1. The Five (?) Senses

2. What a “Sense” Is Sensory Receptors detect some stimulus in the world
Objective sensual data: waves of energy, vibrations, chemicals, pressure
Associated brain areas interpret and reconstruct that information (perception)
Interpretation is based on subjective elements
Perceived information is then integrated into a holistic “experience”

3. So in other words:
1. Objective information is detected by sensory receptors, converted into neural impulses via transduction
2. Those impulses are filtered, interpreted, and integrated into our conscious experience based on what we know, anticipate, expect, or desire
Objective data points are converted into a single subjective experience

4. Sensation The detection of a stimulus Occurs in the Sensory Receptors
Dependent on whether the stimulus is above the Absolute Threshold
Detectable 50% of the time on average
Sensory Adaptation or “habituation” is the gradual decline in sensitivity to a stimulus
Receptors “tire” and stop responding to chronic stimuli

5. Perception Occurs in the Brain
Sorts information based on importance, frequency, etc.
Conscious vs. Unconscious (subliminal) perception

6. The Senses: Vision Objective data are waves of radiation; light waves
Reflected off of surfaces and detected by the rods and cones (sensory receptors)
Limited range: the Visible Light Spectrum
Different wavelengths correspond to colors
Infrared and ultraviolet – just beyond the VLS

7. Anatomy of the Eye

8. Anatomy of the Eye
Cornea – the clear “bulge” directly over the pupil/iris
Iris – contracts or dilates to allow in the correct amount of light (the opening is the pupil)
Lens – thickens or bends (accommodates) to focus light on the retina
Near and far-sightedness are the result of improper focusing by the lens
Retina – contains rods and cones

9. The Retina Contains rods and cones The Fovea The Blind Spot
More rods than cones
The Fovea
Concentration of cones
The Blind Spot
Optic nerve exit; no rods/cones

10. Rods and Cones
Rods are concentrated in the periphery of the visual field
Sensitive to motion, light/dark contrast
Cones are concentrated in the middle of the visual field
Sensitive to detail, color
Concentrated around the fovea, where light is generally focused
Look directly at something to see detail

11. Visual Processing
Begins when stimulated rods and cones send a neural signal (transduction) through bipolar cells to the ganglion cells
One ganglion cell for each “visual field;” higher ratio of ganglion cells for cones than for rods
Information from 10,000 cones becomes one neural signal
Ganglion cells “perceive” – most important information from that field

12. Ganglion Cells The first step in perception
Actually cells from the cortex; capable of analysis and sorting
Reduce “noise” by limiting the number of signals
The primary visual cortex receives only important information
GC → Optic Nerve → Optic Chiasm → PVC

13. Color Vision
Color is the way we perceive different wavelengths of light
Objects do not have “color” objectively speaking
Color vision is subjective, dependent on (1) the operation of the cones and (2) cultural considerations such as language
Color has three “qualities

14. Hue Hue is what we generally mean by the word “color”
Refers to the wavelength associated with that particular light

15. Saturation and Brightness
Saturation is the color's “purity”
Brightness is its perceived “intensity”

16. Theories of Color Vision
Tri-Chromatic Theory
Cones are either red, blue, or green sensitive
Other colors are perceived when two or more different conical groups are stimulated (i.e., yellow is red and green both being stimulated)
Explains deficits in color vision such as colorblindness

17. Colorblindness The inability to distinguish between certain colors
Results from a lack of either red or green cones
i.e., no green cones, so red and green wavelengths trigger only red

18. What do you see?

19. How about now?

20. This one?

21. Another Theory Opponent-Process Theory
Rods and Cones work in opposing pairs
When one is active, the other is inhibited
When an active member stops, the opposing member is temporarily active
red/green, blue/yellow, light/dark, motion (rods)

22. Afterimages Stare at the flag for 30 seconds, and then close your eyes
What do you see?

23. Try This One Black and white contrast activates rods
When you look away or close your eyes, the opponent rods become active, reversing the contrast

24. Visual Perception: Gestalt Principles
Lead to the perception of unified wholes
Perceptual constancy – even though aspects of an object change, perception of the whole does not
Perceptual grouping rules – govern how objects fit together

25. Perceptual Grouping Proximity Closure Similarity Continuation Symmetry
Simplicity
Common Fate

26. Depth Perception Monocular Depth Cues: Linear perspective
Texture gradient
Familiar size
Interposition

27. Binocular Cues Retinal Disparity
Difference in time between signals gives the sensation of depth
Pencil trick

28. Motion Perception
Rods also sense the speed and directionality of motion
Opponent-Processes create strange effects when opponent rods are activated
like this
and THIS!

29. The Senses: Audition Sensing and perceiving sounds
Objective data are vibrations or “sound waves”
Sensory receptors are located in the ears: hair cells
Processing is done in the primary auditory cortex of the temporal lobe

30. Qualities of Sound Amplitude (loudness) – Dbs
Pitch (frequency) – vibrations per second (hertz)
Timbre (color) – overtones and harmonics, rather than pure tones

31. The Outer Ear
Sound waves are collected by the Pinna, and then directed to the ear canal
Sound travels through the ear canal to the ear drum

32. The Middle Ear The ear drum transfers vibrations to the ossicles
Hammer (malleus), anvil (incus), stirrup (stapes)
Amplify sound, transmit to oval window

33. The Inner Ear Oval window transfers vibrations to the cochlea
Contains the basilar membrane, which contains hair cells
Hair cells bend, creating nerve impulses

34. Deafness Conduction Deafness Nerve Deafness
Damage to ossicles or other amplification agents
Can be treated with amplifiers (hearing aids)
Nerve Deafness
Damage to the hair cells themselves
Permanent – requires cochlear implants

35. Chemical Senses: Taste and Smell
Objective data are chemicals
Olfaction (smell) and gustation (taste)
Linked together
Direct, physical contact with the thing sensed

36. Olfaction
Molecules in the air come in contact with olfactory receptors in the nasal cavity
Each chemical stimulates a pattern of nerves
Impulse sent to olfactory bulb

37. Olfaction
Neural impulses are sent to the olfactory bulb, and then the temporal lobe and limbic system
Bypasses the thalamus
Smells are closely linked to emotions and memories
Memory for smells tends to persist longer than other memories

38. Gustation Sense receptors are taste buds
Specialized for sweet, salty, sour, bitter, and umami
“taste” is weak; requires cooperation from smell

39. The Fifth Sense: Touch Pacinian corpuscles measure pressure
Differences in gradation stimulate different nerves, creating the perception of texture

40. The Sixth Sense (?): Temperature
Thermoreceptors detect heat
Respond to changes in skin surface temperature

41. The Seventh Sense: Pain
Nocireceptors respond to damage, stress
A-delta fibers transmit fast, sharp pain
C fibers transmit slow, dull pain

42. Pain Perception
Pain is the “unpleasant” sensation associated with damage or injury
Modulated by psychological factors
The Gate-Control Theory
Pain can be modulated by sending signals to “close” the “gates” that allow pain signals through
Accomplished by rubbing the affected area
Works for dull pain

43. Senses 8 and 9 – The Body Senses
The Kinesthetic Sense – body location and posture
Proprioreceptors in muscles and joints track information about location, muscle tone, movement
The Vestibular Sense – balance
Crystals in the semicircular canals of the inner ear shift as orientation changes
Infection, illness, or sudden changes in air pressure can cause dizziness or vertigo