The Visual System

Part I: Identify the parts of the nervous system that are active in the Visual System

The Visual System: OverviewEyes register optical information

Eyes send this information via the Thalamus to Primary Cortex V1 (Occipital Cortex)

The brain begins to process the signals into vision

The signals are then sent on to other brain regions via Two pathways from V1 “What” pathway to Temporal Visual Cortex called Ventral Pathway “Where” pathway to Parietal Cortex called Dorsal Pathway

Convergence on Frontal Cortex

Human Visual Brain: positions of V1 – V5 areas1. V1 and V2 are involved in basic

visual features

2. V3 and MT/V5 are involved in 1. Motion detection2. Spatial localization3. Hand and eye movements

3. V3/Vp is involved in shape perception

4. V4 is involved in color vision

Anatomy of Pathway to Visual Cortex

Human Brain: From Eyes to Visual CortexThe last layer of cells in the retina is known as the Retinal Ganglion cells or just Ganglion cells.

They come in two varieties:

1. Parvocellular (P) cells carry information about colour

2. Magnocellular (M) cells carry information about movements and flicker

From Eye to Striate CortexThe outputs of different ganglion cells in each eye project

1. to specific layers of the LGNs (C = contralateral, I = ipsilateral)

2. Then to striate cortex (V1)

3. Then to discrete stripes of V2

4. Then to areas V3 – V5

The Parietal Cortex: Pathway InputsThe Parietal Cortex receives input from two pathways:

1. The Superior Colliculus (SC) route

1. Not all the Ganglion cell axons lead to the LGN, some head off to the SC and Pulvinar route

2. LGN/V1 route and the Dorsal Pathway

Mapping of the Retinal image in the Striate Cortex

Mapping of the Retinal image in the Striate CortexNORMAL IMAGE

INVERTED IMAGE

(JUST FOR VISUALIZATION)

Part II: Describe the functions of the nervous system that are apparent and/or impaired in the Visual System

Blindness

Both eye and brain are required for functional vision

Two kinds of blindness:Normal blindness (eye dysfunction)Cortical blindness (brain dysfunction)

“What”/”Where” Pathway

What/Where PathwaysEvidence from NeuropsychologyVisual agnosia:

Inability to identify objects and/or people

Caused by damage to inferior (lower) temporal lobe

Disruption of the “what” pathway

Visual neglect:Inability to see objects in the

left visual field Caused by damage to right

parietal lobeDisruption of the “where”

pathway

Damage to the Parietal lobe(the Dorsal Pathway)

Damage to the Parietal lobe leaves only the ventral route intact and would be responsible for the optic ataxia (Balint-Holmes syndrome)

Damage to the Inferotemporal lobe (The Ventral Pathway)

Damage to the Inferotemporal lobe leaves only the Dorsal route intact and maybe responsible for Visual form of Agnosia

Primary Visual Cortex V1 DamageDamage to the Primary Visual Cortex V1, so information cannot reach the Ventral Pathway at all, but the Dorsal Pathway can be stimulated via information through the Superior Colliculus and Pulvinar

Part III: Ways in which Neurobiology has allowed me to analyze the events and phenomena around me

Topics that I was taken from this class that I will be using in my research on Artificial IntelligenceUnderstanding the components of all perceptual pathways: Transduction, Transmission and Modulation are the keys for the comprehension of our Perception of the world

Optical illusions show that What we see, it is not the reality of the world. What we see , it is only an interpretation of the reality, based on our past experiences which are saved in our memories,

The different type of brain’s memories are the elements that provide us with our identity of who we are

The Neurobiology of Consciousness is the most important question in our lives. We learned the basic concepts of Neurobiology in this class which it is the first step in getting into the world of consciousness

It has been important that I understood the following concepts of anatomy:

Anatomy of the Senses Anatomy of Emotion Anatomy of Attention Anatomy of Memory Anatomy of Language Anatomy of Object Recognition Anatomy of Consciousness

AnatomyANATOMY OF THE ATTENTION ANATOMY OF THE SENSES

AnatomyANATOMY OF MEMORY ANATOMY OF EMOTION

AnatomyANATOMY OF LANGUAGE ANATOMY OF CONSCIOUSNESS

Anatomy of object Recognition

References1. Principles of Neural Science, 5th ed, E. Kandel, 2013

2. Neuroscience, 5th ed, D. Purves, 2013

3. Neuroanatomy, 2nd ed, H. Blumenfeld, 2010

4. Vision and Brain, J. Stone, 2012

5. The Brain Book, R. Carter, 2009

6. Understanding Vision, L. Zhaoping, 2014

7. Vision, D. Marr, 1982

8. Neurophysiology, R. Carpenter and B. Reddi, 5th ed, 2012

9. Medical Neurobiology, P. Mason, 2011

10. Fundamental Neuroscience, 4th ed, D.Haines, 2013

11. Mapping the Mind, 2nd ed, R. Carter, 2010

12. Visual Perception, 3rd, ed, N. Wade, M. Swanston, 2013