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1. Each retina optic tract optic chiasm (nasal fibers from ganglion cell axons decussate across the midline and join undecussated fibers from temporal half of other retina in the optic tract) optic tract ends in lateral geniculate nucleus of thalamus optic radiation (retrolenticular and sublenticular parts of internal capsule) primary visual cortex above and below calcarine sulcus (striate cortex) Retinotopic map – map of image falling on retina; large number of fibers representing fovea; in visual cortex – retina represented right side up (superior fields below calcarine sulcus, inferior fields above), fovea represented posteriorly at occipital pole (large), periphery anteriorly 2. Deficits in visual fields - Fibers to upper back of calcarine sulcus go through retrolenticular part of internal capsule and to occipital lobe - Fibers to lower bank go through sublenticular part and loop out into temporal lobe (Meyer’s loop) before turning posteriorly toward occipital lobe - Damage in optic radiation or occipital lobe spares part of the large foveal representation (foveal or macular sparing) 3. – Receptive fields of lateral geniculate neurons are similar to those of ganglion cells: input from one eye, center-surround antagonism, some receptive fields are for color and others are for black/white contrast, lot of representation of small foveal receptive fields, LGN neurons project to striate cortex - cortical cells for contrasts have a variety of receptive fields; cortical cells do not respond to diffuse illuminate because there are excitatory and inhibitory regions in receptive fields that cancel each other out; receptive fields are not circular which do not respond well to small spots of light - Cortical cells respond to stripes or edges with a particular orientation; simple cells have excitatory and inhibitory regions in the shape of oriented bars; complex cells respond to oriented lines of a particular length -other neurons are more concerned with color than with black/white contrast; they have circular receptive fields with antagonistic center-surround color properties 4. – visual cortex divided into hypercolumns; within hypercolumns all aspects of the information coming from a particular part of the contralateral visual field are sorted (to association areas); each hypercolumn includes two sets of orientation columns through which all stimulus orientations are mapped out for both eyes; among orientation columns are colorsensitive neurons - Foveal hypercolumns correspond to small areas of visual field and peripheral hypercolumns to larger areas - Form and color processed in ventral areas of occipital and temporal lobes - processing of location and motion takes place in dorsal parts of occipital and parietal lobes 5. – Illumination of either retina causes both pupils to constrict - Sphincter is strong; parasympathetic innervation from oculomotor nerve and ciliary ganglion; activated during pupillary light reflex - Dilator is weak; sympathetic innervation via intermediolateral cell column of spinal cord superior cervical ganglion; preganglionic sympathetics for dilator activated by long descending pathways from ipsilateral half of hypothalamus Pupillary light reflex - Response of illuminated eye is direct reflex; equal response of unilluminated eye is consensual reflex - Afferent impulses travel over ganglion cells in optic nerve; half of them (nasal) cross in optic chiasm - Fibers bypass lateral geniculate nucleus and travel through superior brachium to pretectal area (rostral to superior colliculus at midbrain-diencephalon junction; adjacent to posterior commissure - Pretectal area projects bilaterally to Edinger-Westphal nucleus of oculomotor nucleus (preganglionic parasympathetics neurons reside there) oculomotor nerve ciliary ganglion sphincter