Gerald Edelman - A theory of consciousness: The thalamus (50/86) скачать в хорошем качестве

Gerald Edelman - A theory of consciousness: The thalamus (50/86)

To listen to more of Gerald Edelman’s stories, go to the playlist:    • Gerald Edelman (Scientist)   Biologist Gerald Edelman (1929-2014) was born in America. His early work concentrated on the study of immunology and he was jointly awarded the Nobel Prize in Physiology or Medicine in 1972 for his work leading to the understanding of the antibody’s chemical structure. [Listeners: Ralph J Greenspan; date recorded: 2005] TRANSCRIPT: In 1978 or so, when I published this book The Mindful Brain with Vernon Mountcastle, I did discuss the issue of consciousness briefly. But it was only in 1987 and on, and particularly 1989, in a book called The Remembered Present, that I gave forth a theory of consciousness that was based on circuitry, dynamics, biology and, above all, evolution. And let me sort of outline that and then come back to this business of how a conscious artifact might relate to BBDs – brain based devices. The idea was something as follows: that yes, we could argue for ever about whether a table is conscious or a lizard is conscious or even a dog is conscious, but we sort of accept the idea that we are conscious, and we do that because we have a homology in our nervous systems and we also have a language for report and we can exchange back and forth and notice there are similarities in what philosophers call qualia – namely the experience of green, the experience of warmth, or the experience of a much broader experience. And so, starting there, the idea that I developed was as follows: that some time in evolution this process of re-entry became commanding. That at a time when reptiles were precursors to birds on one hand and mammals on the other, there was a huge expansion of particular circuits of the brain related to a structure called the thalamus and the thalamocortical circuits. So I have to tell you about that. The thalamus is something not much bigger than a circuit of your brain – not much bigger than the end of your thumb, which relays everything but smell to the cortex in a vast set of connections back and forth re-enterably. So there are corticothalamic and thalamocortical connections. And there are... there are also cortical... cortical connections which connect the cortices to each other that I mentioned before. And the idea here is that the so-called specific nuclei of the thalamus – the ones that handle smell and... excuse me, not smell... the ones that handle vision, hearing, touch, etc. – that these specific nuclei speak to the cortex but not to each other. But they're enveloped by another nucleus called the reticular nucleus which inhibits them and makes sort of dashboard changes, can pick which ones are more active than others. That particular set of circuits and specific nuclei expanded in both numbers and types at a certain point in evolution; I would figure about 250 million years ago... maybe 225 million years ago, I can't be exact with these numbers. And at that point it was possible to have a re-entrant connection between the more posterior parts of your brain that mediated the sensory elements like vision – I'll give you the example in a minute – to more forward parts of the brain that have to do with memory, that have to do with memory conditioned by the matter of values that I mentioned before. So value, category, memory and perceptual categorization were related by re-entry. That was the idea. What was the value of that idea? Well, it was that when you have a system like that, compared to an animal who doesn't, you have the capacity to make an enormous number of discriminations.