Neural coding and brain machine interfaces 2 Flashcards
- recent developments
What does a brain machine interface measure to decode movements?
The activity of neurons in the motor cortex while a person imagines a movement.
What was the main result of the Hochberg study regarding decoding accuracy?
It was possible to decode the imagined reach direction with an accuracy of about 80 percent.
What device was implanted in the participant MN during the Hochberg study?
A Utah array consisting of 100 microelectrodes.
What was the task that participant T5 was asked to perform in the Willett et al. study?
focuses on BMIs for communication
To imagine doing handwriting.
2 utah arrays in M1 hand area
what injury did T5 have ?
C4 spinal injury
- paralysed from neck down
What is the specific type of decoding algorithm used in the Willett et al. study?
Recurrent neural network.
trained to decode characters
What was the error rate achieved by T5 when imagining handwriting without predictive text?
Around 5 percent.
How many characters per minute was T5 able to produce by the end of the study?
90 characters per minute.
similar to smart-phone typing speed !
strengths of willet et al.
- addresses degrees of freeedom limitation
- achieves peer typing speed
limitations of willet et al
- one participants
- needs a dedicted lab
not easily accessible
What are the two parallel systems of motor control involved in speech?
One through the cortex and one through the brain stem.
What muscles are primarily involved in speech production?
Lips, tongue, jaw, and larynx.
major peripheral nerves for control of speed and where they are located
brain stem
- facial nerve
- hypoglossal
- trigeminal motor
- laryngeal
cell bodies of these nerves in the brain stem (LMNs and premotor)
What happens if there is a lesion in the M1 face area?
cortical control
Complete loss of voluntary control over speech-related muscles.
Who first reported a specific functional deficit from damage to a part of the cerebral cortex?
Broca.
Fill in the blank: Broca’s area is located in regions _______ of the primary motor cortex.
44 to 45
What does damage to Broca’s area affect?
The ability to produce language, while comprehension remains intact.
despite still having ability to move mouth musles
What significant finding did Penfield discover regarding speech control?
A wide area of the cortex is involved in speech control beyond just Broca’s area.
What kind of injury did participant Bravo-1 experience?
Moses et al. 2021
A stroke in the pons
eye movements ok
True or False: The decoding process in the Willett et al. study was less advanced than in previous studies.
False.
What does an MRI scan from Bravo1 reveal in the pons?
A missing triangle indicating tissue destruction due to a stroke.
The intact tissue appears light gray while the damaged area is dark gray.
What major symptoms did Bravo1 experience due to the stroke?
- Anarthria (inability to talk)
- Quadriparesis (paralysis of all four limbs)
What communication method did Bravo1 initially use before the brain-machine interface?
Computer-assisted typing methods.
What device was implanted in Bravo1 to record neural activity?
Electrocorticography (ECOG).
How does ECOG differ from EEG?
ECOG electrodes are placed directly on the surface of the brain, while EEG electrodes are placed on the scalp.
Where were the recording devices implanted in Bravo1’s brain?
Over the left sensorimotor cortex, straddling the border between S1 and M1.
What was the task given to Bravo1 during the study?
To imagine saying words from a list of 50 words and imagine saying a sentance
What type of algorithm was used to decode words from Bravo1’s neural signals?
A deep learning algorithm.
then filtered output using a language model
What was Bravo1’s accuracy in the isolated word task?
47% correct.
reduced to 30% error rate with laguage model
What communication speed was achieved by Bravo1 using the brain-machine interface?
15 words per minute.
What does ALS stand for?
Amyotrophic Lateral Sclerosis.
causes locked-in syndrome / only limited eye movement or not at all
Chaudhary et al 2022 participant
- ALS
- loss of speech and walking
- feeding tube
- eventually locked-in state
What was the initial communication method for the ALS patient after losing speech?
Eye tracking.
for locked-in state
What communication method was used after the ALS patient lost control of eye muscles?
Yes-no blinking.
What was the outcome of the initial brain-machine interface attempts for the ALS patient?
They did not work.
after BMI with imagined movement failed, Where was the implant placed for the ALS patient in new BMI testing?
Chaudry et al. 2019
Over the hand area of the motor cortex, including M1 and the premotor cortex.
How did the team modify their approach to help the ALS patient communicate?
They coupled the neural recording system to a speaker to translate firing rates into tones.
auditoryneural feedback
how did auditory neural feedback work
- neural firing rate measured
- firing rate mapped to tone frequency
- participant attempts to match tone to pitch
What notable achievement did the ALS patient accomplish using the new brain-machine interface?
Communicated a sentence after 22 minutes of effort.
- provides novel treatmenet for severe paralysis
valuable for those who can’t speak, but onyl 22/107 days ineligble output
What is a significant limitation of the current brain-machine interface studies?
They are based on single participants and not widely accessible.
What is needed for broader application of brain-machine interface technology?
Commercialization and larger scale rollout.
