CH5 – SENSATION
How do We Sense Our Worlds
SENSATION – sense organ’s response to external stimuli & responses Sensation to Perception:
transmitted to brain o 1. Stimulus – environmental features
o elementary experience, w/o perceptual experiences o 2. Sensation – detect stimulus
o ex. light, air vibrations, odor not what object o 3. Sensory coding – stimulus transduced
PERCEPTION – brain’s further process of detected signals o 4. Perception – brain processes neural signal
o conscious internal representation of stimuli, construct info from
sensation
Sensory coding – sensory organ’s translation stimuli: physical properties
neural impulses
o TRANSDUCTION – sensory receptors pass produce neural impulses
when receive physical or chemical stimulation
Sensory receptors – Specialized neurons in sense organs
connection neurons pass neural impulses to brain
only sensory organ’s neurons directly respond w/ stimuli, brain
respond to other neurons’ input Psychophysics – psychological experiences of physical stimuli
o different physical features has different neural impulse patterns o assess physical energy req. sense organ detect stimuli
light, odors, physical contact unique patterns Sensory Thresholds:
b/c brain can’t process raw stimuli o Absolute Threshold – min. stimulation intensity req. for sensation
o Reception: most sensory thalamus, then thalamus cortex i.e. stimulus intensity detected above chance
cortex = information interpreted as smell, sound, touch ex. Sound = faintest sound detectable 50% time
Qualitative information – diff. sensory receptors respond to o Difference Threshold – just notable diff. btwn 2 stimuli
qualitatively different stimuli –ex. tuba vs. flute, red vs. green i.e. min. changed req. to detect difference
Quantitative information – same sensory receptor, different
Weber’s law – just noticeable difference btwn 2 stimuli based
firing speed –ex. higher freq. w/ brighter light, louder sound proportional to original stimuli, not constant
Coarse decoding – sensory qualities coded w/ few diff. receptor, SIGNAL DETECTION THEORY – faint stimulus detection req. judgment =
each = broad range stimuli combination = diff. quality subject interpretation, not objective
o theory of perception, based on thresholds
Response: YES Response: no
Stimulus: ON Hit Miss
Stimulus: OFF False Alarm Correct Reject
o Response Bias – participant’s tendency report T/F detection
Sensory Adaption – decrease sensitivity to constant level of stimulation
o response diminish over time, agree w/ mind is adaptive
o strong response when continuous stimulus stops
GUSTATION – sense of taste
Stimuli: chemical substances, molecules dissolve in saliva on tongue o Biological supertaster = highly sensitive, extreme dislike bitter
TASTE BUDS – sensory receptors, taste cells in buds transduce taste o Cultural influence begin w/ womb & breast feeding
o average 500 – 10 000 per person; mother’s food preference pass down to newborn
o 5 basic qualities: sweet, sour, salty, bitter, umami *savory” Pathways to the Brain: along cranial nerve
sensation associated differences
o taste preference experience w/i brain mix w/ texture, smell OLFACTION – The sense of smell
Stimuli: molecules dissolved in fluid on mucous membranes in the noes o prefrontal cortex process smell pleasant/aversive; smell intensity
ORFATORY EPITHELIUM – thin layer of tissue, embedded w/ receptors another region = amygdala
o Odorants – chemical particles, pass into nose to nasal cavity emotion, memory also prefrontal cortex, related w/ smell
o thousands receptors ID’d, correspond w/ diff. chemical group Receptors: olfactory neurons’ sensitive ends in mucous membranes
encoding nature unclear, 1 receptor type detect 1 specific odor, o When receptors in the nose respond to chemicals.
or 1 odor stimulate unique receptor combination Pathways to the brain: along olfactory nerve
OFLACTORY BULB – brain center for smell, receptors transmit info. to it,
below prefrontal cortex
HAPTIC SENSE – The sense of touch
Stimuli: tactile simulation – contact w/ skin in all tissues: skin, muscles, membranes, bones, joints, organs
Receptors: sensitive ends of touch neurons in skin o Fast Fibers – for sharp immediate pain
o Temperature/pressure = sensory exterior Activated by extremes physical pressure/temp.
o Sensing temperature – separate hot/cold receptors causes recoil, protective purpose
can trigger both a/ intense stimuli o Slow Fibers – for chronic, dull, steady pain
o Nerve fibers at base of hair follicles also receptors activated by chemical changes in tissues when skin damaged
prevents us using affect body parts, recuperative
respond w/ movement in hair
o Other pressure receptors = capsules in skin, respond continued
vibration, sudden movement, steady pressure
o various signal integration w/ higher-level mental process produce
haptic experiences
ex. stroking pressure points = tickling sensation
Pathways to the Brain: trigeminal nerve (touch above neck), spinal nerves
(elsewhere)
Gate Control Theory – brain regulates pain experiences, suppress/reduce
o pain signals transmitted by small-diameter nerve fibers, block-able at
spinal cord w/ large sensory nerve fibers
pain experience = pain receptors activate & spinal cord’s neutral
“gate” allow signals
mental process (worry of painful stimuli) opens gates
pain process area also stress, fear, anxiety = sensory &
emotional response
o Females lower pain threshold
sex role theory: consistent pain, men less likely to admit
contrary: females greater pupil dilation, more complex pain
management system pregnancy
females: lower threshold w/ higher estrogen levels
o pain treatment: brain-based vs. traditional
ex. learned techniques, alter brain activity, reduce pain
ex. traditional medicinal options: morphine
Pain Receptors
o pain = warning system, stop continuing activities
o pain nerve fibers (2 types) thinner than temperature/pressure: ADUITION – the sense of sound perception
Stimuli: SOUND WAVES –changing air pressure pattern through time cochlea: fluid-filled tube, curls, snake-like shape, inner ear
o wave’s amplitude = loudness (higher = louder) o basilar membrane – cochlea center, connected w/ cochlea’s hair
o wave’s frequent = pitch (higher Hz = higher pitch) cells
Outer Ear auditory canal to eardrum o hair cells = primary auditory receptors
EARDRUM – thin membrane, across canal, marks middle ear beginnings bends w/ pressure waves, neutrons fire in basilar membrane
o waves vibrate eardrum, transferred to ossicles bones (hammer, nail, Localization audition sensory receptors doesn’t code event locations
stirrup) o brain integrates sound travel time & intensity bt
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