Motor Control Flashcards
How are behaviors produced by different levels?
Each layer adds new dimentions to behavior. I.e. rats can still groom even without a cortex, so evolution led not to new behaviors but to flexibility
Describe top down vs bottom up
Top down: looking at something voluntary. Frontal/supplemental eye fields (IN THE premotor cortex)
Bottom up: sensory stim coming in and automatically drives behavior (Superior coliculus- orients eyes towards visual stimuli, Boston pizza part of the brain)
What are spinal animals?
good chart on the slides to test yourself on
Reflexes (stepping responses, limb approach/withdrawl. Some of our coordination is built into our spinal circuits
What are low decerebrate animals?
Spinal chord + hindbrain (cerebellum, medulla, pons).
Have sleep stages but not cycles. Narcolepsy…
Decerebrate rigidity (abnormal posture) and postural reflexes.
no voluntary control of the body.
What are high decerebrate animals?
Spinal chord, hind and mid brain
- orient twowards stimlui
- inferior coliculus (sound info)
- no evidence that it’s percieving things tho, just responds to objects.
- no “conscious” vision
- automatic and voluntary (but doesn’t seem driven by any motivation. ie. they will get up and walk but not for any purpose)
What are diencephalic animals?
Has spine, thalamus, hypothalamus, midbrain and hindbrain.
- motivation starts happening
- some spontaneous eating/drinking/emotions
SHAM RAGE: poke the animal and it will be angry for HOURS.
Aimless wandering, motivated behavior but not to do anything for itself (eat/drink)
What are decorticate animals?
Everything except cortex (including basal ganglia)
- super capable.
- eat/drink on their own
- normal sleep wake
- sequency movements (groom)
- classical conditioning is in tact (learn)
- HOWEVER don’t do preparatory behaviors like make nests or hoard food.
- don’t perform complex behaviors.
What is the cortex responsible for?
Amygdala: difference between beeping and dog barking
Cortex: difference between beeping of washing machine and microwave.
- language and motor output
- future planning
= creates a simulation of the world. Uses that model to prepare (you know there is a hallway out there)
more complicated: better simulations of the world.
What is the stretch reflex circuit?
- at spinal level
- nervous system and muscles
- push and pull in different directions
- sensory stretch receptors (to dorsal root to horn which diverges to two muscle groups)
- acetylcholine works at NMJ.
controlling muscle GROUPS not just muscles
relies on proprioception input from stretch reeptors.
activating one usually inhibits another. ^^^
What is the loop of movement?
Think “i want a drink of water”
Have a movement Plan
Motor signal sent to muscles (specific group like hand)
Actual movement
Sensory information to correct behavior (touch/visual)
- visual info improves movement. Proprioception too
Need constant sensory info in order to have movement.
(except for ballistic responses)
Who is pt. GO?
Deficits to somatorsensory cortex, couldn’t pick things up off the ground. Issues with arms.
Don’t adjust for things. SHows that you need sensory input for movement.
What are ballistic responses?
Openloop! So fast that you can’t “course correct” or adjust for them. “punching, or throwing a bat”
What is the heirarchical control of movement
Association cortex Secondary motor cortex Primary motor cortex Brainstem motor nuclei Spinal Motor circuits
Separates what we want to do (have a drink) and the types of actions we can make (not restricted to muscle group- could be your feet) and the more we do things, the lower down it goes freeing up space. (flexibility, why now you can talk and drive but before you couldn’t.)
What is the central sensorimotor program theory?
- Lower levels possess sensorimotor programs which represent a pattern of activity
- A movement produced by activating the oppropriate combination of these sensorimotor programs
- once a level of the heirarchy is activated, it can operate of the basis of sensory feedback without direct control by the higher levels.
IN OTHER WORDS
Simple movements make up larger goals. Once you’ve activated a level, it doesn’t need ongoing effort/concsoius control.
How do we plan out movements?
MOTOR PROGRAMS and INDEPENDANT of MUSCLES in the SECONDARY MOTOR CORTEX.
(we know how to sign our names with our feet if we had to)
Can apply things we’ve learned with our hands. SO WEIRD and awesome.
Motor plans aren’t mapped to body parts.
MOTOR EQUIVALENCE: different muscles and limbs but same behavior.
What is Chunking?
Practice makes sensorimotor programs!
- response chunking: one greater movement rather than “squeezing every finger” to squeeze hand closed. you can “chunk the chunks!’’
- shifting control to lower levels.
Shift form assoication to primary/spinal.
When playing guitar for example, don’t have to focus on elements, can focuson how you sound!
over time, sensorymotor cortex requires less cortical activity to do an activity. smaller area needed.
simple animals don’t have these freed up sensoroy motor association areas.
What is the sensorimotor ASSocIATION cortex?
Dorsolateral PFC (rats don’t have one of these, they only have MPFC)
Posterior Parietal Cortex
High level intentionality.
Whats the posterior parietal cortex?
Damage?
Involved in ATTENTION and INTENTION
Proprioception: knowing where you’re at in space
Recieves visual auditory and somatosensory info
- dorsal stream, related to visual system
-output to secondary motor cortex
-stimulation (low levels) makes people want to move thier bodies, at high levels makes subjects feel they’re performing an action
Has a map of different body parts.
DAMAGE:
Apraxia: inability to follow commands. (often left hemisphere damage)
Contralateral neglect: left neglect. (right damage)
Treated with vision goggles or rotating body in space often.
What is the dorsolateral PFC?
Lots of subregions
- projections from posterior pareital cortex
- projects to secondary motor cortex, primary and frontal eye feild.
- assesments of external stimuli
Works with Posterior Parietal about voluntary decisions.
Motor control, active towards all apsects of a sitaution (predicted outcomes, actiosn, time of day, context)
MAKING A SIMULATION OF THE WORLD and acting on it.
DLPFC fires first in the motor chain,
concsious control to move yourself.
Involved in anything sophisticated. Math, problem solving, working memory)
DAMAGE: diffuse!! decision making, perseverative behavior. can’t form a good simulation of the world.
Can still move but have less grace.
What is the secondary motor cortex?
- 8 areas
- 2 premotor
- 3 supplementary motor areas
-3 cingulate motor areas
Projects to primary motor, itself and brainstem.
Complex movements
Doesn’t care about specific body parts, just a plan . Movement as a concept.
Damage: not paralyzed. (must be gettting otehr info to spine)
- important for complex movements
Supplementary: good for planning, damaged see reduced spontaneous movement and poor behavior
Premotor: damage externally guided movements (follow this dot)
Less interested with specfic muscle contractions and more with angles of movement/orientation.
What are mirror neurons?
In premotor cortex. Fire when someone else is interacting INTENTIONALLY with an object.
(can’t just move hand in the same way)
linked to theory of mind and mimicry.
GOOD THING: we can learn by observing
PROBLEM: we have imaginations, does this maybe guide empathy??***
What is the primary motor cortex?
Precentral Gyrus (M1) Somatotopic organization (homunculus) Receives feedback from body, neurons code for direction/movement not muscles per say. (some contract, some extend)
Damage: independant movement damaged (moving finger is harder than the whole hand), astereognosis (identifying an object based on touch), reduced speed, accuracy, force.
This suggests SMA/premotor control .
What do these main areas not account for?
Cerebellar disorders, alcohol, parkinsons, huntingtons, stereotypy and impulsivity.
Why do we lose coordinatin when we drink alcohol before our cognition declines.
What is the cerebellum doing?
Damage to it?
Recieving input from primary and sensory motor cortex
Collateral sytems: signal to body AND cerebellum AND sensory info (vision, vestibular, stretch, proprioceptioN)
COMPARES intentions to what we actually did then corrects our behavior (7/second)
Critical for timing and sequence.
Damage:
Can’t improve an action/correct a behavior. (dart throwing experiment…what was it? )
Lose precision/smoothing of behavior.
Makes learning new things challenging.
Problems w posture
attention, memory, executive control (almost always active)
What is the basal ganglia?
Group of Nuclei
Caudate + putamen (striatum) Globus pallidus,
Substantia nigra, and subthalamic nucleus are close friends.
Modulates motor output though 2 circuits.
Critical to habit formation (still going to the old coffee cabinet) and cognitive roles. Promotes skill learning.
Smaller circuits within (riding a bike) and inhibitory circuits (don’t pee while playing piano)
What is tonic inhibition?
GP internal always releasing gaba (tonic) onto VA thalamus so that it doesn’t move all the time.
What is the GO cirucit?
Cortex sends a signal to the striatum which inhibits GPi which then stops tonic inhbition of thalamus so that it can hit the frontal cortex and promote movement!
What is the stop (indirect) pathway?
Corex sends signals to other striatal neurons to inhibit the GPexternal which then STOPS inhibiting the GPinternal so that it can increase inhition of thalamus, NO movement. at the same time. inhibiting GPexternal allows Subthalamuc nucleus to activate the GPinternal causinge even more inhibition of the thalamus.
How does dopamine work in the basal ganglion circuits?
Acts on metabotropic receptors to modulate a signal. (D1R or D2R) Striatum is rich iwht it.
D1: go path, is activating
D2: stop path, is inhibitory and downregulates signals.
Basal ganglia gets its dopamine from the substantia nigra. “like watering the lawn” with dopamine. not specific.
Has opposite effects on the two circuits.
Direct: increases strength of the go pathway,
indirect: decreases strength of the sop pathway. causing LESS stop.
overall: dopamine causes net movement. to mobilize body!
Describe parkinson’s disease
loss of dopamine from substantia nigra.
(which is always releasing a little dopamine - tonic)
low levels of dopamine, more stop and less go.
Lack of voluntary behavior, starting and stopping of movement is difficult.
L dopa is given as a precursor to dopmaine and this works pretty well.
- since the enzymes are still there
Deep brain stimulaiton of subthalamic nucleus (often inhbiting) to cause less tonic inhibition of the thalamus
What is huntington’s disease?
Specific cells in the striatal indirect pathway. 50/50 change u have it if a parent has it.
Constant mvoement of your body. Havne’t found a good treatment.
What happens if you increase dopamine transmission?
VTA for example? slightly different pathways.
Drugs effect both.
SNn: dorsal striatal (learning, voluntary movement)
VTA: ventral striatum (NAcc) some overlap
Excessive dopamine: excessive species specific behavior! high amounts of spontaneous activity.
Stereotype: pick at skin/chew nails.
movitation: to move.
FInd a way to get ppl off these silly drugs!
