Visual

• superior colliculus: inputs in voluntary control saccades (REMs to salient stimuli) and in coordinating movements of head in concert with this
• -pretectal nuclei participate in pupillary reflexes

the CNS

"blind spot" - where aonx exits and blood vessels pass

area of highest visual acuity

centre of macula

• photoreceptors -rods (night vision)
• and cones (for daylight and colour, densest just around fovea)

bipolar neurons; horizontal (more superficial) and amacrine (deeper). both perform laternal interactions, which enhance visual contrast

ganglion cells. light goes thru to outermost layer, hits photoreceptor cells

input from small # of cones for high visual acuity

input from several rods for convergence and increased sensitivity at low illumination

• pigmented epithelium- phagocytic role for removing old photoreceptors
• functions is absent in retinosa pigmentosum, which can detach retina

• bipolar neurons and ganglions cells process signal
• -in fovea, 1 cone -> 1 bipolar cell --> 1 ganglion cell

highest acuity

• many rods --> 1 bipolar cell
• which acuity is decreased

other cells in retina participate in signal processing

and exit at optic disk, become myelinated and form optic nerve

optic chiasm: partial cross-over

from both sides cross ovver (temporal stay ipsilateral); allows for complete cross-over of each visual field

L visual cortex

• do not go LGN of thalamus, but travel to brachium of superior colliculus
• -

• 1st layer;
• other layers receive input from 1st or from somatic sensory (AL system) and auditory systems
• -sensory info fr. differ modlities is lined up in differ layers -->output to eye and neck muscles so that one can properly orient to stimulus

• a nucleus in thalamus, which projects to the primary visual cortex and serves visual perception
• -laminated (6 layers) with alternating input from ipslateral and contralateral retina

• Magnocellular & Parvolcellular
• -project to distinct parts of primary visual cortex

from M ganglion cells wwith wide dendritic arbours (integrates visual input info from wide area for motion vision)

• from P cells (ganglionic cells with small dendritic arbours)
• -for discriminative aspects of visual form and colour

course anterior for a short distance in order to mvoe over the lateral ventricles

primary cortex, in columnar fissure

densest projection to primary visual cortex (like other sensory)

• ocular dominance columns, orientation columns, aggregates of colour-sensitive neurons (colour blobs)
• -neurons lined up with similar properties across diff layers

lacking of Stripe Gennari

Magnocellular system to the primary cortex to higher order areas for visual form in mtoion (includes medial temporal projection)

parvocellular system to primary cortical projections in 4CB to colour blobs to higher order areas

parvocellular system to 4CB to region between blobs to higher order cortex and inferior temporal lobe

• ventral: features :what
• dorsal: spatial info: 'where"

transection = monocular blindness

• (eg. pituitary tumor)
• -transection --bitemporal visual field deficit

transection: contrlateral visual field deficits (homonynous hemianopsis

• transection of meyer's loop only (temporal region --contralateral upper quadrant (quandranotopia
• complete transection --homonymous hemianopsia

• most common
• infarction - homonymous hemianopia with macular sparing (secondary greater cortical representation)