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  • contrast sensitivity

    Robert.Hess@McGill.CA

  • Receptive fieldThe region of retina over

    which a stimulus affects the electrical activity of a neuron

    -- -

    --

    ---

    -+ ++ +

    --

    -

    bipolar cellin vivo

    + ++ +

    -- -

    --

    ---

    -+ ++ +

    --

    -

    ganglion cellin vivo

    receptorin vitro

  • Receptive field of a ganglion cell

    1-10Light stimulus Light in

    RF centre

    RF peripheryCentre andperipheryOn-centre neuron

    Off-centre neuron 1s

    RF centre

    RF peripheryCentre andperiphery

  • Orientation tuning

  • A cortical binocular cell

  • Ocular dominance

  • Ocular dominance columns

  • Orientation columns

  • A sinusoidal grating

  • contrast

  • Spatial frequency

  • A neuron as a spatial filter

  • Filtering along the pathway

  • A spatial analysis

  • Contrast responses

    1.0

    0.5

    Contrast %0.1 0.3 1.0

    Sens

    itivi

    ty

    P-cells

    threshold saturation

  • Contrast vs spatial frequency

    SPATIAL FREQUENCY (cycles/degree)

    CON

    TRA

    ST S

    ENSI

    TIV

    ITY

  • Window of visibility

    SPATIAL FREQUENCY (cycles/degree)

    CON

    TRA

    ST S

    ENSI

    TIV

    ITY

  • Spatially-tuned channels

    SPATIAL FREQUENCY (cycles/degree)

    CON

    TRA

    ST S

    ENSI

    TIV

    ITY

  • Temporal response of a neuron

    1.0

    0.5

    Temporal Frequency (hz)1 10 100

    Sens

    itivi

    ty

  • Human temporal sensitivity

  • Peripheral sensitivity

  • Types of retinal ganglion cell

  • Magno & parvo layers

  • An isoluminant grating

  • Colour vs luminance CSF

  • Robert F Hess

    Amblyopia: a new view

    McGill Vision Research Unit Dept. of Ophthalmology, McGill University, Canada

  • The Stimuli

  • Visual Development

    Eileen Birch

  • Days of recovery

    G

    ratin

    g ac

    uity

    (c/d

    egre

    e)

  • Gaussian size (sd min)

    Alig

    nmen

    t acc

    urac

    y (m

    in)

    Monocular deprived cats

  • Strabismic cats

    Gaussian size (sd min) Alig

    nmen

    t acc

    urac

    y (m

    in)

  • Unrelated to visibility loss

    Positional loss

    A

    cuity

    loss

    Cont

    rast

    sens

    itivi

    ty lo

    ss

  • Stimuli: positional sensitivity

  • Amblyopes

  • Contrast sensitivity ratio (dB)

    Alig

    nmen

    t acc

    urac

    y ra

    tio

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