Consciousness: How Our Brains Turn Matter Into Meaning

1. What is Consciousness?

• Aristotle believed that consciousness exists as a continuum of different types of souls:
  • Plants have a vegetative or nutritive soul, which controls their growth, nutrition and reproduction.
  • Animals have, in addition, a sensitive soul, which allows them to perceive things and move about, and they also have fears and desires.
  • Humans have, in addition, a rational soul that allows them to reason and reflect.
• Locke and Hume came up with a properly materialist view of consciousness, but their explanations did not explain how each individual mind feels like a unified, individual phenomenon, rather than just a mass of unconnected experiences (binding problem)
• Chalmers sees the hard problem of consciousness as explaining this subjective sense we have as individuals of being us, with all that implies in terms of our specific responses to, say, a sunset or a work of art, the particular way we felt when we first fell in love or any personal experience, in purely material terms.

2. Tools and Symbols

• Parrington argues that human self-conscious awareness arose as a consequence of two other unique human attributes - our capacity for language and our ability to continually transform the world around us by designing and using tools.
• Engels, in 1876, proposed that humans first began to diverge significantly from other primates when our ancestors started walking on two legs. This freed the hands for using and designing tools in a systematic way to transform the world around them. Importantly, such design and subsequent use of different types of tools was carried out with other proto-humans in a socially cooperative manner. Because of the need to communicate with their neighbors about how to carry out such innovative actions, our ancestors also began to develop the first forms of language. Subsequently the development of both systematic tool design and use, and language, led to a dramatic growth and restructuring of the brain.
• Practically all of our interactions with the world are through tools that we have created.
• Human language, is an interconnected system of abstract symbols, linked together by grammar in such a way that it can convey complex meaning. It is for this reason that only human beings are able to use language to convey complex ideas like past, present, and future, individual versus society, location in space, and even more abstract concepts.
• We can see tool use and language as activities that do not just guide our interactions with the external world, but also act as "mental tools" that have transformed the brain in the process.
• Vygotsky argued that egocentric speech - children's tendency to talk to themselves as they play - is the first stage in a child starting to organize their actions using words and that while this form of speech seems to disappear, what is actually happening is it becomes internalized as "inner speech", which in adults plays a central role in the organization and development of our thoughts.
• Inner speech differs from outer speech in some important ways. It is likely to be much more rapid, and far more fluid in meaning, than the speech we use in conversation with others. There are also probably different types of inner speech, ranging from that which emerges from our innermost, half-formed thoughts to the type that structures our outer speech when we express ourselves to others.

3. Nerves and Brains

• Neurons contain:
  • A cell body
  • Dendrites - Tendrils that receive incoming signals from other neurons
  • An axon - A long protuberance that conveys signals to the next neuron in the circuit
• When a neuron is stimulated through its dendrites, this triggers an electrical impulse called an "action potential", which races along the axon at speeds that can reach around 200mph in the fastest human neurons. The speed at which impulses can travel along an axon are greatly enhanced by a structure called a "myelin sheath". This is a fatty layer that both protects the axon but also allows the neural signal to jump between gaps in the sheath in a process called "saltatory conduction". At the end of the axon, the electrical impulse is transmitted to a dendrite on the next neuron in the circuit, at a gap between neurons called a "synapse". The action potential does this by stimulating the release of a chemical called a "neurotransmitter" into the synaptic gap. The neurotransmitter diffuses across the gap and, at the other side, it acts like a key in a lock to trigger a cellular response that activates a new action potential in the target neuron.
• The human brain is estimated to contain around 86bn neurons, linked by 100tn connections.
• Neurons make up half the brain. The rest is made up of glial cells including oligodendrocytes, astrocytes, and microglia.

4. Evolving Minds

• Jellyfish are a simple type of large multicellular organism whose nervous system consists of:
  • Sensory neurons - Which pick up signals from the environment.
  • Motor neurons - Which trigger a response in the organism
  • Interneurons - Which coordinate these two activities in the central nervous system (CNS).
• The human brain has three main parts:
  • The forebrain - Includes:
    • The Cerebellum - which has two hemispheres and a highly folded surface cortex
    • The Cortex - Is particularly developed in humans, twice the expected area for a primate of our size
      • Broca's area - For producing words
      • Wernicke's area - For understanding words
      • Sensory and motor maps, with most space taken up by nerves going from and to the lips, tongue and pharynx and to and from the hands and digits.
    • The Limbic System - emotional or lizard brain
      • Thalamus - Central postal-sorting depot channeling information into and out of the cortex
      • Hypothalamus - Underneath the thalamus, regulates thirst, hunger, desire, reproduction, and the body clock
      • Amygdala - Plays a central role in processing emotions, being involved in generating fearful, but also pleasurable sensations
      • Hippocampus - Plays important roles in memory
  • The midbrain - alos involved in processes such as vision, hearing, and movement
  • The hindrain - Includes
    • The Pons, which controls sleep
    • The medulla, which regulates vital functions such as breathing and heart rate
    • The cerebellum (little brain) - With, once again, two hemispheres and a highly folded surface. Involved in regulating and coordinating movement, posture, and balance and also in creativity and imagination.

5. Thought and Reason

• The combination of an almost unlimited vocabulary and an instinct for correct grammar is what provides human beings with the ability to communicate with other humans in a precise fashion and with a creativity that, while often only used in everyday, mundane circumstances, can allow some humans to reach dizzy heights of novel artistic or scientific expression.
• Spoken words, music, visual art, literature and film - all of these symbolic forms might be part of the thought process.
• Because our thoughts are so infused with the conceptual framework that language provides, it is almost impossible for us to imagine how it might feel to not have such a framework. Therefore, as a species, when we distinguish different colors or recognize that something happened in the past, as opposed to something that might happen in the future, or that we are an individual person and therefore distinct from other people, it can be easy to assume that other species have similar feelings.
• Inner speech and other inner symbols act like a transmission belt between thought and outward expression. However, that does not mean that human thought and speech are equivalent, since all our thoughts arise from a biological brain that has much in common with other species' brains.

6. The Sensual World

• All species on Earth, from unicellular bacteria to complex multicellular organisms like ourselves, have evolved ways to detect changes in the environment and respond accordingly, such activity being crucial to their survival. Demonstrating the unity of life on our planet, it is remarkable how similar, at least at the level of molecular biology, mechanisms of sensing the environment are between species. Such unity can be demonstrated by comparing the sense of a bacterium and a human.
• While one part of the visual cortex receives signals relating to an object's shape, another area receives ones about its color and another about whether the object is moving.
• Kittens kept in enclosures painted with only vertical lines never learned to see horizontal ones, for instance, a chair seat, while kittens only exposed to horizontal lines could not make out vertical ones, and would therefore bump into a chair leg.
• Human infants from about 8-10 months of age generally begin to notice the presence of snakes and spiders, avoid heights at the edge of a drop-off and withdraw at a stranger's approach.
• But there seems to be no evidence that human infants' responses to spiders, snakes, drops and strangers are either universal or primarily fearful. Instead, the responses were shown to be highly variable, driven initially primarily by curiosity rather than fear, and were very dependent on the context in which infants encounter such stimuli, for instance, fearful reactions by parents or carers. The extraordinary curiosity that human infants show in their encounters encourages them to explore new things, while maintaining the flexibility to develop a fear if they discover something truly threatening.
• The developing human brain is far more primed to respond to new experiences that the brains of other species, which undoubtedly affects our perception of the world around us.
• Human language provides a means for the expression of abstract concepts such as time and place, self vs other and so on, and through the medium of inner speech this brings abstraction into our inner thoughts. However, such an ability to think in abstract terms also affects the way we perceive the world.
• At the heart of conceptual thinking is the ability to group things hierarchically. In terms of color, this means humans have an overall concept of color, with the individual colors subordinate to this. Similarly, we have an overall concept of shape and subordinate to this are specific shapes, for instance, circles, squares, triangles and so on.
• Language is central to conceptual thinking because it allows us to describe concepts such as colors and shapes, and also to employ even more general terms, such as "characteristics" or "properties".
• Drawing does not require words, although language can accompany it, but it does require an ability to abstract. Such abstraction is shown by the fact that we can recognize a series of crudely drawn lines as a person as equally as we do a finely drawn, or photographic image. This is important in terms of perception because it means we also perceive the world as an abstraction. That such a capacity is a uniquely human ability is shown be the failure of attempts to teach apes representational drawing.

7. Learning and Memory

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8. Mind Chemistry

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9. Philosophy of Mind

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10. Individual and Society

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11. Information and Meaning

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12. Chance and Design

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13. Structure and Function

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14. Circuits and Waves

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15. Free Will and Selfhood

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16. Consciousness and the Unconscious

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17. Modernity and Its Contradictions

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18. Sanity and Madness

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19. How Ideas Change

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20. Future of Mind

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