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sensation, which is the conversion of physical, electromagnetic, auditory and other info form internal and external environments to electrical signals in the nervous system
processing of sensation info to make sense of its significance
neurons that respond to stimuli and trigger electrical signals
neuronal cell bodies outside CNS
- min of stimulus energy that is needed to activate a sensory system
- stimulus below never reaches the CNS, never transducer (converted)
threshold of conscious perception
- subliminal perception: refers to perception of stimulus below a given threshold.
- below this reaches the CNS, but not the higher order brain regions that control attention and consciousness.
minimum difference in magnitude between two stimuli before one can perceive this difference
- there is a constant ratio between the change in stimulus magnitude need to produce a jnd (just noticeable difference) and magnitude of the original stimulus
- -if the jnd is 3 then you need to divide it by 440 (original) to get 0.68%
signal detection theory
changes in our perception of the same stimuli depending on both internal and external context
tendency of subjects to systematically respond to a stimulus in a particular way due to non sensory factors
trails where signal is presented
trials where signal is not presented
subject correctly guesses the signal
subjects fails to perceive a given signal
subject perceives a signal when there was none
subject correctly identifies that no signal was given
what gives indication of response bias in subject?
misses or false alarms.
- white of the eye that covers most of the eye
- does not cover the cornea
how does eye get nutrients?
- two blood vessels (choroidal vessels-->complex intermingling of blood vessels between the sclera and the retina)
- retina vessels
innermost layer of the eye
- it contains photoreceptors that transduce light into electrical info the brain can process.
which eye structure gathers and focuses incoming light?
which muscles constitute the iris?
- dilator pupillae (opens the pupil under sympathetic)
- constrictor pupillae
produces aqueous humor that bathes the front part of the eye
where does aqueous humor drain
canal of Schlemm
where does the posterior chamber lie?
- between iris and lens
- anterior is in front of iris
contraction of ciliary muscle
under parasympathetic control
what changes the shape of the lens
ciliary muscle contracts, pulls on the suspensory ligaments which changes the shape
duplicity theory of vision
retina contains two kinds of photoreceptors: specialized for light and dark detection and those specialized for color detection.
- color vision and sense fine details
- most effective in bright light
- three forms (short, medium, large) wavelengths
- centermost point of retina consists of only cones
- though rods are more abundant.
why does color vision have greater sensitivity to fine detail than black and white vision?
more rods, hence more rods need to coverage to one ganglion cell
amacrine and horizontal cells
- help accentuate slight differences in visual info in bipolar cell before being passed on to ganglion cells.
- increase perception and contrasts
simultaneously analyze and combine information regarding color, shape and motion
- shape is detected by these cells, which have high color spatial resolution
- work with stationary objects (very low temporal resolution-can notice details)
which cells detect motion
- have very high temporal resolution, low spatial resolution (cannot notice fine details)
pinna or auricle
- sound wave hits
- channel sound waves into external auditor canal to tympanic membrane
what is great intensity correlated to?
louder sounds, higher amplitudes
what det. the rate at which the tympanic membrane vibrates?
frequency of sound
helps to transmit and amplify the vibrations from tympanic membrane to inner ear
- ossicles (malleus, incus, stapes)
- smallest bones in the body
entrance to the inner ear
oval window of the cochlea
eustachian (auditory) tube
- middle ear is connected to nasal cavity via this
- helps to equalize pressure between middle ear and environment
what is the potassium rich fluid that form the membranous labyrinth in the inner ear?
thin layer of fluid that transmits vibrations from outside world and cushions the inner ear structures
fibers from nasal half of each retina cross paths therefore, all fibers in left visual field from both eyes project into right side of the brain and vice versa
aligns the eyes with the likely stimulus (loud noise) giving us the deer in the headlights look
contains utricle and saccule, which are sensitive to linear acceleration (part of balancing and to determine one's orientation in space.
- sensitive to rotational acceleration
- when head rotates, endolymph in semicircular cancal resists this motion, bending the underlying hair cells which sends signal to the brain
Two point threshold
- minimum distance necessary between two points to feel two distinct stimuli
- depends on density of nerves in region
normal temperature of the skin between 86 and 97
gate theory of pain
- explains why rubbing an injury seems to reduce the pain of the injury
- the spinal cord preferentially forwards the signals from other touch modalities (pressure, temp) to the brain thus reduces sensation of pain
top down processing
memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations
ways for brain to infer missing parts of a picture when a picture is incomplete
law of proximity
elements close to one another tend to be perceived as a unit
law of good continuation
elements that appear to follow in the same pathway tend to be grouped together
we see the outlines of things
law of closure
a space is enclosed by a contour tends to be perceived as a complete figure
law of pragnanz
perceptual organization will always be regular, simple and symmetric as possible.