affected
what is sufficient for a causal inference from brain stimulation (assume an intact body)?
Activating an action/mental state by stimulating the brain area(s)
factors needed to consider for brain stimulation?
- stimulation intensity
- stimulation duration
- inter-stimulation duration
what can great spatial specificity tell us?
which part in the brain is responsible for the cognitive function
what are the three factors to consider for brain stimulation?
*Stimulation intensity
*Stimulation duration
*Inter-stimulation duration
why do these three factors affect the two specificity?
Because stimulation accumulates and aggregates across time
* Therefore, (1) neighboring regions can be stimulated by the accumulated stimulations
* (2) the effect of stimulation can last longer than what it should be without the accumulation
excitatory stimulation protocol + excitatory brain area for the function =?
excitatory effect
inhibitory stimulation protocol + excitatory brain area for the function=?
inhibitory effect
excitatory stimulation protocol + inhibitory brain area for the function=?
inhibitory effect
inhibitory stimulation protocol + inhibitory brain area for the function=?
excitatory effect
how does the combination of protocol and target region determine the outcome?
jointy
what determines the outcome jointly?
the combination of protocol and target region
what is a typical experimental design set up?
- The DV (e.g., accuracy in a task)
- The target region
- The stimulation protocol (type of stimulation, duration, intensity, timing)
- The control region
- The sham (Placebo) condition
what can be tricky?
the choice of control region
what does the sham (placebo) condition need to be?
“similar” enough with the real stimulation
Similar as in:
* Somatosensation
*Sound
*Coil position
in what way does the sham condition need to be similar?
- Somatosensation
- Sound
- Coil position
what can sometimes be a good control?
Below threshold (very low intensity) stimulation
The better the temporal resolution, the better the technique?
Depends on the research question
* E.g., Clinical research about treatment to depression
what is invasive stimulation?
Neurostimulation involve surgical interventions to implant electrodes and a pulse generator
what are noninvasive brain stimulations?
Stimulation techniques that stimulate or alter brain activity from the surface of the head without the introduction of instruments inside the body or breaking the skin
what are noninvasive brain stimulations considered to be?
Considered to be safe and without long-term side effect (Bikson et al., 2016)
-> But highly dependent on the target region, intensity, and duration
what are the two types of invasive stimulation?
- electrical brain stimulation
- deep brain stimulation
what happens in electrical stimulation of the brain?
Volley of electrical discharges is sent directly to the brain regions of interest when the human subject is awake
Stimulate different brain regions and observe the change in cognition/behavior immediately
who are most patients of electrical brain stimulation?
Most (if not all) participants are patients that need to receive brain surgery
what does electrical stimulation provide valuable information about?
Provided very valuable information to the development of human neuroscience
E.g., somatosensory homunculus in the primary sensory cortex
what can stimulation to the same region with different intensities generate?
different phenomena
what is needed to generate different phenomena by stimulating the same region
different intensities of stimulation
what are the parts of deep brain stimulation?
IPG -> extension lead -> DBS electrode
what are the advantages of invasive brain stimulation?
- High spatial resolution (Knowing which exact region of your stimulation)
- High temporal resolution (Knowing the exact timing of your stimulation)
when is invasive brain stimulation applicable?
Only applicable to patients with brain lesions (ethical concerns)
what are disadvantages of invasive brain stimulation?
- Limitation in number of samples and paradigm choice
- Problem of generalizability: Neural networks behind a function may differ between patients and general population due to neural plasticity ->
types of non-invasive brain stimulation
- TMS
- tES (tDCS, tACS, tRNS)
- tFUS
types of tES?
- tDCS (Transcranial Direct Current Stimulation)
- tACS (Transcranial Alternating Current Stimulation)
- tRNS (Transcranial Random Noise Stimulation)
are noninvasive brain stimulation techniques safe?
Normally, they are safe (that’s why they are called non-invasive)
under which circumstances can noninvasive brain stimulation be risky?(6)
- Metal implant
- History of seizures
- Neurological disorder
- Medication affecting the central nervous system
- Pregnancy
- Inappropriate protocol (Too high intensity, frequency, or too long duration)
how is spatial resolution of TMS?
- Highly dependent on the shape of the coil
- A few mm for certain coil types
how is temporal resolution of TMS?
- Highly dependent on the protocol (intensity, frequency and duration)
- Very specific if using the single pulse protocol
- The effective time-window can be in tens or hundreds of millisecond (ms)
- The effect can last for very long (e.g., hours or days) if repetitive TMS is used
what is the pulse aggression affect in TMS?
Pulses may aggregate as the stimulation time increase
how is the intensity of TMS?
Most of the time, intensity varies subject by subject
-> Individual difference in reactivity to TMS
how to determine intensity of TMS?
- Participant’s subjective comfort (MOST IMPORTANT)
- The least intensity that can trigger observable change in the subject, then adjust based on the target region
- Resting motor threshold: Stimulating the motor cortex with varying intensity until you observe a motor twitch in the contralateral hand with 50-60% of trials
types of TMS (3)?
- single pulse TMS
- paired pulse TMS
- repetitive TMS
what is single pulse TMS?
Stimulating the target region ONLY ONCE for each trial
what is single pulse TMS used for?
Used to study an immediate effect (within a second) after the stimulation
what is paired pulse TMS?
Consists of 2 successive pulses through the same coil to the same location.
what is paired pulse TMS delivered with?
a relatively short inter-stimulus interval (ISI) (from a few to hundreds of milliseconds)
what is repetitive TMS?
Consistent of a chain of pulses with relatively long period of time before the experiment
what is repetitive TMS used for?
Used to study a pro-long effect (e.g., 60 mins) after the stimulation
spatial resolution of tES?
- Highly dependent on the size of the electrode, usually between 25 and 35 cm2
- With the cathode (return) electrode, it’s affecting a large area of the brain
how can spatial resolution of tES be improved?
Can be largely improved with the high density tDCS
temporal resolution of tES?
Highly dependent on the protocol (especially duration)
* tDCS for less than 3 min did not increase the cortical excitability beyond the stimulation period.
* Long tDCS can induce effects beyond the stimulation period (an hour or much longer)
is the temporal resolution, dependent on the protocol, beneficial for clinical or research?
Maybe beneficial to clinical treatment, but sometimes a problem for researcher
Session contamination: stimulation effect in one session may still affect subsequent sessions
what are both tDCS and TACS using?
electrical current
what is the target of tDCS?
cortical excitability
what is the target of tACS?
Brain Oscillations (synchronization of the neural firing) with certain frequency
current use in tDCS?
stable across time
current use in tACS
alternating (swinging) across time
what is the purpose of tACS?
entrainment of neural oscillation
what is the stimulation in tACS used for?
Using the stimulation to “reset” the onset of the oscillation of different neurons
what is tRNS?
Similar with tACS, except that the alternating current is changing at RANDOM frequency
what can the frequency band use in tRNS be divided into?
- A full range (0.1–640 Hz)
- Low- frequency (0.1–100 Hz)
- High-frequency (101–640 Hz)
what is the full range in tRNS?
(0.1–640 Hz)
what is low frequency in tRNS?
(0.1–100 Hz)
what is high frequency in tNRS?
(101–640 Hz)
what is used in tFUS (Transcranial Focused Ultrasound stimulation)?
steerable ultrasound transducer array
what happens in tFUS?
steerable ultrasound transducer array -> stimulation effects of movement quality
movement quality (e.g. tremor amplitude) -> adjust stimulation focus -> steerable ultrasound transducer array
