Lecture 8 motor Flashcards
What happens with neurons when a limb is amputated
During amputation surgery nerves for missing muscles are reattached to existing muscles to prevent neuroma.
After some time they activate the new muscles when attempting “old” function.
How could muscle reinnvervation be used in prosthetic
EMG generated in re-innervated muscle detect by prosthetic and used to make “natural” movement.
How could give mobility to patients who lost control of their body due to spinal damage
We could implnat a receptor over motor cortex and connect it to the robotic prosthesis
amazingly the motor cortex is still able to funtion over a decade after loos of the descending motor outputs
Where else could the electrodes be implanted to enable control of movements
parietal lobe
What are the problems of directing robotic arm using signals picked up by the electrodes
There is no feedback that normally allows us to adjust our movement
Why is sensory feedback important
BONUS
NOT INCLUDED IN LECTURE
without feedback we cannot know the position of our limb needless to say the tectile information that is so important for us to adjust our moves
What are the somatosensory feedbacks provided by the limb?
Light touch, deep pressure, position of joints, itch etc.
The different senses occur via different receptors located on the end of nerves.
Free nerve endings: pain, warmth, cold
Merkel’s disks: light touch
Pacinian corpuscles: deep pressure
Hair follicle receptor: movement of hairs
The mechamism of somatosensory feedack
Stretch/pressure/chemical on receptors opens Na+ channels in the axon causing an action potential.
The sensation is sent to the brain via the spinal nerves which have different characteristics for different receptors.
Dermatome: area of the body each spinal nerve innervates.
SEMI BONUS question what is dermatomes
A dermatome is an area of skin that is mainly supplied by afferent nerve fibers from a single dorsal root of spinal nerve which forms a part of a spinal nerve.
Somatosensory feedback pathway
Receptors - first order neuron - spinal cord - medula (cross over) - thalamus - third order neuron - primary somatosensory cortex
What is the relationship between somatosensory cortex and the primary motor cortex
they are very close
somatotropic map very similar
butt extra areas where voluntary movement is not possible but sensory exist - GENITALZ, intestine, teeth, gums
What is the role of insular in sensation
evidence
Insular is part of the emotional loop, links sensation and emotion
damage to somatosensory cortex but not insular - don’t know where the touch is from but feels nice
damage to insular but not somatosensory cortex - know where it comes from but not happy thus!
Damage to one region (but not the other) can result in separation of the emotional content versus the sensation.
How could we reverse engineer to allow somatosensory information to be sent to the brain
Microarrays placed over the somatosensory cortex may be useful when sensory nerves damaged.
it mimic natural biology
allos adaptation/learning
How could sensory feedback be used to assist patients with prostheses
new prostheses can make use of patients own sensory nerves to take information back to somatosensory cortex
although some argue sensory feedback is not essential with visual feedback and practice
What is sensory-motor integration
Efference Copy (Corollary Discharge): a copy of the motor command sent to sensory regions.
Enables the planned movement to be compared with the actual movement.
Enables the sense of self generated movement.
What brain region is thought to be in control of predicting sensory feedback
anterior cerebellum integrateds forward model with predictored sensory feedback and make the comparison
What does the pushing other people’s hand back and forth experiment tell you
that when you are focusing and expecting a sensation it gets augmented (like breasts)
Why you can’t tickle yourself
Cuz you know its coming……..
Why is tickle a complex sensation and what are the brain regions implicated
2 kinds
light feather touch “itch type”
Deeper laughter provoking type
Light touch and activates somatosensory and anterior cingulate cortex.
Anterior supplemental motor cortex is activated when laughing.
Too much is painful.
How to tickle yourself
Tickle with a delay
they evaluate the quality of tickle by tickle rating rank…..
Relationship between tickle and schizophrenia and evidence
Schoziphrenic have difficulties differentiating whether tickle is self generated or externally generated.
patinets with auditory hallucination present rate tickle as more externally generated
Schizophrenia may result from faulty efference copies of speech, movement and even thought.
If you don’t recognise it as self generated it is natural to assume someone else said/told you/moved something.
