sensation and perception Flashcards
perception definition
Everything you see, feel, hear, taste, and smell is a product of the biological machinery inside your brain.
what are the four things humans sense?
light
chemicals
mechanical forces
temperature
what is the process of perception?
physical/”distal stimuli” -> input from the physical world -> (psychophysics) -> mental world/”proximal stimuli”
what are the qualities of empiricism?
- knowledge comes from outside the mind
- How are the brain and perception shaped by exposure to different environments?
- The environment shapes the brain and our experience of the world
- “Blank Slate” / Nurture argument
what are the qualities of rationalism?
- certain fundamental principles drive/shape knowledge
- What are the basic substrates and laws that drive perception?
- Our brain’s architecture shapes and constrains experience
- innate tendencies/ nature argument
how do we get from mental to physical world stimuli?
- Sample physical information
- Integrate and encode it in the brain
- Interpret and use it
what are the types of sensory receptors in humans?
- photoreceptors sense light
- chemoreceptors sense chemicals
- mechanoreceptors sense mechanical forces
- thermoreceptors sense temperature
what is visible light?
Visible light is electromagnetic radiation of 380-760nm, emitted by the sun, lightbulbs, etc
what information does light tell us?
- Light energy is reflected and absorbed by surfaces around us.
- This changes the properties of the light.
- Light waves contain information about surfaces.
- The brain extracts surface information from light
what is physical stimulus in the eye?
light waves reflected from the image pass through the cornea and enter the eye through the pupil. the lens focuses the light on the retina
what is sensation in the eye?
sensory receptors in the retina are called rods and cones and detect the light waves
what is transduction in the eye?
rod and cones convert light waves into signals and these signals are processed by ganglion cells which generate action potentials that are sent to the brain by the optic nerve
how do photoreceptors work?
- When light hits a photopigment molecule, it splits
- The split activates the photoreceptor cell – this is the moment of transduction from lightwave to neural impulse
what is photopigment depletion?
- The pupil constricts and widens to control the amount of light coming in to optimize the sensitivity of the photoreceptors for the light conditions.
- Photoreceptors are at the BACK of the eye so that photopigments can be readily replenished.
what are the qualities of rod cells?
response: slow
recovery: slow
acuity: low
sensitivity: high
location: peripheral retina
how many: 120 million
function: peripheral and low-light achromatic version
types: one type
properties of cone cells?
response: fast
recovery: fast
acuity: high
sensitivity: loq
location: central retina
types: 3 (L,M and S)
how many: 6 million
function: detailed, central, chromatic vision
what are the three types of cone cells?
Short (“blue”) peak at 440nm
Medium (“green”) peak at 540
Long (“red”) – peak at 570nm
what is colour blindness?
Most commonly: lose L/M differentiation (red/green colorblind)
- Common in caucasian males(~5%)
- X-linked genetic trait
- Recently evolved
*Less commonly: lose S cones; ocular albinism; brain injury
what is the distribution of photoreceptors on the retina?
- Cones are concentrated at the fovea.
- Rods are fewer in the periphery, and increase towards the fovea, but there are no rods at the fovea.
- Higher receptor density = higher perceptual acuity
what is the purpose of eye movements?
- Bring new objects of interest to the fovea
- Keep the eyes fixed when the head/body move
- Prevent images from fading by shifting their position on the retina
what is the blind spot?
The blind spot corresponds to the place where the axons of 1.2 million retinal ganglion cells form the optic nerve
what is the importance of edges?
- Signal the presence of an object or boundary (usually)
- Blank spaces are unimportant (usually)
- The visual system exaggerates edges, starting in the retina
what are the two types of retinal ganglion cells?
1) midget cells
2) parasol cells
what is the function of midget cells?
Midget Cells receive input from cones
* The number of cells they summarize is small
* They project to the parvocellular pathway: the pathway into the brain that carries high-acuity details
what is the function of parasol cells?
Parasol Cells receive input from rods
* The number of cells they summarize is large
* They project to the magnocellular pathway:the pathway into the brain that carries low-light peripheral vision, motion and contrast
what are receptive fields?
- The place/type of stimulus that elicits a response in a given neuron
- Neurons “respond” selectively to specific regions/stimuli, from sensory receptors all the way through to cortical brain areas.
- “Respond” = change their firing rate (increasing OR decreasing)
- Easier to map RFs at early stages (vision/touch) –becomes increasingly difficult the further into the system you go.
what are dark adaptation and Troxler?
Dark adaptation and Troxler fading reflect changes in sensitivity of the visual c
what happens when you physically deform a mechanoreceptor?
Physically deforming a mechanoreceptor causes ion channels to open, which causes the cell to fire.
what information do the mechanoreceptors involved in the pressure and stretch receptors in the skin provide?
Pressure and stretch receptors in the skin:
* Light touch
* Texture
* Stretch
* Pain
what information do the mechanoreceptors involved in the pressure and stretch receptors in the muscles, tendons and internal organs provide?
- Body position
- Body movement
- Interoception