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The Mind's Past

by Michael Gazzaniga

University of California Press, 1998. Available in hardback at amazon.com


that is full of clever special devices that allow it to reproduce, navigate.., detect...predators, and perform a multitude of tasks.

Then imagine the Thing with a new feature. It asks "how".

The Thing is our brain. It asks "How do I work"? I seem like a bag of tricks. "How am I integrated."

In common parlance, the Thing asks: "What and Who am I."

A genetic blueprint is in control. It builds brains.

Neurons migrate to their sites. The manipulation of one gene during development can disrupt one layer of cells in one area of the brain.

Then the Brain expresses what it knows, and it comes loaded...

with "devises". If we accept as fact that there is no unified neural network...the task of understanding conscious experience is not hopeless.

Let's accept the premise that each devise solves a problem.

Everything from perceptural phenomena to intuitive physics to social exchange rules comes with the brain.

These things are innately structured.

There is a gap between our understanding of the brain and the sensation of our conscious lives.

By the time we know about an action the devices have already [begun to] performed it.

How, then, does the brain enable conscious experience?

The brain is not a general-purpose computing device; it is a collection of circuits devoted to specific capacities.

[By "conscious experience" Gazzaniga means our awareness of our capacities, not the capacities themselves.]

We must distinguish our myriad capacities from our feelings about those capacities.

A circuit-perhaps a single system or one duplicated over and over again- is associated with each brain capacity. The more systems a brain possesses, the greater its awareness of capacities.

The left hemisphere has many more mental capacities than the right. The right hemisphere's level of [self?] awareness is limited.

Circuits arise from natural selection. The brain is not a unified neural network that supports general problem solving. If we accept this realization as fact, we can concentrate on the possibility that smaller, more manageable circuits create awaren

Spit-brain research also exposed the existence of the left brain's INTERPRETER, whose function is to interprete our behavior and our responses.

The next step is to find the common and perhaps simple neural circuit(s) that allows vertebrates to be aware of their species-specific capacities.

The enabling circuit(s) in the rat is most likely present in the human brain.

Each species is aware of its capacities. Human consciousness is different in degree, not kind.

The Interpreter delivers all kinds of...productive answers to questions of how things relate to one another.

It gives birth to the concept of the self.

The device that has rules for solving a problem of how one thing relates to another must be reinforced for such an actions, just as an ant's solving where the daily meal is reinforces its food-seeking devices.

Answering the device's question: "Who is performing this action" with "I am!", provides such reinforcement.

The conceptual self grows and grows and reaches proportions where the biological fact makes an impact on our consciousness but doesn't paralyze us.

The Intepreter is the most amazing thing human beings possess: it keeps convincing us we are good, and that we are in control.

We subconsciously sense the future.

[A fundamental clue to the role of "self" as "that which adjusts to the future" is on p. 171, where Gazzaniga says "we are adjusting, perhaps, the possibilities being served up, but the brain processes outside of our awareness are doing the serving."]

For example, what we see is not what is on the retina at any given instant, but a prediction of what will be there.

Some system in the brain takes old facts and makes predictions as if our perceptual system were really a virtual and continuous movie in our mind. p. 75

Another example is the phenomenon of blindsight.

The information presented in the neglected field can be used to make decision, even though it can't be consciously described. p.78

Sir Francis Crick (the co-discoverer of DNA) and Cristof Koch of Cal Tech, have a program aimed at determining which parts of the brain are involved with conscious experience and which are not. p.97

Sensors, our eyes, for example, send signals to the brain.

Our "Attentional Brain System" for vision is a "devise" located in the parietal lobe that enables us to perceive the world in a way that permits us to maximize our survival. p.83

This attentional system selects objects in our view for special attention. Our brain is built in order to see certain things.

For example, when did you last spontaneously look upward? We rarely do. That's why, in guerrilla warfare, the safest place to hide is above, in a tree.

Through evolution we have tuned our attentional system to be more sensitive to objects in our lower visual field.

In fact, there are more connections to the parietal lobe from the part of the visual brain that represents the lower visual field. Recall that the parietal lobe manages spatial attention.

Illusions illustrate the limits of our attentional devises.

For example, the visual system is limited in its ability to resolve whether two events at different times are indeed two different events.

The temporal sensory system [works] if the visual system can detect a light flickering at fifty hertz. But it cannot tell if the light went on and off when it flickers faster than four to six hertz. The movie industry depends on this limitation.

Chapter 5: "The Shadow Knows"

Who isn't thrilled by seeing an osprey swoop down and majestically catch a fish in a river?

Even though the osprey has not been taught Snell's law of reflected light, it knows that the fish is actually behind where it appears to be.

The osprey must estimate not only its own velocity, but also the position and velocity of its prey.

Special devices [ enabling automatic processes] abound in nature, and they perform miraculous feats. Even though our sense of purpose and centrality of will are foremost, there dwells within us an automatic system.

The elephant's trunk has about fifty thousand different muscles, each with its own innervation. When an elephant spots a peanut in your hand, how does it orchestrate those muscles into a swift and perfect movement?

Melvin Goodale...wondered if the brain is organized in one way to perceive illusions and in another to respond to illusions.

Studies how people reach for items that appear larger or smaller than they really are.

Visual information comes into our first and primary cortical zone, the occipital cortex.

Then it goes in one of two directions: the dorsal stream heads up toward the parietal lobe. The ventral stream projects into the temporal lobe. Information can be routed to one stream or both.

Patients with lesions in the dorsal stream...that damage the parietal lobe connections have little trouble seeing, but a lot of trouble reaching for objects... It is as though they cannot use the spatial information they see.

Patients with lesions in the temporal lobe...that affect the ventral stream, can see an object but not identify it. But they can reach for it accurately.

The temporal lobes process object-centered information such as shape, color, and size. From the viewer's standpoint, the object is constantly changing its position in space. Something has to keep track ... There has to be a place for the viewer.

The parietal lobe is taking the sensory-percept and organizing the body's response to it.

Each neuron has a receptive field. Stare at an object on a wall, within the visual field of the neuron. The field is about 5 inches square inches. The neuron fires rapidly within that zone. It stops when the object is outside the zone.

Platt and Glimcher's experiment with monkeys uses this property of neurons to explore how much information they encode.

Neurons encode information about their past behavior, and the size of reward if it makes the correct movements.

The parietal lobe is showned here to be crucial, participating in what goes into the decision to act.

A lot of its work apparently happens before there is even a hint that the animal is deciding what to do. The automatic brain is at work again.\

How many neurons need to participate in a decision. About a hundred. (Michael Shadlen, University of Washington)

Emotions: Almost everything we see, do, and hear evokes a salience within that reflects subtle but continual conditioning, which proceeds outside the realm of awareness.

Antonio and Hanna Damasio illuminate how emotions interact with cognition automatically and outside of awareness.

Our viscera signal our brain about which ideas we should use in any given situation.

Decisions require interactions with our past. That history has an emotional component shaped by success or failure in what we did or what occurred.

Their Card Game described on p.119:

Subjects' galvanic skin response (GSR) rose when picking cards from the "right" deck before the subjects could explain why they were picking cards from those decks.

But patients with lesions in their prefrontal lobes did not have this GSR cuing response. The Demasios' believe the lesion interrupts the pathways for critical information arising in the gut to be communicated to the decision processes in the brain.

A French doctor, Jean-Christophe Marchand, visiting at Yale, recently walked into Dr. Gazzaniga's office wanting to talk about Immanuel Kant's brain lesion.

Kant's early work, written before age 47, was clear and readable. Work written after that date is nearly impossible to read.

Kant began complaining of headaches and gradually lost vision in his left eye. His great philosophical works, which were written after age 47, and in a style nearly impossible to read, emphasize the idea that innate cognitive structures exist indepen

Dr. Marchand deduced that Kant has a left prefrontal lobe tumor, growing slowly, but there. Damage to this area affects language ability and the ability of our emotional system to cue us toward good cognitive strategies.

Chapter 6. "Real Memories, Phony Memories"

Memories are somehow stored in a network, not in a specific region of the brain. But how can we define "network specificity"?

We don't remember what we don't pay attention to: The Undergraduate Experiment

Two undergraduates are talking on a lawn. The first is unaware that the second is a stooge for the person conducting the experiment. A workman carrying a large door walks between them. At that moment a second stooge replaces the first.

The unsuspecting students never notices the switch!

Split-brain phenomenon: Treating epilsepsy by severing the connection between the two hemispheres localizes the seizures to one hemisphere. Gazzaniga has studied split-brain patients extensively.

In a split-brain patients the thoughts and perceptions of one hemisphere go on outside the awareness of the other.

The left hemisphere is adept at problem solving and thinking. The capacity for speech is also located in the left brain.

The right hemisphere is better at things such as facial recognition.

The right hemisphere can be instructed to do something or to react to an emotion and the right hemisphere will respond to the specific command we give.

The left brain could not tell about the command given to the right brain, but didn't seem to mind.

Then Gazzaniga got the idea of asking the left hemisphere how it felt about the right brain occasionally doing something outside the left brain's control.

Pursing this idea, Gazzaniga discovered that the left brain has a specialized mechanism that interprets actions and feelings generated by systems located throughout the brain. He calls this the Interpreter.

Example: You command the right brain of a split-brain patient to take a walk. The patient gets up and starts walking. You ask the patient why he is doing that. The patient [confabulates]: Oh, I need to get a drink."

Psychiatrists work to reverse the old stories the Interpreter has created as part of our personal narrative.

Neurologic example of the Interpreter at work: Split-brain patients with parietal lesions who are blind on the left side frequently claim the left half of their body is not theirs! They see their left hand, for example, but maintain it's not theirs.

The parietal cortex is where the brain represents how an arm is functioning. It monitors its position in space, its existence in relation to everything else. If there is a lesion to the sensory nerves that bring the brain information, the parietal c

The Interpreter remembers the gist of the story line and fills in the details by using logic, not real memories.

Chapter 7: "The Value of Interpreting the Past"

The left brain can go beyond the information at hand to draw conclusions. The right brain cannot. PET scans show that it's the left brain that is active during reasoning, even reasoning about spatial relations.

The left brain is always looking for order and reason, even when they don't exist. The Interpreter is always trying to make predictions. It fails when trying to interpret giant data sets or meaningless data sets.

Logic tests show that humans are "probability blind". The laws of probability aren't intuitive for us. Our decisions can't be understand solely according to the rules of Game Theory.

Often our rule of thumb heuristics come into play when we're confronted with a problem.

If 72 families have children in this order: gbgbbg, how many would you expect to have in this order: bgbbb?

The answer is 72 famililies. But most people think you're asking about a squence of births, not about the pattern as a whole, so the 50/50 rules is chosen and people pick some number less than 72 because they think the first pattern is more likely.The whole purpose of our brain is to make decisions...

Rationality tests are too artificial to really plumb our intelligence.

Imagine a Thing.....


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