Test 4 Flashcards
Sensation:
How our sense receptors and nervous system physically represent our external environment
Perception:
How we mentally organize and interpret sensory information
What are the 3 steps from sensation to perception?
- Reception: absorption of physical energy by the receptors
- Transduction: converting physical energy to electrochemical patterns in the neurons
- Coding: one to one correspondence between physical stimulus and nervous system activity
Law of Specific Nerve Energy:
- Any impulse in a given nerve sends the same kind of message (AP) to the brain
– AP from auditory nerve = sound, olfactory = odor, optic = light - Brain differentiates one sensory modality from another by which neurons are active
Pathway of Light:
- Light enters the eye through the pupil (eye’s small opening)
- It is focused by the
– Lens (adjustable)
– Cornea (not adjustable) - It is projected to the retina (rear surface of the eye) which is lined with visual receptors
– Rods - black & white: responds to faint light most abundant in retina periphery
– Cones - color vision: more useful in bright light most abundant in around fovea - Light from the R field of vision strikes L side retina & Top strikes Bottom
– Just like a camera–the image is reversed - 3mm x 5mm are in center of retina = macula
- center of macula: fovea: most precise vision, specialized for acute, detailed vision
- Blindspot: no receptors here, where optic nerve & axons meet at the back of the eye
Visual Path:
Temporal cortex (lobe)
- contains ventral stream
– “what” pathway
- identify recognize object
Parietal cortex (lobe)
- contains dorsal stream
– “where”/”how” pathway
– visually guided movements: helps motor system find objects & determine how to move toward them/grasp them/ change item location
What is the sequence through which visual information passes?
1) Receptor cells in the back of the eye send messages to
2) Bipolar cells which are neurons located to the center of the eye
3) Ganglion cells which are still closer to the center of the eye
4) Ganglion cells join one another to form the optic nerve, loop around and travel back to the brain
5) Optic nerves from the right and left eye initially meet at the optic chiasm where 1/2 of axons from each eye cross to the opposite side of the brain
6) Most axons then travel to the lateral geniculate nucleus (LGN) of the thalamus which communicates with the
7) Visual Cortex
What is the Young-Helmholtz Theory?
Aka trichromatic theory
- perceive color by relative rates of response by three kinds of cones: red-long, blue-shorter, green-medium
What is the Opponent-Process Theory?
(Hering)
- perceive color in terms of paired opposites, three receptor complexes: red vs. green, yellow vs. blue, white vs. black
What is the Retinex Theory?
Aka color constancy (Edwin Land)
- Retina + cortex
- Information from various parts of the retina reaches the cortex
- cortex compares imputes to determine brightness and color perception
- We can perceive color despite changes in lighting (brightness)
What are refractive errors?
- Myopia
- Hyperopia
- Astigmatism
- Presbyopia
What is myopia?
(nearsightedness)
Objects up close appear clear, further away blurry
What is hyperopia?
(farsightedness0
Objects far away clear, close blurry
What is Astigmatism?
- Asymmetric curvature of the eyes
- Blurred vision for lines in one direction
What is presbyopia?
- Age-related condition
- Ability to focus up close becomes more difficult
What are the deficiencies in vision?
- Color vision deficiency
- Color blindness
- Motion blindness
- Visual Agnosia
- Prosopagnosia
- Lazy ye
- Strabismus
What is color vision deficiency?
- Inability to perceive color differences
- genetic (males)
What is color blindness?
Inability to perceive anything but shades of black, white, and gray
What is motion blindness? What causes it?
“Akinetopsia” from tumor, injury, stroke
- Failure to detect an object is moving or if able to detect the direction or speed of motion
What is visual agnosia?
Inability to recognize objects despite satisfactory vision
What is prosopagnosia?
Inability to recognize faces
What is lazy eye?
“amblyopia ex anopsia”
- Child ignores vision in one eye letting it drift
What is strabismus?
- Eyes don’t point in same direction
- Inability for both eyes to focus on the same thing
What is pain and what responds to it? (FIB)
- The experience evoked by a harmful stimulus and directs one’s attention toward a danger
- The prefrontal cortex responds to pain as along as the pain lasts