L4 - Brain Machine Interfaces and Prosthetics

Question 1

What is prosthetics?

Answer 1

The utility of a prosthetic to mimic appearance and or function of a missing limb.

The science and practice of evaluating, designing, fabricating, fitting and delivering prosthesis or artificial devices.

Question 2

The allowance of intelligent control by a prosthetic would allow what?

Answer 2

Some of the control of the joints is handed down to the device itself.

Question 3

What is the relationship between the intelligence of the prosthetic device and the ease of control by the owner?

Answer 3

The smarter the device, the harder it is to control.

Question 4

What did Cordella et al., (2016) study and find about prosthetics?

Answer 4

Wanted to find out what patients want from a prosthetic:

• to allow execution of daily life tasks, e.g. grasping and manipulation
• tactile sensorisation system, meaning that continuous visual monitoring would no longer be necessary.
• control system independently managing position and force exerted by the fingers on the objects
• increase the dexterity of the prosthetic, enlarging the number of degrees of freedom it can control.

Question 5

How many degrees of freedom does the hand have?

Answer 5

27.

Wrist - 2
Each finger - 5
Elbow - 2
Shoulder - 3

Question 6

What’s the closest a prosthetic has come to replicating/replacing all of the joints in the hands?

Answer 6

Modular prosthetic limb (MPL).

Has the same strength and dexterity as the human hand.

• has some high level resolution tactile and position sensors.
• 100 sensors in the hand, but not sent to the user - only for device function.

Question 7

Describe open and closed loop control in relation to prosthetic devices.

Answer 7

Open loop: controller –> transducer –> activators

Closed loop: controller –> transducer –> activators –> sensors –> controller

Closed loop receives sensory feedback about each movement/signal (like an efference copy). Sense of awareness will be more difficult with open loop controllers, and continuous visual monitoring will be required.

Question 8

What are the 3 main problems with sensory feedback systems in closed loop devices?

Answer 8

• developing sensors to build into devices (sensory patches on fingertips wear out after hours or days)
• creating feedback devices which can process information and feedback to the user.
• developing computer code which can take sensations from the device and bring them into what might feel like a real sensation.

Question 9

What happens in peripheral sensory loss/peripheral deafferentation?

Answer 9

De-afferentation - loss of the afferent pathway, meaning a failure to report sensory feedback to the CNS. Results in a loss of sensory awareness of limbs and forces continuous visual monitoring to allow successful movements.

Intact efferent pathway - movement of the muscles is fine as signals can reach muscles from the CNS without issue.

Question 10

What are the 3 ways possible to close the loop, and to enable sensory feedback to the brain from prosthetic limbs?

Answer 10

• use remaining nerves (on stump) to intercept signals from brain to limb, and sent to a device.
• surgically split nerves in the chest and move them to existing muscle fibres (where external devices can translate signals).
• record signals in the brain and send signals directly to the device.

Question 11

What are the 4 means of recording motor intention?

Answer 11

• peripheral nerves
• EMG
• EEG
• intracranial

Question 12

What are the 3 ways to stimulate peripheral or central feedback?

Answer 12

• tactile (vibrate/electronically stimulate the skin)
• nerve cuff (stimulate peripheral nerves by cuffing around them)
• intracranial (stimulates the brain itself)

Question 13

What does BCI stand for and what is it?

Answer 13

Brain-computer interface

It is a direct communication pathway between the brain and an external device, bypassing the need for embodiment/the relevant limb.

Question 14

What is the purpose of BCI?

Answer 14

To provide communication capabilities ot severely disabled people who are totally paralyzed, and have very limited alternative options.

Question 15

What are the 3 possible ways of recording from the brain in order to make BCIs possible?

Answer 15

• scalp recording: EEG - electrodes on the scalp, outside of the body, record signals generated by the brain.
• sub-dural: ECoG - electrodes on the surface of the brain. Operation is required to reach the skull layer.
• Intra-cranial: electrodes penetrate into the brain tissue itself, allowing it to record neuron activity

Question 16

Evaluate the use of scalp recordings (EEG) to record from the brain.

Answer 16

+ Safe
+ Easy

• Low spatial resolution
• Low temporal resolution

Question 17

Evaluate the use of sub-dural recordings (ECoG) to record from the brain.

Answer 17

+ higher resolution and better quality signals than EEG (scalp)
+ can last for years, records as long as you want it to
+ can stimulate the brain too.

Question 18

Evaluate the use of intra-cranial recordings to record from the brain.

Answer 18

• risky, surgical operation
• only works for 1-3 years
• scar tissue where the end of electrodes where input.

Question 19

What does the P300 ERP represent?

Answer 19

A decision making signal

Question 20

How do mind control prosthetics work - a BCI using ECoG?

Answer 20

ECoG brain computer interface on the surface of M1. Signals are interpreted by computer algorithms.

Signal are translated into intended movement of a computer cursor and, eventually, a robot arm.

Question 21

Plasticity of the auditory system at deaf patients’ birth is their greatest advantage, despite also being a disadvantage. Why?

Answer 21

Auditory system’s plasticity allows it to learn to interpret the degraded information relayed to it by cochlear implants.

Disadvantage: early on, when cochlear implants are not supplied, unused sections of the auditory system are used by other sensory systems - reducing the effectiveness of late implantations.

Question 22

Cover BCIs, cochlear implants and peripheral control of prosthetic limbs in more detail.

Answer 22

Yes sir.