L8 - Using Knowledge of Brain Body Interactions

Question 1

What has targeted muscle reinnervation shown us?

Answer 1

During amputation surgery, nerves for missing muscles are reattached to existing muscles to prevent neuroma.

However, after some time, they activate the new muscles when attempting the “old” function.

can lead to neural prostheses

Question 2

Where have neural prosthetics been successfully implanted?

Answer 2

in the motor cortex.
find the relevent area, eg. stimulate areas and until feel the sensation of thumb etc.

implant and connect to prosthesis to create natural movement

down side - no feedback about force of movement etc. maybe we need to implant in the somatosensory cortex?

Question 3

Describe somatosensory feedback

Answer 3

This is sensation of the body and its movements, such as light touch and deep pressure.
The different senses can occur via diff receptors located on the ends of nerves.

Such as:
Free nerve endings - pain, temperature.
Merkel's disks- light touch
Pacinian corpulscles - deep pressure
Hair follicle receptor - movement of hairs

Stretch/pressure/chemical on receptors = opens Na+ channels in the axon causing an AP.

The sensation is sent to brain via spinal nerves, which have diff characteristics according to diff receptors.
eg. Pain = unmyelinated and fast.
Gut Ache = slower nerves. slower sensation.

diff nerve qualities. `

Question 4

Describe the tract for the somatosensory feedback

Answer 4

the receptor is activated and sends AP to the spinal cord.
travels up and crosses through midline of the medulla, , then to the thalamus and then primary somatosensory cortex.

sensory info also flows to the secondary somatosensory cortex which is involved in emotion - can lead to pleasure.

Question 5

What are microarrays

Answer 5

basically paddles of electrodes.
useful when sensory nerves are damaged and can be placed over the somatosensory cortex to get feedback on movement

mimics natural biology, adaption.

Question 6

What are efference copies?

Answer 6

Or corollary discharge.
A copy of the motor command sent to the sensory regions, to enable planned movement to be compared w/ actual movement.

enables the sense of SELF GENERATED MOVEMENT!

Question 7

How are the efference copies sent to the sensory regions?

Answer 7

Motor cortex –> anterior cerebellum –> cerebellum receives info from afferent nerve telling us where our muscle is, what we did –> sent to sensory cortex

Question 8

What does the tickle tell us about efference copies

Answer 8

• we can’t tickle ourselves because efference copies tell us that we’re doing it. no element of surprise.
• light touch activates somatosensory and anterior cingulate cortex
• Deeper pressure causes deeper laugh, possible due to balance of deep pressure and pain receptors…
• anterior supplemental motor area of cortex is activated when laughing
• too much is painful.

Question 9

What have studies on self-tickle found?

Answer 9

• found that with no delay, people could not self tickle
• when the delay was over 200ms, it was just as ticklish as if it was external
• scz patients with auditory hallucinations found self tickling just as ticklish when self generated as when externally generated