The Visual System Flashcards
PSYCHOBIOLOGY OF THE SYSTEM (9 cards)
The visual system
the process by which the brain perceives and interprets visual information, enabling us to see and understand our surroundings.
The structure of the eye
Light enters via the cornea → pupil → lens focuses light → retina (contains photoreceptors: rods for low light & peripheral vision; cones for color & fine detail).
Phototransduction
Conversion of light into neural signals via photoreceptors.
Visual Pathways
Optic nerves → optic chiasm (partial crossover) → lateral geniculate nucleus (LGN) in thalamus → primary visual cortex (V1) in occipital lobe
Processing Streams:
Ventral stream (What): Object recognition.
Dorsal stream (Where/How): Spatial awareness & motion.
Hubel & Wiesel (1962)
Found specific neurons in V1 responding to orientation & movement in cats.
Aim: Investigate how visual information is processed in the brain.
Method: Single-cell recordings in cat visual cortex (V1) while showing different stimuli.
Findings: Discovered simple and complex cells responding to specific orientations, movement, and spatial frequencies.
Implications: Revealed hierarchical processing of visual information in the brain.
Riesenhuber & Poggio (2002)
(CRITICISM)
argued hierarchical models of vision are more interactive and dynamic than Hubel & Wiesel’s strict feedforward model.
Ungerleider & Mishkin (1982)
Identified ventral and dorsal visual streams.
Aim: Explore separate pathways for object recognition and spatial location.
Method: Lesions in monkeys — one group with temporal lobe damage (ventral stream) and another with parietal lobe damage (dorsal stream).
Findings: Temporal lesions impaired object discrimination, parietal lesions impaired spatial tasks.
Implications: Supported the what (ventral) and where (dorsal) visual pathways.
Goodale & Milner (1992) CRITICISM
Proposed the ‘perception-action’ model, suggesting the dorsal stream is more for action than for ‘where’, refining the original theory.
