Presentation on theme: "Section 6 – The Brain Chapter 16: The neural correlates of consciousness Chapter 17: The unity of consciousness Chapter 18: Damaged brains All right, brain,"— Presentation transcript:
Section 6 – The Brain Chapter 16: The neural correlates of consciousness Chapter 17: The unity of consciousness Chapter 18: Damaged brains All right, brain, you don't like me, and I don't like you, but let's just get me through this, and I can get back to killing you with beer! Presenters: David & Mimi & Monica
Why Did the Chicken Cross the Road? Nietzsche: Because if you gaze too long across the road, the road gazes also across you. Jean-Paul Sartre: In order to act in good faith and be true to itself, the chicken found it necessary to cross the road Albert Einstein: Whether the chicken crossed the road or the road crossed the chicken depends upon your frame of reference. Darwin: It was the logical next step after coming down from the trees. Buddha: If you ask this question, you deny your own chicken- nature. Donald Hoffman: If we assume that the chicken is a conscious agent, then the road is an icon in the multimodal user interface. Cogito Ergo Sum Descartes
How can this gray, wrinkly physical lump of stuff in be the seat of consciousness? Chapter 16: The neural correlates of consciousness
One way to tackle this mind-baffling question is to look for neural correlates of consciousness (NCC). Correlations between neural events and conscious experiences DOES NOT imply causality. When a correlation between two events, A and B, is observed, there are 3 ways to interpret this phenomenon. 1. A might have caused B Neural events cause conscious experience 2. B might have caused A Conscious experience cause neural events 3. Third variable C gives rise to both A & B X factor cause conscious experience & neural events.
Let’s consider the “unconscious state”. Prior to surgery, a patient undergoes anesthesia, going from a conscious state to an unconscious state. What is biological mechanism behind this effect? Hans Flohr (German neuroscientist) observes that the normal functioning NMDA synapse is necessary for consciousness. Anesthetics abolish consciousness by interfering with the functioning of NMDA receptors. Conclusion: The NCC is the functioning NMDA synapses and the cell assemblies they support. But is it really that straightforward?
What is the “neural correlate” of conscious visual experiences vs. unconscious vision ? “So far we can locate no single region in which the neural activity corresponds exactly to the vivid picture of the world we see in front of our eyes”. Francis Crick
Are aspects of the visual system competing for consciousness? Binocular rivalry: different images are presented to the two eyes. First experiment were conducted on macaque monkeys. Procedure: Monkeys are shown different display to each eye, horizontal grating to one, vertical grating to the other. Result: Some cells in early visual cortex (V1) responds to vertical stripes, some responds to horizontal stripes. Their behavior did not change when the monkey's perception changed. But the behavior of these cells did change in the inferior temporal cortex (IT), to match what the monkey reported seeing. WHAT DOES THIS MEAN? THE NCC lies in IT? Can we really assume that monkey's consciousness = human consciousness?
Phantom Limb Phenomenon After losing an arm or leg, 90% of patients experience a “phantom limb”. Patients feel pain in their “phantom limbs” from time to time. Some report a touch on the face can sometimes felt as a touch on the phantom hand. What gives rise to this experience? The somatosensory cortex map of the body shows the sensory input of the face as being represented next to the hand. If the hand is missing, the sensory input of the face will start to invade the hand area. “The Little Man” What we would look like if our body parts are proportional to our sensory input.
Chapter 17: The unity of consciousness Why do we seem to have only one consciousness? Eccles dualism: The mind plays an active role in selecting, reading out and integrating neural activity, molding it into a unified whole according to its desire or interest. A far more constructive approach is to try to find out how the brain carries out the integrating and unifying functions. Or, reject the idea that consciousness really is unified at all. Perhaps, on closer inspection, we might find that the apparent unity is illusory. In this case, the task is to explain how we can possibly be so deluded.
The Binding Problem As the coin flips, what keeps the color,form, movements and other attributes of the coin together? In V1, there are many retinotopic maps. That is, the organization of cells reflects the layout of the retina. GWT relates consciousness to working memory. There is evidence that attention is required for binding. However, binding at attention are probably not the same thing because some things requiring binding are carried out unconsciously: catching the coin by way of the visuomotor system.
Binding by synchrony The thalamus controls attention by selecting the features to be bound together by synchronization of firing. (Crick) Andreas Engel, Wolf Singer, and colleagues say, Neurons forming part of one represented object fire together, and they fire out of synchrony with neurons representing other objects at the same time. Synchronization is necessary but not sufficient for consciousness. For consciousness, information must also enter short-term memory.
Unity as illusion Singleness of action is a vital requirement; if motor responses were not unified, an animal could quite literally tear itself apart! Some people reject the idea that consciousness is unified at all. Like Dennet's multiple drafts, by paying attention to some thing the appearance of a unified self having a unified experience is created. As soon as attention lapses, the unity falls apart and things carry on as normal.
Doh! what about multiple consciousnesses? The unification that comes with self-consciousness is an exception that is only possible through language. Semir Zeki (neuroscientist)
Think of how many people you have seen in your lifetime. Think of how many paintings you’ve seen. This is a vast amount of information, and you can easily discriminate between all these states. Consciousness is highly informative is it not? There are two types of consciousness (Edelman & Tononi). Primary consciousness: many animals have which allows for the construction of a scene, the maintenance of short-term memory and hence a “remembered present”. Higher order consciousness: emerged later in evolution, depends on reentrant connections between language and conceptual systems. Reentry and the Dynamic Core CONSCIOUSNESS OF CONSCIOUSNESS
Synesthesia : Superunity Synesthesia confounds the notion that conscious experiences are unified. To a person who possesses this ability, their senses of touch, sight, sound are enmeshed. Written letters or numbers are seen as colored, but people can hear shapes, see touches or even have colored orgasms (woah!).
Chapter 18 – Damaged Brains What is like to blind but believe that you can see? What is like to be paralyzed but convinced that you can move? What is like not to notice that you don’t don’t notice half of the world? What do you mean I have hemifield neglect?
Amnesia Korsakoff: most common form of amnesia, caused by the toxic effects of alcohol. Retrograde: a loss of long-term memory that stretches back into the past. Classical conditioning remains unimpaired and procedure learning remains intact. Are amnesiacs conscious?
Neglect Anosagnosia: patients are paralyzed but convince themselves that they can move. Anton’s syndrome: patients are blind but convince themselves that they can see. Hemifield neglect: occurs in right brain damage, so patients neglect their left visual field.
Blindsight Blindsight is a condition in which a person claims that he or she cannot see a certain area of their visual field, but when asked to make a guess, that person is right 90-95% of the time A person with blindsight could detect a slow or fast- moving stimuli, but was only aware of the fast ones.
Wisdom tells me I am nothing. Love tells me I am everything. And between the two, my life flows. Wisdom tells me I am nothing. Love tells me I am everything. And between the two, my life flows. Nisargadatta Maharaj