Chapter 4 - Sensation and Perception

detection

sensing stimuli in the environment

translation

decoding stimuli from the language of their environmental energy form to the language the brain can understand

interpretation

processing stimuli by the brain in order to make it meaningful

sensation

the detection of information from the environment

perception

the meaningful interpretation of sensory information by the brain

transduction

the conversion of physical energy into neural signal

visual anatomy

various parts of the eye that allow us to focus, detect, and transduce light energy into neural signals

visual pathway

the path to and in the brain where neural processing occurs (follows transduction)

color perception

ability of the brain to interpret differences in wavelengths as differences in color

depth perception

ability to see the world in three dimensions despite the two-dimensional nature of images and our retinas

form perception

ability to identify objects based on their shapes

illusion

the misperception of physical reality

hallucinations

false sensory perceptions

auditory system

parts of the ear needed for hearing and the pathway responsible for transferring sound information to the brain

auditory perception

process by which the brain interprets and makes meaning of incoming auditory information

olfactory system

parts of the nose and the pathway that transfer olfactory information to the brain

gustatory system

structures and neural pathways involved in taste

tactile senses

touch and pain

body senses

kinesthetic and vestibular senses

sensory integration

process of bringing together information from multiple sensory systems

energy forms

light waves are seen, sound waves are heard, mechanical energy is felt through our skin, and chemical molecules are tasted and smelled

sensory receptors

specialized cells that detect the physical energy from the environment and convert it into electrical impulses

absolute threshold

the smallest stimulus intensity that can be detected

difference threshold

the smallest possible difference between two stimuli that can be detected 50% of the time

Weber's Law

difference threshold in any given situation is proportional to the intensity of the original stimulus

sensory adaptation

occurs after sensory receptors are exposed to a constant stimulus after a period of time, they stop sending neural signals to the brain

bottom-up processing

processing information at level of sensory receptors first, then putting together bits of information to form a whole perception

top-down processing

processing information and stimuli as a whole, then applying our experiences and expectations to generate a perception

light waves

a portion of the electromagnetic spectrum that can be detected by the sensory receptors in our eyes

pupil

a hole in the middle of ring-shaped muscle (iris) that can expand and contract to regulate the amount of light that enters the eye

lens

structure that focuses light as it enters the eye

retina

a thin membrane that contains the sensory receptors where transduction takes place

photoreceptors

sensory receptor cells in the retina; rods and cones

rods

photoreceptors that are sensitive to low levels of light, allow us to see at night

cones

photoreceptors that are activated by daytime brightness, allow us to see color, and are specialized for acuity

fovea

point of central focus on the retina, contains only cones

optic disc

small section of retina without rods or cones, bundle of nerve fibers that leave the retina to form the optic nerve

blind spot

lack of photoreceptors in the optic disc where vision is not perceived

bipolar cells

special neurons that collect neural signals from photoreceptors and pass them forward to ganglion cells

ganglion cells

receives visual data from a hundred or more rods, integrating the data into one signal

optic nerve

large nerve formed by axons of all ganglion cells in each retina, nerves exit eyes and merge together at the optic chiasm

optic chiasm

point at which some nerve fibers from each eye cross to the other hemisphere of the brain, and some nerve fibers remain on the same side of the brain

thalamus

forebrain structure; processes all sensory information except smell, and then relays the information to higher brain areas in the cerebral cortex

visual cortex

final brain destination for analysis and interpretation of visual information

trichromatic theory

theory that suggests that color vision results from the action of three different types of cones

opponent-process theory

theory that suggests that ganglion cells respond to neural signals in terms of opposing (on-off) pairs of colors

binocular cues

depth perception cues that require the use of both eyes

monocular cues

cues that require a single eye to judge the distance of objects

Gestalt principles

organizing tactics used to form perceptions of groups of stimuli

perceptual constancy

perceiving familiar objects as unchanging

perceptual set

a tendency to perceive our environment from a particular frame of reference

sound waves

mechanical energy form sensed by the ears

outer ear

external structure that collects and funnels sound waves into the ear canal

eardrum

tightly stretched structure at the end of the ear canal, vibrates in time with sound waves

middle ear

amplifies sound waves, contains three small bones

inner ear

begins with the oval window and contains the cochlea

cochlea

a fluid-filled tube of the inner ear where transduction takes place

basilar membrane

membrane that runs the length of the cochlea, embedded with hair cells

hair cells

sensory receptors for the auditory system, bend in response to vibrations, transduction occurs

auditory nerve

structure where neural signals are sent to the brain from the cochlea

auditory cortex

region of the brain where sound stimuli are processed and interpreted

volume

different amplitudes of sound waves, loudness

timbre

complex mixes of different sound waves with a distinctive quality

frequency

sound wavelength which can be perceived

pitch

highness or lowness of sound, a function of frequency

frequency theory

theory that explains how frequency of a sound wave is translated into pitch - the vibration of the basilar membrane matches the frequency of the sound wave that entered the ear

place theory

theory that states that different frequencies result in maximal excitation of hair cells at different locations along the basilar membrane

chemical energy

chemical molecules floating in the air which we smell or dissolved in the saliva which we taste

odorants

tiny molecules of substances that have been released into the air

olfactory receptor cells

tiny neurons in the olfactory epithelium of the nasal cavity, where odorants bind and result in transduction - olfactory axons then travel through bone to olfactory bulb

olfactory bulb

area of the brain which collects information and passes it on to other brain areas for processing in the limbic system

olfactory cortex

area of the cerebral cortex that processes olfactory information

limbic system

located beneath the cerebral cortex, forebrain structures that play a critical role in regulating emotion or feelings

tastants

chemical molecules dissolved in your saliva

taste buds

sensory receptors in the mouth

mechanical energy

energy form sensed by the skin through several types of specialized touch receptors

touch receptors

transduce mechanical energy into neural signals

somatosensory cortex

brain area in parietal lobe that receives information from touch receptors located in specific locations of the body

nociceptors

free nerve endings that recognize pain

gate-control theory

theory that explains how variations in pain perception can be altered by various psychological and situational influences

kinesthetic sense

sense of the location and position of body parts

proprioceptors

sensory receptors for kinesthetic sense, located in muscles and joints and transduce mechanical energy into neural signals

mechanical energy

energy form sensed by the skin through several types of specialized touch receptors

vestibular sense

sense of balance, change of position or motion, the body automatically compensates in order to stay upright and balanced.

semicircular canals

structure in inner ear, sensory organ for the vestibular system, gravitational pull of fluid is transduced into neural signal

vestibular sacs

structure in inner ear, sensory organ for the vestibular system, gravitational pull of fluid is transduced into neural signal that provides information about movement, direction, and gravity

sensory processing disorder

the brain has trouble receiving and processing sensory information into appropriate responses