NSCI 110 1st Edition Lecture 21 Outline of Last Lecture I The retina is responsible for relaying detailed images to the cortex a Consists of layers photoreceptors at the back bipolar cells ganglion cells b Contains the fovea where there are only cones II There are two types of photoreceptors in the visual system a Rods vision at night or in dim lighting b Cones color perception and fine details III Light hyperpolarizes receptors a Reduces the amount of glutamate released by photoreceptors IV Lateral interactions also occur among retinal cells surround inhibition a Horizontal cells inhibit nearby bipolar cells b Amicrine cells inhibit nearby ganglion cells V Retinotopic organization exists among both optic pathways Outline of Current Lecture I The tectopulvinar pathway of the visual system sends signals to the superior colliculi II The geniculostriate pathway of the visual system sends signals the lateral geniculate nucleus of the thalamus then the primary visual cortex a V1 is the primary visual cortex striate cortex i Blobs and interblobs send signals to corresponding thick or thin stripes and pale zones b V2 V5 constitute the extrastriate cortex c Consists of dorsal and ventral pathways III Issues arise when there are lesions in the visual cortex a Hemianopia b Quadrantanopia c Scotoma IV Dorsal stream travels to the parietal cortex and ventral stream to the temporal cortex V A receptive field is an area on the retinal surface which when stimulated causes a change in rate of action potentials traveling to visual cortical cells Current 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 to o V2 V3 V4 V5 increasing layer processes more specific information These 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 information o Quadrantanopia occurs when there is a loss in a specific smaller portion of the visual field on one side o 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 simultaneously o Within each of these circuits there is further serial stepwise processing o Dorsal stream originates in the striate cortex and flows to the parietal lobe The where and how Spatial relationships o Ventral stream originates in the striate cortex and flows to the temporal lobe The what Identification and recognition of objects Visual cortex displays columnar organization o Six layers that correspond with the six cortical layers o Most input arrives in layer IV o 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 columns o 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 fields o 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 Inhibition
View Full Document
Unlocking...