Astrocytes as cellular substrate of memory and consciousness

Contemporary neuroscience regards neuronal networks, and neuronal networks only, as the substrate of memory and consciousness. More than that, current understanding, in essence, denies the existence of special cells or cellular groups which can be the residence of memory, consciousness and other high cognitive functions. At the same time, information processing in the neuronal networks relies entirely on a simple binary code, which might not necessarily offer sophistication sufficient enough to explain how the human brain thinks and becomes

Glial Cells The Brain

Figure 7.15 Diversity of synaptic contacts between neural cells. In the grey matter, synapses may include: (1) classic 'tripartite' neuronal-neuronal contacts, enwrapped by astroglial membranes; (2) neurone-glial synapses (which have already been discovered for neurone-astroglial and neurone-NG2-glial cell contacts); (3) astroglial-neuronal synapses (which are yet to be discovered); and (4) astroglial-astroglial synapses, which may exist as electrical/gap junctional or chemical contacts. In the white matter, astrocytes may act as presynaptic elements in astroglial-oligodendroglial synapses (5); astrocytes and NG2-glia also contact nodes of Ranvier and so could potentially form synapses with axons at nodes of Ranvier. (Modified from Verkhratsky A, Kirchhoff F (2007) NMDA receptors in glia Neuroscientist 13, 1-10)

Figure 7.15 Diversity of synaptic contacts between neural cells. In the grey matter, synapses may include: (1) classic 'tripartite' neuronal-neuronal contacts, enwrapped by astroglial membranes; (2) neurone-glial synapses (which have already been discovered for neurone-astroglial and neurone-NG2-glial cell contacts); (3) astroglial-neuronal synapses (which are yet to be discovered); and (4) astroglial-astroglial synapses, which may exist as electrical/gap junctional or chemical contacts. In the white matter, astrocytes may act as presynaptic elements in astroglial-oligodendroglial synapses (5); astrocytes and NG2-glia also contact nodes of Ranvier and so could potentially form synapses with axons at nodes of Ranvier. (Modified from Verkhratsky A, Kirchhoff F (2007) NMDA receptors in glia Neuroscientist 13, 1-10)

self-aware. In contrast, the astroglial syncytium allows much more diverse routes for informational exchange (as intracellular volume transmission allows passage of many important molecules within the connected astroglial network). Astrocytes divide the space of the grey matter into individual domains, where all neuronal and nonneuronal elements are controlled by a single astroglial cell. By extensive contacts with synaptic membranes belonging to these domains, every astrocyte can integrate all the information flowing though neuronal networks, and is capable of regulating these neuronal networks through the release of neurotransmitters, regulation of the extracellular environment and by affecting neuronal metabolism. The individual microdomains are further integrated through intercellular contacts, which multiply the processing capabilities. As a result, it is entirely possible (and conceptually simpler) to conceive how astrocytes may provide the substrate for memory and cognition, whereas neurones are specialized to serve as the transducers of information between different brain regions and between the brain and the rest of the body. Will such an 'astrocentric' theory stand the scrutiny of experimental testing? This has to be seen in the future.

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