Arnold B. Scheibel - How Brain Scientists Think About Consciousness

arne when we think about human consciousness the specialness that we all feel about being human in reality it gets back to our brain we have to talk about the brain how could this three-pound matter piece of matter think and feel it seems incomprehensible robert i guess that's the most pressing question that any of us any of us can answer and obviously we we don't know let me take a whole brain just use it as a kind of more as a thought weight than anything else we do know that action is based on input and output action to be appropriate needs an evaluation and the sensory input gives us the raw materials for that evaluation and the output then presumably allows us to produce the activity on the environment which is most useful for the organism at that particular point in time it's it's a bromide to say that the cerebral hemispheres developed to this extent in order to make cognitive activity thoughtful meaningful decisions possible so this brain we're now looking at the top now how would you put this like that this were in my head how would that right if this were in your head your forehead would be here so i would be down you'd be this way okay fired here eyes and nose beneath in back this would be the back of your head and of course your neck would be down here your spinal cord would be coming up out of the brain stem so in in in its situation this is this is what you'd have this could be me and this this could be you a matter of fact this is this brain is in uh remarkably good shape uh uh very little atrophy it's uh just a beautiful specimen of this this remarkable except it doesn't have a body it lost it a lot along the way yeah uh and i you you asked basic question how do we think how do we feel and we don't have the foggiest notion i can tell you this as a beginning there are two basic kinds of information that come into the brain one is the information about how much what where when the qualia the components of the individual experience the other part the other informational component is not the quantity and not the quality but the intensity of the experience there are actually two parallel systems one and i'm going to go to the half brain for this okay one we're looking at the inside we're looking at the inside now of the hemisphere here's the brain stem that's been cut in half right on midline right in the middle information is streaming up the specific informations that we've been talking about streaming up through the brain stem through what we call fiber bundles or tracts entering eventually after many relays entering the cortex then there is a second system that occupies the central core of this so-called brain stem and this central core carries not specificities about the information but some very general signatures of the information how much how frequently is it occurring and very importantly what significance does it have to me we call this central core the reticular formation which means it has a spattered appearance in the histological uh preparation that's unimportant at this point but these two have to work together because it's one thing to have specific information it's another thing to know how urgent it is information is flowing in all the time so we have to establish some priorities and it is the second system this reticular or core system that helps us establish priorities to give you an example if there's a stimulus in this room we're aware of it if that stimulus goes on regularly the reticular core quickly realizes that this is not a threat to us it simply begins to disregard it and the emphasis that that sensory information gets in the cortex the emphasis begins to go down and if it continues long enough we'll disregard it entirely so the reticular system in a sense monitors our attention and what we focus on absolutely and many people and i happen to be one of them feel that one of the basic foundations of what we call the conscious experience consciousness lies in this reticular core of the brain stem and its modulation of entire brain that is say of cortical activity so we have to we have to continuously think of these two systems working together one the qualia the the the quantum components of the experience and the other different sensations exactly the other the impact the frequency and the uh what's your importance the importance very good term the importance of that information and the cortex then is going to deal with that and that of course is one of the great unsolved problems how do we deal with that we we know that the cortex becomes the repository not only of the immediate momentary experience but is and has been the repository of the experiences we've built up over a lifetime something we call memory how is memory developed well we know enough now to realize that information laden memories names places dates correlations are probably initially laid down in a deep set area here on the most inner and under surface of this part of the brain we call that the hippocampal dentate complex we don't yet know how it happens but we know that it apparently generates a very specific pattern of what we call synaptic or junctional activities these in turn work on the dna systems we produce no new protein and actual structural changes occur that are somehow transferred widely through the cortex that's what we call the laying down of memory the other side of that of course is retrieval we have to be able to retrieve those at the appropriate time and both of these are profound mysteries now there have been a few patients who have had serious damage to their hippocampus on each side in some cases epilepsy or different things sometimes they've had to be taken out for epilepsy what happens when those tiny areas of the brain are damaged rather remarkably so i'm very glad you picked that up when we have bilateral that is to say two-sided damage yes those patients lose the capacity to lay down new memories so we can i can remember what i did as a child or what happened any time prior to that exactly but it's impossible to have new memories that's right so that every time they wake up in the morning it's a brand new experience it's like groundhog day the movie absolutely but it's not funny you know it's uh and of course there are some very well-known patients who have suffered this kind of disability and they are among the most studied patients in all of neuroscience it's a an example a sad example but a very informative one of when injury can really reveal what natural function is and this is one of the prime ways in which we have learned about the function of brains particularly of the human brain where there are of course ethical constraints which limit what we can do experimentally what about emotion emotion is a different seems to have a different characteristic than cognitive thinking yeah we know certain things and there's so much that we don't know for instance we know that the experiences that make up emotion seem to be generated in a part of the brain that lies here on the inner surface we say the medial surface and along this great central ark we call this the limbic system the limbic system includes cortex and it includes several deep-seated nuclei one of which is known as the amygdala which means almond the little almond the amygdala is located under here very close actually to the hippocampus and the amygdala is it's one of my favorite structures uh if you ask me to define its role in one sentence i would say the amygdala establishes the emotional valence of an experience what do i mean by that the amygdala decides if something that happens to you is potentially dangerous or perhaps pleasant and one of the best examples that's been quoted many times is you're walking through a tropical rain forest with the corner of your eye you see something coiled under a tree you recoil and then look at it it's an old coil of rope so obviously something warned us off until we had further cortical activity to evaluate what happens this quick and dirty response is strictly part of the amygdala's job another example the amygdala in action we now know helps us read the face of what we call a khan specific you and i are looking at each other we're reading each other's face and we're drawing certain conclusions about does he hate me or does he feeling friendly talk the amygdala is doing that continuously and we find that in the animal kingdom too where for instance in the animal kingdom there'll be an alpha male or an alpha female and the others live subserviently to her you never challenge an alpha male by looking him directly in the eye this is confrontational and the amygdala picks that up immediately works through a system that's close the so-called hypothalamus and sends fight signals and so the alpha male immediately takes on against you in human in the human world visual confrontation has developed a somewhat different kneeling meaning but uh again this is the limbic lobe with the amygdala working to generate on a moment-to-moment basis emotional context the experiencing of the emotion the pleasure or the rapidly beating heart and the rapidly increased respiration they are taken care of by the little structure that the limbic system and the amygdala feed into we call that the hypothalamus and the hypothalamus directly controls these expressions of emotion that you have hormones to hormones and through direct neuronal connections and between these these structures that we've just mentioned we have an emotionally i'm going to say emotionally valid and emotionally valid reacting individual and i say valid because there are syndromes there are diseases where there's interruption of this system and then the individual either is unable to express emotion or cannot control the flares of emotion we know for instance that electrical storms in the amygdala can produce murderous sociopathic acting out types of activity well that creates some serious challenges to the nature of free will and responsibility and legal liabilities very much so and it's impossible at this point to draw a defective line because uh at what point does the individual cease having responsibility if his amygdala has a storm yeah so we basically see several kinds of systems we have the sensory inputs the specifics we have the association areas of cognitive associations cognitive planning for the future in the frontal lobes and then this fascinating limbic system which adds emotional context to everything that that comes together and and makes us humans as what we are yes and as you put it that way the only thing that i have to add is the fact the component that integrates the feeling tone of an individual with the cognitive highest level personality components are a set of almost anti-intuitive you might say unlikely connections between the pre-frontal or executive cortex and this system here is where we make our decisions to think about the future here is the where we feel about these things we put them together and we have a lot of feeling about becoming something in the in the world in a sense this this is our signature and each one of us is unique robert that's that's for me that's the most remarkable part