11 Vision II Image formation http://www.slideshare.net/drpsdeb/presentations Retina • Photoreceptors • Interneurons – Horizontal cells • Horizontal interconnection – Bipolar cells • Vertical interconnection – Amacrine cells • Both horizontal and vertical interconnection • Ganglion cells – AP generation – Transmission of AP to the brain http://www.slideshare.net/CsillaEgri/presentations Retina • Fovea – Low convergence • Small receptive field • High resolution – Lower sensitivity to light • Periphery of retina – High degree of convergence • Large receptive field • Low resolution – High sensitivity to light http://www.slideshare.net/CsillaEgri/presentations Receptive field http://www.slideshare.net/drpsdeb/presentations Receptive field http://www.slideshare.net/drpsdeb/presentations Receptive field http://www.slideshare.net/drpsdeb/presentations Receptive field http://www.slideshare.net/drpsdeb/presentations Receptive field http://www.slideshare.net/drpsdeb/presentations Receptive field • Magnocellular system – Large receptive field – Rods and cones – M ganglion cells (10%) – High speed of velocity – Brightness/low contrast sensitivity – Minimal sensitivity to color • Parvocellular system – Small receptive field – Cones and rods – P ganglion cells (80%) – Low speed of velocity – Low sensitivity in low contrast – Good sensitivity to colour http://www.slideshare.net/drpsdeb/presentations Receptive field • Magnocellular system – Large receptive field – Rods and cones – M ganglion cells (10%) – High speed of velocity – Brightness/low contrast sensitivity – Minimal sensitivity to color • Parvocellular system – Small receptive field – Cones and rods – P ganglion cells (80%) – Low speed of velocity – Low sensitivity in low contrast – Good sensitivity to color http://www.slideshare.net/drpsdeb/presentations Optic nerve and optic tract • Optic nerve – Signal from one eye – Signal from „whole“ visual field • Optic tract – Signal from both eyes – Signal from half of visual field http://www.slideshare.net/CsillaEgri/presentations Visual pathways • Nucleus corporis geniculati lateralis – Thalamus – Majority of projections – Via optic radiation to neocortex • Hypothalamus – Regulation circadian activity • Pretectum – Pupillary reflex • Colliculi superiores – Reflex movement of eyes and head http://www.slideshare.net/drpsdeb/presentations Nucleus corporis geniculati lateralis • Six nuclear layers • Retinotopic organization • Each layer receives input from only one eye • Layers 1-2 – Magnocellular system • M ganglion cells • Large receptive field/brightness sensitivity – Information about localization and movement • Layers 3-6 – Parvocellular system • P ganglion cells • Small receptive field / color sensitivity – Information about form and color http://www.slideshare.net/CsillaEgri/presentations Primary visual cortex Retinotopic organization http://www.slideshare.net/CsillaEgri/presentations http://www.slideshare.net/drpsdeb/presentations Primary visual cortex http://www.slideshare.net/drpsdeb/presentations Spatial vision Binocular http://www.slideshare.net/drpsdeb/presentations Spatial vision Monocular – based on previous experience http://www.slideshare.net/drpsdeb/presentations Motion perception http://www.slideshare.net/drpsdeb/presentations Vestibuloocular reflex http://d2avczb82rh8fa.cloudfront.net/content/jn/92/1/20/F3.large.jpg?width=800&height=600&carousel=1 Nystagmus • Involuntary rhythmic eye movement • Physiological – Postrotatinal – Optokinetic • Pathologic – Vestibular system pathologies – Vestibulocerebellar damage – Other damage of CNS http://dxline.info/img/new_ail/nystagmus.jpg Saccadic eye movements https://en.wikipedia.org/wiki/Saccade#/media/File:Szakkad.jpg Saccadic eye movements https://s-media-cache- ak0.pinimg.com/564x/51/f7/26/51f7267e7c8a59caa90f904cd4f965eb.jpg https://en.wikipedia.org/wiki/Saccade#/media/File:Szakkad.jpg Reflexive exploration Intentional exploration Assistance in controlling saccades during movement http://www.nature.com/nrn/journal/v5/n3/box/nrn1345_BX1.html Pupillary reflex http://www.ubooks.pub/Books/B0/E27R7642/MAIN/images/1509_Pupillary_Reflex_Pathways.jpg