I want to welcome people to the course and I want to welcome people to the first series of lectures, which is on the brain, on neuroscience. And I want to begin this series of lectures and the course itself, with a story about a man named Phineas Gage, and an event that happened to Gage in the summer of in Cavendish, Vermont. So Gage was a blasting foreman working on a railway construction project and his job, at that time, was to clear away rock so that they could lay down tracks. And to do so, his routine during those days, was that he would bore a hole in the rocks. Inside the hole, he put blasting powder and a fuse in. Then he would cover that up with dirt and sand and take a tamping iron, which he carried with him.
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Dec 24, Anagh rated it it was amazing After reading Christof Kochs book, it was natural for me to pick up Cricks book on the same topic. Of his mentor, Koch had the following to say: They used to say that in his prime, Arnold Schwarzenegger had muscles in places where people didnt have places. Crick was to scientific creativity what Arnold was to body building. The astonishing hypothesis is a strong affirmation of the now long held belief that minds follow from brains.
On the other hand experimental data shows a breathtaking amount of brain activity that passes beneath the hood of conscious experience. How are the two different in terms of their neural correlates? The book is a feverish array of ideas and possible lines of attack. Crick tackles visual awareness as a starting point to explore the various facets of consciousness parrying philosophical conundrums right off the bat.
Crick presents several possible models for consciousness. Most famous of these is the Global Workspace GW model proposed by Bernie Baars which posits the existence of very short term memory. This memory acts like an attentional searchlight, throwing light on a subset of brain processes that are momentarily rendered conscious. The conscious process in its stead can broadcast a particular narrative of the world to other unconscious processes in order to perform a coherent voluntary function.
This is much like the workings of a modern democracy where competing groups lobbies vie for control of power. Powerful coalitions keep forming and dissolving, each stamping its will on the collective. Homo Sapiens, being a largely visually driven species, has a very intricate visual apparatus.
Broadly speaking, after the initial acquisition from the retina, information gets handled between layers of subsequent processing units. Its like a game of twenty questions, where each layer asks questions about the input until it arrives at a decision as to the state of the visual landscape.
These units are highly overlapping, with rich back connections. A map of the various visual hierarchies looks like a veritable zoo of connections and back connections. At the very top is the so called archicortex Hippocampus. The intervening layers are largely unexplored partly due to the messy ways in which evolutionary tinkering works.
Anyone who has ever trained a neural net would tell you that ascribing particular feature detection capabilities to specific neurons is erroneous as individual nodes often encode very complex representations. How this messy wiring laid down by evolution causes conscious percept is the million dollar question.
Much of our knowledge about the cortex derives from either invasive experiments on non-human primates or non-invasive experiments except for a few cases where electrodes may be directly implanted for diagnostic purposes with human subjects. The former approach allows for recording from single units whereas in human subjects researchers have to be content with signals received from potentially billions of neurons limiting spatial and temporal resolutions in the process.
While animals allow greater observational resolution, human subjects can provide linguistic feedback. Another source of information comes from studies on the pathological human brain. The book is a treasure trove of foundational albeit a tad dated experiments.
Crick is characteristically boisterous and pounds the reader with a feverish volley of ideas. Its almost as if he was thinking aloud in the process of writing the book.
The bibliography and glossary at the end are well written, making the book a good read for amateurs and professionals alike.
The astonishing hypothesis
Q: What is the soul? A: The soul is a living being without a body, having reason and free will. Roman Catholic catechism The Astonishing Hypothesis is that "You," your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. The interest of human beings in the nature of the world, and about their own natures in particular, is found in one form or another in all peoples and tribes, however primitive. It goes back to the earliest times from which we have written records and almost certainly from before that, to judge from the widespread occurrence of careful human burial. Without its spirit a body cannot function normally, if at all.
Astonishing Hypothesis: The Scientific Search for the Soul
The book then delves into a brief overview of many neuroscientific topics, ranging from a survey of how neurons function to a description of basic neural circuits and their artificial equivalents. Throughout, Crick cites various experiments which illustrate the narrow points he is making about visual awareness, such as studies investigating the phenomenon of blindsight in macaques. The later chapters of the book try to synthesize many of the points made earlier about the visual system into a unified framework, although Crick frequently notes the many exceptions to his assumptions and the clumsiness of many of his attempts at synthesis. Background and response[ edit ] Crick had discussed the relationship between science and religion in his earlier book What Mad Pursuit. For example, the idea of a mechanism for the evolution of life by natural selection conflicts with some views on creation of life by divine intervention. Some, such as neurologist and Nobel Laureate Gerald Edelman believe that neural Darwinism is a more satisfactory explanation for the emergence of complex intelligence in humans.