Your perceptions would not change the way auditory or

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- Your perceptions would not change – the way auditory or visual information is coded in the brain, does not depend on the physical location of the brain – Seeing something as “on top” or “to the left” depends on which neurons are active and not where those neurons are located The Eye and It's Connections to the Brain - Light enters the eye through an opening in the center of the iris called the pupil - It is focused by the lens (adjustable) and cornea (non-adjustable) and projected onto theRetina– the rear surface of the eye, which is lined with the visual preceptors- Light from the left side of the world, strikes the right half of the retina, light from the below strikes the right half of the retina, and all the light from the top half of the world hits the top half and vice versa - Visual system does not duplicate the image, it codes it by various neuronal activity Route Within The Retina- In the vertebrate retina, messages go from receptors at the back of the eye to bipolar cells – locatedcloser to the centre of the eye – the bipolar cells send their messages to:- Ganglion Cells –located still closer to the centre of the eye – the ganglion cells – located closer to the centre of the eye- Ganglion cell axons join together and travel to the back of the brain - Additional cells called Amacrine Cells get information from bipolar cells and send it to other bipolar, amacrine, or ganglion cells - Light passes through the ganglion cells and bipolar cells on route to the receptors - However, these cells are transparent and light passes through them without distortion
- The Blind Spot: The ganglion cell axons form the optic nerve , which exits through the back of the eye- The point at which the optic nerve leaves, (which is also where the blood vessels enter and leave) is the Blind Spot because it has no receptors - RECAP: What makes the blind spot at the retina?- The blind spot has no receptors because it is occupied exiting ganglion cell axons and blood vessels Fovea and Periphery of the Retina - Fovea – a tiny area used for acuity and tiny detailed vision - Blood vessels and ganglion cells almost absent near the fovea, giving the fovea nearly unimpeded vision - Tight packing of receptors - Each receptor in the fovea connects to a single bipolar cell, which in turn connect to a ganglion cell, which has an axon to the brain - The ganglion cells in the fovea of humans and other primates is called Midget Ganglion Cellsbecause each is small and responds to a single cone - and furthermore, each cone in the fovea is connected to the brain with a direct route that registers the exact location of the input - Because the midget ganglion cells 70% of the input to the brain, are vision is dominated by what we see in the fovea - Toward periphery of retina, more and more receptors converge onto bipolar and ganglion cells, as a result the brain cannot detect the exact location or shape of a peripheral light source - All in all, fovea vision has better acuity (sensitivity to detail) and peripheral vision has better

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