Week 2 - Sensory processes and Perception - Part 1- Vision

Question 1

describe the structure and function of the visual pathway from stimulus through to visual representation

Answer 1

Perception - Sensation > Perception > Cognition > Action (This model can rotate around and back as needed)

Visual pathway -
>LIGHT WAVES enter through CORNEA, pupil dilates or constricts to control light
>Image then reversed left to right and top to bottom by lens onto RETINA (brain rights the image)
>In retina RODS (120 million, for dim light, not great with colour) and CONES (6 million, more light, for colour perception) work together to construe image
>Rods and cones connect to BIPOLAR CELLS which synapse with a layer of GANGLION CELLS whose axons collect into a bundle (forming the OPTIC NERVE)
>Retina > optic nerve sends impulses to the cortex via the THALAMUS, to PRIMARY VISUAL CORTEX (in occipital lobe at the back of the brain)

Question 2

describe the two proposed visual processing pathways: one specialised for recognising objects, and one specialised for dealing with navigation and the spatial location, movement of objects and self. How might visual illusions and case studies of acquired brain injury support this dual pathway model?

Answer 2

Ventral stream - for perception - the part of the visual processing system involved in object perception and recognition and the formation of perceptual representations. ‘top down’

Dorsal Stream - for action - the part of the visual processing system most involved in visually guided action. ‘bottom up’

Visual illusions: provide an intriguing paradox as clearly our visual perception is prone to errors.
Case studies: patients with dorsal stream damage can perceive visually but have severely impacted vision for action.