1. Electrical Activity of the Neuron
Sensation and Perception
"Nothing is in the mind that did not first pass through the senses" (Aristotle)
Sensation
stimulation of sense organs (Passive, Physiological)
Perception
selection, organization, and interpretation of sensory input (Active, Cognitive)
Electrical Activity of the Neuron

2. Threshold Psychophysical Relationship Physical Stimulus Sensory
Experience
Transduction
Not all physical stimuli result in sensory experience
Ineffective
Stimuli
Effective
Stimuli
Threshold

3. Absolute Threshold (Absolute Limen)
The minimum intensity of a stimulus that will cause a perception to occur (Weber)
The Test Setting (Complete Darkness)

4. Absolute Threshold (Absolute Limen)
The 50% Detection Level

5. Difference Threshold (Difference Limen)
The smallest degree of change in a stimulus which is detected by the subject (JND or Just Noticeable Difference)
The Test Setting (Dimly Lit Room)

6. Difference Threshold (Difference Limen)
Experiment #1
Required Transition from 60.0 to 61.0 to attain a JND
Experiment #2
Required Transition from to to attain a JND
Experiment #3
Required Transition from to to attain a JND
Size of the JND is not a constant amount but is rather a constant proportion of it initial value
Weber’s Law
To make a stimulus Just Noticeably Different you must change it by a constant fraction of its initial value ΔI
= K I

7. Weber’s Constants
Brightness
1/61
1.6%
Pitch
1/333
0.3%
Lifted Weights
1/51
2.0%
Saltiness
1/5
20.0%

8. Make it Saltier Amount of Salt JND = 3.5 JND = 2.9 JND = 2.4 JND = 4.210 12
14.4
17.3
20.8
25.0
Amount of Salt

9. The Sensory Modalities
Physical Stimulus
Transducer
Perceptual Experience
Light
Eye
Vision
Sound
Ear
Audition
Chemical
(Atomized)
Nose
Olfactory
(Solution)
Tongue
Gustation
Heat, Cold, Mechanical Compression, Tissue Damage
Skin
Tactile

10. Vision
Need to understand the nature of the physical stimulus (Light) as well as the transducing system (the Eye)
Light - is a form of electromagnetic radiation that travels as a wave
Only a narrow band of electromagnetic wavelengths give rise to visual sensation

11. Light

12. Perceptual Properties Amplitude (Intensity)
Vision
Need to understand the nature of the physical stimulus (Light) as well as the transducing system (the Eye)
Light - is a form of electromagnetic radiation that travels as a wave
Physical Properties
Perceptual Properties
Wavelength
Hue
Amplitude (Intensity)
Brightness

13. Perceptual Properties Amplitude (Intensity)
Vision
Need to understand the nature of the physical stimulus (Light) as well as the transducing system (the Eye)
Light - is a form of electromagnetic radiation that travels as a wave
Physical Properties
Perceptual Properties
Wavelength
Hue
Amplitude (Intensity)
Brightness
Purity (Bandwidth)
Saturation

14. Major Structures of the Eye
Retina – contains the light sensitive structures (rods and cones) that transduce light into neural activity

15. The Retina
contains the light sensitive structures (rods and cones) that transduce light into neural activity
Rods -
Very sensitive to light (Scotopic)
Poor acuity
No color capability (monochromatic)
Concentrated in peripheral vision
Maximal sensitivity is at 511 nm
Cones -
Daylight Vision (Photopic)
Allow Color Perception (trichromatic)
Great Acuity
Clustered at the Fovea
Maximal sensitivity is at 555 nm

17. Dark Adaptation
Light sensitive structures of the eye become more sensitive to light when kept in the dark for a period of time
Cones – Dark adapt fully in approximately 7 minutes of darkness
Rods - Dark adaptation requires approximately 25 minutes of darkness

18. Red Lighting in the Cockpit to Protect Rod Dark Adaptation
Light sensitive structures of the eye become more sensitive to light when kept in the dark for a period of time
Cones – Dark adapt fully in approximately 7 minutes of darkness
Rods - Dark adaptation requires approximately 25 minutes of darkness
Red Lighting in the Cockpit to Protect Rod Dark Adaptation

19. Organization of the light sensitive structures of the Retina

20. Pathways of the Optic System

21. Pathways of the Optic System

22. Perceptual Properties Wavelength (Frequency) Amplitude (Intensity)
Audition
Audition is the result of the Ear (Auditory System) transducing Sound into neural activity.
Sound - Vibrations passed through an elastic medium (air, water, solids, anything but a vacuum). As an object vibrates it displaces molecules in the air around it, causing repetitive cycles of compression and rarefaction.
Physical Properties
Perceptual Properties
Wavelength (Frequency)
Pitch
Amplitude (Intensity)
Loudness
Purity (Composition)
Timbre
Range of Audible Frequencies - 20Hz to 20KHz
- Ability to hear high frequencies
goes away with age
- Higher frequencies audible for smaller animals smaller animals

23. The Major Structures of the Ear

24. The Auditory Process Sound waves vibrate the tympanic membrane
These vibrations are passed on to the bones of the middle ear
Stirrup hits against the oval window of cochlea
Sets the fluid inside in motion
Hair cells are stimulated with the movement of the basilar membrane
Physical stimulation converted by the hair cells into neural impulses
The axons of the hair cells form the auditory nerve
The auditory nerve fibers synapse at the medial geniculate of the thalamus before continuing to the auditory cortex (temporal lobes)
The hair cells are lined up on a membrane that runs the length of the cochlea called the basilar membrane.
Sound waves cause the bones of the middle ear to hit against the oval window, a covered opening of the cochlea, which sets the fluid inside in motion.
The hair cells are stimulated with the movement of the basilar membrane and convert this physical stimulation into neural impulses that are then sent throughout the thalamus to the auditory cortex, located mostly in the temporal lobes.

25. Taste (Gustation) Physical stimulus: soluble chemical substances
Receptor cells found in taste buds
Four primary tastes: sweet, sour, bitter, and salty
Taste: learned and social processes
The hair cells are lined up on a membrane that runs the length of the cochlea called the basilar membrane.
Sound waves cause the bones of the middle ear to hit against the oval window, a covered opening of the cochlea, which sets the fluid inside in motion.
The hair cells are stimulated with the movement of the basilar membrane and convert this physical stimulation into neural impulses that are then sent throughout the thalamus to the auditory cortex, located mostly in the temporal lobes.

26. Smell (Olfaction)
Physical stimuli: substances carried in the air dissolved in fluid, the mucus in the nose
Olfactory receptors = olfactory cilia
Synapse directly with cells in brain (only sensory input which is not routed through thalamus)
The hair cells are lined up on a membrane that runs the length of the cochlea called the basilar membrane.
Sound waves cause the bones of the middle ear to hit against the oval window, a covered opening of the cochlea, which sets the fluid inside in motion.
The hair cells are stimulated with the movement of the basilar membrane and convert this physical stimulation into neural impulses that are then sent throughout the thalamus to the auditory cortex, located mostly in the temporal lobes.

27. Tactile Senses
Physical stimuli = mechanical, thermal, and chemical energy coming in contact with the skin
Sensory receptors specialized to some degree for different functions, such as pressure, heat, cold, etc.
The hair cells are lined up on a membrane that runs the length of the cochlea called the basilar membrane.
Sound waves cause the bones of the middle ear to hit against the oval window, a covered opening of the cochlea, which sets the fluid inside in motion.
The hair cells are stimulated with the movement of the basilar membrane and convert this physical stimulation into neural impulses that are then sent throughout the thalamus to the auditory cortex, located mostly in the temporal lobes.