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Psychology 372
Physiological PsychologySteven E. Meier, Ph.D.
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Sensory Systems
Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
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Overview
• Lots of sensation or sensory systems • Whole fields of Psychology are associated with
this area• Examples
• Visual system• Auditory system• Tactile system• Olfactory and Taste system• others
Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Systems overview
• Systems have some type of receptor system
• Receptor systems are designed to convert some outside stimulus to a electrical-chemical signal • Is called transduction
• The electrical-chemical signal is used by the nervous system
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Receptor systems
• Usually lack axons• Usually form synapses with dendrites of
other sensory neurons• Messages are carried on different
pathways to specific areas of the brain• Detect small ranges of energy levels
• Visual system: 400 to 700 nm• Auditory system: 20 to 20,000 Hz
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Receptor systems
• Some systems are more complicated than others
• Visual system versus touch system• Visual system was initially part of brain
systems• Has become more specialized and
moved• Allows more processing of information• Increases survival.
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
The Eye
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Some structures
• Pupil: Is basically a hole• Iris: Is a muscle that controls the size of
the hole• Cornea:
• Is it clear transparent membrane that covers the pupil and Iris
• Focuses approximately 75% of visual information onto the retina
• Lens: Focuses the remaining 25% of light onto the fovea of the retina
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Copyright 2001 by Allyn & Bacon
Rods and Cones
Two types of photoreceptors are located within the retina Rods: 120 million
Light sensitive (not color) Found in periphery of retina Low activation threshold
Cones: 6 million Are color sensitive Found mostly in fovea
Source: http://insight.med.utah.edu/Webvision/imageswv/rodcoEM.jpeg
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Copyright 2001 by Allyn & Bacon
Retinal Circuitry
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Adapted from Dowling, J.E., and Boycott, B.B. Proceedings of the RoyalSociety of London, B., 1966, 166, 80-111.
Copyright 2001 by Allyn & Bacon
Primary Visual Pathway
Information from each visual field crosses over at the optic chiasm and projects to the opposite side of the primary visual cortex
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Copyright 2001 by Allyn & Bacon
Visual Cortex
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Copyright 2001 by Allyn & Bacon
Summary of Visual Cortex
V4: responds to color (and form perception) Lesions of V4 impair color perception
V5: responds to movement TEO: involved in color discrimination, 2-d
pattern discrimination TEO projects to area TE
TE: neurons here respond to 3-d objects (a face or a hand)
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Auditory system
• Is less sophisticated than the visual system
• Designed to transduce frequencies of sound into hearing
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological PsychologyDivisions of the Ear
• Outer ear:• Channel to
tympanic membrane
• Middle ear:• Ossicles
• Inner ear:• Cochlea
Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
The Cochlea
• The cochlea is formed from three chambers:
• Hair cells within the organ of Corti transduce sound waves into nerve impulses
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological PsychologyAuditory Pathways
• Afferent pathways:• Through cochlear nuclei
• To superior olivary nuclei
• To inferior colliculus• To medial geniculate• To auditory cortex
• Efferent pathway:• Olivocochlear bundle
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Touch / Pain
• Three different sensations are reported to the brain by receptors localized within skin
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Temperature
• Is detected by warmth and cold receptors• Receptor activation is relative to the
baseline temperature• The receptors lie at different levels of
the skin (cold are close to the surface of the skin)
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Touch and Pain
• Touch involves perception of pressure and vibration of an object on the skin• Pacinian corpuscles detect deformation
of the skin
• Pain is associated with skin tissue damage • Nociceptors detect pain
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological PsychologyMorphology of Skin
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Dermis
Epidermis
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• The dorsal columns carry precise information related to touch
• The spinothalamic tract carries pain and temperature signals (poorly localized)
• 5-10 cortical maps of the body surface
Somatosensory Pathways
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Other systems
• Taste• Vestibular
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Psyc 372 – Physiological PsychologyPsyc 372 – Physiological Psychology
Conclusions
• Lots of systems• Each has a specific purpose• When damage occurs, usually multiple
systems are impacted.• Creates specific symptomatology• Can be used to identify locations of brain
or system damage
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