Consciousness is seen as a difficult “binding” problem. Binding, a process where different sensations evoked by an item are associated in the nervous system, can be viewed as a process similar to associative learning. Several reports that consciousness is associated with some form of memory imply that different forms of memories have a common feature contributing to consciousness. Based on a proposed synaptic mechanism capable of explaining different forms of memory, we developed a framework for consciousness. It is based on (...) the formation of semblance of sensory stimulus from 1)synaptic semblances when excitatory postsynaptic potentials arrive at functionally LINKed postsynaptic membranes, and 2) network semblances when these potentials summate to elicit action potential initiating activity in a network of neurons. It is then possible to derive a framework for consciousness as a multi-dimensional semblance. According to this framework, a continuum of semblances formed from background sensory stimuli and oscillating neuronal activities serve to maintain consciousness. Feasibility of this framework to explain various physiological and pathological states of consciousness, its subjective nature and qualia is examined. (shrink)

Consciousness is seen as a difficult “binding” problem. Binding, a process where different sensations evoked by an item are associated in the nervous system, can be viewed as a process similar to associative learning. Several reports that consciousness is associated with some form of memory imply that different forms of memories have a common feature contributing to consciousness. Based on a proposed synaptic mechanism capable of explaining different forms of memory, we developed a framework for consciousness. It is based on (...) the formation of semblance of sensory stimulus from (1) synaptic semblances when excitatory postsynaptic potentials arrive at functionally LINKed postsynaptic membranes, and (2) network semblances when these potentials summate to elicit action potential initiating activity in a network of neurons. It is then possible to derive a framework for consciousness as a multi-dimensional semblance. According to this framework, a continuum of semblances formed from background sensory stimuli and oscillating neuronal activities serve to maintain consciousness. Feasibility of this framework to explain various physiological and pathological states of consciousness, its subjective nature and qualia is examined. (shrink)

This paper explores the changes in cognitive function which occur as someone "loses consciousness" under anesthesia. Seven volunteers attempted a categorization task and a within-list recognition test while inhaling air, 0.2% isoflurane, and 0.4% isoflurane. In general, performance on these tests declined as the dose of anesthetic was increased and returned to baseline after 10 min of breathing air. A measure of auditory evoked responding termed "coherent frequency" showed parallel changes. At 0.2% isoflurane, subjects could still identify and respond to (...) category exemplars but showed impaired short-term memory function. Electrical stimulation at 0.4% isoflurane, intended to mimic the arousing effects of surgery, had a small, beneficial effect on performance. A mean of 63% of category exemplars was identified at this stage, but recognition memory for those exemplars was at chance on recovery. There was no evidence for learning of words presented at 0.8% isoflurane. (shrink)

A theory of anaesthesia is presented. It consists of four hypotheses: (1) The occurrence of states of consciousness causally depends on the formation of transient higher-order, self-referential mental representations. The occurrence of such states is identical with the appearance of conscious phenomena. Loss of consciousness will occur, if and only if the brain's representational activity falls below a critical threshold. (2) Mental representations are instantiated by neural cell assemblies. (3) The formation of assemblies involves the activation of the NMDA receptor (...) channel complex. The activation state of this receptor determines the rate at which assemblies are generated. (4) General anaesthetics have a common operative mechanism: they directly or indirectly affect the function of the NMDA system. (shrink)

feelings (brainstem, limbic system). The best scientific synchrony and consciousness.21,27 Anesthesiology, V 105, No 2, Aug 2006.