PSY605: Perception

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matthewjlpage
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75525
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PSY605: Perception
Updated:
2011-03-27 21:53:14
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Cognitive Neuroscience Perception
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Chapter 5: Perception
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  1. Is perception faithful replication of stimuli in the environment?
    No -- influenced by top-down processes
  2. Top-Down Processing
    Higher order processes influencing sensations
  3. Transduction
    • Converting stimulus energy to neuronal firing
    • Accomplished by sensory receptors
  4. Types of Sensory Receptors
    • Exteroreceptors - stimulus on body: skin, tongue
    • Telereceptors - Distant stimulus (vision, audition, smell)
    • Proproioceptors - muscles, joints, vestibular system
    • Interoceptors - Internal organs
  5. Four stimulus properties
    • Modality (what) - Type of receptor activated
    • Position (where) - Location of receptors and pattern/frequency of firing (audition, smell)
    • Intensity (how much) - # of neurons firing and frequency of activity (audition, smell)
    • Timing (when) - onset of firing
  6. Principles of Perception
    • 1. Sensory receptors are optimized to detect different stimuli
    • 2. Sensory info is carried along labeled (specified) lines - as long as these neurons are activated, we'll have that perception
    • 3. Center-surround organization
    • 4. Decussation (crossing) of sensory fibers
    • 5. Topographic representation (but distorted) - homunculus
  7. Center-surround organization
    • Center - excitatory
    • Surround - inhibitatory

    Adds precision
  8. Percentage of brain dedicated to vision
    50%
  9. Visual Spectrum
    380 to 760 nanometers
  10. Fovea
    • Subset of retina corresponding to center of visual field
    • Has no rods, only cones
  11. Blind Spot
    • Part of visual scene corresponding to where the optic nerve leaves
    • No visual receptors
  12. Photoreceptor
    • Cones
    • - Color
    • - Found more in fovea

    • Rods
    • - Brightness
    • - Found in periphery of retina (none in fovea)
    • - Important at night
  13. Visual Transduction
    • Photoreceptors (rods and cones)
    • Bipolar Cells
    • Ganglion Cells - (1 million) axos form the optic nerve and exit at the optic disc (which forms the blind spot on the retina)
  14. Primary Visual Pathway
    • Optic Nerve
    • Optic Chiasm - where part of optic nerve crosses over
    • Optic Tract - Portion after chiasm
    • LGN in Thalamus - first point of synapse; relay of visual information
    • Radiations - Portion after LGN
    • Primary Visual Cortex (V1), Visual Cortex
    • Parietal lobe (where/how) and Temporal lobe (what)
  15. Temporal and Nasal Hemiretinas
    • Temporal Hemiretina
    • - Contralateral hemifield's medial portion
    • - Stays on same side

    • Nasal Hemiretina
    • - Ipsilateral hemifield's lateral portion
  16. Lesion of the left optic nerve
    • No input from left eye
    • Left and right visual field in right eye
  17. Lesion at the optic chiasm
    Only see right field in left eye and left field in right eye
  18. Lesion in left optic tract OR radiation
    Both eyes see only see left visual field
  19. Annular Organization
    • Donut shaped
    • Organization in LGN
    • Turns into columnar organization in V1
  20. Columnar Organization
    Organization in V1
  21. Receptive Field
    The area of the retina that, when stimulated with light, changes the cell's membrane potential
  22. Retinotonic map
    • Captures every point in the visual field and maps it onto the retina, V1, etc.
    • Represented in 360 degrees
    • Neighboring cells in the retina feed information to neighboring places in their target structures (i.e. they "stay neighbors" in LGN, V1, etc.)
  23. Receptive Field and Selectivity
    Receptive field - what part of the visual field does a neuron respond to?

    Selectivity - what kind of visual information does the neuron respond to?
  24. Parallel Processing
    Different kinds of visual information are processed in parallel by different neural populations
  25. Response properties o V1 cells
    Hubel and Wiesel (Nobel Prize 1981)
  26. Selectivity of Visual Cortex Areas
    • V1 - Orientation
    • V4 - Color
    • V5 - Motion
  27. What makes a visual region?
    • Cytoarchitecture
    • Intracortical connections
    • Retinotopy
    • Functional properties
  28. Retino-collicular pathway
    • From optic nerve cells --> Superior colliculus (midbrain) --> Pulvinar (thalamus) --> Temporal lobe ("what") and Parietal lobe ("where/how")
    • "Rough and ready" vision
    • Responsible for "blindsight" when main pathway is damaged
  29. Only sense not relayed to thalamus
    • Olfaction
    • Instead goes to Olfactory Bulb
  30. First sense to evolve in cells
    Chemical senses
  31. Glomerulus
    Axons from nasal receptors clumping together in olfactor bulb, form olfactory nerve
  32. Cortex associated with olfaction
    Primary olfactort cortex and secondary olfactory area (orbitofrontal cortex)
  33. Difficulty in imaging olfaction
    • Hard to get signal in fMRI
    • Passive smelling vs. active sniffing
    • Massive amount of habituation in smell
  34. Airflow in Nostrils
    • Smaller nostril (low air flow):
    • -Odorant with high rate of absorption = small neuronal response
    • -Odorant with low rate of absorption = large neuronal response

    • Larger nostril (high air flow):
    • -Odorant with high rate of absorption = large neuronal response
    • -Odorant with low rate of absorption = small neuronal response
  35. Why smells have strong emotional/memory associations
    Close proximity from oldactory buld to hippocampus and amygdala
  36. How is taste coded?
    • No distinct topographic representation in CNS
    • Model 1: Taste receptor-specific signaling pathway defines perception (in PNS)
    • Model 2: Taste neuron projection defines perception (in CNS)
  37. Map of Tongue


    Umami - all over
  38. Location of audition transduction
    • Cochlea - Basilar membrane
    • Inner ear fluid moves hair cells
  39. Auditory pathway
    • Primary recepters (hair cells in the cochlea: Organ of Corti)
    • Intermediate-level relays (MGN of thalamus and inferior colliculus in brainstem)
    • Primary cortical representation (auditory cortex in temporal lobe)
    • Higher integrative areas
  40. Microsmatic
    Compared to most mammals, humans' sense of smell is poor.
  41. Tonotopic organization
    Auditory mapping system - frequency (pitch)
  42. Choroid
    Thick blood cells
  43. Nastagmis
    The eyes are constantly moving so we never actually see our blind spot

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