Reading 1: Intro to Nervous System

Question 1

Brains aren’t Minds

Answer 1

• The subjective experiences of our minds emerge not from what the brain is but from what it does.
• The brain acquires, encodes, transforms, stores, retrieves and uses information. It is an information-processing organ.
• Nervous system = information-processing organ system.
• Therefore, to understand the mind we must first understand the brain and to understand the brain, we must understand information processing.

Question 2

Neuroanatomy

Answer 2

• Anatomy is the most important thing about the brain.
• Cerebral cortex contains approx 10 billion neurons and 1 billion synapes.
• If we consider all the possible connections that can be made = 10 followed by at least a million zeroes.
• There are 10 followed by 79 zeroes particles in the known universe.

Question 3

Computational Theory of Mind

Answer 3

The mind results from information processing of the brain.
* The mind is the computations carried out by the brain.

Question 4

How is your brain different from modern computational devices (laptop,phone…)

Answer 4

1. Compared to a modern computer, your brain is slow. Brain neurons fire at most a few hundred impulses per second. These impulses travel down axons at a speed of 1-100 m/s.
2. Brain does not run on programs. Brain can do enormous range of different things - better than a computer and things that a computer cannot do.
   
   • Its sofware is built into the physiological properties of 100 billion neurons and synapses that connect them together.

Question 5

Power of the brain

Answer 5

• Comes from its ability to distribute information processing over an enormous hierarchical network of processing modules.
• Different regions and subregions of the brain are specialized for different functions because of the distinct physiology and connectivity of their neurons.
• Complex functions (ie. decision making, cognition) all emerge from the way these specialized regions are connected into larger networks.

Question 6

How do we understand/study the brain??

Answer 6

Where to we start?? There are many ways of thinking aboput this problem:
1. Reductionism
2. Computational Neuroscience

Question 7

Reductionism

Answer 7

• To understand something complicated, we take it apart and look at its pieces. Then once we understand the pieces, we put them back together to understand the whole system.
• Weakness of this approach - complex properties of the whole may not be evident from the properties of the pieces.

Question 8

Stretch Reflex

Answer 8

• by Sherrington
• Stretching a muscle activates a loop between sensory neurons embedded in the muscle and motor neurons in the spinal cord that causes the stretched muscle to contract and its antagonist muscle to relax.
• Sherrington suggested that these reflexes were the basic building blocks of movements (incorrect).

Question 9

Computational Neuroscience

Answer 9

• By Marr
  Think of the problem in 3 ways:
  1. Computational Theory: What is the goal of the computation, why is it appropriate and what is the logoic of the strategy by which it it can be carried out?
  2. Representation and Algorithm: How can this computational theory be implemented? In particular, what is the representation for the input and output and what is the algorithm for the transformation?
  3. Hardware and Implementation: How can the representation and algorithm be realized physically?

Question 10

What do the levels of Marr’s framework mean in the context of the brain?

Answer 10

1. Hardware Implementation: the brain is made of something, the mind is not made of anything. Its computations that make the mind, not the stuff the brain is made of.
2. Computational Theory: to understand any computational system, you have to understand what it is trying to accomplish. You cannot just understand the individual parts (like reductionism suggests).
3. Representation and Algorithm: The brain does not just encode information, it also transforms it. The information contained in the inputs to a neuron or a brain region are transformed to produce different outputs.

Question 11

What is the computational goal of the brain?

Answer 11

Use sensory data and stored knowledge of the structure of the world to produce motor responses that yield the highest possible inclusive fitness for the organism.

Question 12

What are neuroscientist/ computational neuroscientist looking at?

Answer 12

We want to understand how the basic elements of the brain and nervous system are interconected in enormously complex computational network and how these connections enable the brain and nervious system to achieve their computational goals.