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- Daniel Collerton & Elaine Perry (2007). Do Multiple Cortical-Subcortical Interactions Support Different Aspects of Consciousness? Behavioral and Brain Sciences 30 (1):88-89.Merker's core idea, that the experience of being conscious reflects the interactions of actions, targets, and motivations in the upper brainstem, with cortex providing the content of the conscious experience, merits serious consideration. However, we have two areas of concern: first, that his definition of consciousness is so broad that it is difficult to find any organisms with a brain that could be non-conscious; second, that the focus on one cortical–subcortical system neglects other systems (e.g., basal forebrain and brainstem cholinergic systems and their cortical and thalamic target areas) which may be of at least equal significance. (Published Online May 1 2007).
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Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the ‘dynamic core’). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized (...)
Merker makes a strong case for the upper brain stem as being the neural home of primary or phenomenal consciousness. Though less emphasized, he makes an equally strong and empirically supported argument for the critical role of the mesodiencephalon in basic emotion processes. His evidence and argument on the functions of brainstem systems in primary consciousness and basic emotion processes present a strong challenge to prevailing assumptions about the primacy of cognition in emotion-cognition-behavior relations. (Published Online May 1 2007).
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To further illuminate the nature of conscious states, it may be progressive to integrate Merker's important contribution with what is known regarding (a) the temporal relation between conscious states and activation of the mesodiencephalic system; (b) the nature of the information (e.g., perceptual vs. premotor) involved in conscious integration; and (c) the neural correlates of olfactory consciousness. (Published Online May 1 2007).
My response addresses general commentary themes such as my neglect of the forebrain contribution to human consciousness, the bearing of blindsight on consciousness theory, the definition of wakefulness, the significance of emotion and pain perception for consciousness theory, and concerns regarding remnant cortex in children with hydranencephaly. Further specific topics, such as phenomenal and phylogenetic aspects of mesodiencephalic-thalamocortical relations, are also discussed. (Published Online May 1 2007).
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