T15, Brain machine interfaces (Joao Sanches) Flashcards
WHAT DO YOU USE THE BEYES THEOREM FOR?
- Basics of all current estimation method
- Establish how our vision of the reality (theta) changes with new observations (x)
- you don’t know (theta=what you are looking for) but you know the normal distribution of theta –>p(theta) you know more than nothing
difference between the Maximize likelihood function (ML) (data driven method) and
?
if you are searching for detection of movement where are should you look?
primary motor cortex
if you are searching for detection of movement where are should you look?
primary motor cortex
what is homunculus?
- Motor map
- -> in precentral gyrus
- Sensory map
- -> in postcentral gyrus
Challange?
try to detect and identify neurons activities in motor and sensor area
metabolic activity?–> less accurate than electrical activity
Example of data acquisition?
- Eelctroencephalongraphy
- cap (more accurate) distribution of electrodes is standard. often only electrodes in the middle are used because thats where motor and sensor cortex is
-
Typical set-up for
?
what is BCI?
- a pattern recognition problem
- an estimation/detection problem
oscillatory waves
Difference between alpha, beta, gamma?
their frequency
P300 evoked potential
- one of the most important methods
- peak about 300 ms after the stimuli
potentials?
potentials on the cortex
- all different kinds of changing (evoked or not)
is the brain ever inactive?
no, the brain is always working. Even when you rest your brain has standard firing rate when they are not occupied in a task. More or less constant.
ERD/ ERS
EVENT RELATED De/Synchronization
- desynconisation, activation decreases when more neurons syncronize ( in regions when the area is enrolled in a task)
Neural masses?
ERD
- low magniture
- irregular
- gitter?
ERS
- synchronized
- not enrolled in any task but still synchronized
- higher magnitude
phase–> randome variable
event related (de)synchronized ERD/ERS?
assuming
how can you detect a movement BY EEG?
analyze the brainwaves and how they are synchronized. If the magnitude decreases the area is active in the movement
movement —> decreasing magnitude
alpha band?
C4 the most decreasing one is the left hand?
what we can se the inactive task and the active task
ratio between the (p(act)-p(rest))/p(rest)
Phase locking factor field (PLEf)
continous field of phase in the skull space
important part?
- issue of desynchronization
- potential
- ocialliatory signal (magnitude and phase)
4.
pre procesing
take away noice etc
feature extraction
- power
- magnitude
- phase
- synchronization
- ERD/..
detection?
?
slow cortical potentials (SCPs)?
- slow voltage shifts in the EEG occurring in the frequency range 1-2 Hz
- Negative SCPs correspond to a general decrease in cortical excitability
- positive SCP correspond to a general increase in cortical excitability
what is ERP?
Evoked Related Potential
Visual evoked potentials (VEPs)?
- More prominent in the occipital area
- ## if a visual stimuli is presented —> a continuous oscillatory electrical response is elicited in the visual pathways
What was the response to mental tasks?
Different mental tasks lead to distinkt, task-specific distribution of EEG frequency patterns over the scalp
What is Movement-related potentials (MRP)?
- Low frequency potentials that start about 1-1.5 s before a movement
- Bilateral distribution
- Present maximum amplitude at the vertex
