S4-1 Visual Systems (2)

Introduction to Sensorimotor Transformations

Sensorimotor transformations connect sensory input and motor output for coordinated movements, emphasizing visual systems' roles in perception and action.

Key Topics and Readings

• Visual systems for perception and action

• Perceptual action dissociations

• Intentional vs. automatic processes in visual-motor control

• Differences between conscious perception and subconscious actionNotable Readings:

1. Streimer CL et al. - Obstacle avoidance without primary visual cortex

2. Kroliczak G et al. - Hollow-face illusion and perception-action dissociation

3. Day BL & Brown P. - Subcortical involvement in visual control during reaching

Anatomical and Functional Divisions of the Visual System

• Visual pathways: 'What' (object identification) vs. 'Where' (object location) pathways.

• Blindsight: Responding to visual stimuli without conscious awareness, illustrated by cases of Patient DF (preserved visuomotor control) and Patient RV (impaired visuomotor control).

Learning Objectives

1. Describe visual system structures.

2. Explain blindsight significance.

3. Analyze dorsal vs. ventral visual streams.

4. Discuss experimental backing for 'what/where' model.

5. Differentiate 'what/where' and 'what/how' models using case studies.

Visual Pathway Components

Key structures include optic chiasm, pulvinar nucleus, LGN, and superior colliculus.

Functions of Vision: Perception vs. Action

• Visual Perception: Object and event recognition.

• Visual-Motor Control: Execution of movements.

Blindsight Research

Monkeys with removed visual cortices can still perform visual tasks. Humans with visual cortex damage have no visual consciousness but display implicit awareness.

Case Studies of D.B. and R.V.

Explore D.B.'s preserved functional visual-motor control despite visual agnosia, contrasting with R.V.'s impairments due to parietal damage and exploring conditions like Balint's syndrome.