Transcript Introduction to Sensory Systems

‫ניורוביולוגיה ומדעי המח‬
‫ – מערכת הראייה‬2 ‫חלק‬
Introduction to Neurobiology
Part 2 – The Visual System
Shaul Hochstein
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
The retina
“From Neuron to Brain” Chapter 19: 379-405
Transduction and signaling in the retina
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
The retina
1- Structure of the eye
2- Muscles of the eye – fixation; convergence; accommodation;
3- Structure of the retina
4- The blind spot
5- Rods and Cones
6- Visual Pigments
7- Color vision: Young & Helmholtz
8- Photoreceptor sensitivity and signal amplification
9- Structure-Function relationships
10- Ribbon synapses
11- The fovea: Comparing central and peripheral vision
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
Is the eye like a camera?
Yes and No:
lens, focus, pupil, inverted image,
film=layer of photorceptors
But: information processing
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
To where are retinal signals transmitted?
Right sides of both retinas to right brain.
Left sides of both retinas to left brain.
BUT: image was inverted (up-down and
right-left) by optical pin-hole (lens) effect.
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
layers of neurons & connections in the retina.
Note 3 types of neurons at middle cell-body
layer.
The Retina and its layers
The Retina and its layers
Cell bodies
connections
Cell bodies
connections
Cell bodies
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
Rods and cones
- sensitivity vs. acuity & color;
- located in central vs. peripheral retina
- night vs. day
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
Pros and Cons for an inside-out retina.
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
Depolarizing and Hyperpolarizing receptor,
generator, and action potential signals
- still only one trick: change in conductance
to specific ion(s).
The photoreceptor response:
Receptor potential & generator potential
Graded potentials vs. Action potentials
In the dark, Na channels are open, causing depolarization and allowing Na
influx and K efflux, counteracted by pump. In light, Rhodopsin ultimately
closes these channels stopping the flow.
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
The source of color vision:
How many cone types do we need?
1 type: no color (confuse color and intensity)
2 types: full color spectrum but no combinations
3 types: color spectrum plus white (& other
unsaturated colors) plus purple (red & blue)
…
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
Transmission:
Photoreceptor to Bipolar
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
The receptive field
Definition – area in the world (or on retina)
where change in stimulus induces
change
in response in recorded neuron.
Extension – area in multi-dimensional
stimulus space where …
Physiological research – aids in guessing
Limulus
Mapping a receptive field
‫ניורוביולוגיה ומדעי המח‬
Introduction to Neurobiology
Introduction to Sensory Systems
A first computation:
Lateral Inhibition:
mechanism, consequences and function
Supplementary material