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Chp. 5 textbook notes

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Steve Joordens

PSY – Chap 5 Notes: Sensation Sensory Processing • Experience is distinguished between sensation and perception o Sensation: the detection of simple stimuli (bright, warm) o Perception: detection of objects, their location, movement, etc.  Seeing the colour red is sensation; seeing a red apple is perception • Our sensory mechanisms: visual, auditory, gustatory, olfactory, somatosensory • Transduction: sense organs convert energy from environmental events into neural activity. Transduction is received by Receptor cells- which release neurotransmitters that stimulate other neurons and alter the rate of firing of their axons. • The body can discriminate between different stimuli by using code: o Anatomical coding: different features are coded by the activity of different neurons o Temporal coding: different features are coded by the neural pattern of activity. Rate of firing tells how intense a stimulus is. • Psychophysics: “physics of the mind.” Studies the relationship between physical stimuli and perceptual experience • Just Noticeable Difference (jnd): smallest difference between 2 similar stimuli that can be distinguished. o The energy necessary to produce a jnd increases with the magnitude of the stimuli • Signal Detection Theory: every stimulus requires distinction between Signal and Noise (background stimuli + random nervous system activity) o Also emphasizes that sensory experience involves factors other than the activity of the sensory systems- such as motivation and experiences • Threshold: the line between not perceiving and perceiving. • Difference threshold: the jnd can be called a difference threshold- the minimal detectable difference between 2 stimuli • Absolute threshold: the minimum value of a stimulus that can be detected- from no stimulus at all. • Response bias: tendency to say “yes” or “no” when you are not sure whether you detected the stimulus • Receiver Operating Characteristic Curve (ROC curve): a graph of hits and false alarms of participants under different motivational conditions. Indicates people’s ability to detect a particular stimulus. Vision • In order to perceive an image clearly, our eyes are constantly making small movements • Cornea: transparent tissue covering the front of the eye • Sclera: the tough outer layer of the eye, the “white” • Iris: the pigmented muscle of the eye that controls the size of the pupil • Lens: the transparent organ situated behind the iris, helps focus an image on the retina • Retina: tissue at the back on the eye ball, contains the photoreceptors and associated neurons • Accommodation: changes in the thickness of the lens of the eye that focus an image on the retina • Photoreceptor: neuron that transduce light into neural activity (cone or rod) • Optic disc: all the axons leave the eye at this point and join the optic nerve, which travels to the brain • Bipolar cell: a neuron in the retina that receives info from photoreceptors and passes it on to the ganglion cells • Ganglion cell: neuron in the retina, receives info from bipolar cells, its axons proceed thru the optic nerve to the brain • Rod: sensitive to light but cannot detect colour • Cone: responsible for day time and colour vision • Fovea: small pit in the centre of the retina (contains densely packed cones). Responsible for our most acute vision • Photopigment: a complex molecule found in photoreceptors, when struck by light, it splits and stimulates the membrane of the photoreceptor in which it resides. Rhodopsin is the photopigment in rods. • There are 3 types of purposive movements: o Vergence: 2 syes cooperate to look at the same thing o Saccadic: rapidly scanning a visual scene o Pursuit: ability to maintain/follow a moving object • Vision is a Synthetic Sensory Modality: it synthesizes (puts together) rather than analyzes (takes apart). When 2 colours mix, we see the intermediate- not the 2 separate • Cones in the human eye contain 3 types of photopigments: Blue, Green, Red o There are more green and red, less blue • Trichromatic Theory: the theory that color vision is accomplished by 3 types of photoreceptors, each of which is maximally sensitive to a different wavelength of light • The ganglion cells are yellow/blue and red/green. How does the brain know whether the light is green/red, if the 2 colours are located on the same cell? o The Opponent Process: the colours are represented by the rate of firing (fast=red , slow=green)(fast=yellow , slow=green) • Forms of color blindness: o Protanopia: defective red cones o Deuteranopia: defective green cones o Tritanopia: lack of blue cones Audition • Ossicle: the 3 bones in the ear: hammer, anvil, stirrup) • Cochlea: snail shaped chamber where auditory transduction takes place • Basilar membrane: contains auditory receptor cells. Within the cochlea • The oval window and round window are both holes in the cochlea with membranes. In the oval window, the stirrup presses against the membrane and transmits vibrations to the fluid in the cochlea. In the round window, the displacement of this fluid causes the membrane here to flex. • All of these vibrations in the cochlea cause neural activity when the cilia of the Auditory hair cells on the basilar membr
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