R2G Flashcards
how much head rotation do we use for accuracy
100% of angular distance
what encodes the postion of the hand relative to gaze and goal
dorsal premotor cortex
what kinematics vary according to goals/contstraints of tasks
velocity
movement duration
describe the motor planning pathway through the brain
visual cortex (to parietal and temporal) -> prefrontal cortex -> to cerebellum/BG and motor cortex -> brain stem -> spinal cord
describe the ventral visual pathway
perception and object recognition (what)
visual cortex -> temporal cortex
what descending path is used for reach
midbrain and brainstem
what descending pathway is used for grasp
primary motor cortex and corticospinal tract (processed parallel)
what aspects of the brain help to determine grip
visual cortex
parietal lobe
premotor cortex
what are the different types of grips
hook
spherical
cylindrical
describe anticipatory shaping of grasping patterns
pre-grasp is determined by intrinsic and extrinsic properties of object
grip size is proportional to object (max aperture -> reduced to match)
what are the phases of grasp, lift, and release
contact
grip and load
lift release
what happens if you have a ventral stream lesion
no conscious perception or dimension of objects, but able to pick up objects with great adeptness
what happens if you have a dorsal stream lesion
both sensory and movement related deficits
what does the medial superior temporal region do in movement planning
planning of smooth pursuit
what does the posterior parietal cortex do in movement planning
encodes orientation for R2G
what happens with reaching with no vision or impaired vision
reach times are shorter
larger constant errors
timing of grasp is not effected
what is hicks law
having a longer distance from the target and a smaller target size both increase reaction time
what SS info is needed for grasp
accuracy in grasp and adaptation object contact, grip forces, detection of slipping, cutaneous inputs, and finger position
if you reach without SS info, what can happen
drift
vision can slightly compensate
conplex/repetitive/novel tasks may not be able to happen
what are 3 factors that contribute to sensorimotor processing in UE reaching and grasping
individual
task
environment
where does R2G fit in the ICF domain
within body structure and body fx and in activity and participation
what are the four key elements of R2G
- locate the object (visual regard)
- reach (PC and moving UE in space)
- grasp (grip formation, grasp and release)
- in-hand manipulation (fine motor)
during locating central objects what moves
eyes only
during locating peripheral objects, what moves
eyes and head (neck muscle activated first, but eyes actually move first)
in children with hemiplegia, if they don’t have vision and an intact motor system, how is motor planning and execution affected
they cannot develop or execute a movement successfully
pointing has a ______ acceleration but a __________ deceleration because we move as one unit
long
short
describe the dorsal visual pathway
localization (where)
visual cortex -> parietal cortex
where does a motor plan go to for modification and refinement
cerebellum and BG
if you perturb one component of R2G what happens to the other
the other is affected as well, despite them being modulated by different tracts
what are some task/environ related demands that influence grasp performance
weight of object, object size, shape and texture
inertial resistance provided by intrinsic stiffness of UE and hand
what is translation (in hand manipulation)
ability to move objects from fingertips to palm or palm to fingertips
what is shift (in hand manipulation)
ability to move an object in a linear manner with fingertips
what is rotation (in hand manipulation)
ability to turn an object around with fingers and thumb or turning object from end to end
what does the premotor cortex do in movement planning
codes body movement
makes plan to be sent to motor cortex
is reaching across midline faster or slower? why?
slower
you are reaching into contralateral visual hemi field which increases processing time
T/F: reaction time decreases with practice
true
