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.