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Sensation and Perception Electrical Activity of the Neuron "Nothing is in the mind that did not first pass through the senses" (Aristotle) Sensation stimulation.

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Presentation on theme: "Sensation and Perception Electrical Activity of the Neuron "Nothing is in the mind that did not first pass through the senses" (Aristotle) Sensation stimulation."— Presentation transcript:

1 Sensation and Perception Electrical Activity of the Neuron "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)

2 Psychophysical Relationship Physical Stimulus Sensory Experience Transduction Not all physical stimuli result in sensory experience Effective Stimuli Ineffective 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 #1Required Transition from 60.0 to 61.0 to attain a JND Experiment #2Required Transition from to to attain a JND Experiment #3Required 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 ΔIΔI I = K

7 Weber’s Constants Brightness1/611.6% Pitch1/3330.3% Lifted Weights1/512.0% Saltiness1/520.0%

8 Make it Saltier Amount of Salt 1012 JND = JND = JND = JND = JND = 4.2

9 The Sensory Modalities Physical Stimulus TransducerPerceptual Experience LightEyeVision SoundEarAudition Chemical (Atomized) NoseOlfactory Chemical (Solution) TongueGustation Heat, Cold, Mechanical Compression, Tissue Damage SkinTactile

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 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 PropertiesPerceptual Properties WavelengthHue Amplitude (Intensity)Brightness

13 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 PropertiesPerceptual Properties WavelengthHue 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

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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 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

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22 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 PropertiesPerceptual 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 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 Auditory Process

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

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)

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.


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