Vision

Question 1

Where is the ganglion for vision located?

Answer 1

Primary Neuron (Ganglion Cell), lies wihtin the retina

Question 2

Visual Pathways: Superior Colliculus (Pretectal Nucleus)

Answer 2

• Reaction to visual stimuli without creating a perception of vision
• To Facial Motor Nucleus – Blink to threat response
• To Visceral Oculomotor Nucleus – Pupillary response (Shine in one eye and dilation in both)

Question 3

Visual Pathways: Lateral Geniculate Nucleus

Posterior portion of the thalamus

Answer 3

• Perception of vision
• To Primary Visual Cortex via the Geniculocalcarine Tract (near occipital lobe)

Question 4

Important principles of the Geniculocalcarine Tract

Answer 4

• Lens Optics
  – Image information projects onto the retina is upside down and backwards
  – Orientation doe snot change as the image information passes through the neural pathways
• Visual Field is divided into left and right halves in both eyes
  – Information from each visual field is kept seperate as it is sent to the visual cortex

Lens Optics - Retina Inverted Image

Question 5

Optic Pathway (Visual Perception)

Answer 5

• Optic Nerves pass through the skull through the optic canal of the sphenoid bone
• Two nerves merge as the optic chiasm
  – Partial decussation of information from the two visual fields of each eye seperate (½ stays, ½ crosses over)
• Neural Pathways leaving chiasm become known as optic tracts (each convey a single visual field)
• Optic tracts pass into thalamus and synapse within the Lateral Geniculate Nucleus
  – Axons leave nucleus as optic radiations (4)
• Optic radiations convey information to the visual cortex in the occipital lobe

Question 6

What could this be caused by?

Answer 6

Damage to the Right Optic Nerve: Right Eye Blindness

Question 7

What could this be caused by?

Answer 7

• Damage to the Right Optic Tract: Left Homonymous Hemianopsia (lose one visual field)
  OR
• Damage to the Right Optic Radiation: Left Homonymous Hemianopsia (All radiations taken out on one side)

Question 8

What could this be caused by?

Answer 8

• Damage to the Optic Chiasm: Bitemporal Hemianopsia
• Outer portions of the visual fields taken out giving you tunnel vision

Question 9

What could this be caused by?

Answer 9

• Damage to the Meyer’s Loop of the Right Optic Radiation: Left Homonymous Superior Quadrantanopsia
• Only one optic radiation taken out

Question 10

What could cause this?

Answer 10

• Damage to the Left Optic Radiation
• Only one optic radiation taken out

Question 11

Explain what possible visual impairments could be seen at different letters

Answer 11

Question 12

Interpretation to Perception of visual information

Answer 12

• The first step is visual signal processing in the Visual Cortex (Area 17)
• Perception involves Primary Visual Association Cortex (Areas 18 & 19)
• The Retina can be mapped roughly to the Association Cortex, with a lot of overlap. (This overlap likely explains the “cover up” of the physiological blind spot. (Brain fills things in))

Question 13

Perception: What? or Where?

Answer 13

• Where – Medial Part of Cortex (Dorsal stream) interprets location of features in the environment, also called “vision for action” – parietal, motor and frontal lobes
  – 3D space and action
  – Motor control stuff
• What – Lateral Part of the Cortex (Ventral stream) interprets the identity of things within the visual field – temporal lobe
  – What objects are, object recognition, facial recognition
  – Description, identification

Question 14

Posterior Parietal Cortex and Vision

Answer 14

• Adds contextual meaning to vision
• Plays a role in coordination of 3-D visual perception (again, think utility for action)

Question 15

Coordination and Vision

Answer 15

• Motor Association Cortex
• Basis for visually guided motions

Question 16

Dorsolateral prefrontal cortex and vision

Answer 16

Grasping and pointing function

Question 17

Occipitotemporal cortex and Ventral Visual Pathway

Answer 17

• Helps to interpret shapes
• Helps to identify generic faces
• Helps to recognize colors

Question 18

Inferiotemoral cortex and vision

Answer 18

Provide memory context to the interpretation of faces and shapes.

Question 19

What and Where Pathway - Interactions

Answer 19

These streams work together but we simplify it to be able to understand. Very complex.