Chapter 16 Flashcards
Concepts Related to Reach and Grasp
Movement control principles Locating a target Characteristics of reach and grasp Systems contributing to reach and grasp Grasping patterns Neural control of reach and grasp
What does feedback control involve?
information from sensory (visual or proprioceptors)
What does feedforward control involve?
takes advantage of prior experience to PREDICT consequences of sensory information
Steps in eye-head-trunk coordination in object location:
Eye movements alone needed if the target is in the central or near peripheral visual field;
Eye-head movements required if in the further periphery
Eye, head and trunk movements combined together, if in the far periphery
Objects in periphery”
- eyes first (low inertia)
- head
- hand
Movement to reaching and pointing an object:
acceleration is longer than deceleration phase
Movement to reaching and grasping an object
acceleration is shorter than deceleration phase
Visual systems contributing to grasp and reach:
dorsal stream pathway
ventral stream pathway
dorsal stream pathway:
from visual to parietal cortex; information about action and localization
ventral stream pathway
from visual to temporal lobe; information on conscious perception
Somatosensory contribution to position sense
Muscle spindle
Cutaneous afferents
Joint receptors: at the extremes of joint motion;
Somatosensory contribution to the control of grip force
Cutaneous afferents
What do cutaneous afferents do?
activate pathways to increase activity in finger muscles to increase grip force in shoulder and elbow muscles to slow acceleration of the hand
Visual and somatosensory inputs
Used to plan movement proactively;
Used reactively for error corrects during the execution of movement;
Midbrain (red nucleus) and brainstem (reticular nuclei) pathways
control the proximal muscles involved in reaching
Pyramidal pathways
fine motor control of grasping movements
Power grip:
finger and thumb directed toward palm to transmit a force to an object
Precision grip:
forces directed between thumb and finger
Types of Power grip
Cylindrical
Spherical
Hook
Lateral prehension
Types of precision grips:
pinch grips
What is power or precision grip determined by?
intrinsic or extrinsic factors
Intrinsic:
object size, shape, texture