S4-3 Visual-Motor Control I (1)

Page 1: Overview of Sensorimotor Transformations

• Topic of Discussion: Sensorimotor transformations in visual-motor control.

• Focus: The distinction between intentional and automatic processes in visual-motor control.

Page 2: Intentional vs. Automatic Processes

• Differences Between Processes:

  • Intentional Processes: Involve conscious decisions and are often slower.

  • Automatic Processes: Occur without conscious awareness and are faster, relying on quick reflexes.

• Key Methods of Study:

  • Utilize fast 'unconscious' corrections during reaching movements to investigate these processes.

  • Double-step paradigm: A method used to study corrections in movement.

  • Saccadic Suppression: Observes visual perception changes when rapid eye movements occur.

• Parietal Cortex Involvement:

  • Updates in reaching based on spatial information regarding target location.

Page 3: Study Objectives

• Primary Objectives:

  1. Analyze eye-hand coordination during reaching movements.

  2. Define and describe the double-step paradigm and saccadic suppression.

  3. Differentiate between volitional (conscious) control and automatic (unconscious) control, with empirical evidence.

  4. Explain how the parietal lobe is involved in the control of reaching movements.

  5. Explore perception-action dissociations through the framework of two visual systems.

Page 4: Focus on Fast Corrections

• Main Interest: Fast 'unconscious' corrections and how they operate in visual-motor tasks.

Page 5: Experimental Evidence from Prablanc et al. (1986)

• Research Findings:

  • Visual control of reaching is significantly more accurate when direct eye movements are coordinated with limb movements.

  • Dynamic Control System: Analyzes limb movement trajectories in response to target displacement during saccades.

  • Key Observations: Participants adjusted their movements without visual feedback of their hand position, demonstrating a robust dynamic control system.

Page 6: Methodology of Experiment

• Experimental Design: Participants pointed towards targets, with conditions for both stationary and displaced targets examined.

Page 7: Eye Movement Metrics

• Metrics Studied:

  • Eye position during saccades, measurement of eye movement latency, undershooting or overshooting targets, and movement velocity metrics.

Page 8: Coordination in Peripheral Visual Field

• Observations:

  • Eye typically moves first, followed closely by head and hand.

  • The timing of eye movements is crucial for efficient reaching.

Page 9: Fast Unconscious Corrections in Pointing

• Procedure: Participants pointed to targets as quickly and accurately as possible.

  • Stationary vs. Displaced Targets:

    • Single-step: Pointing was straightforward.

    • Double-step: Targets jumped during the reaching movement, requiring rapid adjustments.

Page 10: Graphs of Single-Step Pointing

• Data Representation: Availability of graphical data showing performance and adjustments within single-step tasks.

Page 11: Metrics on Single-Step Performance

• Focus on Performance Metrics:

  • Graphs showing eye and target positioning, velocities, and hand movement duration.

Page 12: Analysis of Double-Step Pointing

• Graphical Representation: Results and adjustments during double-step tasks exhibited.

Page 13: Double-Step Pointing Metrics

• Performance Metrics for Double-Step Tasks:

  • Detailed analysis depicting hand and target movement trajectories.

Page 14: Saccadic Suppression Effect

• Understanding Saccadic Suppression:

  • Visual sensitivity decreases during saccadic movements, leading to reduced perception of events.

Page 15: Comparison Between Single-Step and Double-Step

• Visual Representation: Graphs comparing the two types of pointing tasks under various conditions.

Page 16-19: Frequency Distribution of Hand Pointings

• Data Charts: Comparisons among the frequency distributions of hand pointing adjustments.

Page 20: Kinematics of Hand Pointing

• Study of Hand Trajectory: Time-course analysis of hand movements during reaching.

Page 21: Movement Corrections to Displaced Targets

• Findings: Participants adjusted their pointing movements without realizing target shifts occurred.

Page 22: Voluntary vs. Automatic Corrections

• Discussion: Characteristics of voluntary and automatic corrections in movements discussed further.

Page 34: Study by Day & Lyon (2000)

• Focus: The study investigates modifiability of automatic arm movements when subject to a visual target.

Page 35: Experimental Details from Day & Lyon (2000)

• Methodology: Pointing tasks created awareness of the target jump with instructions to differentiate movements.

Page 38: Performance Metrics from Visual Task

• Observations: Data related to movement speeds during various reaching tasks displayed.

Page 39: Summary of Corrections

• Key Differences: Automatic corrections contrasted with voluntary corrections within manipulative contexts.

Page 40: Neural Underpinnings - Parietal Cortex Role

• PPC Functionality: Critical in updating reaching movements by maintaining an internal representation of current hand position.

Page 46: Effect of PPC Lesions on Movement Control

• Clinical Findings: Importance of the PPC region emphasized through patient studies exhibiting distinct reach patterns.