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

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

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

Absolute Threshold (Absolute Limen) The 50% Detection Level

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)

Difference Threshold (Difference Limen) Experiment #1 Required Transition from 60.0 to 61.0 to attain a JND Experiment #2 Required Transition from 120.0 to 122.0 to attain a JND Experiment #3 Required Transition from 600.0 to 610.0 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

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

Make it Saltier Amount of Salt JND = 3.5 JND = 2.9 JND = 2.4 JND = 4.2 10 12 14.4 17.3 20.8 25.0 Amount of Salt

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

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

Light

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

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

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

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

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 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

Organization of the light sensitive structures of the Retina

Pathways of the Optic System

Pathways of the Optic System

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

The Major Structures of the Ear

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.

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.

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.

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.