Chapter 4 Sensation What Do Sensory Illusions Demonstrate? Streams of information coming from...
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Transcript of Chapter 4 Sensation What Do Sensory Illusions Demonstrate? Streams of information coming from...
Chapter 4Sensation
What Do SensoryIllusions Demonstrate?
• Streams of information coming from different senses can interact.
• Experience can change the sensations we receive.
• “Reality” differs from person to person.– Our sensory systems create our personal
reality.
Figure 4.1: Elements ofa Sensory System
The Problem of Coding
• How are physical properties coded into neural activity?
• Doctrine of Specific Nerve Energies
• Types of codes– Temporal– Spatial
Linkages: Sensation andBiological Aspects of Psychology
• Organized sensory information is called a representation.
• Shared features of representations of vision, hearing, and skin senses:– Information from each sense reaches the
cortex via the thalamus.– Representation of world is contralateral to
the part of the world being sensed.
Linkages: Sensation and Biological Aspects of Psychology (cont’d)
• Shared features (cont’d.):– The cortex contains topographical
representations of each sense.– The density of nerve fibers in a sense organ
determines how well it is represented in the cortex.
– Each region of primary sensory cortex is divided into columns of cells that have similar properties.
– Regions of cortex other than the primary areas do additional processing of sensory information.
Sound
• A repeated fluctuation in the pressure of air, water, or some other substance.– Produced by vibrations of an object
• Wave: Repeated variation in pressure that spreads out in three dimensions.
Continue
Physical Characteristics of Sound
• A waveform represents a wave in two-dimensions.
• Characteristics of Waveforms– Amplitude– Wavelength– Frequency
Return
Figure 4.2:Sound Waves and Waveforms
Psychological Dimensions of Sound
• Loudness
• Pitch
• Timbre
Figure 4.3: Structures of the Ear
Conduction Deafness
• The three tiny bones of the middle ear are fused together.
• Prevents accurate reproduction of vibrations.
• Surgery can break bones apart or replace them with plastic ones.
• Hearing aids can also help.
Nerve Deafness
• Results when the auditory nerve or the hair cells are damaged.
• Can be caused by extended exposure to loud noise.
• Cochlear implants can stimulate the auditory nerve.
• Hair cell regeneration as a possible treatment.
Auditory Pathways
• Auditory nerve brainstem thalamus
• Various aspects of sound processed in different regions of auditory system
• Certain parts of auditory cortex process certain types of sounds
Sensing Pitch
• Different people may experience the “same” sound as different pitches.
• Pitch-recognition abilities influenced by genetics.– Cultural factors are also partly responsible for
the way in which a pitch is sensed.
Locating Sounds
• Determined partly by the very slight difference when sound arrives at each ear.
• The brain also uses information about the difference in sound intensity at each ear.
Coding Intensity and Frequency
• The more intense the sound, the more rapid the firing of a given neuron.
• Frequency appears to be coded in two ways.
Coding Frequency: Place Theory
• Sounds produce waves that move down the basilar membrane.– Where the wave peaks depends on the
frequency of the sound.
• Hair cells at a particular place on the membrane respond most to a particular frequency.
• But how are very low frequencies coded?
Coding Frequency:Frequency Matching Theory
• Firing rate of an auditory nerve matches a sound wave’s frequency.
• Sometimes called the volley theory of frequency coding.
The Ear and Sound Waves: Part I
The Ear and Sound Waves: Part 2