Nosology Core Versus Extended Consciousness

Four hundred years ago, Descartes concluded that consciousness was reserved for human beings. The weight of evidence now suggests at least primitive forms of sentience in creatures besides Homo sapiens. We share an enormous degree of subcortical architecture, paleocortex, aminergic and peptidergic neuromodulatory control systems, and basic affective-motivational systems with a wide variety of mammals. Considering the shared subcortical brain systems that mediate basic motivations and emotions, each with a characteristic feeling tone or subjective valence, how can we not conclude that evidence favors the assumption of phenomenal experience in other mammals, especially primates? Assuming otherwise would mean that these basic behavioral and neural system homologs do not generate an additional homology in terms of a basic sentience. Such a perspective is straightforwardly dualistic and therefore scientifically untenable.

Humans depart from other mammalian lines of evolution principally in terms of extended neocortical and prefrontal system development. These developments give humans vastly enhanced cognitive and conceptual abilities, including language, along with extended capacities for working memory (Baddeley, 1986), planning, and other highly cognitive aspects of executive functions and behavioral organization. The prefrontal and neocortical extensions offer potential cognitive extensions to more primitive executive functions provided by the brain's prototypic affective operating systems and by the basal ganglia.

A number of prominent neuroscience researchers (Damasio, 1999; Panksepp, 1998) have begun to argue that our higher cognitive processes rest on a primary or core form of consciousness. From this point of view, cognition is the latest evolutionary layer on the consciousness onion. This is explicitly different from most cognocentric notions advocating the reverse hypothesis, namely that consciousness depends on higher cognitive processes, including even a proposed dependence on language (Rolls, 1999). The preponderance of evidence favors the notion that these higher cognitive functions rest on foundations provided by the basic affective-homeostatic functions of the brain, as cognitive activity is directed and motivated by those affective systems although it is likely that these cortico-cognitive developments inform and perhaps even in some sense transform the more primitive aspects of core consciousness that we probably share with other mammals.

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