Class Notes (1,100,000)
CA (620,000)
U of G (30,000)
PSYC (4,000)
PSYC 2410 (100)
Lecture 10

PSYC 2410 Lecture Notes - Lecture 10: Ocular Dominance


Department
Psychology
Course Code
PSYC 2410
Professor
Elena Choleris
Lecture
10

This preview shows pages 1-2. to view the full 8 pages of the document.
VISION
Exteroceptive Sensory Systems
Sensation: the process of detecting a stumulus (receptor)
Perception: the higher order process of integrating, recognizing and interpreting patterns
of sensation
Case example: the man who mistook his wife for a hat
Hierarchical Organization
Receptors
Other Structures (e.g. thalamic nuclei)
Cortical Processing:
primary sensory cortex
secondary sensory cortex
association cortex
Hierarchical Organization
Functional Segregation
Parallel Processing
Vision Ch. 6
Produces an internal representation of the outside world
Not always an accurate representation of reality
- a perception of reality based on specific receptors (‘hardware’)
- interspecific differences: e.g. snakes can see infrared; insects see ultraviolet
- intraspecific differences: e.g. colour blindness
- top-down influence: attention, individual experience, etc. affect perception
- e.g. same scene viewed differently by different people with different interests
Perception of light
Light: electromagnetic wave (energy) that can be represented by discrete units/particles
of energy called photons
Very fast, travels at 300 000km/sec
Visible light waves (humans): 380-700 nanometers (billionths of a meter)
Wavelengthscolours
Intensity  brightness
e.g. ‘bright red’ = our perception of high intensity, 700 nm wavelength light
Iris: contractile tissueit regulates the size of the pupil
Wide pupil  more light sensitivity  less acuity
Narrow pupil  lower light sensitivity  higher acuity
Light sensitivity: the ability to detect an object in dim light
Acuity: the ability to see fine details of objects
Binocular vision
Lateral  very wide field of view
Frontal much smaller field of view
Frontal eyes  3-D (depth and distance)

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

VISION
Binocular disparity
Refraction (cornea and lens)
Accommodation (ciliary muscles  lens)
Presbyopia: reduced ability to focus on near objects with age lens is less flexible
Needs glasses for reading (convex lens)
The Retina is INSIDE-OUT
Completion: filling in
Two problems:
1. blind spot
2. distortion
Image Completion… and surface interpolation
The perception of surfaces: the visual system extracts info about edges, and infers whole
surface
Photoreceptors
Cones-rods
Night active, nocturnal, species: great prevalence of rods
Day active, diurnal, species: great prevalence of cones
Duplexity Theory of Vision
Photopic Vision
Scotopic Vision
Scotopic Vision: Rod Mediated
High convergence  high sensitivity + low acuity
In low lighting, the weak signals picked up by several receptors can add up  RGC
Spatial ambiguity  low acuity
Photopic Vision: Con Mediated
Low convergence  low sensitivity + high acuity
More intense signal (light) required to activate RGC
Colour vision mediated by cones
Eye Movement
Saccades: very quick eye movements  temporal integration
Stabilized retinal image  images disappear
Transduction: conversion of one form of energy into another
Visual Transduction: light  neural signals
Rhodopsin: a red pigment in rods (from Vitamin A)
Rhodopsin:
Dark  Red
Light  Bleaching
Pigment: a protein that absorbs light (e.g. clorophyll)
You're Reading a Preview

Unlock to view full version

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

VISION
Visual Transduction – RODS
In the Dark
Rhodospin is inactive
cGMP keeps Na+ channels open (cGMP: cyclic Guanosinemono-phosphate)
Na+ influx partially depolarizes the cell membrane
Rods continuously release glutamate
In the Light
Rhodopsin: G-protein coupled membrane receptor is activated by light
cGMP is broken down
Na+ channels close
Partial hyperpolarization of the cell membrane
Glutamate release is blocked
Retina-Geniculate-Striate Pathway
Nasal hemiretinas decussate in the optic chiasm (contralateral)
Temporal hemiretinas do not decussate (ipsilateral)
RIGHT visual field  LEFT primary visual cortex
LEFT visual field  RIGHT primary visual cortex
Retinotopic Organization: each level of the visual system maintains a map-like
organization of the visual field (i.e. the relative position of two points in the visual field is
maintained in the activation of the CNS).
Lateral Geniculate Nucleus
6 layers of cells:
4 Parovocellular (P) Layers (small cells): colour, fine detail
2 Magnocellular (M) Layers (big cells): movement
M and P layers form distinct and separately processed projections to the cortex
Each LGN receives input only from contralateral visual field
Edge Perception
Edges define the extent and position of objects
Perception of an edge  perception of contrast
Contrast Enhancement
Contrast Enhancement Through Lateral Inhibition
Firing rate ~ light intensity
Lateral inhibition
A,B,C: same high light intensity and same high inhibition
D: high light low inhibition (from E)
D: fires at higher rate
E: fires at lower rate (low light high inhibition from D)
You're Reading a Preview

Unlock to view full version