fantôme profane;3830385 said:
Let me be clear, I am not claiming that there is proof that the brain is the source of consciousness. I don't like using that word "proof". But I do believe there is definite evidence that points in that direction. As has been pointed out physical changes to the brain have real impacts on personality, temporment, memory, perception etc. Chemicals delivered to the brain can also effect these things, and they can shut down consciousness completely. Is this proof that consciousness is the product of the brain? Not in my opinion, but it is evidence leading in that direction.
Phenomenologically, let's define consciousness as the state of being awake and aware of one’s surroundings and oneself. As the definition implies, consciousness can be divided into two components – arousal or wakefulness and the qualitative state of awareness, which can have many contents – external and internal, and it can be thought of as a continuum of various states, from full conscious wakefulness, to drowsiness, to sleep, and to states which have very little or no awareness, like deep sleep or coma, etc. But of course, i'm talking here in simplified terms.
We know that in order for the cerebral cortex to be in a state of functionality which can cause and maintain various states and contents of awareness – it needs to be constantly activated by some subcortical structures in the brain, the reticular activating system in the brainstem is the most important in this arousal function, and so are a few other structures. Their functioning releases certain neurotransmitters to almost every other part of the cortex, which are then encouraging increased brain activity which is necessary for generating and maintaining the active continuous loop of information processing that we experience as our various states and contents of awareness. This is consciousness itself, in my opinion.
If the brainstem or other brain structures which are necessary for arousal are damaged, then even if the rest of the cortex is untouched, brain activity decreases to a low level of functionality and a state of unconsciousness results. And if you damage certain parts of the cortex you can essentially damage certain parts of your awareness - hemispatial neglect is a good example of that, and there are many other examples. And of course, by altering cortical brain function you can dramatically alter your states and contents of consciousness – you can even turn awareness on and off.
So what we know, among other things, is that the functioning of certain parts of the brain is contributing to consciousness (causing it) and that this contribution is necessary for consciousness, while certain parts of the brain have pretty much nothing to do with consciousness, and in fact you can for example remove the cerebellum at the back of the brain and consciousness will be intact. We also know that one cerebral hemisphere can be conciouss by itself.
All those examples about the effects that manipulations and damages to the brain have on the mind and personality are irrelevant when it comes to consciousness.
All you can prove is thoughts correlate with brains, and somehow you think that just because they correlate, that mean that one is the by-product of the other, and that is faulty reasoning.
This is a straw man. But at the same time it is correct to say that correlational evidence alone is not sufficient to establish a specific
causal relationship (as
cum hoc ergo propter hoc). For that you need experimental evidence.
“However, as neuroscience begins to reveal the mechanisms underlying personality, love, morality, and spirituality, the idea of a ghost in the machine becomes strained. Brain imaging indicates that all of these traits have physical correlates in brain function. Furthermore, pharmacologic influences on these traits, as well as the effects of localized stimulation or damage, demonstrate that the brain processes in question are not mere correlates but are the physical bases of these central aspects of our personhood.”
- Martha J. Farah and Nancy Murphy, Center for Cognitive Neuroscience, Department of Psychology, University of Pennsylvania, Philadelphia, PA/School of Theology, Fuller Theological Seminary, Pasadena, - ‘Neuroscience and the Soul letter’
“If anything, we have a more fine grained ability to intervene and experiment with the brain than with the weather. We cannot change the weather, but we can produce specific mental events by exquisitely precise manipulation of neural structures. The ability to manipulate variables within a system is our most secure source of causal knowledge (cf. Woodward 2003). Thus, our evidence for the neural basis of mental functions is even stronger than our evidence for the physical basis of the weather.”
– ‘No Mental Life after Brain Death: The Argument from the Neural Localization of Mental Functions’: Gualtiero Piccinini and Sonya Bahar, Departments of Philosophy and Psychology/ Department of Physics & Astronomy Center for Neurodynamics
“Optogenetics is hot stuff because it allows researchers to intercede deliberately at any point within the tightly woven networks of the brain, moving from observation to manipulation, from correlation to causation.”
- Christof Koch, Chief Scientific Officer of the Allen Institute for Brain Science in Seattle/ ‘Consciousness: Confessions of a Romantic Reductionist’
“Robert Lawrence Kuhn: Describe for me three different aspects of the brain-mental relationship. One is simple correlation. Second is causation – even though it is correlated there is cause there. And the third is identity – that it is exactly the same thing – that you just have two names for it, like venus being the morning star, two different things – but it's the same thing.
Patrick Haggard: Okey, so that’s a good question, and I'm only going to answer the first two parts, because the third part is a philosophical question, the third part is a question about ‘what do we mean by’ consciousness, what's the semantics. The first two questions are scientific, is it correlation or causation between brain activity and conscious experience? The really important point here is that some of our scientific methods are causational and not correlative. Let's make a distinction between a method like fMRI – brain imaging, where we might ask a participant to lie in a brain scanner and show them some visual stimuli and where we find that we get activation in the visual parts in the brain in the back in the occipital lobe, now that’s just really noticing a correlation between the fact that we showed them some visual stimuli and the fact that these areas of the brain light up. So that’s just showing a correlation between the visual experience that they have and the activity in these parts of the brain. But in some cases we can actually intervene in the brain. So animal experimentation is a very important method of intervening in the brain, but we can't work out much about consciousness in animals because we can't ask them or if we do ask them they are not going to replie right, so there are a few ways in which we can intervene in the human brain, one of them is a very important technique called transcranial magnetic stimulation, so it basically consist of making neurons in the superficial areas of the cortex fire by exposing them to a brief but strong magnetic field. Now in some areas of the brain – not all – you can produce a conscious experience by artificially activating the brain using TMS - transcranial magnetic stimulation. So if you stimulate over the visual cortex you can make people see flashes, and as you move the coil around the different bits of the visual cortex they see a flash in the different parts of their visual field, if you hold the coil over the different bits that process the movement of visual stimuli, they see a flash that wips across their visual field like a lightning bolt – i think that this is a very beautiful demonstration that making neurons fire – in this case artificially – causes conscious experience. I think that’s the evidence for causation.”
- Robert Lawrence Kuhn, Patrick Haggard, Institute of Cognitive Neuroscience & Dept. Psychology/’Closer to Truth - How Brain Scientists Think About Consciousness’
“The mere existence of psychedelics would seem to establish the material basis of mental and spiritual life beyond any doubt—for the introduction of these substances into the brain is the obvious cause of any numinous apocalypse that follows.”
- Sam Harris, philosopher, neuroscientist/‘Drugs and the Meaning off Life’
