In the readings for this week, both McGaugh and LeDoux look at learning and memory mechanisms that are shared with animals (uncovered largely through experiments done on animals) and discuss what about them is adaptive.
One aspect of memory that McGaugh discusses is the fact that long-term memory involves consolidation over a long period of time. He believes that this long period of consolidation is adaptive because it allows the subsequent neurobiological processes to affect how strong a memory is. He points out that this feature of consolidating long-term memory is shared with rats, birds, bees, mollusks and fish and “…clearly emerged early in evolution and was conserved” presumably because it worked well.
Linking emotional response and learning, LeDoux discusses in depth that the fear response makes quick learning possible, and the learning will persist for a long period of time. Just one exposure to a conditioned stimulus-unconditioned stimulus pairing is enough for an animal to show conditioned fear and this association will persist, as evolution has ensured that animals will quickly learn what can threaten their survival and retain the memory in order to be able to draw on this knowledge in future situations. The work of Dolcos et. al. establishes that in fact people do more easily retrieve memories that are more emotional for them. It seems very efficient of the memory system to make it easy for people to retrieve those memories that feel important to the individual and that it may be necessary for him to reflect on.
Implicit memory is another system in the brain that seems to have protective value much like the quick pathway in the fear response system. McGaugh and LeDoux both give examples of how working and implicit memory works even in amnesic patients, like H.M. who are unable to consolidate long-term memories. Le Doux gives the example of the patient whose doctor pricked her with a tack when shaking her hand one day and how the patient, without remembering the incident, refused to shake his hand again. Both LeDoux and McGaugh gives example from the research of Elizabeth Warrington and Lawrence Weiskrantz who showed that amnesic patients who were shown full pictures of objects on three days of testing could subsequenty identify the objects correctly from just fragments of the pictures as well as others. Through their behavior these people all show learning that they don’t explicitly recall. It is interesting that our brains contain basic systems that underlie more complex systems which, when they are unharmed, persist even when higher systems are damaged. It seems highly adaptive that there is a mechanism in place that enables people to learn from experiences in a way that guides future behavior even when they have lost the ability to consciously evaluate those experiences. Even the injured brain is still doing the best it can to help them survive.
These descriptions of implicit memory make me think of the ideas expressed in our readings on the early relationship between a non-verbal infant and caregiver. These early experiences are not something that a child will explicitly remember but she will learn from them nonetheless. And Le Doux makes the point that implicit memories tend to be long-lasting. He also mentions that due to the implicit memory system, people can be cued in such a way that they have an emotional reaction without knowing explicitly why. The amygdala can be set off and create a physical feeling in the body so that you “find yourself in the throes of an emotional state that exists for reasons you do not quite understand.” For these reasons, (and more) early experiences may be very much with a person as she develops and may operate as a very powerful though unfathomable force.
I find the implicit memory system overall to be mysterious and am still mulling over the idea that traces of prior experiences affect our reactions and our behavior without our awareness. I wonder if there are ways to make something that is in the realm of implicit memory known to ourselves explicitly or to change it? Is the implicit memory system as active in people whose memories are intact? I would like to know more about the ways in which different emotions have implicit and explicit components.
Subscribe to:
Post Comments (Atom)
3 comments:
The computer input-output idea of memory has been discounted in recent studies of memory. As we now know, the encoding and retrieval process of memory is much more complicated than previously supposed. As easily as we remember, we can forget or create false memories, in both long-term and short-term memories... the fallibility of memory is an interesting aspect of memory, which can affect everything from law trials to personal life. Remembering is consolidated based on conditions and frequency of recall. Even our most lasting flashbulb memories can often be mis-remembered. What evolutionary reasoning is there for mis-attributing and mis-remembering "lasting" memories (such as the 'lost in the mall' syndrome) and what parts of the brain differ in these types of "memory?" How easily is a memory 'suggested'? What happens in the minds of PTSD patients that make a memory more persistent and how does this show up in brain scans?
I once heard of persistent deja-vu on a BBC study, how does this occur?
I don't know if confabulations alone can be thought of in terms of their evolutionary value. Selective memory and forgetting are useful and false memories are similar to these. In addition there is consciousness. We've seen that conscious explanations for unconscious processes can be far from accurate, so to me it seems confabulations are, by definition, imaginative. The fact that consciousness is a newer ability might explain its fallibility. I too share in Amy's curiosity about the union of the conscious and unconscious - not so much the extent to which they are connected now, but the extent they will be in the far future. Will the amygdala and the hippocampus ever be one?
In the realm of consciousness, I was also wondering about Figure 7-6 (pg 204) in LeDoux: Arousal of the hippocampus and amygdala are shown to result in immediate conscious experience, or working memory. Are these the only two structures involved in the phenomenon? H.M.'s working memory was intact even though he had no hippocampus, and the amygdala operates outside of consciousness...so am I missing something or is this diagram?
I agree with Amy, Naomi, and Matt that distinctions between conscious and unconscious memory seem to fall short when we consider false memories and PTSD.
I think Matt is right, confabulations are imaginative in nature. Does this mean that they are strictly a product of consciousness? Is the ability to formulate an image of things we have never seen, or even to dream, only a quality of consciousness?
Post a Comment