action Flashcards
difference between extensors and flexors
extensors extend a joint
flexors contract f
what 3 parts of the NS does action focus on
somatic - moving limbs on purpose
autonomic - unconscious inner body action
internal actions - switching thoughts
why is action an inverse problem
you start with a goal, and figure out what sequence of actions you can take to accomplish it
this chapter we went from top to bottom of action through diff brain and body structures - list them top to bottom
start with motor cortex
premotor and supplementary motor areas in prefrontal cortex
basal ganliga role in initiation
cerebellums role in coordination
spinal cord
muscles
what is motor equivalence
the ability to use different movement produced by either the same or different parts of the Boyd, to perform a task under different conditions
forward model
what will come of the result if I perform an action?
feed forward control
come up with a motor command, send it to muscles to perform, and that’s it - hope for the best.
fast but less accurate, so you may use it when speed is the most important thing
feedback control
come up with a motor command to send to muscles, perform action and compare what actually happens to what you were hoping was gonna happen
If you detect errors, you revise the motor command. Not just send commands and hope for the best, there is a continuous feedback loop of adjustment
slower but more accurate
if the input is the goal and the output is the motor command - what kind of model is it
inverse model
is feedback control an inverse model?
yes because it starts with goal state, and motor command as output. but through visual sensory we compare what happens with our goal and adjust if necessary - this part is a forward model
what common household item is a feedback control system
thermostat - tries to reach a heat, compares goal to actual temperature, simple feedback loop that makes adjustments
what role does the premotor cortex play
cognitive function - what my goal is and how will I accomplish that goal
high level goals and action planning
how long before an action occurs can we see planning activity (readiness potential) in the ipsa or contra lateral hemisphere premotor cortex
what about when they consciously note the decision to make the movement
contralateral because opposite sides control each other
as much as a second before movement occurs
when they consciously report to making the decision, the premotor cortex has already become active
the monkey study with spatail cues shows brain activity when monkey is planning for 2 actions - explain
has to pick one colour or the other based on the cue, neyrons are tuned to diff directions of movement
- baseline - all fire at same level
- sees which 2 movements it may have to do - these two start to fire more simultaneously
-cues disappear while memory is held in mind, neurons continue to fire
-cue of which movement to make is shown, one increases firing rate, and the other is inhibited below baseline
- knows what action to take but waiting for the go, neurons ramp up in preparation
- go cue, neurons have final burst to make the movement
what controls initiation or inhibition of movements
basal ganglia
how does BG initiate or inhibit movements
Cortico BasalGanglia Thalamo Cortical Loops
start in cortex, descend to BG, go to Thal, and then back to cortex
how does the BG know whether to initiate or inhibit a movement,
what else is it used for initiating besides motor actions
Reinforcement learning based on Dopamine from Substantia Nigra
also helps us switch thoughts or update memories, control emotion, relax or take action
steps of direct pathway
baseline - GPA and SNR actively inhibit thalamus w IPSPs causing thalamus to only send weak signals to cortex
- cortex send rep to striatum via Epsp
-striation fires more, sends stronger IPSP down the path
Striatum INHIBITS GPI and SNR
-so these 2 send weaker signal to thalamus than before
-release thalamus from inhibition
positive feedback loop
2 IPSP cancel each other out
steps of indirect pathway
-cortex sends rep to striatum
-striatum ramps up inhibition of GPI
-inhibit GPI, released subthalamic nucleus from inhibition
-subthal fires more, sends EPSP to GPI and SNR
-these 2 inhibit the thalamus more
-thalamus sends back weak response to motor cortex
3 negatives = negative
how can an NT like dopamine causes two different effects
different types of receptors on post neuron
D1 are excitated by dopamine
D2 are inhibited by dopamine
list ways that CBGTC loop are used
emotions
motivational contorl
switching thoughts
remember or forget info
effort vs none
express or bottle emotins
eye movement
what keeps movements coordinated
cerebellum
where is white and grey matter in CB
buried white matter
surface of grey matter
2 types of CB cells
granule
purkinje
what are granule cells, their shape, where in the CB are they, their characteristics
granule are a sig part of neurons in brain
in small space of CB
have parallel fibres
run up and down horiz
long and synapse onto a lot of things
tend to connect with purkinje cells
what are purkinje cells, characteristics, shape, where in CB are they
lots of dendrites
lots of input from other cells
each synapse is opp to adjust strength of connection
what kind of model does the CB use
forward model
motor command as input and output is the predicted result
CB plays a role in error checking and feedback control
constant monitoring to see if actions need redirection to meet the goal
missing slides
7-18 action
what are central pattern generators
what study showed this
circuits in spinal cord that control repetitive consistent movements like walking. makes proper muscle fire at proper time
cat with severed SC walking on a treadmill
limits to central pattern generators - cat treadmill
if cat saw something and wanted to run towards it - info couldn’t get to the hind legs
any top down volitional control or decision making depends on the brain
role of lower motor neurons
they are in the spinal cord, their axons run out and synapse onto muscle fibres in our limbs in PNS
what are muscle fibres
specialized cells, opposite of sensory receptors
muscle fibres convert neural input signals into a physical change in the world by contraction of MF (output)
what are muslce spindles
sensory cells buried in muscle amongst MF
give us our sense of proprioception in our muscles
how does the amount of muscle fibers motor neurosn synpse onto effect how we can control our muscles with precision
if you want fine control over your muscles, you have to have each lower motor neuron to synapse onto FEWER muscle fibres so you can control more precisely with muscle fibres are activated at any given time
if you follow this back to the cortex, we need more neurons there to control the lower motor neurons - this is why the part of motor cortex for hand is larger than the back - more detailed movement s needed
the cortical magnification in the primary motor cortex firectly relates to the fact that
for fine motor control you need to have each motor neuron controlling only a small number of muscle fibers
in single and mulit unit recording, what does the unit refer to
unit means single or multi neurons recording,
researches use the term unit when you put electrode in brain and record from it - it is hard to know if you are recording a single unit or not
how is intracellular recording done
touching or inserting into an ind cell,
cell must be out of the animal - petri dish
not the type we are looking at
how is extracellular recording done
is either ___ or ____
same tech as computer chips, pushed in brain tissue, near neurons but not IN any,
either
Invitro - petri dish
Invivo - intact animal while it does an action. plug on their head you can plug into to record the data
extracellular recording is good for what 2 kinds of resolution
spatial - we know where in the brain the data is coming from rather than measuring from outside the brain
temporal - you know exactly when the activity occurs in time because we record AP down to the ms
disadvantages of single cell recording - extra cellular
only records a few 100 neurons, may miss the right spot, may find diff result 1/2 mm over
doesn’t relate to the larger picture - only see small part
in animal exp people are concerned about what processes involed
whats the big question
where do they draw the line
care and housing
surgical implants
training via deprivation
consent
suffering
killed after
is the gain to humanity worth the animal suffering
draw the line between a fly and a cat
animal 1st and 2nd most commonly used for these tests
mice then fish then cattle - not neuroscience specific
primates used in science brain ones
brain machine interfaces
show the gain of animal testing
how did the robot arm work
implact multi-electrode array into primary motor cortex of human,
connector on their skill reads data from neurons and passes it to computer to control robot arm
in robot arm, how did they deocde motor cortex activity
asked patient to imagine moving arm forward - labeled that as forward movement
train computer program with these brain data and what movements they represent
