NSCI 110 1st Edition Lecture 22Outline of Last 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 cellsOutline of Current Lecture I. Ganglion cells have concentric, surround-sound, antagonistic receptive fieldsa. Results in distinct action potential ratesb. Receptive fields are larger for cortical cellsi. Simple feature detection cellsii. Complex feature detection cellsiii. Hypercomplex feature detection cellsII. Color is encoded through opponent processinga. Single opponentb. Double opponentCurrentLecture- Ganglion cells have a surround-sound receptive field that is antagonistico Excitatory center and inhibitory periphery (concentric “surround-off”) Vice versa “surround-on”o If a bar of light stimulates both areas on the receptive field, inhibition and excitation will occur simultaneously based on the proportion of the field it stimulates Results in various rates of action potentialsThese 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.- Receptive fields at the cortex are larger than those for ganglion cells because multiple ganglion axons may join at a single cortical cello Simple feature detection cells Rectangular- “On” center and “off” edges above and below Horizontally or oblique preferred - Orientation preferences occur at around every 10 degrees- Different cortical cells prefer different angleso Cells in the same column prefer the same orientation Receptive field originates from a single row of ganglion cells when a bar of light hits the retina (thus forming a rectangular shape)- From a single row, the ganglion cell receptive fields are all off-center or all on-centero Complex feature detection cells Less redundancy prefer bars of light that are moving in a certain orientation and direction- Keeps track of a line that is moving across certain ganglion receptive fields These cells receive information from ganglion cells and also the simple feature detection cells Important for detecting lines, edges, and borders Many found in thick stripes of V2 as well as V1, too responsive to motion- Extend to V5o Hypercomplex feature detection cells Still contain an excitatory portion and inhibitory portion at one end Again, keeps track of moving bars of light Responsible for plasticity when learning- “Off” areas may expand or vice versa Fire best at 90 degree angles- Important for detecting angles of stimuli Have the largest receptive fields of the three feature detection cells Again, found in V2 and V5 because they are responsive to motion- Color is encoded through similar processeso Color is processed through blobs in the cortexo Opponent process opposing colors in concentric receptive fields Single opponent (one color or the other is stimulated) Red and green cones combine signals together to form blueo Double opponent process can occur when both colors are represented in both portions of the receptive field i.e. red inhibitory and green excitatory in periphery and green inhibitory and red excitatory in center of concentric
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