S4-2 Perception-Action (2)

Overview of Sensorimotor Transformations

• Study focus on visual-motor control dissociations between perception and action.

• Examines how vision for perception (how we see) can differ from vision for action (how we coordinate actions).

Key Concepts

Perception vs. Action

• Dissociation Concept: Understanding differences between visual information used for perception and for guiding actions.

• Visual Illusions: Utilization of visual illusions to highlight differences in perception and action responses.

Types of Control

• Real-time Control: Immediate response to visual stimuli when they are perceived.

• Memory-based Control: Actions guided by previously stored visual information rather than real-time input.

Objectives of the Study

1. Visual Illusions: How they can be employed to illustrate differences between conscious perception and action:

   • Size-Contrast Illusion: An example used to show that visual perception can misrepresent sizes, whereas action may not reflect these misjudgments.

2. Control Types: Differentiating real-time from memory-based control of actions:

   • Evidence backing the existence of distinct visual pathways for perception (ventral stream) vs. action (dorsal stream).

3. Neuroscience Understanding: Insights into the neurological mechanisms that underlie these dissociations.

Illusory Effects on Perception and Action

• Visual distortions affect how objects are perceived versus how actions are executed:

  • Examples: Studies demonstrate size distortions can impact perception while actions are based on true object size.

Experimental Findings

Garcia et al. Study Results

• Grasping Movements: Uses of size-contrast illusions impacted size representations in prehension (grasping movements).

• Experiment Setup: Participants grasped objects influenced by visual illusions and provided perceptions of their sizes.

  • Correlation of Grip Aperture and Size: Grip size aligned with physical size, unaffected by illusory perception during visual trials.

Distinction of Visual Pathways

• Evidence supports that separate visual pathways (ventral and dorsal) mediate perception and action, respectively.

Visual Representation and Action Planning

• Real-time Mechanisms: Engaged when visual information is available at the moment of action.

• Memory-based Planning: Implementation occurs when the target is not visible but has been previously perceived.

Case Studies and Neurological Evidence

• Patients with neurological impairments demonstrate differences in perceptual abilities versus motor actions:

  • Insight into how varying pathways in the brain can maintain perception despite deficits in action coordination.

Summary Insights

• Visual perception and motor control involve distinct neural processing, informed by specific contexts (e.g., immediate visual cues vs. memory).

• Neuropsychological evidence points to specialized mechanisms that operate independently within the visual system to govern how we perceive and act in our environment.