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March 20, 2021

[Brain Image]    

PSY 340 Brain and Behavior

Classes 18 & 19: How the Brain Processes Visual Information/Early Experience OUTLINE

   

This outline page is meant to be used in class to accompany the longer notes and summary diagram (in pdf format) that I posted on the Lectures page. You should make sure you have a copy of that summary diagram for use in Test #2.

I am combining Sections 5.2 & 5.3 in our textbook and treating them according to my own approach (which will also talk briefly about early development issues in the next class).
Processing in the Retina

[Diagram of Eye and Retinal Layers]

Bipolar Layer: Lateral Inhibition

[Lateral Inhibition]

Ganglion Layer: The Notion of Receptive Fields

[Ganglion receptive fields]

Three types of ganglion cells:
  • Parvocellular (parvo = small) (or midget ganglion) responsive to detail, color
  • Magnocellular (magno = large) (or parasol ganglion) responsive to movement, overall pattern, no color
  • Koniocellular (konio = dust-like) (or bistratified ganglion) responsive to ? (perhaps color perception, esp. blue)


Pathway from Retina to Occipital Lobe

(Visual
                Pathway)


Summary Diagram

Visual
          Processing Diagram
Occipital Cortex: Blindsight & Processing

Visual Processing in the Cortex (Lateral & Medial
            View)

Damage to occipital cortex leads to blindness, but some people experience blindsight  Why?
1. There may be small areas of healthy tissue: not enough for conscious perception, but enough to support some functions

2.
Possibly because of connection between koniocellular layer of the  LGN and area MT/V5 (Ajina et al. 2015; see below)
Blindsight Explanation
Processing Shape: Occipital Cortex

Hubel & Wiesel's Cat Experiment: Visual Cortex Response to Light

Hubel & Wiesel
• First at Johns Hopkins and then Harvard University Medical School David Hubel and Torsten Wiesel worked as researchers on the visual system. They recorded electrical activity from individual neurons in the brains of cats. Their findings won them the Nobel Prize for Physiology or Medicine in 1981.

•  Video of recording from visual cortex cell recording (3'15")
[Hubel & Wiesel Cat Experiment]

Occipital cortex is extracting shape information from data in V1 & V2
V1 Columnar Architecture

Stereoscopic Depth Perception

[Stereoscopic Depth
                  Perception]


The Dorsal vs. Ventral Streams
Dorsal
        vs. Ventral Stream in Visual Processing

Dorsal (Where/How) Stream [Parietal Lobe]

Ventral (What) Stream (What/Object Recognition) [Temporal Lobe]



[Famous Faces]

[Facial recognition]


[Unusual Point of View Test]



Class 19: Vision: Infants and Early Experience

A. Infants & Vision
Infant
                Face Preferences
  • Preference for Faces
  • Inability to look away from moving objects to stationary objects (even still difficulty at 6-7 years old)


B. Early Experience: Impact upon Visual Development

strabisms
  • Experiences "fine tune" the neural visual system to see the world accurately
  • Sensitive or critical periods for experiences to have effect upon the nervous system
  • Strabismus (eyes not point in same direction) ==> impaired stereoscopic depth perception
  • Amblyopia ("lazy eye") can lead to blindness in eye. Eyepatch used to treat it
  • Impaired vision in infancy and early childhood leads to long-term visual defects in adulthood
    • Cataracts corrected after age 7: children have impairment for motion & depth perception


This page was first posted March 7, 2007