Occipital Lobe Videos: –Brain modules 8,9,10, 11 –Consciousness- Blindsight

EYE

Rods Cones Rods Cones Receptors: rods and cones 120 million120 million peripheryperiphery sensitivitysensitivity night visionnight vision 8 million8 million centralcentral acuityacuity color visioncolor vision

Anatomical Pathway in the Retina

Retina

Optic Nerve Exits

Locating Blindspot

Stare at single star for sec

Color-Deficient Vision People who suffer red-green blindness have trouble perceiving the number within the design

axons of retinal ganglion cells 10 6 axons of retinal ganglion cells from each eye converge at optic chiasm and hemidecussate Retinal Ganglion Cells project to: –20% project to the Superior Colliculus (retinotectal/pulvinar pathway) “where it is” –80% of the axons of retinal ganglion cells project to the Lateral Geniculate Nucleus (retinocortical pathway) “what it is” Occipital Lobe

The Lateral Geniculate Nucleus of Thalamus

Central Visual Pathways: the Visual Cortex Visual Cortex Cortical magnification factor -- foveally weighted: cortical volume is related to retinal area’s spatial resolution -- central 10 degrees of VF around fovea maps to 80% of V1 (primary visual cortex)

Receptive Field Properties of Cortical Neurons Based on Hubel and Wiesel Simple Cells orientation selective Response to spots On - Off regions Responds to edges Complex Cells movement sensitive can’t predict response from static on off receptive fields

Hypercomplex Cells end stopping

Form Perception LGN - Parvocellular System V1 (Interblobs) ---> V2 ---> V3 Inferotemporal Cortex (MT) –complex stimuli - grandmother cells –Damage leads to visual agnosia

Movement Perception Rods LGN - Magnocellular system V1 ---> V2 ---> V5 V5: middle temporal lobe (MT) –Damage - akinetopsia (unable perceive motion)

High-level Visual Processing V1- elementary properties detected (edge,etc) V2 -input from V1 divergence of color, form, location V3 - shape (form) - inferotemporal V4 - color - lingual & fusiform gyri V5 - motion - midtemporal PPC - location - posterior parietal cortex ~

Striate Cortex (V1) Many more dimensions in which receptive fields may be described – or “tuning” –Receptive field size –Sensitivity to motion? –Sensitivity to chages in wavelength? –Orientation selectivity? –Occular dominance?

Striate Cortex (V1) Projection to V1 from magnocellular portion of V1 –Motion sensitivity (direction and velocity) –Orientation sensitivity –Disparity sensitivity Projection to V1 from parvocellular portion of V1 –Wavelength sensitivity –Orientation sensitivity –Disparity sensitivity

V2 – three categories Pale stripes –Wavelength sensitivity –Orientation sensitivity –Disparity sensitivity Thin stripes –Wavelength sensitivity Thick stripes –Motion sensitivity –Orientation sensitivity –Disparity sensitivity

V4 – recordings (Color) Stimuli –light patches of different wavelengths Stimuli –light patches of different wavelengths Neural response Neural response

MT – recordings (Form) stimuli Neural response Neural response

eyetracking