1	Sensation & Perception
2	Overview Differentiating sensation & perception Exploring sensation Principles Vision Audition Exploring Perception
3	Sensation or Perception? Sensation = process by which sensory organs respond to environmental stimuli Perception = organization and interpretation of sensory information Sensation and perception can best be viewed as being at opposite ends of a continuum
4	Sensation Transduction = conversion of environmental stimuli into neural impulses Sensory receptors Vision = photoreceptors Audition = mechanoreceptors Smell = chemoreceptors Taste = chemoreceptors Touch = mechanoreceptors
5	Sensation Psychophysics = study of relation between physical stimuli & sensory experience Absolute threshold Difference threshold Weber’s law
6	Sensation Sensory adaptation – Our senses are designed to detect change in the environment Evolutionary advantage Sensory adaptation – > or < sensitivity Contrast effect
7	Sensation Signal detection theory Detecting a stimulus requires a judgment about its presence or absence Noise in the environment Perception of stimuli is always a judgment
8	Vision The eye Rods & cones Visual pathways & transduction Vision theories
9	The Eye The eye is designed to focus and detect light waves Parts of the eye Cornea - protective outer cover Lens - focuses light on the retina through “accommodation” Pupil - controls amount of light getting into the eye Retina – layer of photoreceptors covering the back of the eye
10	The Eye Retina – a layer of photoreceptors and interneurons at the back of the eye Fovea Cones Rods Bipolar cells Ganglion cells Optic disc
11	The Eye Fovea – Pinhead sized are of the retina which receives the most direct line of sight & consists of mostly cones
12	The Eye Cones – Appox 6 million located primarily in the fovea of the retina Color vision Function best in bright light High in acuity (sharp focus & high detail) Low in sensitivity
13	The Eye Rods – Appox 120 million located in periphery of the retina Respond best to low levels of illumination Highly responsive to change in the environment = movement detection Low in acuity & high in sensitivity
14	The Eye Bipolar cells – Link rods & cones together and connect to the ganglion cells Ganglion cells receive input from rods & cones via bipolar cells and exit the back of the eye as the optic nerve Optic disc – the space where the optic nerve exits resulting in a blind spot
15	The Eye Visual fields Each eye has a right and left visual field Rather than information from the right eye going to the left side of the brain and visa versa, information from the right visual field of both eyes goes to the left side of the brain
16	The Eye Visual pathways The optic nerves from both eyes connect to form the optic chiasm an which point the combine Exiting the optic chiasm the optic nerves split again, this time combined based on right or left visual field rather than right or left eye
17	The Eye Visual pathways cont. From the optic chiasm the pathway terminates first in a nucleus of the thalamus and from there is carried to the visual cortex in the occipital lobe
18	Color-Vision Theories
19	Opponent Process Demo
20	Opponent Process Demo
21	Opponent Process Demo
22	Opponent Process Demo
23	Opponent Process Demo
24	Opponent Process Demo
25	Color-Vision Theories The current dual-processing theory of color vision incorporates elements from both the trichromatic and opponent processing theories The tricromatic theory was correct in proposing the existence of three different types of cones The opponent-process theory was accurate in terms of opponent processes, but they occur after the cones not in the cones themselves
26	Audition Ear – detects sound waves Wave frequency determines pitch Wave amplitude determines loudness
27	The Ear Outer ear Auditory canal Tympanic membrane – Ear drum Middle ear Ossicles = Hammer anvil & stirrup
28	The Ear Inner ear Cochlea fluid filled tube shaped in a spiral Basilar membrane varies in thickness as it travels the length of the cochlea Tectoral membrane travels along the cochlea in parallel with the basilar membrane Hair cells are the receptor cells housed in the basilar membrane and attached to the tectoral membrane
29	Coding of Sound Pitch Frequency coding Firing frequency plays a limited role due to limits in how rapidly neurons can fire Useful for low-frequency sounds Supported by identification of a strict match between frequency of sound and firing rate of hair cells
30	Coding of Sound Pitch Place coding is based on properties of the basilar membrane Narrow and stiff at the beginning; wide and flexible at the end Structure allows different areas along the membrane to respond to different sound frequencies (pitch) The narrow stiff end responds to high frequency and the wide flexible end responds to low frequency
31	Activation of Hair Cells The basilar membrane acts like a shaken out sheet Because hair cells are housed in the basilar membrane, but connected to the tectoral membrane, movement along the basilar membrane causes pulling on the hair cells
32	Sensation or Perception?
33	Structure of the Eye
34	The Retina
35	Visual Fields & Pathways
36	The Ear
37	Basilar Membrane