HD

S4-3 Visual-Motor Control I (1)

Sensorimotor Transformations in Visual-Motor Control

  • Understanding: Focus on intentional vs. automatic processes in visual-motor control

Intentional vs. Automatic Processes

  • Intentional Processes: Volitional, conscious adjustments made during visual-motor tasks

  • Automatic Processes: Unconscious, rapid corrections occurring without awareness

  • Study and Distinction: Differences are primarily studied through experimental paradigms

Fast 'Unconscious' Corrections During Reaching Movements

  • Double-Step Paradigm: Experimental setup to understand how visual changes affect reaching

  • Saccadic Suppression: Reduced awareness of changes during rapid eye movements

  • Correction Mechanisms: Involves racing between automatic and volitional control strategies

Role of the Parietal Cortex (PPC) in Reaching Movements

  • The PPC updates and corrects reaching movements online based on visual input

  • Evidence suggests it processes both visual and proprioceptive information

Objectives in Studying Visual-Motor Control

  1. Eye-Hand Coordination: Describe characteristics during reaching movements

  2. Double-Step Paradigm: Explain the dissociation between perception and action

  3. Volitional vs. Automatic Control: Discuss empirical distinctions and evidence

  4. PPC Involvement: Explain its role in online movement control

  5. Perception-Action Dissociations: Discussive two-visual systems framework

Fast 'Unconscious' Corrections in Action

  • Participants often make rapid, unawareness corrections to hand placement after seeing a shifted target

  • Main Findings: Movements adjusted even when changes to target location were not perceived

Eye Movements and Reaching Dynamics

  • Eye movements typically precede hand movements in peripheral targeting scenarios

  • Sequence of Movements: Eye -> Head -> Hand

  • Kinematics of reaching can be altered based on visual feedback

Key Findings from Pelisson et al. (1986)

  • Stable vs. Dynamic Targeting: Differences in hand movement correction

  • Stationary Targets: Consistent aiming with foveated and peripheral vision

  • Displaced Targets: Ability to adjust trajectories post-target shift

Saccadic Suppression and Its Implications

  • Understanding reduced visual sensitivity during eye saccades

  • Affects awareness of target changes occurring within that period

Voluntary vs. Automatic Corrections

  • Key Differences:

    • Fast, automatic corrections vs. slower, voluntary adjustments

    • Importance of understanding underlying processes for rehabilitation and motor control theories

Role of PPC and Research Highlights

  • The PPC's involvement in monitoring and correcting movements dynamically

  • Evidence through TMS indicating its critical role during on-line adjustments

  • Distinctions in performance between patients with PPC lesions vs. healthy subjects in grasping tasks

Experimental Paradigms Evaluated

  • Visuo-Motor Processes: Timing of responses and alterations based on target movements

  • Studies indicating dual pathways for automatic vs volitional adjustments

  • Importance of sensory feedback in adjusting movements dynamically

Takeaway Concepts

  • Understanding automatic corrections enhances knowledge of motor control

  • Practical implications for designing interventions for motor impairments

  • Ongoing research continues to explore the intricate relationships between perception, intention, and action in motor tasks.