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Lecture 5


10 Pages

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Marc Johnson

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PSY312-lec5 May 22, 2013 *next class = midterm! & assignment#3 is due! *Assignments = limit 3 pages! But if u have something relevant to say for a couple sentences, won’t be penalized Sensation and Perception *parts of body that process incoming + outgoing information -incoming = sensory; outgoing = peripheral NS (movement) *there are 5 recognized senses - the sense we rely on most (VISION) is least developed in infancy! (b/c no prenatal exposure to it; if ur not exposed to particular sensation ur not going to develop it) - the 2 sense we rely on most = hearing *other mammals don’t rely so much on hearing/vision – they are very sensitive to smell, they rely more on their olfactory system; a secondary smell system = volmuranasal sensory system = sense of smell that detects chemical in air called pheromones Senses: -sight = visual system -hearing = auditory system -smell = olfactory system -touch = somatosensory system -taste = gustatory system *good experiment on exposure of sensory system – 1 group deny sensory info; 2 nd group give the sensory info = can’t conduct on humans; can conduct on animals - blinded cats during development (infancy), and cats remain blind (can’t see) Principles of Sensation - transduction = physical energy to neural signal (transducing 5 senses into a neural signal) - incoming info: (1) visual system – process of “see” = incoming info is light (energy - electromagnetic radiation); electromagnetic radiation energy = visual info in terms of light (exists in waves – height of wave is amplitude; distance from wave peak to peak is wavelength) 1.1000 m wavelength = radio wave (or ac/dc) (can’t harm people) 1-0.1 m = radar .1-.00001 = infrared .00001 - .0000001 = ultraviolet *visible band is between the infrared and ultraviolet - @ high end of visible band = red is color detectable - @ low end of visible band = violet is color detectable @ infancy – not particularly well detect the extremes; develop mostly the yellow + green parts of visual band .0000001 - .0000000001 X-Ray (wavelengths are so small they can disrupt matter, can interfere with solid objects) Less than .0000000001 = gamma band (radioactive substances; will disrupt solid matter) (2) auditory system = stimuli are sound-waves (vibrations of molecules in the air); ear is detecting changing in mass in atmosphere around u (3) olfaction = (developed very early on in evolution, don’t need to be exposed to it) detecting chemicals (some are good for u some are bad); infants are motivated towards/away from things due to reaction to chemicals in the air (4) gustatory = sensing chemicals in the mouth – motivating u away/towards things in the mouth (this is built-in, a sensory ability that evolved early, don’t need to be exposed to it; there is a built-in emotional reaction to sour food & sweet food) *sour/bitter indicates poison (poisonous substances typically taste this way) - tastes that we react well to: sweet, salty/savory, fatty (5) somatosensory = (is built-in, see it from infancy although not well developed in infancy – see development in it from general to specific) what is being transduced is pressure, pain, temperature, vibration - absolute threshold = smallest strength of a stimulus that can be detected - difference threshold = (jnd) smallest difference that can be detected - sensory adaptation (disregarding some sensations, ex. there’s 10 pounds of molecules in air – the atmosphere) Vision Purpose of visual system: - Transform light energy into an electro-chemical neural response - Represent characteristics of objects in our environment such as size, color, shape, and location Light = the visual stimulus - We detect between 400-700 of the visual spectrum (which is white light) - Light can be described as both a particle and a wave (exists as a wavicle) - Wavelength of a light is the distance of one complete cycle of the wave - Visible light has wavelengths from about 400nm to 700nm - Wavelength of light is related to its perceived color o The amplitude is related to brightness Components of visual system: - Detection apparatus of visual system = the eye - Outer front part of eye = cornea (is transparent, is pretty hardy) - Cover to the eye = eye-lid, for protection - Pupil = in middle of eye, behind cornea; is a hole (is inside the eye, and no light inside eye so is dark) - Iris = around the pupil, can expand or contract to respond to how much light comes in (has muscles attached to it); comes in assorted colors (most common is brown, least common is green-gray); NOT well-developed in infancy! - Right behind pupil = LENS = involved in accommodation (focusing on objects that are near/far); infants are not good at accommodation (muscles attached to lens to accommodate shapes), and not good at near+far in regards to perception - Inside the eyeball = clear liquid (vitrious and aqrouous humor), keeps the shape of the eyeball - Light hits the back of eyeball, where there are transducers (transduce signals into neural information) - Back layer of back of eyeball – consists of transducers, are cells (like neurons): rods and cones = Retina is the layer (is not well-developed at infancy; newborn infant is functionally blind – has rods (specialized for detecting any wavelength of light in visible spectrum, develop before cones, specialized for contrast-light and dark areas, outline; specialized for detecting movement, or changes in contrast) and cones (specialized for detecting colour, much more sophisticated information) but needs to be exposed to light o *more rods than cones in the retina (very adaptive) o The rods and cones are processed through ganglion cells and bipolar cells (which look like neurons and communicate with each other like neurons do; rhodopsin is chemical that changes in response to light & sends signals to bipolar+ganglion cells; axons of ganglion cells exit through optic nerve on their way to the brain, called the “blind spot” b/c no receptors there)  Area in middle of sensory field where ur not receiving any information but u don’t perceive it; scanning (eyeball making very quick minute movements, called “saccades” – this fills in the “blind spot”) Rods and Cones: -Cones: - allow us to see in bright light - allow us to see fine spatial detail - allow us to see different colors -Rods: - allow us to see in dim light - can not see fine spatial detail - can not see different colors Processing Visual Info: - Ganglion cells – neurons that connect to the bipolar cells; their axons form the optic nerve - Bipolar cells – neurons that connect rods and cones to the ganglion cells - Optic chiasm – point in the brain where the optic nerves from each eye meet and partly crossover to opposite sides of the brain *as optic nerves comes in from each eye, they cross over @ level of hypothalamus (processed contralaterally) *experiment – sew just 1 eye shut, and cats can see but don’t have a sense of depth; perception of depth in cats is not well developed *ventral view of the brain - after optic nerves cross over, they’re called “optic tracts” which project onto visual cortex -b4 the crossover – some axons project onto superior colliculus for orientation processing (well developed in infancy) Hearing: Sound Waves - Auditory perception occurs when sound waves interact with the structures of the ear *there’s no sound in space b/c no air in space - Sound Wave – changes over time in the pressure of an elastic medium ( for example, air to water) *water is better medium for sound! - without air (or another elastic medium) there can be no sound waves, and thus no sound Anatomy of Ear: -purpose of structures in the ear: - measure the frequency (pitch) of sound waves - measure the amplitude (loudness) of sound waves -3 parts to ear: - outer ear = acts as a funnel to direct sound waves towards inner structures - middle ear = consists of 3 small bones (or ossicles) that amplify the sound o the 3 bones are right behind the ear-drum (they are not well-developed in infancy); bones transduce changes in air pressure into neurological signal by amplifying the signal - inner ear = contains the structures that actually transduce sound into neural response o most important structure = cochlea, where receptor cells are (called hair cells) o as u develop, u will lose hair cells; the more hair cells u lose, the harder it is for u to hear things at lower pitches o receptor cells are very much like neurons – and they will NOT regrow!!! * binocularity = disparity; 2 ears give sense of location based on sound *hearing is other sense that is not very developed in infancy, we need exposure to it -transduction of sounds: - structures of ear transform changes in air pressure (sound waves) into vibrations of Basilar membrane (analogy in eye = retina; where hair cells are) -as the Basilar Membrane vibrates ut causes the hairs in the Hair Cells to bend - the bending of the hairs leads to a change in the electrical potential within the cell * Chemical and Body Senses: - Olfaction (smell) - Gustation (taste) - Touc
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