Researches that have been carried out in the years that have passed concerning the subject of human memory have been in most cases separated in to two main categories. The first category in which these researches have been put is cognitive organization of memory and the other category is brain basis of memory. Following this separation that has been there in the researches, the memory’s cognitive theories have generally undergone evolution separately from the memory’s neuroscientific theories and the reverse has also been the case.
This paper has considered the idea that electrical activity measures of the brain of a human being can be utilized as a great means for carrying out the study of the human memory. There has been explanation of the links between the memory functions and electrophysiological measures. The paper has also looked at the possibilities for future initiatives to be taken on the basis of carrying out measurement of the electrical activity of the human brain.
It has been established that the initiatives taken to have clear understanding of cognition are supposed to be eventually rooted in conception that is precise of neural substrates of cognition. Taking moves to have the understanding of human memory is a very big challenge and this calls for the full power of brain science as well as cognitive science.
Introduction
Researches that have been carried out in the years that have passed concerning the subject of human memory have been in most cases separated in to two main categories. The first category in which these researches have been put is cognitive organization of memory and the other category is brain basis of memory. Following this separation that has been there in the researches, the memory’s cognitive theories has, in general terms, undergone evolution separately from the memory’s neuroscientific theories and the reverse has also been the case. More so, those people who have come up with cognitive theories have discovered, on a constant basis, that neural evidence is irrelevant to their theories. In considering the neuroscientists, these are mainly focused on getting to understand the way the brain operates, and the works they have involved themselves in have not connected with the attempts to getting to understand the way the mind operates.
However, fresh links between the science of the brain and the cognitive science can be clearly seen in a broad variety of fields. Moves carried out to measure the function of the human brain, for instance, have brought up the level of the possibility that relevant information concerning the way the brain works can be utilized to find out the way the mind works. According to Gabriel (1998), there is currently a growing pattern to utilize neural information to inform theories of memory in the human memory research. In adopting this approach, this calls for appreciating memory’s brain substrates as well as the cognitive organization of memory. This approach aims at building up links between theories embedded at these varied levels.
This paper is going to consider the idea that electrical activity measures of the brain of a human being can be utilized as a great means for carrying out the study of the human memory. There is going to be explanation of the links that exist between the memory functions and electrophysiological measures. The paper is also going to look at the possibilities for future initiatives to be taken on the basis of carrying out measurement of the electrical activity of the human brain.
“Neural Implementation of declarative memory”
The disorders that come about as a consequence of the brain damage (mental disorders) mostly give clear illustrations of the associations that exist between the mind and the brain. The studies carried out on those patients having amnesia (neuropsychological studies) have been of great significance in regard to tracing out the relationship between the brain and memory. This significance is a consequence of the amnesic shortfall and can be greatly selective. This shortfall is discriminatory or selective when it comes about jointly with an immense set of cognitive functions that are preserved and among these functions; the memory functions are also encompassed. In line with this, evidence obtained from amnesia has been made use of to a great level to set up hypotheses concerning the basic structure of memory. Basing on the idea given out by Squire (1987), declarative memory in particular has been given definition to in behavioral terms as that type of memory that is needed for recalling and making recognition of facts as well as events and also as the memory that is used in feeling the conscious recollection under such conditions or circumstances. Sufficient neuropsychological evidence backs the categorization of declarative memory as being different from the rest of the memory types. However, the clear nature of declarative memory still stands to be explained.
According to Paller (2001), “ key empirical support for distinguishing between declarative and nondeclarative memory consists of a set of dissociations, wherein amnesic patients demonstrate poor memory but not when tested using various implicit memory tests, which are memory tests that make no reference to prior learning episodes” (Pg 3). Therefore, there can be distinguishing of the two categories of memory phenomenon. The first category is conscious recollection and this is “when a person brings to mind some prior event or some factual knowledge, with the awareness of retrieving memory” (Paller, 2001, pg 3). The other class or category is perpetual priming and this is “when behavior is changed in certain circumstances pertaining to a specific perpetual event, as the result of prior experience, and not necessary experience of recollection” (Paller, 2001, pg 3).
Examples of understood memory tests that are employed in illustrating preserved perceptual priming in amnesia is the “word-identification test” put forth by scientists such as Cermak et al (1985), Hamann et al (1995) and Paller et al (1991). Paller (2001) points out that:
According to Paller (2001), in the “word-identification test”, individuals make an effort to read words that are presented in a tainted way. There can be examination of perceptual priming at a time identification is higher for those words that also were shown in a study stage that came before the word identification test. Even if amnesia patients portray ordinary priming in this test, they show reduced performance at a time when they are asked to engage in making recognition of whether or not there was presentation of those words previously.
According to the formulations that have been put forth by Mayes and Downes (1997, pg 97) “the neural dysfunction in amnesic patients disrupts declarative memory but leaves other types of memories entirely intact”. The actual cause for the declarative memory possessing this position remains to be a question of constant research. However, the main overview is that at a time memory breaks down in amnesia, recollection is in part interfered with but there is still preservation of particular kinds of priming. By putting priming and recollection side by side, there can be learning about the way these two are different from one another in terms of psychological and neural features they have. For instance, the brain potentials that move along the time-course of recollection and priming may offer a chance to carry out monitoring of those cognitive processes that are relevant and engage in studying their neutral substrates. Such kind of research may eventually support efforts carried out to give description to unknowable border that exists in neural terms between conscious mental events and unconscious ones.
According to Squire and Paller (2000), “fundamental speculation about declarative memory is that requisite information storage takes place within neocortical areas dedicated for processing particular information in question. There is no storing of all memories in cortical regions in unitary memory store in the brain” (pg 428). But rather, the storage of facial memories is carried out in cortical regions where there is representation of facial information and where there is representation of verbal information among others.
On the overall basis, the storage space for memory in the cortex goes along functional specialty in the cortex. However, “the memory dysfunction of amnesia cuts across all sensory modalities, while at the same time it does not disrupt perceptual abilities” (Paller, 2001, pg 5). The impairment of amnesia is overall in a way that it includes memories that are based on all kinds of information. However, it is also crucial since this impairment is constrained to declarative memory. In fact some of the scientists who have been carrying out studies in the field of memory disorder like Squire and Paller (2000) observe that the core problem, in general terms, lies in the storage of declarative memories and not in encoding or retrieving these memories.
According to Hebb (1949), “declarative memories characteristically depend on multiple neuronal ensembles that represent different high-level perceptual, cognitive, and emotional attributes processed in functionally distinct cortical regions”. Feeling an event in the moment at hand can be attained at a time such a set of distributed neural ensembles undergoes stimulation under the “prefrontal networks control” (Paller, 1997). More so, according to Paller (1997), this set of neuronal ensembles can turn out to be for the short term linked through cortico-thalamic and cortico-hippocampal networks. This connections function that is for the meantime are eventually substituted by fresh neocortical representations, instantiated by “coherence ensembles” traced in sequential lobe region next to hippocampus. Paller (2001) points out that the core function of the newly formed neuronal ensembles is to offer consistency to the disseminated neocortical demonstration. “Enduring declarative memories are, by this account, characteristically composed of a set of distributed neocortical ensembles plus associated coherence ensembles” (Pg 6).
Paller (2001) points out that “consolidation basically involves the repeated activation of this set of neocortical storage sites, and in this manner mediating memory retrieval, relationships with other memories, and the formation for other enduring declarative memory” (Pg 7). This chain of events that consists consolidation can go on whether the person has intentions to memorize or carry out the rehearsal of the memory or not, like in the course of sleep.
Paller (2001) gives tentative neurobiological definitions to declarative memory and priming. He defines declarative memory as “a type of neocortical memory in which the relevant plasticity occurs across many neocortical zones, and storage requires a special consolidation process that is unique to this type of dispersed neocortical memory” (pg 7). More so, Paller (2001), defines priming as “a type of neocortical memory in which the relevant plasticity occurs within a single neocortical zone”.
Even if there have been researches on priming most of the time by employing single items like words, on some occasion there has been utilization of pairs of items as an alternative. In cases like these, priming may depend on plasticity across multiple neocortical zones and not just within zone plasticity. Basing on this conceptualization that has been outlined here, this calls for consolidation.
Paller (2001) observes that the dissociation between recollection and priming in amnesia can now be recast in neurobiological terms; “recollection is impaired due to consolidation failure following disruption of either cortico-thalamic or cortico-hippocampal networks, whereas priming due to plasticity within single neocortical zones is preserved” (pg 7). In an effort to bring together the biological and the psychological aspects of amnesia, this conceptualization shows out the starting of a neurocognitive theory of declarative memory as well as priming in those people that are healthy. Considering the quick expansion of the neuroscience in the years that have passed, basing on this there can be optimism about this theory being developed even more, specified in clear detail on an increasing level, and be subjected to empirical test. However, a move that will be more crucial is to carry out the discovery of neural measures of the applicable memory functions in humans.
Electrophysiological measures of recollection and perceptual priming
Paller (2001) points out that the studies of old-new electrophysiological differences originally brought about divergent hypotheses in regard to the associations between electrophysiological (ERPs) and memory retrieval, while studies that followed attained success in carrying out the isolation of ERP associates of recollective processing. Basing on the fact that recollection as well as priming seem to come about at a time those items that are studied are presented in a memory test, straight old-new EPR analyses are characteristically unclear in regard to carrying out the isolation of ERPs related to a single type of memory or the other. Those demonstrations that have been successful show a relationship of recollection needed;
- Giving a record of ERPs in the course of recognition and also in circumstances in which subjects were not supposed to carry out explicit recognition responses;
- Carrying out the comparison of the study conditions that influenced declarative memory and priming on a different basis and
- Encompassing behavioral measures to ensure confirmation of the memory dissociation.
According to Paller ( 2001), the notion that observations can be carried out about the neural actions that are in charge of conscious recollection is of great significance for the reason that observations like these are supposed to prove to be of help for carrying out testing of theories concerning neurophysiology of memory. More so, this move can possibly ensure enhancement of the understanding of the cognitive structure as well as the neural substrates of memory
Perceptual priming is seen to come about even at a time a person can not make out a difference in a clear manner between old items and the new ones, and this notion has been having some links with the notion of unconscious memory. There exist a large number of speculations in regard to unconscious memory. These speculations range from the explorations carried out by Freud to the present concerns with restrained memories. However, the direct measurements of the unconscious memory are not common and they bring in much controversy. According to what Desimone (1996) observes; “there has also been showing of the possible electrophysiological correlates of priming in recordings from single neutrons in monkey visual cortex. Some neurons in ventral areas, in particular, tend to show reduced responses during stimulus repetitions” (Desimone, 1996, pg 13497). Wiggs and Martin (1998) point out that neuroimaging in human beings as well indicate that priming may come about as a result of reduced neural activity that follows perceptual learning which may be the core of well-organized perceptual processing. The measures of the events of the brain that bring about recollection and priming offer fresh footing for theoretical initiatives concerning the crucial differences that exist between memories that are accessible to consciousness and those that are not accessible and in general terms, dissimilarities between those events that are conscious and those that are unconscious.
Conclusion
The studies that have been carried out in the field of neuropsychology have given an indication about which brain region are vital for various memory functions. However, taking a step further to establish a comprehensive understanding of how the implementation of these functions are carried out in the brain, and of their clear cognitive structure, will call for a joint working among several approaches. This will involve both healthy individuals and those whose brain has been damaged. The significance of electrophysiological as well as functional neuroimaging techniques, in this line, call for experimental designs that ensure capitalizing on the spatial and temporal decision offered by each of the techniques. The studies that have to be undertaken are not supposed to just consider the strengths and weaknesses of each method or technique for carrying out the measurement of the function of the brain but there is supposed to be there knowledge that the success in the use of these methods and techniques is reliant on whether or not the cognitive activities of the individuals can be sufficiently and effectively controlled.
Studies that involve human memory neural bases have the prospect for carrying out the expansion of the insights acquired from preceding cognitive studies as well as neuropsychological studies of memory. Differences between priming and recollection have especially brought in launching of immense theoretical development. As Paller (2001) points out “even if more work will be needed to sufficiently test and build up these ideas, a reasonable working hypothesis is that there can be characterization of priming and recollection as different kinds of neocortical memory that rely on neurophysological mechanisms that are distinct” (Pg 13). Priming tends to rely on separate occurrences of neocortical plasticity in a way that processing that follows in at least one of cortical regions is changed. On the contrary, “recollection is supposed to have the development of connections among sets of neocortical areas in the service of bringing about an “enduring declarative memory”” (Paller, 2001, pg 13). The confirmation that has been established about ERPs being used to carry out checking of the processes that are related to recollection and also the processes related to priming give a suggestion that this advance will be of great use in carrying out the development of hypotheses are of great help in this field of study.
Eventually, such attempts to acquire the knowledge about the “neural human memory bases” will make things clear not just in line with the kind of the memory processes arrangement in the brain but about individual understanding of conscious recollection as well. Nevertheless, having the knowledge about the neural implementation of the functions of the memory and also having knowledge about the cognitive structure of memory is supposed to be preferably not seen as two goals that are separate. These are basically two sections of the same undertaking. Initiatives that are taken in getting to understand neural performance incline towards the precision of assumptions about cognitive structure. As it has been established, the initiatives taken to acquire clear knowledge about cognition are supposed to be eventually rooted in conception that is correct of “neural substrates of cognition”. Taking moves to have the understanding of human memory is a very big challenge and this calls for the full power of brain science as well as cognitive science.
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