Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Degeneracy, Redundancy, Fault Tolerance

 

No one neuron is essential and critical for the operation and functioning of the neural network.

Degeneracy, Stochasticity, Robustness

The pattern of synaptic strengths in the ensemble of cortical and subcortical neurons has the property of degeneracy as pointed out by Edelman.

Countless examples of degeneracy in the brain. The complex meshwork of connections in the thalamocortical system assures that a large number of different neuronal groups can similarly affect the output. A consequence of degeneracy is that certain localized neurological lesions may often appear to have little effect. (Edelman; Universe of Consciousness, 87)

Structurally variable but functionally equivalent networks, are an example of degeneracy, defined as the capacity of systems to perform similar functions despite differences in the way they are configured and connected. (Sporns; Networks of the Brain, 68)

An input signal pattern will distribute itself in the cortical network with variability in the ensemble of pathways it invokes, each time it appears as an input.  Many thousands of synapses in the active pattern are likely to be on the verge of connectivity, "twinkling" in-and-out of connectivity, while most of the synapses in the pattern are firmly in the active-connected state.  The stochastic properties of neuron functionality and its dendritic tree of about 10,000 synapses will require that populations dynamics determine network functionality rather than the stochastic properties of individual neurons and small neuronal assemblies.

The degeneracy characteristic of the network provides robustness in network functionality, not depending on the stochastic characteristics of individual neurons, but rather population dynamics of large ensembles. Individual neurons can die or otherwise become nonfunctional, leaving the network patterns of memories largely intact.

One neuron or group of neurons can be part of many networks, and thus many representations of memory, perception, or action. (Fuster; Prefrontal Cortex, 379)

 

Grandmother Cells

No individual cells function as “grandmother cells.”

If they did exist, reactivated grandmother cells would allow the playback of the same perceived contents in their entirety. The hypothesis of a grandmother cell is not borne out in the reality of neurophysiological findings. (Damasio; Self Comes to Mind, 138)

 

 

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