chapter 9 Flashcards
- (a) How is sensation different than perception?
Sensation: Sensory organs detecting physical stimuli from the environment
vs
Perception: subjective interpretation by the brains
- (b) Can we have one without the other? If so how?
-Yes example: hallucinations are perceptions and not sensations
-Also not all sensations lead to perception; sensory adaptation and attention play roles in determining what is perceived. For example you don’t always perceive that you are wearing clothes
- What is the “visible spectrum”?
-Light is electromagnetic energy that we see
-Range of electromagnetic energy visible to humans is about 400 nanometers (violet) to 700 nanometers (red)
-nanometer (nm): one-billionth of a meter
- Retina
Light-sensitive surface at the back of the eye; consists of neurons and photoreceptor cells
- Fovea
-Region at the center of the retina that is specialized for HIGH ACUITY
-Receptive field at the center of the eye’s visual field
- Optic Disc
-Blind spot
-Your visual system solves the blind spot problem
-The optic disc is in a different location in each eye
-The optic disc is lateral to the fovea in each eye; it lies to the left of the fovea in the left eye and the right of the fovea in the right eye
- (a) Know the cells of the retina, in order, from back to front.
-Bipolar cells, Horizontal cells, Amacrine cells, Ganglion cells
-Muller cells run from the front of the retina to the back
-Bipolar cell: Receives input from photoreceptors
-Horizontal cell: Links photoreceptors and bipolar cells
-Amacrine cell: Links bipolar cells and ganglion cells
- (b) Which are the photoreceptors?
-Rods:
-More numerous than cones
-Sensitive to low levels of light (dim light)
-Used mainly for night vision
-One type of pigment only
-Cones:
-Highly responsive to bright light
-Specialized for color and high visual acuity
(responsible for color and ability to see
fine detail)
-In the fovea only
-Three types of pigments
- (c) Which gives rise to the optic nerve?
Retinal Ganglion Cell (RGC): Gives rise to the optic nerve
- Compare and contrast rods and cones in terms of their location in the retina and their function
Rods:
-Allows us to see in dim light
-Do not perceive color
-Rods outnumber cones; however, there are no rods in the fovea
-Rods are usually located around the boundary of the retina.
Cones:
-Allows for perception of color in normal light
-There are three types of cones: S cones, M cones, and L cones (short, medium, and long wavelengths) (short- 419nm blue, medium- 531nm green, long- 559nm red) There are approx. equal number of red and green cones but fewer blue cones.
-Cones are usually located in the center of the retina.
- Know the major stops of the visual pathway
- Retina: converts light that enters into your eye into electrical signals
- Optic Nerve: sends the signal to the brain
- Optic Chiasm: (like an intersection) Information from the left visual field goes to the right side of the brain; information from the right visual field goes to the left side of the brain.
- (a) Where is the primary visual cortex?
-The primary visual cortex is known as the Striate Cortex or Area V1.
-It is called striate because sections appear striated (striped) when stained with either a cell body or a myelin stain
-It is located in the occipital lobe
- (b) Primary visual cortex in my right hemisphere process what part of my visual world?
(?) It processes information from the left visual field.
- (a) What/where are the ‘what’ and the ‘how’ pathways?
‘what’ pathway: Identifies an object
‘how’ pathway: How action is to be guided toward objects
- (b) Which is the dorsal stream, and which is the ventral stream?
Dorsal stream: Pathway that originates in the occipital cortex and projects to the parietal cortex
-the ‘how’ pathway is dorsal stream
Ventral stream: Pathway that originates in the occipital cortex and projects to the temporal cortex
-the ‘what’ pathway is ventral stream
