NSCI 110 1st Edition Lecture 21 Outline of Last Lecture I. The retina is responsible for relaying detailed images to the cortexa. Consists of layers photoreceptors at the back, bipolar cells, ganglion cellsb. Contains the fovea, where there are only conesII. There are two types of photoreceptors in the visual systema. Rods vision at night or in dim lightingb. Cones color perception and fine detailsIII. Light hyperpolarizes receptorsa. Reduces the amount of glutamate released by photoreceptorsIV. Lateral interactions also occur among retinal cells (“surround inhibition”):a. Horizontal cells inhibit nearby bipolar cellsb. Amicrine cells inhibit nearby ganglion cellsV. Retinotopic organization exists among both optic pathwaysOutline of Current Lecture I. The tectopulvinar pathway of the visual system sends signals to the superior colliculiII. The geniculostriate pathway of the visual system sends signals the lateral geniculate nucleus of the thalamus, then the primary visual cortexa. V1 is the primary visual cortex (striate cortex)i. Blobs and interblobs send signals to corresponding thick or thin stripes and pale zonesb. V2-V5 constitute the extrastriate cortexc. Consists of dorsal and ventral pathwaysIII. Issues arise when there are lesions in the visual cortexa. Hemianopiab. Quadrantanopiac. ScotomaIV. Dorsal stream travels to the parietal cortex and ventral stream to the temporal cortexV. A receptive field is an area on the retinal surface which when stimulated causes a changein rate of action potentials traveling to visual cortical cellsCurrent Lecture- Tectopulvinar visual pathway allows detection of movement by sending signals to the superior colliculus- VI (primary visual cortex) is where the bulk of information from the LGN travels too V2, V3, V4, V5 increasing layer processes more specific informationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. All constitute the extrastriate cortex - A hemianopia occurs in the cortex when one side does not process informationo Quadrantanopia occurs when there is a loss in a specific, smaller portion of the visual field on one sideo Scotoma is very hard to detect because the loss in the visual field is so small Eye compensates when scanning and person barely notices- Visual system processing is divided into two major parallel circuits simultaneouslyo Within each of these circuits there is further serial (stepwise) processingo Dorsal stream originates in the striate cortex and flows to the parietal lobe The “where” and “how” Spatial relationshipso Ventral stream originates in the striate cortex and flows to the temporal lobe The “what” Identification and recognition of objects- Visual cortex displays columnar organizationo Six layers that correspond with the six cortical layerso Most input arrives in layer IVo Layers I-III contain the “blob” Where information about the hues of colors is processes Everything surrounding in the interblob tissue There are blobs in adjacent vertical columnso Information from the LGN is sent to blobs Blobs process info and send signals to corresponding thin or thick stripes or pale zones in V2 Information then sent to V3, V4, or V5- V3A (form) and V5 (motion) in the dorsal stream sent to the parietal lobe- V3 (dynamic form) and V4 (color form) in the ventral stream sent to the temporal lobe- Feature detection and receptive fieldso A receptive field is an area on a receptor surface (certain number of receptors of ganglion cells) which when stimulated causes a cortical neuron to change the rate of its action potentials Baseline (12/second) Excitation
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