Integrative Neuroscience- Vision

• Where do all information go to broadly?

  V1= striate cortex/ visual cortex 1 in the occipital lobe
• "what" pathway (ventral stream)


  Temporal lobe
• The "Where" Pathway(Dorsal stream)


  Parietal lobe
• Where do all the cells go to?

  4C layer
• Parvocellular vision laminae


  4C BETA
• Magnocellular vision laminae


  4C ALPHA
• Parvocellular cells layers


  3-6
• Magnocellular cells layers


  1-2
• magnocellular cells


  have very high temporal resolution but low spatial resolution so it can provide a blurry but moving image of an object
• parvocellular cells


  shape is detected by parvocellular cells which have very high color spatial resolution and permit us to see very fine detail but have low temporal resolution.

  SMALL
• The LGN contains what type of cells?


  Parvo, magno and konio
• Lesion on the striate cortex?


  complete blindness in one visual hemifield
• Lesion of myer's tract?


  Loss information of three quadrants on both eyes
• Lesion of the optic tract on the left eye?


  Loss of information on the right side of both eyes.
• What happens when there's a lesion on the optic chiasm?


  Loss of peripheral or temporal vision on both eyes
• What happens when there's a lesion of right eye optic nerve?


  Complete loss of sight on the right eye
• The Baum's and myer's loop are called?


  Optic radiation
• visual field pathway


  The eyes are seperated into 4 quadrants. The 2 quadrants closest to the nose are called the nasal retina and the other 2 quadrants are called the temporal retina.

  
  

  The nasal retina takes information from the peripheral(Temporal) visual field ipsilaterally.

  Then the temporal side of the eye takes information from the forward side or nasal visual field contralaterally.

  
  

  Once in, information from the temporal side of the eye goes down ipsilaterally, while information from the nasal side crosses over via optic chiasm. In that process all information from the left visual field goes to the right side, and all information from the right visual field goes to the left side.

  Then information proceeds ipsilaterally via optic tract to the LGN. From there it enters the myer's loop which sends information to the temporal cortex about the contralateral superior visual field and the inferior visual field goes to the parietal via Baum's loop.
• superior colliculus

  orienting the movements of head and eyes
• Pretectum

  reflex control of pupil and lens
• Hypothalamus in function of vision

  Circadian rhythm
• What does the pupillary light reflex tell us?

  It says if light is shined on one eye and constricts the other eye's pupil should constrict too.
• pupillary light reflex

  protective response of pupil constriction when a bright light is flashed in the eye.

  Ganglion cells-->pretectum--->Edinger-Westphal nucleus-->ciliary ganglion
• Thalamus involved in vision?

  Lateral Geniculate Nucleus (LGN)
• Tritanopia

  lack of functioning blue cones-VERY RARE
• Deuteranopia

  lack of functioning green cones
• Protanopia

  lack of functioning red cones
• What are the colors in wavelength presented by cones?

  Long- red

  Medium-Green

  Short- blue
• What are cones?

  provide vision in bright light, color vision, sharp images

  Low sensitivity to light, and high spatial resolution
• What are rods?

  retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.

  They are extremely sensitive to light and have low spatial resolution
• How do photoreceptors hyperpolarize in the light?


  Light breaks down rhodopsin, then activates the G protein(Transducsin) which then activates the cGMP enzyme. Which breaks down CGMP to GMP, in return closes the gated gates.
• How do photoreceptors depolarize in the dark?


  When dark photoreceptors depolarized and Cgmp gated channels open, letting in potassium and calcium.
• Where is amacrine cells located?


  Between bipolar cells and ganglionic cells
• What does horizontal cells do?

  Horizontal cells when depolarized by glutamate, they release GABA, an inhibitory transmitter to inhibit the photoreceptors
• Where is horizontal cells located?

  Specialized retinal cells that contact both the photoreceptor cells and the bipolar cells
• What receptors do "OFF" bipolar cells have?

  AMPA/KAINATE, which is naturally excitatory.
• What receptors do "ON" bipolar cells have?

  Mglur6, which is naturally inhibitory
• What neurotransmitter is released by photoreceptors and bipolar cells?

  Glutamate
• When it is bright what happens to photoreceptors?

  Hyperpolarization
• When it is dark what happens to photoreceptors?

  Depolarization