Week 8 Notes - Visual World.docx.pdf - TEXTBOOK NOTES 8:...

TEXTBOOK NOTES 8 :
Seeing:
● Learning Objectives
o Identify the key structures of the eye and the role they play in vision.
o Summarize how the eye and the visual cortex work together to sense and perceive the visual stimuli
in the environment, including processing colours, shape, depth, and motion
● Electromagnetic energy: pulses of energy waves that can carry information from place to place
o We can only see the visible spectrum (400 to 700 billionths of a meter)
● Wavelength: the distance between one wave peak and the next wave peak
● Cornea pupil lens retina
● Cornea, a clear covering that protects the eye and begins to focus the incoming light
● Pupil, a small opening in the centre of the eye
● Iris, the coloured part of the eye that controls the size of the pupil by constricting or dilating in response to
light intensity
o Complete adaptation to the dark may take up to 20 minutes
● Lens, a structure that focuses the incoming light on the retina
● Retina, the layer of tissue at the back of the eye that contains photoreceptor cells
● Visual accommodation: the process of changing the curvature of the lens to keep the light entering the eye
focused on the retina.
o Rays from the top of the image strike the bottom of the retina and vice versa, and rays from the left
side of the image strike the right part of the retina and vice versa, causing the image on the retina
to be upside down and backward.
o The image projected on the retina is flat, and yet our final perception of the image will be three
dimensional.
o Nearsighted: focus is in front of the retina
o Farsighted: focus is behind the retina
● Light receptor cells (rods and cones) bipolar cells ganglion cells optic nerve
● Optic nerve: a collection of millions of ganglion neurons that sends vast amounts of visual information, via
the thalamus, to the brain
● Rods: black, white, and gray colors; peripheral vision
● Cones: fine detail and colors; located in fovea (central point of retina)
● Margaret Livingstone: Because Leonardo da Vinci painted the smile in low-detail brush strokes, details are
better perceived by our peripheral vision (the rods) than by the cones
o Found that people rated the Mona Lisa as more cheerful when they were instructed to focus on her
eyes than they did when they were asked to look directly at her mouth
● Visual information retina thalamus visual cortex
● Adaptational advantage in case of losing one eye
o Left and right eyes each send information to both the left and the right hemisphere
● Blind spot: place where the optic nerve leaves the retina
o Eyes are constantly moving, and one eye makes up for what the other eye misses
● Perception created in part due to feature detector neurons
o Specialized neurons, located in the visual cortex, that respond to the strength, angles, shapes,
edges, and movements of a visual stimulus
o The feature detectors work in parallel, each performing a specialized function
o The Necker cube is an example of how the visual system creates perceptions out of sensations. We