The two papers cited above were used in a discussion of consciousness as an area of ongoing research in the Senior Seminar in Neural and Behavioral Sciences at Bryn Mawr and Haverford Colleges during spring semester, 1999. The following are comments on the article by participants in that seminar.
I think it is promising that there may be a measure for consciousness. if high-frequency oscillatory electrical activity can really be used as a measure of consciousness, then much more could be learned about consciousness. It is interesting that this electrical activity is looked at in both humans and cats. That would be inferring that cats are also conscious. If cats are conscious, what other animals are consious?
As for the article on hemianopic anosognosia, i admit i found it a little confusing. however, i admit that i may have just too tired to read it clearly enough to understand it. i thought that the question they raised about how we know taht we are missing information was a very interesting one. i just didn't understand how they answered it. i personally think that HAN could be explained by the way that we don't perceive our blind spots. Our brain is simply filling in the missing information enough that the person wouldn't really notice until the blind spot became so large taht that couldn't miss it.
I am particularly interested in their evidence that hemianopsia can be transient. If some of the patients experienced this only transiently, it would suggest that some sort of regulation was happening within the brain to bring unconscious events into conscious processing, a sort of re-wiring of the conscious circuitry. The study points to the cause of transiency as the doctor explaining the deficit and the patient understanding the explanation and accepting it. I think a more interesting interpretation of this is that the patient, once made conscious of the deficit, may be able to use conscious thought to regulate subconscious functioning or awareness. This would suggest that conscious functioning is able to regulate input and perhaps compensate for defects.
The article on hemianopic anosognosia was difficult to understand because I wasn't familiar with the medical terminology at all, but I think they had some very interesting conclusions. Basically they looked at people who had partially lost their vision and were not aware of it. Thus the researchers tried to locate possible regions responsible for conscious visual perception by examining which regions in the brain were disfunctional in these patients. Their results suggested that loss of visual consciousness could be attributed to lesions, or nerve loss, in various different regions of the brain and that "visual awareness requires integration of information distributed in relatively large cortical regions".
In the anesthesia article, the definition they use for unconsciousness is different from what I've been considering it to be. Their definition is specific for their purposes as anesthesiologists. They need physical measures of detecting whether a person is unconscious, so they measure autonomic responses, analgesia, amnesia, etc. However, I think there is more to consciousness that maybe they can't measure. For example, there is no way of measuring whether the person is thinking or not. They propose the 30-40 Hz method of detecting whether the person is unconscious. However, this method is based on observations that people who exhibit spontaneous movements or movements in response to a verbal command always show 30-40 Hz oscillations. Thus, it is only correlating motor responses to these oscillations, but we know that there is more to consciousness than motor response. I believe that a person who has lost all motor capabilities may still be conscious.
As we read more and more about consciousness, I am growing more convinced that there may be no way to measure and study consciousness. It may be impossible to objectively measure and study qualia, which by definition is a subjective "inner feeling".
The articel Does Anethesia Cause Loss of Consciousness addressed a point Professor Grobsteion brought up the last time we met, namely, can you know that somebody is conscious if they are incapable of movement? Professor Grobstein argued that one could not know a person was conscious unless tat person could give a sign of his or her consciousness. This is the same problem doctors seem to face when putting people on anethesia for an operation. I was astonished to read that consciousness could be inferred from auditory evoked responses. This way of measuring consciousness seems a bit too simple alomst. Afterall, auditory evoked reponses indicate only that an auditory stimulus has been received, it should not reveal that consciousness is present. That the author cited evidence from cats surprised me as much as Erin Hunter. As long as it is not established that animals are conscious, even though I do not doubt this, evidence derived from measuring their outputs should not be used to 'prove' consciousness is present. Generally, I believe the article was very telling about the state of consciousness research. We simply do not know what consciousness is and what we must be lookig for in order to find out. I agree with Noreen Khan when she says she doubts we will understand consciousness soon - the evidnece we have encountered till now is not convincing.
The second article, on hemianopic anosognosia, was very difficult to understand. At first I was confused over the medical terminology, but after reading it through twice, I understood it better (not well...just better). The idea of the experiment was extremely interesting to me. The idea that one could just not be aware of a body defect is definitely something to look into. A good method for approaching this discussion is the exmination of the deficit of the visual field. From what I understood, they were trying to locate areas in the brain to identify as causes for the unawareness of the deficit. Also agreeing with Erin Hunter, I think HAN could be explained swomewhat by the fact that our brains normally compensate for gaps/blindspots in our visual fields. However, this article did make a step into examining the idea of visual consciousness, or consciousness derived from visual stimuli, which I think is a good area to look into.
This article has proven how badly we need to determine what is consciousness is and how to define it (or what unconsciousness is and how to define it). It is obvious from the reports of patients after being anesthetized that loss of consciousness is not defined by a loss of movement, nor a lack of response to a strong stimulus. The second criterion has bothered me for some time. The reason it has disturbed me is because the ability of strong stimuli (such as running a serrated wheel over, or pinching of the skin) to elicit a response is also used as a measure of consciousness in patients who may be comatose or otherwise brain injured or unresponsive. I often wondered whether the patient actually feels the stimulus but is in a locked in state. As horrifying as it may be to be presumed unconscious while actually being aware, imagine being in that condition for a year as a result of an injury. I havenít heard of such reports, but the thought none the less is a scary one.
In any case, another criterion for determining lack of consciousness that is interesting yet not quite as disturbing is the lack of recall. I wonder how lack of recall can be used to say someone was unconscious. Perhaps the person was conscious but does not remember being so. Sound silly? Perhaps, but when I canít recall for the life of me what happened three days ago at breakfast, does that mean I wasnít conscious? Or, what about people who block out, and are therefore unable to recall, horrifying and/or traumatic past experiences? There is no recall here. Does this mean the person was not conscious or aware? There is a pharmacological explanation for how benzodiazepines block recall, but this is still interesting to think about. Especially if one is tempted to use recall to determine awareness/consciousness in an unanesthesized person. Further, if someoneís short-term memory system is damaged, is that person unaware and unconscious, even though they are living each moment for the moment? I believe there is a documented story of just such a case, I donít however remember this person being referred to as unaware, unconscious, or unable to experience. Perhaps Alzheimerís disease provides another example.
The article on anesthesia and consciousness is also a fascinating work because it is an attempt at understanding what brain functions or measurable activities could be recognized to represent consciousness. The idea of anesthesia in itself is interesting and how the combinations of certain drugs produce different kinds of anesthestetic, such as anterograde amnesia but the ability to have interactions with patients while in surgery. We might ask if the person is conscious at all if afterward they do not remember what happened. Would this be one of the zombie states that we discussed previously?
I am interested in seeing what other kinds of measurements might be able to develop in order to detect consciousness and therefore make anesthesia a more effective tool during surgery. However, I think this is a very difficult process because there are so many measurements of activity that we can read from the brain while not knowing what, if any, significance they have as well as whether this is a measurement of consciousness or other types of activity in the brain.
I found article by Kulli and Kock to be very interesting because it addressed the question that has been brought many times during our discussion. It seems that the definition that an anesthesologist uses as being unconscious is based on the aspect of movement. I found the idea of recall to be very interesting too. I wondered whether the patients who were quoted in the beginning of the article were actually did have consciousness during the procedure or they just had distorted memories due to the anesthetic which made them think that they woke up during the procedure. It seemed that this article focused a lot on movement and unconsciousness. If you think about the people who woke up during the surgeries, they were conscious of the operation, but they couldn't move or say anything about it. I think that doctors need to rework their definitions of unconsciousness during operations and incoporate the work on neuronal oscillations and STM into this problem. It was interesting to read about the patients who were read a list of words and recalled them after recovery. This helps support a theory of cognition that states that priming doesn't take place at the memory level, but at the perceptual level because amnesics show the same behavior by not remembering they saw the words, but recalling them when they were presented with a task.
The theme of "all or none" was also shown if both of these papers for consciousness. Both papers asserted that you cannot either conscious or unconscious. Kulli and Kock stated that the recall of an anesthesized patient is usually incomplete or distorted, but it is not all or none. Critchley in the other paper asserted that hemianopic anosognosias varied along a spectrum of total absence of awareness to relative degrees of awareness for their deficits. I found this to be an interesting theme related to conscious that should be considered when trying to define or describe consciousness.
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