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what areas of the cortex contribute to the production of voluntary motion?

-primary motor cortex
-supplementary motor cortex
-pre-motor cortex
-pre-frontal cortex
-parietal cortex


dorsal pathway of visual input

-used for higher processing
-leaves the occipital cortex and goes to the parietal/frontal cortex and allows us to complete motor acts based on visual input



-need info about object's location in relation to body
-info is relayed from visual cortex-->parietal cortex-->...-->ventral inter parietal area (VIP)
-VIP creates a rough map of space around you
-info from VIP is sent to F4 in premotor cortex and this creates detailed map of space around you

-also need to rely on superior parietal cortex to get info about where your arm is in space and send the input to F2 in premotor cortex
-so F2 constructs a map about where arm is in relationship to your body and things around you



-need to know the features of the item we are picking up
-anterior interparietal and PFG of the inferior parietal cortex have neurons that respond to:
-visually dominant--seeing an object to grasp
-motor dominant--grasping an object
-visuomotor neurons--either condition
-the anterior interparietal and PFG relay info to F5 which fire with the GOAL not motor act


premotor cortex in motor control

-receives sensory info required to move--particularly F4 and F5
-dorsal component--applies the rules that determine whether it is appropriate to move
-identifies intent of motion and decides what motion to produce


supplementary motor cortex and motor control

-2 parts:
-supplementary motor area (SMA)--postural control--what body position does it take to accomplish the motion you want
-pre-supplementary area (pre-SMA)--plans the motor program required to make action occur--more complicated the motion, the more involved

-organize motor sequences
-acquire motor skills
-executive control--decision to switch actions/strategies


primary motor cortex

-precentral gyrus
-controls specific movements
-regions of body that do fine motions have proportionally high representation
-arranged in columns


columns of primary motor cortex

-stimulation of any give column produces a specific motion
-if we are in an area that controls a more general motion, stimulation may produce contraction of a group of Ms
-layer 4: receives sensory input from M and joint proprioceptors
-layer 5: output for corticospinal pathway, so contain axons that travel down SC and activate alpha motor neurons
-2 sets of neurons in each column: 1 to start motion and one to maintain it as long as necessary
-neighboring columns control related motions, NOT neighboring Ms
-2 kinds of columns:
-on/off for agonist M
-off/on for antagonist M


role of the cerebellum

-sequence complex actions
-correct force/direction
-balance and eye movements
-learning of complex actions



2 regions:
-central--postural control
-either side of vermis--force and direction of an ongoing motion



-lateral regions
-plan complex motions



-balance and eye movements of future NOT current actions


outputs from cerebellum:

-via the deep cerebellar nuclei:
-dentate nucleus
-fastigial nucleus
-interpositus: globes and emboliformis


inputs and outputs of postural control

-uses spinocerebellum

-visual and auditory
-efferent copy--pre motor neurons go to alpha motor neurons and send a branch to spinocerebellum so it can look at the incoming info and what the cortex wants to do an adjust to make that happen

-interpositus n
-fastigial n
-to rubrospinal tract
-all of this info goes straight down SC to work on motion happening now


inputs and outputs of force and direction

-uses spinocerebellum and also controls ballistic motion

-muscle afferent
-efferent copy

-interpositus nucleus
-to rubrospinal tract--go straight down SC to work on motion happening now


inputs and outputs of complex motions

-uses cerebrocerebellum--sequencing of rapid movement

-cerebral cortex
-back to cortex


inputs and outputs of planning balance

-uses vestibulocerebellum: control eye movement and balance

-vestibular apparatus--direct or indirect
-fastigial nucleus to vestibular nucleus
-ascend or descend


basal ganglia

-involved in the planning and programming of movement
-input is particularly important in initiation of movement
-they are the mother may I of motor control--takes the plan the cortex makes and evaluates it and says no or yes
-subthalamic nucleus
-substantia nigra: pars compacta and pars reticularis
-striatum: caudate and putamen
-striatum receives the inputs to basal ganglia
-globus pallidus: internal (medial) and external (lateral) segment


nigrostriatal dopaminergic system

-from: substantia nigra pars compacta
-to: nuclei of striatum
-D1 receptors: when dopamine binds, the neuron is activated
-D2 receptors: when dopamine binds, the neuron is inhibited


intrastriatal cholinergic system

-b/w the nuclei of the striatum--cell bodies within the nuclei of striatum
-release ACh and causes an excitatory effect


striatonigral GABA-nergic pathway

-from: striatum
-to: substantia nigra pars reticularis and internal globus pallidus
-"the direct pathway"
-leads to initiation of movement


inputs/outputs thru the basal ganglia

-subtantia nigra pars compact receives inputs and relays them to striatum

-info leaves the basal ganglia via the substantia nigra pars reticularis and the internal globus pallidus
-SNPR and the GPi project to the thalamus and release GABA within the thalamus
-inhibit the thalamus


what and how does the basal ganglia work?

-control beginning and the end of the movement
-basal ganglia work by inhibition and withdrawal of that inhibition to start the movement


direct pathway vs. indirect pathway of the basal ganglia

-D1 Rs
-excited by dopamine
-allows motion

-D2 Rs
-inhibited by dopamine
-excited by EAA/ACh
-inhibits motion


Direct Pathway

-from striatum to substantia pars reticular and internal part of globus pallidus
-SNPC dopaminergic inputs excite the striatal cells by releasing dopamine which binds to D1 receptors on the striatum
-striatum releases more GABA to the SNPR and GPi which is inhibited by the greater amount of GABA, so less GABA is released
-to thalamus which excites cortex--since less GABA is released to it, this allows us to move


indirect pathway

-input from SNPC is inhibitory to stratal neurons that are part of indirect pathway due to D2 receptors
-to activate the indirect pathway, we must use input from the cortex and intrastriatal pathway
-striatal neurons synapse on external globus pallidus and release more GABA to bind to GPe
-GPe is inhibited by the high GABA, so it releases less GABA to the sub thalamic nucleus
-subthalamic nucleus releases more EAA, b/c there was less GABA, it is activated
-EAA binds to SNPR and GPi which activates it and this causes it to release more GABA to the thalamus
-this inhibits the GABA b/c of the high conc of GABA and this inhibits movement


association cortex and voluntary motion

-2 major areas of fcn:
-planning of complex motor actions
-carrying out of thought processes


prefrontal cortex and higher fcns of the brain

-plan complex motor actions
-interacts with parieto-temporal-occipital association area and all levels of motor cortex
-planning of a complex motor act requires the frontal association area, supplementary motor cortex, premotor cortex, and cerebrocerebellum
-interactions b/w frontal, premotor, SMC, and basal ganglia determine IF the motion will occur
-once the motion is planned, sequenced, and approved, the appropriate columns in the primary motor cortex is activated
-APs then travel down the corticospinal tract and activate the alpha motor neurons that innervate the Ms needed to complete the motion


muscle spindle and voluntary motion

-M spindle could be a problem b/c it could oppose every motion b/c every motion we make stretched one or more Ms
-brain solves the problem by using the gamma motoneurons to trick the M spindle into believing that the M is not changing length
-to make motion occur, if the brain activates alpha motor neuron, and it activates the gamma motor neuron for spindles in the contracting (agonist) M--alpha gamma coactivation
to make motion occur, if the brain inhibits the alpha motor neuron, it also inhibits the gamma motor neuron for spindles in the stretching (antagonist) M