HD

S4-4 Perception vs Action II

Sensorimotor Transformations in Visual-Motor Control

Overview

  • Contrast between conscious perception and subconscious action in visual-motor control.

Evidence of Action Encapsulation from Perception

Key Studies

  • Conscious Perception vs. 'Subconscious' Action

    • Importance of exploring how actions can be separated from conscious visual perception.

  • Dissociations

    • Evidence from perceptual vs. motor awareness studies shows non-overlapping processes for perception and action.

    • Double-step paradigm and post-saccadic information.

  • Visual Masking Techniques

    • Use of visual masking (hiding stimuli) to explore how visual information influences subconscious action mechanisms.

Distinctions between Controls

Objectives

  1. Discuss the differences between voluntary (conscious) control and automatic (subconscious) control.

  2. Explain the target "blanking" experiment and its implications for the dissociation of conscious perception and non-conscious action.

  3. Describe basic visual masking procedures and their relationship to subliminal guidance of actions.

Visual Streams

  • Overview of visual pathways involved in processing visual information:

    • Posterior Pulvinar

    • Parietal Cortex

    • Superior Colliculus

    • Retina and LGNd

    • Primary Visual Cortex

    • Inferotemporal Cortex

Perceptual versus Motor Awareness in Double-Step Paradigms

Experimental Findings

  • Studies show that visual control of reaching can still operate without visual access to the limb.

    • Fast unconscious processes are capable of correcting the hand trajectory post-saccade.

    • Increase in accuracy with visual feedback about target locations (both stationary and displaced).

Saccadic Suppression

  • Definition: Reduced visual sensitivity during saccadic eye movements, leading to lower awareness of visual events (e.g., target displacement).

  • Concept of Space/Position Constancy:

    • Visual world appears stable during eye movement due to compensatory mechanisms of the visual system.

The Role of Target "Blanking"

Post-Saccadic Information

  • Brief disappearance (blanking) of a visual target during saccadic eye movements enhances the ability to detect subsequent changes in that target’s position.

  • Studies show increased detection accuracy of target jumps post-blanking, highlighting the visual system's reliance on continuous presence for spatial referencing.

Insights from Blindsight and Visual Processing

Key Observations

  • Blindsight: Ability to respond to visual stimuli without conscious awareness highlights potential dissociations in visual processing faculties.

    • Patients can still interact with objects and move accurately despite having no conscious visual perception.

  • Unconscious Control of Actions

    • Visually guided actions can be influenced by subliminal cues, demonstrating the separation of visual processing and conscious awareness in motor task execution.

Applications in Research

  • Studies on reaching movements illustrate that movement characteristics are influenced by visual input absent from conscious awareness, emphasizing the complexity of the visuomotor system.

  • Findings challenge traditional notions about the centrality of conscious awareness in guiding physical actions.