L07: Sensation & Perception Flashcards
Sensation
The ability to detect a stimulus. Features of the environment that are used to create understanding of the world.
Perception
The act of giving meaning to a detected stimulus. Combining of sensations arriving from the sensory system with prior knowledge.
Transduction
Process where stimuli are converted to neural electrochemical energy.
Top-down processing
Applying memory, knowledge, etc. to understand and create perception
Bottom-up processing
Processing the elementary messages from the environment
Psychophysics
The science of defining quantitive relationships between physical & psychological events. Relates physical stimuli to the contents of consciousness.
Gestalt psychology
describes how people tend to organize visual elements into whole entities - “the whole is greater than the sum of its parts”
Figure-ground principle
a form is naturally perceived as a figure while its surrounding area is perceived as ground
Principle of Proximity
elements placed close together are perceived as a group
Principle of Similarity
similar objects are perceived as a group
Principle of Closure
people perceive the whole by filling in missing info
Principle of Good continuation
the eye is compelled to move through one object and continue to another object
Principle of Common fate
objects moving together are grouped together
Blindsight
damage to a visual cortex leads to conscious blindness, typically only on one side. when patients are asked to identify visual stimuli in their blind field, they can do so with accuracy, suggesting conscious and unconscious vision
Visual agnosia
inability to recognize visual objects. associated with issues in the ventral pathway
Prosopagnosia
inability to recognize faces. associated with issues in the ventral pathway. shows emotional responses to very close relatives, suggesting unconscious vision
Cornea
Transparent tissue which allows light rays to enter the eye and focus on objects
iris
Coloured part of the eye consisting of muscular diaphragm which regulates light entering the eye
retina
Contains photoreceptors
fovea
Smallest pit that contains the highest concentration of photoreceptors (rods and cones)
blind spot
Where the optic nerve leaves the eye. no photoreceptors in this area, so the visual system usually fills in the area with info about the surroundings
function of rods
responsible for night vision, dim light, low resolution
function of cones
responsible for daylight vision, bright light, sensitive to blue, red, and green, high resolution
bipolar cells
interneurons that provide the main pathways from photoreceptors to ganglion cells
Ganglion cells
Final layer of the retina
Distribution of rods
found in the periphery, around 100 million in each eye, one photopigment
Distribution of cones
multiple photopigments, around 5 million in each eye, spike in the number of cones by the fovea
on-centre/OFF-surround cell
A ganglion cell that increases firing in response to an increase in light intensity
visual pathway
- information from the retina leaves the eye via the optic nerve.
- information from the optic nerve travels to the optic chasm (cross-over)
- information reaches the lateral geniculate nucleus (LGN) of the thalamus
- information reaches the visual striate cortex then the occipital cortex to be processed
feature detector
nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement
simple cells
neurons fire vigorously when the line is orientated vertically but reduce firing horizontally
complex cells
Fire most when lines are in certain motion
receptive field
the region on the retina in which the visual stimuli influence the neural firing rate
ventral pathway
“what” pathway
Ventral -> temporal lobe -> object recognition
Dorsal pathway
“where” pathway
Dorsal -> parietal lobe -> location of objects in space
visible light spectrum
We only detect between 400-700nm of light (ultraviolet to infared)
trichromatic theory
Colour vision occurs by comparing the activation of 3 different cones
opponent process theory
p-cells fire rapidly to one wavelength and reduce to another, forming pairs of colours (red-green, blue-yellow, black-white)
sound
Vibrations in a medium that cause pressure changes or waves
outer ear
Contains the pinna and tympanic membrane
middle ear
consists of the malleus, incus, and stapes - tiny bones responsible for amplifying sound arriving at the eardrum to the cochlear membrane
inner ear
Helps you hear and maintain your balance. Contains the cochlea
cochlea
Fluid-filled, coiled structure with two membranes, creating 3 canals
hair cells
Transduce mechanical movement from sound waves into neural activity
auditory pathway
- Auditory information travels to the medial geniculate nucleus of the thalamus.
- Info then travels to the auditory cortex in temporal lobes.
interpreting sound
2 theories: place & frequency theory
sound localization
Detecting objects’ location in space requires binaural cues
phantom words
Although everyone hears the same stimulus, perceptions differ based on our prior knowledge.
Mechanoreceptors
transduce mechanical stimulation (pressure) into touch sensation
Thermoreceptors
Signals info about changes in skin temp. Also responds to chemical stimuli. split into warm and cold fibers
Nociceptors
Transmit info about painful stimulation that causes damage to the skin. mechanical, thermal, and chemical signals
Somatosensory pathway
Info is relayed via the thalamus to the contralateral parietal lobe.
Sensory homunculus
A depiction of how the body is represented by the brain, proportional to the amount of cortex devoted to each body part.
Body schema modifications
visual input integrates with and even overrides our conscious body image
