Voluntary Movement Flashcards
Describe Voluntary Movement and the impact of the Motor Cortex
- Organized around a purposeful task in the motor cortex
- Can be varied and improved with practice/motor learning
- Can be generated internally or by external sensory information
Describe the difference between voluntary movement and a reflex
When external sensory information or stimulus is received…
A reflex will always be elicited if the threshold is met
Voluntary movement can “decide” whether or not to respond to the stimuli and what to do in the response
List 3 other names for the Primary Motor Cortex
- M1
- Broadmann’s Area 4
- Precentral gyrus
Area: Planning speech production
Broca’s Area (BA 44, 45)
2 Pre-Motor Areas (PMA)
- Premotor Cortex (PMC)
- Supplementary Motor Area (SMA)
Together are BA 6
Describe the 6 Layers of Cellular Organization of the Motor Cortex
Layers 1 & 2 = input from MOTOR and some from SENSORY cortex
Layers 3 & 4 = Input from the THALAMUS
Layer 5 = MAJOR OUTPUT (corticospinal neurons)
Layer 6 = local output
Describe the effect of stimulation in the motor cortex vs. the c-spine
Stimulation occuring in the c-spine will result in mm contraction sooner than stimulation occuring in the cortex b/c the pathway is shorter in the c-spine
Describe what has been understood from mapping grids of M1
- A given muscle may have multiple areas of the cortex that when stimulated will produce varying amount of contraction
- Overlap exists in the cortex (i.e. two muscles could be stimulated by one area)
Describe the connections of the corticospinal axons and its effect on function
The corticospinal axons DIVERGE to motor neurons innervating more than 1 mm
Function: produces and controls simple joint movements as opposed to individual mm movement
Describe the effect of redundacy in the mm representation
Allows different combinations of mm acitivity for different tasks
Also allows compensation after injury due to mutliple tracts with similar functions
Describe the Inputs to the Motor Areas
They are reciprocal
- S1, S2
- Frontol Cortex
- Premotor
- SMA
- Cingulate motor area
- Thalamus, Basal ganglia, Cerebellum
Describe the function of the (pre)frontal cortex in regards to voluntary movement
It reminds you why you’re doing what you’re doing
Cortex Properties:
- Primary simple movements of hand and face
M1
Cortex Properties:
- Highly plastic somatotopic organization
- Allows for motor learning and recovery following injury
M1
Cortex Properties:
- Direct relationship between cell firing rate and force
M1
Can modulate the amount of force needed for a given task
Cortex Properties:
- Direction of movement is encoded by neurons (creates a population vector)
M1
Controls the direction of movement needed for a given activity
Describe the properties of M1
- Controls voluntary movement - primarily simple movements of the hand and face
- Has highly plastic somatotopic organization
- A direction relationship modulates the amount of force needed
- Controls the direction of activity for a given task
Area: Critical for planning movement and preparatory activity
PMA – PMC & SMA
Describe the location of the corticospinal tracts in the cortex
The majority are located in M1
Some are located in the PMA but required stronger stimulation to result in movement
Area: Stimulation evokes more complex movements involving mutiple joint and resembling coordinated movements
PMA
Area: Projects to M1 and directly to SC
PMA
Describe the difference in deficts to M1 and PMA
Deficits to the PMA cause more complex deficits than damage to M1 alone
Cortex Properties: Projects largely to proximal mm, fires during the delay between cue and action
PMCd (dorsal)
Cortex Properties: Externally driven movements
PMCd
Describe the Properties of PMCd
- Externally driven
- Fires during delay between cue and action
- Projects largely to proximal mm
Cortex Properties: Projects to hand/digits to control hand shape
PMCv (ventral)
Cortex Properties: Active whether the subject watches or performs the task
PMCv
Cortex Properties: Fires only during planning of specific hand movements
PMCv
Describe the Properties of PMCv
- Fire only during planning of hand movement
- Active whether performing or demonstrating
- Projects to hand/digits
Area: Projects to M1 and SC (largely to mm of hand and digit)
SMA
Cortex Properties: Heavily involved with planning sequential movements
SMA
Cortex Properties: Internally driven movements
SMA
Cortex Properties: Mental rehearsal of movements
SMA
Cortex Properties: Stimulation evokes bilateral movements – coordinates movement
SMA
Describe the Properties of SMA
- Sequential movements
- Mental Rehearsal
- Internally Driven
- Coordination due to bilateral projection
Describe synergy
A highly stereotyped and obligatory movement
With lesions movements that were once controlled individually are now lumpted together and performed as one movement due to synery
Inhibition fractionated movement due to damage to corticospinal tract
