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Lecture 1

BIO SCI N110 Lecture Notes - Lecture 1: Illusory Contours, Neuroglia, Retina

Biological Sciences
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Weds 4.24.19 | Introduction to the Sensory Systems
The Challenge of Understanding the Sensory Systems
The brain is the most complicated and sophisticated organ created by evolution
~100 billion neurons
Each neuron is connected directly to ~7,000 other neurons (~100-500 trillion synapses)
Even more glial cells (~500 billions to ~ 1 trillion)
Each neuron is also covered by thousands of receptors that respond to neurotransmitters,
neuromodulators, hormones, …
We will focus mostly on the visual system -- we know the most about the visual system
What our sensory systems do is incredibly hard
The sensory information we get is ambiguous
Different lines in the world, same projection on the retina
Somehow you can drive in a snowstorm … but it's really hard to train a computer to do it
Your brain actively constructs your sensory experience
Your visual system is not like a camera faithfully capturing images
The information you receive is actually very vague = your brain constructs what you see
Everything you see is actively constructed
Color, shading, texture, motion, shape, …
This "internal model of the world" is built by innate rules combined with your own experiences
including your memories, emotions, logic and beliefs
Internal rules, assumptions, and shortcuts influencing sensory perception
Why do we have these rules?
Our brain has evolved for a very different world than the one we live in now
Our ancestors lived in a very dangerous world, and had to make quick decisions to survive
We evolved innate rules, assumptions and shortcuts to help us quickly decide in a hostile
Subjective perception of "Objective" External Stimuli
Perception is an opinion
Background/foreground effects -- woman on horse
Illusory contours -- you see a line but there is no line
your brain creates the contours of objects
It works with curved lines too
Simultaneous contrasts-- the circle looks brighter/darker compared to the background color
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