Motor Control and Sensory Processing Quiz

Neural Contributions to Reach, Grasp, and Manipulation

• The course is DPT 425 Functional Neuroscience, Fall 2024 at Saint Joseph's University.
• The primary resource for the information is Shumway-Cook and Woollacott Motor control text, Chapter 17.
• Students will describe upper extremity functions and neural contributions to upper extremity (UE) reach, grasp, and manipulation.

Introduction

• Upper-Extremity (UE) function is the basis for fine motor skills and plays a role in gross motor skills.
• Recovery of function is an important aspect of retraining motor control.
• Contextual factors, including environment and individual, impact upper-extremity function.
• UE function is integrated into most self-care, work, and household activities.

International Classification of Function (ICF)

• The ICF is a framework for understanding health conditions.
• It links health conditions to body structure and function, activities, and participation.
• Body Structure and Function: Neuromusculoskeletal and movement-related functions
• Activities: Mobility (carrying, moving, handling objects), Tasks (self-care, domestic life, real-world activities)
• Participation: Self care (dressing, feeding, domestic life), Activities in real world situations

Sensorimotor Processing for Eye, Head, and Hand Coordination

• Constraints of individual, type of task, and specific environmental constraints determine sensorimotor processing for eye, head, and hand coordination.
• The goal is to understand how the central nervous system (CNS) controls UE movements.

What is Going on in the Brain?

• Visual cortex, Posterior Parietal Association area, Somatosensory Cortex, Prefrontal area, Premotor cortex, Primary motor cortex, Basal Ganglia, Cerebellum, Spinal cord, Motor neurons, Sensory receptors, Spinal cord pathways, Somatosensory cortex, play important roles in processing information for reach, grasp, and manipulation.

Hedmann's Model for Movement Observation Analysis

• The model outlines the stages of movement observation, including initial conditions, preparation, initiation, execution, and termination.
• Key aspects include posture, ability to interact with the environment, stimulus identification, response selection and programming, timing, amplitude, direction, stability, and smoothness.

Motor Control Principles

• Feedforward and Feedback control are discussed in the lectures.
• Motor program theory is equal to open and close loop control concepts.
• Visual systems are highly involved in feedforward (anticipatory control).
• Somatosensation plays a role in feedback (reactive control).

Feedforward versus Feedback Control of Movement

• Efficient reaching involves both feedback and feedforward control processes.
• Feedforward (anticipatory) control builds on past experience to predict the consequences of sensory information.
• Feedback control compares sensory input to a reference signal, identifying discrepancies and correcting errors reactively.

Role of Sensory Information in Anticipatory Control (Feedforward) of Reaching and Grasping

• Visual: Locating and determining the initial direction of the reach, characteristics of the object to be grasped, referencing hand location, and object location. Visual accuracy decreases with lack of vision.
• Somatosensory: Determining initial position and coordinating limb segments (e.g., how body and limbs are initially positioned).

Role of Sensory Feedback to Reach and Grasp

• Visual: Attaining final accuracy in reaching, accurate but slower with feedback. Visual feedback doesn't have much impact during grasping.
• Somatosensory: Simple movements don't need constant feedback, but complex movements do. Feedback loops are necessary to correct limb deviations for accurate grasps and manipulation.

Motor System in Reaching and Grasping- Execution of Movement

• Premotor and Primary Motor Cortex receive input from posterior parietal cortex (PPC) to plan, locate, direct/place movement, and determine characteristics of the intended action (e.g., grasp type).
• Evidence suggests PPC encodes visual information in visual reference or coordinates, and premotor cortex encodes more in body reference or coordinates.

Two Separate Descending Pathways for Reaching and Grasping

• Motor development for reaching and grasp occurs early, while grasp and hand manipulation develops later in relation to the maturation stages of the corticospinal tract.
• Individuals with corticospinal injury show impairments in grasp and manipulation but transportation is intact.
• "Transport" component is related to distance and location (Shoulder and elbow), proximal control includes midbrain and brainstem structures (reticulospinal and rubrospinal tracts)
• Grasp "hand precision" component involves wrist and hand pathways, relaying on corticospinal pathways.

Musculoskeletal Contributions

• Complex relationship between neural and musculoskeletal systems, with changes in range of motion (ROM), strength, or muscle tone affecting neural commands.
• Movement compensation occurs when there are limitations in ROM, strength, or muscle tone (e.g., elbow extension range of motion).
• Scapular control plays a role in reaching and grasping, influencing arm movement and arm stabilization.

Postural Support of Reaching and Grasping

• The postural system maintains upright orientation and alignment of postural segments as part of arm movement, in anticipatory and feedback control processes.
• Anticipatory and reactive postural adjustments are considered in postural control.

Motor Control Elements

• Posture is controlled by medial activation, with medial spinal tracts playing a role.
• Reach movement is controlled by rubriospinal and reticulospinal pathways.
• Grasping and manipulation is controlled by corticospinal pathways.

Grasping Patterns

• Power grip uses finger and thumb pads directed to the palm to transmit force.
• Hook grip, spherical grasp, and cylindrical grasp are other types of grips.
• Precision grip uses fingers and thumbs to transmit force.

Anticipatory Control of Grasp and Lift

• Grip formation occurs during transport in anticipation of grasping
• Hand adapts to object size and shape
• Finger movements are timed in relation to the object's transport
• The nervous system anticipates grip based on weight, surface characteristics, and the need for lifting
• Cerebellum plays a role in predicting forces to maintain grasp.
• Feedback loops adjust motor adaptations for slip errors and store force predictions.

Coordination of Reach and Grasp

• Reach and grasp are kinematically coupled movements.
• Invariant features of movement include timing of transport and hand opening, which may represent rules stored in the CNS
• Other elements, such as direction, distance, and speed of grasp types, are modulated by initial task conditions.

Reaction Time (RT)

• Reaction time (RT) measures sensorimotor processing before movement.
• RT is a useful tool for measuring discrete tasks like reaching.

Simple versus Choice Reaction Time

• Simple reaction time involves a single stimulus-response relationship.
• Choice reaction time involves multiple stimuli-response possibilities, which takes more time.

Fit’s Law of Movement

• The relationship between movement time and accuracy when varying distance and target size of movements. Increased time increases with increased distance and accuracy demands.
• The relationship shows that movements take longer time the greater the distance and accuracy demands.

Theories of Reaching Control

• Distance Programming Theories: CNS activates agonist muscles based on perceived distance, relying heavily on initial visual perception.
• Location Programming Theories: Limb muscles act like springs, with the CNS adjusting stiffness as needed for precise location and target contact.

Interference Between Reaching and Cognitive Tasks

• Dual task paradigm compares motor task and cognitive task interference in relation to reach precision and attending to visual stimulus such as reading, and reaction time. Movement time does not change, suggesting that movement planning is affected by the cognitive task

Prefrontal Cortex and Limbic System Influences

• The prefrontal cortex and limbic system are involved in reaching and grasping. The prefrontal cortex is involved in stopping actions and behaviors as well as analyzing behavior in the context of goal-directed movement.
• Limbic system is responsible for explicit memory learning, emotion, and drive.

Conceptual Mapping of Neural Control of Reach and Grasp

• A conceptual map for neural control of reach and grasp should include visual cortex (target location, identification, planning, sensory processing), posterior parietal association area (formulation of internal models, egocentric reference, sensorimotor transformation), prefrontal area (determining environmental goal, planning movement, selection of motor plan and sequence), Premotor cortex (selecting motor plan and sequences), primary motor cortex (commands of movements, judging grasps force and sequence), and Cerebellum (correcting movement errors, maintaining grip force).

Extrapolate Reaching and Grasping Research

• Mechanisms of reaching and grasping identified can be applied to other upper extremity tasks like picking up a spoon and feeding and overhead throwing.

Test your knowledge on the key concepts of motor control and sensory processing relevant to upper-extremity function. This quiz covers essential theories, models, and the neuroanatomy involved in movement observation and control. Challenge yourself with questions about feedforward control and the factors affecting upper-extremity functions.