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Lecture 9

PSY 1101 Lecture Notes - Lecture 9: Thalamus, Trichromacy, Opponent Process

Course Code
PSY 1101
Najwa Haddad

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Lecture 9
A. The Stimulus
!In order for us to sense we must be able to detect stimulus.
!E.g. there must be light for us to have vision.
!Light is a form of electromagnetic radiation and is a part of
electromagnetic spectrum.
!The spectrum is huge but we can only detect a thin portion of the
spectrum – visible light
!We can only detect light waves between 400nm to 700 nm.
!Other animals may be able to detect some part of this spectrum
which we can’t see.
!2 characteristics of visible light (form of energy, travels in the form
of waves):
o!1. Wavelength of a light wave is the distance between 2
!!Physical characteristic that is going to be translated into
psychological experience of colour: hue.
!!There’s no colour other there its just light waves, its
your brain taking in and creating the experience of
"!Red (long wavelength)
"!Green (Medium wavelength)
"!Blue (Short wavelength)
!!Colour is a psychological experience.
o!2. Amplitude
!!The height of the wave.
!!Physical characteristic that is going to translate to the
psychological experience of brightness.
!!Your brain creates the psychological experience.
B. The Eye
!Stimulus – light
!Sensory organ to deal with light – the eye
!B.1 Focusing light
o!Light has to enter in your eye through the cornea and travel
through several structures until it reaches the retina.
!!Retina is at the back of the eye.
!!It is made of neural tissues.
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!!Super highly complex.
!!Made up of several layers as thin as a sheet of paper.
!B.2 Retina – Structure
o!Forms the innermost layer.
o!At the back of the retina are the rods and cones.
o!Rods and cones are connected to bipolar cells.
o!Bipolar cells are connected to ganglion cells.
o!The axons of the ganglion cells bunch up together to form the
optic nerve.
o!Optic never is going to grab this info, collect it and transmit
it to the brain.
o!Blind spot
!!Area in eye where the optic never exits the eye and
goes to the brain.
!!No neural tissues, just axon, just nerve fiber.
!!Right in the center of the eye.
!!Responsible for our highest visual activity.
!!When you see something with super clarity and fine
details, it is because of the fovea.
!B.3 Retina – Rods & Cones
o!Photoreceptors (rods and cones)
!!Sensory receptors
!!Detect, transduce and transmit.
!!The light is going to keep travelling through the eye
until the light hits rods and cones.
!!Without them we cannot see anything.
o!They differ in:
"!Cones have cone shape, rods have a rod shape.
"!Rods outnumber cones by a huge margin.
!Supersensitive to light
!Require very little light activity
!We rely on them to see when lighting is
!They allow us to see black, grey and white.
!Does not allow us to see colour.
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