Gerald M.Edelmann
A UNIVERSE OF CONSCIOUSNESS
Basic 2000
Nonrepresentational Memory
pg. 93
Memory is a central component of the brain mechanisms that lead to consciousness.
It is commonly assumed tbat memory involves the inscription and storage of information, but what is stored? Is it a coded message? When it is "read out" or recovered, is it unchanged? These questions point to the widespread assumption that what is stored is some kind of representation. This chapter takes the opposite viewpoint, consistent with a selectionist approach, that memory is nonrepresentational.
We see memory as the ability of a dynamic system that is molded by selection and exbibits degeneracy to repeat or suppress a mental or physical act. This novel view of memory is illustrated with a geological comparison; memory is more like the melting and refreezing of a glacier than it is like an inscription on a rock.
cf. Freeman : Origins of Music: brain functions - solipsistic brain - dynamics of perception
pg 94
....The problem the brain confronts is that signals from the world do not generally represent a coded input. Instead, they are potentially ambiguous, are context-dependent, and are not necessarily adorned by prior judgments of their significance.
...a memory is not a representation; it is a reflection of how the brain has changed its dynamics in a way that allows the repetition of a performance.
...in mentioning a changing context, we pay heed to a key property of memory in the brain: that it is, in some sense, a form of constructive recategorization during ongoing experience, rather than a precise replication of a previous sequence of events.
pg. 102
Perception into Memory:
The Remembered Present
To uncover the neural mechanisms of consciousness, it is useful to keep in mind the distinction between primary consciousness and higher-order consciousness.
Primary consciousness is seen in animals with certain brain structures similar to ours. These animals appear to be able to construct a mental scene but have limited semantic or symbolic capabilities and no true language.
Higher-order consciousness (which flourishes in humans and presupposes the coexistence of primary consciousness) is accompanied by a sense of self and the ability in the waking state explicitly to construct past and future scenes. It requires, at the minimum, a semantic capability and, in its most developed form, a linguistic capability.
In this chapter, we present a model that accounts for the appearance of primary consciousness in the course of evolution that is consistent with a selectionist view of the brain. We briefly consider the neural requirements to be incorporated in such a model.
The first requirement is perceptual categorization, the ability to carve up the world of signals into categories adaptive for a given animal species.
The second requirement is the development of concepts. We propose that concepts arise from the mapping by the brain itself of the activity of the brain's own areas and regions.
....categorical memory responsive to value and the activity of reentryTwo more requirements for conscious experience are the appearance of a categorical memory responsive to value and the activity of reentry, which is the fundamental inte-grative mechanism in higher brains.
.....remembered present
We propose that primary consciousness emerged in evolution when, through the appearance of new circuits mediating reentry, posterior areas of the brain that are involved in perceptual categorization were dynamically linked to anterior areas that are responsible for a value-based memory.With such means in place, an animal would be able to build a remembered present - a scene tbat adaptively links immediate or imagined contingencies to that animal's previous history of value-driven behavior.
pg 103
The greatest challenge to modern neuroscience is to provide an adequate analysis of the brain mechanisms that give rise to consciousness. In this chapter, we consider a proposal for the neural mechanisms of consciousness that is based on the selectional brain theory. To understand the neural processes that underlie consciousness, one must first understand a number of other brain processes at a variety of organizational levels. These processes include
perceptual categorization;
concepts;
value;
memory; and, at the neural level, special dynamic processes of cortico-thalamic organization.
pg 105
THE CRITICAL ROLE OF REENTRY
...reentry, is the third main tenet of the TNGS. As we previously discussed, reentry is a process of ongoing parallel and recursive signaling between separate brain maps along massively parallel anatomical connections, most of which are reciprocal. It alters and is altered by the activity of the target areas it interconnects. Reentry is not only the most important integrative mechanism in higher brains, but is conceptually the most challenging of the principles proposed in the TNGS. It is critical to a variety of processes, ranging from perceptual categorization and motor coordination to consciousness itself.
pg 125
Consciousness and Complexity .
Consciousness is extraordinarily differentiated. At any given time, we experience a particular conscious state selected out of billions of possible states, each of which can lead to different behavioral conseques. The occurrence of a particular conscious state is therefore highly informative in the specific sense that information is the reduction of uncertainty among a number of alternatives. If this is the case, the neural processes underlying conscious experience must also be highly differentiated and informative. In this chapter, we examine how the information content of a neural process can actually be evaluated. To do so, it is crurial to take the point of view of the neural ystem itsef and of its constitutive subsets of elements. As we show, the information content of such a ystem can be expressed by a statistical measure tbat we call "neural complexity". This measure of complexity provides an estimate of the degree to which a unified neural process is differentiated. A major task of this chapter is to show that consciousness and complexity are intimately linked and to illustrate how complexity is realized in the brain. The analysis not only resolves a number of vexing problems, it adds something new to our ideas of how a scientific observer should examine a conscious system.
pg 138
The Dynamic Core Hypothesis
In this chapter, we first reviev observations indicating that despite their wide distribution, only a subset of the neuronal groups in our brain comtributes directly to conscious experience at any given time. What, then, if anything, is special about these neuronal groups, and how should they be identified both in theory and experiment?
The dynamic core hypothesis is our answer to this question. This hypothesis states that the activity of a group of neurons can contribute directly to conscious experience if it is part of a functional cluster, characterized by strong mutual interactions among a set of neuronal groups over a period of hundreds of milliseconds.
To sustain conscious experience, it is essential that this functional cluster be highly differentiated, as indicated by high values of complexity. Such a cluster, which we call the "dynamic core" because of its ever-changing composition yet ongoing integration, is generated largely, althongh not exclusively, within the thalamocortical system.
The dynamic core hypothesis leads to sperific predictions concerning the neural basis of conscious experience. Unlike hypotbeses that merely invoke a correlation between conscious experience and this or that neural structure or group of neurons, the dynamic core hypothesis accounts instead for the general properties of conscious experience by linking these properties to the specific neural processes that can give rise to them.
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